EFFECTS OF 1,25-DIHYDROXYVITAMIN D-3 ON TRANSFORMED C3H 10T1/2 FIBROBLASTS GROWN AS MULTICELLULAR SPHEROIDS/

We have previously shown that 1,25-dihydroxyvitamin D-3 (1,25-(OH)(2)D -3) is able to modulate proliferation of C3H/10T1/2 fibroblasts grown in monolayer cell culture. The aim of this study was to investigate th e effects of the hormone in a 3-dimensional culture system, which is c onsidered to better reflect the cellular environment that is found in vivo. Two transformed cell lines of C3H/10T1/2 fibroblasts (C116 and T PA 482) were grown as multicellular spheroids, whereas the nontumorige nic C3H/10T1/2 C18 cells failed to form spheroids. The hormone had no effect on spheroids made of TPA 482 cells but had a biphasic effect on Glib spheroid growth with stimulation at low and inhibition at higher concentrations. In C116 spheroids, 10(-8) M 1,25-(OH)(2)D-3 induced c omplete arrest of spheroid growth. Light and electron microscopic stud ies and immunocytochemistry showed that 10(-8) M 1,25-(OH)(2)D-3 induc ed morphological changes in C116 spheroids, with a marked reduction in expression of fibronectin, laminin and the gap junction protein conne xin 43. These effects were followed by a loosening of the spheroid str ucture, detachment of viable cells, and finally disaggregation of the spheroids. The results of this study, together with the data previousl y obtained in monolayer cell cultures, indicate that the effects of 1, 25-(OH)(2)D-3 may be conditioned by the cellular environment. Therefor e, the spheroid model is an interesting tool for investigation of the antineoplastic effect of the hormone. (C) 1995 Wiley-Liss, Inc.