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Carcinogenesis - RSS feed of current issue

Glioblastoma is the most common and most aggressive primary brain malignancy. The current initial standard of care consists of maximal safe surgical resection followed by radical radiotherapy and adjuvant temozolomide. Despite optimal therapy, median survival is ~15 months from diagnosis in molecularly unselected patients, and <6 months for patients with recurrent disease. Therefore, clinical treatments are currently palliative, not curative. Collectively, current knowledge suggests that the continued tumor growth and recurrence is in part due to the presence of glioma stem-like cells, which display self-renewal and tumorigenic potential. They differ from their more differentiated progeny, as they are more resistant to current treatments. Recurrent disease may be a consequence of the enhancement and/or gain of stem cell-like characteristics during disease progression, together with preferential death of more differentiated tumor cells during treatment, signifying that the cancer stem cell phenotype is a crucial therapeutic target. The limited knowledge of the characteristics of these cells and their response to current clinical treatments warrants intensive investigation with the aim to improve patient survival and/or develop a cure for this disease.

The special AT-rich sequence-binding proteins 1 and 2 (SATB1/2) are nuclear matrix associated proteins that are transcription factors involved in chromatin remodeling and gene regulation. Expression of the SATB2 gene is tissue-specific, and the only epithelial cells expressing SATB2 are the glandular cells of the lower gastrointestinal tract where its expression is regulated by microRNA-31 (miR-31) and miR-182. SATB2, along with its homolog SATB1, are thought to be involved in various cancers with their roles in this disease being specific to the type of cancer. Colorectal cancer (CRC) provides the largest association of SATB2 with cancer and the roles of SATB2 are better defined and more studied in CRC than in any other cancer type. SATB1 displays a negative association with SATB2 in CRC. The various studies that have investigated the involvement of SATB1 and 2 in CRC have produced consistent findings. Here, we form four major conclusions regarding the role of these proteins in CRC and their potential clinical value: (i) SATB2 is a sensitive marker to distinguish CRC from other cancer types, (ii) Reduced expression of SATB2 in CRC is associated with poor prognosis, (iii) High levels of SATB1 expression facilitate CRC and are associated with poor prognosis and (iv) Overexpression of miR-31 and -182 in CRC leads to more aggressive cancer. This review will describe several of the key investigations that established these conclusions and highlight results that offer opportunities for future research in the treatment and diagnosis of CRC.

Alterations of epigenetic modifications are promising targets for cancer therapy, and several epigenetic drugs are now being clinically utilized. At the same time, individual epigenetic modifications have physiological functions in normal cells, and cancer cell specificity is considered difficult to achieve using a drug against a single epigenetic modification. To overcome this limitation, a combination of epigenetic modifications specifically or preferentially present in cancer cells is a candidate target. In this study, we aimed to demonstrate (i) the presence of a cancer cell-specific combination of epigenetic modifications by focusing on DNA methylation and trimethylation of histone H3 lysine 27 (H3K27me3) and (ii) the therapeutic efficacy of a combination of DNA demethylation and EZH2 inhibition. Analyses of DNA methylation and H3K27me3 in human colon, breast and prostate cancer cell lines revealed that 24.7±4.1% of DNA methylated genes had both DNA methylation and H3K27me3 (dual modification) in cancer cells, while it was 11.8±7.1% in normal cells. Combined treatment with a DNA demethylating agent, 5-aza-2'-deoxycytidine (5-aza-dC) and an EZH2 inhibitor, GSK126, induced marked re-expression of genes with the dual modification, including known tumor-suppressor genes such as IGFBP7 and SFRP1, and showed an additive inhibitory effect on growth of cancer cells in vitro. Finally, an in vivo combined treatment with 5-aza-dC and GSK126 inhibited growth of xenograft tumors more efficiently than a single treatment with 5-aza-dC. These results showed that the dual modification exists specifically in cancer cells and is a promising target for cancer cell-specific epigenetic therapy.

Lynch syndrome is caused by inactivating mutations in the MLH1 gene, but genetic variants of unclear significance frequently preclude diagnosis. Functional testing can reveal variant-conferred defects in gene or protein function. Based on functional defect frequencies and clinical applicability of test systems, we developed a functional testing strategy aimed at efficiently detecting pathogenic defects in coding MLH1 variants. In this strategy, tests of repair activity and expression are prioritized over analyses of subcellular protein localization and messenger RNA (mRNA) formation. This strategy was used for four unclear coding MLH1 variants (p.Asp41His, p.Leu507Phe, p.Gln689Arg, p.Glu605del + p.Val716Met). Expression was analyzed using a transfection system, mismatch repair (MMR) activity by complementation in vitro, mRNA formation by reverse transcriptase–PCR in carrier lymphocyte mRNA, and subcellular localization with dye-labeled fusion constructs. All tests included clinically meaningful controls. The strategy enabled efficient identification of defects in two unclear variants: the p.Asp41His variant showed loss of MMR activity, whereas the compound variant p.Glu605del + p.Val716Met had a defect of expression. This expression defect was significantly stronger than the pathogenic expression reference variant analyzed in parallel, therefore the defect of the compound variant is also pathogenic. Interestingly, the expression defect was caused additively by both of the compound variants, at least one of which is non-pathogenic when occurring by itself. Tests were neutral for p.Leu507Phe and p.Gln689Arg, and the results were consistent with available clinical data. We finally discuss the improved sensitivity and efficiency of the applied strategy and its limitations in analyzing unclear coding MLH1 variants.

