title: PC cell-derived growth factor confers resistance to dexamethasone and promotes tumorigenesis in human multiple myeloma.
abstract: OBJECTIVE
  We have shown previously that the 88 kDa glycoprotein PC cell-derived growth factor (PCDGF/GP88) is expressed and acts as an autocrine growth factor in human multiple myeloma cells. The present study investigates whether PCDGF/GP88 expression in multiple myeloma cells leads to the development of resistance to dexamethasone, a conventional drug for multiple myeloma patients.
  
  
  METHODS
  PCDGF functions and signaling pathways in dexamethasone-induced apoptosis were studied using a representative dexamethasone-sensitive multiple myeloma cell line ARP-1. The effect of PCDGF/GP88 was further confirmed in PCDGF/GP88-overexpressed ARP-1 cells.
  
  
  RESULTS
  Dexamethasone inhibits cell growth and induces apoptosis in a time- and dose-dependent fashion. Exogenous addition of PCDGF/GP88 to the ARP-1 cells prevented dexamethasone-induced apoptosis as examined by flow cytometry analysis and poly(ADP-ribose)polymerase cleavage assay. Signaling studies showed that mitogen-activated protein kinase, phosphatidylinositol 3-kinase, and nuclear factor-kappaB were involved in the antiapoptotic effect of PCDGF/GP88. Overexpression of PCDGF/GP88 in ARP-1 cells rendered the cells refractory to dexamethasone-mediated apoptosis, enhanced their ability to form colonies in soft agar, and to form tumors in vivo without any change in glucocorticoid receptor expression and function.
  
  
  CONCLUSIONS
  These data suggest that expression of PCDGF/GP88 confers resistance to dexamethasone and increase tumorigenesis of multiple myeloma cells in mouse xenografts. Our data here also raises the possibility of PCDGF/GP88 as a potential therapeutic target for dexamethasone-resistant multiple myeloma.
authors.affiliation: Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Maryland, USA.
authors.forename: Wengang
authors.initials: W
authors.lastname: Wang
authors.forename: Jun
authors.initials: J
authors.lastname: Hayashi
authors.forename: Ginette
authors.initials: G
authors.lastname: Serrero
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D045744:Cell Line, Tumor; D003907:Dexamethasone / Q000494:pharmacology*; D019008:Drug Resistance, Neoplasm / Q000187:drug effects / Q000502:physiology*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005434:Flow Cytometry; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000378:metabolism*; D009101:Multiple Myeloma / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000077153:Progranulins
chemical_list: D000970:Antineoplastic Agents; D036341:Intercellular Signaling Peptides and Proteins; D016328:NF-kappa B; D000077153:Progranulins; D003907:Dexamethasone; D019869:Phosphatidylinositol 3-Kinases; D048049:Extracellular Signal-Regulated MAP Kinases