1,25-Dihydroxyvitamin D3 induces programmed cell death in a rat glioma cell line

Abstract

1,25‐Dihydroxyvitamin D3 (1,25(OH)2D3), a seco‐steroid hormone with potential antitumoral activities, has been recently reported to exert cytotoxic effects on C6 glioma cells. However, the molecular mechanisms which trigger this cell death remain unknown. We show here that this 1,25(OH)2D3‐induced cell death is dependent upon protein synthesis and is accompanied by the expression of c‐myc, p53, and gadd45 genes. Two other genes, coding for interleukin‐6 and vaso‐endothelial growth factor, are also up‐regulated after addition of 1,25(OH)2D3. This programmed cell death can be suppressed when cells are treated with forskolin, a drug which increases intracellular cAMP concentration, or with genistein, an inhibitor of tyrosine protein kinases. However, in spite of the demonstration of fragmented DNA in 1,25(OH)2D3‐treated cells, the C6.9 cells used in this study do not show the classical morphological features of apoptosis. These results provide the first evidence for the existence of a programmed cell death triggered by 1,25(OH)2D3 in glioma cells and may provide a basis for the development of new therapeutic strategies. In addition, these data also suggest that the treatment of C6.9 cells with 1,25(OH)2D3 may be a useful model to study the molecular mechanisms involved in the programmed cell death of a cell of glial origin. © 1996 Wiley‐Liss, Inc.

Differentially expressed genes in C6.9 glioma cells during vitamin D-induced cell death program

“…The screening of this library was performed with two complex 32 P-labeled cDNAs probes prepared from Poly(A) + RNA isolated from C6.9 cells 3 days after a treatment of 24 h with either 1,25-D3 or its vehicle. This time point was chosen to allow the detection of changes in RNA expression occurring well before the death of cells, which takes place around day 6 (Baudet et al, 1996a), and because a peak in the expression of c-myc, p53, gadd45, IL-6 and VEGF in 1,25-D3-treated C6.9 cells has been recently reported to occur at day 3 (Baudet et al, 1996b).…”

“…Therefore, the consequence of the down-regulation of ON/SPARC observed here would be to increase cell responsiveness to cytokines. This suggests that the decreased expression of ON/SPARC could be, together with the induction of VEGF and IL-6 expressions (Baudet et al, 1996b), a part of the mechanisms observed under stressful conditions to enhance cell viability.…”

“…Therefore, C6 cells were subcloned and a subclone, referred to as C6.9, was selected on the basis of its high susceptibility to the cytotoxic action of 1,25-D3 (Baudet et al, 1996a). In C6.9 cells, 1,25-D3 treatment induces accumulation of mRNAs of c-myc, p53 and gadd45 genes (Baudet et al, 1996b). Furthermore, cells are largely protected against the toxic action of 1,25-D3 if they are treated with cycloheximide (Baudet et al, 1996b).…”

“…In C6.9 cells, 1,25-D3 treatment induces accumulation of mRNAs of c-myc, p53 and gadd45 genes (Baudet et al, 1996b). Furthermore, cells are largely protected against the toxic action of 1,25-D3 if they are treated with cycloheximide (Baudet et al, 1996b). These data indicate that 1,25-D3 cytotoxicity corresponds to a cell death program, that requires protein synthesis.…”

22‐Oxa‐1,25‐dihydroxyvitamin D3 efficiently inhibits tumor growth in inoculated mice and primary histoculutre of cholangiocarcinoma

“…Decreased expression of the antiapoptotic protein Bcl-2, increased expression of proapoptotic protein Bax, and release of cytochrome c from the mitochondria may underlie the action of vitamin D. 37,38 A key regulator of apoptotic cell death, p53, also is up-regulated after vitamin D treatment. 39,40 In addition, vitamin D inhibits the expression of telomerase, an enzyme that adds a specific DNA sequence repeat to the 3 0 end of DNA strands, resulting in cell death. 41,42 In the current investigation, we noted that supplementation with 22-oxa-D 3 also up-regulated the expression of VDR, a receptor that is necessary for the genomic action of vitamin D. This observation is was evident in cell cultures, in the mouse model, and in the HDRA.…”