Cancer Therapy: Going to the Dogs

29. May 2009

US scientists developed a new strategy against cancer. They bound nitrogen monoxide to vitamin B12 and smuggled the active ingredient in the malign cells of tumors in dogs as a Trojan horse. The result: The sick animals recovered noticeably.

The ten year old Bichon Frisé named Oscar developed an adenocarcinoma in the anal sac. This particularly malignant type of cancer should kill the male dog within three months. Against this prognosis the dog leaved to see another five years of a good quality dog’s life.

Undetected Trojan

The distressed owner did not want to have the dog put to sleep after all therapy approaches failed. He turned to the Taussig Cancer Institute in Cleveland/USA. Joseph Bauer, at this time scientific assistant at the Cleveland Clinic’s Center for Hematology & Oncology Molecular Therapeutics, had provided the veterinarian treating the dog with not yet approved cancer drugs within an experimental study. At the same time two other dogs have received the drug Nitrosylcobalamin (NO-Cbl) as well.

Here NO-Cbl works like a Trojan horse by binding to vitamin B12 receptors on cells surfaces. For a rapid cell proliferation cancer cells need a particularly high amount of vitamin B12 thus having a high number of receptors for this vitamin. If the effect of vitamin B12 is blocked the process of the potentially deadly reproduction process of malign cells is interrupted.

After 15 months of daily therapy with NO-Cbl the tumor shrank by 43 percent. Only two weeks after the start of the treatment first results showed. The ten months therapy of another deadly sick dog with thyroid carcinoma made its tumor shrink by 77 percent. And the peripheral nerve sheath tumor of another animal shrank by 39 percent after a nine months’ treatment. This reports Bauer during the national meeting of the American Chemical Society in Salt Lake City/USA. According to his own statement no side effects were observed. The antineoplastic effect of NO-Cbl had been subject to research for a long time (PLoS ONE 2007; 2(12): e1313. doi:10.1371/journal.pone.0001313).

Doggies preferred

Obviously dogs are much more suitable for active ingredient studies against cancer than mice. Normally the tumor is induced by genetic manipulation in mice. The dogs on the other hand had developed a cancer spontaneously, just like the human being. In addition dogs are genetically a lot closer to humans than mice. Plus they are exposed to the same environmental conditions. Experimental chemo therapeutics frequently achieve a response rate of 80 percent and more in mice. But those successes decrease to a disappointing 10 to 15 percent in human beings explains Bauer.

The research area still appears to be promising enough for the U.S. National Cancer Institute to bring the Comparative Oncology Program into being for researching chemo therapeutics specifically on dogs. In addition the first U.S. tissue bank for dogs was opened in 2007 which collects tissue and blood samples of dogs suffering from cancer.

A healthy doggie makes a happy owner

Currently Bauer and his study group research with ten dogs suffering from cancer. They are treated and observed with the support of their veterinarians for one year. The results are planned to make way for phase 1 studies on human beings. Most of the cancer drugs for dogs and other pets were developed in the Fifties, a complaint heard from both, researches and veterinarians. It is a completely different ball game – cancer therapy of dog and of man. The studies of Bauer might bring advantages for both species.

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