Epigenetics and Cancer

Epigenetics and  Cancer

INTRODUCTION

  

        

         Epigenetics  is a rapidly evolving study of molecular genetics and biological research. The advancement in the understanding of different  biological activity like DNA methylation, chromatin structure, transcriptional  activity and histone modification has resulted in the development  of epigenetics. Epigenetics changes influence gene transcription  without alteration in the DNA  sequence. The term '' epigenetics was first used by Conrad  Waddington in 1939 to describe ' the causal interaction between the genes and their products, which bring  the phenotype into being.'' In  present  era the term  epigenetics has broadened to include heritable and  transient / reversible changes in gene expression that is not accompanied  by a change in the DNA  sequence. There are two type  of major of major  epigenetic  modification: those occurring  at the DNA level (DNA methylation) and  those occurring at the chromatin  level ( chromatin  remodeling). DNA  Methylation is an  enzyme driven chemical change to the DNA  sequence that most commonly occurs at CpG dinucleotides.  Chromatin remodeling  occurs via modification of the histone residues  by enzymes  primarily  on  the N- terminal  tails and ultimately effects  the interaction  of DNA  with chromatin modifying  proteins. Both DNA methylation and histone modification are associated with silencing critical  tumor suppressor genes and activating oncogones involved in cancer.

        

       Most  of the traditional  molecular studies on cancer are on identifying the genetic mutation or on tumor suppressor gene. Recently, more studies are now focused in discovering new biomarkers  that are epigenetically silenced in early carcinogenesis.  It  is also seen that almost half of the  tumor suppressor genes that  causes familial  cancer through mutations can  also get inactivated with  promoter hypermethylation  in sporadic  cancer. Increasing  evidence suggests  that epigenetic changes  play a key role in  cancer development.

          

          The various  genetic  markers has been used for the early  tumor detection, prognostic prediction and explaining  the genetic pathway of carcinogenesis. But the epigenetics marker has  gained popularity in recent year particularly the promoter hypermethylation which has various  advantages over  a genetic marker.  First promoter hypermethylation is  much more common than genetic alteration  in cancer.  Second promoter hypermethylation occur in the same defined region of that gene  in  all  form of cancer in comparison to wide  range of mutational  variations occur within a specific  gene. Thus epigenetic detection of promoter                                                                                             hypermethylation  will be both efficient and 

                                                                       cost- effective method of tumor detection.