PDGFRA and growth hormone-producing pituitary gland neoplasm: To quantify the differential expression between tumor subtypes and imatinib targets, we evaluated protein expression of c-Kit VEGF, PDGFR-α, and PDGFR-β in somatotropinomas (n = 27), NFPA (n = 27), prolactinomas (n = 4), and normal pituitaries (n = 9) using western blotting (Figure 5).