Prediction of BRCA1 status in patients with breast cancer using estrogen receptor and basal phenotype.

PURPOSE: To investigate the proportion of breast cancers arising in patients with germ line BRCA1 and BRCA2 mutations expressing basal markers and developing predictive tests for identification of high-risk patients. EXPERIMENTAL DESIGN: Histopathologic material from 182 tumors in BRCA1 mutation carriers, 63 BRCA2 carriers, and 109 controls, collected as part of the international Breast Cancer Linkage Consortium were immunohistochemically stained for CK14, CK5/6, CK17, epidermal growth factor receptor (EGFR), and osteonectin. RESULTS: All five basal markers were commoner in BRCA1 tumors than in control tumors (CK14: 61% versus 12%; CK5/6: 58% versus 7%; CK17: 53% versus 10%; osteonectin: 43% versus 19%; EGFR: 67% versus 21%; P < 0.0001 in each case). In a multivariate analysis, CK14, CK5/6, and estrogen receptor (ER) remained significant predictors of BRCA1 carrier status. In contrast, the frequency of basal markers in BRCA2 tumors did not differ significant from controls. CONCLUSION: The use of cytokeratin staining in combination with ER and morphology provides a more accurate predictor of BRCA1 mutation status than previously available, that may be useful in selecting patients for BRCA1 mutation testing. The high percentage of BRCA1 cases positive for EGFR suggests that specific anti-tyrosine kinase therapy may be of potential benefit in these patients.

Familial breast cancer and the hCHK2 1100delC mutation: assessing cancer risk.

Germline mutations in the human checkpoint gene, hCHK2, were first identified in 1999 in cases of Li-Fraumeni syndrome. Recent studies have demonstrated that the hCHK2 1100delC mutation acts as a low-penetrance tumour suppressor gene in familial breast cancer not associated with mutations in BRCA1 or BRCA2. The present article describes the published studies on hCHK2 1100delC and addresses some of the key questions raised.

TP53, hChk2, and the Li-Fraumeni syndrome.

Germline TP53 mutations are responsible for the large majority of classic LFS families, and a smaller proportion of LFL families. In some of the families shown to have no germline TP53 mutation, germline hChk2 mutations have been described. In some cases the functional consequences of the latter have been demonstrated, although there are still relatively few reports of such mutations. Due to the paucity of families currently described with hChk2 mutations, it is not possible to reach any conclusions concerning the phenotypic/clinical differences between the two types of germline mutation. At least one family with a germline hChk2 mutation is a classic LFS family, whereas others are LFL, variant-LFS, or phenotypically suggestive of LFS. However, there is still a significant number of LFS/LFL families for which no underlying genetic determinant has been identified. It will be fascinating to see what genetic defects are responsible, and whether they involve additional components of DNA damage recognition, repair, or cell cycle checkpoint pathways.

Human papillomavirus type 16 E6 variants in cervical carcinoma: relationship to host genetic factors and clinical parameters.

Infection with human papillomavirus type 16 (HPV-16) confers a high risk for the development of cervical neoplasia. Variants of this virus may interact differentially with host genetic factors, possibly altering the disease course. Thus, HPV-16 E6 variants may differ in their ability to degrade p53 whereas the polymorphic p53 alleles may provide more or less susceptible substrates for the viral oncogene product. Also, E6 variants may differ in immunogenicity by generating different peptides for presentation by polymorphic HLA molecules to specific T cells. This study examines HPV-16 E6 sequence variation in cervical carcinomas from the UK and its relationship to polymorphism of HLA and p53 and to clinical parameters. Sequence analysis of the HPV-16 E6 ORF from 77 tumour biopsies detected the viral prototype sequence in 38% of cases. The most common variation detected was a T to G transition at base pair 350, resulting in an amino acid change from a leucine to a valine. Overall, the frequencies of 350T and 350G sequences were similar (49. 4% and 50.6% respectively). Other mutations of lower frequencies were detected together with and independently of 350G. HPV-16 E6 sequence variation at base pair 350 did not correlate with HLA genotype or clinical outcome. There was no difference in the distribution of p53 proline and arginine alleles between HPV-16-positive cervical carcinoma patients and local controls, and no influence on clinical outcome; however, there was a trend for an increased frequency of p53 arginine homozygotes among the 350T carcinoma patients.