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Carcinogenesis - RSS feed of current issue

Numerous studies investigated the associations of VDR polymorphisms with various types of cancer, suggesting an influence on cancer risk. FokI is one of the most frequently analysed polymorphisms but the results from single studies are contradictory. We performed a meta-analysis looking at the association between the FokI and all cancer sites and investigating sources of heterogeneity. We identified 77 independent studies up to April 2014. We presented the summary odds ratios (SORs) by cancer sites, ethnicity and study features. We found a significant association between FokI and ovarian cancer for ff genotype versus FF with no heterogeneity: SOR = 1.20 (95% CI: 1.02–1.41, I 2 = 0%). Moreover, we found a significant increased risk of any cancer: SOR = 1.08 (95% CI: 1.01–1.16, I 2 = 58%). A significant increased risk of any cancer is confirmed among Caucasian, among studies in Hardy–Weinberg equilibrium and nested case–control studies. Furthermore, among studies in Hardy–Weinberg equilibrium, skin cancer was found significantly associated with FokI: SOR = 1.24 (95% CI: 1.01–1.54; I 2 = 24%) for ff versus FF. The estimated number of cases attributable to ff genotype is 4221 for ovarian cancer and 52858 for skin cancer worldwide each year. No indication for publication bias was found for any cancer site. In conclusion, we found an overall significant association of FokI polymorphism with any cancer, with differential effect by ethnicity. In particular, the summary estimates indicate an increase risk for ovarian and skin cancer for ff versus FF. However, other factors may act modifying the association, and further studies are needed to clarify the impact on cancer risk.

Suppressive function of connexin(Cx)43 in carcinogenesis was recently contested by reports that showed a multifaceted function of Cx43 in cancer progression. These studies did not attempt to model the dynamics of intratumoral heterogeneity involved in the metastatic cascade. An unorthodox look at the phenotypic heterogeneity of prostate cancer cells in vitro enabled us to identify links between Cx43 functions and Snail-1-regulated functional speciation of invasive cells. Incomplete Snail-1-dependent phenotypic shifts accounted for the formation of phenotypically stable subclones of AT-2 cells. These subclones showed diverse predilection for invasive behavior. High Snail-1 and Cx43 levels accompanied high motility and nanomechanical elasticity of the fibroblastoid AT-2_Fi2 subclone, which determined its considerable invasiveness. Transforming growth factor-β and ectopic Snail-1 overexpression induced invasiveness and Cx43 expression in epithelioid AT-2 subclones and DU-145 cells. Functional links between Snail-1 function and Cx43 expression were confirmed by Cx43 downregulation and phenotypic shifts in AT-2_Fi2, DU-145 and MAT-LyLu cells upon Snail-1 silencing. Corresponding morphological changes and Snail-1 downregulation were seen upon Cx43 silencing in AT-2_Fi2 cells. This indicates that feedback loops between both proteins regulate cell invasive behavior. We demonstrate that Cx43 may differentially predispose prostate cancer cells for invasion in a coupling-dependent and coupling-independent manner. When extrapolated to in vivo conditions, these data show the complexity of Cx43 functions during the metastatic cascade of prostate cancer. They may explain how Cx43 confers a selective advantage during cooperative invasion of clonally evolving, invasive prostate cancer cell subpopulations.

Human papillomaviruses (HPVs) is the principal etiological agent of cervical cancer (CC). However, exposure to the high-risk type HPV alone is insufficient for tumor formation, and additional factors are required for the HPV-infected cells to become tumorigenic. Dysregulated microRNAs (miRNAs) expression is frequently observed in cancer but their roles in the formation of CC have not been fully revealed. In this study, we compared the expression of miR-135a in laser capture microdissected cervical specimens and confirmed overexpression of the miRNA in malignant cervical squamous cell carcinoma compared with precancerous lesions. Transient force-expression of miR-135a induced growth in low-density culture, anchorage-independent growth, proliferation and invasion of a HPV-16 E6/E7-immortalized cervical epithelial cell line, NC104-E6/E7. The observed effects were due to the inhibitory action of miR-135a on its direct target seven in absentia homolog 1 (SIAH1) leading to upregulation of β-catenin/T cell factor signaling. miR-135a force-expression enhanced the growth of HeLa- and NC104-E6/E7-derived tumor in vivo. The effect of miR-135a could be partially nullified by SIAH1 force-expression. More importantly, the expression of SIAH1 and β-catenin correlated with that of miR-135a in precancerous and cancerous lesions of cervical biopsies. By comparing the tumorigenic activities of miR-135a in E6/E7 positive/negative cell lines and in NC104-E6/E7 with or without E6/E7 knockdown, we demonstrated that HPV E6/E7 proteins are prerequisite for miR-135a as an oncomiR. Taken together, miR-135a/SIAH1/β-catenin signaling is important in the transformation and progression of cervical carcinoma.

