Epigenetic Mechanisms of Quercetin and Other Flavonoids in Cancer Therapy and Prevention

Flavonoids are the most abundant polyphenols in the fruits, vegetables and plant-derived beverages and their presence in food have been associated to many positive outcomes in terms of protection against overall mortality and degenerative diseases. Recent findings suggest that quercetin and other flavonoids may possess the capacity to counteract adverse epigenetic regulation involved in various forms of cancer. Epigenetics is the study of heritable changes in gene expression, independent from those occurring in the genome and includes histone modifications, DNA methylation, post transcriptional gene regulation by non-coding RNAs. In general, hypomethylation leads to activation of genes causing cancer, while global DNA hypomethylation is common in the metastatic phase. In several cases, it has been shown that hypermethylation of tumor suppressive genes determines their silencing which is commonly associated with cancer development. In recent years, several studies demonstrated that dietary factors may influence the structure of chromatin and contribute to regulate both gene transcription and translation. Here, we reviewed the role of quercetin and other flavonoids in regulating epigenetic processes in cancer cells. Being the large part of the studies analyzed based on pre-clinical models, we conclude that, although promising, the impact of flavonoids in the regulation of key epigenetic mechanisms controlling cancer requires the validation of clinical studies.