title: KLF4-SQSTM1/p62-associated prosurvival autophagy contributes to carfilzomib resistance in multiple myeloma models.
abstract: Multiple myeloma (MM) is an incurable clonal plasma cell malignancy. Because of a high rate of immunoglobulin synthesis, the endoplasmic reticulum of MM cells is subjected to elevated basal levels of stress. Consequently, proteasome inhibitors, which exacerbate this stress by inhibiting ubiquitin-proteasome-mediated protein degradation, are an important new class of chemotherapeutic agents being used to combat this disease. However, MM cells still develop resistance to proteasome inhibitors such as carfilzomib. Toward this end, we have established carfilzomib-resistant derivatives of MM cell lines. We found that resistance to carfilzomib was associated with elevated levels of prosurvival autophagy, and Kruppel-like factor 4 (KLF4) was identified as a contributing factor. Expression levels as well as nuclear localization of KLF4 protein were elevated in MM cells with acquired carfilzomib resistance. Chromatin immunoprecipitations indicated that endogenous KLF4 bound to the promoter regions of the SQSTM1 gene encoding the ubiquitin-binding adaptor protein sequestosome/p62 that links the proteasomal and autophagic protein degradation pathways. Ectopic expression of KLF4 induced upregulation of SQSTM1. On the other hand, inhibitors of autophagy sensitized MM cells to carfilzomib, even in carfilzomib-resistant derivatives having increased expression of the multidrug resistance protein P-glycoprotein. Thus, we report here a novel function for KLF4, one of the Yamanaka reprogramming factors, as being a contributor to autophagy gene expression which moderates preclinical proteasome inhibitor efficacy in MM.
authors.affiliation: Department of Anatomy and Regenerative Biology, The George Washington University, Washington, DC, USA.
authors.forename: Irene
authors.initials: I
authors.lastname: Riz
authors.affiliation: Flow Cytometry Core Facility, The George Washington University, Washington, DC, USA.
authors.forename: Teresa S
authors.initials: TS
authors.lastname: Hawley
authors.affiliation: Department of Anatomy and Regenerative Biology, The George Washington University, Washington, DC, USA.
authors.forename: Robert G
authors.initials: RG
authors.lastname: Hawley
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics* / Q000378:metabolism; D001343:Autophagy / Q000187:drug effects / Q000235:genetics*; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects / Q000235:genetics; D002738:Chloroquine / Q000494:pharmacology; D019008:Drug Resistance, Neoplasm / Q000235:genetics; D020869:Gene Expression Profiling / Q000379:methods; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D011495:Histone-Lysine N-Methyltransferase / Q000235:genetics / Q000378:metabolism; D006801:Humans; D000090062:Kruppel-Like Factor 4; D051741:Kruppel-Like Transcription Factors / Q000235:genetics* / Q000378:metabolism; D018613:Microscopy, Confocal; D009101:Multiple Myeloma / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D009842:Oligopeptides / Q000494:pharmacology*; D011379:Prognosis; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000071456:Sequestosome-1 Protein; D016019:Survival Analysis
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C000715467:KLF4 protein, human; D000090062:Kruppel-Like Factor 4; D051741:Kruppel-Like Transcription Factors; D009842:Oligopeptides; D012097:Repressor Proteins; C099718:SQSTM1 protein, human; D000071456:Sequestosome-1 Protein; C524865:carfilzomib; D002738:Chloroquine; D011495:Histone-Lysine N-Methyltransferase; C419586:NSD2 protein, human
keywords: KLF4; autophagy; carfilzomib; multiple myeloma; proteasome inhibitor