March 21, 2011 | WMU News
KALAMAZOO--The National Cancer Institute within the National Institutes of Health has awarded a three-year $400,000 grant to Western Michigan University to develop a new, cutting-edge treatment for colorectal cancer using viruses to attack cancer cells without harming normal cells.
"This is not a new idea, but it has generated new interest in the last 10 years," Essani says. "What we're doing is really in the beginning, experimental stage."
The idea actually goes back decades to a case in which a person with cancer contracted rabies. When the rabies vaccine was administered, the cancer miraculously disappeared.
Viruses are very specific in the cells they attack. They often differentiate between species of animals and even the type of cells within that species. So theoretically, a virus could be developed to attack specific cancer cells and leave other cells untouched.
Some research is already under way into using viruses to attack a number of different human tumors, Essani says. His project will take a rare, nonfatal African virus known as the tanapox virus, which infects monkeys and humans, and use it to treat colon cancer. Colon cancer is a particularly troubling and potentially deadly cancer for which conventional treatment is not always effective and causes unwanted side effects.
"We thought if we could take this virus and modify it in such a way that it will only infect and destroy human colorectal cancer cells and not normal cells, then that would be really outstanding," Essani says.
The viral cancer therapy would work something like penicillin, Essani says. Penicillin targets bacterial cells, but does not harm normal human cells. An oncolytic virus, in a similar manner, only infects and destroys cancer cells without harming healthy human cells.
"Unfortunately, it has been very difficult to find such targets in cancer," Essani says. "The reason for this is because it's very difficult to differentiate between a normal cell and a cancer cell at the molecular level."
Essani and his team of three students plan to take human colorectal cancer cells and transplant them onto nude mice--specially bred laboratory mice that do not mount a rejection response because they have an inhibited immune system. The team then will treat the nude mice with tanapox virus mutants they have genetically designed to see if they can kill the human cancer cells. If that goes well, they will try it on monkeys and finally humans.
The tanapox virus is ideal because it is confined to equatorial Africa and people outside that region have no immunity to it. If people were immune to the virus, it could not replicate itself and attack the cancer cells. Additionally, it only causes a mild, transitory, febrile illness in humans, which is self-limiting.
Chemotherapy and radiation both are used to fight colon cancer. But both are not always effective and may be accompanied by some serious side effects, including nausea, diarrhea and suppression of the immune system. In addition, cancer cells can become resistant to chemotherapy drugs.
"With viruses, we do not expect to see any of this," Essani says.