Darshana Daftary

Promoter methylation of Wnt antagonists DKK1 and SFRP1 is associated with opposing tumor subtypes in two large populations of colorectal cancer patients

Aberrant activation of canonical Wnt signaling is a hallmark event in colorectal carcinogenesis. The Dickkopf-1 (DKK1) and Secreted Frizzled Related Protein 1 (SFRP1) genes encode extracellular inhibitors of Wnt signaling that are frequently silenced by promoter hypermethylation in colorectal cancer (CRC). These methylation events have been identified as prognostic markers of patient outcome and tumor subtype in several cancers but similar roles in CRC have not been comprehensively examined. In CRC, the microsatellite instability (MSI) subtype associates with favorable disease outcome but the molecular events that are responsible remain poorly understood. Consequently, we quantified promoter methylation status of the Wnt antagonist genes DKK1 and SFRP1 in a large population-based cohort of CRCs from Ontario (n = 549) and Newfoundland (n = 696) stratified by MSI status. We examined the association between methylation status and clinicopathological features including tumor MSI status and patient survival. DKK1 and SFRP1 were methylated in 13 and 95% of CRCs, respectively. In Ontario, DKK1 methylation was strongly associated with MSI tumors after adjustment for age, sex and tumor location [odds ratio (OR) = 13.7, 95% confidence interval (CI) = 7.8-24.2, P < 0.001]. Conversely, SFRP1 methylation was inversely associated with MSI tumors after these adjustments (OR = 0.3, 95% CI = 0.1-0.9, P = 0.009). Similar results were obtained in Newfoundland. There were no independent associations with recurrence-free survival. This is the first large study to identify associations between Wnt antagonist promoter hypermethylation and CRC MSI subtype. These events provide insight into subtype-specific epigenetic mediation of Wnt signaling in CRC.

Association of the Colorectal CpG Island Methylator Phenotype with Molecular Features, Risk Factors, and Family History

Background: The CpG island methylator phenotype (CIMP) represents a subset of colorectal cancers characterized by widespread aberrant DNA hypermethylation at select CpG islands. The risk factors and environmental exposures contributing to etiologic heterogeneity between CIMP and non-CIMP tumors are not known. Methods: We measured the CIMP status of 3,119 primary population-based colorectal cancer tumors from the multinational Colon Cancer Family Registry. Etiologic heterogeneity was assessed by a case–case study comparing risk factor frequency of colorectal cancer cases with CIMP and non-CIMP tumors using logistic regression to estimate the case–case odds ratio (ccOR). Results: We found associations between tumor CIMP status and MSI-H (ccOR = 7.6), BRAF V600E mutation (ccOR = 59.8), proximal tumor site (ccOR = 9; all P < 0.0001), female sex [ccOR = 1.8; 95% confidence interval (CI), 1.5–2.1], older age (ccOR = 4.0 comparing over 70 years vs. under 50; 95% CI, 3.0–5.5), and family history of CRC (ccOR = 0.6; 95% CI, 0.5–0.7). While use of NSAIDs varied by tumor CIMP status for both males and females (P = 0.0001 and P = 0.02, respectively), use of multivitamin or calcium supplements did not. Only for female colorectal cancer was CIMP status associated with increased pack-years of smoking (Ptrend < 0.001) and body mass index (BMI; Ptrend = 0.03). Conclusions: The frequency of several colorectal cancer risk factors varied by CIMP status, and the associations of smoking and obesity with tumor subtype were evident only for females. Impact: Differences in the associations of a unique DNA methylation–based subgroup of colorectal cancer with important lifestyle and environmental exposures increase understanding of the molecular pathologic epidemiology of this heavily methylated subset of colorectal cancer. Cancer Epidemiol Biomarkers Prev; 24(3); 512–9. ©2015 AACR.

Vitamin D Intake Is Negatively Associated with Promoter Methylation of the Wnt Antagonist Gene DKK1 in a Large Group of Colorectal Cancer Patients

Diet and lifestyle influence colorectal cancer (CRC) risk but the molecular events that mediate these effects are poorly characterized. Several dietary and lifestyle factors can modulate DNA methylation suggesting that they may influence CRC risk through epigenetic regulation of cancer-related genes. The Wnt regulatory genes DKK1 and Wnt5a are important contributors to colonic carcinogenesis and are often silenced by promoter hypermethylation in CRC; however, the dietary contributions to these events have not been explored. To investigate the link between dietary/lifestyle factors and epigenetic regulation of these Wnt signaling genes, we assessed promoter methylation of these genes in a large cohort of Canadian CRC patients from Ontario (n = 549) and Newfoundland (n = 443) and examined associations to dietary/lifestyle factors implicated in CRC risk and/or DNA methylation including intake of vitamins, fats, cholesterol, fiber, and alcohol as well as body mass index (BMI), and smoking status. Several factors were associated with methylation status including alcohol intake, BMI, and cigarette smoking. Most significantly, however, dietary vitamin D intake was strongly negatively associated with DKK1 methylation in Newfoundland (P = 0.001) and a similar trend was observed in Ontario. These results suggest that vitamin D and other dietary/lifestyle factors may alter CRC risk by mediating extracellular Wnt inhibition.

