Rapamycin regulates the proliferation of Huh7, a hepatocellular carcinoma cell line, by up-regulating p53 expression.
Rapamycin, a specific inhibitor of mTOR used extensively as an immunosuppressant, has been expanded recently to cancer therapy, because the mTOR signal is known to be up-regulated in various cancer cells including hepatocellular carcinoma (HCC) cells. In spite of extensive efforts to employ mTOR inhibitors as anti-HCC therapy, they have not yet been approved by the FDA. Because of the heterogeneity and complexity of molecular signaling in HCC, suitable biomarkers should be identified or discovered to improve clinical efficacy of mTOR-specific inhibitors to HCC cells. In this study, the effect of rapamycin was investigated on two different HCC cell lines, Huh7 cells and HepG2 cells. Rapamycin was found to inhibit the proliferation of Huh7 cells but not of HepG2 cells. Moreover, it was found that rapamycin can up-regulate p53 at the protein level, but not affect its transcript. To understand the critical role of p53 in the rapamycin effect, knock-down experiments were performed using small-interfering RNAs (siRNAs). The anti-proliferative effect of rapamycin on Huh7 cells clearly disappeared after blocking p53 production with siRNA, which indicates that p53 is a critical factor in the anti-proliferative effect of rapamycin in HCC cells. The over-expression system of p53 was also employed to mimic the effect of rapamycin and found that cell proliferation was clearly down-regulated by p53 over-expression. Finally, we found that the extracellular signal-regulated kinase 1/2 (ERK1/2) signal was regulated by p53 whose expression was induced by rapamycin. Overall, this study demonstrates that rapamycin inhibited the proliferation of Huh7 cells by up-regulating the expression of p53 and down-regulating the ERK1/2 signal, indicating that p53 is a useful biomarker for anti-cancer therapy using the specific inhibitor of mTOR signal, rapamycin, against hepatocellular carcinoma cells.
Department of Pharmaceutical Engineering, Hoseo University, Asan, Republic of Korea.
Sora
S
Kwon
Department of Pharmaceutical Engineering, Hoseo University, Asan, Republic of Korea.
Ji-Sook
JS
Jeon
Transplantation Research Institute, Seoul National University, Seoul, Republic of Korea.
Curie
C
Ahn
Department of Life Science, Dongguk University, Goyang, Republic of Korea. Electronic address: sungjs@dongguk.edu.
Jung-Suk
JS
Sung
Department of Pharmaceutical Engineering, Hoseo University, Asan, Republic of Korea. Electronic address: inhochoi@hoseo.edu.
Inho
I
Choi
D015153:Blotting, Western; D006528:Carcinoma, Hepatocellular / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects* / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D056945:Hep G2 Cells; D006801:Humans; D007166:Immunosuppressive Agents / Q000494:pharmacology; D008113:Liver Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000235:genetics; D034622:RNA Interference; D020133:Reverse Transcriptase Polymerase Chain Reaction; D020123:Sirolimus / Q000494:pharmacology*; D058570:TOR Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*; D015854:Up-Regulation / Q000187:drug effects*
D007166:Immunosuppressive Agents; D016159:Tumor Suppressor Protein p53; C546842:MTOR protein, human; D058570:TOR Serine-Threonine Kinases; D020123:Sirolimus
ERK signal; Hepatocellular carcinoma cells; Rapamycin; mTOR; p53