Relationship between promoter methylation & tissue expression of MGMT gene in ovarian cancer.

Background & objectives: Epigenetic alterations, in addition to multiple gene abnormalities, are involved in the genesis and progression of human cancers. Aberrant methylation of CpG islands within promoter regions is associated with transcriptional inactivation of various tumour suppressor genes. O6-methyguanine-DNA methyltransferase (MGMT) is a DNA repair gene that removes mutagenic and cytotoxic adducts from the O6-position of guanine induced by alkylating agents. MGMT promoter hypermethylation and reduced expression has been found in some primary human carcinomas. We studied DNA methylation of CpG islands of the MGMT gene and its relation with MGMT protein expression in human epithelial ovarian carcinoma. Methods: A total of 88 epithelial ovarian cancer (EOC) tissue samples, 14 low malignant potential (LMP) tumours and 20 benign ovarian tissue samples were analysed for MGMT promoter methylation by nested methylation-specific polymerase chain reaction (MSP) after bisulphite modification of DNA. A subset of 64 EOC samples, 10 LMP and benign tumours and five normal ovarian tissue samples were analysed for protein expression by immunohistochemistry. Results: The methylation frequencies of the MGMT gene promoter were found to be 29.5, 28.6 and 20 per cent for EOC samples, LMP tumours and benign cases, respectively. Positive protein expression was observed in 93.8 per cent of EOC and 100 per cent in LMP, benign tumours and normal ovarian tissue samples. Promoter hypermethylation with loss of protein expression was seen only in one case of EOC. Interpretation & conclusions: Our results suggest that MGMT promoter hypermethylation does not always reflect gene expression.

Clinical outcome of adjuvant endocrine treatment according to Her-2/neu status in breast cancer.

Background & objectives: An association between over-expression of proto-oncogene Her-2/neu and resistance to tamoxifen in estrogen receptor (ER) positive, primary and metastatic breast cancer has been suggested. HR+/Her-2/neu+ patients have a poor response to endocrine therapy, making this group a matter of debate. The present study was carried out to examin whether Her-2/neu expression in breast cancer patients predicted tamoxifen effectiveness. Methods: An enzyme-linked immunosorbent assay (ELISA) specific for the extracellular domain of the Her-2/neuoncoprotein product was used to detect serum Her-2/neu levels in 207 patients with histological confirmed breast cancer. Tissue Her-2/neu expression was studied in 100 breast cancer patients by immunohistochemistry (IHC) and compared with serum Her-2/neu levels by ELISA. Results: Among 207 histologically confirmed breast cancer patients, 53 were serum Her-2/neu positive. Patients who were treated with surgery, chemotherapy, and radiotherapy showed significantly (P<0.05) reduced serum Her-2/neu levels, showing good response to treatment. Patients who were treated with tamoxifen in addition to the above regimen did not show any significant reduction in serum Her-2/neu levels showing resistance to treatment. Interpretation & conclusions: The present findings study support the hypothesis that Her-2/neu overexpression contributes to tamoxifen resistance. Trastuzumab or other growth factor inhibitors should be used in combination with tamoxifen, since monotherapy is not likely to be optimal in HR+/Her-2/neu+ tumours.

Association of methylenetetrahydrofolate reductase gene polymorphisms & colorectal cancer in India.