Specific Variants in the MLH1 Gene Region May Drive DNA Methylation, Loss of Protein Expression, and MSI-H Colorectal Cancer

Background We previously identified an association between a mismatch repair gene, MLH1, promoter SNP (rs1800734) and microsatellite unstable (MSI-H) colorectal cancers (CRCs) in two samples. The current study expanded on this finding as we explored the genetic basis of DNA methylation in this region of chromosome 3. We hypothesized that specific polymorphisms in the MLH1 gene region predispose it to DNA methylation, resulting in the loss of MLH1 gene expression, mismatch-repair function, and consequently to genome-wide microsatellite instability. Methodology/Principal Findings We first tested our hypothesis in one sample from Ontario (901 cases, 1,097 controls) and replicated major findings in two additional samples from Newfoundland and Labrador (479 cases, 336 controls) and from Seattle (591 cases, 629 controls). Logistic regression was used to test for association between SNPs in the region of MLH1 and CRC, MSI-H CRC, MLH1 gene expression in CRC, and DNA methylation in CRC. The association between rs1800734 and MSI-H CRCs, previously reported in Ontario and Newfoundland, was replicated in the Seattle sample. Two additional SNPs, in strong linkage disequilibrium with rs1800734, showed strong associations with MLH1 promoter methylation, loss of MLH1 protein, and MSI-H CRC in all three samples. The logistic regression model of MSI-H CRC that included MLH1-promoter-methylation status and MLH1 immunohisotchemistry status fit most parsimoniously in all three samples combined. When rs1800734 was added to this model, its effect was not statistically significant (P-value  = 0.72 vs. 2.3×10−4 when the SNP was examined alone). Conclusions/Significance The observed association of rs1800734 with MSI-H CRC occurs through its effect on the MLH1 promoter methylation, MLH1 IHC deficiency, or both.

Promoter methylation of Wnt5a is associated with microsatellite instability and BRAF V600E mutation in two large populations of colorectal cancer patients.

Background:In colorectal cancer (CRC), tumour microsatellite instability (MSI) status and CpG island methylator phenotype (CIMP) status are indicators of patient outcome, but the molecular events that give rise to these outcomes remain largely unknown. Wnt5a is a critical regulator of non-canonical Wnt activity and promoter hypermethylation of this gene has emerging prognostic roles in CRC; however the frequency and prognostic significance of this epigenetic event have not been explored in the context of colorectal tumour subtype. Consequently, we investigated the frequency and prognostic significance of Wnt5a methylation in a large cohort of MSI-stratified CRCs.Methods:Methylation was quantified in a large cohort of 1232 colorectal carcinomas from two clinically distinct populations from Canada. Associations were examined between methylation status and clinicopathlogical features, including tumour MSI status, BRAF V600E mutation, and patient survival.Results:In Ontario, Wnt5a methylation was strongly associated with MSI tumours after adjustment for age, sex, and tumour location (odds ratio (OR)=4.2, 95% confidence interval (CI)=2.4–7.4, P<10−6) and with BRAF V600E mutation, a marker of CIMP (OR=12.3, 95% CI=6.9–21.7, P<10−17), but was not associated with patient survival. Concordant results were obtained in Newfoundland.Conclusion:Methylation of Wnt5a is associated with distinct tumour subtypes, strengthening the evidence of an epigenetic-mediated Wnt bias in CRC.

Association of apolipoprotein E polymorphisms and dietary factors in colorectal cancer

ApoE single nucleotide polymorphisms (SNPs) Cys112Arg (Epsilon-4), and Arg158Cys (Epsilon-2) have been implicated in cardiovascular and Alzheimers disease, but their role in colorectal cancer (CRC) has not been extensively studied. We investigated whether ApoE polymorphisms alone or in combination with dietary factors selectively contribute to mismatch-repair (MMR) proficient (microsatellite stable/low or MSS/L) vs deficient (microsatellite unstable or MSI-H) CRCs. We carried out a case–control study with 906 CRC cases and 911 unaffected controls to examine the associations between ApoE polymorphisms and dietary factors and assessed their contribution to MSS/L and MSI-H CRCs. We used unconditional logistic regression to evaluate the associations between ApoE SNPs, tumour MSI status, and dietary factors after adjusting for age and sex. All statistical tests were two-sided. No significant differences in ApoE genotype frequencies were observed between CRC cases and unaffected controls. We observed that increased dietary intake of total fat, saturated fat, cholesterol, and red meat was significantly associated with CRC. Among non-ApoE4 carriers, 2–4 and >4 red meat servings/week were associated with developing MSS/L CRC (OR=1.51, 95% CI 1.10–2.07 and OR=1.80, 95% CI 1.30–2.48, respectively), whereas among ApoE4 allele carriers, four or more red meat servings/week were associated with MSI-H CRC (OR=4.62, 95% CI 1.20–17.77) when compared with the controls. ApoE isoforms modulate the risk of MSI-H and MSS/L CRCs among high red meat consumers.

