CRKL plays a pivotal role in tumorigenesis of head and neck squamous cell carcinoma through the regulation of cell adhesion

Hiroko Yanagi,Lei Wang,Hiroshi Nishihara,Taichi Kimura,Mishie Tanino,Teruki Yanagi,Satoshi Fukuda,Shinya Tanaka

doi:10.1016/j.bbrc.2011.12.142

Abstract

The signaling adapter protein CRK is an indispensable molecule involved in regulating the malignant potential of human cancers. CRK-like (CRKL) is a hematopoietic cell-dominant homologue of CRK that is reported to be phosphorylated by BCR–ABL tyrosine kinase in chronic myelogenous leukemia patients, but its biological function in non-hematopoietic tumors remains unclear. In this study, we explored the tumorigenic role of CRKL in head and neck squamous cell carcinoma (HNSCC) in vitro and in vivo. Immunoprecipitation analysis of HNSCC cell line, HSC-3 cells, showed that the dominant binding partner for C3G was CRKL, not CRK. To clarify the molecular function of CRKL, we established lentiviral shRNA-mediated CRKL-knockdown HNSCC cell lines. In CRKL-knockdown HSC-3 and HSC-4 cells, cell growth and motility were diminished compared to control cells. Cell adhesion assays showed that cell attachment onto both fibronectin- and collagen-coated dishes was significantly suppressed in CRKL-knockdown HSC-3 cells, while no significant change was observed for poly-l-lysine-coated dishes. Immunofluorescence staining revealed that focal adhesion was reduced in CRKL-knockdown HSC-3 cells. With a pulldown assay, CRKL-knockdown HSC-3 cells showed decreased amounts of active Rap1 compared to control cells. Moreover, in an in vivo assay, tumor formation of CRKL-knockdown HSC-3 cells in nude mice was significantly abrogated. Our results indicate that CRKL regulates HNSCC-cell growth, motility, and integrin-dependent cell adhesion, suggesting that CRKL plays a principal role in HNSCC tumorigenicity.

Highlights

IntroductionSignaling adaptor protein CRK, which carries Src homology (SH) 2 and SH3 domains, was originally identified as avian sarcoma virus CT10 (chicken tumor 10)
Signaling adaptor protein CRK, which carries Src homology (SH) 2 and SH3 domains, was originally identified as avian sarcoma virus CT10-encoding oncogene product v-Crk [1], and was followed by isolation of its mammalian homologues, CRKI, CRKII and CRKL (CRK-like) [2,3]
In addition to the histological analysis, CRKL and CRKI/II expression was found in all head and neck squamous cell carcinoma (HNSCC) cell lines examined

Summary

Introduction

Signaling adaptor protein CRK, which carries Src homology (SH) 2 and SH3 domains, was originally identified as avian sarcoma virus CT10 (chicken tumor 10). -encoding oncogene product v-Crk [1], and was followed by isolation of its mammalian homologues, CRKI, CRKII and CRKL (CRK-like) [2,3]. The CRKL protein has high sequence identity within the SH2 and SH3 domains of CRKII, despite their distinct gene locations, and was identified as a major substrate of the BCR-ABL tyrosine kinase in chronic myelogenous leukemia [14,15]. A previous report showed that phosphorylated CRKL activates Ras and Jun kinase signaling pathways and transforms mouse fibroblasts in a BCR-ABL-dependent fashion [16]

Methods

Results

Conclusion