Antiproliferative effect of calcitriol on human prostatic cancer cell lines: unrelated to the expression of major histocompatibility complex antigens or intercellular adhesion molecule-1 (ICAM-1).

Abstract

In addition to its role in calcium and phosphorus metabolism, calcitriol (1,25-dihydroxyvitamin D3; 1,25-D3) demonstrates multiple effects on cell proliferation/differentiation by expressing major histocompatibility complex (MHC) antigens and intercellular adhesion molecule-1 (ICAM-1). It has recently been reported that 1,25-D3 inhibits the growth of prostatic cancer (PCa) cells. In this study we examined the effect of 1,25-D3 on both the growth and expression of HLA-ABC, HLA-DR and ICAM-1 antigens in PCa cells. Four human PCa cell lines (PC-3, PPC-1, ALVA-41 and ALVA-101) were examined. The cell numbers were enumerated, and the effects of interferon-y (IFN-gamma) and 1,25-D3 on the expression of HLA-ABC, HLA-DR and ICAM-1 were quantitated by flow cytometry. A dose-dependent antiproliferative effect of 1,25-D3 was found in all PCa cells lines except ALVA-41.1,25-D3 was approximately 10 times as potent as its analogue 24,25-dihydroxyvitamin D3 in inhibiting the growth of PC-3 cells. Also, the relative inhibitory ability of these compounds paralleled the strength of their binding affinities for the 1,25-D3 receptor, indicating that the antiproliferative effect may require a receptor-ligand interaction. HLA-ABC was expressed in PC-3, ALVA-41 and ALVA-101, but not in PPC-1 cells, while HLA-DR was not expressed on any of the tested cells. IFN-gammacould enhance or induce HLA-ABC but not HLA-DR expression in the tested cells. ICAM-1 was expressed in all cells and slightly upregulated by IFN-gamma. In this study 1,25-D3 had an antiproliferative effect on 3 of the 4 examined PCa cell lines.