Increased levels of soluble endoglin (Sol-Eng) correlate with poor outcome in human cancer. We have previously shown that shedding of membrane endoglin, and concomitant release of Sol-Eng is a late event in chemical mouse skin carcinogenesis associated with the development of undifferentiated spindle cell carcinomas (SpCCs). In this report, we show that mouse skin SpCCs exhibit a high expression of hepatocyte growth factor (HGF) and an elevated ratio of its active tyrosine kinase receptor Met versus total Met levels. We have evaluated the effect of Sol-Eng in spindle carcinoma cells by transfection of a cDNA encoding most of the endoglin ectodomain or by using purified recombinant Sol-Eng. We found that Sol-Eng inhibited both mitogen-activated protein kinase (MAPK) activity and cell growth in vitro and in vivo. Sol-Eng also blocked MAPK activation by transforming growth factor-β1 (TGF-β1) and impaired both basal and HGF-induced activation of Met and downstream MAPK. Moreover, Sol-Eng strongly reduced basal and HGF-stimulated spindle cell migration and invasion. Both Sol-Eng and full-length endoglin were shown to interact with Met by coimmunoprecipitation experiments. However, full-length endoglin expressed at the plasma membrane of spindle carcinoma cells had no effect on Met signaling activity, and was unable to inhibit HGF-induced cell migration/invasion. These results point to a paradoxical suppressor role for Sol-Eng in carcinogenesis.

The association between alcohol consumption, genetic polymorphisms of alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) and gastric cancer risk is not completely understood. We investigated the association between ADH1B (rs1229984), ADH1C (rs698) and ALDH2 (rs671) polymorphisms, alcohol consumption and the risk of gastric cancer among Japanese subjects in a population-based, nested, case–control study (1990–2004). Among 36 745 subjects who answered the baseline questionnaire and provided blood samples, 457 new gastric cancer cases matched to 457 controls were used in the analysis. The odds ratios (OR) and corresponding 95% confidence intervals (CI) were calculated using logistic regression models. No association was observed between alcohol consumption, ADH1B (rs1229984), ADH1C (rs698) and ALDH2 (rs671) polymorphisms and gastric cancer risk. However, considering gene–environmental interaction, ADH1C G allele carriers who drink ≥150g/week of ethanol had a 2.5-fold increased risk of gastric cancer (OR = 2.54, 95% CI = 1.05–6.17) relative to AA genotype carriers who drink 0 to <150g/week (P for interaction = 0.02). ALDH2 A allele carriers who drink ≥150g/week also had an increased risk (OR = 2.08, 95% CI = 1.05–4.12) relative to GG genotype carriers who drink 0 to < 150g/week (P for interaction = 0.08). To find the relation between alcohol consumption and gastric cancer risk, it is important to consider both alcohol consumption level and ADH1C and ALDH2 polymorphisms.

Glypican-3 (GPC3) protein expression was determined by immunohistochemical analysis from 29 normal livers, 80 cirrhotic livers sample taken near hepatocellular carcinoma (HCC), and 87 cirrhotic livers without HCC. The levels for miR-657 and HCC-related gene mRNAs were determined by quantitative real-time polymerase chain reaction (qRT-PCR). Also, a published microarray dataset was used for gene set enrichment analysis (GSEA) to investigate the relationship between GPC3- and HCC-related gene signatures. Kaplan–Meier analysis was used to evaluate the relationship between GPC3 and HCC recurrence. GPC3 protein expression was not detected in any of the 29 (0%) normal livers, but was detected in 32 of 87 (37%) cirrhotic livers without HCC, and 51 of 80 (64%) cirrhotic liver samples taken near HCC sites (P < 0.001). The GPC3-positive rate in cirrhotic livers of viral origin was 68% (27/40), which was significantly higher than for non-viral cirrhotic livers (11%, 5/47) (P < 0.001). Also, GPC3 expression positively correlated with mRNA expression of HCC-related genes in the qRT-PCR and GSEA evaluations. Furthermore, HCC recurrence in cirrhotic liver samples taken near HCC sites was significantly higher in the GPC3-positive group than the GPC3-negative group (Log-rank P = 0.02, HR = 3.26; 95% CI = 1.20–10.29). This study demonstrated that highly expression of GPC3 could enrich HCC-related genes’ mRNA expression and positive associate with dysplasia in cirrhotic livers. Therefore, GPC3 may serve as a precancerous biomarker in cirrhotic livers.

