Abstract A258: Combined blockade of Src kinase and epidermal growth factor receptor synergistically inhibits growth of pancreas cancer

Abstract

Abstract The failure of conventional chemotherapeutic regimes to produce any meaningful impact on survival in patients with pancreatic cancer highlights a desperate need for novel treatment strategies. The purpose of this study was to translate the current understanding of activated tyrosine kinase signaling pathways in pancreas cancer into improved patient therapies by targeting two tyrosine kinases, the epidermal growth factor receptor (EGFR) and the non-receptor Src kinase, which act in complementary pathways. The biochemical effects of individual and combined drug treatment with dasatinib (Sprycel, BMS-354825), a potent Src kinase inhibitor, erlotinib (Tarceva, OSI-774), a tyrosine kinase inhibitor to EGFR and the nucleoside analog gemcitabine were examined in pancreas cancer cell lines in vitro and in vivo. IC50 for dasatinib (DTB), erlotinib and gemcitabine was determined by the MTT proliferation assay against 9 human pancreas cancer cell lines, and sensitive and resistant cell lines were identified. In vitro regulation of cell motility, proliferation, survival, migration, invasion and in vivo tumor growth inhibition was determined. Expression of Ki67, cleaved caspase 3, phosphorylated Src and AKT in tumor xenografts was determined following exposure to combination of drugs. The combined inhibition of Src with DTB and EGFR with erlotinib results in cooperative attenuation of cell migration, invasion, proliferation and increases in apoptosis of pancreatic cancer cells. Combined inhibition of Src and EGFR also results in cooperative inhibition of multiple signaling pathways including FAK, AKT, Stat3, ERK, JNK, MAPK and decreases cyclin D1 at concentrations that are ineffective as individual agents. The addition of gemcitabine enhances the effects of combined inhibition of Src and EGFR compared to that seen with individual agents alone or in double combination. Mice with tumor xenografts of BxPC3 (sensitive cell line) and Panc1 (resistant cell line) cells treated with DTB, erlotinib or gemcitabine either individually or as two drug or three drug combinations showed that the most effective in vivo anti-tumor effects were seen with the triple combination of DTB, erlotinib and gemcitabine even in xenografts of resistant pancreatic cells. Pharmacological inhibition of EGFR and Src, in addition to gemcitabine treatment, results in cooperative inhibition of pancreatic tumor cell growth and appears to overcome resistance of single and double agent therapy. These results show that activation of Src and EGFR signaling pathways is evident in pancreas cancer and may be a driver of poor prognosis and chemotherapy resistance and provide a rationale for combination therapy with erlotinib, DTB and gemcitabine in clinical trials of pancreas cancer. Citation Information: Mol Cancer Ther 2009;8(12 Suppl):A258.