Xylocydine, a novel Cdk inhibitor, is an effective inducer of apoptosis in hepatocellular carcinoma cells in vitro and in vivo.
Hepatocellular carcinoma (HCC) frequently includes abnormalities in cell cycle regulators, including up-regulated cyclin-dependent kinase (Cdks) activities due to loss or low expression of Cdk inhibitors. In this study, we show that xylocydine, a cyclin-dependent kinase (Cdk) specific inhibitor, is a good anti-cancer drug candidate for HCC treatment. Xylocydine (50muM) selectively down-regulates the activity of Cdk1 and Cdk2, accompanied by significant cell growth inhibition in HCC cells. Xylocydine also strongly inhibits the activity of Cdk7 and Cdk9, in vitro as well as in cell cultures, that is temporally associated with apoptotic cell death in xylocydine-induced HCC cells. This is associated with inhibition of phosphorylation of RNA polymerase II at serine residues 5 and 2, which are targets of Cdk7 and Cdk9, respectively. The effects on apoptosis are concomitant with changes in the levels of anti-apoptotic proteins, Bcl-2, XIAP, and survivin, which are markedly down-regulated, and pro-apoptotic molecules, p53 and Bax, which are elevated in HCC cells after treatment with xylocydine. The up-regulated level of p53 was associated with increased stability of the protein, as levels of Ser15 and Ser392 phsophorylated p53 are similarly elevated in the inhibitor treated cells. We demonstrated that xylocydine can effectively suppress the growth of HCC xenografts in Balb/C-nude mice by preferentially inducing apoptosis in the xenografts, whereas the drug did not cause any apparent toxic effect on other tissues. Taken together, these data suggest that the novel Cdk inhibitor xylocydine is a good candidate for an anti-cancer drug for HCC therapy.
Cho
Seung-Ju
SJ
Division of Pharmaceutical Biosciences, College of Pharmacy and The Research Institute for Pharmaceutical Sciences, Seoul National University, Seoul 151-742, Republic of Korea.
Lee
Seung-Soo
SS
Kim
Young-Jong
YJ
Park
Byoung-Duck
BD
Choi
Joon-Seok
JS
Liu
Linhua
L
Ham
Young-Mi
YM
Moon Kim
B
B
Lee
Seung-Ki
SK
D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D016203:CDC2 Protein Kinase / Q000037:antagonists & inhibitors / Q000378:metabolism; D006528:Carcinoma, Hepatocellular / Q000188:drug therapy* / Q000201:enzymology / Q000473:pathology; D049109:Cell Proliferation / Q000187:drug effects; D051357:Cyclin-Dependent Kinase 2 / Q000037:antagonists & inhibitors / Q000378:metabolism; D042863:Cyclin-Dependent Kinase 9 / Q000037:antagonists & inhibitors / Q000378:metabolism; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D056945:Hep G2 Cells; D006801:Humans; D051034:Inhibitor of Apoptosis Proteins / Q000378:metabolism; D008113:Liver Neoplasms / Q000188:drug therapy* / Q000201:enzymology / Q000473:pathology; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D009705:Nucleosides / Q000494:pharmacology*; D010766:Phosphorylation; D047428:Protein Kinase Inhibitors / Q000494:pharmacology*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D012319:RNA Polymerase II / Q000378:metabolism; D013997:Time Factors; D047368:Tumor Burden; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D023041:Xenograft Model Antitumor Assays; D051028:bcl-2-Associated X Protein / Q000378:metabolism; D000095043:Cyclin-Dependent Kinase-Activating Kinase
C547380:4-amino-6-bromo-7-(xylofuranosyl)pyrrolo(2,3-d)pyrimidine-5-carboxamide; D000970:Antineoplastic Agents; C494826:BAX protein, human; D051034:Inhibitor of Apoptosis Proteins; D009705:Nucleosides; D047428:Protein Kinase Inhibitors; D019253:Proto-Oncogene Proteins c-bcl-2; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; D051028:bcl-2-Associated X Protein; D016203:CDC2 Protein Kinase; C495894:CDK2 protein, human; C467969:CDK9 protein, human; D051357:Cyclin-Dependent Kinase 2; D042863:Cyclin-Dependent Kinase 9; D018844:Cyclin-Dependent Kinases; D012319:RNA Polymerase II; D000095043:Cyclin-Dependent Kinase-Activating Kinase