Breast cancer risk in relation to alcohol consumption and BRCA gene mutations--a case-only study of gene-environment interaction

The variable penetrance of the BRCA1 and BRCA2 genes suggests that other genetic or environmental factors may interact with these mutations to modify breast cancer risk. The objective of this study was to measure departures from multiplicative effects of alcohol consumption and BRCA gene mutations. A cohort of French-Canadian breast cancer patients was tested for BRCA gene mutations and completed a food frequency questionnaire. The case-only odds ratio (COR) was calculated. A total of 857 women, including 10 BRCA1 and 33 BRCA2 mutation carriers, participated in the study. No significant interaction between alcohol consumption and BRCA1 mutations was detected, although the interaction with wine consumption suggested a sub-multiplicative effect (COR = 0.38, 95% CI: 0.08-1.81). Consumption of alcohol other than wine interacted significantly with BRCA2 mutations (COR = 2.15, 95% CI: 1.03-4.49). Consumption of wine may protect against BRCA1-associated tumors, while women with BRCA2 mutations may be at greater risk of alcohol-induced breast cancer.

The contribution of founder mutations to early-onset breast cancer in French-Canadian women

In an ethnically-homogeneous population, it is valuable to identify founder mutations in cancer-predisposing genes. Founder mutations have been found in four breast-cancer-predisposing genes in French-Canadian breast cancer families. The frequencies of the mutant alleles have been measured neither in a large series of unselected breast cancer patients from Quebec, nor in healthy controls. These estimates are necessary to measure their contribution to the hereditary burden of breast cancer in Quebec and to help develop genetic screening policies which are appropriate for the province. We studied 564 French-Canadian women with early-onset invasive breast cancer who were treated at a single Montreal hospital. Patients had been diagnosed at age 50 or less, and were ascertained between 2004 and 2008. We screened all 564 patients for nine founder mutations: four in BRCA1, three in BRCA2 and one each in PALB2 and CHEK2. We also studied 6433 DNA samples from newborn infants from the Quebec City area to estimate the frequency of the nine variant alleles in the French-Canadian population. We identified a mutation in 36 of the 564 breast cancer cases (6.4%) and in 35 of 6443 controls (0.5%). In the breast cancer patients, the majority of mutations were in BRCA2 (54%). However, in the general population (newborn infants), the majority of mutations were in CHEK2 (54%). The odds ratio for breast cancer to age 50, given a BRCA1 mutation, was 10.1 (95% CI: 3.7-28) and given a BRCA2 mutation was 29.5 (95% CI: 12.9-67). The odds ratio for breast cancer to age 50, given a CHEK2 mutation, was 3.6 (95% CI: 1.4-9.1). One-half of the women with a mutation had a first- or second-degree relative diagnosed with breast or ovarian cancer. Thus, it can be concluded that a predisposing mutation in BRCA1, BRCA2, CHEK2 or PALB2 is present in approximately 6% of French-Canadian women with early-onset breast cancer. It is reasonable to offer screening for founder mutations to all French-Canadian women with breast cancer before age 50. The frequency of these mutations in the general population (0.5%) is too low to advocate population-based screening.

The Contribution of Founder Mutations to Early-Onset Breast Cancer in French-Canadian Women

Background: In an ethnically-homogeneous population, it is valuable to identify founder mutations in cancer-predisposing genes. Founder mutations have been found in four breast cancer predisposing genes in French-Canadian breast cancer families. The frequencies of the mutant alleles have not been measured in a large series of unselected breast cancer patients from Quebec, nor in healthy controls. These estimates are necessary to measure their contribution to the hereditary burden of breast cancer in Quebec and to help develop genetic screening policies which are appropriate for the province.Methods: We studied 564 French-Canadian women with early-onset invasive breast cancer who were treated at a single Montreal hospital. Patients had been diagnosed at age 50 or less, and were ascertained between 2004 and 2008. We screened all 564 patients for nine founder mutations; four in BRCA1, three in BRCA2 and one each in PALB2 and CHEK2. We also studied 6433 DNA samples from newborn infants from the Quebec City area to estimate the frequency of the nine variant alleles in the French-Canadian population.Results: We identified a mutation in 36 of the 564 breast cancer cases (6.4%) and in 35 of 6443 controls (0.5%). In the breast cancer patients, the majority of mutations were in BRCA2 (54%). However, in the general population (newborn infants), the majority of mutations were in CHEK2 (54%). The odds ratio for breast cancer to age 50, given a BRCA1 mutation was 10.1 (95% CI: 3.7 to 28) and given a BRCA2 mutation was 29.5 (95% CI: 12.9 – 67). The odds ratio for breast cancer to age 50, given a CHEK2 mutation was 3.6 (95% CI: 1.4 – 9.1). One-half of the women with a mutation had a first or second-degree relative diagnosed with breast or ovarian cancer.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 902.

