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Molecular Cancer Therapeutics

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Molecular Cancer Therapeutics

Malignant melanoma is associated with poor clinical prognosis; however, novel molecular and immune therapies are now improving patient outcomes. Almost 50% of melanomas harbor targetable activating mutations of BRAF that promote RAS–RAF–MEK–ERK pathway activation and melanoma proliferation. Recent evidence also indicates that melanomas bearing mutant BRAF may also have altered immune responses, suggesting additional avenues for treatment of this patient group. The small molecule inhibitors selective for mutant BRAF induce significant but short-lived clinical responses in a proportion of patients, but also lead to immune stimulatory bystander events, which then subside with the emergence of resistance to inhibition. Simultaneous BRAF and MEK inhibition, and especially combination of BRAF inhibitors with new immunotherapies such as checkpoint blockade antibodies, may further enhance immune activation, or counteract immunosuppressive signals. Preclinical evaluation and ongoing clinical trials should provide novel insights into the role of immunity in the therapy of BRAF-mutant melanoma. Mol Cancer Ther; 13(12); 2769–83. ©2014 AACR.

With an increasing number of clinical trials looking at combination therapies in cancer, potential drug–drug interactions require particular attention. One such instance is the treatment of CD30+ tumors after previous vorinostat (SAHA; suberoylanilide hydroxyamic acid) failure with the anti-CD30 antibody–drug conjugate brentuximab vedotin. Using B-, T-, and natural killer (NK)–cell lines in vitro, we demonstrate that SAHA downregulates the expression of CD30 and lowers the efficacy of subsequent brentuximab vedotin treatment if baseline CD30 levels are reduced by 50% or more. Interestingly, low-dose SAHA treatment that maintained 50% or more of basal CD30 expression followed by subsequent treatment with brentuximab vedotin led to enhanced antitumor activity. The downregulation of CD30 was short lived upon SAHA removal, suggesting that allowing SAHA washout may circumvent any interactions with subsequent drug therapies. Our findings confirm the requirement of CD30 for brentuximab vedotin efficacy and suggest that combination treatment with SAHA in CD30dim tumors may decrease efficacy. Combination treatment in highly CD30+ tumors, however, increases efficacy and warrants further consideration as a new treatment paradigm. Mol Cancer Ther; 13(12); 2784–92. ©2014 AACR.

Emergence of clinical resistance to BRAF inhibitors, alone or in combination with MEK inhibitors, limits clinical responses in melanoma. Inhibiting HSP90 offers an approach to simultaneously interfere with multiple resistance mechanisms. Using the HSP90 inhibitor AT13387, which is currently in clinical trials, we investigated the potential of HSP90 inhibition to overcome or delay the emergence of resistance to these kinase inhibitors in melanoma models. In vitro, treating vemurafenib-sensitive cells (A375 or SK-MEL-28) with a combination of AT13387 and vemurafenib prevented colony growth under conditions in which vemurafenib treatment alone generated resistant colonies. In vivo, when AT13387 was combined with vemurafenib in a SK-MEL-28, vemurafenib-sensitive model, no regrowth of tumors was observed over 5 months, although 2 of 7 tumors in the vemurafenib monotherapy group relapsed in this time. Together, these data suggest that the combination of these agents can delay the emergence of resistance. Cell lines with acquired vemurafenib resistance, derived from these models (A375R and SK-MEL-28R) were also sensitive to HSP90 inhibitor treatment; key clients were depleted, apoptosis was induced, and growth in 3D culture was inhibited. Similar effects were observed in cell lines with acquired resistance to both BRAF and MEK inhibitors (SK-MEL-28RR, WM164RR, and 1205LuRR). These data suggest that treatment with an HSP90 inhibitor, such as AT13387, is a potential approach for combating resistance to BRAF and MEK inhibition in melanoma. Moreover, frontline combination of these agents with an HSP90 inhibitor could delay the emergence of resistance, providing a strong rationale for clinical investigation of such combinations in BRAF-mutated melanoma. Mol Cancer Ther; 13(12); 2793–804. ©2014 AACR.

Inhibition of the monocarboxylate transporter MCT1 by AZD3965 results in an increase in glycolysis in human tumor cell lines and xenografts. This is indicated by changes in the levels of specific glycolytic metabolites and in changes in glycolytic enzyme kinetics. These drug-induced metabolic changes translate into an inhibition of tumor growth in vivo. Thus, we combined AZD3965 with fractionated radiation to treat small cell lung cancer (SCLC) xenografts and showed that the combination provided a significantly greater therapeutic effect than the use of either modality alone. These results strongly support the notion of combining MCT1 inhibition with radiotherapy in the treatment of SCLC and other solid tumors. Mol Cancer Ther; 13(12); 2805–16. ©2014 AACR.

Proliferating cell nuclear antigen (PCNA) plays an essential role in DNA replication and repair. Tumor cells express high levels of PCNA, identifying it as a potentially ideal target for cancer therapy. Previously, we identified nine compounds termed PCNA inhibitors (PCNA-Is) that bind directly to PCNA, stabilize PCNA trimer structure, reduce chromatin-associated PCNA, and selectively inhibit tumor cell growth. Of these compounds, PCNA-I1 is most potent. The purposes of this study were to further investigate the effects of targeting PCNA chromatin association on DNA damage and cytotoxicity and to evaluate the therapeutic potential of PCNA-I1 against tumors in mice. Given the important roles of tumor suppressor p53 in regulating sensitivity of tumor cells to chemotherapeutics, we performed studies in two human prostate cancer cell lines differing in p53 expression: LNCaP cells (wild-type p53) and PC-3 cells (p53-null). PCNA-I1 induced DNA damage and apoptosis in both LNCaP and PC-3 cells and enhanced DNA damage and apoptosis triggered by cisplatin. PCNA-I1 also induced autophagy in PC-3 cells. A short-term pretreatment with PCNA-I1 reduced colony formation by 50% in both cell lines. These data suggest that, unlike many other cytotoxic drugs, the effects of PCNA-I1 on tumor cells do not depend on expression of p53. Intravenous administrations of PCNA-I1 significantly retarded growth of LNCaP tumors of in nude mice without causing detectable effects on mouse body weight and hematology profiles. These data provide proof of concept that targeting PCNA chromatin association could be a novel and effective therapeutic approach for treatment of cancer. Mol Cancer Ther; 13(12); 2817–26. ©2014 AACR.

Insulin-like growth factor (IGF) signaling is associated with castrate-resistant prostate cancer (CRPC) progression. Insulin receptor substrates 1 and 2 (IRS1/2) mediate mitogenic and antiapoptotic signaling from IGF1 receptor (IGF1R), insulin receptor, and other oncoproteins. This study demonstrates that IRS1/2 expression is increased in prostate cancer, and persists in CRPC. Furthermore, this study assesses the anticancer activity of NT157, a small molecule tyrphostin targeting IRS proteins, using androgen-responsive (LNCaP) and -independent (PC3) prostate cancer cells in vitro and in vivo. NT157 treatment resulted in dose-dependent inhibition of IGF1R activation, suppression of IRS protein expression, inhibition of IGF1-induced AKT activation, but increased ERK activation in NT157-treated cells in vitro. These effects were correlated with decreased proliferation and increasing apoptosis of LNCaP cells and increasing G2–M arrest in PC3 cells. NT157 also suppressed androgen-responsive growth, delayed CRPC progression of LNCaP xenografts, and suppressed PC3 tumor growth alone and in combination with docetaxel. This study reports the first preclinical proof-of-principle data that this novel small molecule tyrosine kinase inhibitor suppresses IRS1/2 expression, delays CRPC progression, and suppresses growth of CRPC tumors in vitro and in vivo. Demonstration that IRS expression can be increased in response to a variety of stressors that may lead to resistance or reduced effect of the therapies indicate that NT157-mediated IRS1/2 downregulation is a novel therapeutic approach for management of advanced prostate cancer. Mol Cancer Ther; 13(12); 2827–39. ©2014 AACR.

