Induction of enantio-selective apoptosis in human leukemia HL-60 cells by (S)-erypoegin K,an isoflavone isolated from Erythrina poeppigiana

Erypoegin K, an isoflavone isolated from the stem bark of Erythrina poeppigiana, has potent apoptosis-inducing effect on human leukemia HL-60 cells. Erypoegin K has a chiral carbon at the C-2′′ position of its furan ring and naturally occurs as a racemic mixture of (S)- and (R)-isomers. In the present study, we semi-synthesized (RS)-erypoegin K from genistein and separated the optical isomers by HPLC using a chiral column to characterize its apoptosis-inducing activity. Apoptotic cell death was assessed by analyzing caspase-3 and caspase-9 activation, nuclear fragmentation, and genomic DNA ladder formation. (S)-erypoegin K showed exclusive anti-proliferative and apoptosis-inducing activity, with an IC₅₀ value of 90 nM, about 50% lower than that of its racemic mixture (175 nM). By contrast, no apoptosis-inducing activity was shown by the (R)-isomer. In addition, methylglyoxal accumulation in the culture medium was observed only in cells treated with (S)-erypoegin K. These results demonstrated that (S)-erypoegin K is a unique bioactive component that has potent apoptosis-inducing activity on HL-60 cells.     

Potent antitumor activities of recombinant human PDCD5 protein in combination with chemotherapy drugs in K562 cells

Conventional chemotherapy is still frequently used. Programmed cell death 5 (PDCD5) enhances apoptosis of various tumor cells triggered by certain stimuli and is lowly expressed in leukemic cells from chronic myelogenous leukemia patients. Here, we describe for the first time that recombinant human PDCD5 protein (rhPDCD5) in combination with chemotherapy drugs has potent antitumor effects on chronic myelogenous leukemia K562 cells in vitro and in vivo. The antitumor efficacy of rhPDCD5 protein with chemotherapy drugs, idarubicin (IDR) or cytarabine (Ara-C), was examined in K562 cells in vitro and K562 xenograft tumor models in vivo. rhPDCD5 protein markedly increased the apoptosis rates and decreased the colony-forming capability of K562 cells after the combined treatment with IDR or Ara-C. rhPDCD5 protein by intraperitoneal administration dramatically improved the antitumor effects of IDR treatment in the K562 xenograft model. The tumor sizes and cell proliferation were significantly decreased; and TUNEL positive cells were significantly increased in the combined group with rhPDCD5 protein and IDR treatment compared with single IDR treatment groups. rhPDCD5 protein, in combination with IDR, has potent antitumor effects on chronic myelogenous leukemia K562 cells and may be a novel and promising agent for the treatment of chronic myelogenous leukemia.     

Molecular evidence of anti-leukemia activity of gypenosides on human myeloid leukemia HL-60 cells in vitro and in vivo using a HL-60 cells murine xenograft model

We have shown that gypenosides (Gyp) induced cell cycle arrest and apoptosis in many human cancer cell lines. However, there are no reports showing that show Gyp acts on human leukemia HL-60 cells in vitro and in a murine xenograft model in vivo. In the present study effects of Gyp on cell morphological changes and viability, cell cycle arrest and induction of apoptosis in vitro and effects on Gyp in an in vivo murine xenograft model. Results indicated that Gyp induced morphological changes, decreased cell viability, induced G0/G1 arrest, DNA fragmentation and apoptosis (sub-G1 phase) in HL-60 cells. Gyp increased reactive oxygen species production and Ca²⁺ levels but reduced mitochondrial membrane potential in a dose- and time-dependent manner. Gyp also changed one of the primary indicators of endoplasmic reticulum (ER) stress due to the promotion of ATF6-α and ATF4-α associated with Ca²⁺ release. Gyp reduced the ratio of Bcl-2 to Bax due to an increase in the pro-apoptotic protein Bax and inhibited levels of the anti-apoptotic protein Bcl-2. Oral consumption of Gyp reduced tumor size of HL-60 cell xenograft mode mice in vivo. These results provide new information on understanding mechanisms by which Gyp induces cell cycle arrest and apoptosis in vitro and in vivo.