Accuracy of Colorectal Polyp Self-Reports: Findings from the Colon Cancer Family Registry

Introduction: Colorectal adenomas and other types of polyps are commonly used as end points or risk factors in epidemiologic studies. However, it is not known how accurately patients are able to self-report the presence or absence of adenomas following colonoscopy. Methods: Participants in the Colon Cancer Family Registry provided self-reports of recent colorectal cancer (CRC) screening activity, and whether or not they had ever been told they had a polyp. Positive and negative predictive values for polyp self-report were calculated by comparing medical records with self-reports from 488 participants. Results: The positive predictive value for self-reported polyp was 80.9%, and the negative predictive value was 85.8%. The predictive values did not differ by age group or sex, but participants with a previous diagnosis of CRC had a lower negative predictive value (76.2%) than participants with no personal history of CRC (89.0%; P = 0.04). Conclusions: Predictive values for self-reports of polyps are fairly high, but researchers needing accurate polyp data should obtain medical record confirmation. Pursuing medical records on only those participants self-reporting a polyp could result in an underestimation of the polyp prevalence in a study population. (Cancer Epidemiol Biomarkers Prev 2007;16(9):1898–901)

Colorectal cancer and self-reported tooth agenesis

BackgroundGermline mutations in APC and AXIN2 are both associated with colon neoplasia as well as anomalous dental development. We tested the hypothesis that congenitally missing teeth may occur more commonly in individuals diagnosed with colorectal cancer than in individuals without this diagnosis.MethodsVia a survey conducted on 1636 individuals with colorectal cancer (CRC) and 2788 individuals with no colorectal cancer from the Colon Cancer Family Registry, self-reported information on congenitally missing teeth was collected. The frequency of missing teeth between cases and controls was compared using Pearson’s chi-squared test or Fisher’s exact test.Results4.8% of cases and 5.7% of controls reported having at least one missing tooth (p = 0.20). When we stratified by recruitment site, gender, and mutation status where available, frequency of missing teeth was not statistically significantly different between cases and controls.ConclusionsThis study did not provide support for there being a general predisposition to missing teeth among a large cohort of CRC patients. The study neither addresses nor excludes the possibility, however, that individuals presenting with notable hypodontia/oligodontia might still have an increased risk for colorectal neoplasia.

Family history of hormonal cancers and colorectal cancer risk: A case‐control study conducted in Ontario

Aggregation of cancers among families with highly penetrant genetic mutations such as hereditary nonpolyposis colorectal cancer is well‐described. However, there is a paucity of data regarding familial aggregation of hormonal cancers (cancers of the breast, endometrial, ovarian and prostate) and colorectal cancer (CRC) in the general population. We investigated the association between having a first‐degree family history of breast, endometrial, ovarian, or prostate cancer and CRC risk. Population‐based CRC cases and controls were recruited by the Ontario Familial Colorectal Cancer Registry (OFCCR). Logistic regression was conducted to obtain odds ratio (OR) estimates and 95% confidence intervals (95% CIs). First‐degree family history of breast cancer was associated with a modest, borderline statistically significant increased CRC risk (age‐, sex‐adjusted OR = 1.2, 95% CI = 1.0, 1.5). The magnitude of CRC risk was greatest if more than one first‐degree kin had breast cancer (age‐, sex‐adjusted OR = 1.7, 95% CI = 1.0, 2.0), as well as if the kin was diagnosed at >50 years of age (age‐, sex‐adjusted OR = 1.4, 95% CI = 1.1, 1.8). Family history of ovarian cancer was associated with reduced CRC risk (multivariate‐adjusted OR = 0.6, 95% CI = 0.3, 1.0). Although statistically significant increases in CRC risk were observed in the age‐, sex‐adjusted OR estimates for family history of endometrial and prostate cancers, the associations were no longer significant after multivariate‐adjustment. In conclusion, individuals with a first‐degree kin with breast cancer may have a modest increased risk for CRC compared to individuals without.