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S.A. patient study promising
By Don Finley - Express-News : March 22, 2010
In a small study involving San Antonio patients, a team of researchers proved it's possible to trick cancer genes into switching themselves off.
The trick involves using tiny strands of material known as small-interfering RNA, or siRNA, which tells genes to stop making proteins. These siRNAs appear naturally in the body to tell healthy cells to stop growing.
For years, scientists have been trying to find effective treatments for cancer — which is the uncontrolled growth of cells from abnormal genes — using the technique. But they have had limited success in getting siRNAs targeting specific cancer genes into the tumor without being destroyed by the immune system.
In the latest technology, developed by researchers at the California Institute of Technology, the strands were placed in protective nanoparticles covered with transferrin, a material that is absorbed into cells.
Fifteen patients with different types of cancers, most of them from San Antonio, were injected with the nanoparticles. In biopsies of skin cancers, it was found that the particles not only reached and penetrated the cancer cells, but they interfered with the correct gene, called RRM2, which the cells need to multiply.
The results were published online Sunday in the journal Nature.
“It's encouraging,” said co-author Dr. Anthony Tolcher, director of clinical research at South Texas Accelerated Research Therapeutics in San Antonio. “We're showing that you can do it. And now it's really the evolutionary process of can you make it better? Can you turn off different (cancer) genes? That's what the future holds, but it's very preliminary.”
The study was designed only to show it was safe and could work. And not all patients benefited from the treatment.
While most targeted cancer treatments aim for the protein produced by the faulty gene, this method attacks messenger RNA (mRNA), which reads the instructions in genes and sets in motion the manufacture of the protein it makes.
“That means every protein now is druggable because its inhibition is accomplished by destroying the mRNA,” said lead author Mark Davis, professor of chemical engineering at Caltech, who developed the nanoparticle technology. “And we can go after mRNAs in a very designed way given all the genomic data that are and will become available.”
Tolcher said his lab, which specializes in the earliest human studies of new cancer treatment, probably won't be involved in the research as it advances into more patients.
“There's a long way to go, but it's a very promising technology if you can knock down specific genes, and personalize it to an individual's cancer,” Tolcher said. “Because one person's lung cancer might have completely different genes that are abnormal than another person's. Yet they both have lung cancer.”
Other Texas researchers are also studying the use of RNA interference in treating or preventing HIV and other infectious diseases.