Resistant KIT mutations have hindered the development of KIT kinase inhibitors for treatment of patients with systemic mastocytosis. The goal of this research was to characterize the synergistic effects of a novel combination therapy involving inhibition of KIT and calcineurin phosphatase, a nuclear factor of activated T cells (NFAT) regulator, using a panel of KIT-mutant mast cell lines. The effects of monotherapy or combination therapy on the cellular viability/survival of KIT-mutant mast cells were evaluated. In addition, NFAT-dependent transcriptional activity was monitored in a representative cell line to evaluate the mechanisms responsible for the efficacy of combination therapy. Finally, shRNA was used to stably knockdown calcineurin expression to confirm the role of calcineurin in the observed synergy. The combination of a KIT inhibitor and a calcineurin phosphatase inhibitor (CNPI) synergized to reduce cell viability and induce apoptosis in six distinct KIT-mutant mast cell lines. Both KIT inhibitors and CNPIs were found to decrease NFAT-dependent transcriptional activity. NFAT-specific inhibitors induced similar synergistic apoptosis induction as CNPIs when combined with a KIT inhibitor. Notably, NFAT was constitutively active in each KIT-mutant cell line tested. Knockdown of calcineurin subunit PPP3R1 sensitized cells to KIT inhibition and increased NFAT phosphorylation and cytoplasmic localization. Constitutive activation of NFAT appears to represent a novel and targetable characteristic of KIT-mutant mast cell disease. Our studies suggest that combining KIT inhibition with NFAT inhibition might represent a new treatment strategy for mast cell disease. Mol Cancer Ther; 13(12); 2840–51. ©2014 AACR.

Beta-glucuronidase (βG) is a potential biomarker for cancer diagnosis and prodrug therapy. The ability to image βG activity in patients would assist in personalized glucuronide prodrug cancer therapy. However, whole-body imaging of βG activity for medical usage is not yet available. Here, we developed a radioactive βG activity–based trapping probe for positron emission tomography (PET). We generated a 124I-tyramine–conjugated difluoromethylphenol beta-glucuronide probe (TrapG) to form 124I-TrapG that could be selectively activated by βG for subsequent attachment of 124I-tyramine to nucleophilic moieties near βG-expressing sites. We estimated the specificity of a fluorescent FITC-TrapG, the cytotoxicity of tyramine-TrapG, and the serum half-life of 124I-TrapG. βG targeting of 124I-TrapG in vivo was examined by micro-PET. The biodistribution of 131I-TrapG was investigated in different organs. Finally, we imaged the endogenous βG activity and assessed its correlation with therapeutic efficacy of 9-aminocamptothecin glucuronide (9ACG) prodrug in native tumors. FITC-TrapG showed specific trapping at βG-expressing CT26 (CT26/mβG) cells but not in CT26 cells. The native TrapG probe possessed low cytotoxicity. 124I-TrapG preferentially accumulated in CT26/mβG but not CT26 cells. Meanwhile, micro-PET and whole-body autoradiography results demonstrated that 124I-TrapG signals in CT26/mβG tumors were 141.4-fold greater than in CT26 tumors. Importantly, Colo205 xenografts in nude mice that express elevated endogenous βG can be monitored by using infrared glucuronide trapping probes (NIR-TrapG) and suppressed by 9ACG prodrug treatment. 124I-TrapG exhibited low cytotoxicity allowing long-term monitoring of βG activity in vivo to aid in the optimization of prodrug targeted therapy. Mol Cancer Ther; 13(12); 2852–63. ©2014 AACR.

In an effort to improve the therapeutic index of cancer chemotherapy, we developed an advanced nanopreparation based on the combination of landscape phage display to obtain new targeting ligands with micellar nanoparticles for tumor targeting of water-insoluble neoplastic agents. With paclitaxel as a drug, this self-assembled nanopreparation composed of MCF-7–specific phage protein and polyethylene glycol–phosphatidylethanolamine (PEG-PE) micelles showed selective toxicity to target cancer cells rather than nontarget, non cancer cells in vitro. In vivo, the targeted phage micelles triggered a dramatic tumor reduction and extensive necrosis as a result of improved tumor delivery of paclitaxel. The enhanced anticancer effect was also verified by an enhanced apoptosis and reduced tumor cell proliferation following the treatment with the targeted micellar paclitaxel both in vitro and in vivo. The absence of hepatotoxicity and pathologic changes in tissue sections of vital organs, together with maintenance of overall health of mice following the treatment, further support its translational potential as an effective and safe chemotherapy for improved breast cancer treatment. Mol Cancer Ther; 13(12); 2864–75. ©2014 AACR.

Despite being among the most common oncogenes in human cancer, to date, there are no effective clinical options for inhibiting KRAS activity. We investigated whether systemically delivered KRAS siRNAs have therapeutic potential in KRAS-mutated cancer models. We identified KRAS siRNA sequences with notable potency in knocking down KRAS expression. Using lung and colon adenocarcinoma cell lines, we assessed antiproliferative effects of KRAS silencing in vitro. For in vivo experiments, we used a nanoliposomal delivery platform, DOPC, for systemic delivery of siRNAs. Various lung and colon cancer models were used to determine efficacy of systemic KRAS siRNA based on tumor growth, development of metastasis, and downstream signaling. KRAS siRNA sequences induced >90% knockdown of KRAS expression, significantly reducing viability in mutant cell lines. In the lung cancer model, KRAS siRNA treatment demonstrated significant reductions in primary tumor growth and distant metastatic disease, while the addition of CDDP was not additive. Significant reductions in Ki-67 indices were seen in all treatment groups, whereas significant increases in caspase-3 activity were only seen in the CDDP treatment groups. In the colon cancer model, KRAS siRNA reduced tumor KRAS and pERK expression. KRAS siRNAs significantly reduced HCP1 subcutaneous tumor growth, as well as outgrowth of liver metastases. Our studies demonstrate a proof-of-concept approach to therapeutic KRAS targeting using nanoparticle delivery of siRNA. This study highlights the potential translational impact of therapeutic RNA interference, which may have broad applications in oncology, especially for traditional "undruggable" targets. Mol Cancer Ther; 13(12); 2876–85. ©2014 AACR.

