Frequency of BRCA1 and BRCA2 mutations in unselected Ashkenazi Jewish patients with colorectal cancer.

Mutations in BRCA1 and BRCA2 that predispose to breast and ovarian cancer are detected in approximately 2.5% of the Ashkenazi Jewish population. To explore whether carriers of Ashkenazi founder mutations in BRCA1 or BRCA2 have an increased risk for colorectal cancer, we screened 586 unselected Ashkenazi Jewish case patients with colorectal cancer for the three common founder mutations in BRCA1 and BRCA2. We identified six carriers (1.02%) among these case patients. After adjusting for age at diagnosis and sex by use of logistic regression analysis, we compared the incidence of carriers in this group of 586 case patients with that of 5012 Ashkenazi Jewish control subjects without a known history of colorectal cancer. The presence of a founder BRCA mutation was not associated with the risk of colorectal cancer (relative risk = 0.50, 95% confidence interval = 0.22 to 1.14). We thus recommend that counseling for colorectal cancer screening and prevention in individuals with BRCA mutations be based on the personal and family history of colorectal cancer or associated syndromic malignancies.

Genomic Alterations in Gastrointestinal Stromal Tumors as Revealed by Conventional and Array-based Comparative Genomic Hybridization.

Gastrointestinal stromal tumor (GIST) is the most commonly occurring mesenchymal neoplasm of the gastrointestinal tract, accounting for 80 percent of these tumors. GIST is highly unresponsive to standard chemotherapy, particularly in patients with advanced or metastatic disease. Recent molecular studies have shown that activating c-kit (KIT) mutations are detectable in a large proportion (>75%) of tumors, between 78% (1) and 89% (2). Approximately 30% of tumors without an identifiable KIT mutation exhibit PDGFRA mutations (3). Furthermore, the KIT mutations are heterogeneous, some being known to confer a relatively better prognosis than others (1). Gross cytogenetic abnormalities associated with GIST appear to be similar regardless of whether a KIT mutation is identified. The molecular genetic alterations associated with multistep GIST tumorigenesis, particularly those which confer intrinsic or acquired resistance to both standard as well as targeted therapeutic approaches, however, are not fully recognized. As an initial approach to identify chromosomal sites of candidate gene(s), which may predict overall clinical and biologic behavior of GISTs, as they relate to response to the specific therapeutic drug Gleevec, we analyzed six GIST samples using both conventional as well as array-based Comparative Genomic Hybridization (CGH). The common abnormalities detected by CGH in low and high grade tumors included loss of all or part of chromosome 14; an entire chromosome 14 was lost in four tumor samples, with the remaining two samples exhibiting loss of the 14q22-q32.3 region. Other recurrent abnormalities included loss of the 1p chromosomal region (four tumor samples), loss of part or entire chromosome 9 (only in metastatic tumors), loss of chromosomes 15 and 22, and a gain of the chromosome 3q region in three samples each. Array- based CGH performed using human BAC arrays (1400V11 Spectral Genomics Chip™) on the other hand, not only detected recurrent abnormalities of the chromosomes and chromosomal sites mentioned above, but also identified losses of additional chromosomal sites on chromosomes 6q and 13q. Array-based CGH further delineated the regions of loss or gain to specific chromosome bands or sub bands based on location of chromosomal site-specific BACs. The specific regions of losses are located at 1p36.2-36.3,6q12,9p13-ter,13q33.33-q34, and gain or amplification of chromosomal DNA at bands 3q26-27. It is interesting to note that some of the chromosomal sites of losses and gains also harbor gene(s) such as AFAR, RIZ1, p73(1p35-36), Akt-1(14q32), p14 and p16(9p21), NF2(22q12), ZASCI, p63 and PIK3CA oncogenes (3q26-27), all of which are known to play a major role in solid tumor pathogenesis. The role of these genes in GIST, however, remains to be seen. Thus, the results of our current study demonstrate that such a combined approach to detect global genomic alterations in GIST is significant in providing information related to chromosomal sites of potential tumor suppressor genes associated with multistep tumorigenesis; some of which also may be predictive of prognosis and clinical outcome following specific targeted therapy, which is the focus of future studies.

MSH6 germline mutations are rare in colorectal cancer families.

Germline mutations in MSH6 can cause HNPCC, which is associated with a tumor phenotype featuring MSI. However, tumors arising in persons with disease-causing mutations of MSH6 may or may not exhibit MSI. We used D-HPLC to screen for germline mutations in the promoter region, the coding region and the 3'-UTR of MSH6. Eighty-four families, enrolled on the basis of Amsterdam I and II criteria (HNPCC families) and less stringent criteria (HNPCC-like families), were tested for MMR gene mutations; 27 families had a disease-causing mutation in MLH1 or MSH2, and the remaining 57 families were tested for mutations in MSH6. Two protein-truncating mutations were identified in each of 2 families fulfilling the Amsterdam I criteria, being present in persons affected with early-onset colorectal cancers exhibiting MSI. Immunohistochemical analysis showed that expression of both MSH2 and MSH6 proteins was lost in the cancer cells of the 2 mutation carriers but only MSH6 protein expression was lost in 2 adenomatous polyps. A third possibly disease-causing mutation was found in a person affected with a tumor that did not exhibit MSI. In addition, we found 4 new polymorphisms and determined that neither of the 2 studied by association analysis conferred susceptibility to colorectal or endometrial cancer. Altogether, our results indicate that disease-causing germline mutations of MSH6 are rare in HNPCC and HNPCC-like families.

