1-ALPHA,25-DIHYDROXYVITAMIN D3 AND ALL-TRANS-RETINOIC ACID INHIBIT THE GROWTH OF A LUNG-CANCER CELL-LINE

The secosteroid 1 alpha, 25-dihydroxyvitamin D3 (calcitriol) and retin oic acid are the major biologically active metabolites of vitamins D a nd A, respectively. Their antitumor activity has been observed in seve ral cancer cells in vitro apart from lung cancer cells. The purpose of this study was to examine the possible effects of the agents on lung cancer cell lines. The responses of five lung cancer cell lines to cal citriol or all-trans-retinoic acid (RA) were assessed by a colorimetri c MTT assay. Calcitriol inhibited growth in one of the tested cell lin es, i.e. EBC-1 squamous cell carcinoma, dose dependently. RA also exhi bited the same effect in EBC-1 cells. However neither agent affected t he grouth of other lung cancer cell lines. Subsequently we examined th e mRNA expression of vitamin D receptor (VDR) and retinoic acid recept or (RAR alpha) in these lung cancer cells by quantitative RT-PCR. EBC- 1 cells expressed high levels of mRNA far both VDR and RAR alpha, whil e other cell lines expressed much lower mRNA levels for the receptors. These data suggest that the growth inhibitory effects of the vitamins are associated with mRNA expression for VDR and RAR alpha.