Interactions between the HDAC6 inhibitor ricolinostat (ACY1215) and the irreversible proteasome inhibitor carfilzomib were examined in non-Hodgkin lymphoma (NHL) models, including diffuse large B-cell lymphoma (DLBCL), mantle cell lymphoma (MCL), and double-hit lymphoma cells. Marked in vitro synergism was observed in multiple cell types associated with activation of cellular stress pathways (e.g., JNK1/2, ERK1/2, and p38) accompanied by increases in DNA damage (H2A.X), G2–M arrest, and the pronounced induction of mitochondrial injury and apoptosis. Combination treatment with carfilzomib and ricolinostat increased reactive oxygen species (ROS), whereas the antioxidant TBAP attenuated DNA damage, JNK activation, and cell death. Similar interactions occurred in bortezomib-resistant and double-hit DLBCL, MCL, and primary DLBCL cells, but not in normal CD34+ cells. However, ricolinostat did not potentiate inhibition of chymotryptic activity by carfilzomib. shRNA knockdown of JNK1 (but not MEK1/2), or pharmacologic inhibition of p38, significantly reduced carfilzomib–ricolinostat lethality, indicating a functional contribution of these stress pathways to apoptosis. Combined exposure to carfilzomib and ricolinostat also markedly downregulated the cargo-loading protein HR23B. Moreover, HR23B knockdown significantly increased carfilzomib- and ricolinostat-mediated lethality, suggesting a role for this event in cell death. Finally, combined in vivo treatment with carfilzomib and ricolinostat was well tolerated and significantly suppressed tumor growth and increased survival in an MCL xenograft model. Collectively, these findings indicate that carfilzomib and ricolinostat interact synergistically in NHL cells through multiple stress-related mechanisms, and suggest that this strategy warrants further consideration in NHL. Mol Cancer Ther; 13(12); 2886–97. ©2014 AACR.

Cathepsin K (CatK) is essential for osteoclast-mediated bone resorption. CatK expression is also detected in breast cancer cells that metastasize to bone. Here, the CatK inhibitor L-235 dosed in prevention (10, 30, and 100 mg/kg, p.o., b.i.d.) or treatment regimen (30 mg/kg) was compared with the bisphosphonate zoledronic acid (ZOL, 7.5 μg/kg/wk, s.c.) in the intratibial injection model of MDA-MB-231 breast carcinoma in nude rats. Progression of osteolysis, skeletal tumor burden, and local metastasis was evaluated by radiography through 42 days and ex vivo μCT and histology. IHC and RT-PCR confirmed the increases in CatK protein and mRNA levels in human breast cancer primary and metastatic tumors. In the experimental model of breast cancer bone metastasis, L-235 dosed in preventive mode resulted in a dose-related reduction of osteolysis of 72%, 75%, and 87% respectively, compared with ZOL by 86% versus intact. Similarly, L-235 significantly reduced intratibial tumor volume by 29%, 40%, and 63%, respectively, compared with 56% by ZOL versus vehicle. Efficacy of L-235 and ZOL on reduction of osteolytic lesions and tumor burden was comparable in treatment versus preventive regimens. All L-235 doses inhibited cortical disruption and extraskeletal tumor growth to a level comparable with ZOL. Assessment of local metastasis demonstrated that treatment with the CatK inhibitor was more effective than ZOL in reducing breast cancer invasion. These data support the role of CatK in breast cancer skeletal growth and metastasis and CatK inhibitors may represent a novel oral therapy for treatment of metastatic breast cancer. Mol Cancer Ther; 13(12); 2898–909. ©2014 AACR.

Alectinib/CH5424802 is a known inhibitor of anaplastic lymphoma kinase (ALK) and is being evaluated in clinical trials for the treatment of ALK fusion–positive non–small cell lung cancer (NSCLC). Recently, some RET and ROS1 fusion genes have been implicated as driver oncogenes in NSCLC and have become molecular targets for antitumor agents. This study aims to explore additional target indications of alectinib by testing its ability to inhibit the activity of kinases other than ALK. We newly verified that alectinib inhibited RET kinase activity and the growth of RET fusion–positive cells by suppressing RET phosphorylation. In contrast, alectinib hardly inhibited ROS1 kinase activity unlike other ALK/ROS1 inhibitors such as crizotinib and LDK378. It also showed antitumor activity in mouse models of tumors driven by the RET fusion. In addition, alectinib showed kinase inhibitory activity against RET gatekeeper mutations (RET V804L and V804M) and blocked cell growth driven by the KIF5B-RET V804L and V804M. Our results suggest that alectinib is effective against RET fusion–positive tumors. Thus, alectinib might be a therapeutic option for patients with RET fusion–positive NSCLC. Mol Cancer Ther; 13(12); 2910–8. ©2014 AACR.

This report describes results from our analysis of the activity and biodistribution of a novel pan-ERBB inhibitor, NT113, when used in treating mice with intracranial glioblastoma (GBM) xenografts. Approaches used in this investigation include: bioluminescence imaging (BLI) for monitoring intracranial tumor growth and response to therapy; determination of survival benefit from treatment; analysis of tumor IHC reactivity for indication of treatment effect on proliferation and apoptotic response; Western blot analysis for determination of effects of treatment on ERBB and ERBB signaling mediator activation; and high-performance liquid chromatography for determination of NT113 concentration in tissue extracts from animals receiving oral administration of inhibitor. Our results show that NT113 is active against GBM xenografts in which wild-type EGFR or EGFRvIII is highly expressed. In experiments including lapatinib and/or erlotinib, NT113 treatment was associated with the most substantial improvement in survival, as well as the most substantial tumor growth inhibition, as indicated by BLI and IHC results. Western blot analysis results indicated that NT113 has inhibitory activity, both in vivo and in vitro, on ERBB family member phosphorylation, as well as on the phosphorylation of downstream signaling mediator Akt. Results from the analysis of animal tissues revealed significantly higher NT113 normal brain-to-plasma and intracranial tumor-to-plasma ratios for NT113, relative to erlotinib, indicating superior NT113 partitioning to intracranial tissue compartments. These data provide a strong rationale for the clinical investigation of NT113, a novel ERBB inhibitor, in treating patients with GBM. Mol Cancer Ther; 13(12); 2919–29. ©2014 AACR.

Ashwagandha is an important herb used in the Indian system of traditional home medicine, Ayurveda. Alcoholic extract (i-Extract) from its leaves and its component, withanone, were previously shown to possess anticancer activity. In the present study, we developed a combination of withanone and withaferin A, major withanolides in the i-Extract, that retained the selective cancer cell killing activity and found that it also has significant antimigratory, -invasive, and -angiogenic activities, in both in vitro and in vivo assays. Using bioinformatics and biochemical approaches, we demonstrate that these phytochemicals caused downregulation of migration-promoting proteins hnRNP-K, VEGF, and metalloproteases and hence are candidate natural drugs for metastatic cancer therapy. Mol Cancer Ther; 13(12); 2930–40. ©2014 AACR.

