RESUMO
Recently, 1,25-dihydroxyvitamin D3 (1,25-D3) and less hypercalcemic analogs were shown to exert a delayed cytotoxic effect on rat C6 glioma cells. 1,25-D3 induces in these cells a programmed cell death, accompanied by the induction of c-myc, p53 and gadd 45 genes. The involvement of the intracellular vitamin D receptor (VDR) remained to be determined. In this lethal process, we have investigated its role in a subclone of C6 cells, which was isolated on the basis of its resistance to 1,25-D3, and in which VDR expression was not detected either at the mRNA or protein levels. The stable transfection of a rat VDR cDNA into this clone restored its susceptibility to the cytotoxic effects of 1,25-D3. This phenomenon was accompanied by a dramatic upregulation of c-myc mRNA expression, as already described in a C6-sensitive clone. These results provide the first evidence that VDR expression, if not sufficient, is necessary to mediate 1,25-D3 cytotoxic effect in C6 glioma cells. Since VDR mRNA expression has been already reported in human brain tumors, our data imply that the identification of VDR expression could become a prerequisite in any strategy of glioma treatment with vitamin D analogs.
Assuntos
Calcitriol/toxicidade , Glioma/genética , Receptores de Calcitriol/genética , Transfecção/efeitos dos fármacos , Animais , Morte Celular/efeitos dos fármacos , Morte Celular/genética , Células Clonais , Fragmentação do DNA/efeitos dos fármacos , DNA Complementar/genética , Resistencia a Medicamentos Antineoplásicos , Genes myc/efeitos dos fármacos , Glioma/patologia , Ratos , Receptores de Calcitriol/biossínteseRESUMO
C6.9 rat glioma cells undergo a cell death program when exposed to 1, 25-dihydroxyvitamin D3 (1,25-D3). As a global analytical approach, we have investigated gene expression in C6.9 engaged in this cell death program using differential screening of a rat brain cDNA library with probes derived from control and 1,25-D3-treated cells. Using this methodology we report the isolation of 61 differentially expressed cDNAs. Forty-seven cDNAs correspond to genes already characterized in rat cells or tissues. Seven cDNAs are homologous to yeast, mouse or human genes and seven are not related to known genes. Some of the characterized genes have been reported to be differentially expressed following induction of programmed cell death. These include PMP22/gas3, MGP and beta-tubulin. For the first time, we also show a cell death program induced up-regulation of the c-myc associated primary response gene CRP, and of the proteasome RN3 subunit and TCTP/mortalin genes. Another interesting feature of this 1,25-D3 induced-cell death program is the down-regulated expression of transcripts for the microtubule motor dynein heavy chain/MAP 1C and of the calcium-binding S100beta protein. Finally 15 upregulated cDNAs encode ribosomal proteins suggesting a possible involvement of the translational apparatus in this cell program. Alternatively, these ribosomal protein genes could be up-regulated in response to altered rates of cellular metabolism, as has been demonstrated for most of the other isolated genes which encode proteins involved in metabolic pathways. Thus, this study presents to our knowledge the first characterization of genes which are differentially expressed during a cell death program induced by 1, 25-D3. Therefore, this data provides new information on the fundamental mechanisms which participate in the antineoplastic effects of 1,25-D3 and on the machinery of a cell death program in a glioma cell line.
Assuntos
Apoptose/efeitos dos fármacos , Biomarcadores Tumorais , Calcitriol/farmacologia , Agonistas dos Canais de Cálcio/farmacologia , Proteínas da Matriz Extracelular , Glioma , Vitamina D/farmacologia , Animais , Apoptose/fisiologia , Osso e Ossos/fisiologia , Proteínas de Ligação ao Cálcio/genética , Diferenciação Celular/efeitos dos fármacos , Diferenciação Celular/fisiologia , Cisteína , Cisteína Endopeptidases/genética , DNA/análise , DNA Complementar , Dineínas/genética , Regulação Neoplásica da Expressão Gênica/efeitos dos fármacos , Biblioteca Gênica , Proteínas de Choque Térmico HSP70/genética , Complexos Multienzimáticos/genética , Proteínas da Mielina/genética , Proteínas de Neoplasias/genética , Osteonectina/genética , Complexo de Endopeptidases do Proteassoma , Biossíntese de Proteínas/fisiologia , RNA Mensageiro/análise , Ratos , Proteínas Ribossômicas/genética , Tubulina (Proteína)/genética , Células Tumorais Cultivadas/química , Células Tumorais Cultivadas/citologia , Células Tumorais Cultivadas/fisiologia , Proteína Tumoral 1 Controlada por Tradução , Proteína de Matriz GlaRESUMO
Retinoic acid (RA), the acid form of vitamin A, is shown to enhance the synthesis of nerve growth factor (NGF) in cultures of mouse L cells. Maximal stimulation was observed in cells growing in a serum-free medium supplemented with 10(-6)M RA during 48 h. The drug increased both the level of NGF mRNA and the amount of mature NGF protein secreted by the cells. RA was previously reported to increase the number of NGF receptors on some neuroblastoma cells (Haskell et al., 1987 Cell and Tiss. Res., 247, 67-73). It seems, therefore, that RA may influence nerve cell differentiation by promoting both the synthesis of the neurotrophic factor and the responsiveness of target cells.