EFFECTS OF VITAMIN-D AND RETINOIC ACID ON HUMAN GLIOBLASTOMA CELL-LINES

The biological significance of vitamin D receptors expressed by gliobl astoma and other glial tumours is still unclear. In an effort to clari fy this issue we studied the effects of increasing concentrations of 2 5-dihydroxyvitamin D-3 and its metabolite 1 alpha,25-dihydroxyvitamin D-3 on two human glioblastoma cell lines. Both substances were capable of inducing a significant(> 50%) reduction in growth of the two gliob lastoma cell lines at dosages over 5 mu M. When the HU 70 cell line wa s treated by increasing dilutions of 25-dihydroxyvitamin D-3 combined with 1 mu M all trans-retinoic acid, significant inhibition was appare nt even after addition of 25-dihydroxyvitamin D-3 in the nanomolar ran ge. Reduction of growth index was mainly due to induced cell death. Ou r results provide in vitro evidence that vitamin D metabolites alone o r in combination with retinoids may be potentially useful agents in th e differentiation therapy of human malignant gliomas.