Marine-derived compounds have been explored and considered as possible antitumor agents. In this study, we analyzed extracts of the sponge Cribrochalina vasculum for their ability to inhibit tumor cell proliferation. Screening identified two acetylenic compounds of similar structure that showed strong tumor-specific toxicity in non–small cell lung carcinoma (NSCLC) cells and small-cell lung carcinoma cells, and less prominent toxicity in ovarian carcinoma, while having no effect on normal cells. These acetylenic compounds were found to cause a time-dependent increase in activation of apoptotic signaling involving cleavage of caspase-9, caspase-3, and PARP, as well as apoptotic cell morphology in NSCLC cells, but not in normal fibroblasts. Further analysis demonstrated that these compounds caused conformational change in Bak and Bax, and resulted in loss of mitochondrial potential and cytochrome c release in NSCLC cells. Moreover, a decreased phosphorylation of the growth factor signaling kinases Akt, mTOR, and ERK was evident and an increased phosphorylation of JNK was observed. Thus, these acetylenic compounds hold potential as novel therapeutic agents that should be further explored for NSCLC and other tumor malignancies. Mol Cancer Ther; 13(12); 2941–54. ©2014 AACR.

High-grade glioma is one of the most aggressive cancers in adult humans and long-term survival rates are very low as standard treatments for glioma remain largely unsuccessful. Cannabinoids have been shown to specifically inhibit glioma growth as well as neutralize oncogenic processes such as angiogenesis. In an attempt to improve treatment outcome, we have investigated the effect of 9-tetrahydrocannabinol (THC) and cannabidiol (CBD) both alone and in combination with radiotherapy in a number of glioma cell lines (T98G, U87MG, and GL261). Cannabinoids were used in two forms, pure (P) and as a botanical drug substance (BDS). Results demonstrated a duration- and dose-dependent reduction in cell viability with each cannabinoid and suggested that THC-BDS was more efficacious than THC-P, whereas, conversely, CBD-P was more efficacious than CBD-BDS. Median effect analysis revealed all combinations to be hyperadditive [T98G 48-hour combination index (CI) at FU50, 0.77–1.09]. Similarly, pretreating cells with THC-P and CBD-P together for 4 hours before irradiation increased their radiosensitivity when compared with pretreating with either of the cannabinoids individually. The increase in radiosensitivity was associated with an increase in markers of autophagy and apoptosis. These in vitro results were recapitulated in an orthotopic murine model for glioma, which showed dramatic reductions in tumor volumes when both cannabinoids were used with irradiation (day 21: 5.5 ± 2.2 mm3 vs. 48.7 ± 24.9 mm3 in the control group; P < 0.01). Taken together, our data highlight the possibility that these cannabinoids can prime glioma cells to respond better to ionizing radiation, and suggest a potential clinical benefit for glioma patients by using these two treatment modalities. Mol Cancer Ther; 13(12); 2955–67. ©2014 AACR.

Normal tissue toxicity markedly reduces the therapeutic index of genotoxic anticancer agents, including ionizing radiation. Countermeasures against tissue damage caused by radiation are limited by their potential to also protect malignant cells and tissues. Here, we tested a panel of signal transduction modifiers for selective radioprotection of normal but not tumor tissues. These included three inhibitors of GSK3 (LiCl, SB216763, and SB415286) and two inhibitors of NF-B (ethyl pyruvate and RTA 408). Among these, the thiol-reactive triterpenoid RTA 408 emerged as a robust and effective protector of multiple organ systems (gastrointestinal, skin, and hemopoietic) against lethal doses of radiation. RTA 408 preserved survival and proliferation of intestinal crypt cells in lethally irradiated mice while reducing apoptosis incidence in crypts and villi. In contrast, RTA 408 uniformly inhibited growth of established CWR22Rv1, LNCaP/C4-2B, PC3, and DU145 xenografts either alone or combined with radiation. Antitumor effects in vivo were associated with reduced proliferation and intratumoral apoptosis and with inhibition of NF-B–dependent transcription in PC3 cells. Selective protection of normal tissue compartments by RTA 408 critically depended on tissue context and could not be replicated in vitro. Collectively, these data highlight the potential of RTA 408 as a cytoprotective agent that may be safely used in chemoradiation approaches. Mol Cancer Ther; 13(12); 2968–77. ©2014 AACR.

Tivantinib (ARQ197) was first reported as a highly selective inhibitor of c-MET and is currently being investigated in a phase III clinical trial. However, as recently reported by us and another group, tivantinib showed cytotoxic activity independent of cellular c-MET status and also disrupted microtubule dynamics. To investigate if tivantinib exerts its cytotoxic activity by disrupting microtubules, we quantified polymerized tubulin in cells and xenograft tumors after tivantinib treatment. Consistent with our previous report, tivantinib reduced tubulin polymerization in cells and in mouse xenograft tumors in vivo. To determine if tivantinib directly binds to tubulin, we performed an in vitro competition assay. Tivantinib competitively inhibited colchicine but not vincristine or vinblastine binding to purified tubulin. These results imply that tivantinib directly binds to the colchicine binding site of tubulin. To predict the binding mode of tivantinib with tubulin, we performed computer simulation of the docking pose of tivantinib with tubulin using GOLD docking program. Computer simulation predicts tivantinib fitted into the colchicine binding pocket of tubulin without steric hindrance. Furthermore, tivantinib showed similar IC50 values against parental and multidrug-resistant cells. In contrast, other microtubule-targeting drugs, such as vincristine, paclitaxel, and colchicine, could not suppress the growth of cells overexpressing ABC transporters. Moreover, the expression level of ABC transporters did not correlate with the apoptosis-inducing ability of tivantinib different from other microtubule inhibitor. These results suggest that tivantinib can overcome ABC transporter–mediated multidrug-resistant tumor cells and is potentially useful against various tumors. Mol Cancer Ther; 13(12); 2978–90. ©2014 AACR.

In this article, we describe a novel antibody–drug conjugate (ADC; SGN–LIV1A), targeting the zinc transporter LIV-1 (SLC39A6) for the treatment of metastatic breast cancer. LIV-1 was previously known to be expressed by estrogen receptor–positive breast cancers. In this study, we show that LIV-1 expression is maintained after hormonal therapy in primary and metastatic sites and is also upregulated in triple-negative breast cancers. In addition to breast cancer, other indications showing LIV-1 expression include melanoma, prostate, ovarian, and uterine cancer. SGN–LIV1A consists of a humanized antibody conjugated through a proteolytically cleavable linker to monomethyl auristatin E, a potent microtubule-disrupting agent. When bound to surface-expressed LIV-1 on immortalized cell lines, this ADC is internalized and traffics to the lysozome. SGN–LIV1A displays specific in vitro cytotoxic activity against LIV-1–expressing cancer cells. In vitro results are recapitulated in vivo where antitumor activity is demonstrated in tumor models of breast and cervical cancer lineages. These results support the clinical evaluation of SGN–LIV1A as a novel therapeutic agent for patients with LIV-1–expressing cancer. Mol Cancer Ther; 13(12); 2991–3000. ©2014 AACR.

