[Frontiers in Bioscience, Landmark, 25, 1058-1109, March 1, 2020]

Epigenetic alterations in cancer

Suganya Ilango1, Biswaranjan Paital2, Priyanka Jayachandran1, Palghat Raghunathan Padma1, Ramalingam Nirmaladevi1

1Department of Biochemistry, Biotechnology and Bioinformatics, Avinashilingam Institute for Home Science and Higher Education for Women, Coimbatore, 641043, Tamil Nadu, India, 2Redox Regulation Laboratory, Department of Zoology, CBSH, Odisha University of Agriculture and Technology, Bhubaneswar-751003, India


1. Abstract
2. Introduction
3. Importance of epigenetics in cancers
4. Biological basis of cancer
    4.1. Epigenetic mechanisms in normal cells
    4.2. Epigenetic mechanisms in cancer cells
    4.3. Epigenetics of cancer in relation to aging
5. DNA methylation
    5.1. Role of DNA methylation in cancer
    5.2. DNA hypomethylation in cancer
    5.3. Epigenetic alterations involving DNA methylation by mutation
    5.4. DNA hypermethylation in cancer
    5.5. DNA demethylation
6. Histone modifications
    6.1. Non histone methylation
7. Nucleosome remodelling
    7.1. Changes in chromatin
8. Micro RNAs (miRNAs)
    8.1. miRNA biogenesis
    8.2. Biological roles of miRNAs
9. Regulation of epigenetics in cancer progression
10. Role of oxygen and cancer
    10.1. Normoxia and cancer
    10.2. Hypoxia
      10.2.1. Functional effect of epigenetic regulation upon hypoxia
      10.2.2.. Importance of epigenetics in tumor hypoxia and cancer immunotherapy
11. Epigenetic therapy
12. Acknowledgments
13. References


Genetic and epigenetic modifications in DNA contribute to altered gene expression in aging and cancer. In human cancers, epigenetic changes such as DNA methylation, histone modifications, micro RNAs and nucleosome remodelling all control gene expression. The link between the genetics and epigenetics in cancer is further shown by existence of aberrant metabolism and biochemical pathways in cancer or mutation in genes that are epigenetic players. Reversal of these epigenetic changes has been clearly shown to have therapeutic value in various forms of lymphoma and preleukemia and similar results are appearing for the treatment of solid tumors. In this review, we discuss the functional effects of epigenetic changes inducible by hypoxia, the epigenetic alterations in cancer and how they contribute to tumor progression and their relevance to epigenetic therapy.


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Key Words: Epigenetics, Cancer, Hypoxia, DNA Methylation, Histone Modifications, miRNAs, Chromatin.

Send correspondence to: Ramalingam Nirmaladevi, Department of Biochemistry, Biotechnology and Bioinformatics, Avinashilingam Institute for Home Science and Higher Education for Women, Coimbatore, 641043, Tamil Nadu, India, Tel.: 91-9976152000, E-mail: nirmaladevi.saravanan32@gmail.com