Tuesday, April 14, 2009

Some Good News on the Cancer Front

I don't normally post much on science issues, but this one caught my eye:

An experimental treatment that takes an entirely new approach to fighting prostate cancer extended survival in a late-stage study, its maker announced Tuesday.

Seattle-based Dendreon Corp. said that its Provenge cancer vaccine improved overall survival when compared to a dummy treatment in a study of 512 men with advanced disease...

...Provenge is not like traditional vaccines that prevent disease. It's a so-called therapeutic vaccine that treats cancer by training the immune system to fight tumors. If approved, Provenge would be the first such treatment on the market.

This is the second major study in which Provenge has shown a survival benefit, leading some scientists to hope not just for its approval but for a new approach to fighting cancer beyond the surgery, radiation, hormones and chemotherapy used now.

"This is an exciting result, demonstrating that harnessing a patient's own immune system can successfully attack prostate cancer," said Dr. Eric Small, cancer specialist at the University of California at San Francisco. "Now we have more confidence that the initial results we saw were real."

In this humble blogger's opinion, manipulation of the human immune system is far and away the most promising avenue for research into the treatment of cancer. If there is ever going to be a "cure" for cancer, my money is 100% on this approach producing the result. The human immune system is simply amazing. It is incredibly flexible and powerful. And as people in the field of biology know full well, immune compromised patients become susceptible to cancers which are never or rarely observed in healthy patients. This would imply that, in at least these cases, the immune system can actually beat cancer on its own. In fact, it probably does it all the time without our noticing. If it didn't, we'd all contract these cancers. The logical question would be: why can't its repertoire be expanded? The trick is usually recognition of the offending tissues. The immune system works by identifying chemical shapes, usually the folded structure of a macromolecule, especially proteins, which are foreign to the body. This is true of bacterial infections, viral infections, and foreign objects lodged in the body, such as a splinter. It is also the source of complications arising from tissue transplants and blood transfusions, both of which the immune system recognize as foreign and begin to attack. The problem with cancer is that the tissue comes from the host itself. So, the proteins on the surface of these cells are pretty much the same as the host protein, and it becomes hard to distinguish the good tissues from the cancerous ones. Cancer vaccines work by helping the immune system "recognize" the cancerous tissue, just like regular vaccines help the immune system "recognize" an offensive pathogen by giving it a sample of weakened or dead pathogen. Of course, dead bacteria are easy, you just grow 'em up, kill them, and inject them in. The immune cells know exactly what to do. It's a bit more difficult with the cancer, because it is human tissue. What are you going to inject? You have to get a bit more creative in this case. Many methods have been developed, some of them quite ingenious. Once the immune system knows what it is looking for, it can go to work, swarming through the body looking for chemicals that match the signature of the one it has identified as bad. Sometimes it doesn't have enough "killing ability," and sometimes it can be fooled. The malaria pathogen is a good example of this phenomenon, which is the reason malaria is simultaneously so deadly and a vaccine against it has been so difficult to develop. But most of the time, if the immune system can figure out what it is looking for, it is a relentless, ruthless opponent. The odds of a malicious microbe beating it are slim. The approach has even been used in a moderately successful experimental treatement for Alzheimer's, targetting the proteinaceous plaques that destroy brain tissue. So, some good news from me for a change. At least on the cancer front, there is reason for hope!

No comments:

Post a Comment