The rest of the cells were also inhibited in anchorage-independent growth assays after NVP-AUY922 treatment (0.1 μM). Primary cultures from colorectal tumors were also inhibited by both Hsp90 inhibitors, even though the half maximal inhibitory concentration (IC50) was higher than the IC50 of the cell lines. Interestingly, the primary culture HCUVA-CC-34 was inhibited GDC-0068 cell line only 43.8 ± 4.4% with 17-AAG and 40.4 ± 7.8% with NVP-AUY922 at the maximum concentration

used of 10 μM in anchorage-dependent growth assays ( Figure 1, E and F). In addition, anchorage-independent growth of the HCUVA-CC-34 primary cell culture was moderately inhibited by 17-AAG and by NVP-AUY922 only at the highest concentration used ( Figure 2, C and D). We performed

cell cycle analyses and found that pancreatic carcinoma IMIM-PC-2 cells accumulated in the G1 phase of the cell cycle upon 24 hours of 17-AAG or NVP-AUY922 treatment, followed by an accumulation in the sub-G1 phase, indicative of cell death, after 48 or 72 hours of Hsp90 inhibitor treatment (Figure 3, A and C). However, pancreatic carcinoma IMIM-PC-1 cells accumulated in the G2/M phase of the cell cycle, followed by an increase in the sub-G1 phase with both inhibitors ( Figure 3, A and C). The pancreatic cell line CFPAC-1 accumulated in the G2/M phase and only slightly in sub-G1, Selleckchem PLX-4720 and PANC-1 did not experience any change upon 17-AAG exposure ( Figure 3A), suggesting that both CFPAC-1 and PANC-1 cells are unresponsive to 17-AAG but sensitive to NVP-AUY922 treatment. Conversely, when these cells were treated with NVP-AUY922, they accumulated considerably in the G2/M phase of the cell cycle

followed by an increase in the sub-G1 phase ( Figure 3C). Colorectal carcinoma cell lines HT-29 and SW620 accumulated in the G2/M and sub-G1 phases upon treatment with 17-AAG or NVP-AUY922. Especially, the G2/M arrest induced by 17-AAG treatment was very noticeable in HT29 cells ( Figure 3, B and D). LoVo cells mainly accumulated in the sub-G1 phase with both inhibitors, whereas Caco-2 cells barely accumulated in the G2/M phase with 17-AAG but instead were arrested in this phase and also accumulated in sub-G1 after NVP-AUY922 treatment. This indicates Adenylyl cyclase that LoVo cells are sensitive to 17-AAG and NVP-AUY922, but Caco-2 cells are practically unresponsive to 17-AAG but sensitive to NVP-AUY922 treatment. To determine whether 17-AAG and NVP-AUY922 were able to downregulate Hsp90 protein clients such as EGFR family members, we performed Western blot analyses and found that indeed EGFR and HER2 down-regulation could be detected within 4 hours of 17-AAG treatment in sensitive cell lines but not in cell lines resistant to 17-AAG (Figure 4A). In addition, EGFR and HER2 receptors were even more efficiently downregulated within 4 hours of NVP-AUY922 exposure ( Figure 4A).