Liver function tests (LFTs) have been reported as independent predictors of non-liver disease-related morbidity and mortality in general population and cancer patients. In this study, we evaluated the relationship between pretreatment serum LFTs and overall survival (OS) in non-metastatic Caucasian breast cancer patients. Seven LFTs, including albumin, alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, lactate dehydrogenase (LDH), total bilirubin and total protein, were measured in pretreatment serum from 2425 female Caucasian patients with newly diagnosed, histologically confirmed non-metastatic invasive breast cancer. Multivariate Cox model was used to estimate hazard ratio (HR) and 95% confidence interval (CI) for the association of individual LFTs with 5-year OS while adjusting for age, smoking status, pathological characteristics and treatment regimen. We found that serum albumin, LDH and total bilirubin were significantly associated with 5-year OS in multivariate Cox analyses. Patients with higher albumin level exhibited 45% reduced risk of death (HR = 0.55, 95% CI: 0.40–0.75) compared with those with lower albumin level. Patients with higher total bilirubin level had a nearly 40% reduction in the risk of death (HR = 0.62, 95% CI: 0.45–0.85) and patients with higher LDH levels had a 1.42-fold increased risk of death (HR = 1.42, 95% CI: 1.08–1.88). Furthermore, cumulative analysis showed a significant dose–response trend of significantly increasing risk of death with increasing number of unfavorable LFT levels. Our result highlighted the potential of using pretreatment serum levels of albumin, LDH and total bilirubin as prognostic factors for OS in patients with non-metastatic breast cancer.

Variation of mitochondrial DNA copy number (mtDNAcn) in peripheral blood leukocytes has been associated with the risk of various cancers, including renal cell carcinoma (RCC). We assessed the association between mtDNAcn and clear cell RCC (ccRCC) risk in 608 cases and 629 controls frequency-matched on age and gender. Unconditional logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs) adjusting for age, gender, body mass index, smoking status, history of hypertension, total energy intake and physical activity. Our results suggest an association between low mtDNAcn and ccRCC risk (OR = 1.28, 95% CI: 0.97–1.68, P = 0.09). Lower mtDNAcn was associated with increased ccRCC risk in younger individuals (age <60, OR = 1.68, 95% CI: 1.13–2.49, P = 0.01), women (OR = 1.66, 95% CI: 1.03–2.73, P = 0.04), individuals without history of hypertension (OR = 1.62, 95% CI: 1.09–2.41, P = 0.02) and individuals with low physical activity levels (OR = 1.55, 95% CI: 1.02–2.37, P = 0.05). We observed significant and marginally significant interactions between both age and history of hypertension and mtDNAcn in elevating ccRCC risk (P for interaction = 0.04 and 0.07, respectively). Additionally, low mtDNAcn was associated with ccRCC risk in younger individuals with low levels of physical activity [ORs and 95% CI for medium and low physical activity levels, respectively, 2.31 (1.18–4.52) and 2.09 (1.17–3.75), P interaction = 0.04]. To our knowledge, this is the first report to investigate the role of mtDNAcn in the ccRCC subtype and the first to suggest that this association may be modified by risk factors including age, gender, history of hypertension and physical activity.

The chromosomal passenger complex (CPC) plays a pivotal role in the regulation of cell division. Therefore, inherited CPC variability could influence tumor development. The present candidate gene approach investigates the relationship between single nucleotide polymorphisms (SNPs) in genes encoding key CPC components and breast cancer risk. Fifteen SNPs in four CPC genes (INCENP, AURKB, BIRC5 and CDCA8) were genotyped in 88 911 European women from 39 case-control studies of the Breast Cancer Association Consortium. Possible associations were investigated in fixed-effects meta-analyses. The synonymous SNP rs1675126 in exon 7 of INCENP was associated with overall breast cancer risk [per A allele odds ratio (OR) 0.95, 95% confidence interval (CI) 0.92–0.98, P = 0.007] and particularly with estrogen receptor (ER)-negative breast tumors (per A allele OR 0.89, 95% CI 0.83–0.95, P = 0.0005). SNPs not directly genotyped were imputed based on 1000 Genomes. The SNPs rs1047739 in the 3' untranslated region and rs144045115 downstream of INCENP showed the strongest association signals for overall (per T allele OR 1.03, 95% CI 1.00–1.06, P = 0.0009) and ER-negative breast cancer risk (per A allele OR 1.06, 95% CI 1.02–1.10, P = 0.0002). Two genotyped SNPs in BIRC5 were associated with familial breast cancer risk (top SNP rs2071214: per G allele OR 1.12, 95% CI 1.04–1.21, P = 0.002). The data suggest that INCENP in the CPC pathway contributes to ER-negative breast cancer susceptibility in the European population. In spite of a modest contribution of CPC-inherited variants to the total burden of sporadic and familial breast cancer, their potential as novel targets for breast cancer treatment should be further investigated.

