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.