title: Up-regulation of Mcl-1 is critical for survival of human melanoma cells upon endoplasmic reticulum stress.
abstract: We have previously shown that most melanoma cell lines are insensitive to endoplasmic reticulum (ER) stress-induced apoptosis, and this involves activation of the mitogen-activated protein/extracellular signal-regulated kinase (MEK)/ERK signaling pathway and expression of the apoptosis repressor with caspase recruitment domain (ARC) protein in the cells. In the present study, we show that up-regulation of the antiapoptotic Bcl-2 family member Mcl-1 is another mechanism critical for protection of melanoma cells against ER stress-induced apoptosis. Inhibition of Mcl-1 by small interference RNA (siRNA) rendered melanoma cells sensitive to apoptosis induced by the ER stress inducers thapsigargin and tunicamycin, but this sensitization was partially reversed by siRNA knockdown of PUMA or Noxa, as shown in Mcl-1-deficient melanoma cells. Both PUMA and Noxa were increased by ER stress through transcriptional up-regulation, but only up-regulation of Noxa was dependent on p53, whereas up-regulation of PUMA seemed to be mediated by a p53-independent mechanism(s). Up-regulation of Mcl-1 was also due to increased transcription that involved the IRE1alpha and activating transcription factor 6 signaling pathways of the unfolded protein response. In addition, activation of the MEK/ERK signaling pathway seemed to be necessary for optimal up-regulation of Mcl-1. Taken together, these results reveal the mechanisms of resistance of melanoma cells to apoptosis induction mediated by BH3-only proteins upon ER stress, and identify Mcl-1 as a target for the treatment of melanoma in combination with therapeutics that induce ER stress.
authors.affiliation: Immunology and Oncology Unit, Calvary Mater Newcastle Hospital, New South Wales, Australia.
authors.forename: Chen Chen
authors.initials: CC
authors.lastname: Jiang
authors.forename: Keryn
authors.initials: K
authors.lastname: Lucas
authors.forename: Kelly A
authors.initials: KA
authors.lastname: Avery-Kiejda
authors.forename: Margaret
authors.initials: M
authors.lastname: Wade
authors.forename: Charles E
authors.initials: CE
authors.lastname: deBock
authors.forename: Rick F
authors.initials: RF
authors.lastname: Thorne
authors.forename: John
authors.initials: J
authors.lastname: Allen
authors.forename: Peter
authors.initials: P
authors.lastname: Hersey
authors.forename: Xu Dong
authors.initials: XD
authors.lastname: Zhang
mesh_terms: D051702:Activating Transcription Factor 6 / Q000235:genetics / Q000378:metabolism; D000998:Antiviral Agents / Q000494:pharmacology; D017209:Apoptosis / Q000502:physiology*; D051017:Apoptosis Regulatory Proteins / Q000235:genetics / Q000378:metabolism; D015153:Blotting, Western; D004721:Endoplasmic Reticulum / Q000502:physiology*; D004722:Endoribonucleases / Q000235:genetics / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005434:Flow Cytometry; D006801:Humans; D008545:Melanoma / Q000378:metabolism / Q000473:pathology*; D053078:Membrane Potential, Mitochondrial; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D018384:Oxidative Stress; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000494:pharmacology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D012878:Skin Neoplasms / Q000378:metabolism / Q000473:pathology*; D019284:Thapsigargin / Q000494:pharmacology; D014158:Transcription, Genetic; D014162:Transfection; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism; D014415:Tunicamycin / Q000494:pharmacology; D015854:Up-Regulation
chemical_list: C497111:ATF6 protein, human; D051702:Activating Transcription Factor 6; D000998:Antiviral Agents; D051017:Apoptosis Regulatory Proteins; C438378:BBC3 protein, human; D004791:Enzyme Inhibitors; D064549:Myeloid Cell Leukemia Sequence 1 Protein; C498702:PMAIP1 protein, human; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D016159:Tumor Suppressor Protein p53; D014415:Tunicamycin; D019284:Thapsigargin; C528229:ERN1 protein, human; D017346:Protein Serine-Threonine Kinases; D004722:Endoribonucleases