One of the causes of cancer is abnormal genes. Cancer causing genes are called oncogenes and genes that prevent cancer are called tumor suppressor genes. Cancers can occur when the normal genes are not functioning normally. Genes, as you know, are the blueprints to the body. They tell a cell what it will be and what it will do. We could not function if the process did not run well. There is a system in place that is designed to keep good genes running and suppress bad genes. This process is called epigenetics.
Epigenetic changes are modifications to the genome that are heritable during cell division but do not involve a change in DNA sequence. Expression of genes is not regulated by the DNA sequence, which is the same in every cell, but by epigenetic marking and packaging. This process regulates chromatin structure through DNA methylation, histone variants, post-translational modifications, nucleosome positioning factors or chromatin loop and domain organization.
How can this cause cancer? Well, if a tumor suppressor gene is abnormally turned off, or an oncogene is turned on, then cancer (carcinogenesis) can occur. One key is a chemical change to the DNA called methylation. First, we need to define the process to make it clearer.
DNA contains four bases: adenine, guanine, cytosine, thymidine, but there is a fifth base methylated cytosine. DNA methyl-transferase (DNMT) produces methyl-cytosine where cytosines precede guanine (CpG). The CpG areas are not symmetric but clustered in CpG islands located at promoter regions. The promoter region is the region at the beginning of a gene and it controls the start of gene transcription. If the promoter is off, then the gene never is expressed.
Abnormal methylation in cancer has been known for 20 years. Hypo-methylated areas turn on normally silent areas such as virally inserted genes or inactive X-linked genes. Hyper-methylated areas silence tumor suppresser genes.
We know that cancers have abnormal levels of methylation and we know foods can help prevent cancers. Is there a link between foods and epigenetics? Yes!
The study of food nutrients and their effect on disease through epigenetics is known as nutrigenomics. This is a growing field, in fact, it is exploding. A Google search for the term nutrigenomics produces 127,000 entries.
Epidemiologic studies suggest there are bad foods and good foods. BAD: red meat, processed meat, grilled meat, dairy, animal fat, partially hydrogenated fats. Good: Fish, fruits, vegetables, tree nuts, omega-3 fatty acids, whole grains.
You can study the epigenetic effects of bad or good foods. I’m going to talk about some of the cancer preventing foods and how their mechanisms include epigenetic effects.
Foods with epigenetic effects include green tea, cruciferous vegetables, and grapes. Usually we hear about antioxidants and foods. Antioxidants are important but there are beneficial substances in foods called polyphenols which can affect genes. Of the polyphenols, different forms exist but flavonoids are the most highly cited for health benefits and are found in a variety of vegetables and fruits. Types of flavonoids include …