There exists a "type" of cancer that is common yet rarely discussed—metastatic cancer, or cancer that has spread from the part of the body where it originated (the primary tumor) to another (such as lungs, bones or liver). Although much research is being done to combat primary tumors, there still exists a crucial need to find a treatment that can be effective against metastatic cancer, or "mets." Could a virus be the answer that finally beats the mets?
Researchers are looking into harnessing viruses to infect, multiply within and subsequently destroy cancer cells; the virus targets tumors without affecting normal tissue. Several types of these viruses have been developed to date, with names like adenovirus, poxvirus and picornavirus. Even the herpes simplex virus is under consideration for this type of use. Another class of viruses, known as reoviruses, is being studied by the National Institutes of Health. These viruses appear to be especially effective in treating metastatic cancers.
Reoviruses are found everywhere in nature and have been isolated from untreated sewage, river and stagnant waters. These viruses choose to colonize cancer cells that exhibit a group of common mutations, that result in an "activated Ras pathway," while sparing normal cells. Normal cells are unaffected by the reovirus becausethey lack these mutations. Approximately two-thirds of human cancers have the mutation that makes them a prime target for reoviruses.