Effects of Per2 overexpression on growth inhibition and metastasis, and on MTA1, nm23-H1 and the autophagy-associated PI3K/PKB signaling pathway in nude mice xenograft models of ovarian cancer

Abstract

The aim of the present study was to evaluate the association between Period2 ( Per2) and the occurrence and development of ovarian cancer, in addition to evaluating the effect of this gene on the growth and metastasis of ovarian cancer in nude mice xenograft models. The detection of Per2 by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and western blotting methods at various stages of ovarian cancer in tumor tissue samples was conducted. Nude mice xenograft models of ovarian cancer were constructed using an ovarian cancer cell line and, using a gene transfection technique, exogenous infusion of the recombinant gene, Per2, was performed. To assess for the successful and stable expression of Per2 in the tumor tissue, levels of Per2 expression in the nude mice xenograft models were detected by RT-qPCR. During the experimental period, the tumor volumes were measured every three days. Two weeks following treatment cessation, the nude mice were sacrificed and the tumor weight and volume were measured. Furthermore, detection of the changes in expression levels of metastasis-associated gene 1 ( MTA-1) and tumor metastasis suppressor gene, non-metastasis protein 23-H1 ( nm23-H1), and the expression change of autophagy-associated signal transduction pathway, phosphatidylinositol 3-kinase (PI3K)/protein kinase B (PKB) kinase were analyzed. The findings demonstrated that with ovarian cancer stage development, the expression of Per2 gradually reduced or ceased. In addition, exogenous Per2 was successfully and stably expressed in nude mice tumor tissue samples. Furthermore, in the Per2 overexpression group, MTA-1 protein expression was significantly reduced when compared with the phosphate-buffered saline (PBS) control and empty plasmid groups, while nm23-H1 protein expression was significantly higher when compared with those two groups. The expression levels of PI3K and PKB kinase, which are marker proteins of the autophagy associated signaling pathway PI3K/PKB, were significantly downregulated, when compared with the PBS control and empty plasmid groups (P<0.001). Thus, it was demonstrated that Per2 is closely associated with the development of ovarian cancer, and late-stage ovarian cancer is associated with Per2 mutation or deletion. Per2 overexpression, via exogenous infusion reduced the ovarian cancer growth rate, which was demonstrated by a significant increase in the tumor inhibition rate. In addition, Per2 may inhibit the expression of MTA-1 and promote the expression of nm23-H1 to restrict ovarian tumor growth and metastasis. Finally, it is hypothesized that Per2 affects autophagy by interfering with the PI3K/PKB signaling pathway, causing inhibition of tumor angiogenesis in order to inhibit tumor growth.