For almost two decades, breast cancer clinical genetics has operated in an environment where a heritable cause of breast cancer susceptibility is identified in the vast minority of women seeking advice about their personal and/or family history of breast and/or ovarian cancer. A new wave of genetic information is upon us that promises to provide an explanation for the greater proportion of current missing heritability of breast cancer. Whilst researchers refine bioinformatic and analytic methodology necessary to interpret the new genetic data, attention needs to be paid to defining appropriate and coordinated pathways for the translation of this information so that it can be applied in clinical genetic services for the benefit of the majority of women who currently have no explanation for their breast cancer susceptibility. The search for additional breast cancer susceptibility genes remains a very active area of research. Exhausting the power of linkage studies that identified BRCA1 and BRCA2, the research community moved to candidate gene studies that led to the identification of ATM, BRIP1, CHEK2, and PALB2 as so-called "moderate-risk" breast cancer susceptibility genes. Mutations in these genes are rare and although early reports suggested that, on average, they are associated with moderate risks of breast cancer; population-based studies have demonstrated that at least some mutations in these genes are associated with breast cancer risks that are comparable to the average risk associated with BRCA2 mutations. The search for additional breast cancer susceptibility genes has now moved onto research platforms applying massively parallel sequencing capable of sequencing whole human exomes and genomes in single instrument runs. These programs are identifying a large number of additional putative breast cancer susceptibility genes, many of which are currently undergoing validation. It is highly anticipated that the remaining missing heritability of breast cancer will be due to mutations in many different genes, each explaining a small proportion of the currently unexplained heritable breast cancer susceptibility. The characterization of PALB2 as a breast cancer susceptibility gene and subsequent research that has refined our understanding of the prevalence and penetrance of heritable mutations in PALB2 offers a precious opportunity to use the data as a model and develop modes of translation that would be appropriate for the anticipated volume of imminent new information.

There remains debate about whether risk-reducing salpingo-oophorectomy (RRSO), which reduces ovarian cancer risk, also reduces breast cancer risk. We examined the association between RRSO and breast cancer risk using a prospective cohort of 17 917 women unaffected with breast cancer at baseline (7.2% known carriers of BRCA1 or BRCA2 mutations). During a median follow-up of 10.7 years, 1046 women were diagnosed with incident breast cancer. Modeling RRSO as a time-varying exposure, there was no association with breast cancer risk overall (hazard ratio [HR] = 1.04, 95% confidence interval [CI] = 0.87 to 1.24) or by tertiles of predicted absolute risk based on family history (HR = 0.68, 95% CI = 0.32 to 1.47, HR = 0.94, 95% CI = 0.70 to 1.26, and HR = 1.10, 95% CI = 0.88 to 1.39, for lowest, middle, and highest tertile of risk, respectively) or for BRCA1 and BRCA2 mutation carriers when examined separately. There was also no association after accounting for hormone therapy use after RRSO. These findings suggest that RRSO should not be considered efficacious for reducing breast cancer risk.

Physical activity has been associated with lower risks of breast and colorectal cancer in epidemiological studies; however, it is unknown if these associations are causal or confounded. In two-sample Mendelian randomisation analyses, using summary genetic data from the UK Biobank and GWA consortia, we found that a one standard deviation increment in average acceleration was associated with lower risks of breast cancer (odds ratio [OR]: 0.51, 95% confidence interval [CI]: 0.27 to 0.98, P-value = 0.04) and colorectal cancer (OR: 0.66, 95% CI: 0.48 to 0.90, P-value = 0.01). We found similar magnitude inverse associations for estrogen positive (ER+ve) breast cancer and for colon cancer. Our results support a potentially causal relationship between higher physical activity levels and lower risks of breast cancer and colorectal cancer. Based on these data, the promotion of physical activity is probably an effective strategy in the primary prevention of these commonly diagnosed cancers.

