Metastasis is the major reason of disease progression and poor prognosis in prostate cancer. Src family kinases (SFKs), including c-Src, Lyn and Fyn, are non-receptor tyrosine kinases that have been shown to play an essential role in castration resistance and metastasis in prostate cancer. Hypoxia, a typical hallmark of solid malignancies, is able to promote metastasis-associated functions. However, whether SFK members are upregulated under hypoxia is unclear. The current project will detect the impact of hypoxia on cell functions and molecular features in prostate cancer cells. For hypoxic exposure, prostate cancer cells were exposed to low oxygen tensions (1% O2) for varied durations (0, 2, 6, 24 h). To test cell migration, “wound-healing” assay was used. Cell invasion was detected by seeding cells into Matrigel-coated transwell chamber and cells on the bottom membranes were counted after treatment. Clonogenic assay was performed to test cell survival. At the molecular level, SFKs' phosphorylation in cancer cells and patient tissues was detected by Western blotting, and gene knockdown was accomplished by siRNA transfection. To detect the effects of Src inhibitors, cells were treated with saracatinib for indicated time periods. Phosphorylation of all three typical SFKs, e.g., c-Src, Lyn and Fyn, were highly expressed in prostate cancer patient tissues. At the cellular level, while short term hypoxic exposure (2-6 h) induced greater effects than prolonged hypoxia (24 h) in PC-3ML, these cellular functions were increased with 24 h hypoxic exposure in C4-2B cells. Further, hypoxia enhanced SFK phosphorylation in the pattern that was consistent with cell functions in both cell lines. Knockdown SRC, but not LYN or FYN, abolished hypoxia-induced invasion and p-SFK expression. Lastly, SFK inhibitor saracatinib showed stronger inhibition on functional behaviors facilitated under hypoxia than normal conditions. Our data show that hypoxia is able to enhance metastatic phenotypes by activating SFKs in prostate cancer cells. Interestingly, c-Src may be the most important signaling molecule for hypoxia-mediated behaviors. More importantly, SFK inhibitors are able to impair hypoxia-induced cell functions, suggesting their therapeutic potential by suppressing tumor metastasis that is driven under hypoxia in prostate cancer.

Citation Format: Yao Dai, Dietmar Siemann. Effects of hypoxia on Src family members' activity in prostate cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2441.