Hong Zhang

SOD1 is known as the major cytoplasmic superoxide dismutase and an anticancer target. However, the role of SOD1 in cancer is not fully understood. Herein we describe the generation of an inducible Sod1 knockout in KRAS-driven NSCLC mouse model. Sod1 knockout markedly reduces tumor burden in vivo and blocks growth of KRAS mutant NSCLC cells in vitro. Intriguingly, SOD1 is enriched in the nucleus and notably in the nucleolus of NSCLC cells. The nuclear and nucleolar, not cytoplasmic, form of SOD1 is essential for lung cancer cell proliferation. Moreover, SOD1 interacts with PeBoW complex and controls its assembly necessary for pre-60S ribosomal subunit maturation. Mechanistically, SOD1 regulates co-localization of PeBoW with and processing of pre-rRNA, and maturation of cytoplasmic 60S ribosomal subunits in KRAS mutant lung cancer cells. Collectively, our study unravels a nuclear SOD1 function essential for ribosome biogenesis and proliferation in KRAS-driven lung cancer.

Hepatocellular carcinoma (HCC) is a male‐dominant cancer, and androgen receptor (AR) has been linked to the pathogenesis of HCC. However, AR expression and its precise role in HCC remain controversial. Moreover, previous antiandrogen and anti‐AR clinical trials in HCC failed to demonstrate clinical benefits. In this study, we found that AR is overexpressed in the nucleus of approximately 37% of HCC tumors, which is significantly associated with advanced disease stage and poor survival. AR overexpression in HCC cells markedly alters AR‐dependent transcriptome, stimulates oncogenic growth, and determines therapeutic response to enzalutamide, a second generation of AR antagonist. However, AR inhibition evokes feedback activation of AKT‐mTOR (mechanistic target of rapamycin) signaling, a central regulator for cell growth and survival. On the other hand, mTOR promotes nuclear AR protein expression by restraining ubiquitin‐dependent AR degradation and enhancing AR nuclear localization, providing a mechanistic explanation for nuclear AR overexpression in HCC. Finally, cotargeting AR and mTOR shows significant synergistic anti‐HCC activity and decreases tumor burden by inducing apoptosis in vivo. Conclusion: Nuclear AR overexpression is associated with the progression and prognosis of HCC. However, enzalutamide alone has limited therapeutic utility attributed to feedback activation of the AKT‐mTOR pathway. Moreover, mTOR drives nuclear AR overexpression. Cotargeting AR and mTOR is a promising therapeutic strategy for HCC. (Hepatology 2018;67:2271‐2286).