Joanne Holahan Nurse and Pink Hope Ambassador has done significant research on epigenetics and in this post explains What is epigenetics.
Epigenetics Definition Recently there has been a lot of posts about research and news articles on “Epigenetics” and breast /ovarian cancer being posted. There are literally thousands of article on epigenetics with titles like “Sins of the fathers and the mothers” (1), “you are whatever your mother ate” (2) and research discussing the potential of improving early diagnosis, targeted treatment and possibly gene manipulating cures for cancer (3, 4, 7). So amidst the controversy, confusion and exciting potential is the question, what is “Epigenetics” and what does it mean for us?
In biology, classic Genetics is based on studying changes to DNA sequence, also known as genotype (7). DNA is a molecule that provides the codes for cellular instructions used in the development and functioning of all living organisms. Cells get their instructions on what do to from DNA which acts sort of like a computer program. The cell is the computer or the hardware and the DNA is the program or code.
Within each string of DNA are sets of instructions called genes. One of the overriding beliefs around how cancer develops is that it is initiated and driven by abnormal changes to a person’s gene function (3). To understand how things go wrong, it helps to have an idea of what drives normal cellular development. We each have around 25,000 genes which contain information that instruct the bodys’ cells what to do (2). A gene tells a cell how to make a specific protein. Proteins are used by the cell to perform certain functions, to grow, and to survive. Despite the fact that every cell in a human body contains the same genetic material, not every cell looks or behaves the same (5). Development of an organism is primarily activated by the actions of “regulatory” proteins called transcription factors. These proteins bind to DNA sequences related to specific genes and encourage or discourage replication of the gene sequence (8).
Over the past couple of decades science has looked into gene mutations or variants to explain our susceptibility to diseases that do not have a clear cut genetic cause. It is now believed that epigenetics may provide some answers in explaining many diseases, including cancer (5). One article likens epigenetic changes to “short term bar codes on our cells so that they remember where they’ve been and where they should be going….if they get lost we call it cancer, etc.” (6)
It is becoming more evident that there is another layer of information that sits “above” DNA encoded genetics (2). Unlike classic genetics, epigenetic refers to the study of heritable changes in gene activity that occur without altering the DNA (7). The name epi is Greek for “over, outside of, around” genetics.
Epigenetics Infogram In order for cells to survive and maintain the proper function of the organism, individual genes need to be “turned on” or expressed at different times and slowed down or turned off at others. (9, 10) Epigenetics refer to all the other factors that control how and when each gene is expressed, or about what turns genes on and off ( 3,7,8 ). Epigenetic regulation can be described as chemical flags or markers on genes that are copied when the gene’s DNA is replicated (1, 3). This information can influence how the DNA’s structure is organised in the cell which in turn determines how that gene is expressed and how it controls its normal development. These changes are thought to be influenced by environmental factors (7, 8, 9) especially during early cellular development and can be inherited and passed on through cell generations. This can increase susceptibility to diseases without altering the sequence of the DNA’s molecular building blocks (9). The Age states “Epigenetics takes place when nature meets nurture, where the environment interacts with the genes…”(2)
If an individuals epigenetic profile varies from one cell to another, and in the same cell between health and disease state, what are these markers and chemical labels that when added to DNA can alter gene activity and increase our risk of disease. Epigenetic modifications include DNA methylation, histone modification and post-transcriptional gene regulation or non coding silencing pathways (7, 11, 13). These mechanisms are essential parts of normal cell development though modification and growth to them are known to contribute to cancer development (13, 14, 16). In humans, epigenetic modifications are known to contribute to the various stages of cancer development, including initiation, growth, invasion, metatases and chemotherapy resistance (7, 13, 16). Over 300 genes and gene products have been proposed to be epigenetically altered in various human cancers (13, 16).
(1) The Age, “Sins of the fathers and mothers”. Lifestyle. Thea O’Conner, Monday, January 20 2014
(2) The Age, “You are what you mother ate”. Diet &Fitness. Thursday March 15, 2012
(3) Dawson MA et al. Targeting epigenetic readers in cancer. N Engl J Med 2012, 367;7
(4) Epigenetics as a Therapeutic Target in Breast Cancer. Journal of Mammary Gland Biology and Neoplasia, 2012; 17 (3-4): 191-204
(5) Williams SCP. Epigenetics. Proceedings of the National Academy of Science. 2013, 110;9.
(6) Ptshane M. Faddish Stuff: Epigenetics and the inheritance of Acquired Characteristics. FASEB Journal. 2013;27:1-2
(7) Esteller M. Epigenetis in Cancer. N Eng J Med. 2008;358:1148-59
(8) Ptshane M. Epigenetics: Core misconcept Proceedings of the National Academy of Science. 2013, 110;18:7101-7103
(9 What is Epigenetic. Australian epigenetic alliance. wwwepialliance.org.au/contents/
(10) Epigenetic Research – Garvan institute of Medical Research. www.garvan.org.au/research/cancer/epigenetics
(11) Stein RA. Epigenetics – The Link Between Infectious Diseases and Cancer. JAMA 2011; 305(14):1484-1485
(12) Haitian L et al. Inflammation, a key event in cancer development. Mol CancerRes 2006; 4(4):221-33
(13) Kanwal, R Gupta S. Epigenetic modifications in cancer. Clinical Genetics.
(14) Popiela AL et al. The meaning of the methylation of genomic DNA in the regulation of gene expression levels. Euro J of Genetics
(15) Burdge, GC, et al
(16) Kanwal R, Gupta S. Epigenetic an Cancer. J Appl Physiol, 2010:109: 598-605
(17) Magnani L et al. ChIping away at breast cancer. Lancet Oncology, 2012: 13:12; 1185-7
(18) Wang Y et al. Epigenetic inactivation of BRCA1 through promoter Hypermethylation in ovarian cancer progression. J Ob&G Research, 2013: 39:2; 549-554