Skeletal alkaline phosphatase specific activity is an index of the osteoblastic phenotype in subpopulations of the human osteosarcoma cell line SaOS-2.
During continuous culture with serial passage, the human osteosarcoma cell line SaOS-2 showed a time-dependent decrease in skeletal alkaline phosphatase (ALP) activity. Because this was indicative of heterogeneity, subpopulations of SaOS-2 cells were isolated from replicate low-density cultures. The subpopulations were less heterogeneous and more stable (with respect to ALP) than the parent population. ALP specific activity in the subpopulations ranged from 0.05 to 2.3 U/mg protein, and cytochemical analyses indicated multiple steady-state levels of ALP activity per cell. The amount of ALP activity in SaOS-2 subpopulations was proportional to collagen production ([3H]proline incorporation into collagenase-digestible protein; r = .84, P less than .005), and to parathyroid hormone (PTH)-linked synthesis of cyclic adenosine monophosphate (cAMP) (r = .88, P less than .01). From these data, we inferred that ALP activity in SaOS-2 cells can provide a useful index of the osteoblastic phenotype, and that ALP activity, collagen production, and PTH-linked adenylate cyclase were coordinately regulated in these osteoblast-like osteosarcoma cells (ie, selection of subpopulations for ALP activity coselected for collagen synthesis and PTH-linked synthesis of cAMP). Further comparative studies showed that micromolar fluoride concentrations stimulated cell proliferation ([3H]thymidine incorporation into DNA) in low-ALP SaOS-2 subpopulations, but not in high-ALP cells (P less than .001), and that this differential sensitivity to fluoride was associated with an inverse correlation between fluoride-sensitive acid phosphatase and ALP activities (r = -.91, P less than .001).
Farley
J R
JR
Department of Medicine, Loma Linda University, CA.
Hall
S L
SL
Herring
S
S
Tarbaux
N M
NM
Matsuyama
T
T
Wergedal
J E
JE
D000469:Alkaline Phosphatase / Q000378:metabolism*; D001842:Bone and Bones / Q000201:enzymology*; D000242:Cyclic AMP / Q000096:biosynthesis; D005459:Fluorides / Q000494:pharmacology; D006651:Histocytochemistry; D006801:Humans; D003012:Microbial Collagenase; D010006:Osteoblasts / Q000502:physiology*; D012516:Osteosarcoma / Q000235:genetics / Q000473:pathology*; D010281:Parathyroid Hormone / Q000494:pharmacology; D010641:Phenotype; D014176:Protein Biosynthesis; D013936:Thymidine / Q000493:pharmacokinetics; D014407:Tumor Cells, Cultured
D010281:Parathyroid Hormone; D000242:Cyclic AMP; D000469:Alkaline Phosphatase; D003012:Microbial Collagenase; D005459:Fluorides; D013936:Thymidine