Abstract B86: HSP90 is a promising target in gemcitabine and 5-fluorouracil resistant pancreatic cancer

Abstract

Abstract Purpose: Pancreatic cancer (PC) is a deadly disease. Chemotherapy options are limited to gemcitabine and 5-fluorouracil (5-FU). The molecular profile of PC offers several growth receptors (epidermal growth factor receptor [EGFR], insulin-like growth factor 1 receptor [IGF-1R]) and tyrosine kinases (AKT and MAPK) as promising therapy targets. EGFR, IGF-1R, AKT and MAPK are dependent upon the heat shock protein 90 (HSP90) to gain the mature functional active protein form hence HSP90 represents a promising therapy target in PC. Functional inhibition of HSP90 has the advantage of disruption of many oncogenic signalling pathways simultaneously. The aim of this study was evaluate the efficacy of different HSP90 inhibitors in gemcitabine and 5-FU resistant PC. Material and Methods: Human gemcitabine and 5-FU resistant pancreatic cancer cell lines 5061, 5072 and 5156 were generated and brought in to culture from patients who were operated for PC at our institution and received gemcitabine as adjuvant therapy. The commercial L3.6pl cell line served as a control. Antiproliferative efficacy of three different HSP90 inhibitors (17AAG, 17DMAG and 17AEPGA) was evaluated by the MTT assay. Alterations in signalling pathway effectors and apoptosis upon HSP90 inhibition was determined by western blot analysis (WB). Results: The cell lines 5061, 5072 and 5156 were resistant to gemcitabine and 5-FU. In contrast, 17AAG and the water-soluble derivates 17DMAG and 17AEPGA displayed high antiproliferative activity in all tested cell lines. The calculated GI50 was below 1 µM. In line with the proliferation inhibition in the MTT assay, the expression of EGFR, IGF-1R, AKT and MAPK was significantly down regulated under HSP90 inhibition as verified inWB. In contrast, HSP70 and HSP27 were upregulated in all cell lines under HSP90 inhibition. Apoptosis was an early event in all three HSP90 inhibited cell lines and determined by CASPASE-3 and poly (ADP-ribose) polymerase assay. In contrast, gemcitabine treated cells did not show significant apoptosis. Conclusions: Functional inhibition of HSP90 disrupts multiple signalling cascades in gemcitabine and 5-FU resistant PC. Water-soluble 17DMAG is equally effective as 17AAG. The up-regulation of HSP70 and HSP27 indicates counter regulation of tumor cells to prevent apoptosis and should be addressed when considering HSP90 inhibition in PC. Citation Information: Mol Cancer Ther 2009;8(12 Suppl):B86.