Mol. Cells 2011; 31(3): 231-238
Published online January 21, 2011
https://doi.org/10.1007/s10059-011-0034-6
© The Korean Society for Molecular and Cellular Biology
Correspondence to : *Correspondence: mikelee@incheon.ac.kr
The effectiveness of an apoptosis-targeting therapy may be limited in tumor cells with defects in apoptosis. Recen-tly, considerable attention in the field of cancer therapy has been focused on the mammalian rapamycin target (mTOR), inhibition of which results in autophagic cell death. In our study using multidrug-resistant v-Ha-ras-transformed NIH3T3 (Ras-NIH 3T3/Mdr) cells, we demon-strated that rapamycin-induced cell death may result from 2 different mechanisms. At high rapamycin concentrations (≥100 nM), cell death may occur via an autophagy-depen-dent pathway, whereas at lower concentrations (≤ 10 nM), cell death may occur after G1-phase cell cycle arrest. This effect was accompanied by upregulation of p21Cip1 and p27Kip1 expression via an autophagy-independent pathway. We also tested whether inhibition of mTOR with low con-centrations of rapamycin and ectopic Beclin-1 expression would further sensitize multidrug resistance (MDR)-posi-tive cancer cells by upregulating autophagy. Rapamycin at low concentrations might be insufficient to initiate auto-phagosome formation in autophagy but Beclin-1 overex-pression triggered additional processes downstream of mTOR during G1 cell cycle arrest by rapamycin. Our find-ings suggest that these combination strategies targeting autophagic cell death may yield significant benefits for cancer patients, because lowering rapamycin concentra-tion for cancer treatment minimizes its side effects in pa-tients undergoing chemotherapy.
Keywords autophagy, Beclin 1, chemotherapy, MDR, Rapamycin
Mol. Cells 2011; 31(3): 231-238
Published online March 31, 2011 https://doi.org/10.1007/s10059-011-0034-6
Copyright © The Korean Society for Molecular and Cellular Biology.
Ki-Hwan Eum, and Michael Lee*
Division of Life Sciences, College of Natural Sciences, University of Incheon, Incheon 406-772, Korea
Correspondence to:*Correspondence: mikelee@incheon.ac.kr
The effectiveness of an apoptosis-targeting therapy may be limited in tumor cells with defects in apoptosis. Recen-tly, considerable attention in the field of cancer therapy has been focused on the mammalian rapamycin target (mTOR), inhibition of which results in autophagic cell death. In our study using multidrug-resistant v-Ha-ras-transformed NIH3T3 (Ras-NIH 3T3/Mdr) cells, we demon-strated that rapamycin-induced cell death may result from 2 different mechanisms. At high rapamycin concentrations (≥100 nM), cell death may occur via an autophagy-depen-dent pathway, whereas at lower concentrations (≤ 10 nM), cell death may occur after G1-phase cell cycle arrest. This effect was accompanied by upregulation of p21Cip1 and p27Kip1 expression via an autophagy-independent pathway. We also tested whether inhibition of mTOR with low con-centrations of rapamycin and ectopic Beclin-1 expression would further sensitize multidrug resistance (MDR)-posi-tive cancer cells by upregulating autophagy. Rapamycin at low concentrations might be insufficient to initiate auto-phagosome formation in autophagy but Beclin-1 overex-pression triggered additional processes downstream of mTOR during G1 cell cycle arrest by rapamycin. Our find-ings suggest that these combination strategies targeting autophagic cell death may yield significant benefits for cancer patients, because lowering rapamycin concentra-tion for cancer treatment minimizes its side effects in pa-tients undergoing chemotherapy.
Keywords: autophagy, Beclin 1, chemotherapy, MDR, Rapamycin
Eun Seong Hwang and Seon Beom Song
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