Identification of Gαi3 as a promising target for osteosarcoma treatment

Sustained activation of multiple receptor tyrosine kinases (RTKs) simultaneously is vital for tumorigenesis and progression of osteosarcoma (OS). G alpha i proteins recruitment to various RTKs mediates downstream oncogenic signaling activation. The expression, functions and underlying mechanisms of G alpha i3 in human OS were examined. Expression of G alpha i3 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), G alpha i3 depletion, by shRNA and CRISPR/Cas9 strategies, robustly suppressed cell viability, proliferation and migration, while provoking G1-S arrest and apoptosis activation. Conversely, G alpha i3 overexpressing ectopically can accelerate proliferation and migration of OS cells. In OS cells, G alpha i3 immunoprecipitated with VEGFR2, FGFR, PGDFR and EGFR, mediating downstream cascade transduction. Akt-mTOR activation in primary OS cells was potently inhibited by G alpha i3 shRNA, knockout or dominant negative mutation, but augmented after G alpha i3 overexpression. In vivo studies showed that G alpha i3 shRNA AAV (adeno-associated viruses) intratumoral injection largely inhibited the growth of subcutaneous xenografts of primary OS cells. Moreover, the growth of the G alpha i3-knockout primary OS xenografts was much slower than that of OS xenografts with empty vector. In G alpha i3-depleted OS xenografts tissues, G alpha i3 downregulation and Akt-mTOR inactivation were detected. Taken together, overexpressed G alpha i3 mediates RTK-Akt signaling to drive OS progression.

Automated summary

Overexpression of G alpha i3 protein promotes tumorigenesis and progression of osteosarcoma by mediating RTK-Akt signaling.