Since the discovery of oncogenes as well as tumor suppressor genes it has been known that a large factor of causing and repressing cancer is within our own genome. If areas around oncogenes become unmethylated these cancer-causing genes have the potential to be transcribed at an alarming rate. Opposite of this is the methylation of tumor suppressor genes.
The revelation of oncogenes and tumor suppressor genes has shed light on the fact that a major contributor to cancer development is inherent in our own genetic material. When regions surrounding oncogenes become unregulated, these genes can be overexpressed at an alarming rate. Conversely, the silencing of tumor suppressor genes through methylation.