Huai Qi Huang-induced Apoptosis via Down-regulating PRKCH and Inhibiting RAF/MEK/ERK Pathway in Ph Leukemia Cells.

Imatinib mesylate (IM) is the first-line treatment for Philadelphia (Ph) chromosomal positive leukemia by inhibiting phosphorylation of substrates via binding to the ABL kinase domain. Because of the drug resistance, side effects and the high cost of IM, it is necessary to find anti-cancer drugs with relatively low toxicity and cost, and enhanced efficacy, such as traditional Chinese medicines (TCMs). As one of TCMs, Huai Qi Huang (HQH) was chosen to treat BV173 and K562 cells. Various concentrations of HQH were added to cells for 24-72 h. Co-treatment of HQH and trametinib, an MEK inhibitor, was used to verify the synergistic effects on cell viability and apoptosis. Knockdown and overexpression of mitogen-activated protein kinase kinase 4 (MEK4) were implemented to demonstrate the role of MEK in cell apoptosis. Cell viability and apoptosis were measured by cell counting kit-8 assay (CCK8) and flow cytometry, respectively. Western blotting and real-time quantitative PCR (RT-qPCR) were used to assess protein and mRNA expression levels, respectively. The results showed that HQH inhibited survival and promoted apoptosis of BV173 and K562 cells in a dose-dependent manner, accompanied with down-regulation of PRKCH mRNA as well as CRAF, MEK4, phospho-ERK (pERK) and BCL2 proteins, and up-regulation of cleaved caspase3 protein. Co-treatment of HQH and trametinib had a synergistic effect on inhibiting survival and promoting apoptosis. MEK4 knockdown increased apoptosis, and had a synergistic effect with HQH. In contrast, MEK4 overexpression decreased apoptosis, and had the opposite effect with HQH. Collectively, the results of this study may identify a therapeutic mechanism of HQH on promoting apoptosis, and provide a potential option for treatment of Ph leukemia.