title: Specific mTOR inhibitor rapamycin enhances cytotoxicity induced by alkylating agent 1-(4-amino-2-methyl-5-pyrimidinyl)methyl-3-(2-chloroethyl)-3-nitrosourea (ACNU) in human U251 malignant glioma cells.
abstract: Loss of the PTEN tumor suppressor gene and amplification of the epidermal growth factor receptor (EGFR), which is common in malignant gliomas, result in activation of the mammalian target of rapamycin (mTOR). Rapamycin is a highly specific inhibitor of mTOR and induces a cytostatic effect in various glioma cell lines. DNA-damaging agents such as nitrosourea are widely used in malignant glioma treatment; therefore, we investigated the effect of rapamycin on cell growth and death in combination with 1-(4-amino-2-methyl-5-pyrimidinyl)methyl-3-(2-chloroethyl)-3-nitrosourea (ACNU, nimustine hydrochloride) in human glioma cells. In U251 malignant glioma (U251MG) cells, we confirmed that rapamycin enhanced ACNU-induced apoptosis. We found that rapamysin inhibited ACNU-induced p21 induction, and knocking down of p21 protein by siRNA enhanced ACNU-induced apoptosis in U251MG cells. Furthermore, adenovirus-mediated over-expression of p21 protein rescued U251MG cells from apoptosis induced by ACNU and rapamycin. Finally, treatment of intracerebral U251MG xenografts with a combination of rapamycin and ACNU in vivo resulted in statistically prolonged median survival (P<0.05). These results suggest that rapamycin in combination with DNA-damaging agents may be efficacious in the treatment of malignant gliomas.
authors: Department of Neurosurgery, Kobe University Graduate School of Medicine, 7-5-1, Kusunoki-cho, Chou-ku, Kobe, 650-0017, Japan. hiro2804@med.kobe-u.ac.jp
authors: Kazuhiro
authors: K
authors: Tanaka
authors: Takashi
authors: T
authors: Sasayama
authors: Katsu
authors: K
authors: Mizukawa
authors: Atsufumi
authors: A
authors: Kawamura
authors: Takeshi
authors: T
authors: Kondoh
authors: Kohkichi
authors: K
authors: Hosoda
authors: Toshiyoshi
authors: T
authors: Fujiwara
authors: Eiji
authors: E
authors: Kohmura
mesh_terms: D000818:Animals; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism; D004357:Drug Synergism; D005910:Glioma / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D007150:Immunohistochemistry; D020287:In Situ Nick-End Labeling; D008297:Male; D009374:Neoplasms, Experimental / Q000188:drug therapy*; D015376:Nimustine / Q000494:pharmacology*; D011494:Protein Kinases / Q000187:drug effects; D034741:RNA, Small Interfering; D051381:Rats; D011923:Rats, Nude; D020123:Sirolimus / Q000494:pharmacology*; D058570:TOR Serine-Threonine Kinases; D023041:Xenograft Model Antitumor Assays
chemical_list: D050759:Cyclin-Dependent Kinase Inhibitor p21; D034741:RNA, Small Interfering; D015376:Nimustine; D011494:Protein Kinases; C546842:MTOR protein, human; D058570:TOR Serine-Threonine Kinases; D020123:Sirolimus