Saturday, June 27, 2009

Ad blockers

The potbangers keep bringing up Introgen (see the comments on this story in the Eagle, for example). So Vision 1920 will retell the tale of Introgen, even if it mans having to get faculty input again.

As noted in an earlier post, Mr. David Nance, formerly of Introgen, is a biotech expert who has been advising the Governor for years. His company, Introgen, was founded on the work of Dr. Jack Roth of M.D. Anderson
Advexin, which expresses the tumor-suppressing p53 gene, is the first gene therapy to succeed in a U.S. phase III clinical trial for cancer. Jack A. Roth, M.D., a professor in the Department of Thoracic and Cardiovascular Surgery, invented the therapy and co-founded Introgen Therapeutics, Inc., the company that makes Advexin.

“The p53 protein,” Dr. Roth said, “is called ‘the guardian of the genome’ because it protects against damage to the cell. We are all constantly exposed to agents such as sunlight or tobacco smoke that can cause gene mutations. When the gene is functioning normally, p53 can actually help facilitate repair of those mutations or eliminate the damaged cell.”

In most cancers, however, p53 is defective. The thinking behind the Advexin protocol was to take a normal p53 gene and put it into p53-defective tumor cells to cause apoptosis—death—of the cancer cells but not of normal cells. According to Dr. Roth, “When the p53-expressing adenovirus is injected directly into tumors, it causes the tumors to shrink or to stop growing. And in a few cases, there are very dramatic responses where the tumors disappear completely.”
If you can inject something directly into a tumor, why not just kill it directly instead of using this p53-whatsit to turn on a program that kills the cell? Here's why: Traditional cancer therapy is known as slash, burn, and poison. You cut out the cancer, but you might miss some and it comes back. Same if you burn it out with radiation. Chemotherapy poisons the cancer but it poisons everything else in the body at the same time; that's why chemo patients lose their hair, lose their appetites, and are prone to infections. Unless you can deliver the poison only to the cancer cells, what you want is something that's a poison to the cancer cell but not to the patient's normal cells... and that's how p53 is supposed to work.

Introgen was based on the idea that you could deliver p53 everywhere. When it hit a normal cell, nothing would happen because there was already normal p53 there. when it hit a cancer cell that lacked p53, the incoming p53 would detect that the cell had problems and tell it to commit suicide (apoptosis means programmed cell death).

To implement this strategy, Introgen needed a delivery system. Back when they started, the delivery system of choice was Adenovirus.

To be continued...

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