The HMG-box transcription factor Sox9 is expressed in the intestinal epithelium, specifically, in stem/progenitor cells and in Paneth cells. Sox9 expression requires an active beta-catenin-Tcf complex, the transcriptional effector of the Wnt pathway. This pathway is critical for numerous aspects of the intestinal epithelium physiopathology, but processes that specify the cell response to such multipotential signals still remain to be identified. We inactivated the Sox9 gene in the intestinal epithelium to analyze its physiological function. Sox9 inactivation affected differentiation throughout the intestinal epithelium, with a disappearance of Paneth cells and a decrease of the goblet cell lineage. Additionally, the morphology of the colon epithelium was severely altered. We detected general hyperplasia and local crypt dysplasia in the intestine, and Wnt pathway target genes were up-regulated. These results highlight the central position of Sox9 as both a transcriptional target and a regulator of the Wnt pathway in the regulation of intestinal epithelium homeostasis.

BACKGROUND: Analysis of 23 published transcriptome studies allowed us to identify nine genes displaying frequent alterations in HNSCC (FN1, MMP1, PLAU, SPARC, IL1RN, KRT4, KRT13, MAL, and TGM3). We aimed to independently confirm these dysregulations and to identify potential relationships with clinical data for diagnostic, staging and prognostic purposes either at the tissue level or in saliva rinse. METHODS: For a period of two years, we systematically collected tumor tissue, normal matched mucosa and saliva of patients diagnosed with primary untreated HNSCC. Expression levels of the nine genes of interest were measured by RT-qPCR in tumor and healthy matched mucosa from 46 patients. MMP1 expression level was measured by RT-qPCR in the salivary rinse of 51 HNSCC patients and 18 control cases. RESULTS: Dysregulation of the nine genes was confirmed by the Wilcoxon test. IL1RN, MAL and MMP1 were the most efficient diagnostic markers of HNSCC, with ROC AUC > 0.95 and both sensitivity and specificity above 91%. No clinically relevant correlation was found between gene expression level in tumor and T stage, N stage, tumor grade, global survival or disease-free survival. Our preliminary results suggests that with 100% specificity, MMP1 detection in saliva rinse is potentially useful for non invasive diagnosis of HNSCC of the oral cavity or oropharynx, but technical improvement is needed since sensitivity was only 20%. CONCLUSION: IL1RN, MAL and MMP1 are prospective tumor diagnostic markers for HNSCC. MMP1 overexpression is the most promising marker, and its detection could help identify tumor cells in tissue or saliva.

Cancer stem cells (CSC) are responsible for cancer chemoresistance and metastasis formation. Here we report that Δ133p53β, a TP53 splice variant, enhanced cancer cell stemness in MCF-7 breast cancer cells, while its depletion reduced it. Δ133p53β stimulated the expression of the key pluripotency factors SOX2, OCT3/4, and NANOG. Similarly, in highly metastatic breast cancer cells, aggressiveness was coupled with enhanced CSC potential and Δ133p53β expression. Like in MCF-7 cells, SOX2, OCT3/4, and NANOG expression were positively regulated by Δ133p53β in these cells. Finally, treatment of MCF-7 cells with etoposide, a cytotoxic anti-cancer drug, increased CSC formation and SOX2, OCT3/4, and NANOG expression via Δ133p53, thus potentially increasing the risk of cancer recurrence. Our findings show that Δ133p53β supports CSC potential. Moreover, they indicate that the TP53 gene, which is considered a major tumor suppressor gene, also acts as an oncogene via the Δ133p53β isoform.

Cyclin-dependent kinase 4/6 (CDK4/6) inhibitors are an established treatment in estrogen receptor-positive breast cancer and are currently in clinical development in melanoma, a tumor that exhibits high rates of CDK4 activation. We analyzed melanoma cells with acquired resistance to the CDK4/6 inhibitor palbociclib and demonstrate that the activity of PRMT5, a protein arginine methyltransferase and indirect target of CDK4, is essential for CDK4/6 inhibitor sensitivity. By indirectly suppressing PRMT5 activity, palbociclib alters the pre-mRNA splicing of MDM4, a negative regulator of p53, leading to decreased MDM4 protein expression and subsequent p53 activation. In turn, p53 induces p21, leading to inhibition of CDK2, the main kinase substituting for CDK4/6 and a key driver of resistance to palbociclib. Loss of the ability of palbociclib to regulate the PRMT5-MDM4 axis leads to resistance. Importantly, combining palbociclib with the PRMT5 inhibitor GSK3326595 enhances the efficacy of palbociclib in treating naive and resistant models and also delays the emergence of resistance. Our studies have uncovered a mechanism of action of CDK4/6 inhibitors in regulating the MDM4 oncogene and the tumor suppressor, p53. Furthermore, we have established that palbociclib inhibition of the PRMT5-MDM4 axis is essential for robust melanoma cell sensitivity and provide preclinical evidence that coinhibition of CDK4/6 and PRMT5 is an effective and well-tolerated therapeutic strategy. Overall, our data provide a strong rationale for further investigation of novel combinations of CDK4/6 and PRMT5 inhibitors, not only in melanoma but other tumor types, including breast, pancreatic, and esophageal carcinoma.

