Identification of Gαi3 as a promising target for osteosarcoma treatment
Zheng-jun Bian, Huajian Shan, Yun-Rong Zhu, Ce Shi, Min‐Bin Chen, Yumin Huang, Xiaodong Wang, Xiaozhong Zhou, Cong Cao
Abstract
Sustained activation of multiple receptor tyrosine kinases (RTKs) simultaneously is vital for tumorigenesis and progression of osteosarcoma (OS). Gi proteins recruitment to various RTKs mediates downstream oncogenic signaling activation. The expression, functions and underlying mechanisms of Gi3 in human OS were examined. Expression of Gi3 is robustly elevated in human OS tissues and is correlated with a poor overall survival. In patient-derived primary OS cells and immortalized lines (MG63 and U2OS), Gi3 depletion, by shRNA and CRISPR/Cas9 strategies, robustly suppressed cell viability, proliferation and migration, while provoking G1-S arrest and apoptosis activation. Conversely, Gi3 overexpressing ectopically can accelerate proliferation and migration of OS cells. In OS cells, Gi3 immunoprecipitated with VEGFR2, FGFR, PGDFR and EGFR, mediating downstream cascade transduction. Akt-mTOR activation in primary OS cells was potently inhibited by Gi3 shRNA, knockout or dominant negative mutation, but augmented after Gi3 overexpression. In vivo studies showed that Gi3 shRNA AAV (adeno-associated viruses) intratumoral injection largely inhibited the growth of subcutaneous xenografts of primary OS cells. Moreover, the growth of the Gi3-knockout primary OS xenografts was much slower than that of OS xenografts with empty vector. In Gi3-depleted OS xenografts tissues, Gi3 downregulation and Akt-mTOR inactivation were detected. Taken together, overexpressed Gi3 mediates RTK-Akt signaling to drive OS progression.