In this report, we sought to determine the effects of 17-AAG and NVP-AUY922 in a panel of pancreatic exocrine adenocarcinoma and colorectal Target Selective Inhibitor Library carcinoma cell lines and in colorectal primary cultures derived from

tumors excised to patients to find predictive markers of response to such Hsp90 inhibitors, aiming at down-regulation of signaling pathways initiated by HER receptors. We have found some cell lines resistant to 17-AAG but still responsive to NVP-AUY922. We have determined that ABC transporters such as Pgp (Mdr-1), MRP1, and BCRP1 are not involved in 17-AAG resistance and that although the absence of NQO1 is a feature of several pancreatic and colorectal resistant cancer cell lines, its depletion is not enough to generate a resistance phenotype to 17-AAG. Moreover, NQO1 is related to resistance only to 17-AAG but not to other nonbenzoquinone Hsp90 inhibitors BMS-907351 such as NVP-AUY922, which is a more potent inhibitor in these cellular models. Indeed, we demonstrate in this report that NVP-AUY922 is able to potentiate the effect of other antitumor drugs in cells that do not respond to these agents. 17-AAG (tanespimycin), NVP-AUY922, AZD6244, and NVP-BEZ235 were purchased from ChemieTek (Indianapolis, IN) and ES936 and gemcitabine from Tocris Bioscience (Bristol, United Kingdom), and each one of them is dissolved in DMSO or water. Propidium iodide,

crystal violet, iodonitrotetrazolium violet, 4-hydroxycoumarin (dicumarol), 2,6-dichlorophenol-indophenol (DCPIP), and oxaliplatin were purchased from Sigma-Aldrich (St Louis, MO). The human pancreatic carcinoma cell lines Hs 766 T, BxPC-3, HPAF-II, CFPAC-1, PANC-1, IMIM-PC-1, IMIM-PC-2, and RWP-1, the human colorectal carcinoma cell lines HT-29, SW620, SW480, HCT-15, HCT 116, LoVo, Caco-2, DLD-1, LS 174 T, and Colo 320 HSR (Colo 320), and the glioblastoma cell line T98G were obtained from the American Type Culture Collection (Manassas, VA) or the IMIM cell line repository (Instituto

Hospital del Mar de Investigaciones Médicas (IMIM), Barcelona, Spain). The HGUE-C-1 cell line was kindly donated by Dr Miguel Saceda (Hospital General Universitario de Elche, Elche, Spain). Primary cell culture Decitabine molecular weight samples were obtained from colorectal tumors excised to patients at the Hospital Clínico Universitario Virgen de la Arrixaca (Murcia, Spain) or the Hospital General Universitario Santa Lucía (Cartagena, Spain). Surgical samples were digested with 1.5 U/ml dispase, 0.09 mg/ml collagenase II, 0.1 mg/ml pronase E, and 45 U/ml hyaluronidase and incubated at 37°C for 30 minutes. Fragments were incubated with RBC lysis solution (GeneAll Biotechnology, Seoul, Korea) for 10 minutes to eliminate erythrocytes, washed with phosphate-buffered saline (PBS) filtered through a 70-μm mesh, washed with PBS and harvested in Dulbecco’s modified Eagle’s medium–F12 containing 20% heat-inactivated FBS, 2 mM glutamine, 10 μg/ml insulin–5.