Basic fibroblast growth factor autocrine loop controls human osteosarcoma phenotyping and differentiation.
BACKGROUND
We focused on the phenotype of non-mineralizing MG 63 and mineralizing TE 85 human osteosarcoma cells and investigated the role of bFGF in modulating their differentiative responses. Basic FGF expression and bFGF effects on osteocalcin, runt-related transcription factor-2 (RUNX2), matrix molecular production and bFGF receptors, were evaluated.


METHODS
Osteocalcin and RUNX2 gene expression were studied by RT-PCR analysis. We evaluated cell proliferation by DNA content and performed differentiation studies on glycosaminoglican (GAG), collagen and proteoglican (PG) synthesis by using radiolabelled precursors and Northern blotting. BFGF receptors were quantified by bFGF receptor binding assay.


RESULTS
Osteocalcin is expressed in MG63 and TE65. RUNX2 RNA is differentially spliced in the two cell lines. BFGF elicits the effects of differentially splicing RUNX2. Proliferation, GAG synthesis, bFGF and proteoglycan mRNA expression, high and low affinity bFGF receptors, were more marked in MG 63 and differently affected by bFGF. Procollagen expression and alkaline phosphatase activity were significantly reduced. BFGF increased TE 85 cell proliferation and reduced TE 85 procollagen and osteocalcin production.


CONCLUSIONS
The different splice variants in RUNX2 gene in the two cell lines might be related to their different phenotypes. The less differentiated stage of MG63 could also be related to bFGF over-production and more bFGF receptors. The consequent increase in bFGF-bFGF receptor binding could explain the bFGF differentiative effects on MG 63. We suggest an autocrine role of bFGF endogenous release in controlling the different osteosarcoma phenotypes.
Bodo
Maria
M
Sezione di Istologia, Facoltà di Medicina, Università di Perugia. bodo@unipg.it
Lilli
Cinzia
C
Bellucci
Catia
C
Carinci
Paolo
P
Calvitti
Mario
M
Pezzetti
Furio
F
Stabellini
Giordano
G
Bellocchio
Silvia
S
Balducci
Chiara
C
Carinci
Francesco
F
Baroni
Tiziano
T
D000469:Alkaline Phosphatase / Q000235:genetics / Q000378:metabolism; D019898:Autocrine Communication / Q000187:drug effects; D001859:Bone Neoplasms / Q000378:metabolism* / Q000473:pathology; D002454:Cell Differentiation / Q000187:drug effects; D002455:Cell Division; D002460:Cell Line; D024042:Collagen Type I / Q000235:genetics / Q000378:metabolism; D050659:Core Binding Factor Alpha 1 Subunit; D005109:Extracellular Matrix / Q000378:metabolism; D016222:Fibroblast Growth Factor 2 / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology*; D005786:Gene Expression Regulation / Q000187:drug effects; D006025:Glycosaminoglycans / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D006801:Humans; D009363:Neoplasm Proteins; D015675:Osteocalcin / Q000235:genetics / Q000378:metabolism; D012516:Osteosarcoma / Q000378:metabolism* / Q000473:pathology; D010641:Phenotype; D011485:Protein Binding; D011509:Proteoglycans / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D017468:Receptors, Fibroblast Growth Factor / Q000032:analysis / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014407:Tumor Cells, Cultured
D024042:Collagen Type I; D050659:Core Binding Factor Alpha 1 Subunit; D006025:Glycosaminoglycans; D009363:Neoplasm Proteins; D011509:Proteoglycans; D012333:RNA, Messenger; D017468:Receptors, Fibroblast Growth Factor; D014157:Transcription Factors; D016222:Fibroblast Growth Factor 2; D015675:Osteocalcin; D000469:Alkaline Phosphatase