title: Mutated in colorectal cancer (MCC) is a novel oncogene in B lymphocytes.
abstract: BACKGROUND
  Identification of novel genetic risk factors is imperative for a better understanding of B lymphomagenesis and for the development of novel therapeutic strategies. TRAF3, a critical regulator of B cell survival, was recently recognized as a tumor suppressor gene in B lymphocytes. The present study aimed to identify novel oncogenes involved in malignant transformation of TRAF3-deficient B cells.
  
  
  METHODS
  We used microarray analysis to identify genes differentially expressed in TRAF3-/- mouse splenic B lymphomas. We employed lentiviral vector-mediated knockdown or overexpression to manipulate gene expression in human multiple myeloma (MM) cell lines. We analyzed cell apoptosis and proliferation using flow cytometry, and performed biochemical studies to investigate signaling mechanisms. To delineate protein-protein interactions, we applied affinity purification followed by mass spectrometry-based sequencing.
  
  
  RESULTS
  We identified mutated in colorectal cancer (MCC) as a gene strikingly up-regulated in TRAF3-deficient mouse B lymphomas and human MM cell lines. Aberrant up-regulation of MCC also occurs in a variety of primary human B cell malignancies, including non-Hodgkin lymphoma (NHL) and MM. In contrast, MCC expression was not detected in normal or premalignant TRAF3-/- B cells even after treatment with B cell stimuli, suggesting that aberrant up-regulation of MCC is specifically associated with malignant transformation of B cells. In elucidating the functional roles of MCC in malignant B cells, we found that lentiviral shRNA vector-mediated knockdown of MCC induced apoptosis and inhibited proliferation in human MM cells. Experiments of knockdown and overexpression of MCC allowed us to identify several downstream targets of MCC in human MM cells, including phospho-ERK, c-Myc, p27, cyclin B1, Mcl-1, caspases 8 and 3. Furthermore, we identified 365 proteins (including 326 novel MCC-interactors) in the MCC interactome, among which PARP1 and PHB2 were two hubs of MCC signaling pathways in human MM cells.
  
  
  CONCLUSIONS
  Our results indicate that in sharp contrast to its tumor suppressive role in colorectal cancer, MCC functions as an oncogene in B cells. Our findings suggest that MCC may serve as a diagnostic marker and therapeutic target in B cell malignancies, including NHL and MM.
authors.forename: Shanique K E
authors.initials: SK
authors.lastname: Edwards
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Baron
authors.forename: Carissa R
authors.initials: CR
authors.lastname: Moore
authors.forename: Yan
authors.initials: Y
authors.lastname: Liu
authors.forename: David H
authors.initials: DH
authors.lastname: Perlman
authors.forename: Ronald P
authors.initials: RP
authors.lastname: Hart
authors.forename: Ping
authors.initials: P
authors.lastname: Xie
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000235:genetics; D001402:B-Lymphocytes / Q000473:pathology*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000235:genetics; D002471:Cell Transformation, Neoplastic / Q000235:genetics*; D047369:Chromatin Immunoprecipitation; D005434:Flow Cytometry; D017431:Genes, MCC / Q000235:genetics*; D006801:Humans; D015151:Immunoblotting; D047468:Immunoprecipitation; D008228:Lymphoma, Non-Hodgkin / Q000235:genetics; D051379:Mice; D018345:Mice, Knockout; D009101:Multiple Myeloma / Q000235:genetics; D020411:Oligonucleotide Array Sequence Analysis; D009857:Oncogenes / Q000235:genetics*; D000091402:Prohibitins; D020133:Reverse Transcriptase Polymerase Chain Reaction; D048008:TNF Receptor-Associated Factor 3 / Q000172:deficiency; D053719:Tandem Mass Spectrometry
chemical_list: C000717331:PHB2 protein, human; C000717333:Phb2 protein, mouse; D000091402:Prohibitins; D048008:TNF Receptor-Associated Factor 3