title: NEDD8 Inhibition Overcomes CKS1B-Induced Drug Resistance by Upregulation of p21 in Multiple Myeloma.
abstract: OBJECTIVE
  CKS1B is significantly upregulated in multiple myeloma and associated with poor prognosis. The identification of novel therapies is essential for effective treatment of patients resistant to chemotherapy. The NEDD8 inhibitor MLN4924 selectively targets SCF(Skp2) activation and offers a more specific approach to protein degradation inhibition than total proteasomal inhibition. The goal of this study was to evaluate whether MLN4924 is effective in high CKS1B conditions and identify mechanisms regulating drug potency.
  
  
  METHODS
  Bortezomib and MLN4924 sensitivity was assessed through proliferation, viability, clonogenic potential, and senescence induction in cells overexpressing CKS1B. The mechanism for MLN4924 sensitivity was elucidated by immunoblot analysis of SCF(skp) substrates and confirmed by shRNA knockdown. The clinical relevance of the NEDD8 pathway was examined in gene expression profiles (GEP) derived from healthy people, patients with monoclonal gammopathy of undetermined significance (MGUS), and multiple myeloma.
  
  
  RESULTS
  Cells overexpressing CKS1B were resistant to bortezomib but sensitive to MLN4924. Treatment of CKS1B-overexpressing cells with MLN4924 decreased proliferation, clonogenicity, and induced senescence. MLN4924, but not bortezomib, induced stabilization of p21 and knockdown of p21 resulted in loss of MLN4924 sensitivity. Patients with MGUS and multiple myeloma exhibited increased expression of NEDD8 pathway genes relative to normal plasma cells. Multiple myeloma patients with high NEDD8 expression were linked to bortezomib resistance in clinical trials, and had inferior outcomes.
  
  
  CONCLUSIONS
  Our data demonstrate that cells with elevated CKS1B expression are resistant to bortezomib but sensitive to MLN4924 and offer a mechanism through the stabilization of p21. These findings provide rationale for targeting the NEDD8 pathway in multiple myeloma patients exhibiting elevated expression of CKS1B. Clin Cancer Res; 21(24); 5532-42. ©2015 AACR.
authors.affiliation: Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, Iowa. Institute of Cancer Research, School of Basic Medical Sciences, Southern Medical University, Guangzhou, China.
authors.forename: Junwei
authors.initials: J
authors.lastname: Huang
authors.affiliation: Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, Iowa.
authors.forename: Yi
authors.initials: Y
authors.lastname: Zhou
authors.affiliation: Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, Iowa.
authors.forename: Gregory S
authors.initials: GS
authors.lastname: Thomas
authors.affiliation: Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, Iowa.
authors.forename: Zhimin
authors.initials: Z
authors.lastname: Gu
authors.affiliation: Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, Iowa.
authors.forename: Ye
authors.initials: Y
authors.lastname: Yang
authors.affiliation: Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, Iowa.
authors.forename: Hongwei
authors.initials: H
authors.lastname: Xu
authors.affiliation: Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, Iowa.
authors.forename: Guido
authors.initials: G
authors.lastname: Tricot
authors.affiliation: Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, Iowa. fenghuang-zhan@uiowa.edu.
authors.forename: Fenghuang
authors.initials: F
authors.lastname: Zhan
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology / Q000627:therapeutic use; D017209:Apoptosis / Q000187:drug effects; D000069286:Bortezomib / Q000494:pharmacology; D042846:CDC2-CDC28 Kinases / Q000235:genetics* / Q000378:metabolism; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000235:genetics / Q000378:metabolism*; D003517:Cyclopentanes / Q000494:pharmacology* / Q000627:therapeutic use; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D006801:Humans; D053208:Kaplan-Meier Estimate; D009101:Multiple Myeloma / Q000188:drug therapy / Q000235:genetics* / Q000378:metabolism / Q000401:mortality; D000075687:NEDD8 Protein; D059748:Proteolysis; D011743:Pyrimidines / Q000494:pharmacology* / Q000627:therapeutic use; D015398:Signal Transduction / Q000187:drug effects; D014452:Ubiquitins / Q000037:antagonists & inhibitors* / Q000378:metabolism
chemical_list: D000970:Antineoplastic Agents; C093090:CKS1B protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D003517:Cyclopentanes; D000075687:NEDD8 Protein; C082860:NEDD8 protein, human; D011743:Pyrimidines; D014452:Ubiquitins; D000069286:Bortezomib; D042846:CDC2-CDC28 Kinases; C539933:pevonedistat