Original ArticleSEI1 induces genomic instability by inhibiting DNA damage response in ovarian cancer

•SEI1 is frequently overexpressed in ovarian cancer and associated with tumor stage.•Overexpression of SEI1 is associated with genomic instability.•SEI1 is co-located with components of DDR complex in ovarian cancer cell line.•SEI1 changes the distribution of DDR related proteins, increased genomic instability.

Previous studies have shown that the oncogene SEI1 is highly expressed in ovarian carcinomas, and promoting genomic instability. However, the molecular mechanism of SEI1 in promoting genomic instability remains unclear. We observed SEI1 overexpression in 30 of 46 cases of ovarian cancer compared to non-tumor tissues and the overexpression of SEI1 was positively associated with the tumor FIGO stage. Our functional studies revealed that overexpression of SEI1 could induce genomic instability and increased DNA strand breaks. In contrast, SEI1 co-localized with γH2AX and phosphorylated ATM and DNAPKcs in the nucleus. Furthermore, we found that overexpression of SEI1 induced translocation of the SEI1 protein from the cytoplasm to the nucleus; ATM and DNAPKcs were associated with the cytoplasm-to-nucleus translocation of SEI1. To further prove the correlation between the DNA damage response (DDR) and SEI1, we knocked down SEI1 expression in SEI1-transfected ovarian cancer cell lines. The expression of DDR proteins was significantly downregulated, and the number of micronuclei was significantly decreased. Together, these results define a new mechanism of SEI1 in the regulation of genomic stability and in the malignant progression of ovarian cancer.