title: Induction of adipocyte-specific gene expression is correlated with mammary tumor regression by the retinoid X receptor-ligand LGD1069 (targretin).
abstract: Targretin (LGD1069; a high-affinity ligand for the retinoid X receptors) is an efficacious chemotherapeutic and chemopreventive agent in the N-nitroso-N-methylurea-induced rat mammary carcinoma model. To evaluate the molecular action of LGD1069 in mammary carcinoma we have examined gene expression patterns in controls and nonresponding tumors compared with tumors undergoing regression (responding) by LGD1069. When compared with controls or nonresponding tumors, the expression of adipocyte-related genes such as adipocyte P2 (aP2), adipsin, peroxisome proliferator-activated receptor gamma (PPARgamma), and lipoprotein lipase was elevated in LGD1069-responding tumors. Further analysis showed that gene expression changes occurred rapidly, in as little as 6 h, after the first dose of LGD1069. Immunohistochemical analysis showed that aP2 protein was also highly expressed in responding tumors when compared with control or nonresponding tumors. More importantly, aP2 protein was localized in the tumor cells in addition to the adipocytes present in the tumors. Similar changes in gene expression and inhibition in growth were seen in tumor cells (cloned from N-nitroso-N-methylurea-induced carcinoma) exposed to LGD1069 in vitro. These data suggest that tumor regression by LGD1069 involves differentiation induction along the adipocyte lineage.
authors.affiliation: Department of Nuclear Receptor Discovery, Ligand Pharmaceuticals Inc., San Diego, California 92121, USA.
authors.forename: V R
authors.initials: VR
authors.lastname: Agarwal
authors.forename: E D
authors.initials: ED
authors.lastname: Bischoff
authors.forename: T
authors.initials: T
authors.lastname: Hermann
authors.forename: W W
authors.initials: WW
authors.lastname: Lamph
mesh_terms: D033962:Adaptor Protein Complex 2; D033965:Adaptor Protein Complex alpha Subunits; D033942:Adaptor Proteins, Vesicular Transport; D017667:Adipocytes / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D000818:Animals; D016588:Anticarcinogenic Agents / Q000494:pharmacology*; D000077610:Bexarotene; D002273:Carcinogens; D002454:Cell Differentiation / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D002999:Clone Cells; D011416:Complement Factor D; D005260:Female; D015870:Gene Expression / Q000187:drug effects; D006131:Growth Inhibitors / Q000494:pharmacology; D008024:Ligands; D008071:Lipoprotein Lipase / Q000096:biosynthesis / Q000235:genetics; D008325:Mammary Neoplasms, Experimental / Q000188:drug therapy* / Q000235:genetics / Q000473:pathology; D008565:Membrane Proteins / Q000096:biosynthesis / Q000235:genetics; D008770:Methylnitrosourea; D051381:Rats; D017207:Rats, Sprague-Dawley; D018160:Receptors, Cytoplasmic and Nuclear / Q000096:biosynthesis / Q000235:genetics; D018168:Receptors, Retinoic Acid / Q000819:agonists* / Q000378:metabolism; D047488:Retinoid X Receptors; D012697:Serine Endopeptidases / Q000096:biosynthesis / Q000235:genetics; D013764:Tetrahydronaphthalenes / Q000494:pharmacology*; D014157:Transcription Factors / Q000819:agonists* / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D014407:Tumor Cells, Cultured
chemical_list: D033962:Adaptor Protein Complex 2; D033965:Adaptor Protein Complex alpha Subunits; D033942:Adaptor Proteins, Vesicular Transport; D016588:Anticarcinogenic Agents; D002273:Carcinogens; D006131:Growth Inhibitors; D008024:Ligands; D008565:Membrane Proteins; D018160:Receptors, Cytoplasmic and Nuclear; D018168:Receptors, Retinoic Acid; D047488:Retinoid X Receptors; D013764:Tetrahydronaphthalenes; D014157:Transcription Factors; D008770:Methylnitrosourea; D000077610:Bexarotene; D008071:Lipoprotein Lipase; D012697:Serine Endopeptidases; D011416:Complement Factor D