The HSP90 inhibitor KW-2478 depletes the malignancy of BCR/ABL and overcomes the imatinib-resistance caused by BCR/ABL amplification

Background: With the widespread clinical application of tyrosine kinase inhibitors (TKIs), an increasing number of chronic myeloid leukaemia (CML) patients have developed resistance or intolerance to TKIs. BCR/ABL is the oncoprotein of CML. HSP90 is an essential chaperone of BCR/ABL and plays an important role in protein folding and the function of BCR/ABL. Therefore, inhibiting the chaperone function of HSP90 may be an effective strategy for CML treatment and to overcome TKI resistance.

Methods: The effect of KW-2478 on CML cell viability, Apoptosis and cell cycle progression was detected by CCK-8 assay or flow cytometry. The levels of BCR/ABL, HSP90 and other signalling proteins were detected by western blots. The mitochondrial membrane potential was detected by flow cytometry combined with JC-1 staining. The interaction between BCR/ABL and HSP90α was detected by coimmunoprecipitation. The effect of KW-2478 on BCR/ABL carcinogenesis in vivo was investigated in CML-like mouse models.

Results: KW-2478 inhibited growth and induced Apoptosis of CML cells. KW-2478 inhibited the chaperone function of HSP90α and then weakened the BCR/ABL and MAPK signalling pathways. This treatment also caused an increase in p27 and p21 expression and a decrease in cyclin B1 expression, which led to G2/M phase arrest. The mitochondrial pathway was primarily responsible for KW-2478-induced Apoptosis. KW-2478 had a synergistic effect with imatinib in growth inhibition. Notably, KW-2478 had a stronger effect on growth inhibition, Apoptosis induction and cell cycle arrest of K562/G01 cells than K562 cells. KW-2478 could effectively prolong the mouse lifespan and alleviate disease symptoms in CML-like mouse models.

Conclusions: This finding demonstrated that KW-2478 had Anticancer properties in imatinib-sensitive and imatinib-resistant CML cells and illustrated the possible mechanisms. This study provides an alternative choice for CML treatment, especially for TKI-resistant patients with BCR/ABL amplification and TKI-intolerant patients.