Epigenetics, Vitamin C, and Abnormal Hematopoiesis - Role of Vitamin C in Epigenetic Regulation in Hematopoiesis Sub-Study on CCUS, Low-Risk MDS, and CMML-0/1

BACKGROUND Recent investigations have shown that mutations in epigenetic regulators are common, both in the apparently normal hematopoiesis of the elderly and in patients (pts) with myeloid cancers. It was long anticipated that DNA methylation was a permanent silencing mark, but with the discovery of the ten eleven translocation (TET) enzymes it became clear that active demethylation occurs. The initial steps in this process are catalyzed by TET enzymes, which are, however, frequently mutated and methylated in hematological cancers. The Jumonji enzymes, which catalyze histone demethylation, are also aberrantly regulated in hematological cancers.

Vitamin C (VitC) was identified in the 1930'ies as the necessary micronutrient in the prevention of scurvy. Unlike plants and most animals, humans are unable to synthesize vitC from glucose due to lack of the required enzyme, L-gulonolactone oxidase. Therefore, vitC must be provided through the diet. Recent studies recognize vitC as an important cofactor for the Fe(II)- and 2-oxoglutarate dioxygenase family. These include the TET enzymes, which are involved in the conversion of 5-methylcytosine (5-mC) to its oxidized derivatives 5-hydroxymethylcytosine (5-hmC), 5-carboxyl cytosine (5-caC), and 5-formylcytosine (5-fC), and the Jumonji enzymes that are involved in histone demethylation. Accordingly, vitC may potentially play an important role in the regulation of DNA and histone demethylation. However, > 80 percentage of hematological cancer pts were found to be severely vitC deficient. Interestingly, analyses of 20 participants included in the investigators' recently conducted randomized, placebo-controlled pilot study (NCT02877277) show that the level of vitC in MDS and CMML pts undergoing treatment with azacitidine, is easily elevated to the normal range by oral vitC supplement (unpublished data). When pts that were already taking vitC supplements were switched to placebo, the vitC levels quickly dropped below the normal range.

It has also been shown that the formation of 5-hmC and its derivatives may be compromised in healthy individuals and pts with TET mutations. However, since many of these mutations are heterozygous, and since the three TET enzymes (TET1, TET2, and TET3) may have some redundancy, restoration of vitC to physiological levels might have an impact on the level of 5-hmC/5-mC in individuals with TET mutant clonal hematopoiesis or hematological cancer.

Analyses of 5-hmC/5-mC levels in peripheral blood (PB) mononuclear cells (MNCs) from the participants in the pilot study also showed a clear trend toward increased 5-hmC in the vitC arm, however, after designing the trial the investigators realized that 5-hmC/5-mC levels are better measured in hematopoietic stem cells in the bone marrow (BM) where the levels are 10-20 fold higher. Thus, the pilot study will be followed-up with a randomized placebo-controlled trial of oral vitC in individuals with low-risk myeloid malignancies; i.e., CCUS or low-risk MDS/CMML, to investigate if oral vitC can change the biology of these disease entities and ultimately prevent progression.

Hypotheses: