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: Osamu Nakamura, Toshiaki Hitora, Toshihiro Akisue, Teruya Kawamoto, Yoshiki Yamagami, Tetsuji Yamamoto
• Journal: International journal of oncology (Int J Oncol) Vol. 39 Issue 6 Pg. 1545-52 (Dec 2011) ISSN: 1791-2423 [Electronic] Greece
• PMID: 21805033 (Publication Type: Journal Article)

Chemical References

• Protein Kinase Inhibitors
• temsirolimus
• Oncogene Protein v-akt
• TOR Serine-Threonine Kinases
• Sirolimus

Topics

• Apoptosis (drug effects)
• Autophagy (drug effects)
• Cell Cycle (drug effects)
• Cell Line, Tumor
• Cell Proliferation (drug effects)
• Histiocytoma, Malignant Fibrous (metabolism)
• Humans
• Microscopy, Fluorescence
• Oncogene Protein v-akt (metabolism)
• Protein Kinase Inhibitors (pharmacology)
• Signal Transduction (drug effects)
• Sirolimus (analogs & derivatives, pharmacology)
• Staining and Labeling
• TOR Serine-Threonine Kinases (antagonists & inhibitors)