title: Effects of novel retinoid X receptor-selective ligands on myeloid leukemia differentiation and proliferation in vitro.
abstract: The biologic effects of retinoids such as all-trans-retinoic acid (ATRA) and 9-cis-retinoic acid on proliferation and differentiation of hematopoietic cells are mediated by binding and activating two distinct families of transcription factors: the retinoic acid receptors (RARs) and the retinoid X receptors (RXRs). The RARs require heterodimerization with RXRs; in addition, RXRs can form homodimers, which can bind to DNA response elements that are either distinct or the same as those bound by the RAR/RXR heterodimers. Therefore, the two retinoid pathways provide sequences that are specific for effective DNA binding and activation of target genes. We have developed several series of novel synthetic retinoids that selectively interact with RXR/RXR homodimers and RAR/RXR heterodimers. We show here that SR11236 and SR11246, which are RXR-selective analogs, had little ability to inhibit clonal growth and induce differentiation of leukemic cells (HL-60 cells and fresh acute myeloid leukemia cells). However, SR11249, SR11256, and LGD1069, which activated both RXR/RXR homodimers and RAR/RXR heterodimers, could inhibit clonal growth and induce differentiation of HL-60 cells as well as leukemic cells from patients, including those with acute promyelocytic leukemia (APL). This is similar to results observed with RAR/RXR-specific ligands. Interestingly, the combination of ATRA and either SR11249, SR11256, or LGD1069 showed synergistic effects in inducing differentiation of HL-60 cells. A retinoid (SR11238) with strong anti-AP-1 activity that did not activate the RARs and RXRs for gene transcription from the response element TREpal was inactive in our assay systems, suggesting that the antiproliferative effects of retinoids on leukemic cells is not mediated by inhibiting the AP-1 pathway. We conclude that the RAR/RXR pathway is more important than RXR/RXR pathway for differentiation and proliferation of acute myeloid leukemic cells, and certain retinoids or combination of retinoids with both RAR and RXR specificities may synergistically enhance the differentiation activity of ATRA, which may be relevant in several clinical situations.
authors.affiliation: Division of Hematology, Keio University School of Medicine, Tokyo, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Kizaki
authors.forename: M I
authors.initials: MI
authors.lastname: Dawson
authors.forename: R
authors.initials: R
authors.lastname: Heyman
authors.forename: E
authors.initials: E
authors.lastname: Elster
authors.forename: R
authors.initials: R
authors.lastname: Morosetti
authors.forename: S
authors.initials: S
authors.lastname: Pakkala
authors.forename: D L
authors.initials: DL
authors.lastname: Chen
authors.forename: H
authors.initials: H
authors.lastname: Ueno
authors.forename: W
authors.initials: W
authors.lastname: Chao
authors.forename: M
authors.initials: M
authors.lastname: Morikawa
authors.forename: Y
authors.initials: Y
authors.lastname: Ikeda
authors.forename: D
authors.initials: D
authors.lastname: Heber
authors.forename: M
authors.initials: M
authors.lastname: Pfahl
authors.forename: H P
authors.initials: HP
authors.lastname: Koeffler
mesh_terms: D000077610:Bexarotene; D015415:Biomarkers; D002454:Cell Differentiation / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D004357:Drug Synergism; D015973:Gene Expression Regulation, Leukemic / Q000187:drug effects; D018922:HL-60 Cells / Q000187:drug effects; D006801:Humans; D008024:Ligands; D016177:Macrophage-1 Antigen / Q000096:biosynthesis / Q000235:genetics; D015394:Molecular Structure; D009363:Neoplasm Proteins / Q000096:biosynthesis / Q000187:drug effects* / Q000235:genetics; D014411:Neoplastic Stem Cells / Q000187:drug effects* / Q000473:pathology; D055503:Protein Multimerization; D018168:Receptors, Retinoic Acid / Q000737:chemistry / Q000187:drug effects*; D000072482:Retinoic Acid Receptor alpha; D047488:Retinoid X Receptors; D012176:Retinoids / Q000138:chemical synthesis / Q000494:pharmacology*; D015398:Signal Transduction / Q000187:drug effects; D013764:Tetrahydronaphthalenes / Q000138:chemical synthesis / Q000494:pharmacology*; D018808:Transcription Factor AP-1 / Q000378:metabolism; D014157:Transcription Factors / Q000737:chemistry / Q000187:drug effects*; D014212:Tretinoin / Q000494:pharmacology*; D014407:Tumor Cells, Cultured / Q000187:drug effects
chemical_list: D015415:Biomarkers; D008024:Ligands; D016177:Macrophage-1 Antigen; D009363:Neoplasm Proteins; C000607071:RARA protein, human; D018168:Receptors, Retinoic Acid; D000072482:Retinoic Acid Receptor alpha; D047488:Retinoid X Receptors; D012176:Retinoids; D013764:Tetrahydronaphthalenes; D018808:Transcription Factor AP-1; D014157:Transcription Factors; D014212:Tretinoin; D000077610:Bexarotene