Posted on 11/16/2001 3:24:20 PM PST by Map Kernow
A CANCER treatment that works like a "Trojan horse", delivering a single radioactive atom inside cancer cells and then unleashing a shower of atomic fragments to kill them, has been developed by scientists.
In the laboratory the technique killed a variety of cancer cells - including breast, leukaemia, lymphoma, ovarian, neuroblastoma and prostate - and tests on humans could begin next year. The treatment could be administered by injection at a doctor's office or outpatient clinic.
The atoms, known as nanogenerators, use a minute dose of radiation - a picocurie, which is a millionth of a millionth of the standard unit of radioactive decay. Tests on mice with prostate cancer and the blood cancer lymphoma have prolonged life without side effects.
A team at Memorial Sloan-Kettering Cancer Centre in New York reveals today in the journal Science that nanogenerators consist of a single radioactive atom held in a molecular cage that is in turn attached to an antibody that homes in on cancer cells. The antibody circulates in the body and carries the nanogenerator inside cancer cells and destroys them.
Dr David Scheinberg, the team leader, said: "We have found an effective way of containing and then delivering this highly potent element directly into cancer cells. One atom will kill a cell."
Dr Scheinberg and his colleagues tested the treatment in two mouse models, one for prostate cancer and one for widespread lymphoma. Many of the animals had long-term survival, and all of them had their lives extended after a single treatment at a low dose.
In many of the mice with prostate cancer levels of a chemical linked with the disease, a marker known as PSA, decreased to zero.
The atom contained inside the nanogenerator is actinium-225, a radioactive isotope that decays by giving off short-lived, high-energy alpha particles that blast through cancer cells and destroy their genetic material and proteins.
When actinium decays, it produces a series of three daughter atoms, each of which gives off its own alpha particle. Each particle increases the chance that the cancer cell will be destroyed. "You get four times the punch from one atom," Dr Scheinberg said.
The nanogenerator circulates in the blood until the antibody latches on to a cancer cell, where the cage releases the atom inside. "The range of the alpha particles is very short (50 millions to 80 millions of a metre), and the dose is very small, so as long as it remains circulating, the risks of toxicity are low," he said.
Targeting the generator to the inside of the cancer cells is more effective. Dr Michael McDevitt, lead author of the article, said: "If the atom is sitting on the outside of the cell the alpha particle can travel in any direction and it kills the cell only a fraction of the time. If the generator is inside the cell, every particle will be effective."
Keeping the generator inside the cell also greatly reduces the possibility that the daughter atoms could float off and damage healthy cells, causing side effects.
Dr Scheinberg and his team plan to file an application to begin trials in humans next year, probably on patients with acute myeloid leukaemia. Although the mice seemed to experience no toxic side effects, the true test will be when human trials begin.
Teehee...Actually, I was expecting someone to start joshing about "terrorist cells" etc. :)
Another source of cures for diseases I have always thought was in the fangs of the most deadly snakes. Those creatures have to be good for something besides killing a victim be it a mouse or a man by a bite. I think the venomn must have some curative powers yet to be discovered.
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