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Viruses vs. Cancer: Go Viruses!

April 10, 2009 at 2:51 pm
By Collin Hazlett

The measles virus is definitely not a fun thing fun to have in your body when it is attacking your cells and using them to make more of itself. You probably consider it to be an enemy. But have you ever thought about the power that would be at your fingertips if you MADE FRIENDS WITH the measles virus? About the possibilities that would open up if you could somehow win a virus over to your side and hire it out as a mercenary to take down much nastier microscopic menaces- like cancer cells?

Dr. David Dingli, of the Mayo Clinic Department of Molecular Medicine, has thought about this a lot. Dr. Dingli recently came to Carleton to give a presentation on his research involving recombinant viruses: he edits the genes of the ordinary, yucky viruses we all know and hate, in order to turn them into new, helpful superhero viruses capable of fighting cancer cells.

The measles, in particular, is Dr. Dingli's weapon of choice against cancer. The measles already doesn't get along very well with cancer--even a normal, unmodified measles virus is more likely to attack a cancer cell than a healthy cell, and contracting the measles can actually destroy a cancer patient's tumor. However, Dr. Dingli and his associates don't give cancer patients the measles. They use a genetically modified form of the measles, whose genes they carefully patched together from measles genes and various other sources, which they have named MV-NIS.

MV-NIS, unlike its infamous cousin, does not attack normal cells but goes straight for cancer cells. Once it gets inside, it not only replicates itself and starts killing the cancer cell from within, but it also messes with the cell's DNA to cause it to produce lots of a protein called NIS. NIS is a protein that binds to iodine. When infected with MV-NIS, a cancer cell suddenly becomes an iodine magnet. So Dr. Dingli's next move after injecting the virus is to follow it up with an injection of radioactive iodine, which the cancer cells greedily drink up. Radioactivity being just as unhealthy for cancer as it is for people, this is very harmful to the tumor cells. (Unfortunately, it is also dangerous for anything nearby, so Dr. Dingli makes sure to use radioactive iodine that emits alpha particles--which are quite powerful but not long-ranged enough to reach far into healthy areas of the body.) After taking in the radioactive iodine, the cancer cells shoot alpha particles at each other, and, if all goes according to plan, kill each other off.

Cancer cells mutate quickly, though. One problem with a lot of cancer treatments is that the cancer mutates and becomes resistant to whatever is being used against it. For MV-NIS, says Dr. Dingli, this is no longer a problem--viruses mutate even faster than cancer cells, so they can beat cancer at its own game. As soon as the tumor becomes resistant to the virus, the virus adapts its strategy and continues the attack. Also, only one dose is necessary for treatment. MV-NIS, unlike other medicines, creates more of itself once it is in the body.

The interaction between the healthy cells, the cancer cells, the viruses, and the radioactive iodine is very complex- each different combination of inputs results in a different cycle of death and regrowth for the tumor. The idea is to put in just the right amount and type of virus and just the right amount of iodine so that the resulting cycle has one particularly low point for the tumor, when it is small enough to be finished off by conventional means. Finding this just-right cycle requires the awesome power of mathematicians, who are working out a model of the system and optimizing the correct combination of factors right now. Surprisingly, it seems to be better to use a version of MV-NIS that actually waits a little while before killing the cancer cells itself. This way it has more time to spread to other cancer cells and convert them into radioactive alpha-particle-firing battlestations.

It's good to see viruses working to heal people, for a change. Maybe they've gotten a bad rap in the past. In any event, MV-NIS is a model for its fellow viruses to follow. As for us humans, we can look at Dr. Dingli's inventiveness and drive to help sick people as our model.