title: The combination of rapamycin and MAPK inhibitors enhances the growth inhibitory effect on Nara-H cells.
abstract: The inhibition of the mammalian target of rapamycin (mTOR) signaling pathway promotes the initiation of autophagy, and the mitogen-activated protein kinase (MAPK)/extracellular signal-regulated protein kinase (ERK) is well known to induce autophagy. Autophagy is a self-defense mechanism of cancer cells that are subjected to antitumor agents, and blocking autophagy can trigger apoptosis. In the present study, we demonstrate that an mTOR inhibitor, rapamycin, induces autophagy in the Nara-H malignant fibrous histiocytoma (MFH) cell line through the activation of ERK1/2. Rapamycin-induced apoptosis was enhanced following the inhibition of the MEK/ERK pathway. In the Nara-H cells, we examined the effects of rapamycin treatment on cell proliferation and on the phosphorylation of the mTOR pathway components and autophagy by western blot analysis. Furthermore, we examined the effects of rapamycin with or without the MEK inhibitor, U0126, on the induction of apoptosis by using fluorescence microscopy. Rapamycin inhibited Nara-H cell proliferation and decreased the phosphorylation of the mTOR pathway in the Nara-H cells. Rapamycin induced the apoptosis of Nara-H cells, and this apoptosis was enhanced by U0126. Simultaneously, phospho-ERK1/2 was activated by rapamycin. The present study demonstrates that rapamycin induces autophagy in Nara-H cells by activating the MEK/ERK signaling pathway, and the rapamycin-induced apoptosis can be enhanced by the MEK inhibitor, U0126. These results suggest that self‑protective mechanisms involving mTOR inhibitors in Nara-H cells are prevented by the inhibition of the MEK/ERK pathway. The combination of an mTOR inhibitor (e.g., rapamycin) and an MEK inhibitor (e.g., U0126) may offer effective treatment for MFH, as this combination effectively activates apoptotic pathways.
authors.affiliation: Department of Orthopaedic Surgery, Kagawa University School of Medicine, Kagawa 761-0793, Japan.
authors.forename: Osamu
authors.initials: O
authors.lastname: Nakamura
authors.affiliation: Department of Orthopaedic Surgery, Kagawa University School of Medicine, Kagawa 761-0793, Japan.
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Hitora
authors.affiliation: Department of Orthopaedic Surgery, Kagawa University School of Medicine, Kagawa 761-0793, Japan.
authors.forename: Yoshiki
authors.initials: Y
authors.lastname: Yamagami
authors.affiliation: Department of Orthopaedic Surgery, Kagawa University School of Medicine, Kagawa 761-0793, Japan.
authors.forename: Masaki
authors.initials: M
authors.lastname: Mori
authors.affiliation: Department of Orthopaedic Surgery, Kagawa University School of Medicine, Kagawa 761-0793, Japan.
authors.forename: Hideki
authors.initials: H
authors.lastname: Nishimura
authors.affiliation: Department of Orthopaedic Surgery, Kagawa University School of Medicine, Kagawa 761-0793, Japan.
authors.forename: Ryosuke
authors.initials: R
authors.lastname: Horie
authors.affiliation: Department of Orthopaedic Surgery, Kagawa University School of Medicine, Kagawa 761-0793, Japan.
authors.forename: Konosuke
authors.initials: K
authors.lastname: Yamaguchi
authors.affiliation: Department of Orthopaedic Surgery, Kagawa University School of Medicine, Kagawa 761-0793, Japan.
authors.forename: Tetsuji
authors.initials: T
authors.lastname: Yamamoto
mesh_terms: D017209:Apoptosis / Q000187:drug effects / Q000235:genetics; D015153:Blotting, Western; D002070:Butadienes / Q000494:pharmacology; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects; D006801:Humans; D020935:MAP Kinase Signaling System / Q000187:drug effects; D008856:Microscopy, Fluorescence; D020929:Mitogen-Activated Protein Kinase Kinases / Q000037:antagonists & inhibitors*; D009570:Nitriles / Q000494:pharmacology; D047428:Protein Kinase Inhibitors / Q000494:pharmacology*; D034622:RNA Interference; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects; D020123:Sirolimus / Q000494:pharmacology*
chemical_list: D002070:Butadienes; D009570:Nitriles; D047428:Protein Kinase Inhibitors; C113580:U 0126; D020929:Mitogen-Activated Protein Kinase Kinases; D020123:Sirolimus