title: Mechanism of apoptotosis induced by ortho-topolin riboside in human hepatoma cell line SMMC-7721.
abstract: The naturally occurring cytokinin, ortho-topolin riboside (oTR), has been recently reported to have a strong anticancer effect. However, the molecular mechanism has not been elucidated. From our research we found that oTR strongly inhibited the proliferation of SMMC-7721 cells inducing apoptosis. After oTR treatment, up-regulation of the protein levels of pro-apoptotic Bax and the down-regulation of the anti-apoptotic proteins, Bcl-2 and Bcl-xL was observed, leading to the loss of mitochondrial membrane potential, the release of cytochrome c from the mitochondria into the cytosol, the downstream activation of caspase-9 and caspase-3, as well as the cleavage of poly ADP-ribose-polymerase (PARP), the effect of apoptosis could be blocked by the pan-specific caspase inhibitor z-VAD-fmk and caspase-9-specific inhibitor z-LEHD-fmk. Moreover, oTR was shown to inhibit the activation of the extracellular signal-regulated kinase-1/2 (ERK(1/2)) as well as the Akt pathway. These results suggest that oTR interferes with the mitogen-activated protein kinase (MAPK) and Akt pathways and induces the apoptosis of human SMMC-7721 cells through the activation of intrinsic mitochondria-mediated pathways. However, the apoptosis was completely prevented when cells were treated with A-134974, an inhibitor of adenosine kinase, it indicated that the intracellular phosphorylation of oTR is necessary for its cytotoxic effects to SMMC-7721 cells.
authors.affiliation: Department of Cell Biology, School of Life Sciences, Lanzhou University, Lanzhou 730000, PR China.
authors.forename: Li
authors.initials: L
authors.lastname: Wang
authors.forename: Chao
authors.initials: C
authors.lastname: Sun
authors.forename: Zhen-Hua
authors.initials: ZH
authors.lastname: Wang
authors.forename: Guang-Qin
authors.initials: GQ
authors.lastname: Guo
mesh_terms: D000248:Adenosine Kinase / Q000037:antagonists & inhibitors; D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D061945:Caspase Inhibitors; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D045304:Cytochromes c / Q000378:metabolism; D003583:Cytokinins / Q000494:pharmacology*; D005434:Flow Cytometry; D006801:Humans; D020935:MAP Kinase Signaling System / Q000187:drug effects; D008564:Membrane Potentials / Q000187:drug effects; D051336:Mitochondrial Membranes / Q000187:drug effects; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009705:Nucleosides / Q000494:pharmacology; D009842:Oligopeptides / Q000494:pharmacology; D051058:Oncogene Protein v-akt / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects
chemical_list: C422646:A 134974; D000590:Amino Acid Chloromethyl Ketones; D061945:Caspase Inhibitors; D003583:Cytokinins; D009705:Nucleosides; D009842:Oligopeptides; D019253:Proto-Oncogene Proteins c-bcl-2; C403754:benzyloxycarbonyl-leucyl-glutamyl-histidyl-aspartic acid fluoromethyl ketone; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; C575434:ortho-topolin riboside; D045304:Cytochromes c; D000248:Adenosine Kinase; D051058:Oncogene Protein v-akt; D020928:Mitogen-Activated Protein Kinases