BACKGROUND: Chronic inflammation is a risk factor for colorectal cancer (CRC). Circulating C-reactive protein (CRP) is also moderately associated with CRC risk. However, observational studies are susceptible to unmeasured confounding or reverse causality. Using genetic risk variants as instrumental variables, we investigated the causal relationship between genetically elevated CRP concentration and CRC risk, using a Mendelian randomization approach. METHODS: Individual-level data from 30 480 CRC cases and 22 844 controls from 33 participating studies in three international consortia were used: the Genetics and Epidemiology of Colorectal Cancer Consortium (GECCO), the Colorectal Transdisciplinary Study (CORECT) and the Colon Cancer Family Registry (CCFR). As instrumental variables, we included 19 single nucleotide polymorphisms (SNPs) previously associated with CRP concentration. The SNP-CRC associations were estimated using a logistic regression model adjusted for age, sex, principal components and genotyping phases. An inverse-variance weighted method was applied to estimate the causal effect of CRP on CRC risk. RESULTS: Among the 19 CRP-associated SNPs, rs1260326 and rs6734238 were significantly associated with CRC risk (P = 7.5 × 10-4, and P = 0.003, respectively). A genetically predicted one-unit increase in the log-transformed CRP concentrations (mg/l) was not associated with increased risk of CRC [odds ratio (OR) = 1.04; 95% confidence interval (CI): 0.97, 1.12; P = 0.256). No evidence of association was observed in subgroup analyses stratified by other risk factors. CONCLUSIONS: In spite of adequate statistical power to detect moderate association, we found genetically elevated CRP concentration was not associated with increased risk of CRC among individuals of European ancestry. Our findings suggested that circulating CRP is unlikely to be a causal factor in CRC development.

OBJECTIVE: To provide an understanding of the role of common genetic variations in colorectal cancer (CRC) risk, we report an updated field synopsis and comprehensive assessment of evidence to catalogue all genetic markers for CRC (CRCgene2). DESIGN: We included 869 publications after parallel literature review and extracted data for 1063 polymorphisms in 303 different genes. Meta-analyses were performed for 308 single nucleotide polymorphisms (SNPs) in 158 different genes with at least three independent studies available for analysis. Scottish, Canadian and Spanish data from genome-wide association studies (GWASs) were incorporated for the meta-analyses of 132 SNPs. To assess and classify the credibility of the associations, we applied the Venice criteria and Bayesian False-Discovery Probability (BFDP). Genetic associations classified as 'positive' and 'less-credible positive' were further validated in three large GWAS consortia conducted in populations of European origin. RESULTS: We initially identified 18 independent variants at 16 loci that were classified as 'positive' polymorphisms for their highly credible associations with CRC risk and 59 variants at 49 loci that were classified as 'less-credible positive' SNPs; 72.2% of the 'positive' SNPs were successfully replicated in three large GWASs and the ones that were not replicated were downgraded to 'less-credible' positive (reducing the 'positive' variants to 14 at 11 loci). For the remaining 231 variants, which were previously reported, our meta-analyses found no evidence to support their associations with CRC risk. CONCLUSION: The CRCgene2 database provides an updated list of genetic variants related to CRC risk by using harmonised methods to assess their credibility.

