Tuesday, September 1, 2009

Conquering cancer one virus at a time

Back in June, I participated in The Ride to Conquer Cancer, a 2-day bike ride between Vancouver and Seattle to raise money for BC Cancer. It was an extremely moving, positive and rewarding experience. It also gave me a chance to eat a piece of humble pie when 70 year-old cancer survivors (identified by flags on their bikes, adding to their wind resistance) would pass me going up the hill. The good news is that at the end of the 272 km, I was still smiling:

The bad news is that I didn’t conquer cancer.

Cancer research is well-funded, popular, and has been around for quite some time. So why can’t we get rid of this disease? The problem with cancer is that it’s tremendously difficult to target. Unlike cells infected by viruses and bacteria, cancer cells don’t display any obvious flags that something is wrong with them, which makes them challenging to distinguish from healthy cells. Therefore, most treatments for cancer involve killing a number of healthy cells, and that’s just not ideal.

Progress is being made, though, as a recent publication in the journal PNAS suggests. In this paper, a collaboration between researchers in California and in Japan lead to the discovery of a new way of identifying tumors for easier removal. They rely on an unlikely ally: viruses.

The researchers genetically engineered a special type of virus to carry a gene that codes for a fluorescent protein, GFP (for Green Fluorescent Protein - as simple as that!). If all the cells in your body were to be infected by that virus, you would glow (kind of like the famous puppy). While this would immediately up your popularity ranking at any science party, it doesn’t do much for treating cancer. So the researchers took it one step further and engineered the virus so that it would only express the fluorescent protein (make the cell glow) if the cell has an active telomerase. Telomerase in an enzyme involved in the replication of cells. If the telomerase enzyme is active when it shouldn’t be, it can cause cells to divide indefinitely, creating tumors. In fact, it is thought that over 90% of human tumors show telomerase activation. To sum it up, cells are infected with a virus that has a gene for a fluorescent protein, but only cancerous cells have an active telomerase, the switch that turns on the fluorescence. The result? Glowing tumors.

The benefits of these findings are two-fold. First, glowing tumors mean that surgeons can precisely remove the tumors without having to also remove a chunk of healthy tissue “just to make sure”. Second, tumors have a nasty habit of hitching a ride in your lymphatic system or your blood and disseminate throughout your body, making it very difficult to take out every little bit of sprouting tumor. With this innovation, all those little disseminated tumors can be identified and removed. Those two benefits together could greatly reduce the chance of a relapse, an important consideration when treating cancer. The researchers tested their mutant virus in two different types of animal models of cancer (colon and lung) with great success. While I’m usually worried at the prospect of glowing body parts, this research could have a big impact on cancer treatment.

If I want to give myself a chance to conquer cancer in 2010, I should probably spend less time on the computer and more time on the bike...

Glowing tumors

Reference: In vivo internal tumor illumination by telomerase-dependent adenoviral GFP for precise surgical navigation. (2009) Kishimotoa, H., Zhaoa, M., Hayashia, K., Uratad, Y., Tanakac, N., Fujiwarac, T., Penmanf, S., and Hoffmana, R.M. Proc Natl Acad Sci 106(34):14514-7.

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