title: Retinoic acid modulation of mRNA levels in malignant, nontransformed, and immortalized osteoblasts.
abstract: Clonal cell lines presumably "arrested" at a particular stage of differentiation are useful models to study the processes of differentiation in osteoblasts. UMR-201 is a presumptive preosteoblastic nontransformed rat clonal cell line with a limited life span in culture. Two immortalized cell lines, UMR-201-10A (10A) and UMR-201-10B (10B), were derived from UMR-201 by stable transfection with simian virus (SV) 40 large T antigen. This study compares the growth and profile of gene expression of the immortalized cell lines with those of UMR-201 and UMR-106-06, a rat clonal cell line with well-defined osteoblast-like phenotypic characteristics. All four cell lines constitutively expressed the mRNA for the gamma, alpha, and beta receptors for retinoic acid (RA), the growth hormone receptor, pro-alpha 1(I) collagen, osteonectin, bone proteoglycan I, and bone morphogenetic proteins (BMP) 1 and 2A. Alkaline phosphatase mRNA was absent in the preosteoblast cell lines but was induced by treatment with 10(-6) M RA, which also increased the steady-state levels of mRNA for osteopontin and BMP1. mRNA for matrix gla protein was constitutively present and further induced by RA in UMR-201 and 10B only. Messenger RNA for bone sialoprotein and bone morphogenetic protein 3 were constitutively expressed in UMR-106-06 and UMR-201 but absent in the immortalized cell lines. None of the cell lines expressed measurable mRNA for bone gla protein or bone proteoglycan II. 10B grew more rapidly than UMR-201, but unlike UMR-201, it was also able to proliferate in serum-free medium and exhibit anchorage-independent growth. In summary, this study identifies novel retinoic acid effects on gene expression in these cells. Differences noted in the expression of mRNAs between UMR-106-06 and the other cell lines may provide some insight into the sequence of expression of these phenotypic characteristics as osteoblasts differentiate.
authors.affiliation: Department of Medicine, University of Melbourne, Australia.
authors.forename: H
authors.initials: H
authors.lastname: Zhou
authors.forename: R G
authors.initials: RG
authors.lastname: Hammonds
authors.forename: D M
authors.initials: DM
authors.lastname: Findlay
authors.forename: P J
authors.initials: PJ
authors.lastname: Fuller
authors.forename: T J
authors.initials: TJ
authors.lastname: Martin
authors.forename: K W
authors.initials: KW
authors.lastname: Ng
mesh_terms: D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D002135:Calcium-Binding Proteins / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism; D002454:Cell Differentiation; D002460:Cell Line; D002461:Cell Line, Transformed; D016326:Extracellular Matrix Proteins; D010006:Osteoblasts / Q000187:drug effects* / Q000378:metabolism; D053495:Osteopontin; D012516:Osteosarcoma / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism*; D018168:Receptors, Retinoic Acid; D012795:Sialoglycoproteins / Q000378:metabolism; D014212:Tretinoin / Q000494:pharmacology*; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000378:metabolism; D000097568:Matrix Gla Protein
chemical_list: D000469:Alkaline Phosphatase; D002135:Calcium-Binding Proteins; D002352:Carrier Proteins; D016326:Extracellular Matrix Proteins; D053495:Osteopontin; D012333:RNA, Messenger; D018168:Receptors, Retinoic Acid; D012795:Sialoglycoproteins; D014212:Tretinoin; D000097568:Matrix Gla Protein; C506897:Spp1 protein, rat