The major histocompatibility complex class I polypeptide-related sequence A gene (MICA) encodes a membrane-bound protein acting as a ligand to stimulate an activating receptor, NKG2D, expressed on the surface of essentially all human natural killer (NK), T and CD8+ αβ T cells. MICA protein is absent from most cells but can be induced by infections and oncogenic transformation and is frequently expressed in epithelial tumors. Upon binding to MICA, NKG2D activates cytolytic responses of NK and T cells against infected and tumor cells expressing MICA. Therefore, membrane-bound MICA acts as a signal during the early immune response against infection or spontaneously arising tumors. On the other hand, human tumor cells spontaneously release a soluble form of MICA, causing the downregulation of NKG2D and in turn severe impairment of the antitumor immune response of NK and CD8+ T cells. This is considered to promote tumor immune evasion and also to compromise host resistance to infections. MICA is the most polymorphic non-classical class I gene. A possible association of MICA polymorphism with genetic predisposition to different cancer types has been investigated in candidate gene-based studies. Two genome-wide association studies have identified loci in MICA that influence susceptibility to cervical neoplasia and hepatitis C virus-induced hepatocellular carcinoma, respectively. Given the current level of interest in the field of MICA gene, we discuss the genetics and biology of the MICA gene and the role of its polymorphism in cancer. Gaps in our understanding and future research needs are also discussed.
Base excision repair (BER) is a frontline defense mechanism for dealing with many common forms of endogenous DNA damage, several of which can drive mutagenic or cell death outcomes. The pathway engages proteins such as glycosylases, abasic endonucleases, polymerases and ligases to remove substrate modifications from DNA and restore the genome back to its original state. Inherited mutations in genes related to BER can give rise to disorders involving cancer, immunodeficiency and neurodegeneration. Studies employing genetically defined heterozygous (haploinsufficient) mouse models indicate that partial reduction in BER capacity can increase vulnerability to both spontaneous and exposure-dependent pathologies. In humans, measurement of BER variation has been imperfect to this point, yet tools to assess BER in epidemiological surveys are steadily evolving. We provide herein an overview of the BER pathway and discuss the current efforts toward defining the relationship of BER defects with disease susceptibility.
Recent studies identified three genetic loci reproducibly associated with lung cancer in populations of European ancestry, namely 15q25, 5p15 and 6p21. The goals of this study are first to confirm whether these loci are associated with lung cancer in a French Canadian population and second to identify disease-associated single nucleotide polymorphisms (SNPs) influencing messenger RNA (mRNA) expression levels of genes in the lung, that is expression quantitative trait loci (eQTLs). SNPs were genotyped in 420 patients undergoing lung cancer surgery and compared with 3151 controls of European ancestry. Genome-wide gene expression levels in non-tumor lung tissues of the same 420 patients were also measured to identify eQTLs. Significant eQTLs were then followed-up in two replication sets (n = 339 and 363). SNPs found in the three susceptibility loci were associated with lung cancer in the French Canadian population. Strong eQTLs were found on chromosome 15q25 with the expression levels of CHRNA5 (P = 2.23 x 10–22 with rs12907966). The CHRNA5-rs12907966 eQTL was convincingly validated in the two replication sets (P = 3.46 x 10–16 and 2.01 x 10–15). On 6p21, a trend was observed for rs3131379 to be associated with the expression of APOM (P = 3.58 x 10–4) and validated in the replication sets (P = 1.11 x 10–8 and 6.84 x 10–4). On 5p15, no significant eQTLs were found. This study confirmed that chromosomes 15q25, 5p15 and 6p21 harbored susceptibility loci for lung cancer in French Canadians. Most importantly, this study suggests that the risk alleles at 15q25 and 6p21 may mediate their effect by regulating the mRNA expression levels of CHRNA5 and APOM in the lung.
