title: Additive Effects of Retinoic Acid (RA) and Bone Morphogenetic Protein 4 (BMP-4) Apoptosis Signaling in Retinoblastoma Cell Lines.
abstract: Retinoids have been shown to serve promising therapeutic agents for human cancers, e.g. the treatment of neuroblastoma. Synthetic retinoids, specific for particular retinoic acid (RA) receptors, are tested as new therapy strategies. In the present study, application of recombinant retinoic acid (RA) lowers retinoblastoma (RB) cell viability and induces apoptosis in RB cell lines. Combined treatment of RA and bone morphogenetic protein 4 (BMP-4) increases the pro-apoptotic effect of RA in the RB cells lines WERI-Rb1, Y-79, RB355, RBL-30 and RBL-15, indicating an additive effect. We could show that in WERI-Rb1 cells RA/BMP-4 mediated cell death is at least partially caspase-dependent, whereby RA and BMP-4 additively increased (i) Apaf-1 mRNA levels, (ii) caspase-9 cleavage activity and (iii) the number of activated, cleaved caspase-3 positive cells. Compared to single application of RA and BMP-4, combined RA/BMP-4 treatment significantly augments mRNA levels of the retinoic acid receptors (RARs) RARα and RARß and the retinoic X receptor (RXR) RXRγ suggesting an interaction in the induction of these RA receptor subtypes in WERI-Rb1 cells. Agonist studies revealed that both, RARs and RXRs are involved in RA/BMP-4 mediated apoptosis in WERI-Rb1 retinoblastoma cells. Employing specific RAR subtype antagonists and a RXRß and RXRγ knockdown, we proved that RA/BMP-4 apoptosis signaling in WERI-Rb1 cells requires the RA receptor subtypes RARα, RARß, RXRß and RXRγ. Deciphering signaling mechanisms underlying apoptosis induction of RA and BMP-4 in WERI-Rb1 cells, our study provides useful starting-points for future retinoid-based therapy strategies in retinoblastoma.
authors.affiliation: Department of Neuroanatomy, Institute for Anatomy, Medical Faculty, University of Duisburg-Essen, Essen, Germany.
authors.forename: Patrick
authors.initials: P
authors.lastname: Müller
authors.affiliation: Department of Neuroanatomy, Institute for Anatomy, Medical Faculty, University of Duisburg-Essen, Essen, Germany.
authors.forename: Rebekka
authors.initials: R
authors.lastname: Doliva
authors.affiliation: Department of Neuroanatomy, Institute for Anatomy, Medical Faculty, University of Duisburg-Essen, Essen, Germany.
authors.forename: Maike
authors.initials: M
authors.lastname: Busch
authors.affiliation: Department of Neuroanatomy, Institute for Anatomy, Medical Faculty, University of Duisburg-Essen, Essen, Germany.
authors.forename: Claudia
authors.initials: C
authors.lastname: Philippeit
authors.affiliation: Division of Haematology and Oncology, Children's Hospital, University of Duisburg-Essen, Essen, Germany.
authors.forename: Harald
authors.initials: H
authors.lastname: Stephan
authors.affiliation: Department of Neuroanatomy, Institute for Anatomy, Medical Faculty, University of Duisburg-Essen, Essen, Germany.
authors.forename: Nicole
authors.initials: N
authors.lastname: Dünker
mesh_terms: D000328:Adult; D017209:Apoptosis / Q000187:drug effects*; D053477:Apoptotic Protease-Activating Factor 1 / Q000378:metabolism; D055415:Bone Morphogenetic Protein 4 / Q000494:pharmacology*; D020169:Caspases / Q000378:metabolism; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D004357:Drug Synergism; D006801:Humans; D018168:Receptors, Retinoic Acid / Q000378:metabolism; D012175:Retinoblastoma / Q000473:pathology*; D047488:Retinoid X Receptors / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D014212:Tretinoin / Q000494:pharmacology*; D015854:Up-Regulation / Q000187:drug effects
chemical_list: C506592:APAF1 protein, human; D053477:Apoptotic Protease-Activating Factor 1; D055415:Bone Morphogenetic Protein 4; D018168:Receptors, Retinoic Acid; D047488:Retinoid X Receptors; D014212:Tretinoin; D020169:Caspases