Naturally occurring small molecules include a large variety of natural products from different sources that have confirmed activity against epigenetic targets. In this work we review chemoinformatic, molecular modeling and other computational approaches that have been used to uncover natural products as inhibitors of DNA metiltransferases, a major family of epigenetic targets with significant potential for the treatment of cancer and several other diseases. Examples of these computational approaches include docking, similarity-based virtual screening, and pharmacophore modeling. It is also commented the chemoinformatic-based exploration of the chemical space of naturally occurring compounds as epigenetic modulators which may have significant implications in epigenetic drug discovery and nutriepigenetics.

Recent studies have demonstrated an important role for vitamin C in the epigenetic regulation of cancer-related genes via DNA demethylation by the ten-eleven translocation (TET) methylcytosine dioxygenase enzymes. DNA methyltransferase (DNMT) reverses this, increasing DNA methylation and decreasing gene expression. Dual oxidase (DUOX) enzymes produce hydrogen peroxide (H2O2) in normal pancreatic tissue but are silenced in pancreatic cancer (PDAC). Treatment of PDAC with pharmacologic ascorbate (P-AscH-, intravenous, high dose vitamin C) increases DUOX expression. We hypothesized that inhibiting DNMT may act synergistically with P-AscH- to further increase DUOX expression and cytotoxicity of PDAC. PDAC cells demonstrated dose-dependent increases in DUOX mRNA and protein expression when treated with DNMT inhibitors. PDAC cells treated with P-AscH- + DNMT inhibitors demonstrated increased DUOX expression, increased intracellular oxidation, and increased cytotoxicity in vitro and in vivo compared to either treatment alone. These findings suggest a potential therapeutic, epigenetic mechanism to treat PDAC.

Retinoblastoma (Rb) is a rare cancer that nonetheless represents the most common ocular malignancy in children. Rb exists as familiar and sporadic cancer and the increasing incidence of the sporadic one and its pathogenesis is mostly unknown. To date the management of retinoblastoma requires intensive chemotherapy and sometimes invasive surgery in order to preserve vision and quality of life in Rb patients. The discovery of the epigenetic nature of non-hereditable/sporadic Rb led to the development of high-throughput precision investigation strategies for the study of its epigenetic landscape. Here we investigated the effect of the demethylating 5-Aza-2’- deoxycytidine (Decitabine; DAC) agent on preclinical models to assess its possible use as anti-cancer drug in the treatment of Rb patients. We found that DAC treatment induced cell cycle arrest and apoptosis in Weri-Rb-1 cells. We investigated the variation of differential gene expression profile in Rb cells in relation to time of exposure to DAC with respect to controls. Network map analysis evidences 15 hub/driver genes, which share pathways of regulation of TNF-, FAS-, p53-dependent apoptotic signaling and NF-kB pro-survival pathways. Furthermore, a computing expression profile analysis of publicly available datasets of patients’ primary tumors and normal retina cell-derived organoids vs WeriWeri-Rb-1 DEGs depicted the relevancy of these 15 hub genes on retinoblastoma genesis. The antiproliferative effect of DAC treatment on Rb was confirmed in vivo, both in subcutaneous xenograft and orthotopic models also showing the changes the gene methylation status in treated Weri-Rb-1, shedding a new light on the reprogramming antiproliferative dynamics induced by the epigenetic therapy and on the role of this therapeutic approach to spare children sight and life.

Background: Despite recent advances in epithelial ovarian carcinoma (EOC) treatment, recur-rence and mortality rates have not improved significantly. DNA hypermethylation has generally been associated with ominous prognosis and chemotherapy resistance, but the role of DNMTs in EOC remains to be investigated. Methods: In the current study, we systematically retrieved gene expression data from patients with EOC and studied the immunohistochemical expression of DNMTs in 108 primary and 26 relapsed tumors. Results: Our results showed that DNMT1, DNMT3A, DNMT3B and DNMT3L RNA levels were higher and DNMT2 lower in tumors compared to non-neoplastic tissue, and DNMT3A and DNMT2 expression decreased from Stage II to Stage IV carcinomas. Proteomic data also suggested that DNMT1 and DNMT3A levels were increased in tumors. Similarly, DNMT1, DNMT3A and DNMT3L protein levels were overex-pressed and DNMT2 expression was reduced in high grade carcinomas compared to non-neoplastic tissue and low-grade tumors. Moreover, DNMT1 and DNMT3L were increased in relapsed tumors compared to their primaries. DNMT3A, DNMT1 and DNMT3B mRNA lev-els were correlated with overall survival. Conclusions: Our study demonstrates that DNMT1 and DNMT3L are upregulated in primary high grade EOC and further increase in relapses, whereas DNMT3A is upregulated only in the earlier stages of cancer progression. DNMT2 downregulation highlights a presumptive tumor-suppressor activity of this gene in ovarian car-cinoma.