Inhibition of DNA synthesis by downregulation of cyclin A but not Skp 2 overexpression in human hepatocellular carcinoma cells.
Cyclin A is an S and G2/M phase regulatory protein and associates with Skp 2 in many transformed cells. Our previous results showed that 12 (39%) and 17 (55%) out of 31 hepatocellular carcinoma (HCC) patients exhibited higher protein expression levels of cyclin A and Skp 2, respectively, in their tumorous compared to non-tumorous tissues. In the present study, we used Western blot analysis to show that 3 out of 6 HCC cell lines, HA59T, HA22T and HCC36, exhibited overexpression of cyclin A, among which the HCC36 cell line also expressed a higher Skp 2 protein level. Moreover, we used the antisense oligonucleotide phosphorothioates to down regulate the overexpression of cyclin A and Skp 2 proteins to determine whether or not these two proteins are involved in the mitogenesis of HCC36 cells. After treatment with antisense oligonucleotide phosphorothioates, the gene product of cyclin A or Skp 2 was suppressed dose-dependently as revealed by Western blot analyses. By [3H]thymidine incorporation assay, we found that downregulation of cyclin A but not Skp 2 overexpression could inhibit the DNA synthesis ability of HCC36 cells, suggesting that abnormal Skp 2 expression is not directly correlated with the HCC proliferation.
Chao
Y
Y
Cancer Center and Department of Internal Medicine, Veterans General Hospital-Taipei, and National Yang-Ming University, Taiwan.
Shih
Y L
YL
Chen
H J
HJ
Lee
S D
SD
Huang
T S
TS
D006528:Carcinoma, Hepatocellular / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000378:metabolism*; D019925:Cyclin A / Q000378:metabolism*; D004273:DNA, Neoplasm / Q000096:biosynthesis*; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation; D006801:Humans; D016376:Oligonucleotides, Antisense; D044786:S-Phase Kinase-Associated Proteins; D014407:Tumor Cells, Cultured
D018797:Cell Cycle Proteins; D019925:Cyclin A; D004273:DNA, Neoplasm; D016376:Oligonucleotides, Antisense; D044786:S-Phase Kinase-Associated Proteins