Epithelial ovarian cancer (EOC) is the fourth leading cause of death due to cancer in women and comprises distinct histologic subtypes, which vary widely in their genetic profiles and tissues of origin. It is therefore imperative to understand the etiology of these distinct diseases. Ovarian clear cell carcinoma (OCCC), a very aggressive subtype, comprises >10% of EOCs. In the present study, we show that mitochondrial superoxide dismutase (Sod2) is highly expressed in OCCC compared with other EOC subtypes. Sod2 is an antioxidant enzyme that converts highly reactive superoxide (O2•−) to hydrogen peroxide (H2O2) and oxygen (O2), and our data demonstrate that Sod2 is protumorigenic and prometastatic in OCCC. Inhibiting Sod2 expression reduces OCCC ES-2 cell tumor growth and metastasis in a chorioallantoic membrane (CAM) model. Similarly, cell proliferation, migration, spheroid attachment and outgrowth on collagen, and Akt phosphorylation are significantly decreased with reduced expression of Sod2. Mechanistically, we show that Sod2 has a dual function in supporting OCCC tumorigenicity and metastatic spread. First, Sod2 maintains highly functional mitochondria, by scavenging O2•−, to support the high metabolic activity of OCCC. Second, Sod2 alters the steady-state ROS balance to drive H2O2-mediated migration. While this higher steady-state H2O2 drives prometastatic behavior, it also presents a doubled-edged sword for OCCC, as it pushed the intracellular H2O2 threshold to enable more rapid killing by exogenous sources of H2O2. Understanding the complex interaction of antioxidants and ROS may provide novel therapeutic strategies to pursue for the treatment of this histologic EOC subtype. Cancer Res; 75(22); 1–12. ©2015 AACR.

Epithelial ovarian cancer (EOC) is the fourth leading cause of death due to cancer in women and comprises distinct histological subtypes, which vary widely in their genetic profiles and tissues of origin. It is therefore imperative to understand the etiology of these distinct diseases. Ovarian clear cell carcinoma (OCCC), a very aggressive subtype, comprises >10% of EOCs. In the present study we show that mitochondrial superoxide dismutase (Sod2) is highly expressed in OCCC compared to other EOC subtypes. Sod2 is an antioxidant enzyme that converts highly reactive superoxide (O2•-) to hydrogen peroxide (H2O2) and oxygen (O2), and our data demonstrate that Sod2 is pro-tumorigenic and -metastatic in OCCC. Inhibiting Sod2 expression reduces OCCC ES-2 cell tumor growth and metastasis in a chorioallantoic membrane (CAM) model. Similarly, cell proliferation, migration, spheroid attachment and outgrowth on collagen, and Akt-phosphorylation are significantly decreased with reduced expression of Sod2. Mechanistically, we show that Sod2 has a dual function in supporting OCCC tumorigenicity and metastatic spread. First, Sod2 maintains highly functional mitochondria, by scavenging O2•-, to support the high metabolic activity of OCCC. Secondly, Sod2 alters the steady-state ROS balance to drive H2O2-mediated migration. While this higher steady-state H2O2 drives pro-metastatic behavior it also presents a doubled-edged sword for OCCC, as it pushed the intracellular H2O2 threshold to enable more rapid killing by exogenous sources of H2O2. Understanding the complex interaction of antioxidants and ROS may provide novel therapeutic strategies to pursue for the treatment of this histological EOC subtype.

Imatinib and other tyrosine kinase inhibitors (TKI) have improved treatment of chronic myelogenous leukemia (CML); however, most patients are not cured. Deeper mechanistic understanding may improve TKI combination therapies to better control the residu...

The therapeutic promise of microRNA in cancer has yet to be realized. In this study, we identified and therapeutically exploited a new role for miR-10b at the metastatic site which links its overexpression to tumor cell viability and proliferation. In ...

TMEM88 is a transmembrane protein that plays a crucial role in regulating human stem cell differentiation and embryonic development. However, its expression and clinicopathological significance in human neoplasms is unclear. In the current study, the e...