Meanwhile, other scientists say that an experimental drug designed to put the molecular brakes on the growth of tumor-feeding blood vessels shows promise in people with brain cancer.
While the work is still in its earliest stages, the approaches show great promise, says William J. Nelson, MD, a professor of oncology at Johns Hopkins in Baltimore who was not involved with the research.
"We're just beginning to explore their full potential," he tells WebMD.
The research was discussed at the annual meeting of the American Association for Cancer Research.
'Smart Bomb' Against Prostate Cancer
Researchers at Columbia University say they have designed a novel viral-based gene therapy that blasts through the body, targeting both primary and distant tumor cells, while leaving normal cells unscathed.
Once at its target, the virus replicates and produces a massive amount of a cancer-killing compound, says researcher Paul B. Fisher, PhD, a professor of clinical pathology.
Early results suggest the approach is working. When injected into 15 mice with prostate cancer that resisted normal cancer drugs, the treatment eradicated all signs of cancer, essentially producing a cure.
An earlier version of the therapy worked "fairly well" in a study of people with multiple solid tumors, Fisher says.
There were signs that the cancer cells were committing cell suicide, and five of the eight people studied are still alive, he tells WebMD.
The improved treatment appears to be "a much more intelligent smart bomb" that can only replicate in tumor cells, Fisher says. The treatment also worked in animals with skin and breast cancer.
Nelson comments, "The idea of harnessing the innate power of viruses to infect cells, reproduce many times and destroy the cancer cell in the process and then move on to the next cancer cell is a great therapeutic goal."
Gene Therapy Targets Lung Cancer
Researchers at the University of Texas M.D. Anderson Cancer Center in Houston are trying a different tactic, packaging a cancer-suppressing gene in a fat-based coating for protection.
So far, they have successfully delivered the cancer-killing gene into the tumors of 13 people with advanced lung cancer.
In the three people in whom biopsies were performed before and after treatment, "we saw expression of the infected gene and signs the tumor [had stopped growing]," says researcher Charles Lu, MD, associate professor in the department of thoracic, head and neck medical oncology.
They lived an average of 14.6 months, which compares favorably to the typical seven-month average for people with this stage of disease, Lu says. "Still, it is way too early to draw conclusions," he tells WebMD.
Lu says the work built on the observation that a copy of the cancer-killing gene, FUS1, is lost in people with lung cancer.
"By reinjecting the gene that was lost, we get tumor suppression again," he says.
The only significant side effect so far has been fever, which is treatable, he says.
Lung cancer is the leading cause of cancer death in the U.S., causing 160,000 deaths annually, according to the American Cancer Society.
Experimental Drug Shows Promise in Brain Cancer
In other research presented at the meeting, an experimental pill showed promise in treating one of the deadliest types of brain cancer.
The pill blocks the growth of new blood vessels that feed tumors. By eliminating the flow of blood to tumors, the idea is to prevent the tumor from growing.
People with the cancer, glioblastoma, "secrete a lot of growth factors that make blood vessels that feed the tumor, so this is an attractive target," says researcher Tracy Batchelor, MD, chief of neuro-oncology at Massachusetts General Hospital in Boston.
Within 24 hours, "leaky blood vessels began to normalize," Batchelor tells WebMD. Also, swelling in the brain, a big problem in such patients, was alleviated.
But by one month later, abnormal blood vessel growth resumed, imaging studies showed.Still, tumors shrank by 50% or more in half of the participants, and the average time to tumor regrowth was 111 days. In contrast, only about one in 10 people with glioblastoma given traditional treatment typically have tumor shrinkage, and the average time to progression is usually 63 days, Batchelor says.
"We all recognize that what we need to do now is combine this therapy with other types of treatments, either existing or to be developed, and to deliver these drug combinations during the window we have identified," Batchelor says. "This might help us manage patients much more effectively."
He says the researchers hope to start a larger trial in which participants get either AZD2171 plus standard chemotherapy or chemo alone within the year.