Molecular Markers for Novel Therapeutic Strategies in Pancreatic Endocrine Tumors

Objectives: Pancreatic endocrine tumors (PETs) share numerous features with gastrointestinal neuroendocrine (carcinoid) tumors. Targets of novel therapeutic strategies previously assessed in carcinoid tumors were analyzed in PETs (44 cases). Methods: Activating mutations in EGFR, KIT, and PDGFRA and non-response mutations in KRAS were evaluated. Copy number of EGFR and HER-2/neu was quantified by fluorescence in situ hybridization. Expression of EGFR, PDGFRA, VEGFR1, TGFBR1, Hsp90, SSTR2A, SSTR5, IGF1R, mTOR, and MGMT was measured immunohistochemically. Results: Elevated EGFR copy number was found in 38% of cases but no KRAS nonresponse mutations. VEGFR1, TGFBR1, PDGFRA, SSTR5, SSTR2A, and IGF1R exhibited the highest levels of expression in the largest percentages of PETs. Anticancer drugs BMS-754807 (selective for IGF1R/IR), 17-(allylamino)-17- demethoxygeldanamycin (17-AAG, targeting Hsp90), and axitinib (directed toward VEGFR1-3/PDGFRA-B/KIT) induced growth inhibition of human QGP-1 PET cells with IC50 values (nM) of 273, 723, and 743, respectively. At growth-inhibiting concentrations, BMS-754807 inhibited IGF1R phosphorylation; 17-AAG induced loss of EGFR, IGF1R, and VEGFR2; and axitinib increased p21(Waf1/Cip1) (CDKN1A) expression without inhibiting VEGFR2 phosphorylation. Conclusions: Results encourage further research into multidrug strategies incorporating inhibitors targeting IGF1R or Hsp90 and into studies of axitinib combined with conventional chemotherapeutics toxic to tumor cells in persistent growth arrest.