PDGFRA and gastrointestinal stromal tumor: Because PDGFC is not known to activate PDGFR-β/β, these results suggested that CAF-mediated PDGFC secretion affects both PDGFR-α/α homo-dimerization and PDGFR-α/β hetero-dimerization, supporting our previous finding that CAF-mediated PDGFC secretion enhances GIST progression and metastasis.