Long-term Epigenetic Therapy with Oral Zebularine Has Minimal Side Effects and Prevents Intestinal Tumors in Mice

Abstract

Recent successes in the application of epigenetic drugs for the treatment of myelodysplastic syndrome have raised questions on the safety of long-term administration of DNA methylation inhibitors. We treated preweaned cancer prone Apc Min/+ (Min) mice continuously with the DNA methylation inhibitor zebularine in their drinking water to determine the effects of the drug on normal mouse development as well as cancer prevention. Zebularine caused a tissue-specific reduction in DNA methylation at B1 short interspersed nucleotide elements in the small and large intestines of female Min mice but not in other organs examined after chronic oral treatment. No significant difference in the average weights of mice was observed during the treatment. In addition, analysis of global gene expression of colonic epithelial cells from the females indicated that only 3% to 6% of the genes were affected in their expression. We did not detect toxicity and abnormalities from the histopathologic analysis of liver and intestinal tissues. Lastly, we tested whether prevention of tumorigenesis can be achieved with chronic oral administration of zebularine in Min mice. The average number of polyps in Min females decreased from 58 to 1, whereas the average polyp number remained unaffected in Min males possibly due to differential activity of aldehyde oxidase. Taken together, our results show for the first time that long-term oral administration of zebularine causes a gender-specific abrogation of intestinal tumors while causing a tissuespecific DNA demethylation. Importantly, prolonged treatment of mice with epigenetic drugs resulted in only minor developmental and histologic changes.

Prevention of Helicobacter pylori–Induced Gastric Cancers in Gerbils by a DNA Demethylating Agent

“…Specific global demethylation in the stomach and intestine was also observed in the female Apc min/þ mice administered a demethylating agent, zebularine (23). Turnover of epithelial cells in these tissues is known to be very rapid, being 3 to 4 days in mice (45,46).…”

“…The usefulness of DNA demethylating agents in cancer chemoprevention has been shown in several animal models, including intestinal tumors in Apc min/þ mice (22,23), prostate tumors in transgenic mice harboring probasin promoter-driven SV40 antigen (24), 4-(methyl-nitrosamino)-1-(3-pyridyl)-1-butanone-induced mouse lung tumors (25), and 4-nitroquinoline 1-oxide-induced mouse oral tumors (26). Genetic suppression of a maintenance DNA methyltransferase (Dnmt1) also suppressed tumor development in some of these models (22,27,28).…”

Boswellic acid induces epigenetic alterations by modulating DNA methylation in colorectal cancer cells

“…17,18 Indeed, DAC and zebularine, an oral DNA methylation inhibitor, have been shown to prevent tumor formation in the Apc Min/+ mouse model. 19,20 In spite of its promise, DAC AKBA treatment increased the number of active caspase-3 positive cells, as evidenced by a greater number of bright yellow cells, in all three cell lines, in a dose-dependent manner. These results suggest that AKBA's antitumor effects are mediated both by the induction of apoptosis as well as through inhibition of cell proliferation in CRC cells.…”

DNA Methylation: Its Role in Cancer Development and Therapy

“…When administered chronically in a mouse intestinal cancer model, the average number of polyps decreased from 58 to 1 in female mice with decreased DNA methylation. 146 The therapy was well-tolerated in the chronic dosing schedule. However, when zebularine was administered orally to primates, bioavailability was less than 1%, a disappointing finding considering its in vivo activity when administered orally to murine tumor models.…”