Role of mTORC2 and nitric oxide in bladder cancer invasion.

Abstract

504 Background: In the United States, bladder cancer is the fourth most common cancer, with an estimated 79,000 new diagnoses and 17,000 deaths in 2017, and the eleventh most common cancer worldwide. The key driver of bladder cancer stage progression is tumor cell invasion which has limited response to current chemotherapy options and hence, newer therapies directed against invasion are key to improving the treatment of bladder cancer. Our laboratory has identified mammalian target of rapamycin complex 2 (mTORC2) as a driver of bladder cancer cell invasion. We have also recently shown that arginine, the nitric oxide (NO) precursor, is implicated in bladder cancer progression. We evaluated the interaction between these two pathways to promote invasion. Methods: Expression of inducible and endothelial nitric oxide synthases (iNOS and eNOS) in FFPE tissue sections of progressive disease was assessed by IHC and correlated with histopathology, progression and stage based on moderate to strong expression (2+, 3+) compared to absent to weak expression (0, 1+).We utilized gene silencing methods and NOS inhibitors and NO scavenger for effects on bladder cancer invasion and migration. We assessed mTORC2 pathway activity and NOS levels in invasive cell tip protrusions called “invadopodia” and evaluated if mTORC2 regulates NOS localization and/or activity. We used a novel zebrafish model to characterize the effects of mTORC2 and NO on bladder cancer metastases. Results: We found that eNOS and iNOS are elevated in invasive human bladder tumors and cell lines and their ablation reduces bladder cancer cell migration and invasion. mTORC2 silencing can affect levels of iNOS and eNOS in bladder cancer cell lines. Silencing of mTORC2, eNOS or iNOS reduced metastases of bladder cancer cells within zebrafish. Conclusions: mTORC2 pathway is a key driver of bladder cancer invasion and metastases by regulating the NO pathway and both mTORC2 and NO can be targets for bladder cancer therapy, which would benefit patient outcomes.