title: Retinoid and thiazolidinedione therapies in melanoma: an analysis of differential response based on nuclear hormone receptor expression.
abstract: BACKGROUND
  Metastatic melanoma has a high mortality rate and suboptimal therapeutic options. Molecular targeting may be beneficial using the rexinoid LGD1069, a retinoid x receptor selective agonist, and thiazolidinediones (TZD), PPARgamma selective ligands, as novel treatments.
  
  
  RESULTS
  Mouse xenograft models with human melanoma cell lines [A375(DRO) or M14(5-16)] were treated for 4 weeks with daily vehicle, RXR agonist (rexinoid, LGD1069, 30 mg/kg/d), PPARgamma agonist (TZD, rosiglitazone, 10 mg/kg/d) or combination. A375(DRO) tumor growth was significantly inhibited by either ligand alone and the combination had an additive effect. M14(5-16) tumors only responded to LGD1069 100 mg/kg/day. A375(DRO) sublines resistant to rexinoid, TZD and combination were generated and all three sublines had reduced PPARgamma expression but preserved RXR expression. shRNA knockdown of PPARgamma or RXRgamma attenuated the rexinoid, TZD and combination ligand-mediated decreased proliferation in A375(DRO) cells. Rexinoid (LGD1069) and retinoid (TTNPB) treatment of M14(5-16) cells resulted in decreased proliferation that was additive with combination of both rexinoid and retinoid. shRNA knockdown of RXRgamma resulted in a decreased response to either ligand.
  
  
  CONCLUSIONS
  A375 (DRO) melanoma cell growth is inhibited by rexinoid and TZD treatment, and this response is dependent on RXR and PPARgamma receptor expression. M14 (5-16) melanoma cell growth is inhibited by rexinoid and retinoid treatment, and this response is dependent on RXR expression. These findings may help guide molecular-based treatment strategies in melanoma and provide insight for mechanisms of resistance to nuclear receptor targeted therapies in certain cancers.
authors.affiliation: Department of Medicine, Division of Endocrinology, Metabolism and Diabetes, University of Colorado Denver, Aurora, CO, USA. joshua.klopper@ucdenver.edu
authors.forename: Joshua P
authors.initials: JP
authors.lastname: Klopper
authors.forename: Vibha
authors.initials: V
authors.lastname: Sharma
authors.forename: Andrew
authors.initials: A
authors.lastname: Berenz
authors.forename: William R
authors.initials: WR
authors.lastname: Hays
authors.forename: Michele
authors.initials: M
authors.lastname: Loi
authors.forename: Umarani
authors.initials: U
authors.lastname: Pugazhenthi
authors.forename: Sherif
authors.initials: S
authors.lastname: Said
authors.forename: Bryan R
authors.initials: BR
authors.lastname: Haugen
mesh_terms: D000818:Animals; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology / Q000627:therapeutic use*; D001565:Benzoates / Q000494:pharmacology / Q000627:therapeutic use; D000077610:Bexarotene; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D019008:Drug Resistance, Neoplasm / Q000187:drug effects; D006801:Humans; D008024:Ligands; D008545:Melanoma / Q000188:drug therapy* / Q000378:metabolism* / Q000473:pathology; D051379:Mice; D047495:PPAR gamma / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism*; D047488:Retinoid X Receptors / Q000378:metabolism; D012176:Retinoids / Q000494:pharmacology / Q000627:therapeutic use*; D000077154:Rosiglitazone; D013764:Tetrahydronaphthalenes / Q000494:pharmacology / Q000627:therapeutic use; D045162:Thiazolidinediones / Q000494:pharmacology / Q000627:therapeutic use*; D023041:Xenograft Model Antitumor Assays
chemical_list: D001565:Benzoates; D008024:Ligands; D047495:PPAR gamma; D034741:RNA, Small Interfering; D018160:Receptors, Cytoplasmic and Nuclear; D047488:Retinoid X Receptors; D012176:Retinoids; D013764:Tetrahydronaphthalenes; D045162:Thiazolidinediones; D000077154:Rosiglitazone; C038864:4-(2-(5,6,7,8-tetrahydro-5,5,8,8-tetramethyl-2-naphthalenyl)-1-propenyl)benzoic acid; D000077610:Bexarotene