Esophageal squamous cell carcinoma (ESCC) is the eighth most common cause of cancer-related death worldwide. However, previous genome-wide single nucleotide polymorphism association analyses have not explained the high heritability associated with ESCC. In this study, we performed genome-wide copy number variation (CNV) analysis on 128 discordant sibling pairs to identify novel genes that contribute to ESCC susceptibility. A total of 57 774 individual CNVs were identified, and an interactive network of common CNV-associated genes was constructed, which showed that several ABC transporter genes contain CNVs in ESCC patients. Independent validation of a CNV at 13q32.1 in 1048 northern Chinese Han subjects demonstrated that the amplification of ABCC4 significantly correlated with ESCC risk [odds ratio: 3.36 (1.65–7.93), P = 0.0013]. Immunohistochemistry staining suggested that high copy numbers correlated with increased protein levels. High expression of ABCC4 was an independent poor prognostic factor for ESCC [relative risk: 1.73 (1.10–2.73), P = 0.0181]. The CNV region showed strong enhancer activity. Furthermore, inhibition of ABCC4 protein in ESCC cells decreased cell proliferation and motility via the inhibition of COX-2, PGE2 receptors and c-Myc expression; AKT, extracellular signal-regulated kinase and cAMP response element-binding protein phosphorylation; and β-catenin nuclear translocation in ESCC cells. In conclusion, the CNV at 13q32.1 is associated with ESCC susceptibility, and a gene within this locus, ABCC4, activates the oncogenic pathways in ESCC and thus facilitates cancer cell development and progression. A direct genetic contribution of ESCC risk through CNV common variants was determined in this study, and ABCC4 might therefore have predictive and therapeutic potential for ESCC.

Recent genomics analysis of the high-grade serous subtype of epithelial ovarian cancer (EOC) show aberrations in the phosphatidylinositol 3-kinase (PI3K)/AKT pathway that result in upregulated signaling activity. Thus, the PI3K/AKT pathway represents a potential therapeutic target for aggressive high-grade EOC. We previously demonstrated that treatment of malignant ascites-derived primary human EOC cells and ovarian cancer cell lines with the allosteric AKT inhibitor Akti-1/2 induces a dormancy-like cytostatic response but does not reduce cell viability. In this report, we show that allosteric AKT inhibition in these cells induces cytoprotective autophagy. Inhibition of autophagy using chloroquine (CQ) alone or in combination with Akti-1/2 leads to a significant decrease in viable cell number. In fact, Akti-1/2 sensitizes EOC cells to CQ-induced cell death by exhibiting markedly reduced EC50 values in combination-treated cells compared with CQ alone. In addition, we evaluated the effects of the novel specific and potent autophagy inhibitor-1 (Spautin-1) and demonstrate that Spautin-1 inhibits autophagy in a Beclin-1-independent manner in primary EOC cells and cell lines. Multicellular EOC spheroids are highly sensitive to Akti-1/2 and CQ/Spautin-1 cotreatments, but resistant to each agent alone. Indeed, combination index analysis revealed strong synergy between Akti-1/2 and Spautin-1 when both agents were used to affect cell viability; Akti-1/2 and CQ cotreatment also displayed synergy in most samples. Taken together, we propose that combination AKT inhibition and autophagy blockade would prove efficacious to reduce residual EOC cells for supplying ovarian cancer recurrence.

There is a need for exploration of new therapeutic strategies that target distinct molecular mechanisms of castration-resistant prostate cancer (CRPC) because its emergence following androgen deprivation therapy is a major clinical problem. In this report, we investigated the role of glutathione peroxidase 2 (GPX2) in CRPC. GPX2 expression was analyzed in rat and human CRPC cells. Next, we determined the proliferation rate and level of reactive oxygen species (ROS) in GPX2-small interfering RNA (siRNA)-transfected CRPC cells. For in vivo analysis, siRNA-transfected cells were subcutaneously implanted into normal and castrated nude mice. Further, immunohistochemical and prognostic analyses of GPX2 were performed using human specimens. Silencing of GPX2 caused significant growth inhibition and increased intracellular ROS in both rat (PCai1) and human (PC3) CRPC cells. Flow cytometry and western blot analyses revealed that the decrease in proliferation rate of the GPX2-silenced cells was due to cyclin B1-dependent G2/M arrest. Furthermore, knockdown of Gpx2 inhibited tumor growth of PCai1 cells in castrated mice. Immunohistochemical analyses indicated that expression of GPX2 was significantly higher in residual cancer foci after neoadjuvant hormonal therapy than in hormone naive cancer foci. Moreover, patients with high GPX2 expression in biopsy specimen had significantly lower prostate-specific antigen recurrence-free survival and overall survival than those with no GPX2 expression. These findings suggest that GPX2 is a prognostic marker in CRPC and affects proliferation of prostate cancer under androgen depletion partially through protection against ROS signaling.

The PI3K/PTEN/Akt/mTOR/p70S6K pathway is one of the most frequently deregulated signaling pathways in solid tumors and has a functional role in drug resistance. However, targeting this pathway leads to compensatory activation of several mediators of cell survival. Expression of the reactive oxygen species-controlling kinase Mirk/dyrk1B was increased severalfold by the mammalian target of rapamycin (mTOR) inhibitors RAD001, WYE354 and rapamycin, with less effect by the Akt inhibitors AZD5363 and MK-2206. Upregulation of Mirk messenger RNA (mRNA) expression was mediated by cyclic AMP response element binding protein (CREB) binding to two sites in the Mirk promoter upstream of the transcription start site and one site within exon 4. Depletion of CREB reduced Mirk expression, whereas depletion of mTOR increased it. Moreover, hydroxytamoxifen activation of an Akt-estrogen receptor construct blocked an increase in Mirk mRNA and protein. Addition of a Mirk/dyrk1B kinase inhibitor increased the sensitivity of Panc1 pancreatic cancer cells and three different ovarian cancer cell lines to the mTOR inhibitor RAD001. Targeting Mirk kinase could improve the utility of mTOR inhibitors and so presents an attractive drug target.

