Genetic and epigenetic classifications define clinical phenotypes and determine patient outcomes in colorectal cancer.

BACKGROUND: A molecular classification of colorectal cancer has been proposed based on microsatellite instability (MSI), CpG island methylator phenotype (CIMP), and mutations in the KRAS and BRAF oncogenes. This study examined the prevalence of these molecular classes, and differences in clinical presentation and outcome. METHODS: Demographics, tumour characteristics and survival were recorded for 391 subjects with colorectal cancer. Tumour DNA was analysed for MSI (high (MSI-H) or microsatellite stable (MSS)), CIMP (high (CIMP-H) or no (CIMP-neg)) and BRAF and KRAS mutations. Clinical differences between four phenotypes were examined. RESULTS: Most tumours were MSS/CIMP-neg (69.8 per cent), with a nearly equal distribution of MSI-H/CIMP-H, MSI-H/CIMP-neg and MSS/CIMP-H types. MSS/CIMP-neg tumours were less likely to be poorly differentiated (P = 0.009). CIMP-H tumours were more common in older patients (P < 0.001). MSI-H/CIMP-H tumours had a high frequency of BRAF mutation and a low rate of KRAS mutation; the opposite was true for MSS/CIMP-neg tumours (P < 0.001). The four molecular phenotypes tended towards divergent survival (P = 0.067 for stages 1-III). MSI-H cancers were associated with better disease-free survival (hazard ratio 2.00 (95 per cent confidence interval 1.03 to 3.91); P = 0.040). CONCLUSION: Colorectal cancers are molecularly and clinically heterogeneous. These different molecular phenotypes may reflect variable prognosis.

Breast tumor immunophenotype of BRCA1-mutation carriers is influenced by age at diagnosis.

PURPOSE: Breast tumors of BRCA1 mutation carriers and those of early onset breast cancer cases share similar histological features, being generally high-grade, highly proliferative, aneuploid tumors that are predominantly estrogen- and progesterone-receptor negative. Because histological features of tumors of premenopausal women differ from those of tumors of older women, we sought to determine whether the immunophenotype of breast tumors of BRCA1 mutation carriers was influenced by age at diagnosis. EXPERIMENTAL DESIGN: We examined 31 breast tumors from BRCA1 mutation carriers and compared them with 81 tumors of age-matched (plus or minus 5 years) breast cancer patients unselected for family history. Tumors were further matched for histology, grade, and size. Paraffin-embedded tumor tissues were examined for protein expression of estrogen receptor (ER), PR, Ki-67, cyclin D1, TP53, HER2, beta-catenin, and cyclin E using immunohistochemical approaches. RESULTS: ER (P = 0.01), PR (P = 0.06), and cyclin D1 (P = 0.002) were less frequently expressed and Ki-67 (P = 0.01) and beta-catenin (P = 0.04) were more frequently expressed in tumors of BRCA1 mutation carriers than controls. After age stratification, we found a significant difference in the frequency of tumors of BRCA1 mutation carriers diagnosed before 50 years of age compared with age-matched controls that stained positive for ER (P = 0.01), PR (P = 0.03), Ki-67 (P = 0.008), cyclin D1 (P < 0.001), HER2 (P = 0.04), and beta-catenin (P = 0.05). However, no significant differences were observed in tumors of BRCA1 mutation carriers diagnosed at age 50 or older compared with age-matched controls. CONCLUSIONS: These data suggest that age at diagnosis, possibly related to menopausal status, may be an important factor in the expression of specific proteins in breast tumors of BRCA1 mutation carriers.

Frequency of BRCA1 and BRCA2 mutations in a clinic-based series of breast and ovarian cancer families.

Mutations in BRCA1 and BRCA2 account for a significant proportion of hereditary breast and ovarian cancer cases. In this study, we sought to determine the frequency of BRCA1- and BRCA2-mutation carrier families in a hospital-based cancer family registry. The frequency of families with germline truncating mutations in BRCA1 and BRCA2 was 17.3% (18/104) and 1.9% (2/104), respectively. Two novel truncating mutations, BRCA1 1848delGA and BRCA2 5694insT, were identified. We also sought to determine the carrier frequency of other affected family members for which the mutation lineage could be established within these families. Not including the probands, 72% (18/25) of the affected family members within the BRCA1 mutation-associated families were carriers, and all four affected members of the BRCA2 families were carriers. These data imply that risk evaluation based on cancer family history alone may result in inaccurate estimates, and where possible, mutation testing should be considered in other affected family members to verify carrier status.

COX2 genetic variation, NSAIDs, and advanced prostate cancer risk.

Collective evidence suggests that cyclooxygenase 2 (COX2) plays a role in prostate cancer risk. Cyclooxygenase 2 is the major enzyme that converts arachidonic acid to prostaglandins, which are potent mediators of inflammation. Nonsteroidal anti-inflammatory drugs (NSAIDs) inhibit the enzymatic activity of COX2 and long-term use of NSAIDs appears to modestly lower the risk of prostate cancer. We investigated whether common genetic variation in COX2 influences the risk of advanced prostate cancer. Nine single-nucleotide polymorphisms (SNPs) in COX2 were genotyped among 1012 men in our case-control study of advanced prostate cancer. Gene-environment interactions between COX2 polymorphisms and NSAID use were also evaluated. Information on NSAID use was obtained by questionnaire. Three SNPs demonstrated nominally statistically significant associations with prostate cancer risk, with the most compelling polymorphism (rs2745557) associated with a lower risk of disease (odds ratio (OR) GC vs GG=0.64; 95% confidence interval (CI): 0.49-0.84; P=0.002). We estimated through permutation analysis that a similarly strong result would occur by chance 2.7% of the time. Nonsteroidal anti-inflammatory drug use was associated with a lower risk of disease in comparison to no use (OR=0.67; 95% CI: 0.52-0.87). No significant statistical interaction between NSAID use and rs2745557 was observed (P=0.12). Our findings suggest that variation in COX2 is associated with prostate cancer risk.

Germline BRCA1 alterations in a population-based series of ovarian cancer cases.

The objective of this study was to provide more accurate frequency estimates of breast cancer susceptibility gene 1 ( BRCA1 ) germline alterations in the ovarian cancer population. To achieve this, we determined the prevalence of BRCA1 alterations in a population-based series of consecutive ovarian cancer cases. This is the first population-based ovarian cancer study reporting BRCA1 alterations derived from a comprehensive screen of the entire coding region. One hundred and seven ovarian cancer cases were analyzed for BRCA1 alterations using the RNase mismatch cleavage assay followed by direct sequencing. Two truncating mutations, 962del4 and 3600del11, were identified. Both patients had a family history of breast or ovarian cancer. Several novel as well as previously reported uncharacterized variants were also identified, some of which were associated with a family history of cancer. The frequency distribution of common polymorphisms was determined in the 91 Caucasian cancer cases in this series and 24 sister controls using allele-specific amplification. The rare form of the Q356R polymorphism was significantly ( P = 0.03) associated with a family history of ovarian cancer, suggesting that this polymorphism may influence ovarian cancer risk. In summary, our data suggest a role for some uncharacterized variants and rare forms of polymorphisms in determining ovarian cancer risk, and highlight the necessity to screen for missense alterations as well as truncating mutations in this population.