Granulin–epithelin precursor (GEP) overexpression has been shown in many cancers with functional role on growth, and recently on regulating chemoresistance and cancer stem cell (CSC) properties. Here, we investigate the combined effect of GEP antibody and chemotherapeutic agent. Combination therapy was compared with monotherapy using hepatocellular carcinoma (HCC) cells in vitro and orthotopic liver tumor models in vivo. CD133 and related hepatic CSC marker expressions were investigated by flow cytometry. Antiproliferative and apoptotic effects and signaling mechanisms were examined by immunohistochemistry, flow cytometry, and Western blot analysis. Secretory GEP levels in the serum and culture supernatant samples were measured by ELISA. We demonstrated that HCC cells that survived under chemotherapeutic agents showed upregulation of hepatic CSC markers CD133/GEP/ABCB5, and enhanced colony and spheroid formation abilities. Importantly, GEP antibody sensitized HCC cells to the apoptosis induced by chemotherapy for both HCC cell lines and the chemoresistant subpopulations, and counteracted the chemotherapy-induced GEP/ABCB5 expressions and Akt/Bcl-2 signaling. In human HCC orthotopic xenograft models, GEP antibody treatment alone was consistently capable of inhibiting the tumor growth. Notably, combination of GEP antibody with high dose of cisplatin resulted in the eradication of all established intrahepatic tumor in three weeks. This preclinical study demonstrated that GEP antibody sensitized HCC cells to apoptosis induced by chemotherapeutic agents. Combination treatment with GEP antibody and chemotherapeutic agent has the potential to be an effective therapeutic regimen for GEP-expressing cancers. Mol Cancer Ther; 13(12); 3001–12. ©2014 AACR.

Chromosome region maintenance 1 (CRM1) mediates the nuclear export of proteins and mRNAs, and is overexpressed in various cancers. Recent studies have also reported that CRM1 protein expression is a negative prognostic factor in patients with cancer. Therefore, CRM1 is considered a potential target for anticancer therapy. Our previous study demonstrated that CBS9106, a synthetic small-molecular inhibitor of CRM1, decreases CRM1 protein through proteasomal degradation without affecting CRM1 mRNA levels. However, the mechanism by which CRM1 is degraded is not well understood. Here, we demonstrate a novel signaling pathway that plays an important role in CBS9106-induced CRM1 degradation. We found that MLN4924, a selective inhibitor of NEDD8-activating enzyme (NAE), effectively inhibits cullin neddylation and attenuates CBS9106-induced CRM1 degradation in a time- and dose-dependent manner. MLN4924 also attenuated CBS9106-induced nuclear accumulation of Ran-binding protein 1 (RanBP1), cell growth inhibition, and apoptosis. Furthermore, RNAi-mediated knockdown of neddylation pathway proteins (NEDD8 and UBA3) or cullin ring ligase (CRL) component protein (Rbx1) attenuated CRM1 protein degradation and G1 phase cell-cycle arrest by CBS9106. Knockdown of CSN5 or CAND1 also partially inhibited CBS9106-induced CRM1 degradation. These findings demonstrate that CBS9106-induced CRM1 degradation is conferred by CRL activity involving the neddylation pathway, and that this response to CBS9106 leads to cell growth inhibition and apoptosis. Mol Cancer Ther; 13(12); 3013–23. ©2014 AACR.

The success of immunotherapeutic approaches targeting glioblastoma multiforme (GBM) demands a robust antiglioma T-cell cytotoxic and memory response. Recent evidence suggests that rapamycin regulates T-cell differentiation. Herein, we tested whether administration of rapamycin could enhance the efficacy of immunotherapy utilizing Fms-like tyrosine kinase 3 ligand (Ad-Flt3L) and thymidine kinase/ganciclovir (Ad-TK/GCV). Using the refractory rat RG2 glioma model, we demonstrate that administration of rapamycin with Ad-Flt3L + Ad-TK/GCV immunotherapy enhanced the cytotoxic activity of antitumor CD8+ T cells. Rats treated with rapamycin + Ad-Flt3L + Ad-TK/GCV exhibited massive reduction in the tumor volume and extended survival. Rapamycin administration also prolonged the survival of Ad-Flt3L + Ad-TK/GCV–treated GL26 tumor–bearing mice, associated with an increase in the frequency of tumor-specific and IFN+ CD8+ T cells. More importantly, rapamycin administration, even for a short interval, elicited a potent long-lasting central memory CD8+ T-cell response. The enhanced memory response translated to an increased frequency of tumor-specific CD8+ T cells within the tumor and IFN release, providing the mice with long-term survival advantage in response to tumor rechallenge. Our data, therefore, point to rapamycin as an attractive adjuvant to be used in combination with immunotherapy in a phase I clinical trial for GBM. Mol Cancer Ther; 13(12); 3024–36. ©2014 AACR.

JAK/STAT3 is one of the major signaling pathways that is aberrantly activated in ovarian cancer and associated with tumor progression and poor prognosis in patients with ovarian cancer. In this study, we evaluated the therapeutic potential of targeting JAK/STAT3 signaling in ovarian cancer using a peritoneal dissemination mouse model. We developed this mouse model by injecting a metastatic human ovarian cancer cell line, SKOV3-M-Luc, into the peritoneal cavity of immunodeficient mice. This model displayed a phenotype similar to late-stage ovarian cancer, including extensive peritoneal metastasis and ascites production. The constitutive activation of STAT3 in human ovarian cancer cells appeared to be mediated by an autocrine cytokine loop involving the IL6 family of cytokines and JAK1 kinase. shRNA-mediated knockdown of JAK1 or STAT3 in ovarian cancer cells led to reduced tumor growth, decreased peritoneal dissemination, and diminished ascites production, suggesting a critical role of STAT3 in ovarian cancer progression. Similar results were obtained when a small-molecule inhibitor (JAKi) of the JAK1 kinase was used to treat ovarian cancer in this model. In addition, we found that the expression level of IL6 was correlated with activation of STAT3 in ovarian cancer cells both in vitro and in vivo, suggesting a potential application of IL6 as a biomarker. Altogether, our results demonstrate that targeting JAK1/STAT3, using shRNA knockdown or a small-molecule inhibitor, effectively suppressed ovarian tumor progression and, therefore, could be a potential novel therapeutic approach for treating advanced ovarian cancer. Mol Cancer Ther; 13(12); 3037–48. ©2014 AACR.

Glioblastoma multiforme (GBM) is an extremely aggressive brain cancer with a median survival of less than 2 years. GBM is characterized by abnormal activation of receptor tyrosine kinase and constitutively activated STAT3. Although EGFR phosphorylation and STAT3 activation are essential for the maintenance of GBM cancer stem cells, the molecular mechanism underlying endosome-mediated STAT3 activation is not fully understood. In the current study, we showed that GTP-binding protein RRAD (RAS associated with diabetes, RAD) physically associates with EGFR, and EEA1, enhancing the stability and endosome-associated nuclear translocation of EGFR. Functionally, RRAD contributes to the activation of STAT3 and expression of the stem cell factors OCT4, NANOG, and SOX2, thereby enhancing self-renewing ability, tumor sphere formation, EMT, and in vivo tumorigenesis. Most importantly, RRAD contributes to poor survival in patients with GBM. RRAD expression is correlated with temozolomide resistance, and, conversely, depletion of RRAD leads to sensitization of highly temozolomide-resistant GBM cells. Our data collectively support a novel function of RRAD in STAT3 activation and provide evidence that RRAD acts as a positive regulator in the EGFR signaling pathway. These results demonstrate a critical role for RRAD in GBM tumorigenesis and provide a rationale for the development of pharmacologic inhibitors of RRAD in GBM. Mol Cancer Ther; 13(12); 3049–61. ©2014 AACR.