p73, a structural and functional homolog of p53, plays an important role in modulating cell cycle control and apoptosis. We examined whether the p73 G4C14-to-A4T14 polymorphism was related to the risk of nasopharyngeal carcinoma (NPC) among Chinese populations. The G4C14-to-A4T14 polymorphism was genotyped in 593 NPC cases and 480 controls, and in 102 NPC trios. Logistic regression analysis and transmission/disequilibrium tests (TDT) were performed to evaluate whether there was an association between the polymorphism and NPC, respectively. Functional analyses were conducted to verify the biological relevance of the polymorphism. We observed that compared with the GC/GC genotype, the genotypes containing AT allele (GC/AT + AT/AT genotypes) were associated with significantly increased susceptibility to NPC [odds ratio (OR) = 1.51; 95% confidence interval (CI) = 1.16–1.95; P = 0.002]. Furthermore, compared with the GC/GC genotype, the GC/AT + AT/AT genotypes were significantly associated with the advanced lymph node metastasis (OR = 1.47; 95% CI = 1.02–2.11; P = 0.041). A significantly greater than expected transmission of the AT allele from heterozygous parents to offspring was also observed (P = 0.049) using the TDT. By using the TdT-mediated dUPT-biotin nick end labeling assay, we observed lower apoptosis in NPC tissues from the AT allele carriers compared with that from non-carriers. Furthermore, the relative TAp73 RNA levels of the AT allele were lower than those of the GC allele in heterozygous cells. Our findings suggest that the p73 G4C14-to-A4T14 polymorphism may play a role in mediating the susceptibility to NPC in Chinese populations.

CXCR4 is a chemokine receptor that is overexpressed in certain cancer types and involved in migration toward distant organs. The molecular mechanisms underlying CXCR4 expression in invasive cancer, particularly posttranscriptional regulation, are poorly understood. Here, we find that CXCR4 harbors AU-rich elements (AREs) in the 3'-untranslated region (3'-UTR) that bind and respond to the RNA-binding proteins, tristetraprolin (TTP/ZFP36) and HuR (ELAVL1). Different experimental approaches, including RNA immunoprecipitation, 3'-UTR reporter, RNA shift and messenger RNA (mRNA) half-life studies confirmed functionality of the CXCR4 ARE. Wild-type TTP, but not the zinc finger mutant, C124R, was able to bind CXCR4 mRNA and ARE. In the invasive breast cancer phenotype, aberrant expression of CXCR4 is linked to both TTP deficiency and HuR overexpression. HuR silencing led to decreased CXCR4 mRNA stability and expression, and significant reduction in migration of the cells toward the CXCR4 ligand, CXCL12. Derepression of TTP using miR-29a inhibitor led to significant reduction in CXCR4 mRNA stability, expression and migration capability of the cells. The study shows that CXCR4 is regulated by ARE-dependent posttranscriptional mechanisms that involve TTP and HuR, and that aberration in this pathway helps cancer cells migrate toward the CXCR4 ligand. Targeting posttranscriptional control of CXCR4 expression may constitute an alternative approach in cancer therapy.

Pleomorphic adenoma gene like-2 (PLAGL2), a member of the PLAG gene family, is a C2H2 zinc finger transcriptional factor that is involved in cellular transformation and apoptosis. In this report, we show that PLAGL2 is associated with the organization of stress fibers and with small guanosine triphosphatase (GTPase) activity. Depletion of PLAGL2 in two different ovarian cancer cell lines, ES-2 and HEY, induced activation of RhoA, whereas activity of Rac1 was suppressed. Organization of actin stress fibers and focal adhesions was significantly promoted by PLAGL2 knockdown in a RhoA-dependent manner. Conversely, exogenous expression of PLAGL2 in MDA-MB-231 cells, a breast cancer cell line, resulted in the activation of Rac1 and the inactivation of RhoA. In addition, PLAGL2 expression induced lamellipodia formation and disruption of stress fiber formation. Finally, we show that CHN1 expression is essential for Rac1 inactivation in PLAGL2-depleted cells. Our results demonstrate a crucial role of PLAGL2 in actin dynamics and give further insight into the role of PLAGL2 in cellular transformation and apoptosis.

Exposure to environmental agents and endogenous metabolism can both give rise to DNA alkylation. Thymine is known to be alkylated at O 2, N3 and O 4 positions; however, it remains poorly explored how the regioisomeric alkylated thymidine lesions compromise the flow of genetic information by perturbing DNA replication in cells. Herein, we assessed the differential recognition of the regioisomeric O 2-, N3- and O 4-ethylthymidine (O 2-, N3- and O 4-EtdT) by the DNA replication machinery of Escherichia coli cells. We found that O 4-EtdT did not inhibit appreciably DNA replication, whereas O 2- and N3-EtdT were strongly blocking to DNA replication. In addition, O 4-EtdT induced a very high frequency of T->C mutation, whereas nucleotide incorporation opposite O 2- and N3-EtdT was promiscuous. Replication experiments with the use of polymerase-deficient cells revealed that Pol V constituted the major polymerase for the mutagenic bypass of all three EtdT lesions, though Pol IV also contributed to the T->G mutation induced by O 2- and N3-EtdT. The distinct cytotoxic and mutagenic properties of the three regioisomeric lesions could be attributed to their unique chemical properties.

The spindle assembly checkpoint (SAC), which blocks anaphase onset until all chromosomes have bi-oriented, is one of the key self-monitoring systems of the eukaryotic cell cycle for genome stability. The mitotic arrest-deficient protein 1 (Mad1), a critical component of the SAC, is hyperphosphorylated in mitosis. However, the kinases responsible for Mad1 phosphorylation and its functional significance are not fully understood. Here we report that Mad1 is phosphorylated on Serine 214 by the Ataxia-Telangiectasia Mutated (ATM) kinase, a critical DNA damage response protein also activated in mitosis and required for the SAC. We demonstrate that Mad1 Serine 214 phosphorylation promotes the formation of homodimerization of Mad1 and its heterodimerization with Mad2. Further we show that Mad1 Serine 214 phosphorylation contribute to activation of the SAC and the maintenance of chromosomal stability. Together, these findings reveal an important role of ATM-mediated Mad1 Serine 214 phosphorylation in mitosis.

