title: Inhibition of induced autophagy increases apoptosis of Nara-H cells.
abstract: Inhibition of the mTOR signaling pathway promotes initiation of autophagy. However, recent studies indicate that autophagy is a self-defense mechanism of cancer cells that are subjected to anti-tumor agents and that blocking autophagy can trigger apoptosis. Here, we examined the effects of an mTOR inhibitor, temsirolimus, on a malignant fibrous histiocytoma (MFH) cell line, Nara-H cells, and the effect of suppressing autophagy on the induction of apoptosis in these MFH cells. In Nara-H cells, we examined the effects of temsirolimus treatment on cell proliferation using the CellTiter 96® AQueous One Solution Cell Proliferation Assay and on phosphorylation of mTOR pathway components and autophagy using Western blot-based assays. Furthermore, we examined the effects of temsirolimus with or without 3-methyladenine (3-MA) on induction of apoptosis using fluorescent microscopic analysis. In Nara-H cells, temsirolimus treatment inhibited cell proliferation, suppressed phosphorylation of mTOR pathway components, and induced autophagy as assessed by LC-3 II expression. Moreover, treatment with a combination of temsirolimus and 3-MA induced apoptosis in Nara-H cells. Apparently, simultaneous inhibition of autophagy and mTOR induced apoptosis in Nara-H cells because inhibition of autophagy prevented the cells from protecting themselves from the effects of the inhibition of mTOR. Therefore, a combination therapy that includes an mTOR inhibitor and an autophagy inhibitor (temsirolimus and 3-MA, respectively) may effectively treat MFH by inducing apoptosis in tumor cells.
authors.affiliation: Department of Orthopaedic Surgery, Kagawa University School of Medicine, Miki-cho, Kita-gun, Kagawa, Japan.
authors.forename: Osamu
authors.initials: O
authors.lastname: Nakamura
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Hitora
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Akisue
authors.forename: Teruya
authors.initials: T
authors.lastname: Kawamoto
authors.forename: Yoshiki
authors.initials: Y
authors.lastname: Yamagami
authors.forename: Tetsuji
authors.initials: T
authors.lastname: Yamamoto
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D001343:Autophagy / Q000187:drug effects*; D002453:Cell Cycle / Q000187:drug effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D051677:Histiocytoma, Malignant Fibrous / Q000378:metabolism*; D006801:Humans; D008856:Microscopy, Fluorescence; D051058:Oncogene Protein v-akt / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000494:pharmacology*; D015398:Signal Transduction / Q000187:drug effects; D020123:Sirolimus / Q000031:analogs & derivatives* / Q000494:pharmacology; D013194:Staining and Labeling; D058570:TOR Serine-Threonine Kinases / Q000037:antagonists & inhibitors
chemical_list: D047428:Protein Kinase Inhibitors; C401859:temsirolimus; D051058:Oncogene Protein v-akt; D058570:TOR Serine-Threonine Kinases; D020123:Sirolimus