Coumarins are plant-derived natural products with a broad range of known pharmacological activities including anticancer effects. However, the molecular mechanisms by which this class of promising compounds exerts their anticancer effects remain largely unknown. We report here that a furanocoumarin named apaensin could effectively induce apoptosis of cancer cells through its activation of Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase (MAPK). Apoptosis induction by apaensin in cancer cells was suppressed by chemical inhibitors of JNK and p38 MAPK. Inhibition of the expression of orphan nuclear receptor Nur77 by small interfering RNA (siRNA) approach also abrogated the death effect of apaensin. Molecular analysis demonstrated that JNK activation was required for the nuclear export of Nur77, a known apoptotic event in cancer cells. Although p38 MAPK activation was not involved in Nur77 nuclear export, it was essential for Nur77 mitochondrial targeting through induction of Nur77 interaction with Bcl-2, which is also known to convert Bcl-2 from an antiapoptotic to a proapoptotic molecule. Together, our results identify a new natural product that targets orphan nuclear receptor Nur77 through its unique activation of JNK and p38 MAPK and provide insight into the complex regulation of the Nur77-Bcl-2 apoptotic pathway.
Pancreatic ductal adenocarcinoma (PDAC) is driven by the accumulation of somatic mutations, epigenetic modifications and changes in the micro-environment. New approaches to investigating disruptions of gene expression networks promise to uncover key regulators and pathways in carcinogenesis. We performed messenger RNA-sequencing in pancreatic normal (n = 10) and tumor (n = 8) derived tissue samples, as well as in pancreatic cancer cell lines (n = 9), to determine differential gene expression (DE) patterns. Sub-network enrichment analyses identified HNF1A as the regulator of the most significantly and consistently dysregulated expression sub-network in pancreatic tumor tissues and cells (median P = 7.56x10–7, median rank = 1, range = 1–25). To explore the effects of HNF1A expression in pancreatic tumor-derived cells, we generated stable HNF1A-inducible clones in two pancreatic cancer cell lines (PANC-1 and MIA PaCa-2) and observed growth inhibition (5.3-fold, P = 4.5x10–5 for MIA PaCa-2 clones; 7.2-fold, P = 2.2x10–5 for PANC-1 clones), and a G0/G1 cell cycle arrest and apoptosis upon induction. These effects correlated with HNF1A-induced down-regulation of 51 of 84 cell cycle genes (e.g. E2F1, CDK2, CDK4, MCM2/3/4/5, SKP2 and CCND1), decreased expression of anti-apoptotic genes (e.g. BIRC2/5/6 and AKT) and increased expression of pro-apoptotic genes (e.g. CASP4/9/10 and APAF1). In light of the established role of HNF1A in the regulation of pancreatic development and homeostasis, our data suggest that it also functions as an important tumor suppressor in the pancreas.
Myometrial infiltration represents a main clinical determinant of endometrial carcinomas (EC) presenting as aggressive high-grade deeply invasive neoplasms, substantially associated with risk of recurrence and death. The up-regulation of ETV5 transcription factor linked to the promotion of epithelial to mesenchymal transition is considered as a basic mechanism underlying the initial steps of EC invasion. In this work, we aimed to investigate the transcription program of tumor invasion regulated by ETV5. We performed a comparative Chip-on-chip analysis at invasive front and superficial area of human EC. ETV5 specific binding to promoter regions of genes related to cellular migration, adhesion and invasion at deep invasion tumor areas highlighted the relevance of neural networks associated with cellular plasticity. Interestingly, brain-derived neurotrophic factor (BDNF) demonstrated a principal role orchestrating ETV5-mediated epithelial-to-mesenchymal transition in endometrial cancer. Impairment of the BDNF/tropomyosin-related kinase B (TrkB)/extracellular signal-regulated kinase axis in endometrial cancer cell lines reversed the aggressive and invasive phenotype promoted by the up-regulation of ETV5 at the invasive front of EC. Likewise, BDNF directly impacted on the efficiency of ETV5 promoted metastasis in a mice model of endometrial distant dissemination. These results translate the recognized role of BDNF/TrkB on neural plasticity into a relevant cancer metastasis event; suggest common mechanisms shared by neural development and tumor invasion; and offer new therapeutic opportunities specifically directed against disseminated disease in endometrial cancer.
