Visfatin induces ovarian cancer resistance to anoikis by regulating mitochondrial activity

Purpose: Ovarian cancer is characterized by recurrent peritoneal and distant metastasis. To survive in a non-adherent state, floating ovarian cancer spheroids develop mechanisms to resist anoikis. Moreover, ascitic fluid from ovarian cancer patients contains high levels of visfatin with anti-apoptotic properties. However, the mechanism by which visfatin induces anoikis resistance in ovarian cancer spheroids remains unknown. Here, we aimed to assess wheather visfatin which possess anti-apoptotic properties can induce resistance of anoikis in ovarian cancer spheroids.

Methods: Visfatin synthesis were examined using a commercial human visfatin ELISA Kit. Spheroid were exposed to visfatin and cell viability and caspase 3/7 activity were measured using CellTiter-Glo 3D cell viability assay and Caspase-Glo® 3/7 Assay System. mRNA and protein expression were analyzed by Real-time PCR and Western Blot analysis, respectively. Analysis of mitochondrial activity was estimated by JC-1 staining.

Results: First, our results suggested higher expression and secretion of visfatin by epithelial than by granulosa ovarian cells, and in non-cancer tissues versus cancer tissues. Interestingly, visfatin increased the proliferation/apoptosis ratio in ovarian cancer spheroids. Specifically, both the intrinsic and extrinsic pathways of anoikis were regulated by visfatin. Moreover, the effect of the visfatin inhibitor (FK866) was opposite to that of visfatin. Furthermore, both NAMPT and FK866 affected mitochondrial activity in ovarian cancer cells.

Conclusion: In conclusion, visfatin acts as an anti-apoptotic factor by regulating mitochondrial activity, leading to anoikis resistance in ovarian cancer spheroids. The finding suggest visfatin as a potential novel therapeutic target for the treatment of ovarian carcinoma with peritoneal dissemination.