DNA Methylation of ESR1 and PGR in Breast Cancer: Relationship to Pathologic and Epidemiologic Features
ME Sherman, MM Gaudet, M Campan, XR Yang, JD Figueroa, J Lissowska, B Peplonska, LA Brinton, M Garcia-Closas, PW Laird. National Cancer Institute, Rockville, MD; Memorial Sloan-Kettering Cancer Center, New York, NY; University of Southern California, Los Angeles, CA; Cancer Center and M. Sklodowska-Curie Institute of Oncology, Warsaw, Poland; Nofer Institute of Occupational Medicine, Lodz, Poland
Background: DNA hypermethylation of ESR1 and PGR promoters may be related to ER or PR negative breast cancer. Most data have been derived from small case series and cell lines. Accordingly, we assessed the association between methylation of ESR1 and PGR and ER and PR expression in a population-based study.
Design: We evaluated 200 invasive breast cancers included in a population-based case-control study of 2,386 cases and 2,502 controls conducted in Poland (2000-2003). Using matched hematoxylin and eosin stained slides, 0.6 mm-diameter tissue microarray needles were used to remove tumor-rich cores from formalin fixed paraffin embedded tissues. Following methodologic validation studies, cores were used to prepare bisulfite treated DNA that was tested with MethyLight to assess methylation at 4 CpG islands in promoters: ESR1-1A; ESR1-M3B; PGR-M1A and PGR-M2B and a CpG-rich region, ESR1-M4C. Methylation results were compared to ER, PR and HER2 expression assessed by Automated Quantitative Analysis (AQUA) performed on tissue microarrays, tumor features,and breast cancer risk factors.
Results: When analyzed categorically, methylation of ESR1-M3B and M4C were weakly associated with reduced ER and PR expression and ESR-1-M3B was positively related to HER2 (all reults non-significant). When ESR1-M4C methylation was analyzed continuously, it was significantly inversely related to ER and PR levels and positively related to HER2. In multivariate analyses including age and tumor characteristics, methylation of ESR1 was a predictor of ER, PR and HER2 status, though weaker than tumor size. ESR1-M4C methylation was also weakly associated with younger age, pre-menopausal obesity and short duration of breast feeding.
Conclusions: Low level methylation is common in CpG-rich promoter regions of ESR1 and PGR, but relationships with protein expression are weak and generally non-significant. Strongest associations between DNA methylation and marker expression were found for ESR1-M4C, which is not a true CpG island.
Wednesday, March 11, 2009 9:30 AM
Poster Session V # 6, Wednesday Morning