Regulation ofC-FOS and ornithine decarboxylase mRNA levels by estrogen and 5-azacytidine

Lipotropes regulate bcl-2 gene expression in the human breast cancer cell line, MCF-7

Lipotropes, a methyl group containing nutrients, including choline, methionine, folic acid, and vitamin B(12), are essential nutrients for humans. They are important methyl donors that interact in the metabolism of one-carbon units and are essential for the synthesis and methylation of deoxyribonucleic acid. The purpose of this study was to examine the effects of excess lipotropes on the growth of a human breast cancer cell line, MCF-7, and normal mammary cells, MCF-10A, in culture. Both cell lines were grown in basal culture medium for 24 h and then switched to medium supplemented with 50 times the amount of each lipotrope as basal culture medium (control). Although there were no significant differences in growth between treatments in either cell line, gene array and Northern analysis revealed that expression of bcl-2 was decreased in lipotrope-treated MCF-7 cells. The ability to induce tumor cell death could have many uses in the prevention and treatment of cancer. Bcl-2 regulates apoptosis and has been shown to directly affect the sensitivity of cancer cells to chemotherapy agents, and it is suggested that strategies designed to block Bcl-2 might prove useful in sensitizing tumor cells to chemotherapy-induced apoptosis. This study shows that although excess lipotropes do not inhibit the growth of breast cancer cells, they can down-regulate the bcl-2 gene, suggesting that lipotropes may increase the susceptibility of breast cancer cells to anticancer drugs.

Modulation of expression of fos and Ha-ras oncogenes and ornithine decarboxylase activity in mammary gland and liver of young female rats by the absence of dietary lipotropes

There is evidence that diets deficient in lipotropes [methionine, choline, pteroylmonoglutamic acid (folic acid), and cyanocobalamin (vitamin B12)] induce and enhance hepatocarcinogenesis. This research examined the extent to which dietary lipotropes modify cellular oncogene expression and ornithine decarboxylase activity in mammary gland and liver of rats. Eighteen female Sprague-Dawley rats (8 wk old) were fed 3 wk on one of three diets: 1) a control synthetic diet; 2) a methyl-deficient diet lacking choline, methionine, pteroylmonoglutamic acid, and cyanocobalamin; or 3) a diet supplemented with twice the amount of each lipotrope as in the control synthetic diet. The group fed the methyl-deficient diet gained less body weight than groups fed the control or methyl-supplemented diet. The group fed the methyl-deficient diet had approximately 5- and 11-fold greater fos transcription in mammary gland and liver, respectively, than did the control group. The expression of the Ha-ras gene in mammary gland and liver of the group fed the methyl-deficient diet was increased by 4- and 6-fold compared with that of the control. Ornithine decarboxylase activity, considered to be a developmental marker, was higher in liver and mammary gland of the group fed the methyl-deficient diet than in either the group fed control synthetic diet or the group fed the methyl-supplemented diet. The methyl-deficient diet may have caused activation of the transcription factor fos and thus the activation of the transcription regulatory complex, AP-1. In turn, AP-1 may regulate genes, such as ornithine decarboxylase, which are responsible for cell proliferation and differentiation.

Lipotrope-modified diets enhance nitrosomethylurea-induced mammary carcinogenesis in female rats

This study was conducted to determine the effects of lipotrope-modified (deficient or supplemented) diets on nitrosomethylurea- (NMU) induced mammary tumorigenesis. Eighty female Sprague-Dawley rats (4 wks old) were assigned to one of the following groups: control-synthetic diet (CSD), containing all required lipotropes; choline-methionine-deficient diet (CMD); methyl-deficient diet (MDD), lacking all lipotropes; and methyl-supplemented diet (MSD), containing twice as much of each lipotrope as the CSD diet. All animals were injected with NMU after a three-week dietary treatment period. MDD and MSD groups had shorter tumor latency periods (73 and 74 days, respectively) than the CSD group (105 days). Number of tumors per rat was significantly increased in the MDD group (4.6) compared with CSD (1.6), CMD (2.1), and MSD (2.5) groups. The results indicate that dietary manipulation of lipotropes in young female rats enhanced NMU-induced mammary tumorigenesis.