Genetic and epigenetic changes regulated by bioactive molecules in cancer therapeutics

Cancer biogenesis stems from genetic and epigenetic changes that regulate various signaling pathways responsible for growth, division, and proliferation. Genetic changes occur through mutations that contribute to loss of function, overexpression or repression of proteins involved in metabolic pathways. The changes place individuals at risk to diseases, including cancer. However, epigenetics is a mechanism of gene control that occurs through changes in chromatin structure without alterations to the DNA sequence and is mostly reversible. Epigenetic alterations have been implicated in colorectal cancers (CRCs), transforming normal colonic epithelial cells. Aberrant DNA methylation and chromatin modifications have been shown to contribute to CRCs. These mechanisms alter genes that drive the initiation and progression of CRC. The novel approach of using diet-derived bioactive molecules that reverse the nature of epigenetic events that control gene expression important to apoptosis, differentiation or cell death pathways may serve as a treatment option for CRC. The aim of this dissertation was to determine the effectiveness of epigallocatechin-3-gallate (EGCG) and sodium butyrate (NaB) as epigenetic modulators against CRCs. Our investigation showed that the combination of EGCG and NaB was effective against CRCs by reducing cell viability and inhibiting colony formation, inducing apoptosis and cell cycle arrest in G2/M phase for p53-wild type (WT)-expressing RKO and HTC-116 and G1 phase for p53-mutant HT-29 CRC cells, decreasing survivin, a highly upregulated anti-apoptotic protein for all CRC cell lines tested, inducing nuclear p21 in a p53-dependent manner in RKO CRC cells and inducing phosphorylated γ-H2AX a marker of DNA damage in RKO CRC cells. The EGCG and NaB combination also led to increased nuclear NF-κB-p65, a protein found to be associated with DNA damage in order to enhance repair mechanisms, in RKO CRCs, and a down-regulation of DNA methyltransferase1 (DNMT1) in all three CRC cell lines as well as decreased DNNMT3A and 3B levels and percent CpG methylation in RKO CRC cells. Further, HDAC activity was reduced in all cell lines tested. The levels of acetylated H3 level an epigenetic marker for gene expression was also observed in response to EGCG and NaB treatment in RKO CRC cells. Taken together, these findings demonstrate that EGCG and NaB are promising and effective chemotherapeutic bioactive molecules against colorectal cancers.