Loss of heterozygosity (LOH) in ovarian cancer

BRCA1 promoter hypermethylation and protein expression in ovarian carcinoma--an Indian study

Mounting evidences suggest that aberrant methylation of CpG islands is a major pathway leading to the inactivation of tumour suppressor genes and the development of cancer. The aim of the current study was to examine the prevalence of the promoter hypermethylation and protein expression of the BRCA1 gene in epithelial ovarian carcinoma (EOC) to understand the role of epigenetic silencing in ovarian carcinogenesis. We studied the promoter methylation of the BRCA1 gene by methylation-specific PCR in a cohort of 88 patients with EOC, 14 low malignant potential (LMP) tumours and 20 patients with benign tumours of the ovary. The expression of the BRCA1 protein by immunohistochemical analysis was carried out in a subset of 64 EOCs, 10 LMP tumours, 10 benign tumours and 5 normal ovarian tissues. The frequencies of methylation in EOCs and LMP tumours were 51.2 and 57%, respectively, significantly higher (p = 0.000 and p = 0.001) in comparison to benign tumours and normal ovarian tissue where no methylation was seen. Expression of BRCA1 was significantly lower in EOCs (p = 0.003). Lack of protein expression correlated with tumour grade and type. The methylation status correlated well with downregulation of BRCA1 expression. Our results clearly demonstrate that hypermethylation of BRCA1 promoter is a frequent event in ovarian cancer. These data support the hypothesis that BRCA1 promoter methylation plays an important role in the functional inactivation of BRCA1. Follow-up clinical data will reveal the impact of BRCA1 methylation on survival.

Clinical Considerations of BRCA1- and BRCA2-Mutation Carriers: A Review

Individuals who carry an inherited mutation in the breast cancer 1 (BRCA1) and BRCA2 genes have a significant risk of developing breast and ovarian cancer over the course of their lifetime. As a result, there are important considerations for the clinician in the counseling, followup and management of mutation carriers. This review outlines salient aspects in the approach to patients at high risk of developing breast and ovarian cancer, including criteria for genetic testing, screening guidelines, surgical prophylaxis, and chemoprevention.

Breast cancer 1 (BRCA1) protein expression as a prognostic marker in sporadic epithelial ovarian carcinoma: an NCIC CTG OV.16 correlative study

BACKGROUND

Breast cancer 1 (BRCA1) protein inactivation in sporadic ovarian carcinoma (OC) is common and low BRCA1 expression is linked with platinum sensitivity. The clinical validation of BRCA1 as a prognostic marker in OC remains unresolved.

PATIENTS AND METHODS

In 251 patient samples from the NCIC CTG clinical trial, OV.16, BRCA1 protein expression was determined by immunohistochemistry.

RESULTS

For all patients, when BRCA1 score was analyzed as a continuous variable, there was no significant correlation between BRCA1 protein expression and progression-free survival (PFS) [adjusted hazard ratio (HR) = 1.15 (0.96-1.37), P = 0.12] or response rate [HR = 0.89 (0.70-1.12), P = 0.32]. In the 116 patients with minimal residual disease (RD), higher BRCA1 expression correlated significantly with worse PFS [HR = 1.40 (1.04-1.89), P = 0.03]. Subgroup analysis divided patients with minimal RD into low (BRCA1 ≤2.5) and high (BRCA1 >2.5) expression groups. Patients with low BRCA1 expression had a more favorable outcome [median PFS was 24.7 and 16.6 months in patients with low and high BRCA1, respectively; HR = 0.56 (0.35-0.89), P = 0.01].

CONCLUSIONS

This study suggests that BRCA1 protein is a prognostic marker in sporadic OC patients with minimal RD. Further research is needed to evaluate BRCA1 as a predictive biomarker and to target BRCA1 expression to enhance chemotherapeutic sensitivity.

Loss of heterozygosity at 1p, 7q, 17p, and 22q in meningiomas

OBJECTIVE

Allelic losses or loss of heterozygosity (LOH) at many chromosomal loci have been found in the cells of meningiomas. The objective of this study was to evaluate LOH at several loci of different chromosomes (1p32, 17p13, 7q21, 7q31, and 22q13) in different grades of meningiomas.

METHODS

Forty surgical specimens were obtained and classified as benign, atypical, and anaplastic meningiomas. After DNA extraction, ten polymorphic microsatellite markers were used to detect LOH. Medical and surgical records, as well as pathologic findings, were reviewed retrospectively.

