Epigenetic is the study of those alterations regulating gene expression without altering DNA sequence and inherited by transmission through cell division.Mutational and epimutational events that alterate cellular growth and division are combined in carcinogenesis.Advances in genome and epigenome-wide analysis identify DNA hypomethylation,hypermethylation of tumor suppressor genes,aberrant histone modifications and/or specific miRNA expression profiles to contribute to tumor initiation and progression.The major challenge for cancer researchers is to enlighten the complex relationship between the epigenetic and genetic machinery in order to optimize combined therapies,reducing chemoresistance and minimizing adverse effects in cancer patients.In this review we will cover many distinct aspects of epigenetic phenomenon.Firstly,we will globally explain the most common epigenetic events and their effects on gene expression regulation.Secondly,we will review the evidence of the correlation between epigenetics and cancer progression,focusing in particular on the effect of aberrant hypo-and hyper-methylation.We will also consider the main methods currently used for methylation analysis,covering both locus-specific technologies and genome-wide analysis.Finally,we will discuss the introduction of novel epigenetic drugs in combination with conventional treatments in order to develop more effective cancer therapies.Such information could help in understanding the important role of epigenetics in cancer.