Securinine Induces Differentiation of Human Promyelocytic Leukemic HL-60 Cells through JNK-Mediated Signaling Pathway

Acute myeloid leukemia is characterized by abnormal differentiation of hematopoietic stem cells, leading to the accumulation of immature myeloid cells. Differentiation therapy has been a successful treatment option for acute promyelocytic leukemia but suffers from adverse effects. Therefore, search for novel differentiation-inducing agents with minimal side effects is desirable. Securinine, a naturally-occurring alkaloid, induces differentiation in various leukemic cells and apoptosis in other types of cancers. However, the underlying molecular mechanism(s) remain elusive. Our study aimed to elucidate the possible molecular mechanism(s) and signaling events involved in securinine-induced differentiation of HL-60 cells. Securinine inhibited proliferation in a time- and dose-dependent manner and triggered differentiation. A higher CD14+ population indicated maturation toward monocytic lineage. Securinine caused cell cycle arrest at the G0/G1 phase and enhanced ROS generation. Quantitative gene expression analysis showed significant down-regulation of C/EBP-alpha, C/EBP-epsilon, GA tau Alpha, and c-myc and up-regulation of the PU.1 gene. The expression of distinct protein kinases Lyn, Chk-2, Yes, FAK, c-Jun, and JNK were enhanced. Use of specific inhibitors of crucial intracellular signaling proteins indicated that JNK and ERK blockade resulted in a significant decline in differentiation. These data thus confirm that securinine induces differentiation through the activation of the JNK-ERK signaling pathway in HL-60 cells.