Epigenetic alterations play a critical role in cancer initiation and progression in addition to genetic alterations. Epigenetics includes changes such as DNA methylation, microRNA and histone modifications, which together make up the epigenome . Here we focused on the histone modifications that play a crucial role in cancer development and progression. Chromatin structure plays an important role in regulating various nuclear functions such as transcription, replication, recombination and DNA repair. Regulation of gene expression is known to be involved in the binding of transcription factors in target gene promoters but it is also dependent on how the epigenetic events, including histone marks, are characterized. Basically, the local modification of chromatin structure by histone modifications can lead to activation or inactivation of gene expression. For example, some histone modifications such as tri-methylated histone H3 at lysine 27 (H3K27me3) are known to inactive gene expression.