As you probably already know, proto-oncogenes;i.e. the precursors for oncogenes which go on to become a factor in a multi-hit pathway to cause various forms of cancers, may become activated by DNA mutations. Cancer is not caused by one phenomenom, but a number of processes that may be recognized by the cells to become injurious to the body and cause the cells themselves to become immortal, vascularize, and ultimately metastasize to various parts of the body. Once the cancer has metastasized, it becomes very difficult to treat by radiation or surgical techniques. This is because the cancer has now grown in many different parts of the body and is no longer localized in one body part. A cancer that has metastasized may still be treated by chemotherapy; but chemotherapy has many adverse effects to the human body and is not as effective as radiation treatment or surgery in removing the cancerous cells. It has been recently found that mutations in the DNA of humans that the cancer-causing precursors, known as proto-oncogenes, may activate these DNA sequences to become oncogenic and thus cancer forming. These mutations may be caused by UV light or excessive exposure to various types of radiation as well as being random. It is highly recommended that people should be routinely checked out by their family doctor for various types of common cancers. Blood tests and stool tests are highly recommended as well. In the mean time, individuals should use plenty of sun screen in the summer.