Objective:To investigate the different expressions of heat shock protein 90β(HSP90β) mRNA and protein in all-trans retinoic acid(ATRA) sensitive leukemia cell line HL-60 and its resistant cell line HL60/ATRA in order to explore the effect of HSP90β on the ATRA multidrug resistance in leukemia.Methods:HL60/ATRA cell line was constructed by increasing ATRA concentration stepwisely and intermittently.The proliferation and sensitivity to anticancer drugs(VCR

CTX

VP-16

ADM) of HL60 and HL60/ATRA were tested by MTT assay.The cell cycle was analyzed using flow cytometry(FCM).The expression of HSP90β in HL60 cells and HL60/ATRA cells was detected with RT-PCR(reverse transcription PCR) and Western blot.Results:HL60/ATRA was successfully constructed.The transcription and protein expression of HSP90β in HL60/ATRA cells was higher than that of HL60 cells statistically(P<0.01).The drug resistant indexes of HL60/ATRA cells to VCR

CTX

VP-16 and ADM increased to 10.74

5.51

4.01 and 3.24

compared with HL60 cells respectively.Conclusion:ATRA could induce the high expression of HSP90 β in HL-60 cells.The sensitivity to anticancer drugs of HL60/ATRA induced by ATRA is decreased

but drug resistance is increased

which suggests that HSP90β may play an important role in the development of ATRA multidrug resistance.