Stachydrine is effective and selective against blast phase chronic myeloid leukaemia through inhibition of multiple receptor tyrosine kinases

CONTEXT: Resistance to BCR-ABL tyrosine kinase inhibitor (TKI) is the cause of treatment failure in blast phase chronic myeloid leukaemia (BP-CML). Agents that act synergistically with BCR-ABL TKI are required to improve response. OBJECTIVE: This work investigated the effects of stachydrine in CML. MATERIALS AND METHODS: CML cells were treated with control or stachydrine at 20, 40 and 80 µM. Proliferation and apoptosis were examined after 72 h treatment. Combination studies were performed in four groups: control, TKI, stachydrine and the combination of stachydrine and TKI. Immunoblotting analysis was performed in CML cells after 24 h treatment. RESULTS: Stachydrine inhibited K562 (IC(50) 61 µM), KCL22 (IC(50) 141 µM), LAMA84 (IC(50) 86 µM), Ba/F3 T315I (IC(50) 26 µM), Ba/F3 WT (IC(50) 22 µM) and KU812 (IC(50) 35 µM) proliferation, and induced apoptosis in these CML cell lines. Stachydrine significantly induced apoptosis, inhibited colony formation and self-renewal in BP-CML CD34(+) cells. The combination index of stachydrine and TKI combination was <1. Compared to TKI alone, the combination of stachydrine and TKI significantly induced more apoptosis and decreased colony formation in BP-CML CD34(+) cells. Stachydrine decreased phosphorylation levels of multiple receptor tyrosine kinases in CML cells. DISCUSSION AND CONCLUSIONS: Our study is the first to demonstrate (1) the anticancer activity of stachydrine on primary patient cancer cells; (2) the inhibitory effects of stachydrine on cancer stem cells; (3) the synergism between stachydrine and other anticancer drugs.