Rapamycin enhances chemotherapy-induced cytotoxicity by inhibiting the expressions of TS and ERK in gastric cancer cells.
We have previously reported the synergistic cytotoxic effects of Docetaxel (TXT) and S-1 in gastric cancer in vitro and in vivo, and the combination regimen is now under phase III clinical trail. In this study, to elucidate whether the rapamycin, the inhibitor of the mTOR (mammalian target of rapamaycin), can enhance the potentiation of TXT and 5-fluorouracil (5-Fu) in gastric carcinoma cells. Rapamycin inhibited the growth of TMK-1, MKN-28, MKN-45 and MKN-74 cell lines by MTT assay, and it demonstrated the cytostatic effects as G1 arrest shown by flowcytometry. However, the cytotoxic effects of 5-Fu, TXT and cisplatin were enhanced by 2 to 4 times with the concomitant administration of rapamycin. To clarify the mechanism of the potentiation, the expression changes of the enzymes relating DNA metabolism and cell growth signal transduction pathways were examined by western blot analysis. Interestingly, the expression of thymidilate synthase was markedly decreased by the administration of rapamycin in TMK-1 cells in a time- and dose-dependent manner. Moreover, rapamycin decreased the phosphorylation of 4E-BP1, the phosphorylation of ERK1/2 and enhanced the phosphorylation of c-Jun NH2-terminal kinase, and the activation of caspase of apoptotic pathways in combination with TXT. These results strongly indicate that the mTOR inhibitor can enhance the potentiation of TXT and 5-Fu or S-1 and can serve as a new therapeutic tool for advanced and recurrent gastric cancer patients.
Department of Surgical Oncology, Research Institute for Radiation Biology and Medicine, Hirsoshima University, Japan.
Hideo
H
Shigematsu
Kazuhiro
K
Yoshida
Yuichi
Y
Sanada
Shinnji
S
Osada
Takao
T
Takahashi
Yoshiyuki
Y
Wada
Kazuo
K
Konishi
Morihito
M
Okada
Masakazu
M
Fukushima
D000903:Antibiotics, Antineoplastic / Q000627:therapeutic use; D000970:Antineoplastic Agents / Q000627:therapeutic use; D017209:Apoptosis / Q000187:drug effects; D002453:Cell Cycle / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D045744:Cell Line, Tumor; D000077143:Docetaxel; D048049:Extracellular Signal-Regulated MAP Kinases / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D005434:Flow Cytometry; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D015398:Signal Transduction / Q000187:drug effects; D020123:Sirolimus / Q000627:therapeutic use*; D013274:Stomach Neoplasms / Q000188:drug therapy* / Q000235:genetics* / Q000473:pathology; D043823:Taxoids / Q000627:therapeutic use
D000903:Antibiotics, Antineoplastic; D000970:Antineoplastic Agents; D043823:Taxoids; D000077143:Docetaxel; D048049:Extracellular Signal-Regulated MAP Kinases; D020123:Sirolimus