OBJECTIVETo investigate the antitumor efficacy and mechanism of HSP90 inhibitor FW-04-806 against Bcr/Abl(+) leukemia K562 and HL60 cells and their mechanisms of action.

METHODSMTT assay was used to assess the proliferation-inhibiting effect of FW-04-806. Cell cycle was analyzed with propidium iodide by flow cytometry. Cell apoptosis was determined using the FITC mV apoptosis detection kit. Western blot was applied to reveal the protein expression of related proliferative and apoptotic signaling pathways. The changes of mitochondrial membrane potential were detected by flow cytometry. Protein-protein interactions was shown by co-immunoprecipitation. The level of mRNA was assessed by real-time RT-PCR.

RESULTSFW-04-806 obviously inhibited cell proliferation in the HL60, K562 and HL60/Bcr-Abl cell lines, with an IC50 of (30.89 ± 0.12) µmol/L, (9.76 ± 0.19) µmol/L and (8.03 ± 0.26) µmol/L, respectively (P<0.001). Compared with the vehicle group, the two increasing doses of FW-04-806 showed inhibition of tumor growth at a rate of (17.40 ± 0.34)% and (34.33 ± 5.00)%, respectively, in the K562 cell line groups (P=0.003), and (18.90 ± 1.45)% and (35.60 ± 3.55)% (P=0.001) in the HL60/Bcr-Abl cell line groups. FW-04-806 dissociated Hsp90/Cdc37 chaperon/co-chaperon complex, followed by degradation of the Hsp90 proteins through proteasome pathway without affecting mRNA expression. FW-04-806 induced apoptosis and led to G2/M arrest.

CONCLUSIONOur findings indicate that FW-04-806 displays potential antitumor effect by suppressing the proliferation and apoptosis in Bcr/Abl(+) leukemia cells in vivo.