Gene fusion is among the primary processes that generate new genes and has been well characterized as potent pathway of oncogenesis. Here, by high-throughput RNA sequencing in nine paired human endometrial carcinoma (EC) and matched non-cancerous tissues, we obtained that chimeric translin-associated factor X–disrupted-in-schizophrenia 1 (TSNAX–DISC1) occurred significantly upregulated in multiple EC samples. Experimental investigation showed that TSNAX–DISC1 appears to be formed by splicing without chromosomal rearrangement. The chimera expression inversely correlated with the binding of CCCTC-binding factor (CTCF) to the insulators. Subsequent investigations indicate that long intergenic non-coding RNA lincRNA-NR_034037, separating TSNAX from DISC1, regulates TSNAX–DISC1 production and TSNAX/DISC1 expression levels by extricating CTCF from insulators. Dysregulation of TSNAX influences steroidogenic factor-1-stimulated transcription on the StAR promoter, altering progesterone actions, implying the association with cancer. Together, these results advance our understanding of the mechanism in which lincRNA-NR_034037 regulates TSNAX–DISC1 formation programs that tightly regulate EC development.
The chromosome 9p21 region has been implicated in the pathogenesis of multiple cancers. We analyzed 9p21 single nucleotide polymorphisms (SNPs) from eight genome-wide association studies (GWAS) with data deposited in dbGaP, including studies of esophageal squamous cell carcinoma (ESCC), gastric cancer (GC), pancreatic cancer, renal cell carcinoma (RCC), lung cancer (LC), breast cancer (BrC), bladder cancer (BC) and prostate cancer (PrC). The number of subjects ranged from 2252 (PrC) to 7619 (LC). SNP-level analyses for each cancer were conducted by logistic regression or random-effects meta-analysis. A subset-based statistical approach (ASSET) was performed to combine SNP-level P values across multiple cancers. We calculated gene-level P values using the adaptive rank truncated product method. We identified that rs1063192 and rs2157719 in the CDKN2A/2B region were significantly associated with ESCC and rs2764736 (3' of TUSC1) was associated with BC (P ≤ 2.59 x 10–6). ASSET analyses identified four SNPs significantly associated with multiple cancers: rs3731239 (CDKN2A intronic) with ESCC, GC and BC (P = 3.96 x 10–4); rs10811474 (3' of IFNW1) with RCC and BrC (P = 0.001); rs12683422 (LINGO2 intronic) with RCC and BC (P = 5.93 x 10–4) and rs10511729 (3' of ELAVL2) with LC and BrC (P = 8.63 x 10–4). At gene level, CDKN2B, CDKN2A and CDKN2B-AS1 were significantly associated with ESCC (P ≤ 4.70 x 10–5). Rs10511729 and rs10811474 were associated with cis-expression of 9p21 genes in corresponding cancer tissues in the expression quantitative trait loci analysis. In conclusion, we identified several genetic variants in the 9p21 region associated with the risk of multiple cancers, suggesting that this region may contribute to a shared susceptibility across different cancer types.
G-quadruplex (G4) structures in intron 3 of the p53 pre-mRNA modulate intron 2 splicing, altering the balance between the fully spliced p53 transcript (FSp53, encoding full-length p53) and an incompletely spliced transcript retaining intron 2 (p53I2 encoding the N-terminally truncated 40p53 isoform). The nucleotides forming G4s overlap the polymorphism rs17878362 (A1 wild-type allele, A2 16-base pair insertion) which is in linkage disequilibrium with rs1642785 in intron 2 (c.74+38 G>C). Biophysical and biochemical analyses show rs17878362 A2 alleles form similar G4 structures as A1 alleles although their position is shifted with respect to the intron 2 splice acceptor site. In addition basal FSp53 and p53I2 levels showed allele specific differences in both p53-null cells transfected with reporter constructs or lymphoblastoid cell lines. The highest FSp53 and p53I2 levels were associated with combined rs1642785-GG/rs17878362-A1A1 alleles, whereas the presence of rs1642785-C with either rs17878362 allele was associated with lower p53 pre-mRNA, total TP53, FSp53 and p53I2 levels, due to the lower stability of transcripts containing rs1642785-C. Treatment of lymphoblastoid cell with the G4 binding ligands 360A or PhenDC3 or with ionizing radiation increased FSp53 levels only in cells with rs17878362 A1 alleles, suggesting that under this G4 configuration full splicing is favoured. These results demonstrate the complex effects of intronic TP53 polymorphisms on G4 formation and identify a new role for rs1642785 on mRNA splicing and stability, and thus on the differential expression of isoform-specific transcripts of the TP53 gene.
