Characterization of a human osteoblastic osteosarcoma cell line (SAOS-2) with high bone alkaline phosphatase activity.
We characterized the alkaline phosphatase activity of the human osteogenic sarcoma cell line, SAOS-2, and studied the regulation of this enzyme and 3',5'-cyclic adenosine monophosphate levels by 1,25-dihydroxyvitamin D3 and triamcinolone acetonide. We report that the basal alkaline phosphatase activity of SAOS-2 cells was 100-1000 times greater than that of other established human osteogenic sarcoma cell lines. The enzymatic activity was thermolabile, could be inhibited by levamisole and L-homoarginine, but not by L-phenylalanine, and was immunoprecipitable with anti-bone/liver/kidney, but not with anti-placental antibody, confirming that it is the tissue-unspecific or bone/liver/kidney isoenzyme. However, in contrast to other established human osteosarcoma cell lines (TE-85, SAOS-1), in which alkaline phosphatase activity is stimulated several-fold by the steroid hormones 1,25-dihydroxyvitamin D3 and hydrocortisone, the alkaline phosphatase activity of SAOS-2 cells was not affected by 1,25-dihydroxyvitamin D3 treatment despite the presence of classical receptors for this hormone. Furthermore, administration of the potent glucocorticoid analogue, triamcinolone acetonide, induced only a modest increase in activity. The SAOS-2 cell line expressed low basal cAMP levels (28 pmol/10(6) cells) which could be increased 25-40 times by pretreatment with parathyroid hormone. However, unlike other osteoblastic models, in which PTH-induced cAMP stimulation is modulated by 1,25-dihydroxyvitamin D3 and glucocorticoids, neither of these hormones had an effect on the PTH-stimulated cAMP levels in SAOS-2 cells. We conclude that the SAOS-2 cell line is an osteoblastic cell model which expresses high levels of tissue-unspecific alkaline phosphatase activity and exhibits limited responsiveness to two steroid hormones.(ABSTRACT TRUNCATED AT 250 WORDS)
Murray
E
E
Department of Medicine, Endocrine Section, University of California, La Jolla.
Provvedini
D
D
Curran
D
D
Catherwood
B
B
Sussman
H
H
Manolagas
S
S
D000469:Alkaline Phosphatase / Q000032:analysis*; D001842:Bone and Bones / Q000201:enzymology*; D002117:Calcitriol / Q000494:pharmacology; D002460:Cell Line; D000242:Cyclic AMP / Q000096:biosynthesis; D006801:Humans; D010006:Osteoblasts / Q000473:pathology*; D012516:Osteosarcoma / Q000473:pathology*; D014222:Triamcinolone Acetonide / Q000494:pharmacology
D000242:Cyclic AMP; D000469:Alkaline Phosphatase; D014222:Triamcinolone Acetonide; D002117:Calcitriol