Gene expression profiles of folate deficient colon cancer cells

Abstract

Folate is a B vitamin that inversely modulates colorectal carcinogenesis. Folate status is also an important determinant in chemotherapeutic response. Mediating the transfer of onecarbon moieties is the sole biochemical function known for folate, and in this role folate plays a critical role in DNA synthesis, repair and methylation This study determined the gene expression profiles induced by tolate deficiency in 2 human colon adenocarcinoma cell lines, HCT116 and Caco2. Cells were grown in either standard (2.3 ~tM Mate) or folate deficient (0 ~M) RPMI medium for 20 days. Folate-deficient HCTll6 and Caco2 cells showed sigmficantly reduced growth rates and had sigmficantly decreased (by 80-90%) intracellular folate concentrations compared with corresponding folate-sufficient ceils (P<O.001 ). The deoxyuridine suppression test confirmed functionally significant intracellular folate depletion in folate-deficlent cells (P<0.01). Total RNA from folate-deficient and sufficient ceils of each cell line was hybridized onto 2 commercially available human cancer pathway (a panel of key genes involved in 6 biological pathways frequently altered during transformation and tumongenesis) and apoptosis (a panel of key genes involved in apoptosis) cDNA arrays and differentially expressed genes were identified RT-PCR analysis was used to confirm the results of cDNA array. A total of 13 and 22 cancer pathway genes were differential expressed in folate-defictent HCT116 and Caco2 cells, respectively, compared with corresponding folate-sufficient cells; 4 genes were differentially expressed in both folatedeficient ceils Most notably affected changes were upregulated ATM and downregulated MDM2 in folate-deficient Caco2 cells, upregulated p21 in folate-deficient HCT 116 cells and upregulated b-catenin and VEGF in both folate-deficient ceils. A total of 5 and 12 apoptosis genes were difterentially expressed in folate-deficient HCT 116 and Caco2 cells, respectively, compared with corresponding folate-sufficient cells; 1 gene was differentially expressed in both fofate-deficient cells. Most significantly altered changes were downregulated MDM2 and BAX in folate-deficient Caco2 cells and upregulated B1RC3 in both folate-deficient HCT116 and Caco2 cells. These data suggest that folate deficiency affects the expression of key genes that are related to cell cycle control, DNA damage and repair, apoptosis, signal transduction and angiogenesis in colon cancer cells in a cell-specific manner.