Previous epidemiological studies suggest an inverse association between allergies, marked by elevated immunoglobulin (Ig) E levels, and non-Hodgkin lymphoma (NHL) risk. The evidence, however, is inconsistent and prospective data are sparse. We examined the association between prediagnostic total (low: <20; intermediate: 20–100; high >100 kU/l) and specific IgE (negative: <0.35; positive ≥0.35 kU/I) concentrations against inhalant antigens and lymphoma risk in a study nested within the European Prospective Investigation into Cancer and Nutrition cohort. A total of 1021 incident cases and matched controls of NHL, multiple myeloma (MM) and Hodgkin lymphoma with a mean follow-up time of 7 years were investigated. Multivariate-adjusted odds ratios (ORs) with 95% confidence intervals (CI) were calculated by conditional logistic regression. Specific IgE was not associated with the risk of MM, B-cell NHL and B-cell NHL subtypes. In contrast, total IgE levels were inversely associated with the risk of MM [high level: OR = 0.40 (95% CI = 0.21–0.79)] and B-cell NHL [intermediate level: OR = 0.68 (95% CI = 0.53–0.88); high level: OR = 0.62 (95% CI = 0.44–0.86)], largely on the basis of a strong inverse association with chronic lymphocytic leukemia [CLL; intermediate level: OR = 0.49 (95% CI = 0.30–0.80); high level: OR = 0.13 (95% CI = 0.05–0.35)] risk. The inverse relationship for CLL remained significant for those diagnosed 5 years after baseline. The findings of this large prospective study demonstrated significantly lower prediagnostic total IgE levels among CLL and MM cases compared with matched controls. This corresponds to the clinical immunodeficiency state often observed in CLL patients prior to diagnosis. No support for an inverse association between prediagnostic levels of specific IgE and NHL risk was found.
Current procedures for diagnosis and biomarker examination of colorectal cancer (CRC) are invasive and unpleasant. There is a great need to identify sensitive and specific biomarkers for early diagnosis of CRC. Circulating microRNAs (miRNAs) are promising molecular markers for CRC prediction. We performed a comprehensive meta-analysis to integrate an evaluation index for diagnostic accuracy of circulating miRNAs in diagnosing CRC patients. Furthermore, we conducted an independent validation set of 49 CRC patients and 49 healthy controls. In our meta-analysis, we found that miR-21 yielded a pooled area under ROC curve (AUC) of 0.867 (sensitivity: 76%, specificity: 82%) in discriminating CRC from controls, and miR-92a yielded a summary AUC of 0.803 (sensitivity: 77%, specificity: 68%); miR-21 had a higher diagnostic efficiency than miR-92a. In the further validation, plasma miR-21 levels in CRC patients were significantly higher than levels observed in healthy subjects. A ROC curve analysis showed a consistent result. However, this phenotype was not present in miR-92a. Moreover, the expression trend of miR-21 in plasma samples was in line with that of tissue samples, along with the cellular level. Current evidences suggest that plasma miR-21 could be a reliable and non-invasive biomarker for CRC diagnosis. Studies with larger cohorts that include the diagnostic value of plasma miR-21 for CRC are warranted.
The prognosis of gastric cancer (GC) patients with peritoneal dissemination remains poor, and a better understanding of the underlying mechanisms is critical for the development of new treatments that will improve survival in these patients. This study aimed to clarify the clinical and biological role of two key metastasis-associated long non-coding RNAs (lncRNAs) in GC. We analyzed the expression levels of two lncRNAs—Metastasis-Associated Lung Adenocarcinoma Transcript 1 (MALAT1) and HOX-Antisense Intergenic RNA (HOTAIR)—by real-time reverse transcription PCR in 300 gastric tissues (150 GC and 150 adjacent normal mucosa), and in seven GC cell lines. Functional characterization for the role of HOTAIR in GC was performed by small interfering RNA (siRNA) knockdown, followed by series of in-vitro and in-vivo experiments. Expression of both lncRNAs was significantly higher in cancerous tissues than in corresponding normal mucosa, and higher expression of these lncRNAs significantly correlated with peritoneal metastasis in GC patients. In addition, elevated HOTAIR expression emerged both as an independent prognostic and risk factor for peritoneal dissemination. SiRNA knockdown of HOTAIR in GC cells significantly inhibited cell proliferation, migration and invasion, but concurrently enhanced the anoikis rate in transfected cells. In an in vivo assay, HOTAIR siRNA-transfected MKN45 cells injected into nude mice inhibited the growth of xenograft tumors and peritoneal metastasis compared with controls. Our data provide novel evidence for the biological and clinical significance of HOTAIR expression as a potential biomarker for identifying patients with peritoneal metastasis, and as a novel therapeutic target in patients with gastric neoplasia.
