title: Nimbolide sensitizes human colon cancer cells to TRAIL through reactive oxygen species- and ERK-dependent up-regulation of death receptors, p53, and Bax.
abstract: TNF-related apoptosis-inducing ligand (TRAIL) shows promise as a cancer treatment, but acquired tumor resistance to TRAIL is a roadblock. Here we investigated whether nimbolide, a limonoid, could sensitize human colon cancer cells to TRAIL. As indicated by assays that measure esterase activity, sub-G(1) fractions, mitochondrial activity, and activation of caspases, nimbolide potentiated the effect of TRAIL. This limonoid also enhanced expression of death receptors (DRs) DR5 and DR4 in cancer cells. Gene silencing of the receptors reduced the effect of limonoid on TRAIL-induced apoptosis. Using pharmacological inhibitors, we found that activation of ERK and p38 MAPK was required for DR up-regulation by nimbolide. Gene silencing of ERK abolished the enhancement of TRAIL-induced apoptosis. Moreover, our studies indicate that the limonoid induced reactive oxygen species production, which was required for ERK activation, up-regulation of DRs, and sensitization to TRAIL; these effects were mimicked by H(2)O(2). In addition, nimbolide down-regulated cell survival proteins, including I-FLICE, cIAP-1, cIAP-2, Bcl-2, Bcl-xL, survivin, and X-linked inhibitor of apoptosis protein, and up-regulated the pro-apoptotic proteins p53 and Bax. Interestingly, p53 and Bax up-regulation by nimbolide was required for sensitization to TRAIL but not for DR up-regulation. Overall, our results indicate that nimbolide can sensitize colon cancer cells to TRAIL-induced apoptosis through three distinct mechanisms: reactive oxygen species- and ERK-mediated up-regulation of DR5 and DR4, down-regulation of cell survival proteins, and up-regulation of p53 and Bax.
authors.affiliation: Cytokine Research Laboratory, Department of Experimental Therapeutics, The University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030, USA.
authors.forename: Subash C
authors.initials: SC
authors.lastname: Gupta
authors.forename: Simone
authors.initials: S
authors.lastname: Reuter
authors.forename: Kanokkarn
authors.initials: K
authors.lastname: Phromnoi
authors.forename: Byoungduck
authors.initials: B
authors.lastname: Park
authors.forename: Padmanabhan S
authors.initials: PS
authors.lastname: Hema
authors.forename: Mangalam
authors.initials: M
authors.lastname: Nair
authors.forename: Bharat B
authors.initials: BB
authors.lastname: Aggarwal
mesh_terms: D000230:Adenocarcinoma / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D001943:Breast Neoplasms; D003110:Colonic Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D045325:HCT116 Cells; D019073:HT29 Cells; D006801:Humans; D007680:Kidney Neoplasms; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive; D036701:Limonins / Q000494:pharmacology*; D008175:Lung Neoplasms; D009101:Multiple Myeloma; D010190:Pancreatic Neoplasms; D017382:Reactive Oxygen Species / Q000378:metabolism; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand / Q000378:metabolism; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000378:metabolism*; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D051028:bcl-2-Associated X Protein / Q000378:metabolism
chemical_list: D000970:Antineoplastic Agents; D036701:Limonins; D017382:Reactive Oxygen Species; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D053221:TNF-Related Apoptosis-Inducing Ligand; C105190:TNFRSF10A protein, human; C505653:TNFSF10 protein, human; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; D051028:bcl-2-Associated X Protein; C042198:nimbolide; D048049:Extracellular Signal-Regulated MAP Kinases