A636P is associated with early-onset colon cancer in Ashkenazi Jews.

BACKGROUND: Hereditary predisposition to colorectal cancer most often manifests itself as familial adenomatous polyposis from mutations of APC, or hereditary nonpolyposis colorectal cancer, resulting from mutations of MSH2, MLH1, MSH6, or other genes. Previously, we described a rare founder mutation MSH2*1906C > G in Ashkenazi Jews that was found in 8 of 1,345 individuals (0.6%) of Ashkenazi descent with colorectal cancer. This study seeks to characterize the proportion of individuals of Ashkenazi heritage with very early-onset colon cancer (diagnosed at age 40 or younger) that could be attributed to MSH2*1906C>G. STUDY DESIGN: We analyzed the carrier frequency of MSH2*1906C>G in paraffin samples from 31 Jewish patients age 40 or less, diagnosed with colorectal cancer at Memorial Sloan-Kettering and lymphocyte-derived DNA from 10 patients. We did not select for family history. Genotyping for MSH2*1906C>G was performed by polymerase chain reaction and restriction enzyme digestion methods. RESULTS: We detected the MSH2*1906G>C mutation in 3 of the 41 samples (7.14%) of patients who had colorectal cancer diagnosed at age 40 or younger. This incidence is significantly greater than the 8 in 1,345 (0.6%) we observed for cases of colorectal cancer in Ashkenazi Jews not selected for age (p = 0.004). CONCLUSION: Although very rare in the population, MSH2*1906G>C is found at an increased frequency in young Jewish patients with colorectal cancer. These results suggest that testing for the MSH2*1906G>C mutation should be included in the evaluation of Ashkenazi Jewish individuals diagnosed with early-onset colon cancer.

Frequency of CHEK2*1100delC in New York breast cancer cases and controls.

BACKGROUND: The 1100delC CHEK2 allele has been associated with a 1.4-4.7 fold increased risk for breast cancer in women carrying this mutation. While the frequency of 1100delC was 1.1-1.4% in healthy Finnish controls, the frequency of this allele in a North American control population and in North American breast cancer kindreds remains unclear. METHODS: We genotyped 1665 healthy New York volunteers and 300 cases of breast cancer for the CHEK2*1100delC. RESULTS: The overall frequency of the 1100delC was 3/300 (1.0%) among all cases with either a family history of breast cancer (n = 192) or a personal history of breast cancer (n = 108, of which 46 were bilateral, 46 unilateral, and 16 were male breast cancer cases), compared to a frequency of 5/1665 (0.3%) in healthy controls (p = 0.1). There was no difference in allele frequency among Ashkenazi and non-Ashkenazi controls. CONCLUSION: The relatively low breast cancer penetrance of this allele, along with the low population frequency, will limit the clinical applicability of germline testing for CHEK2*1100delC in North American kindreds.

Rare variants of ATM and risk for Hodgkin's disease and radiation-associated breast cancers.

PURPOSE: In this study, we first sought to evaluate whether individuals heterozygous for ATM mutations may have an increased susceptibility to radiation-induced breast cancer (BC) after treatment for Hodgkin's disease (HD). We next sought to determine the frequency of ATM variants in patients with Hodgkin's lymphoma, regardless of coexisting BC, compared with healthy volunteers. EXPERIMENTAL DESIGN: Full sequence analysis of ATM was performed on cDNA from peripheral blood lymphocytes from 37 cases of BC after therapeutic radiation therapy for HD and 27 comparison cases with HD and no BC treated during the same time period. The frequency of ATM variants was analyzed in the total group of 64 cases of HD and compared to allele frequencies in 128 ethnically matched controls from the same geographical region. RESULTS: No protein-truncating ATM mutations were observed in cases with HD with or without BC. Missense mutations were more frequent in the cohort with HD compared with patients with BC following HD (P = 0.02). The median time from HD to the development of BC was 18 years in patients with ATM variants compared with 16 years in those with no ATM variants (P = 0.04). Multiple ATM variants, including one homozygous mutation, were observed in 9 HD cases. CONCLUSIONS: Heterozygous protein-truncating or missense mutations of ATM were not associated with increased radiation-associated risk of BC after HD. The observation of multiple germ-line mutations and a homozygote suggests that rare ATM variants may constitute cancer-susceptibility alleles in a subset of cases.