Mistletoe lectin induces apoptosis and telomerase inhibition in human A253 cancer cells through dephosphorylation of akt

Mistletoe lectin has been reported to induce apoptosis in different cancer cell linesin vitro and to show antitumor activity against a variety of tumors in animal models. We previously demonstrated the Korean mistletoe lectin (Viscum album var.coloratum, VCA)-induced apoptosis by down-regulation of Bcl-2 and telomerase activity and by up-regulation of Bax through p53- and p21-independent pathway in hepatoma cells. In the present study, we observed the induction of apoptotic cell death through activation of caspase-3 and the inhibition of telomerase activity through transcriptional down-regulation of hTERT in the VCA-treated A253 cells. We also observed the inhibition of telomerase activity and induction of apoptosis resulted from dephosphorylation of Akt in the survival signaling pathways. In addition, combining VCA with the inhibitors of phosphatidylinositol 3-kinase (PI3-kinase) upstream of Akt, wortmannin and LY294002 showed an additive inhibitory effect of telomerase activity. In contrast, the inhibitor of protein phosphatase 2A (PP2A), okadaic acid inhibited VCA-induced dephosphorylation of Akt and inhibition of telomerase activity. Taken together, VCA induces apoptotic cell death through Akt signaling pathway in correlated with the inhibition of telomerase activity and the activation of caspase-3. From these results, together with our previous studies, we suggest that VCA triggers molecular changes that resulting in the inhibition of cell growth and the induction of apoptotic cell death of cancer cells, which suggest that VCA may be useful as chemotherapeutic agent for cancer cells.

[1]  A. Büssing,et al.  Intracellular expression of IL-4 and inhibition of IFN-gamma by extracts from European mistletoe is related to induction of apoptosis. , 2000, Anticancer research.

[2]  R. Park,et al.  Activation of caspase cascades in Korean mistletoe (Viscum album var. coloratum) lectin-II-induced apoptosis of human myeloleukemic U937 cells. , 2000, General pharmacology.

[3]  W. H. Kim,et al.  Involvement of Caspase-3 in Apoptosis Induced by Viscum album var. coloratum Agglutinin in HL-60 Cells , 2001, Bioscience, biotechnology, and biochemistry.

[4]  M. Robinson,et al.  Telomere shortening and apoptosis in telomerase-inhibited human tumor cells. , 1999, Genes & development.

[5]  C B Harley,et al.  Specific association of human telomerase activity with immortal cells and cancer. , 1994, Science.

[6]  R. Anton,et al.  Modulation of cytotoxicity and enhancement of cytokine release induced by Viscum album L. extracts or mistletoe lectins , 1997, Anti-cancer drugs.

[7]  S. Choi,et al.  Korean mistletoe lectin-induced apoptosis in hepatocarcinoma cells is associated with inhibition of telomerasevia mitochondrial controlled pathway independent of p53 , 2002, Archives of pharmacal research.

[8]  M. Greenberg,et al.  Akt Promotes Cell Survival by Phosphorylating and Inhibiting a Forkhead Transcription Factor , 1999, Cell.

[9]  Elizabeth Yang,et al.  Serine Phosphorylation of Death Agonist BAD in Response to Survival Factor Results in Binding to 14-3-3 Not BCL-XL , 1996, Cell.

[10]  D R Alessi,et al.  Mitogenic Activation, Phosphorylation, and Nuclear Translocation of Protein Kinase Bβ* , 1997, The Journal of Biological Chemistry.

[11]  J. Steitz,et al.  Telomere shortening associated with chromosome instability is arrested in immortal cells which express telomerase activity. , 1992, The EMBO journal.

[12]  S. Lyu,et al.  Comparative study of korean (Viscum album var.coloratum) and european mistletoes (Viscum album) , 2000, Archives of pharmacal research.

[13]  Yoshikazu Tanaka,et al.  Inhibition of telomerase increases the susceptibility of human malignant glioblastoma cells to cisplatin-induced apoptosis , 1998, Oncogene.

[14]  A. Büssing,et al.  Induction of apoptosis in human lymphocytes treated with Viscum album L. is mediated by the mistletoe lectins. , 1996, Cancer letters.

[15]  J. Brock,et al.  The B-chain of mistletoe lectin I efficiently stimulates calcium signaling in human Jurkat T-cells. , 2001, Immunology letters.

[16]  S. R. Datta,et al.  Cellular survival: a play in three Akts. , 1999, Genes & development.

[17]  John Calvin Reed,et al.  Regulation of cell death protease caspase-9 by phosphorylation. , 1998, Science.

[18]  M. Lavin,et al.  Calyculin A, a potent inhibitor of phosphatases-1 and -2A, prevents apoptosis. , 1993, Biochemical and biophysical research communications.

[19]  B. Gjertsen,et al.  Protein phosphorylation in apoptosis. , 1995, Biochimica et biophysica acta.

[20]  A. Zeiher,et al.  Pro‐atherogenic factors induce telomerase inactivation in endothelial cells through an Akt‐dependent mechanism , 2001, FEBS letters.

[21]  Hun-taeg Chung,et al.  Potentiation of Tumor Necrosis Factor-α-Induced Apoptosis by Mistletoe Lectin , 2000 .

[22]  S. R. Datta,et al.  Akt Phosphorylation of BAD Couples Survival Signals to the Cell-Intrinsic Death Machinery , 1997, Cell.

[23]  E. Im,et al.  Inhibition of cell growth and telomerase activity of breast cancer cells in vitro by retinoic acids. , 2000, International journal of oncology.

[24]  Frank McCormick,et al.  Akt activation by growth factors is a multiple-step process: the role of the PH domain , 1998, Oncogene.

[25]  N. Hay,et al.  The PI 3-kinase/Akt signaling pathway delivers an anti-apoptotic signal. , 1997, Genes & development.

[26]  A. Multani,et al.  Induction of apoptosis by the N-acetyl-galactosamine-specific toxic lectin from Viscum album L. is associated with a decrease of nuclear p53 and Bcl-2 proteins and induction of telomeric associations. , 1998, Cancer letters.

[27]  D. Corey,et al.  Inhibition of human telomerase in immortal human cells leads to progressive telomere shortening and cell death. , 1999, Proceedings of the National Academy of Sciences of the United States of America.

[28]  I. H. Engels,et al.  Mistletoe lectin activates caspase-8/FLICE independently of death receptor signaling and enhances anticancer drug-induced apoptosis. , 1999, Cancer research.

[29]  S. Do,et al.  Akt Protein Kinase Enhances Human Telomerase Activity through Phosphorylation of Telomerase Reverse Transcriptase Subunit* , 1999, The Journal of Biological Chemistry.

[30]  G. Cooper,et al.  Requirement for phosphatidylinositol-3 kinase in the prevention of apoptosis by nerve growth factor. , 1995, Science.

[31]  H. Oh,et al.  Roles of extracellular signal-regulated kinase and p38 mitogen-activated protein kinase in apoptosis of human monoblastic leukemia U937 cells by lectin-II isolated from Korean mistletoe. , 2001, In vitro & molecular toxicology.

[32]  K. Anderson,et al.  Nuclear Factor-κB p65 Mediates Tumor Necrosis Factor α-induced Nuclear Translocation of Telomerase Reverse Transcriptase Protein , 2003 .

[33]  A. Büssing.  Biological and Pharmacological Properties of Viscum album L. From Tissue flask to Man , 2000 .