Sodium–hydrogen exchanger isoform 1 (NHE1) plays a role in survival and migration/invasion of several cancers and is an emerging new therapeutic target. However, the role of NHE1 in glioblastoma and the interaction of NHE1 expression and function in glioblastoma cells with cytotoxic temozolomide (TMZ) therapy remain unknown. In this study, we detected high levels of NHE1 protein only in primary human glioma cells (GC), glioma xenografts and glioblastoma, but not in human neural stem cells or astrocytes. GC exhibited an alkaline resting pHi (7.46±0.04) maintained by robust NHE1-mediated H+ extrusion. GC treatment with TMZ for 2–24h triggered a transient decrease in pHi, which recovered by 48h and correlated with concurrent upregulation of NHE1 protein expression. NHE1 protein was colocalized with ezrin at lamellipodia and probably involved in GC migration. The TMZ-treated GC exhibited increased migration and invasion, which was attenuated by addition of NHE1 inhibitor HOE-642. Most importantly, NHE1 inhibition prevented prosurvival extracellular signal-regulated kinase activation and accelerated TMZ-induced apoptosis. Taken together, our study provides the first evidence that GC upregulate NHE1 protein to maintain alkaline pHi. Combining TMZ therapy with NHE1 inhibition suppresses GC migration and invasion, and also augments TMZ-induced apoptosis. These findings strongly suggest that NHE1 is an important cytoprotective mechanism in GC and presents a new therapeutic strategy of combining NHE1 inhibition and TMZ chemotherapy.

Genome-wide association studies (GWAS) in colorectal cancer (CRC) identified five regions near transforming growth factor β-related genes BMP4, GREM1, CDH1, SMAD7 and RPHN2. The true risk alleles remain to be identified in these regions, and their role in CRC risk in non-European populations has been understudied. Our previous work noted significant genetic heterogeneity between African Americans (AAs) and European Americans (EAs) for single nucleotide polymorphisms (SNPs) identified in GWAS. We hypothesized that associations may not have been replicated in AAs due to differential or independent genetic structures. In order to test this hypothesis, we genotyped 195 tagging SNPs across these five gene regions in 1194 CRC cases (795 AAs and 399 EAs) and 1352 controls (985 AAs and 367 EAs). Imputation was performed, and association testing of genotyped and imputed SNPs included ancestry, age and sex as covariates. In two of the five genes originally associated with CRC, we found evidence for association in AAs including rs1862748 in CDH1 (ORAdd = 0.82, P = 0.02) and in GREM1 the SNPs rs10318 (ORRec = 60.1, P = 0.01), rs11632715 (ORRec = 2.36; P = 0.004) and rs12902616 (ORRec = 1.28, P = 0.005), the latter which is in linkage disequilibrium with the previously identified SNP rs4779584. Testing more broadly for associations in these gene regions in AAs, we noted three statistically significant association peaks in GREM1 and RHPN2 that were not identified in EAs. We conclude that some CRC risk alleles are shared between EAs and AAs and others are population specific.

Functional genetic variants of DNA repair genes may alter the host DNA repair capacity, and thus influence efficiency of therapies. We genotyped eight potentially functional single nucleotide polymorphisms (SNPs) in genes (i.e. ERCC1, XPA, XPC, XPD and XPG) involved in the nucleotide excision repair (NER) pathway in 496 Japanese gastric cancer patients, and assessed overall survival and recurrence-free survival. The combined effects of risk genotypes of these eight SNPs in Japanese patients were further replicated in 356 North-American gastric cancer patients. In Japanese patients, we found that the XPC rs2228000 TT genotype was associated with shorter overall survival [hazards ratio (HR) = 1.75, 95% confidence interval (95% CI) = 1.07–2.86] and recurrence-free survival (HR = 2.17, 95% CI = 1.19–3.95), compared with CC/CT genotypes, and the XPG rs17655 CC genotype was associated with shorter overall survival (HR = 1.60, 95% CI = 1.08–2.36), compared with GG/CG genotypes. The number of observed risk genotypes in the combined analysis was associated with shorter overall survival and recurrence-free survival in a dose–response manner (P trend = 0.006 and P trend < 0.000) in Japanese patients; specifically, compared with those with ≤1 risk genotypes, those with ≥2 risk genotypes showed markedly shorter overall survival (HR = 1.79, 95% CI = 1.18–2.70) and recurrence-free survival (HR = 2.80, 95% CI = 1.66–4.73). The association between ≥2 risk genotypes and shorter overall survival was not significant (HR = 1.26, 95% CI = 0.82–1.94) in North-American patients, but the trends were similar in these two groups of patients. These data show that functional SNPs in NER core genes may impact survival in Japanese gastric cancer patients.

