Dual inhibition of STAT3 and STAT5 may overcome imatinib resistance in chronic myeloid leukemia.

BACKGROUND

Clinical outcome of patients with chronic myeloid leukemia (CML) has improved dramatically since the introduction of tyrosine kinase inhibitors such as imatinib mesylate (IM). However, approximately 20-30% of patients experience IM resistance. SH-4-54, which targets the SH2 domains of both proteins STAT3 and STAT5, has been reported to exhibit anticancer activity in solid tumors. However, the roles of SH-4-54 in CML remain unclear. The aim was to explore whether SH-4-54 could overcome IM resistance and identify novel targets for CML.

METHODS

Cell viability was measured by CCK-8 assays after treatment of K562 and K562R cells with different concentrations of SH-4-54. Annexin V-FITC and PI were applied to assess the effects of SH-4-54 on cell apoptosis. Effects of SH-4-54 on the expression of proteins downstream of BCR::ABL1 were assessed by western blotting (WB). Effects of SH-4-54 on gene expression profile of CML cells were analyzed by Next generation sequence (NGS).

RESULTS

SH-4-54 inhibited the growth of CML cell lines with increasing concentration. SH-4-54 cytotoxic effects correlated with a significant induction of apoptosis. The results of WB analysis showed the downstream proteins of BCR::ABL1, such as STAT3 and STAT5, decreased after SH-4-54 treatment; moreover, the phosphorylation of both proteins were inhibited in dose-dependent manner. Using NGS, we obtained Mrna expression profiles in SH-4-54 treated K562 and K562R cells and identified differentially expressed mRNAs. Among these, STAT3 and STAT5 were markedly downregulated.

CONCLUSION

SH-4-54 may overcome IM resistance and represent a promising novel approach to improve the outcome of CML.