title: Targeting the autophagy pathway using ectopic expression of Beclin 1 in combination with rapamycin in drug-resistant v-Ha-ras-transformed NIH 3T3 cells.
abstract: The effectiveness of an apoptosis-targeting therapy may be limited in tumor cells with defects in apoptosis. Recently, 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 demonstrated that rapamycin-induced cell death may result from 2 different mechanisms. At high rapamycin concentrations (≥ 100 nM), cell death may occur via an autophagy-dependent pathway, whereas at lower concentrations (≤ 10 nM), cell death may occur after G1-phase cell cycle arrest. This effect was accompanied by upregulation of p21(Cip1) and p27(Kip1) expression via an autophagy-independent pathway. We also tested whether inhibition of mTOR with low concentrations of rapamycin and ectopic Beclin-1 expression would further sensitize multidrug resistance (MDR)-positive cancer cells by upregulating autophagy. Rapamycin at low concentrations might be insufficient to initiate autophagosome formation in autophagy but Beclin-1 overexpression triggered additional processes downstream of mTOR during G(1) cell cycle arrest by rapamycin. Our findings suggest that these combination strategies targeting autophagic cell death may yield significant benefits for cancer patients, because lowering rapamycin concentration for cancer treatment minimizes its side effects in patients undergoing chemotherapy.
authors.affiliation: Division of Life Sciences, College of Natural Sciences, University of Incheon, Incheon, 406-772, Korea.
authors.forename: Ki-Hwan
authors.initials: KH
authors.lastname: Eum
authors.forename: Michael
authors.initials: M
authors.lastname: Lee
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000378:metabolism; D000818:Animals; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology*; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology; D051017:Apoptosis Regulatory Proteins / Q000096:biosynthesis*; D001343:Autophagy / Q000187:drug effects*; D000071186:Beclin-1; D053148:Caspase 3 / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects; D002461:Cell Line, Transformed; D002470:Cell Survival / Q000187:drug effects; D002471:Cell Transformation, Neoplastic; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000378:metabolism; D019008:Drug Resistance, Neoplasm; D051379:Mice; D041681:NIH 3T3 Cells; D017239:Paclitaxel / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects*; D020123:Sirolimus / Q000494:pharmacology*; D018631:ras Proteins / Q000096:biosynthesis*
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000903:Antibiotics, Antineoplastic; D000972:Antineoplastic Agents, Phytogenic; D051017:Apoptosis Regulatory Proteins; D000071186:Beclin-1; C115010:Becn1 protein, mouse; C493957:Cdkn1a protein, mouse; C493961:Cdkn1b protein, mouse; D050759:Cyclin-Dependent Kinase Inhibitor p21; D050760:Cyclin-Dependent Kinase Inhibitor p27; C505409:Casp3 protein, mouse; D053148:Caspase 3; D018631:ras Proteins; D017239:Paclitaxel; D020123:Sirolimus