In this study, we aim to identify the genes responsible for colorectal cancer risk behind the loci identified in genome-wide association studies (GWAS). These genes may be candidate targets for developing new strategies for prevention or therapy. We analyzed the association of genotypes for 26 GWAS single nucleotide polymorphisms (SNPs) with the expression of genes within a 2 Mb region (cis-eQTLs). Affymetrix Human Genome U219 expression arrays were used to assess gene expression in two series of samples, one of healthy colonic mucosa (n = 47) and other of normal mucosa adjacent to colon cancer (n = 97, total 144). Paired tumor tissues (n = 97) were also analyzed but did not provide additional findings. Partial Pearson correlation (r), adjusted for sample type, was used for the analysis. We have found Bonferroni-significant cis-eQTLs in three loci: rs3802842 in 11q23.1 associated to C11orf53, COLCA1 (C11orf92) and COLCA2 (C11orf93; r = 0.60); rs7136702 in 12q13.12 associated to DIP2B (r = 0.63) and rs5934683 in Xp22.3 associated to SHROOM2 and GPR143 (r = 0.47). For loci in chromosomes 11 and 12, we have found other SNPs in linkage disequilibrium that are more strongly associated with the expression of the identified genes and are better functional candidates: rs7130173 for 11q23.1 (r = 0.66) and rs61927768 for 12q13.12 (r = 0.86). These SNPs are located in DNA regions that may harbor enhancers or transcription factor binding sites. The analysis of trans-eQTLs has identified additional genes in these loci that may have common regulatory mechanisms as shown by the analysis of protein–protein interaction networks.

In this case-cohort study, we examined the association between bulky DNA adducts and the risk of lung cancer within the European Prospective Investigation into Cancer and Nutrition (EPIC) Spanish cohort with an average 7-year follow-up, including 98 cases of primary lung cancer and 296 subjects randomly selected from the cohort. Aromatic adducts were measured using 32P-postlabeling in leukocyte DNA from blood samples collected at enrollment. The association between DNA adducts and the risk of lung cancer was estimated using a Cox proportional hazards model with a modified partial likelihood. There was an overall significant increased risk for developing lung cancer when DNA adduct concentrations were doubled, with relative risk (RR) adjusting for all relevant confounders of 1.36 with 95% confidence interval (CI) 1.18–157. There was a significant increased risk for developing lung cancer when DNA adduct concentrations were doubled for current smokers and among subjects exposed to PAH at work; there was also a slightly higher increase among males than females. However, no statistically significant differences were observed for the effect of adduct levels across smoking status, sex or occupational exposure to PAH. A meta-analysis combined four prospective studies, including this study, resulting in a significant association among current smokers, with an overall estimate of 34% increase in the risk of lung cancer when doubling the level of aromatic DNA adducts in leukocytes.

DNA adducts are a measure of internal exposure to genotoxicants. However, the measurement of DNA adducts in molecular epidemiology studies often is precluded by the lack of fresh tissue. In contrast, formalin-fixed paraffin-embedded (FFPE) tissues frequently are accessible, although technical challenges remain in retrieval of high quality DNA suitable for biomonitoring of adducts. Aristolochic acids (AA) are human carcinogens found in Aristolochia plants, some of which have been used in the preparation of traditional Chinese herbal medicines. We previously established a method to measure DNA adducts of AA in FFPE tissue. In this study, we examine additional features of formalin fixation that could impact the quantity and quality of DNA and report on the recovery of AA-DNA adducts in mice exposed to AA. The yield of DNA isolated from tissues fixed with formalin decreased over 1 week; however, the levels of AA-DNA adducts were similar to those in fresh frozen tissue. Moreover, DNA from FFPE tissue served as a template for PCR amplification, yielding sequence data of comparable quality to DNA obtained from fresh frozen tissue. The estimates of AA-DNA adducts measured in freshly frozen tissue and matching FFPE tissue blocks of human kidney stored for 9 years showed good concordance. Thus, DNA isolated from FFPE tissues may be used to biomonitor DNA adducts and to amplify genes used for mutational analysis, providing clues regarding the origin of human cancers for which an environmental cause is suspected.

Long noncoding RNA (lncRNA) HOX transcript antisense RNA (HOTAIR), which could induce genome-wide retargeting of polycomb-repressive complex 2, trimethylates histone H3 lysine-27 (H3K27me3) and deregulation of multiple downstream genes, is involved in development and progression of esophageal squamous cell carcinoma (ESCC). We hypothesized that the functional single nucleotide polymorphisms (SNP) in HOTAIR may affect HOTAIR expression and/or its function and, thus, ESCC risk. Therefore, we examined the association between three haplotype-tagging SNPs (htSNP) across the whole HOTAIR locus and ESCC risk as well as the functional relevance of an ESCC susceptibility SNP rs920778. Genotypes were determined in three independent case–control sets consisted of 2098 ESCC patients and 2150 controls. The allele-specific regulation on HOTAIR expression by the rs920778 SNP was investigated in vitro and in vivo. We found that the HOTAIR rs920778 TT carriers had a 1.37-fold, 1.78-fold and 2.08-fold increased ESCC risk in Jinan, Shijiazhuang and Huaian populations, respectively, compared with the CC carriers (P = 0.003, 7.7 x 10–4 and 5.9 x 10–4). During inspecting functional relevance of the rs920778 SNP, we identified a novel intronic HOTAIR enhancer locating between +1719bp and +2353bp from the transcriptional start site through reporter assays. Moreover, there is an allelic regulation of rs920778 on HOTAIR expression via this enhancer in both ESCC cell lines and normal esophageal tissue specimens, with higher HOTAIR expression among T allele carriers. These results demonstrate that functional genetic variants influencing lncRNA regulation may explain a fraction of ESCC genetic basis.

