Epigenetic Control of Genes Involved in Cancer Initiation and Progression

Aberrant changes in gene expression that regulate the cell cycle, cell division and cell death are major contributing factors to the genesis of tumors. Tumors arising from heritable epigenetic changes governed by epigenetic mechanisms are treatable by the use of compounds that reverses the epigenetic change, as the DNA sequence remains unaltered. DNA methylation and histone modifications are primary mechanisms that induce epigenetic changes and are well studied. Micro RNAs, which are about 20–25 nucleotides long RNA sequence, are also emerging as important epigenetic regulators in tumorigenesis. As evident in many cancers, tumors are heterogeneous in nature and therefore a common epigenetic signature that dictates the onset or the progression of the diseases is hard to determine. In addition to tumor heterogeneity, epigenetic processes are highly dynamic and therefore rather than single epigenetic events, the combination of epigenetic patterns obviate the changes. However, most tumors strongly exhibit epigenetic dysfunctions of genes crucial to the cell cycle. The analysis of epigenetic changes, degree of the change and reversal of epigenetic alterations is important to the diagnosis, prognosis and therapeutics of various cancers. The goal of this chapter is to discuss genes that are susceptible to aberrant epigenetic modifications and the influence of the altered epigenetic states in tumorigenesis. The assessment and detection of epigenetic patterns, degree of methylation of genes involved in tumorigenesis as potential biomarkers for the diagnosis and prognosis of the disease will also be presented.