Incidence of esophageal adenocarcinoma (EA) in Western countries has increased markedly in recent decades. Although several risk factors have been identified for EA and its precursor, Barrett’s esophagus (BE), including reflux, Caucasian race, male gender, obesity, and smoking, less is known about the role of inherited genetic variation. Frequent somatic mutations in the tumor suppressor genes CDKN2A and TP53 were recently reported in EA tumors, while somatic alterations at 9p (CDKN2A) and 17p (TP53) have been implicated as predictors of progression from BE to EA. Motivated by these findings, we used data from a genome-wide association study of 2515 EA cases and 3207 controls to analyze 37 germline single nucleotide polymorphisms at the CDKN2A and TP53 loci. Three CDKN2A polymorphisms were nominally associated (P < 0.05) with reduced risk of EA: rs2518720 C>T [intronic, odds ratio 0.90, P = 0.0121, q = 0.3059], rs3088440 G>A (3'UTR, odds ratio 0.84, P = 0.0186, q = 0.3059), and rs4074785 C>T (intronic, odds ratio 0.85, P = 0.0248, q = 0.3059). None of the TP53 single nucleotide polymorphisms reached nominal significance. Two of the CDKN2A variants identified were also associated with reduced risk of progression from BE to EA, when assessed in a prospective cohort of 408 BE patients: rs2518720 (hazard ratio 0.57, P = 0.0095, q = 0.0285) and rs3088440 (hazard ratio 0.34, P = 0.0368, q = 0.0552). In vitro functional studies of rs3088440, a single nucleotide polymorphism located in the seed sequence of a predicted miR-663b binding site, suggested a mechanism whereby the G>A substitution may attenuate miR-663b-mediated repression of the CDKN2A transcript. This study provides the first evidence that germline variation at the CDKN2A locus may influence EA susceptibility.
A growing amount of evidence supports that microRNA (miRNA) dysregulation is involved in cancer progression by directly downregulating multiple targets. Elucidating the underlying mechanism of miRNA in carcinogenesis may improve diagnostic and therapeutic strategies for malignancy. In the current study, we found that miR-105 expression was markedly downregulated in both hepatocellular carcinoma (HCC) cell lines and clinical HCC tissues, compared with normal human hepatocyte and adjacent non-cancerous tissues, respectively. Ectopic miR-105 expression suppressed, whereas inhibiting miR-105 promoted the proliferation and tumorigenicity of HCC cells both in vitro and in vivo. Furthermore, we demonstrated that miR-105 could deactivated the phosphoinositide 3-kinase (PI3K)/AKT signaling pathway by downregulating insulin receptor substrate-1, 3-phosphoinositide-dependent protein kinase-1 and AKT1 directly, resulting in increasing cyclin-dependent kinase inhibitors 1A and 1B (p21Cip1 and p27Kip1) and decreasing cyclin D1 expression in HCC. Therefore, our results suggest that miR-105 functions as a potential tumor suppressor by inhibiting the PI3K/AKT signaling pathway and might represent a potential therapeutic target for HCC patients.
Glioblastoma multiforme (GBM) is the most malignant primary brain tumor. The prognosis of GBM patients varies considerably and the histopathological examination is not sufficient for individual risk estimation. MicroRNAs (miRNAs) are small, non-coding RNAs that function as post-transcriptional regulators of gene expression and were repeatedly proved to play important roles in pathogenesis of GBM. In our study, we performed global miRNA expression profiling of 58 glioblastoma tissue samples obtained during surgical resections and 10 non-tumor brain tissues. The subsequent analysis revealed 28 significantly deregulated miRNAs in GBM tissue, which were able to precisely classify all examined samples. Correlation with clinical data led to identification of six-miRNA signature significantly associated with progression free survival [hazard ratio (HR) 1.98, 95% confidence interval (CI) 1.33–2.94, P < 0.001] and overa+ll survival (HR 2.86, 95% CI 1.91–4.29, P < 0.001). O(6)-methylguanine-DNA methyltransferase methylation status was evaluated as reference method and Risk Score based on six-miRNA signature indicated significant superiority in prediction of clinical outcome in GBM patients. Multivariate Cox analysis indicated that the Risk Score based on six-miRNA signature is an independent prognostic classifier of GBM patients. We suggest that the Risk Score presents promising prognostic algorithm with potential for individualized treatment decisions in clinical management of GBM patients.