Genome-wide association studies (GWAS) have identified a large number of cancer-associated single nucleotide polymorphisms (SNPs), several of which have been associated with multiple cancer sites suggesting pleiotropic effects and shared biological mechanisms across some cancers. We hypothesized that SNPs associated with other cancers may be additionally associated with endometrial cancer. We examined 213 SNPs previously associated with 14 other cancers for their associations with endometrial cancer in 3758 endometrial cancer cases and 5966 controls of European ancestry from two consortia: Population Architecture Using Genomics and Epidemiology and the Epidemiology of Endometrial Cancer Consortium. Study-specific logistic regression estimates adjusted for age, body mass index and the most significant principal components of genetic ancestry were combined using fixed-effect meta-analysis to evaluate the association between each SNP and endometrial cancer risk. A Bonferroni-corrected P value of 2.35x10–4 was used to determine statistical significance of the associations. SNP rs7679673, ~6.3kb upstream of TET2 and previously reported to be associated with prostate cancer risk, was associated with endometrial cancer risk in the direction opposite to that for prostate cancer [meta-analysis odds ratio = 0.87 (per copy of the C allele), 95% confidence interval = 0.81, 0.93; P = 7.37x10–5] with no evidence of heterogeneity across studies (P heterogeneity = 0.66). This pleiotropic analysis is the first to suggest TET2 as a susceptibility locus for endometrial cancer.

Aberrant expression of subgroup k human endogenous retroviruses (HERV-K) has been observed in prostate cancer. This subgroup is unique because it encodes sequences in the human genome containing open reading frames for near intact retroviruses. We hypothesized that HERV-K reactivation could serve as a non-invasive early disease detection marker for prostate cancer. We evaluated HERV-K gag messenger RNA (mRNA) expression in blood samples of African-American and European-American men using a case–control design via quantitative real-time PCR. Additionally, we examined HERV-K envelope protein expression in prostate tumors by immunohistochemistry. HERV-K envelope protein was commonly upregulated in prostate tumors, but more so in tumors of African-American than European-American patients (61% versus 40%, P < 0.01). Examining HERV-K gag expression in peripheral blood mononuclear cells (PBMC) from 294 cases and 135 healthy men, we found that the abundance of HERV-K gag message was significantly higher in cases than controls and was associated with increased plasma interferon-. Men with gag expression in the highest quartile had >12-fold increased odds {odds ratio = 12.87 [95% confidence interval 6.3–26.25]} of being diagnosed with prostate cancer than those in the lowest quartile. Moreover, our results showed that HERV-K expression may perform better as a disease biomarker in older than younger men (whereas the sensitivity of prostate-specific antigen (PSA) testing decreases with age) and in men with a smoking history compared with never smokers. Combining non-invasive HERV-K testing with PSA testing may improve the efficacy of prostate cancer detection specifically among older men and smokers who tend to develop a more aggressive disease.

A large number of genetic associations with cervical cancer have been reported in hypothesis-driven candidate gene studies, but most studies have not included an independent replication or the results have been inconsistent between studies. In order to independently validate these associations, we reexamined 58 candidate gene/regions previously reported to be associated with cervical cancer using the gene-based Adaptive Rank Truncated Product test in a genome-wide association study (GWAS) of 1034 cervical cancer patients and 3948 controls from the Swedish population. Of the 58 gene/regions, 8 had a nominal P value < 0.05 [tumor necrosis factor (TNF), P = 5.0 x 10 4; DEAD (Asp-Glu-Ala-Asp) box helicase 1 [DDX1], P = 2.2 x 10 3; exonuclease 1 [EXO1], P = 4.7 x 10 3; excision repair cross-complementing rodent repair deficiency, complementation group 1 [ERCC1], P = 0.020; transmembrane channel-like 6 and 8 genes [TMC6-TMC8], P = 0.023; secreted phosphoprotein 1 [SPP1], P = 0.028; v-erb-b2 avian erythroblastic leukemia viral oncogene homolog 2 [ERBB2], P = 0.033 and chloride channel, voltage-sensitive 7 [CLCN7], P = 0.047). After correction for multiple testing, only TNF remained statistically significant (P = 0.028). Two single-nucleotide polymorphisms that are in nearly perfect linkage disequilibrium (rs2857602 and rs2844484) contributed most to the association with TNF. However, they are not independent from the previously reported associations within the MHC region. The very low number of previously reported associations with cervical cancer that replicate in the Swedish population underscore the need to apply more stringent criteria when reporting associations, including the prerequisite of replicating the association as part of the original study.

Metabolomic analysis of feces may provide insights on colorectal cancer (CRC) if assay performance is satisfactory. In lyophilized feces from 48 CRC cases, 102 matched controls, and 48 masked quality control specimens, 1043 small molecules were detected with a commercial platform. Assay reproducibility was good for 527 metabolites [technical intraclass correlation coefficient (ICC) >0.7 in quality control specimens], but reproducibility in 6-month paired specimens was lower for the majority of metabolites (within-subject ICC ≤0.5). In the CRC cases and controls, significant differences (false discovery rate ≤0.10) were found for 41 of 1043 fecal metabolites. Direct cancer association was found with three fecal heme-related molecules [covariate-adjusted 90th versus 10th percentile odds ratio (OR) = 17–345], 18 peptides/amino acids (OR = 3–14), palmitoyl-sphingomyelin (OR = 14), mandelate (OR = 3) and p-hydroxy-benzaldehyde (OR = 4). Conversely, cancer association was inverse with acetaminophen metabolites (OR <0.1), tocopherols (OR = 0.3), sitostanol (OR = 0.2), 3-dehydrocarnitine (OR = 0.4), pterin (OR = 0.3), conjugated-linoleate-18-2N7 (OR = 0.2), N-2-furoyl-glycine (OR = 0.3) and p-aminobenzoate (PABA, OR = 0.2). Correlations suggested an independent role for palmitoyl-sphingomyelin and a central role for PABA (which was stable over 6 months, within-subject ICC 0.67) modulated by p-hydroxy-benzaldehyde. Power calculations based on ICCs indicate that only 45% of metabolites with a true relative risk 5.0 would be found in prospectively collected, prediagnostic specimens from 500 cases and 500 controls. Thus, because fecal metabolites vary over time, very large studies will be needed to reliably detect associations of many metabolites that potentially contribute to CRC.