The EZH2 methyltransferase silences gene expression through methylation of histone H3 on lysine 27 (H3K27). Recently, EZH2 mutations have been reported at Y641, A677, and A687 in non-Hodgkin lymphoma. Although the Y641F/N/S/H/C and A677G mutations exhibit clearly increased activity with substrates dimethylated at lysine 27 (H3K27me2), the A687V mutant has been shown to prefer a monomethylated lysine 27 (H3K27me1) with little gain of activity toward H3K27me2. Herein, we demonstrate that despite this unique substrate preference, A687V EZH2 still drives increased H3K27me3 when transiently expressed in cells. However, unlike the previously described mutants that dramatically deplete global H3K27me2 levels, A687V EZH2 retains normal levels of H3K27me2. Sequencing of B-cell–derived cancer cell lines identified an acute lymphoblastic leukemia cell line harboring this mutation. Similar to exogenous expression of A687V EZH2, this cell line exhibited elevated H3K27me3 while possessing H3K27me2 levels higher than Y641- or A677-mutant lines. Treatment of A687V EZH2-mutant cells with GSK126, a selective EZH2 inhibitor, was associated with a global decrease in H3K27me3, robust gene activation, caspase activation, and decreased proliferation. Structural modeling of the A687V EZH2 active site suggests that the increased catalytic activity with H3K27me1 may be due to a weakened interaction with an active site water molecule that must be displaced for dimethylation to occur. These findings suggest that A687V EZH2 likely increases global H3K27me3 indirectly through increased catalytic activity with H3K27me1 and cells harboring this mutation are highly dependent on EZH2 activity for their survival. Mol Cancer Ther; 13(12); 3062–73. ©2014 AACR.

Advanced gastric cancer is one of the most aggressive gastrointestinal malignancies, and ADAM (A disintegrin and metalloproteinase)-9 is a cell-surface membrane glycoprotein with oncogenic properties that is overexpressed in several cancers. Herein, we investigated the biologic mechanism of ADAM9 in the progression, proliferation, and invasion of gastric cancer. First, we detected ADAM's expression, processing, and protease activity in gastric cancer cells. Protease activity was moderately correlated with ADAM9 protein expression, but was better related to a processed smaller molecular weight (84 kDa) form of ADAM9. Knockdown of ADAM9 or specifically targeted monoclonal antibody (RAV-18) suppressed cancer cell proliferation and invasion in high ADAM9-expressing cells, not in low ADAM9-expressing cells. RAV-18 showed in vivo antitumor activity in a gastric cancer xenograft model. Hypoxia (1% oxygen) induced ADAM9 expression and functional activity in low ADAM9-expressing gastric cancer cells that was inhibited by siRNA knockdown or RAV-18 antibody to levels in normoxic cells. Overall, our studies show that ADAM9 plays an important role in gastric cancer proliferation and invasion, and that while expressed in some gastric cancer cells at high levels that are responsive to functional inhibition and antitumor activity of a catalytic site–directed antibody, other gastric cancer cells have low levels of expression and only when exposed to hypoxia do ADAM9 levels increase and the cells become responsive to ADAM9 antibody inhibition. Therefore, our findings suggest that ADAM9 could be an effective therapeutic target for advanced gastric cancer. Mol Cancer Ther; 13(12); 3074–85. ©2014 AACR.

PTENP1 is a pseudogene of the PTEN tumor suppression gene (TSG). The functions of PTENP1 in clear-cell renal cell carcinoma (ccRCC) have not yet been studied. We found that PTENP1 is downregulated in ccRCC tissues and cells due to methylation. PTENP1 and PTEN are direct targets of miRNA miR21 and their expression is suppressed by miR21 in ccRCC cell lines. miR21 expression promotes ccRCC cell proliferation, migration, invasion in vitro, and tumor growth and metastasis in vivo. Overexpression of PTENP1 in cells expressing miR21 reduces cell proliferation, invasion, tumor growth, and metastasis, recapitulating the phenotypes induced by PTEN expression. Overexpression of PTENP1 in ccRCC cells sensitizes these cells to cisplatin and gemcitabine treatments in vitro and in vivo. In clinical samples, the expression of PTENP1 and PTEN is correlated, and both expressions are inversely correlated with miR21 expression. Patients with ccRCC with no PTENP1 expression have a lower survival rate. These results suggest that PTENP1 functions as a competing endogenous RNA (ceRNA) in ccRCC to suppress cancer progression. Mol Cancer Ther; 13(12); 3086–97. ©2014 AACR.

The prognosis for patients with unresectable advanced or recurrent gastric cancer remains poor. The identification of additional oncogenes with influences similar to those of epidermal growth factor receptor gene mutations, upon which the growth of cancer cells is dependent, is needed. In this study, we evaluated sensitivity to MEK inhibitors (GSK1120212 and PD0325901) in several gastric cancer cell lines in vitro and found three poorly differentiated gastric cancer cell lines that were hypersensitive to the inhibitors. The sequence analyses in these three cell lines revealed that one cell line had a novel MEK1 mutation, while the other two had previously reported KRAS and MEK1 mutations, respectively; the gene statuses of the other resistant cell lines were all wild-type. Experiments using MEK1 expression vectors demonstrated that the MEK1 mutations induced the phosphorylation of ERK1/2 and had a transforming potential, enhancing the tumorigenicity. The MEK inhibitor dramatically reduced the phosphorylation of ERK1/2 and induced apoptosis in the cell lines with MEK1 mutations. In vivo, tumor growth was also dramatically decreased by an inhibitor. One of the 46 gastric cancer clinical samples that were examined had a MEK1 mutation; this tumor had a poorly differentiated histology. Considering the addiction of cancer cells to active MEK1 mutations for proliferation, gastric cancer with such oncogenic MEK1 mutations might be suitable for targeted therapy with MEK inhibitors. Mol Cancer Ther; 13(12); 3098–106. ©2014 AACR.

This study was conducted to examine the effects of doxycycline on the survival time and proliferation of hepatocellular carcinoma (HCC) in vivo and on the biologic functions of HCC in vitro. This study was also designed to evaluate the effects of doxycycline on epithelial-to-mesenchymal transition (EMT)– and vasculogenic mimicry (VM)–related protein expression and on matrix metalloproteinase (MMP) and DNA methyltransferase (DNMT) activity in vitro. Human MHCC97H cells were injected into BALB/c mice, which were divided into treatment and control groups. Doxycycline treatment prolonged the mouse survival time and partly suppressed the growth of engrafted HCC tumor cells, with an inhibition rate of 43.39%. Higher amounts of VM and endothelium-dependent vessels were found in the control group than the treatment group. IHC indicated that epithelial (E)-cadherin expression was increased in the doxycycline-treated mice compared with the control group. In in vitro experiments, doxycycline promoted HCC cell adhesion but inhibited HCC cell viability, proliferation, migration, and invasion. Western blot analysis, semiquantitative RT-PCR, qRT-PCR, and immunofluorescence demonstrated that doxycycline inhibited the degradation of the epithelial marker E-cadherin and downregulated the expression levels of EMT promoters, the mesenchymal marker vimentin, and the VM-associated marker vascular endothelial (VE)-cadherin. Furthermore, the activities of MMPs and DNMTs were examined in different groups via gelatin zymography and a DNMT activity assay kit. A methylation-specific PCR was performed to assess the promoter methylation of CDH1 (the gene encoding E-cadherin). Doxycycline prolonged the mouse survival time by inhibiting EMT progression and VM formation. Mol Cancer Ther; 13(12); 3107–22. ©2014 AACR.