RESULTS

LOH at 1p32 was detected in 24%, 60%, and 60% in benign, atypical, and anaplastic meningiomas, respectively. Whereas LOH at 7q21 was found in only one atypical meningioma. LOH at 7q31 was found in one benign meningioma and one atypical meningioma. LOH at 17p13 was detected in 4%, 40%, and 80% in benign, atypical, and anaplastic meningiomas, respectively. LOH at 22q13 was seen in 48%, 60%, and 60% in benign, atypical, and anaplastic meningiomas, respectively. LOH results at 1p32 and 17p13 showed statistically significant differences between benign and non-benign meningiomas.

CONCLUSION

LOH at 1p32 and 17p13 showed a strong correlation with tumor progression. On the other hand, LOH at 7q21 and 7q31 may not contribute to the development of the meningiomas.

Sporadic epithelial ovarian cancer: clinical relevance of BRCA1 inhibition in the DNA damage and repair pathway

Among the most promising pathways for molecular targets in sporadic epithelial ovarian cancer (SEOC) are those involving the BRCA1 protein. Because somatic mutations in BRCA1 are rare in SEOC, it was originally postulated that BRCA1 plays a limited role in the pathogenesis of this disease. However, inactivation of BRCA1 through various mechanisms is a relatively frequent event in ovarian cancer. This is important because BRCA1 is involved in the cellular response to DNA damage and repair and has an essential role in the maintenance of genomic stability. The BRCA1 tumor suppressor protein is known to interact with genes and proteins known collectively as the BRCA1 pathway, and defects in this pathway are believed to be a driving force for cancer progression. As a result, there is compelling evidence to suggest that the dysfunction of BRCA1 may be a central mechanism in all ovarian carcinogenesis, and this has clinical and molecular significance beyond the management of patients with hereditary ovarian cancer. The aim of this review is to evaluate the evidence for BRCA1 dysfunction in SEOC and to link this dysfunction to a defective DNA repair pathway and ultimately the promotion of genomic instability and tumorigenesis. Furthermore, we advocate the continued need to study BRCA1 and its pathway by prospectively correlating clinicopathologic data with molecular aberrations. This will determine whether BRCA1 has relevance as a predictive and prognostic marker in SEOC and whether aberrations in the BRCA1 pathway warrant further study as potential therapeutic targets.

Molecular biomarkers for cancer detection in blood and bodily fluids

Cancer is a major and increasing public health problem worldwide. Traditionally, the diagnosis and staging of cancer, as well as the evaluation of response to therapy have been primarily based on morphology, with relatively few cancer biomarkers currently in use. Conventional biomarker studies have been focused on single genes or discrete pathways, but this approach has had limited success because of the complex and heterogeneous nature of many cancers. The completion of the human genome project and the development of new technologies have greatly facilitated the identification of biomarkers for assessment of cancer risk, early detection of primary cancers, monitoring cancer treatment, and detection of recurrence. This article reviews the various approaches used for development of such markers and describes markers of potential clinical interest in major types of cancer. Finally, we discuss the reasons why so few cancer biomarkers are currently available for clinical use.

Accumulation of beta-catenin protein, mutations in exon-3 of the beta-catenin gene and a loss of heterozygosity of 5q22 in solid pseudopapillary tumor of the pancreas

BACKGROUND

Solid pseudopapillary tumors (SPT) of the pancreas are neoplasms with a low malignant potential. The molecular events contributing to the pathogenesis of SPTs are still unknown.

OBJECTIVES

This study was intended to help better understand the early steps of human SPT development.

METHODS

We microdissected 20 SPTs and normal pancreatic tissue. In addition, we examined the DNA from each SPT for mutations in exon-3 of beta-catenin and loss of heterozygosity (LOH) on 9 chromosome arms using 10 microsatellite markers. Immunohistochemical staining for beta-catenin was performed.

RESULTS

Activating mutations between codons 32 and 37 of beta-catenin exon-3 were present in 16 cases (80%). Allelic loss on chromosome 5q22.1 was present in 10 cases (55.5%), while no allelic loss was found on chromosomes 1p, 6q, 9p, 9q, 11p, 11q, 17p, or 22q. Nuclear accumulation of beta-catenin was found in 20 cases (100%).

CONCLUSION

Mutations in exon-3 of the beta-catenin gene, nuclear accumulation of beta-catenin, and LOH on chromosome 5q22.1 in SPT tissue suggest that these mutations are involved in SPT tumorigenesis.