Get this and be clear about it. Many cancers are infectious; they arrive because of infective organisms and can be passed from person to person. 20% of all cancers are caused by infections and, 80% of those, it’s a virus.
An oncovirus is a virus that can cause cancer. This term originated from studies of retroviruses in the 1950–60s, often called oncornaviruses (onco-RNA-viruses) to denote their RNA virus origin. It’s amazing that viruses don’t cause many more cancers than they do, because a virus is basically a bunch of nasty DNA/RNA that gets into the cells it infects.
Cancer is also basically nasty DNA/RNA. There could come a day when we realize that ALL cancers are infections. That would explain why cancer is basically a disease of the immune system. A vibrant and healthy immune system remains your best insurance against cancer.
Burkitt’s lymphoma (or “Burkitt’s tumor” or Burkitt lymphoma) is a cancer of the lymphatic system (in particular, B lymphocytes). It is named after Denis Parsons Burkitt, a surgeon who first described the disease in 1956 while working in equatorial Africa. It was, essentially, the first confirmed human cancer caused by a virus.
By 1964, Anthony Epstein and Yvonne Barr identified the first human cancer virus from Burkitt lymphoma cells. A herpes-group virus, this virus is formally known as human herpesvirus 4. But it is more commonly known as Epstein-Barr Virus or EBV, after the discovers.
There are many other cancer-causing viruses known, of which HPV (human papilloma virus, which causes cervical cancer) is probably the most well-known. But for sure the list is going to grow and grow and grow.
How does it happen? Scientists have found a clue. When cells sense that an oncogenic virus is trying to “take over”, a process known as “oncogenic stress”, they switch on a signal that keeps the virus in check. But if that mechanism fails, then cancer could be the result. The race is on to find out how to operate the anti-viral signaling mechanism.
The Epstein-Barr virus (EBV) is a notorious human pathogen. Antibody tests show that it infects 90% people at some point in their lives. The resulting disease has various names: infectious mononucleosis (mono), Pfeiffer’s disease, “the kissing disease” (because of its oral transmission) or glandular fever in most English-speaking countries.
Mono can be a severe and debilitating illness and the origin of so-called chronic-fatigue syndrome for many. But fortunately it rarely causes cancer. People with immune systems weakened by HIV infection, or because they have had an organ transplant, or some other reason, are at greater risk of developing forms of lymphoma.
Now researchers have found that when lab cultures of primary human B cells are infected with EBV, they remain in an “immortal” state, producing lymphoblastoid cell lines indefinitely (lymphblastoid means likely to form lymphoma cells). This could be how EBV, if unchecked, eventually causes cancer in the human body.
[Cell Host & Microbe, Volume 8, Issue 6, pp 510-522, 16 December 2010, DOI:10.1016/j.chom.2010.11.004]