Ovarian cancer is the second leading cause of cancer-related death in women worldwide. Despite optimal cytoreduction and adequate adjuvant therapies, initial tumor response is often followed by relapse suggesting the existence of a tumor niche. Targeted therapies have been evaluated in ovarian cancer to overcome resistant disease. Among them, antiangiogenic therapies inhibit new blood vessel growth, induce endothelial cell apoptosis, and block the incorporation of hematopoietic and endothelial progenitor cells into new blood vessels. Despite in vitro and in vivo successes, antivascular therapy with bevacizumab targeting VEGF-A has limited efficacy in ovarian cancer. The precise molecular mechanisms underlying clinical resistance to anti-VEGF therapies are not yet well understood. Among them, tumor and stromal heterogeneity might determine the treatment outcomes. The present study investigates whether abnormalities in the tumor endothelium may contribute to treatment resistance to bevacizumab and promote a residual microscopic disease. Here, we showed that ovarian cancer cells activate Akt phosphorylation in endothelial cells inducing resistance to bevacizumab leading to an autocrine loop based on FGF2 secretion. Altogether, our results point out the role of an activated endothelium in the resistance to bevacizumab and in the constitution of a niche for a residual disease. Mol Cancer Ther; 13(12); 3123–36. ©2014 AACR.

MicroRNA-200c (miR200c) recently emerged as an important regulator of tumorigenicity and cancer metastasis; however, its role in regulating multidrug resistance (MDR) remains unknown. In the current study, we found that the expression levels of miR200c in recurrent and metastatic colorectal cancers were significantly lower, whereas the JNK2 expression was higher compared with primary tumors. We showed that in MDR colorectal cancer cells, miR200c targeted the 3' untranslated region of the JNK2 gene. Overexpression of miR200c attenuated the levels of p-JNK, p-c-Jun, P-gp, and MMP-2/-9, the downstream factors of the JNK signaling pathway, resulting in increased sensitivity to chemotherapeutic drugs, which was accompanied by heightened apoptosis and decreased cell invasion and migration. Moreover, in an orthotopic MDR colorectal cancer mouse model, we demonstrated that overexpression of miR200c effectively inhibited the tumor growth and metastasis. At last, in the tumor samples from patients with locally advanced colorectal cancer with routine postsurgical chemotherapy, we observed an inverse correlation between the levels of mRNA expression of miR200c and JNK2, ABCB1, and MMP-9, thus predicting patient therapeutic outcomes. In summary, we found that miR200c negatively regulated the expression of JNK2 gene and increased the sensitivity of MDR colorectal cancer cells to chemotherapeutic drugs, via inhibiting the JNK2/p-JNK/p-c-Jun/ABCB1 signaling. Restoration of miR200c expression in MDR colorectal cancer may serve as a promising therapeutic approach in MDR-induced metastasis. Mol Cancer Ther; 13(12); 3137–51. ©2014 AACR.

Patients with non–small cell lung cancer (NSCLC) with malignant pleural effusion (MPE) have a short median survival time and increased regulatory T cells (Treg). However, it is unclear whether some specific factors in MPE are involved in Treg recruitment in the progression of NSCLC. Here, we found that Treg population was increased in MPE and inversely correlated with patient survival (P < 0.001). Increased level of CXCL1 in MPE was associated with recruitment of Tregs (P < 0.01). Moreover, miR141 regulated expression of CXCL1 in lung cancer cells, whereas the luciferase test confirmed that CXCL1 is a target of miR141. Chemotaxis assay showed that the miR141–CXCL1–CXCR2 pathway regulates migration of Tregs into MPE. Furthermore, miR141 significantly inhibited tumor growth and metastasis in an immune-competent mouse model. This suppressive function was mediated by the CXCL1–CXCR2 pathway and recruitment of Tregs. Our study uncovered a causative link between microRNA and development of MPE. Mechanistically, decreased expressions of miR141, associated with the survival of patients with NSCLC with MPE, resulted in the increased production of CXCL1 and recruitment of Tregs to promote immune escape of tumor. Mol Cancer Ther; 13(12); 3152–62. ©2014 AACR.

Nasopharyngeal carcinoma (NPC) is a malignant tumor originating in the epithelium. Radiotherapy is the standard therapy, but tumor resistance to this treatment reduces the 5-year patient survival rate dramatically. Studies are urgently needed to elucidate the mechanism of NPC radioresistance. Epigenetics—particularly microRNAs (miRNA) and DNA methylation—plays an important role in carcinogenesis and oncotherapy. We used qRT-PCR analysis and identified an miRNA signature from differentially expressed miRNAs. Our objectives were to identify the role of miR24 in NPC tumorigenesis and radioresistance and to identify the mechanisms by which miR24 is regulated. We found that miR24 inhibited NPC cell growth, promoted cell apoptosis, and suppressed the growth of NPC xenografts. We showed that miR24 was significantly downregulated in recurrent NPC tissues. When combined with irradiation, miR24 acted as a radiosensitizer in NPC cells. One of the miR24 precursors was embedded in a CpG island. Aberrant DNA methylation was involved in NPC response to radiotherapy, which linked inactivation of miR24 through hypermethylation of its precursor promoter with NPC radioresistance. Treating NPC cells with the DNA-hypomethylating agent 5-aza-2'-deoxycytidine compensated for the reduced miR24 expression. Together, our findings showed that miR24 was negatively regulated by hypermethylation of its precursor promoter in NPC radioresistance. Our findings defined a central role for miR24 as a tumor-suppressive miRNA in NPC and suggested its use in novel strategies for treatment of this cancer. Mol Cancer Ther; 13(12); 3163–74. ©2014 AACR.

Patients with metastatic triple-negative breast cancer (TNBC) have poor treatment outcomes. We reviewed the electronic records of consecutive patients with metastatic TNBC treated in phase I clinic at MD Anderson Cancer Center (Houston, TX) between Augu st 2005 and May 2012. One hundred and six patients received at least 1 phase I trial. Twelve of 98 evaluable patients (12%) had either complete response (CR; n = 1), partial response (PR; n = 7), or stable disease ≥6 months (SD; n = 4). Patients treated on matched therapy (n = 16) compared with those on nonmatched therapy (n = 90) had improved SD ≥ 6 months/PR/CR (33% vs. 8%; P = 0.018) and longer progression-free survival (PFS; median, 6.4 vs. 1.9 months; P = 0.001). Eleven of 57 evaluable patients (19%) treated with combination chemotherapy and targeted therapy had SD ≥ 6 months/PR/CR versus 1 of 41 evaluable patients (2%) treated on other phase I trials (P = 0.013), and longer PFS (3.0 vs. 1.6 months; P < 0.0001). Patients with molecular alterations in the PI3K/AKT/mTOR pathway treated on matched therapy (n = 16) had improved PFS compared with those with and without molecular alterations treated on nonmatched therapy (n = 27; 6.4 vs. 3.2 months; P = 0.036). On multivariate analysis, improved PFS was associated with treatment with combined chemotherapy and targeted agents (P = 0.0002), ≤2 metastatic sites (P = 0.003), therapy with PI3K/AKT/mTOR inhibitors for those with cognate pathway abnormalities (P = 0.018), and treatment with antiangiogenic agents (P = 0.023). In summary, combinations of chemotherapy and angiogenesis and/or PI3K/AKT/mTOR inhibitors demonstrated improved outcomes in patients with metastatic TNBC. Mol Cancer Ther; 13(12); 3175–84. ©2014 AACR.

