[Correlation between inhibitory effect of Manumycin on human hepatoma cancer cell HepG2 and Ras signal transduction pathway].
OBJECTIVE
Treatment with anti-cancer agents has failed to achieve satisfactory results in hepatocellular carcinoma. In the process of hepatocarcinogenesis, Ras has been shown to play an important role. Ras requires a farnesyl moiety for activation. It has been found that farnesyltransferase inhibitor Manumycin inhibits farnesyl protein transferase, which catalyzes farnesylation. This study was designed to investigate the antitumor effect of Manumycin in human hepatoma cell line HepG2 and try to clarify its influence on Ras pathway.


METHODS
The growth inhibitory effect of farnesyltransferase inhibitor Manumycin on human hepatoma cell line HepG2 was observed by using [3H]thymidine incorporation assay. The relative protein expressions of pan-Ras, N-Ras, ERK1/2, AKT, and MKP-1 affected by Manumycin were determined by using Western blot analysis.


RESULTS
Manumycin(5, 10, 20, 40, and 80 mumol/L) significantly inhibited cell growth of human hepatoma cell line HepG2 with IC50 value of (17.1 +/- 2.6) mumol/L. Manumycin could inhibit both pan-Ras and N-Ras in human hepatoma HepG2 cells, but its inhibitory effect on pan-Ras of cell membrane was much stronger. Phospho-MAPK and phospho-AKT decreased significantly after treatment of HepG2 cells with Manumycin, while total MAPK and AKT were hardly affected. After treatment with 10 nmol/L wortmannin for 1 h, which had potent inhibitory effect on phosphorylation of AKT, Manumycin had stronger inhibitory effect on phosphorylation of AKT as compared to treatment without wortmannin, eventhough AKT protein levels were still unaffected. Furthermore, the expression of MKP-1 was elevated through manumycin treatment in a concentration-dependent manner.


CONCLUSIONS
Manumycin may significantly inhibit the growth of human hepatoma cell line HepG2, which was related to its inhibition on the combination of Ras and cell membrane and increasing the expression of MKP-1, accordingly inhibiting activation of ERK1/2 and AKT. These results suggest that Manumycin antagonizes the growth of HepG2 via the suppression of ras farnesylation blocking the function of oncogenic ras against and could be a potential new anti-cancer agents human cancer, including hepatocellular carcinoma.
Zhou
Jun-min
JM
Cancer Institute, Sun Yat-sen University, Guangzhou 510060, P. R. China. zhoujm21@hotmail.com
Pan
Qi-chao
QC
Yang
Xiao-ping
XP
Liu
Zong-chao
ZC
Liao
Duan-fang
DF
Fu
Li-wu
LW
Liang
Yong-ju
YJ
D000970:Antineoplastic Agents / Q000494:pharmacology*; D006528:Carcinoma, Hepatocellular / Q000473:pathology; D002455:Cell Division / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D008113:Liver Neoplasms / Q000473:pathology; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011090:Polyenes / Q000494:pharmacology*; D053284:Polyunsaturated Alkamides; D017368:Protein Prenylation / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors; D051057:Proto-Oncogene Proteins c-akt; D015398:Signal Transduction / Q000187:drug effects*; D014407:Tumor Cells, Cultured; D018631:ras Proteins / Q000187:drug effects / Q000378:metabolism*
D000970:Antineoplastic Agents; D004791:Enzyme Inhibitors; D011090:Polyenes; D053284:Polyunsaturated Alkamides; D011518:Proto-Oncogene Proteins; C494918:AKT1 protein, human; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D020928:Mitogen-Activated Protein Kinases; D018631:ras Proteins; C054474:manumycin