Desmoid tumors (DTs) are rare, mesenchymal tumors that exhibit features of an abundant wound healing process. Previously, we showed that mesenchymal stem cells (MSCs) are constituents of DTs and may contribute to desmoid tumorigenesis via activities associated with wound healing. Hyaluronan (HA) is a long-charged chain of repeating glucuronate and N-acetylglucosamine disaccharides that is synthesized by HA synthases (HAS) and degraded by hyaluronidases (HYAL). HA is secreted into the extracellular matrix by injured stroma and is important for normal tissue repair and neoplastic progression. Here, we investigated the presence of HA in DTs and the antitumor effects of the HA inhibitor, 4-methylumbelliferone (4-MU), on DT-derived mesenchymal cells. By immunohistochemistry and enzyme-linked immunosorbent assay, we found abundant expression of HA in 29/30 DTs as well as >5-fold increased HA levels in DT-derived cell lines relative to controls. Immunohistochemistry also demonstrated high expression of HAS2 in DTs, and quantitative PCR analysis showed increased HAS2 upregulation in frozen DTs and DT-derived cells. 4-MU treatment of DT-derived cells significantly decreased proliferation as well as HA and HAS2 levels. Fluorescent immunohistochemistry showed that MSCs in DTs coexpressed HA, HAS2, HYAL2, as well as the major HA receptor CD44 and HA coreceptor TLR4. Taken together, our results suggest that paracrine regulation of HA signaling in DTs may contribute to MSC recruitment and tumor proliferation. Future studies investigating the role of HA in tumor-stroma crosstalk and inhibition of HA-MSC interactions as a novel therapeutic target in DTs and other solid tumors are warranted.

Human studies and clues from animal models have provided important links between gastrointestinal (GI) tract bacteria and colon cancer. Gut microbiota antigenic stimuli play an important role in shaping the intestinal immune responses. Therefore, especially in the case of inflammation-associated colon cancer, gut bacteria antigens may affect tumorigenesis. The present study aimed to investigate the effects of the oral administration of a bacterial product with known immunomodulatory properties on inflammation-driven colorectal neoplasmatogenesis. For that, we used cholera-toxin and a well-established mouse model of colon cancer in which neoplasia is initiated by a single dose of the genotoxic agent azoxymethane (AOM) and subsequently promoted by inflammation caused by the colitogenic substance dextran sodium sulfate (DSS). We found that a single, low, non-pathogenic dose of CT, given orally at the beginning of each DSS treatment cycle downregulated neutrophils and upregulated regulatory T-cells and IL-10 in the colonic mucosa. The CT-induced disruption of the tumor-promoting character of DSS-induced inflammation led to the reduction of the AOM-initiated colonic polypoidogenesis. This result adds value to the emerging notion that certain GI tract bacteria or their products affect the immune system and render the microenvironment of preneoplastic lesions less favorable for promoting their evolution to cancer.

Non-steroidal anti-inflammatory drugs prevent colorectal cancer by inhibiting cyclooxygenase (COX) enzymes that synthesize tumor-promoting prostaglandins. 15-hydroxyprostaglandin dehydrogenase (15-PGDH) is a tumor suppressor that degrades tumor-promoting prostaglandins. Murine knockout of 15-PGDH increases susceptibility to azoxymethane-induced colon tumors. It also renders these mice resistant to celecoxib, a selective inhibitor of inducible COX-2 during colon neoplasia. Similarly, humans with low colonic 15-PGDH are also resistant to colon adenoma prevention with celecoxib. Here, we used aspirin and sulindac, which inhibit both COX-1 and COX-2, in order to determine if these broader COX inhibitors can prevent colon tumors in 15-PGDH knockout (KO) mice. Unlike celecoxib, sulindac proved highly effective in colon tumor prevention of 15-PGDH KO mice. Significantly, however, aspirin demonstrated no effect on colon tumor incidence in either 15-PGDH wild-type or KO mice, despite a comparable reduction in colonic mucosal Prostaglandin E2 (PGE2) levels by both sulindac and aspirin. Notably, colon tumor prevention activity by sulindac was accompanied by a marked induction of lymphoid aggregates and proximal colonic inflammatory mass lesions, a side effect seen to a lesser degree with celecoxib, but not with aspirin. These findings suggest that sulindac may be the most effective agent for colon cancer prevention in humans with low 15-PGDH, but its use may also be associated with inflammatory lesions in the colon.