Breast cancer is a major public health problem all over the world, and the current treatment strategies are not potent enough for some patients, especially those with triple-negative breast cancer (TNBC). Recent studies have demonstrated that microRNAs (miRNA) play vital roles in the development of TNBC. In this study, we found that miR-185 was strongly downregulated in TNBC tissues and cell lines and that its expression levels were associated with lymph node metastasis, clinical stage, overall survival, and relapse-free survival in TNBC. We also found that ectopic expression of miR-185 inhibited TNBC cell proliferation in vitro and in vivo. We further identified that miR-185 directly targeted DNMT1 and E2F6, which resulted in a marked increase in the expression of BRCA1 at the mRNA and protein levels in TNBC. Our data suggest that miR-185 functions as a tumor suppressor in TNBC development. It is a promising prognostic biomarker and potential therapeutic target for TNBC. Mol Cancer Ther; 13(12); 3185–97. ©2014 AACR.

Aberrant activation of Notch and Ras pathways has been detected in breast cancers. A synergy between these two pathways has also been shown in breast cell transformation in culture. Yet, the clinical relevance of Notch–Ras cooperation in breast cancer progression remains unexplored. In this study, we show that coordinate hyperactivation of Notch1 and Ras/MAPK pathways in breast cancer patient specimens, as assessed by IHC for cleaved Notch1 and pErk1/2, respectively, correlated with early relapse to vital organs and poor overall survival. Interestingly, majority of such Notch1highErkhigh cases encompassed the highly aggressive triple-negative breast cancers (TNBC), and were enriched in stem cell markers. We further show that combinatorial inhibition of Notch1 and Ras/MAPK pathways, using a novel mAb against Notch1 and a MEK inhibitor, respectively, led to a significant reduction in proliferation and survival of breast cancer cells compared with individual inhibition. Combined inhibition also abrogated sphere-forming potential, and depleted the putative cancer stem-like cell subpopulation. Most importantly, combinatorial inhibition of Notch1 and Ras/MAPK pathways completely blocked tumor growth in a panel of breast cancer xenografts, including the TNBCs. Thus, our study identifies coordinate hyperactivation of Notch1 and Ras/MAPK pathways as novel biomarkers for poor breast cancer outcome. Furthermore, based on our preclinical data, we propose combinatorial targeting of these two pathways as a treatment strategy for highly aggressive breast cancers, particularly the TNBCs that currently lack any targeted therapeutic module. Mol Cancer Ther; 13(12); 3198–209. ©2014 AACR.

BRAF inhibitors (BRAFi) have led to clinical benefit in patients with melanoma. The development of a blood-based assay to detect and quantify BRAF levels in these patients has diagnostic, prognostic, and predictive capabilities that could guide treatment decisions. Blood BRAFV600E detection and quantification were performed on samples from 128 patients with stage II (19), III (67), and IV (42) melanoma. Tissue BRAF analysis was performed in all patients with stage IV disease and in selected patients with stage II and III disease. Clinical outcomes were correlated to initial BRAF levels as well as BRAF level dynamics. Serial analysis was performed on 17 stage IV melanoma patients treated with BRAFi and compared with tumor measurements by RECIST. The assay was highly sensitive (96%) and specific (95%) in the stage IV setting, using a blood level of 4.8 pg as "positive." BRAF levels typically decreased following BRAFi. A subset of these patients (5) had an increase in BRAFV600E values 42 to 112 days before clinical or radiographic disease progression (PD). From 86 patients with resected, stage II or III melanoma, 39 had evidence of disease relapse (45.3%). Furthermore, BRAF mutation in the blood after surgical resection in these patients was not associated with a difference in relapse risk, although tissue BRAF status was only available for a subset of patients. In summary, we have developed a highly sensitive and specific, blood-based assay to detect BRAFV600 mutation in patients with melanoma. Mol Cancer Ther; 13(12); 3210–8. ©2014 AACR.

Human aggressive B-cell non-Hodgkin lymphomas (NHL) encompass the continuum between Burkitt lymphoma and diffuse large B-cell lymphoma (DLBCL), and display considerable clinical and biologic heterogeneity, most notably related to therapy response. We previously showed that lymphomas arising in the Eμ-Myc transgenic mouse are heterogeneous, mirroring genomic differences between Burkitt lymphoma and DLBCL. Given clinical heterogeneity in NHL and the need to develop strategies to match therapeutics with discrete forms of disease, we investigated the extent to which genomic variation in the Eμ-Myc model predicts response to therapy. We used genomic analyses to classify Eμ-Myc lymphomas, link Eμ-Myc lymphomas with NHL subtypes, and identify lymphomas with predicted resistance to conventional and NF-B–targeted therapies. Experimental evaluation of these predictions links genomic profiles with distinct outcomes to conventional and targeted therapies in the Eμ-Myc model, and establishes a framework to test novel targeted therapies or combination therapies in specific genomically defined lymphoma subgroups. In turn, this will rationally inform the design of new treatment options for aggressive human NHL. Mol Cancer Ther; 13(12); 3219–29. ©2014 AACR.

Large-scale cancer datasets such as The Cancer Genome Atlas (TCGA) allow researchers to profile tumors based on a wide range of clinical and molecular characteristics. Subsequently, TCGA-derived gene expression profiles can be analyzed with the Connectivity Map (CMap) to find candidate drugs to target tumors with specific clinical phenotypes or molecular characteristics. This represents a powerful computational approach for candidate drug identification, but due to the complexity of TCGA and technology differences between CMap and TCGA experiments, such analyses are challenging to conduct and reproduce. We present Cancer in silico Drug Discovery (CiDD; scheet.org/software), a computational drug discovery platform that addresses these challenges. CiDD integrates data from TCGA, CMap, and Cancer Cell Line Encyclopedia (CCLE) to perform computational drug discovery experiments, generating hypotheses for the following three general problems: (i) determining whether specific clinical phenotypes or molecular characteristics are associated with unique gene expression signatures; (ii) finding candidate drugs to repress these expression signatures; and (iii) identifying cell lines that resemble the tumors being studied for subsequent in vitro experiments. The primary input to CiDD is a clinical or molecular characteristic. The output is a biologically annotated list of candidate drugs and a list of cell lines for in vitro experimentation. We applied CiDD to identify candidate drugs to treat colorectal cancers harboring mutations in BRAF. CiDD identified EGFR and proteasome inhibitors, while proposing five cell lines for in vitro testing. CiDD facilitates phenotype-driven, systematic drug discovery based on clinical and molecular data from TCGA. Mol Cancer Ther; 13(12); 3230–40. ©2014 AACR.