Breast cancer risk in relation to the joint effect of BRCA mutations and diet diversity

It has been suggested that gene-environment interaction is related to the risk of cancer. To evaluate departure from multiplicative effects between BRCA mutations and diet diversity in breast cancer (BC), a case-only study was carried out in a French-Canadian population including 738 patients with incident primary BC comprising 38 BRCA mutation carriers. Diet diversity was assessed using a validated food frequency questionnaire. Unconditional logistic regression analysis was performed to assess case-only odds ratio (COR) and 95% confidence interval (CI) while adjusting for age, body mass index, smoking, hormonal replacement therapy, and total energy intake. Ours results reveal a strong and significant interaction between BRCA mutations and vegetable and fruit diversity (COR = 0.27; 95%CI = 0.10-0.80; P = 0.03) when comparing the upper to the lower quartiles. The estimates for departure from multiplicative effects between BRCA mutations and total or other food groups' diversity were not supportive of the idea of a gene-environment interaction. The results of this study suggest that the combination of BRCA mutations and vegetable and fruit diversity may be associated with a reduced risk of BC.

Identification of a novel truncating PALB2 mutation and analysis of its contribution to early-onset breast cancer in French-Canadian women

Background

PALB2 has recently been identified as a breast cancer susceptibility gene. PALB2 mutations are rare causes of hereditary breast cancer but may be important in countries such as Finland where a founder mutation is present. We sought to estimate the contribution of PALB2 mutations to the burden of breast cancer in French Canadians from Quebec.

Methods

We screened all coding exons of PALB2 in a sample of 50 French-Canadian women diagnosed with either early-onset breast cancer or familial breast cancer at a single Montreal hospital. The genetic variants identified in this sample were then studied in 356 additional women with breast cancer diagnosed before age 50 and in 6,448 newborn controls.

Results

We identified a single protein-truncating mutation in PALB2 (c.2323 C>T, resulting in Q775X) in 1 of the 50 high-risk women. This variant was present in 2 of 356 breast cancer cases and in none of 6,440 newborn French-Canadian controls (P = 0.003). We also identified two novel new non-synonymous single nucleotide polymorphisms in exon 4 of PALB2 (c.5038 A>G [I76V] and c.5156 G>T [G115V]). G115V was found in 1 of 356 cases and in 15 of 6,442 controls (P = 0.6). The I76V variant was not identified in either the extended case series or the controls.

Conclusion

We have identified a novel truncating mutation in PALB2. The mutation was found in approximately 0.5% of unselected French-Canadian women with early-onset breast cancer and appears to have a single origin. Although mutations are infrequent, PALB2 can be added to the list of breast cancer susceptibility genes for which founder mutations have been identified in the French-Canadian population.

Germline TP53 mutations in BRCA1 and BRCA2 mutation-negative French Canadian breast cancer families

About 40% of French Canadian breast and/or ovarian cancer families harbor germline BRCA1 or BRCA1 mutations where common mutations account for about 84% of all mutations identified in cancer families. Within a series of BRCA1 and BRCA2 mutation-negative families, a germline TP53 13398 G>A (Arg213Gln) mutation was identified, which was selected for mutation analysis in this gene because of a family history consistent with Li-Fraumeni syndrome (LFS). Given the founder effects in this population, the 13398 G>A mutation was screened in series of 52 BRCA1 and BRCA2 mutation-negative cancer families, and a mutation-positive family was identified. However, pedigree inspection and expansion of mutation-positive families with the same mutation revealed that they were closely related to each other. To further characterize the contribution of TP53 in cancer families, mutation analysis was performed in the remaining BRCA1 and BRCA2 mutation-negative cancer families. Thirty sequence variants were identified, the majority of which occur in intronic sequences and are not predicted to affect the functionality of TP53. However, the 14538 G>A (Arg290His) mutation was identified in a family which did not exhibit features consistent with LFS or Li-Fraumeni-like (LFL) syndrome. Neither of the TP53 mutations was detected in 381 French Canadian women with breast cancer diagnosed before 50 years of age not selected for family history of cancer. In all, germline TP53 mutations were identified in two of 52 (3.8%) cancer families, suggesting that TP53 is not a major contributor to BRCA1 and BRCA2 mutation-negative breast and/or ovarian cancer families of French Canadian descent.