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 residual leukemic cell population. In analyzing our patients’ data, we found that many patients who otherwise responded well to imatinib therapy still showed variations in their BCR–ABL transcripts. To investigate this phenomenon, we applied a mathematical model that integrates CML and an autologous immune response to the patients’ data. We define an immune window or a range of leukemic loads for which the autologous immune system induces an improved response. Our modeling results suggest that, at diagnosis, a patient’s leukemic load is able to partially or fully suppress the autologous immune response developed in a majority of patients, toward the CML clone(s). Imatinib therapy drives the leukemic population into the “immune window,” allowing the patient’s autologous immune cells to expand and eventually mount an efficient recognition of the residual leukemic burden. This response drives the leukemic load below this immune window, allowing the leukemic population to partially recover until another weaker immune response is initiated. Thus, the autologous immune response may explain the oscillations in BCR–ABL transcripts regularly observed in patients on imatinib. Cancer Res; 75(19); 1–10. ©2015 AACR.

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 the protocol developed, we combined a miR-10b-inhibitory nanodrug with low-dose anthracycline to achieve complete durable regressions of metastatic disease in a murine model of metastatic breast cancer. Mechanistic investigations suggested a potent anti-proliferative, pro-apoptotic effect of the nanodrug in the metastatic cells, potentiated by a cell-cycle arrest produced by administration of the low-dose anthracycline. miR-10b was overexpressed specifically in cells with high metastatic potential, suggesting a role for this miRNA as a metastasis-specific therapeutic target. Taken together, our results implied the existence of pathways that regulate the viability and proliferation of tumor cells only after they have acquired the ability to grow at distant metastatic sites. As illustrated by miR-10b targeting, such metastasis-dependent apoptotic pathways would offer attractive targets for further therapeutic exploration.

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 expression and subcellular localizations of TMEM88 were assessed in 214 cases of non-small cell lung cancer (NSCLC). Notably, TMEM88 was highly expressed in the cytosol of ~60% NSCLC specimens examined. Higher expression of cytosolic TMEM88 in NSCLC correlated significantly with poor differentiation, high TNM stage, lymph node metastasis and inferior survival. In NSCLC cells displaying membrane-localized TMEM88, we observed an inhibition of canonical Wnt signaling due to interactions of TMEM88 with the Wnt pathway factor Dishevelled (DVLS). In contrast, NSCLC cells with cytosol-localized TMEM88 lacked effects on Wnt signaling. Cytosolic interactions of TMEM88 and DVLS increased the expression of phosphorylated, active forms of p38,GSK3β (Thr390) and Snail, thereby reducing the expression of the tight junction associated proteins ZO-1 and occludin, effects associated with enhanced invasive and metastatic cell characters. Importantly, attenuating the expression of cytosolic TMEM88 reduced metastatic prowess in xenograft models. Overall, our findings show how mislocalization of TMEM88 to the cytosol in NSCLC cells ablates its Wnt pathway regulatory properties, thereby promoting invasion and metastasis by activating the p38-GSK3β-Snail signaling pathway.