High expression of ENPP1 in high-grade serous ovarian carcinoma predicts poor prognosis and as a molecular therapy target

Abstract

Recent studies have shown that the expression of ENPP1 is related to differentiation, death, dissemination and chemosensitivity of tumor cells. So far, there is no research in ovarian carcinoma. This study aimed at exploring the role of ENPP1 gene in ovarian carcinoma, the relationship with prognostic indicators and chemotherapy resistance, and investigates the possibility of molecular targeted therapy. The expression of ENPP1 in 41 normal ovarian epithelial tissues, 97 ovarian serous cystadenoma and 103 HGSOC tissues was detected by IHC. In ovarian cancer tissues and ovarian cancer cell lines, mRNA and protein expression of ENPP1 was determined by qRT-PCR and Western blot. The ENPP1 expression was knockdowned by siRNA. Cell proliferation was measured with the BrdU Cell Proliferation ELISA. Cell migration and invasion were detected by Wound-Healing, Transwell migration and Matrigel invasion assay. Caspase 3 activity was determined by the CaspACE. The expression of EMT markers such as E-cadherin, N-cadherin, and Vimentin was measured, and the expression of PCNA and MMP9 was also be detected. The results showed that the expression of ENPP1 was significantly increased in high-grade ovarian serous carcinoma, the number of strong expression was 85.4% (22.3%+63.1%) and only 1.03% (1.03%+0.0%) in serous cystadenoma, but no in normal ovarian epithelium (P< 0.05). And the stronger the expression of ENPP1, the later the FIGO stage and the poorer differentiation of cells (P = 0.001 or <0.001, respectively). However, no correlation was found between the expression of ENPP1 and chemosensitivity. ENPP1 was also highly expressed in ovarian cancer tissues and in epithelial ovarian cancer cell lines (A2780, CaoV3, OVCAR3, SKOV3 and 3ao). After down-regulation of ENPP1 expression by RNA interference, the cell proliferation, migration and invasion of ovarian cancer cell decreased significantly, the expression of apoptosis related gene caspase 3 increased significantly, while the expression of PCNA and MMP9 was significantly down regulated. In addition, EMT biological characteristics of A2780 and SKOV3 cells were also inhibited. In summary, the increased expression of ENPP1 may be related to the occurrence of HGSOC, and indicate that the disease progresses rapidly and the prognosis is poor. ENPP1 may be considered as a potential molecular therapeutic target.