To further elucidate whether the effect of nintedanib on SHP-1 is dependent on its angiokinase inhibition activity, we developed a novel kinase-independent derivative of nintedanib, 螖N. HCC cell lines were treated with nintedanib or its derivative (螖N) and apoptosis, signal transduction, and phosphatase activity were analyzed. Purified SHP-1 proteins or HCC cells expressing deletion N-SH2 domain or D61A point mutants were used to investigate the potential effect of nintedanib on SHP-1. In vivo efficacy was determined in nude mice with HCC subcutaneous xenografts (n 猢?#xA0;8 mice).
Nintedanib induced anti-proliferation in HCC cell lines by targeting STAT3. Ectopic STAT3 abolished nintedanib-mediated apoptosis in HCC cells. Nintedanib further activated SHP-1 in purified SHP-1 proteins suggesting that nintedanib directly affects SHP-1 for STAT3 inhibition. HCC cells or recombinant SHP-1 proteins expressing deletion of N-SH2 domain or D61A mutants restored the activity of nintedanib suggesting that the auto-inhibition structure of SHP-1 was relieved by nintedanib. Although 螖N only retained the backbone of nintedanib without kinase activity, 螖N still induced substantial anti-HCC activity in vitro and in vivo by targeting STAT3.
Nintedanib induced significant anti-HCC activity independent of angiokinase inhibition activity in a preclinical HCC model by relieving autoinhibition of SHP-1. Our findings provide new mechanistic insight into the inhibition of HCC growth by nintedanib.