Abstract 1440: Mitochondrial superoxide dismutase (Sod2) modulates ovarian clear cell carcinoma transcoelomic metastatic pathway

Abstract

Abstract Ovarian clear cell carcinoma (OCCC) is a highly aggressive histological subtype that represents approximately 10% of all ovarian cancer cases and displays high expression of mitochondrial superoxide dismutase (Sod2), a major mitochondrial antioxidant enzyme. In the female body ovarian cancer cells metastasize via the transcoelomic route, where cells detach from the primary tumor into the intraperitoneal (IP) cavity and survive as unattached single cells or spheroid aggregates until they get carried via ascites fluid to the omental wall and surrounding organs for metastatic colonization. Ovarian cancer spheroids evade anoikis and display strong resistant to most anti-proliferative cancer drugs. This may contribute to the high recurrence rate and chemoresistance of ovarian cancer. The present study suggests that Sod2 is critically important for the key events of this transcoelomic metastatic route of OCCC. Levels of Sod2 are further increased in OCCC cell lines when these are cultured as anchorage-independent spheroid aggregates, suggesting that Sod2 may play a major role in spheroid stability and survival. When Sod2 levels are reduced using RNA interference, spheroid morphology of ES-2 OCCC cell line is compromised, suggesting a potential correlation between anoikis resistant and Sod2 levels in OCCC. Sod2 knockdown compromises mitochondrial metabolism, as a consequence of reduced superoxide scavenging, and enhances spheroid sensitivity to cisplatin. In addition, Sod2 is necessary for spheroid attachment and outgrowth on extracellular matrix components, representing the invasion of spheroids into the omental wall. Further, tumor cell metastasis is attenuated with reduced Sod2 levels when ES-2 spheroids are placed on the vasculature of the Chorioallantoic membrane (CAM). Scavenging H2O2 by exogenous addition of catalase inhibits the migration of OCCC and our data suggest that high levels of Sod2 in OCCC shift the intracellular redox balance to drive H2O2-dependent pro-metastatic signaling. These results indicate that Sod2 plays a major role in OCCC tumor metastasis, by regulating survival and chemoresistance of tumor spheroids in the IP cavity and by supporting attachment and migration at secondary metastatic sites. Inhibition of Sod2 can be a potential therapeutic target against OCCC transcoelomic metastasis. Citation Format: L.P.Madhubhani P. Hemachandra, Usawadee Dier, Nadine Hempel. Mitochondrial superoxide dismutase (Sod2) modulates ovarian clear cell carcinoma transcoelomic metastatic pathway. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1440. doi:10.1158/1538-7445.AM2015-1440