DNA repair is a major mechanism for minimizing mutations and reducing cancer risk. Here, we present the development of reproducible and specific enzymatic assays for methylpurine DNA glycosylase (MPG) repairing the oxidative lesions 1,N6-ethenoadenine (A) and hypoxanthine (Hx) in peripheral blood mononuclear cells protein extracts. Association of these DNA repair activities with lung cancer was determined using conditional logistic regression with specimens from a population-based case–control study with 96 lung cancer cases and 96 matched control subjects. The mean MPG-A in case patients was 15.8 units/μg protein (95% CI 15.3–16.3), significantly higher than in control subjects—15.1 (14.6–15.5), *P = 0.011. The adjusted odds ratio for lung cancer associated with a one SD increase in MPG-A activity (2.48 units) was significantly bigger than 1 (OR = 1.6, 95% CI = 1.1–2.4; *P = 0.013). When activity of OGG1, a different DNA repair enzyme for oxidative damage, was included in the model, the estimated odds ratio/SD for a combined MPG-A-OGG1 score was 2.6 (95% CI 1.6–4.2) *P = 0.0001, higher than the odds ratio for each single assay. The MPG enzyme activity assays described provide robust functional risk biomarkers, with increased MPG-A activity being associated with increased lung cancer risk, similar to the behavior of MPG-Hx. This underscores the notion that imbalances in DNA repair, including high DNA repair, usually perceived as beneficial, can cause cancer risk. Such DNA repair risk biomarkers may be useful for risk assessment of lung cancer and perhaps other cancer types, and for early detection techniques such as low-dose CT.
The tumour-specific ‘pre-metastatic niche’ has emerged as a potential driving force for tumour metastasis and has been confirmed using mouse models of cancer metastasis. Vascular endothelial growth factor receptor-1+ hematopoietic progenitor cells (HPCs) have been shown to play an important role in metastasis, forming a ‘pre-metastatic niche’ at designated sites for distant tumour progression. Here, CD133+ human umbilical hematopoietic progenitor cells (HUHPCs) were purified from human umbilical cord blood and expanded in vitro. We studied the effects of CD133+ HUHPCs on the growth and metastasis of four colorectal cancer (CRC) cell lines by using cell-to-cell co-culture. Our results revealed that CD133+ HUHPCs promoted the proliferation and invasion of CRC cells in vitro and enhanced tumour growth and metastasis in vivo. Moreover, CD133+ HUHPCs were observed in the pre-metastatic liver tissue using immunohistochemical analysis after co-injection of SW480/EGFP+ cells and HUHPCs. Further experiments were therefore conducted to uncover the molecular mechanisms by which CD133+ HUHPCs influenced colon carcinogenesis and cancer progression. Extracted proteins were separated using the two-dimensional difference in gel electrophoresis technology. Among the differentially expressed proteins, mitogen-activated protein 4 kinase 4, stromal cell-derived factor-1, matrix metallopeptidase 9, calumenin, peripherin, leucine zipper, putative tumour suppressor 1 and guanidinoacetate methyltransferase attracted our attention. Western blot analysis further confirmed the differential expression of these proteins. Altogether, these results suggest that CD133+ HUHPCs may induce proliferation or metastasis of CRC cells and impact their derived proteins by providing a pre-metastatic microenvironment.
Sporadic and non-hereditary mutations account for the majority of colorectal cancers (CRC). After the loss of adenomatous polyposis coli (APC) function and activation of the β-catenin/LEF signaling pathway, activating mutations in Kras are major drivers of sporadic CRC. Preventing the outgrowth of cells that develop sporadic mutations will decrease CRC. Resveratrol, a naturally occurring polyphenolic compound has anti-inflammatory, anti-oxidant and anti-cancer activities. We used a genetically engineered mouse model for sporadic CRC where the APC locus is knocked out and Kras is activated specifically in the distal colon to determine the effects of resveratrol on preventing and treating CRC. Feeding mice a diet supplemented with 150 or 300 ppm resveratrol (105 and 210mg daily human equivalent dose, respectively) before tumors were visible by colonoscopy resulted in a 60% inhibition of tumor production. In the 40% of mice that did develop tumors Kras expression was lost in the tumors. In a therapeutic assay where tumors were allowed to develop prior to treatment, feeding tumor bearing mice with resveratrol resulted in a complete remission in 33% of the mice and a 97% decrease in tumor size in the remaining mice. Analysis of miRNA expression in non-tumoral and tumoral colonic tissue of resveratrol treated mice showed an increased expression of miR-96, a miRNA previously shown to regulate Kras translation. These data indicate that resveratrol can prevent the formation and growth of colorectal tumors by downregulating Kras expression.
