title: Thymosin beta 4 is expressed in ROS 17/2.8 osteosarcoma cells in a regulated manner.
abstract: The differential expression of mRNAs between the closely related rat osteosarcoma cell lines ROS 17/2.8 and ROS 25/1 was used to identify genes whose expression is associated with the osteoblast phenotype. Thymosin beta 4 cDNA was cloned from an ROS 17/2.8 complimentary DAN library on the basis of its differential hybridization with radiolabeled cDNA prepared from ROS 17/2.8 and ROS 25/1 cells. Northern blot analysis confirmed that thymosin beta 4, hitherto a putative immunodulatory hormone, was indeed differentially expressed. Steady state mRNA levels were severalfold higher in ROS 17/2.8 cells exhibiting an osteoblast-like phenotype, compared with the less osteoblast-like ROS 25/1. Thymosin beta 4 transcripts were also detected in rat UMR 106 osteosarcoma cells and in intact neonatal and fetal rat calvaria. Sequence analysis of the cDNA indicated that thymosin beta 4 transcripts may arise by processing at a more distal polyadenylation signal. Treatment of ROS 17/2.8 cells with dexamethasone increased, while addition of 1,25-dihydroxyvitamin D3 decreased thymosin beta 4 mRNA. The phenotype-dependent expression in the ROS cells and the response to steroid hormone suggest that thymosin beta 4 expression contributes to the osteoblast phenotype.
authors.affiliation: Endocrine Unit, Massachusetts General Hospital, Boston.
authors.forename: M J
authors.initials: MJ
authors.lastname: Atkinson
authors.forename: M W
authors.initials: MW
authors.lastname: Freeman
authors.forename: H M
authors.initials: HM
authors.lastname: Kronenberg
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001859:Bone Neoplasms / Q000235:genetics* / Q000378:metabolism; D002117:Calcitriol / Q000494:pharmacology; D004247:DNA / Q000096:biosynthesis; D003907:Dexamethasone / Q000494:pharmacology; D015536:Down-Regulation / Q000187:drug effects; D008969:Molecular Sequence Data; D012516:Osteosarcoma / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D013947:Thymosin / Q000031:analogs & derivatives* / Q000096:biosynthesis / Q000235:genetics; D014407:Tumor Cells, Cultured; D015854:Up-Regulation / Q000187:drug effects; D000099201:Thymosin beta(4)
chemical_list: D002117:Calcitriol; D004247:DNA; D003907:Dexamethasone; D012333:RNA, Messenger; D013947:Thymosin; D000099201:Thymosin beta(4)