Rapamycin inhibits cell growth by induction of apoptosis on hepatocellular carcinoma cells in vitro.
BACKGROUND
Rapamycin, isolated from Streptomyces hygroscopicus, is recently reported to have immunosuppressant and anti-tumor effects on a large variety of cancers. To date, no detailed data are available about the effects of rapamycin on hepatocellular carcinoma cells.


OBJECTIVE
In this study, the anti-proliferation effects of rapamycin on hepatocellular carcinoma cells BEL-7402 and HepG-2 in vitro were studied.


METHODS
Cell viability was assessed by MTT assay and [3H]-thymidine uptake, cell apoptosis was observed by Hoechst 33258 staining and flow cytometry (FCM). The variation of caspase-3 and apoptotic related genes was assayed by Western blotting, cell mitochondrial membrane potential was also investigated by using standard methods.


RESULTS
Rapamycin could inhibit the growth of hepatocellular carcinoma cells and cause apoptosis significantly; the suppression was both in time- and dose-dependent manner, marked morphological changes of cell apoptosis were observed very clearly by Hoechst 33258 staining. Rapamycin exhibits induction apoptosis by activation of caspase-3 and disruption of the mitochondrial membrane potential on hepatocellular carcinoma cells in vitro. Western blotting analysis demonstrated that anti-apoptotic protein Bcl-2 was down-regulated while pro-apoptotic protein Bcl-xl up-regulated remarkably in a time-dependent manner when apoptosis occurred.


CONCLUSIONS
Rapamycin has significant anti-proliferation effect by induction of apoptosis via activation of caspase-3 and disruption of mitochondrial membrane potential, as well as by down-regulation of anti-apoptotic protein Bcl-2 and up-regulation of pro-apoptotic protein Bcl-xl on hepatocellular carcinoma cells. The data provide a potential mechanism for rapamycin-induced apoptosis in hepatocellular carcinoma cells, suggesting that rapamycin may serve as both an effective adjunctive reagent for the treatment of residual cancer cells and immunosuppressant after liver transplantation of hepatocellular carcinoma, and that in vivo anti-cancer effects as well as its potential clinical effectiveness need further investigation.
Zhang
Jun-Feng
JF
Department of Liver Transplantation, The Third Affiliated Hospital of Sun Yat-sen University, TianHe Road 600, Guangdong Guangzhou, 510630, P.R. China.
Liu
Jia-Jun
JJ
Lu
Min-Qiang
MQ
Cai
Chang-Jie
CJ
Yang
Yang
Y
Li
Hua
H
Xu
Chi
C
Chen
Gui-Hua
GH
D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D006528:Carcinoma, Hepatocellular / Q000378:metabolism*; D053148:Caspase 3; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D005434:Flow Cytometry; D006801:Humans; D007166:Immunosuppressive Agents / Q000494:pharmacology*; D008113:Liver Neoplasms / Q000378:metabolism*; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000187:drug effects / Q000378:metabolism; D020123:Sirolimus / Q000494:pharmacology*; D051020:bcl-X Protein / Q000187:drug effects / Q000378:metabolism
D007166:Immunosuppressive Agents; D019253:Proto-Oncogene Proteins c-bcl-2; D051020:bcl-X Protein; D053148:Caspase 3; D020123:Sirolimus