Although genetic studies have reported a number of loci associated with melanoma risk, the complex genetic architecture of the disease is not yet fully understood. We sought to identify common genetic variants associated with melanoma risk in a genome-wide association study (GWAS) of 2298 cases and 6654 controls. Thirteen of 15 known loci were replicated with nominal significance. A total of 69 single-nucleotide polymorphisms (SNPs) were selected for in silico replication in two independent melanoma GWAS datasets (a total of 5149 cases and 12 795 controls). Seven novel loci were nominally significantly associated with melanoma risk. These seven SNPs were further genotyped in 234 melanoma cases and 238 controls. The SNP rs4698934 was nominally significantly associated with melanoma risk. The combined odds ratio per T allele = 1.18; 95% confidence interval (1.10–1.25); combined P = 7.70 x 10 7. This SNP is located in the intron of the TET2 gene on chromosome 4q24. In addition, a novel somatic mutation of TET2 was identified by next-generation sequencing in 1 of 22 sporadic melanoma cases. TET2 encodes a member of TET family enzymes that oxidizes 5-methylcytosine to 5-hydroxymethylcytosine (5hmC). It is a putative epigenetic biomarker of melanoma as we previously reported, with observation of reduced TET2 transcriptional expression. This study is the first to implicate TET2 genetic variation and mutation in melanoma.

Many adult chronic diseases are thought to be influenced during early life by maternal nutrition; however, the underlying mechanisms remain largely unknown. Obesity-related diseases may be due partly to high fat consumption. Herein, we evaluated mammary tumor risk in female mouse mammary tumor virus-Wnt-1 transgenic (Tg) offspring exposed to high-fat diet (HFD) or control diet (CD) (45% and 17% kcal from fat, respectively) during gestation and lactation, with CD provided to progeny at weaning. In Tg offspring, maternal HFD exposure increased mammary tumor incidence and decreased tumor latency without affecting tumor volume. Tumor risk was associated with higher tumor necrosis factor-α and insulin and altered oxidative stress biomarkers in sera and with early changes in mammary expression of genes linked to tumor promotion [interleukin 6 (Il6)] or inhibition [phosphatase and tensin homolog deleted on chromosome 10 (Pten), B-cell lymphoma 2 (Bcl2)]. Corresponding wild-type progeny exposed to maternal HFD displayed accelerated mammary development, higher mammary adiposity, increased insulin resistance and early changes in Pten, Bcl2 and Il6, than CD-exposed offspring. Dams-fed HFD showed higher serum glucose and oxidative stress biomarkers but comparable adiposity compared with CD-fed counterparts. In human breast cancer MCF-7 cells, sera from maternal HFD-exposed Tg offspring elicited changes in PTEN, BCL2 and IL6 gene expression, mimicking in vivo exposure; increased cell viability and mammosphere formation and induced measures [insulin receptor substrate-1 (IRS-1), IRS-2] of insulin sensitivity. Serum effects on IRS-1 were recapitulated by exogenous insulin and the PTEN-specific inhibitor SF1670. Hyperinsulinemia and PTEN loss-of-function may thus, couple maternal HFD exposure to enhanced insulin sensitivity via increased mammary IRS-1 expression in progeny, to promote breast cancer risk.

The objective of this study was to analyze the expression, biological role and clinical relevance of exosomal microRNAs (miRNAs) from ovarian carcinoma (OC) effusion supernatants. Exosomal miRNA expression profiling was performed using miRNA Taqman arrays. Selected miRNAs were validated using quantitative PCR in 86 OC effusion supernatants. The role of exosomal miRNA in this cancer was further studied using in vitro and in vivo models. miRNA profiling identified 99 miRNAs with high expression levels in exosomes from OC effusion supernatants. Quantitative PCR validation of 11 miRNAs showed significant associations with effusion site (peritoneum versus pleura) and International Federation of Gynecology and Obstetrics stage. In univariate survival analysis, high levels of miRNAs 21, 23b and 29a were associated with poor progression-free survival (P = 0.01, P = 0.015 and P = 0.009, respectively), whereas high expression of miRNA 21 correlated with poor overall survival (P = 0.017). The latter association was retained in Cox multivariate analysis (P = 0.001). Exposure of LP9 mesothelial cells and ES2 OC cells to OC effusion-derived exosomes inhibited tumor spheroid expansion and reduced mesothelial clearance area. Treatment of severe combined immunodeficiency mice with exosomes from OC effusions prior to injection of tumor cells was associated with larger tumor load, more infiltrative tumors and shorter survival. Patient-derived OC effusion exosomes contain multiple miRNAs, of which some may have clinical relevance. In experimental models, OC exosomes affect both tumor cells and cells in the tumor microenvironment and induce more aggressive disease. Collectively, these data demonstrate the central role of miRNAs and their content in the biology of this cancer.

