baohuoside-i and Leukemia--Myeloid--Acute

Acute myeloid leukemia (AML) is a devastating hematological malignancy, characterized by differentiation arrest and unscheduled proliferation of immature cells of the myeloid lineage. Inducing AML cell differentiation has emerged as a promising therapeutic strategy for the therapy of AML. Icariside II, an active component of Herba Epimedii, has been well defined to promote osteogenic differentiation. However, the differentiation-inducing effect of Icariside II on AML cells has not been explored. In this study, we investigated the differentiation-inducing effect and underlying mechanism of Icariside II in AML HL-60 and THP-1 cell lines. Icariside II induced G1 phase cell cycle arrest by down-regulating Cyclin-dependent kinases (CDK2, CDK4 and CDK6) and up-regulating Cyclin-dependent kinase inhibitor (p21 and p27). Importantly, Icariside II could induce differentiation of AML cells, accompanied by the up-regulation of Toll-like receptor 8 (TLR8), myeloid differentiation factor 88 (MyD88) and phosphorylated p38. Further study indicated the cell cycle arrest and differentiation induced by Icariside II could be abrogated by TLR8-specific inhibitor CU-CPT9a. Collectively, these findings firstly demonstrate Icariside II induces cell cycle arrest and differentiation of AML cells via activation of TLR8/MyD88/p38 pathway, suggesting Icariside II could be developed into a novel differentiation-inducing agent for AML.

Topics: Cell Cycle Checkpoints; Cell Differentiation; Cyclin-Dependent Kinase 2; Cyclin-Dependent Kinase 4; Cyclin-Dependent Kinase 6; Cyclin-Dependent Kinase Inhibitor p21; Cyclin-Dependent Kinase Inhibitor p27; Down-Regulation; Flavonoids; HL-60 Cells; Humans; Leukemia, Myeloid, Acute; MAP Kinase Signaling System; Membrane Glycoproteins; Osteogenesis; Receptors, Interleukin-1; Signal Transduction; THP-1 Cells; Toll-Like Receptor 8; Up-Regulation

The aim of this study is to determine anti-cancer effect of Icariside II purified from the root of Epimedium koreanum Nakai on human acute myeloid leukemia (AML) cell line U937.. Icariside II blocked the growth U937 cells in a dose- and time-dependent manner. In this anti-proliferation process, this herb compound rendered the cells susceptible to apoptosis, manifested by enhanced accumulation of sub-G1 cell population and increased the terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL)-positive cells. Icariside II was able to activate caspase-3 and cleaved poly (ADP-ribose) polymerase (PARP) in a time-dependent manner. Concurrently, the anti-apoptotic proteins, such as bcl-x(L) and survivin in U937 cells, were downregulated by Icariside II. In addition, Icariside II could inhibit STAT3 phosphorylation and function and subsequently suppress the activation of Janus activated kinase 2 (JAK2), the upstream activators of STAT3, in a dose- and time-dependent manner. Icariside II also enhanced the expression of protein tyrosine phosphatase (PTP) SH2 domain-containing phosphatase (SHP)-1, and the addition of sodium pervanadate (a PTP inhibitor) prevented Icariside II-induced apoptosis as well as STAT3 inactivation in STAT3 positive U937 cells. Furthermore, silencing SHP-1 using its specific siRNA significantly blocked STAT3 inactivation and apoptosis induced by Icariside II in U937 cells.. Our results demonstrated that via targeting STAT3-related signaling, Icariside II sensitizes U937 cells to apoptosis and perhaps serves as a potent chemotherapeutic agent for AML.

Topics: Antineoplastic Agents, Phytogenic; Apoptosis; bcl-X Protein; Caspase 3; Cell Cycle; Cell Line, Tumor; Cell Proliferation; Dose-Response Relationship, Drug; Epimedium; Flavonoids; Gene Expression Regulation, Neoplastic; Humans; Inhibitor of Apoptosis Proteins; Janus Kinase 2; Leukemia, Myeloid, Acute; Phosphorylation; Plant Extracts; Plant Roots; Poly(ADP-ribose) Polymerases; Protein Tyrosine Phosphatase, Non-Receptor Type 6; Signal Transduction; STAT3 Transcription Factor; Survivin