Ethanol Extract of Tripterygium wilfordii Hook. f. Induces G0/G1 Phase Arrest and Apoptosis in Human Leukemia HL-60 Cells Through c-Myc and Mitochondria-Dependent Caspase Signaling Pathways

Tripterygium wilfordii Hook. f. is a traditional Chinese herb (Murphy, 2006; Qiu et al., 2003). The extract of Tripterygium wilfordii Hook. f. has been widely applied to the treatment of immune-related diseases, such as rheumatoid arthritis (RA), nephritis, and systemic lupus erythematosus (SLE) (Chang et al., 1999; Wang et al., 2000). Extracts of Tripterygium wilfordii Hook. f. have been shown to inhibit lymphocyte proliferation induced by mitogentic stimulation in-vitro (Wu et al., 2003). Triptolide (PG490, one of the most active components in Tripterygium wilfordii Hook. f. extract, possesses immunosuppressive, anti-inflammatory and anti-fertility actions in vivo and in vitro (Zhao et al., 2005; Leuenroth et al., 2005). Many reports have demonstrated that triptolide has anti-proliferate activity against L1210, U937, K562, HL60, and P388 leukemia cells (Lou et al., 2004; Chan et al., 2001; Wei et al., 1991). However, the cellular and molecular mechanisms underlying mediating Tripterygium wilfordii Hook. f.-induced differentiation and/or apoptosis in leukemia cells have not been well studied.