Activated tyrosine kinases in gastrointestinal stromal tumor with loss of KIT oncoprotein expression. Issue 23 (2nd December 2018)

• Record Type: Journal Article
• Authors: Tu, Yuqing; Zuo, Rui; Ni, Nan; Eilers, Grant; Wu, Duolin; Pei, Yuting; Nie, Zuoming; Wu, Yeqing; Wu, Yuehong; Ou, Wen-Bin
• Is Part Of: Cell cycle. Volume 17:Issue 23(2018)
• Page Start: 2577
• Page End: 2592
• Publication Date: 2018-12-02
• Subjects: AXL -- EGFR -- FAK -- loss of KIT -- GIST; Cell cycle -- Periodicals; 571.84377
• DOI: 10.1080/15384101.2018.1553335
• Languages: English
• ISSNs: 1538-4101

Abstract

ABSTRACT: Oncogenic KIT or PDGFRA receptor tyrosine kinase (TK) mutations are compelling therapeutic targets in gastrointestinal stromal tumors (GISTs), and the KIT/PDGFRA kinase inhibitor, imatinib, is the standard of care for patients with metastatic GIST. However, approximately 10% of KIT-positive GIST metastases lose KIT expression at the time of clinical progression during imatinib therapy. In the present report, we performed TK-activation screens, using phosphotyrosine-TK double immunoaffinity purification and mass spectrometry, in GIST in vitro models lacking KIT expression. These studies demonstrated tyrosine-phosphorylated EGFR, AXL, and EPHA2 in four of six KIT-negative GIST lines (GIST62, GIST522, GIST54, GIST226, GIST48B, and GIST430B), and tyrosine-phosphorylated focal adhesion kinase (FAK) in each of the six KIT-negative lines. AXL expression was strong in KIT-negative or -weak clinical GIST samples that were obtained from progressing metastases during imatinib therapy. AXL knockdown inhibited viability in three KIT-negative GIST cell lines (GIST62, GIST54, and GIST522), but not in an AXL-negative, KIT-positive GIST control cell line (GIST430). AXL inhibition by R428, a specific AXL kinase inhibitor, reduced viability in AXL-activated GIST54. AXL knockdown in GIST62, GIST522, and GIST54 was accompanied by an increase in p21, p27, and p53 expression. By contrast, gefitinib-mediated EGFR inhibition, PF562271-mediated FAK inactivation, and shRNA-mediated knockdowns of EPHA2 and FAK had no effect on viability or colony formation of the KIT-negative GISTs. These findings highlight the potential relevance of AXL/p53 signaling as a therapeutic target in a subset of GISTs that have lost KIT oncoprotein expression.