Abstract #7: Characterization of a normal human colonic epithelial cell line as a model to study vitamin D action in colon cancer prevention.
Authors: Elisabete Figueiredo, Rajendra Mehta, Xinjian Peng, Rajeshwari Mehta, Genoveva Murillo
Journal: Cancer Research (2009)

AACR Annual Meeting-- Apr 18-22, 2009; Denver, CO

The protective role of vitamin D against colon cancer has been reported and it supports its use in prevention and treatment. The active vitamin D metabolite, 1\#945;, 25 dihydroxyvitamin D3 (1\#945;,25(OH)2D3) mediates growth inhibitory signaling via interaction with its vitamin D receptor (VDR). The VDR-ligand complex in the nucleus mediates its action by regulating the transcription of the VDR target genes. Cells that express VDR respond to 1,25(OH)2D3 by decreasing proliferation and enhancing differentiation. The disruption of the vitamin D signaling pathway suggested to be an early event in the tumorigenesis process could represent a strategy by which cancer cells evade negative growth regulation. While VDR and CYP27b1 expression is abundant in normal and neoplastic colon tissue samples, it is almost non-existent in metastases. However little is known about the function of vitamin D on normal colonic epithelial cells. In the current study we used the NCM356 normal human colon mucosal epithelial cells to better characterize the role of vitamin D in normal colonocytes. Studies were conducted to determine whether VDR was detectable in NCM356 and basal VDR protein levels were compared to those of colon cancer cell lines (Caco-2 and HT29). We found that VDR is expressed in both normal and neoplastic colonic epithelial cells. The NCM356 cells consist of a mixed monolayer/suspension culture and since it has been reported that two sub-populations of SW480 colon cancer cell line have different levels of VDR expression, we evaluated VDR protein levels between the two sub-populations of NCM356. Although no significant difference in basal levels of VDR between NCM356 sub-populations was observed, the floating cells appear to be more responsive to 1\#945;, 25(OH)2D3. The effects of 1\#945;, 25(OH)2 D3 were examined on cell proliferation and the expression of several key proteins and genes via western blot or RT-PCR. The anti-proliferative effects mediated by 1\#945;,25(OH)2D3 were observed at 1nM for the floating cells, whereas for the adherent sub-population the growth inhibition was not observed until 100 nM. The differential response to 1\#945;, 25(OH)2D3 of the sub-populations was correlated with protein or mRNA levels of possible regulatory molecules (VDR, CYP24, CYP27b1, p27 and p21). Although there was an up-regulation for VDR and p27 in the floating cells, no significant difference was observed for the adherent sub-population of NCM356 treated with 1\#945;, 25(OH)2D3. CYP24, an endogenous VDR target gene, was induced in both floating (9-fold) and adherent (6-fold) sub-populations of NCM356. These results suggest that NCM356, a normal human colonic cell line is a good model to study chemoprevention of colon carcinogenesis by Vitamin D. (Supported by the Business Development Agency- aicep Global Portugal [Agencia Para O Investimento e Comercio Externo de Portugal], NIH Grants K01 CA103861 and R01 CA121157).

Citation Information: In: Proc Am Assoc Cancer Res; 2009 Apr 18-22; Denver, CO. Philadelphia (PA): AACR; 2009. Abstract nr 7.