Background & objectives: Methylenetetrahydrofolate reductase (MTHFR) is a critical enzyme in folate metabolism and involved in DNA synthesis, DNA repair and DNA methylation. The two common functional polymorphisms of MTHFR, 677 C→T and 1298 A→C have shown to impact several diseases including cancer. This case-control study was undertaken to analyse the association of the MTHFR gene polymorphisms 677 C→T and 1298 A→C and risk of colorectal cancer (CRC). Methods: One hundred patients with a confirmed histopathologic diagnosis of CRC and 86 age and gender matched controls with no history of cancer were taken for this study. DNA was isolated from peripheral blood samples and the genotypes were determined by PCR-RFLP. The risk association was estimated by compounding odds ratio (OR) with 95 per cent confidence interval (CI). Results: Genotype frequency of MTHFR 677 CC, CT and TT were 76.7, 22.1 and 1.16 per cent in controls, and 74, 25 and 1.0 per cent among patients. The ‘T’ allele frequency was 12.21 and 13.5 per cent in controls and patients respectively. The genotype frequency of MTHFR 1298 AA, AC, and CC were 25.6, 58.1 and 16.3 per cent for controls and 22, 70 and 8 per cent for patents respectively. The ‘C’ allele frequency for 1298 A→C was 43.0 and 45.3 per cent respectively for controls and patients. The OR for 677 CT was 1.18 (95% CI 0.59-2.32, P = 0.642), OR for 1298 AC was 1.68 (95% CI 0.92-3.08, P = 0.092) and OR for1298 CC was 0.45 (95% CI 0.18-1.12, P = 0.081). The OR for the combined heterozygous state (677 CT and 1298 AC) was 1.18 (95% CI 0.52-2.64, P =0.697). Interpretation & conclusion: The frequency of the MTHFR 677 TT genotype is rare as compared to 1298 CC genotype in the population studied. There was no association between 677 C→T and 1298 A→C polymorphisms and risk of CRC either individually or in combination. The homozygous state for 1298 A→C polymorphism appears to slightly lower risk of CRC. This needs to be confirmed with a larger sample size.

Homocysteine, vitamin B12 and folate status in pediatric acute lymphoblastic leukemia.

OBJECTIVE: The cause of majority of acute leukemias is unknown, but likely to involve interaction of environment, hematopoitic development and weak susceptibility loci within an individual's genetic constitution. The present study evaluates the association between plasma levels of homocysteine, folate and vitamin B12 and acute lymphoblastic leukemia. METHODS: Plasma levels of homocysteine, folate and vitamin B12 were compared between cases of acute lymphoblastic leukemia and age and sex matched normal controls. Homocysteine levels were measured by solid immunoassay, while folate and vitamin B12 levels were determined by radioassay. RESULTS: Folate levels were significantly among cases as compared to control group (8.56 +/- 4.35) vs (14.04 +/- 2.62) ng/ml, P< 0.001). Although individually vitamin B12 and homocysteine were not significant different between cases and controls, the combined effect of all three parameters was significantly different (P< 0.001), with 83.3% of correct classification of cases and controls was obtained by discriminate function analysis. CONCLUSION: The data provide evidence for the role of folate, vitamin B12 and homocysteine levels in acute lymphoblastic leukemia, suggesting that gene-environment interaction may be an important factor in the development of acute lymphoblastic leukemia.

Clinical utility of serum human epidermal receptor-2/neu detection in breast cancer patients.

BACKGROUND & OBJECTIVE: In breast cancer, the HER-2/neu gene is amplified in 20-30 per cent of cases. The mechanism by which the amplification/overexpression occurs is not known. Elevated serum HER-2/neu levels have been shown to be associated with a poor clinical prognosis and decreased survival in early stage breast cancer patients, and thus might help in management of the disease. The present study was therefore to estimate the serum HER-2/neu levels in breast cancer patients and associate with other prognostic factors. METHODS: Serum HER-2/neu levels were studied in 207 patients with cancer breast, 15 benign breast diseases (BBD) and 175 age-matched healthy controls. Patients' age, menopausal status, node and hormone receptor status were compared with serum HER-2/neu levels. RESULTS: Serum HER-2/neu overexpression was associated with age, disease stage and positive nodal status but not with menopausal status. Serum HER-2/neu levels were negatively related with hormone receptor positivity. INTERPRETATION & CONCLUSION: HER-2/neu serum test could be done more frequently in women with breast cancer irrespective of the hormone receptor status, to suggest modifications in systemic adjuvant therapy, including possibly the use of Herceptin.