Timing breast cancer surgery and methylation status of genes in relation to the phase of the menstrual cycle.

VH Deshmane^a, IS Fentiman^b, IR Hart^c

^aDepartment of Surgical Oncology, Hinduja Hospital, Mumbai, India, ^bBreast Unit, Guy’s Hospital, London, United Kingdom, ^cDepartment of Tumour Biology, Queen Mary's School of Medicine and Dentistry, Barts and The London, London, United Kingdom

Surgical intervention according to the phase of the menstrual cycle may influence the outcome of premenopausal women with breast cancer. Previous data from Guy's Hospital suggests, women operated upon during the follicular phase of the menstrual cycle have a worse prognosis as compared to those operated upon during the luteal phase. The explanation for this observation, however, remains to be established. Changes in proliferation and adhesion during the menstrual cycle have been suggested as a possible explanation for the effect of timing surgery. Promoter methylation provides a mechanism that can down regulate gene expression and this epigenetic change is potentially reversible. Changes in gene expression, due to an alteration in the methylation status of genes during the menstrual cycle, could provide an explanation for the difference noted in timing studies. To test this hypothesis the promoter methylation status of the E-cadherin gene and p16genes (as a surrogate marker for adhesion/invasion and proliferative potential) was evaluated during the menstrual cycle of patients with breast cancer undergoing primary surgical treatment. Aim: To assess the methylation status of the E-cadherin and the p16 gene promoter in breast tumours operated upon during the follicular and luteal phase of the menstrual cycle. Methods: Using Methylation-specific PCR (MSP) the methylation status of the E-cadherin and p16 gene promoter was established in a cohort of 38 premenopausal patients with breast cancer (24 luteal phase, 14 follicular phase). Results: The overall incidence of methylation involving either the E-cadherin gene (84%) or the p16 gene (68%) was as high as 95% and both were simultaneously methylated in 58%. The methylation status of both genes did not change significantly with the phase of the menstrual cycle (E-cadherin: 87.5% luteal, 78.5% follicular; p16: 71% luteal, 64% follicular). Conclusions: Promoter methylation occurs frequently in breast cancer and diverse genes, involved in different stages of the metastatic cascade, may be simultaneously affected. Assessment of such genes within a tumour may provide a “metastatic profile” of that tumour. Methylation once established does not change with the menstrual cycle phase. However the high incidence of methylation indicates, that in most breast tumours, there exists a subpopulation of cells with a high metastatic potential. Such altered cells, shed during surgical extirpation of a tumour, could then survive, implant and form metastatic deposits in the more favourable biological conditions existing during the follicular phase of the menstrual cycle.

Paper presented at the International Symposium on Predictive Oncology and Intervention Strategies; Nice, France; February 7 - 10, 2004; in oral session 893 (Molecular pathology - Part I).