BACKGROUND: Type 2 diabetes mellitus and high total cholesterol and triglycerides are known to be associated with increased colorectal cancer risk for the general population. These associations are unknown for people with a germline DNA mismatch repair gene mutation (Lynch syndrome), who are at high risk of colorectal cancer. METHODS: This study included 2023 (56.4% female) carriers with a mismatch repair gene mutation (737 in MLH1, 928 in MSH2, 230 in MSH6, 106 in PMS2, 22 in EPCAM) recruited by the Colon Cancer Family Registry between 1998 and 2012. Weighted Cox regression was used to estimate the hazard ratios (HR) and 95% confidence intervals (CI) for the associations between self-reported type 2 diabetes, high cholesterol, triglyceride and colorectal cancer risk. RESULTS: Overall, 802 carriers were diagnosed with colorectal cancer at a median age of 42 years. A higher risk of colorectal cancer was observed in those with self-reported type-2 diabetes (HR 1.92; 95% CI, 1.03-3.58) and high cholesterol (HR 1.76; CI 1.23-2.52) compared with those without these conditions. There was no evidence of high triglyceride being associated with colorectal cancer risk. CONCLUSION: For people with Lynch syndrome, self-reported type-2 diabetes mellitus and high cholesterol were associated with increased colorectal cancer risk.

PURPOSE: Lynch syndrome due to pathogenic variants in the DNA mismatch repair genes MLH1, MSH2, and MSH6 is predominantly associated with colorectal and endometrial cancer, although extracolonic cancers have been described within the Lynch tumor spectrum. However, the age-specific cumulative risk (penetrance) of these cancers is still poorly defined for PMS2-associated Lynch syndrome. Using a large data set from a worldwide collaboration, our aim was to determine accurate penetrance measures of cancers for carriers of heterozygous pathogenic PMS2 variants. METHODS: A modified segregation analysis was conducted that incorporated both genotyped and nongenotyped relatives, with conditioning for ascertainment to estimates corrected for bias. Hazard ratios (HRs) and corresponding 95% CIs were estimated for each cancer site for mutation carriers compared with the general population, followed by estimation of penetrance. RESULTS: In total, 284 families consisting of 4,878 first- and second-degree family members were included in the analysis. PMS2 mutation carriers were at increased risk for colorectal cancer (cumulative risk to age 80 years of 13% [95% CI, 7.9% to 22%] for males and 12% [95% CI, 6.7% to 21%] for females) and endometrial cancer (13% [95% CI, 7.0%-24%]), compared with the general population (6.6%, 4.7%, and 2.4%, respectively). There was no clear evidence of an increased risk of ovarian, gastric, hepatobiliary, bladder, renal, brain, breast, prostate, or small bowel cancer. CONCLUSION: Heterozygous PMS2 mutation carriers were at small increased risk for colorectal and endometrial cancer but not for any other Lynch syndrome-associated cancer. This finding justifies that PMS2-specific screening protocols could be restricted to colonoscopies. The role of risk-reducing hysterectomy and bilateral salpingo-oophorectomy for PMS2 mutation carriers needs further discussion.

Genome-wide association studies have reported 56 independently associated colorectal cancer (CRC) risk variants, most of which are non-coding and believed to exert their effects by modulating gene expression. The computational method PrediXcan uses cis-regulatory variant predictors to impute expression and perform gene-level association tests in GWAS without directly measured transcriptomes. In this study, we used reference datasets from colon (n = 169) and whole blood (n = 922) transcriptomes to test CRC association with genetically determined expression levels in a genome-wide analysis of 12,186 cases and 14,718 controls. Three novel associations were discovered from colon transverse models at FDR ≤ 0.2 and further evaluated in an independent replication including 32,825 cases and 39,933 controls. After adjusting for multiple comparisons, we found statistically significant associations using colon transcriptome models with TRIM4 (discovery P = 2.2 × 10- 4, replication P = 0.01), and PYGL (discovery P = 2.3 × 10- 4, replication P = 6.7 × 10- 4). Interestingly, both genes encode proteins that influence redox homeostasis and are related to cellular metabolic reprogramming in tumors, implicating a novel CRC pathway linked to cell growth and proliferation. Defining CRC risk regions as one megabase up- and downstream of one of the 56 independent risk variants, we defined 44 non-overlapping CRC-risk regions. Among these risk regions, we identified genes associated with CRC (P < 0.05) in 34/44 CRC-risk regions. Importantly, CRC association was found for two genes in the previously reported 2q25 locus, CXCR1 and CXCR2, which are potential cancer therapeutic targets. These findings provide strong candidate genes to prioritize for subsequent laboratory follow-up of GWAS loci. This study is the first to implement PrediXcan in a large colorectal cancer study and findings highlight the utility of integrating transcriptome data in GWAS for discovery of, and biological insight into, risk loci.