British Journal of Nutrition

Full Papers

High folic acid increases cell turnover and lowers differentiation and iron content in human HT29 colon cancer cells

Linette Pellisa1, Yvonne Dommelsa1, Dini Venemaa1, Ab van Polanena1, Esther Lipsa1, Hakan Baykusa1, Frans Koka2, Ellen Kampmana2 and Jaap Keijera1 c1

a1 RIKILT-Institute of Food Safety, PO Box 230, 6700 AE Wageningen, The Netherlands

a2 Wageningen University, Division of Human Nutrition, Wageningen, The Netherlands

Abstract

Folate, a water-soluble B vitamin, is a cofactor in one-carbon metabolism and is essential for DNA synthesis, amino acid interconversion, methylation and, consequently, normal cell growth. In animals with existing pre-neoplastic and neoplastic lesions, folic acid supplementation increases the tumour burden. To identify processes that are affected by increased folic acid levels, we compared HT29 human colon cancer cells exposed to a chronic supplemental (100 ng/ml) level of folic acid to cells exposed to a normal (10 ng/ml) level of folic acid, in the presence of vitamin B12 and other micronutrients involved in the folate–methionine cycle. In addition to higher intracellular folate levels, HT29 cells at 100 ng folic acid/ml displayed faster growth and higher metabolic activity. cDNA microarray analysis indicated an effect on cell turnover and Fe metabolism. We fully confirmed these effects at the physiological level. At 100 ng/ml, cell assays showed higher proliferation and apoptosis, while gene expression analysis and a lower E-cadherin protein expression indicated decreased differentiation. These results are in agreement with the promoting effect of folic acid supplementation on established colorectal neoplasms. The lower expression of genes related to Fe metabolism at 100 ng folic acid/ml was confirmed by lower intracellular Fe levels in the cells exposed to folic acid at 100 ng/ml. This suggests an effect of folate on Fe metabolism.

(Received February 21 2007)

(Revised July 04 2007)

(Accepted July 30 2007)

Correspondence:

c1 Corresponding author: Dr J. Keijer, fax +31 317 417717, email jaap.keijer@wur.nl

Footnotes

Abbreviations: DMEM, Dulbecco's modified Eagle's medium; MTT, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide; SAH, S-adenosyl homocysteine; SAM, S-adenosyl methionine

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