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Open Access Research article

Promoter hypomethylation, especially around the E26 transformation-specific motif, and increased expression of poly (ADP-ribose) polymerase 1 in BRCA-mutated serous ovarian cancer

Fang-Fang Bi1, Da Li12 and Qing Yang1*

  • * Corresponding author: Qing Yang biff@yahoo.cn

  • † Equal contributors

Author Affiliations

1 Department of Obstetrics and Gynecology, Shengjing Hospital, China Medical University, 110004, Shenyang, China

2 Department of Physiology, Institute of Basic Medical Sciences, China Medical University, 110001, Shenyang, China

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BMC Cancer 2013, 13:90  doi:10.1186/1471-2407-13-90

Published: 26 February 2013

Abstract

Background

Poly (ADP-ribose) polymerase 1 (PARP1) overexpression plays a critical role in ovarian cancer progression and the clinical development of PARP1 inhibitors to treat BRCA-mutated ovarian cancer has advanced rapidly. However, the mechanism regulating PARP1 expression remains unknown. Alterations in gene expression mediated by promoter methylation are being increasingly recognized and have frequently been reported in ovarian cancer. We therefore investigated the methylation status of the PARP1 promoter region and its correlation with PARP1 expression in BRCA-mutated ovarian cancer.

Methods

DNA from BRCA-mutated serous ovarian cancer samples and adjacent normal ovarian tissues were analyzed by bisulfite sequence using primers focusing on the CpG island in the promoter region of PARP1. Expression levels of PARP1 were assessed by immunohistochemistry and real-time PCR.

Results

Serous ovarian cancer tissues displayed decreased DNA methylation in the promoter region of PARP1 compared to normal tissue, and methylation intensity correlated inversely with PARP1 mRNA levels. More importantly, E26 transformation-specific (ETS) defined CpG sites were significantly less methylated in ovarian cancer samples.

Conclusions

These results indicate that hypomethylation of the promoter region, especially around the ETS motif might play a role in the upregulation of PARP1 expression in the progression of ovarian cancer.

Keywords:
PARP1; ETS; BRCA mutation; Ovarian cancer; Methylation