Suijkerbuijk KPM, Fackler MJ, Sukumar S, van Gils CH, van Laar T, van der Wall E, Vooijs M, van Diest PJ. Methylation is less abundant in BRCA1-associated compared with sporadic breast cancer.
Ann Oncol 2008;
19:1870-4. [PMID:
18647968 DOI:
10.1093/annonc/mdn409]
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Abstract
BACKGROUND
Promoter methylation is a common epigenetic mechanism to silence tumor suppressor genes during breast cancer development. We investigated whether BRCA1-associated breast tumors show cancer-predictive methylation patterns similar to those found in sporadic tumors.
PATIENTS AND METHODS
Quantitative multiplex methylation-specific PCR of 11 genes involved in breast carcinogenesis (RARB, RASSF1, TWIST1, CCND2, ESR1, SCGB3A1, BRCA1, BRCA2, CDKN2A, APC, CDH1) was carried out on 32 BRCA1-associated and 46 sporadic breast carcinomas and on normal breast tissue from seven BRCA1 mutation carriers and 13 non-carriers.
RESULTS
The extent of cumulative methylation increased with age (P < 0.001). The median cumulative methylation index (CMI) of all studied genes was significantly higher in tumors (89) than in normal tissue (13, P < 0.001). The median CMI was significantly lower in BRCA1-associated (59) than in sporadic breast tumors (122, P = 0.001), in estrogen receptor (ER)-negative tumors (73) than in ER-positive tumors (122, P = 0.005) and in lymph node-negative (77) compared with lymph node-positive tumors (137, P = 0.007). In subgroup analysis, the effect of a BRCA1 germline mutation on methylation proved to be independent of ER status, lymph node status and age.
CONCLUSIONS
These data indicate that BRCA1-associated breast cancers show less promoter methylation compared with sporadic breast carcinomas indicating a difference in disease etiology.
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