Platelet-Derived Growth Factor Receptor-α Regulates Proliferation of Gastrointestinal Stromal Tumor Cells With Mutations in KIT by Stabilizing ETV1

Abstract

Background & Aims In gastrointestinal muscles, KIT is predominantly expressed by interstitial cells of Cajal (ICC) and PDGFRA is expressed by so-called fibroblast-like cells. KIT and PDGFRA have been reported to be co-expressed in ICC precursors and gastrointestinal stromal tumors (GISTs), which originate from the ICC lineage. PDGFRA signaling has been proposed to stimulate growth of GISTs that express mutant KIT, but the effects and mechanisms of selective blockade of PDGFRA are unclear. We investigated whether inhibiting PDGFRA could reduce proliferation of GIST cells with mutant KIT via effects on the KIT-dependent transcription factor ETV1. Methods We studied 53 gastric, small intestinal, rectal, or abdominal GISTs collected immediately after surgery or archived as fixed blocks at the Mayo Clinic and University of California, San Diego. In human GIST cells carrying imatinib-sensitive and imatinib-resistant mutations in KIT, PDGFRA was reduced by RNA interference (knockdown) or inhibited with crenolanib besylate (a selective inhibitor of PDGFRA and PDGFRB). Mouse ICC precursors were retrovirally transduced to overexpress wild-type Kit. Cell proliferation was analyzed by methyltetrazolium, 5-ethynyl-2'-deoxyuridine incorporation, and Ki-67 immunofluorescence assays; we also analyzed growth of xenograft tumors in mice. Gastric ICC and ICC precursors, and their PDGFRA+ subsets, were analyzed by flow cytometry and immunohistochemistry in wild-type, Kit+/copGFP, Pdgfra+/eGFP and NOD/ShiLtJ mice. Immunoblots were used to quantify protein expression and phosphorylation. Results KIT and PDGFRA were co-expressed in 3%–5% of mouse ICC, 35%−44% of ICC precursors, and most human GIST samples and cell lines. PDGFRA knockdown or inhibition with crenolanib efficiently reduced proliferation of imatinib-sensitive and imatinib-resistant KIT+ETV1+PDGFRA+ GIST cells (half-maximal inhibitory concentration: IC50=5-32 nM), but not of cells lacking KIT, ETV1, or PDGFRA (IC50>230 nM). Crenolanib inhibited phosphorylation of PDGFRA and PDGFRB but not KIT. However, Kit overexpression sensitized mouse ICC precursors to crenolanib. ETV1 knockdown reduced KIT expression and GIST proliferation. Crenolanib downregulated ETV1 by inhibiting ERK-dependent stabilization of ETV1 protein and also reduced expression of KIT and PDGFRA. Conclusions In KIT-mutant GIST, inhibition of PDGFRA disrupts a KIT–ERK−ETV1−KIT signaling loop by inhibiting ERK activation. The PDGFRA inhibitor crenolanib might be used to treat patients with imatinib-resistant, KIT-mutant GIST.

COP1/DET1/ETS axis regulates ERK transcriptome and sensitivity to MAPK inhibitors

“…The cooperative oncogenic effects of ETV1 with KIT-or BRAF-activating mutations is in part through ETV1 protein stabilization. Therefore, MAPK pathway inhibition with either KIT or MEK inhibitors leads to rapid ETV1 degradation (15)(16)(17). This implicates the dynamic regulation of ETV1 protein stability as a critical mechanism to couple ERK activity to a downstream nuclear transcriptional response in GISTs and melanoma.…”

“…In GISTs, the ETS factor ETV1 is a lineage-specific master regulator that cooperates with KIT-and PDGFRA-activating mutations in pathogenesis (15)(16)(17)(18)(19). In cutaneous melanoma, ETV1 is recurrently amplified and cooperates with the BRAF V600E -activating mutation in oncogenesis (20,21).…”

Hyperglycemia Increases Interstitial Cells of Cajal via MAPK1 and MAPK3 Signaling to ETV1 and KIT, Leading to Rapid Gastric Emptying

“…1 ICCs play a central role in gastrointestinal motility by generating electrical slow waves underlying phasic contractile activity, mediating nerve-muscle interactions and by setting smooth muscle membrane potential and tone. 1,2 ICCs differentiate from embryonic 3 and adult stem cells (ICC-SCs) 4,5 in response to the interdependent actions of the ets family transcription factor ETV1, a master regulator of ICC fate, 6–8 and KIT ligand (KITL, also known as stem cell factor) signaling via the receptor tyrosine kinase KIT. 3,9 …”

Expression of CAF-Related Proteins Is Associated with Histologic Grade of Breast Phyllodes Tumor

“…Sunitinib, a US Food and Drug Administration- (FDA-) approved PDGFR inhibitor, is currently used in the treatment of advanced renal cell carcinoma [37], advanced progressive pancreatic neuroendocrine tumor [38], and advanced radioiodine refractory thyroid carcinoma [39]. Furthermore, ongoing preclinical trials are testing the therapeutic effect of another PDGFR inhibitor, imatinib mesylate, in gastrointestinal stromal tumor [40, 41] and in vitro and in vivo studies of malignant peripheral nerve sheath tumors have shown promising results [42]. Therefore, inhibition of PDGFR in PT might be a potential therapeutic strategy.…”