Cannabigerol (CBG) is a safe non-psychotropic Cannabis-derived cannabinoid (CB), which interacts with specific targets involved in carcinogenesis. Specifically, CBG potently blocks transient receptor potential (TRP) M8 (TRPM8), activates TRPA1, TRPV1 and TRPV2 channels, blocks 5-hydroxytryptamine receptor 1A (5-HT1A) receptors and inhibits the reuptake of endocannabinoids. Here, we investigated whether CBG protects against colon tumourigenesis. Cell growth was evaluated in colorectal cancer (CRC) cells using the 3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyl tetrazolium bromide and 3-amino-7-dimethylamino-2-methylphenazine hydrochloride assays; apoptosis was examined by histology and by assessing caspase 3/7 activity; reactive oxygen species (ROS) production by a fluorescent probe; CB receptors, TRP and CCAAT/enhancer-binding protein homologous protein (CHOP) messenger RNA (mRNA) expression were quantified by reverse transcription–polymerase chain reaction; small hairpin RNA-vector silencing of TRPM8 was performed by electroporation. The in vivo antineoplastic effect of CBG was assessed using mouse models of colon cancer. CRC cells expressed TRPM8, CB1, CB2, 5-HT1A receptors, TRPA1, TRPV1 and TRPV2 mRNA. CBG promoted apoptosis, stimulated ROS production, upregulated CHOP mRNA and reduced cell growth in CRC cells. CBG effect on cell growth was independent from TRPA1, TRPV1 and TRPV2 channels activation, was further increased by a CB2 receptor antagonist, and mimicked by other TRPM8 channel blockers but not by a 5-HT1A antagonist. Furthermore, the effect of CBG on cell growth and on CHOP mRNA expression was reduced in TRPM8 silenced cells. In vivo, CBG inhibited the growth of xenograft tumours as well as chemically induced colon carcinogenesis. CBG hampers colon cancer progression in vivo and selectively inhibits the growth of CRC cells, an effect shared by other TRPM8 antagonists. CBG should be considered translationally in CRC prevention and cure.
4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is metabolized to enantiomers of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), found in the urine of virtually all people exposed to tobacco products. We assessed the carcinogenicity in male F-344 rats of (R)-NNAL (5 ppm in drinking water), (S)-NNAL (5 ppm), NNK (5 ppm) and racemic NNAL (10 ppm) and analyzed DNA adduct formation in lung and pancreas of these rats after 10, 30, 50 and 70 weeks of treatment. All test compounds induced a high incidence of lung tumors, both adenomas and carcinomas. NNK and racemic NNAL were most potent; (R)-NNAL and (S)-NNAL had equivalent activity. Metastasis was observed from primary pulmonary carcinomas to the pancreas, particularly in the racemic NNAL group. DNA adducts analyzed were O2-[4-(3-pyridyl)-4-oxobut-1-yl]thymidine (O2-POB-dThd), 7-[4-(3-pyridyl)-4-oxobut-1-yl]guanine(7-POB-Gua),O6-[4-(3-pyridyl)-4-oxobut-1-yl]deoxyguanosine(O6-POB-dGuo),the 4-(3-pyridyl)-4-hydroxybut-1-yl(PHB)adductsO2-PHB-dThd and 7-PHB-Gua, O6-methylguanine (O6-Me-Gua) and 4-hydroxy-1-(3-pyridyl)-1-butanone (HPB)-releasing adducts. Adduct levels significantly decreased with time in the lungs of rats treated with NNK. Pulmonary POB-DNA adducts and O6-Me-Gua were similar in rats treated with NNK and (S)-NNAL; both were significantly greater than in the (R)-NNAL rats. In contrast, pulmonary PHB-DNA adduct levels were greatest in the rats treated with (R)-NNAL. Total pulmonary DNA adduct levels were similar in (S)-NNAL and (R)-NNAL rats. Similar trends were observed for DNA adducts in the pancreas, but adduct levels were significantly lower than in the lung. The results of this study clearly demonstrate the potent pulmonary carcinogenicity of both enantiomers of NNAL in rats and provide important new information regarding DNA damage by these compounds in lung and pancreas.
