Carcinogens can be either man-made, such as cigarette smoke, or present naturally in the environment, as is ultraviolet radiation from the sun, both of which are known to play a major role in the development of cancer. Carcinogens can also enhance other factors that cause the cancer. Certain cancers develop slowly. It can take from 5 to 40 years for cancer to develop after exposure to a cancer-causing agent, making identification of carcinogens difficult. Oncogenic viruses These are pictures from the BRCA1 lab.
Scientists work here studying the gene which is thought to cause breast cancer.
Oncogenes are genes within a cell that may initiate the cells' transformation from normal to malignant. Some known oncogenes are the BRCA 1 gene which is linked to breast cancer or the gene linked to colon cancer. Oncogenic viruses are viruses that are linked to cancer. Researchers have found that the immune system may recognize the difference between healthy cells and cancer cells and eliminate those that become cancerous. Cancer may develop when the immune system breaks down or is overwhelmed.