Abstract 1261: Nintedanib induces antitumor effects in triple-negative breast cancer cells by targeting SHP-1/p-STAT3-mediated signaling pathway
Authors: Liu Chun-Yu , Lee Chia-Han , Huang Chun-Teng , Chu Pei-Yi , Wang Wan-Lun , Tseng Ling-Ming , Shiau Chung-Wai , Chen Kuen-Feng 
Published: July 2016

Abstract
Background:
Triple-negative breast cancer (TNBC) is a heterogeneous and aggressive subtype that currently lack of specific targeted therapy. Previous studies have suggested that disturbing the oncogenic STAT3 signaling by activating a protein tyrosine phosphatase SHP-1 as a possible anti-cancer strategy. Our previous study also found that nintedanib (BIBF1120), a multi-kinase inhibitor that blocks mainly anti-angiogenic pathways and has been approved for idiopathic pulmonary fibrosis and for non-small cell lung cancer (in Europe), inhibits hepatocellular carcinoma cell growth independent of its anti-angiokinase activity (J Hepatology 2015). In this study, we tested nintedanib in TNBC cells and examined the underlying molecular mechanism by which nintedanib shows anti-TNBC effects.
Methods:
TNBC cell lines (MDA-MB-468, MDA-MB-231, HCC-1395) were used for in vitro studies. Cell viability was examined by MTT assay. Apoptosis was examined by flow cytometry and western blot. Signal transduction pathways in cells were assessed by western blot. Purified SHP-1 proteins or cells expressing deletion N-SH2 domain or D61A point mutants (SHP-1 mutants with constant open form conformations) were used to investigate the potential effects of nintedanib on SHP-1. In vivo efficacy of nintedanib was tested in nude mice bearing orthotopic breast cancer cells xenografts.
Results:
MTT assays revealed nintedanib induced anti-proliferation in the 3 TNBC cell lines. Sub-G1 flow cytometric and western blot analysis showed that nintedanib induced apoptosis in association with downregulation of p-STAT3 and its downstream proteins such as cyclin D1 in both dose and time-dependent manners. Overexpression of STAT3 suppressed nintedanib-mediated apoptosis in MDA-MB-231 cells. Nintedanib further increased SHP-1 activity in purified SHP-1 proteins, suggesting that nintedanib may directly affects SHP-1 activity for p-STAT3 inhibition. Moreover, either specific SHP-1 activity inhibitor or SHP-1 siRNA reduced the apoptotic effects of nintedanib on MDA-MB-231 and MDA-MB-468 cells, validating the role of SHP-1 activation in nintedanib-induced apoptosis. Furthermore, nintedanib-induced apoptosis was attenuated in TNBC cells expressing SHP-1 mutants with constant open form conformations, including deletion mutants of N-SH2 domain or D61A mutants, suggesting that the auto-inhibition structure of SHP-1 mediated the effect of nintedanib. Importantly, intraperitoneal injection of nintedanib showed antitumor activity, increased SHP-1 activity and p-STAT3 downregulation in MDA-MB-231 xenograft tumors.
Conclusions
Our results suggest that nintedanib induced anti-tumor effect by SHP-1 dependent STAT3 inhibition in human TNBC cells. These findings may provide new signaling pathway insight into the inhibition of TNBC growth by nintedanib.
Citation Format: Chun-Yu Liu, Chia-Han Lee, Chun-Teng Huang, Pei-Yi Chu, Wan-Lun Wang, Ling-Ming Tseng, Chung-Wai Shiau, Kuen-Feng Chen. Nintedanib induces antitumor effects in triple-negative breast cancer cells by targeting SHP-1/p-STAT3-mediated signaling pathway. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1261.