Involvement of mTOR and survivin inhibition in tamoxifen-induced apoptosis in human hepatoblastoma cell line HepG2.
Patients with advanced hepatocellular carcinoma (HCC) have shown to benefit from tamoxifen treatment. The mechanisms of tamoxifen effects in HCC, however, are not yet clearly understood. The PI3K/Akt/mTOR signal pathway is involved in cell proliferation, tumorigenesis, and apoptosis. Over-expression of survivin has played an important role in leading to antiapoptosis. The current study investigated changes in mTOR pathway and survivin expression in hepatocarcinoma cell line HepG2 treated with tamoxifen. We detected apoptosis of hepatocarcinoma cells by flow cytometry assay. Survivin transcription level and p70S6k was demonstrated by PCR, dual-luciferase reporter assay and western blot analysis respectively. Our results are showed as follows: tamoxifen leads to apoptosis of the cells, and reduction in survivin expression, as well as a dramatic reduction in the activated form of p70S6 kinase. Twenty micromoles tamoxifen treatment significantly depresses transcription of survivin mRNA. Treating HepG2 cells with rapamycin, a specific mTOR inhibitor, significantly reduce survivin protein level but did not affect survivin transcription, which indicated that tamoxifen and rapamycin were synergistic in regards to down-regulation of survivin expression in hepatocellular carcinoma cells. Our results suggest that tamoxifen down-regulate survivin expression in HepG2 cells is mediated by transcriptional and posttranscriptional level via PI3K/Akt/mTOR pathway to induce apoptosis.
Guo
Renhua
R
Department of oncology, First Affiliated Hospital of Nanjing Medical University, Nanjing Guangzhou road 300, Nanjing 210029, China.
Wang
Tongshan
T
Shen
Hua
H
Ge
Hong-mei
HM
Sun
Jing
J
Huang
Zu-hu
ZH
Shu
Yong-qian
YQ
D018931:Antineoplastic Agents, Hormonal / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D015536:Down-Regulation / Q000187:drug effects; D004357:Drug Synergism; D005434:Flow Cytometry; D017930:Genes, Reporter; D056945:Hep G2 Cells; D018197:Hepatoblastoma / Q000188:drug therapy / Q000473:pathology; D006801:Humans; D051034:Inhibitor of Apoptosis Proteins; D047908:Intracellular Signaling Peptides and Proteins / Q000187:drug effects* / Q000378:metabolism; D008113:Liver Neoplasms / Q000188:drug therapy / Q000473:pathology; D008156:Luciferases; D008869:Microtubule-Associated Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics; D016133:Polymerase Chain Reaction; D017346:Protein Serine-Threonine Kinases / Q000187:drug effects* / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D020123:Sirolimus / Q000494:pharmacology; D000077022:Survivin; D058570:TOR Serine-Threonine Kinases; D013629:Tamoxifen / Q000494:pharmacology*
D018931:Antineoplastic Agents, Hormonal; C107489:BIRC5 protein, human; D051034:Inhibitor of Apoptosis Proteins; D047908:Intracellular Signaling Peptides and Proteins; D008869:Microtubule-Associated Proteins; D000077022:Survivin; D013629:Tamoxifen; D008156:Luciferases; C546842:MTOR protein, human; D017346:Protein Serine-Threonine Kinases; D058570:TOR Serine-Threonine Kinases; D020123:Sirolimus