DNA methylation is an epigenetic phenomenon known to play a critical role in regulating gene expression through interference with the binding of specific transcription factors to recognition sites in promoters [
13]. ETS is one of the largest transcription factor families and has a highly conserved DNA-binding domain that recognizes a common sequence motif, 5’-(C/A) GGA (A/T) -3’ [
14], which is widely distributed in the PARP1 promoter [
15]. The present study showed that BRCA-mutated ovarian cancer displayed a relatively hypomethylated PARP1 promoter, but significantly higher methylation as noted particularly around the ETS motif in normal ovarian tissue. Therefore, we speculate that the important mechanism underlying increased PARP1 expression might be related to the abnormal methylation of CpG sites in the ETS motif, thereby affecting the binding of ETS transcription factors. Previous studies have shown that ETS transcription factors may be key mediators in regulating PARP expression [
15]. Furthermore, an increasing amount of evidence suggests that ETS transcription factors are important regulators of the tumorigenic properties of ovarian cancer cells [
16] and correlate poor survival in serous ovarian carcinoma [
17]. Based on these findings, there are some interesting issues that need to be considered in future studies. PARP1 can enhance DNA methyltransferase 1 (DNMT1) expression by maintaining the unmethylated state of the DNMT1 promoter [
18], so it can be predicted that up-regulation expression of DNMT1 may be beneficial in resisting genome-wide demethylation during the progression of ovarian cancer. Moreover, PARP1, as the protein component of chromatin, controls transcription through affecting the chromatin structure [
19]. Therefore, PARP1 overexpression may constitute a specific epigenetic mark in BRCA-mutated ovarian cancer. Another report indicated that hypermethylation of the BRCA1 promoter correlated with gene inactivation in sporadic breast and ovarian tumors, as inherited BRCA1 mutations [
20]. Thus, it is important for future studies to analyze DNA methylation patterns of the PARP1 promoter in the DNA methylation-associated inactivation of the BRCA1 gene in ovarian cancer.