Regulatory factor X-1 (RFX-1) is a transcription factor that has been linked to negative regulation of tumor progression; however, its biological function and signaling cascades are unknown. Here, we performed several studies to elucidate the roles of RFX-1 in the regulation of SHP-1 in hepatocellular carcinoma (HCC) cells. Overexpression of RFX-1 resulted in the activation of SHP-1 and repressed colony formation of HCC cells. In addition, by a mouse xenograft model, we demonstrated that RFX-1 overexpression also inhibited the tumor growth of HCC cells in vivo, suggesting that RFX-1 is of potential interest for small-molecule-targeted therapy. We also found that SC-2001, a bipyrrole molecule, induced apoptosis in HCC cells through activating RFX-1 expression. SC-2001 induced RFX-1 translocation from the cytosol to nucleus, bound to the SHP-1 promoter, and activated SHP-1 transcription. In a xenograft model, knockdown of RFX-1 reversed the antitumor effect of SC-2001. Notably, SC-2001 is much more potent than sorafenib, a clinically approved drug for HCC, in in vitro and in vivo assays. Our study confirmed that RFX-1 acts as a tumor suppressor in HCC and might be a new target for HCC therapy. The findings of this study also provide a new lead compound for targeted therapy via the activation of the RFX-1/SHP-1 pathway.
Peanut agglutinin (PNA), which accounts for ~0.15% of the weight of the common peanut, is a carbohydrate-binding protein that binds the oncofoetal Thomsen–Friedenreich (TF) disaccharide (galactoseβ1,3N-acetylgalactosamineα-) that is overexpressed by ~90% of human cancers. Previous studies have shown that PNA is highly resistant to cooking and digestion and rapidly enters the human blood circulation after peanut ingestion. This study investigates the hypothesis that PNA appearance in the circulation after peanut ingestion may mimic the actions of endogenous TF-binding human galectin-3 in metastasis promotion. It shows that PNA at concentrations similar to those found in blood circulation after peanut ingestion increases cancer cell heterotypic adhesion to the blood vascular endothelium and enhances the formation of tumour cell homotypic aggregates, two important steps in the metastasis cascade, and enhances metastasis in a mouse metastasis model. These effects of PNA are shown to result from its interaction with the cancer-associated TF disaccharide on the transmembrane mucin protein MUC1, causing MUC1 cell surface polarization that reveals underlying cell surface adhesion molecules. Thus, PNA appearance in the blood circulation after peanut ingestion mimics the actions of endogenous galectin-3 and promotes cancer cell metastatic spread by interaction with cancer-associated TF/MUC1. As metastasis accounts for the majority of cancer-associated fatality, regular consumption of peanuts by cancer patients would therefore be expected to have an adverse effect on cancer survival.
Nucleolar disruption has recently emerged as a relevant means to activate p53 through inhibition of HDM2 by ribosome-free RPL11. Most drugs that induce nucleolar disruption also possess important genotoxic activity, which can have lasting mutagenic effects. Therefore, it is of interest to identify compounds that selectively produce nucleolar disruption in the absence of DNA damage. Here, we have performed a high-throughput screening to search for nucleolar disruptors. We have identified an acridine derivative (PubChem CID-765471) previously known for its capacity to activate p53 independently of DNA damage, although the molecular mechanism underlying p53 activation had remained uncharacterized. We report that CID-765471 produces nucleolar disruption by inhibiting ribosomal DNA transcription in a process that includes the selective degradation of the RPA194 subunit of RNA polymerase I. Following nucleolar disruption, CID-765471 activates p53 through the RPL11/HDM2 pathway in the absence of detectable DNA damage. In a secondary screening of compounds approved for medical use, we identify two additional acridine derivatives, aminacrine and ethacridine, that operate in a similar manner as CID-765471. These findings provide the basis for non-genotoxic chemotherapeutic approaches that selectively target the nucleolus.