Effects of IFN-beta and 1,25-dihydroxyvitamin D3 on cellular proliferation, induction of 2',5'-oligoadenylate (2-5A) synthetase and changes in immunoreactive pRB/p53 in human prostatic JCA-1 cells.
The combined antimitogenic effects of IFN-beta and 1,25-dihydroxyvitamin D3 (vit. D3) were investigated by treating the androgen-independent JCA-1 cells, established from the primary prostatic tumor site prior to anti-hormonal therapy, with IFN-beta (1000 IU/ml), vit. D3 (100 nM), and both agents. Cell growth, changes in overall RNA and protein contents, and cell cycle regulatory proteins pRB/p53 were determined. After a 24 h exposure, a significant reduction in cell proliferation was observed in all three conditions. IFN-beta, vit D3, and their combination elicited, respectively, a 1.7-, 1.6- and 2.5-fold increase in total RNA and a corresponding 1.4-, 1.2- and 1.7-fold increase in soluble proteins. The IFN-inducible 2-5A synthetase activity was elevated by 15-, 1.4- and 21-fold, respectively. No differences in cell cycle phase distribution were found between control and treated samples. However, a significant change in pRB and p53 expression was observed upon exposure to these agents. A progressive increase in total pRB was observed in untreated JCA-1 cells, with the 48 h culture showing a 1.9-fold increase over the 6 h culture. The ratio of phosphorylated to the nonphosphorylated forms of pRB, however, decreased from 3.00 at 6 h to 1.2 at 48 h. The overall pRB increase as well as the modified:unmodified protein ratio change were both markedly decreased when the cells were treated with IFN-beta, vit. D3, or their combination. With p53, a similar progressive increase was also observed in control cells, which was largely abolished by IFN-beta but only partially blocked by vit. D3. The combination of IFN-beta and vit. D3 gave results similar to samples receiving vit. D3 alone suggesting that the effects of IFN-beta, insofar as p53 modulation is concerned, is distal to the effects of vit. D3.
Faiella
L
L
Department of Urology, New York Medical College, Valhalla 10595, USA.
Ng
C
C
Hsieh
T C
TC
Wu
J M
JM
Mallouh
C
C
D015088:2',5'-Oligoadenylate Synthetase / Q000096:biosynthesis*; D015153:Blotting, Western; D002117:Calcitriol / Q000494:pharmacology*; D002455:Cell Division / Q000187:drug effects; D016213:Cyclins / Q000494:pharmacology; D004790:Enzyme Induction / Q000187:drug effects; D006801:Humans; D016899:Interferon-beta / Q000494:pharmacology*; D008297:Male; D011471:Prostatic Neoplasms / Q000201:enzymology* / Q000378:metabolism* / Q000473:pathology; D012313:RNA / Q000096:biosynthesis; D016160:Retinoblastoma Protein / Q000378:metabolism*; D014407:Tumor Cells, Cultured / Q000187:drug effects; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*
D016213:Cyclins; D016160:Retinoblastoma Protein; D016159:Tumor Suppressor Protein p53; D012313:RNA; D016899:Interferon-beta; D015088:2',5'-Oligoadenylate Synthetase; D002117:Calcitriol