Inhibition of integrin β3, a binding partner of kallistatin, leads to reduced viability, invasion and proliferation in NCI-H446 cells.

Yong Diao,Suqiu Pang,Shulan Zeng,Xiaoping Huang,Guoquan Wang,Xiaolan Xie,Huiyong Yang,Junsheng Lin,Xiao Wang

doi:10.1186/s12935-016-0365-7

Yong Diao, Suqiu Pang + Show 7 more

Open Access

https://doi.org/10.1186/s12935-016-0365-7

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Abstract

BackgroundKallistatin is a serine proteinase inhibitor and heparin-binding protein. It is considered an endogenous angiogenic inhibitor. In addition, multiple studies demonstrated that kallistatin directly inhibits cancer cell growth. However, the molecular mechanisms underlying these effects remain unclear.MethodsPull-down, immunoprecipitation, and immunoblotting were used for binding experiments. To elucidate the mechanisms, integrin β3 knockdown (siRNA) or blockage (antibody treatment) on the cell surface of small the cell lung cancer NCI-H446 cell line was used.ResultsInterestingly, kallistatin was capable of binding integrin β3 on the cell surface of NCI-H446 cells. Meanwhile, integrin β3 knockdown or blockage resulted in loss of antitumor activities induced by kallistatin. Furthermore, kallistatin suppressed tyrosine phosphorylation of integrin β3 and its downstream signaling pathways, including FAK/-Src, AKT and Erk/MAPK. Viability, proliferation and migration of NCI-H446 cells were inhibited by kallistatin, with Bcl-2 and Grb2 downregulation, and Bax, cleaved caspase-9 and caspase 3 upregulation.ConclusionsThese findings reveal a novel role for kallistatin in preventing small cell lung cancer growth and mobility, by direct interaction with integrin β3, leading to blockade of the related signaling pathway.

Highlights

Kallistatin is a serine proteinase inhibitor and heparin-binding protein
We recently demonstrated that kallistatin inhibits proliferation of lung cancer cells and enhances apoptosis in vitro, inhibiting lung cancer in a subcutaneous NCI-H446 xenograft model by reducing tumor cell angiogenesis and proliferation [23]
Integrin β3 is a kallistatin binding protein We selected NCI-H446 cells as target cells to identify kallistatin-binding partners because they were sensitive to kallistatin as assayed on small cell lung cancer cell viability and proliferation

Summary

Introduction

Kallistatin is a serine proteinase inhibitor and heparin-binding protein. It is considered an endogenous angiogenic inhibitor. Integrins are transmembrane receptors composed of two subunits, α and β chains They comprise a large family of cell surface receptors, with more than 18 α subunit and 8 β subunit isoforms identified in mammals. As an inducer of the Ras/MEK/ERK pathway, growth factor receptor-bound protein 2 (Grb2) is crucial for regulating cell proliferation and tumorigenesis. Upon activation of EGFR or other RTKs, Grb recruits Sos to the membrane to form the Grb2Sos complex, which is crucial for signal transduction, sequentially leading to Ras/MEK/ERK activation [11,12,13,14]

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