Although use of non-steroidal anti-inflammatory drugs (NSAIDs) generally decreases colorectal cancer (CRC) risk, inherited genetic variation in inflammatory pathways may alter their potential as preventive agents. We investigated whether variation in prostaglandin synthesis and related pathways influences CRC risk in the Colon Cancer Family Registry by examining associations between 192 single nucleotide polymorphisms (SNPs) and two variable nucleotide tandem repeats (VNTRs) within 17 candidate genes and CRC risk. We further assessed interactions between these polymorphisms and NSAID use on CRC risk. Using a case-unaffected-sibling-control design, this study included 1621 primary invasive CRC cases and 2592 sibling controls among Caucasian men and women aged 18–90. After adjustment for multiple comparisons, two intronic SNPs were associated with rectal cancer risk: rs11571364 in ALOX12 [ORhet/hzv = 1.87, 95% confidence interval (CI) = 1.19–2.95, P = 0.03] and rs45525634 in PTGER2 (ORhet/hzv = 0.49, 95% CI = 0.29–0.82, P = 0.03). Additionally, there was an interaction between NSAID use and the intronic SNP rs2920421 in ALOX12 on risk of CRC (P = 0.03); among those with heterozygous genotypes, risk was reduced for current NSAID users compared with never or former users (ORhet = 0.60, 95% CI = 0.45–0.80), though not among those with homozygous wild-type or variant genotypes. The results of this study suggest that genetic variation in ALOX12 and PTGER2 may affect the risk of rectal cancer. In addition, this study suggests plausible interactions between NSAID use and variants in ALOX12 on CRC risk. These results may aid in the development of genetically targeted cancer prevention strategies with NSAIDs.

Hepatitis B virus surface antigen (HBsAg) is an important risk factor for hepatocellular carcinoma (HCC) and is downregulated during hepatocarcinogenesis. MicroRNAs (miRNAs) are frequently deregulated in HCC tissues. However, whether the deregulation of certain miRNAs in HCC has an impact on HBsAg expression remains unclear. We found here that microRNA-581 (miR-581), which is deregulated during hepatocarcinogenesis, promoted HBsAg expression. Additionally, miR-581 targeted Dicer and endoplasmic reticulum degradation-enhancing alpha-mannosidase-like protein 1 (EDEM1) and repressed their expression. Although Dicer cannot process HBV transcripts, Dicer knockdown led to increased HBsAg secretion, most likely due to a reduction in the levels of Dicer-processed 7SL RNA fragments. Moreover, Dicer-processed 7SL RNA fragments partially inhibited the ability of miR-581 to stimulate HBsAg expression. Furthermore, we found that forced EDEM1 expression inhibited miR-581-mediated induction of HBsAg. Finally, transfection of miR-581 into HepG2.2.15 cells promoted cell proliferation and led to upregulation of genes involved in development, cell proliferation and protein secretion. Altogether, we conclude that miR-581 promotes HBsAg expression by targeting Dicer and EDEM1. Our findings suggest that downregulation of miR-581 during hepatocarcinogenesis may lead to a reduction in HBsAg expression and impede HCC development.

Leptin, secreted by the adipose tissue and known to be related to obesity, is considered to be involved in the onset and progression of colorectal cancer. However, the exact role of leptin in colorectal carcinogenesis is still unclear, as several controversial reports have been published on the various systemic effects of leptin. The aim of this study was to clarify the local and precise roles of leptin receptor (LEPR)-mediated signaling in colonic carcinogenesis using intestinal epithelium-specific LEPRb conditional knockout (cKO) mice. We produced and used colonic epithelium-specific LEPRb cKO mice to investigate the carcinogen-induced formation of aberrant crypt foci (ACF) and tumors in the colon, using their littermates as control. There were no differences in the body weight or systemic condition between the control and cKO mice. The tumor sizes and number of large-sized tumors were significantly lower in the cKO mice as compared with those in the control mice. On the other hand, there was no significant difference in the proliferative activity of the normal colonic epithelial cells or ACF formation between the control and cKO mice. In the control mice, marked increase of the LEPRb expression level was observed in the colonic tumors as compared with that in the normal epithelium; furthermore, signal transducer and activator of transcription (STAT3) was activated in the tumor cells. These findings suggest that STAT3 is one of the important molecules downstream of LEPRb, and LEPRb/STAT3 signaling controls tumor cell proliferation. We demonstrated the importance of local/regional LEPR-mediated signaling in colorectal carcinogenesis.

Castration-resistant prostate cancer is an incurable heterogeneous disease that is characterized by a complex multistep process involving different cellular and biochemical changes brought on by genetic and epigenetic alterations. These changes lead to the activation or overexpression of key survival pathways that also serve as potential therapeutic targets. Despite promising preclinical results, molecular targeted therapies aimed at such signaling pathways have so far been dismal. In the present study, we used a PTEN-deficient mouse model of prostate cancer to show that plasticity in castration-resistant tumors promotes therapeutic escape. Unlike castration-naïve tumors which depend on androgen receptor and PI3K/AKT signal activation for growth and survival, castration-resistant tumors undergo phenotypic plasticity leading to increased intratumoral heterogeneity. These tumors attain highly heterogeneous phenotypes that are characterized by cancer cells relying on alternate signal transduction pathways for growth and survival, such as mitogen-activated protein kinase and janus kinase/signal transducer and activator of transcription, and losing their dependence on PI3K signaling. These features thus enabled castration-resistant tumors to become insensitive to the therapeutic effects of PI3K/AKT targeted therapy. Overall, our findings provide evidence that androgen deprivation drives phenotypic plasticity in prostate cancer cells and implicate it as a crucial contributor to therapeutic resistance in castration-resistant prostate cancer. Therefore, incorporating intratumoral heterogeneity in a dynamic tumor model as a part of preclinical efficacy determination could improve prediction for response and provide better rationale for the development of more effective therapies.