HOMING IN ON TUMORS
Next-generation cancer therapies will use target-seeking nanoparticles to deliver drugs directly to the site of cancer
Mechanism of breast-cancer gene identified
MONTREAL
Canadian researchers have uncovered how a gene linked to 40 percent of breast cancers works, offering hope for a treatment. The study by McGill University scientists showed that halting the activity of the so-called PTP1b gene in mice predisposed to certain cancers slowed the growth of, and in some cases, prevented tumors. The results were published in Nature Genetics.
"The gene we identified, PTP1b, is known for its role in diabetes and obesity," said Michel Tremblay, study coauthor and director of the McGill Center for Cancer Research. "In this new study, we found that the role of PTP1b in modulating metabolism is equally crucial in the promotion of the proliferation and metastasis of cancer tumors."
In 1999, the same group of researchers found that suppressing the enzyme produced by the gene PTP1b made it possible to cure type 2 diabetes and obesity. A large number of pharmaceutical companies have since developed new inhibitors used in treatments for these diseases.
"Adapting these compounds is all that is needed to attack breast cancer," said Tremblay.
Researchers identify nanoparticle with tumor affinity
CHICAGO
A nanoparticle that homes in on a tumor in the same way that blood platelets swarm to the site of a wound may make it easier to diagnose and treat cancer one day.
The nanoparticle binds to clotted plasma proteins found in tumors, and once in place it causes additional clotting, which generates more plasma proteins, sucking in more nanoparticles, researchers at the Burnham Institute for Medical Research in La Jolla, California, reported.
According to the study published in the Proceedings of the National Academy of Sciences, the scientists hope this "amplified homing mechanism," which mimics the way blood platelets accumulate at the site of an injury to a vessel in the body, will enhance the effectiveness of the molecule as both a drug carrier and an imaging aide.
Cancer researchers and biotechnology companies are already developing next-generation cancer therapies using tiny homing devices, such as the one in this study, to deliver drugs directly to the site of the tumor.
Research has shown that these particles can target the malignant cells with pinpoint precision-a huge improvement over the "carpet-bombing" technique of some current chemotherapy treatments, which damage healthy cells as well the cancerous ones.
But the technology has some limitations. "The efficiency of delivery is generally low," the Burnham Institute researchers, who created the nanoparticle, said. They have not yet tested its efficiency as a drug-delivery system, but they said it clearly has more potential than conventionally acting nanoparticles.
Separately, in preliminary tests on mice, researchers were able to identify tumors measuring a quarter of an inch in diameter that had been injected with this particle. The nanoparticle is made of iron oxide, which is visible under magnetic resonance imaging.
"That would be a very small tumor in a human being," said Erkki Ruoslahti, a cell biologist at the Burnham Institute and lead author of the study.
In the treated mice, the clotting action also choked off a portion of the blood supply to the tumor, although it was not sufficient to slow the tumor's rate of growth.
The researchers were looking at ways to boost the process to the point where it could effectively curtail the cancer's development. "If we can optimize this process, we might be able to achieve a robust therapeutic effect," said Ruoslahti.
Computer no help in spotting breast cancers
WASHINGTON
Computer-aided mammography finds breast cancers no better than the human-read kind, and it prompts more unnecessary biopsies, said a study published April 5 in the New England Journal of Medicine.
"The use of computer-aided detection is associated with reduced accuracy of interpretation of screening mammograms," said the study of 429,345 mammographies in 43 US medical centers, which detected 2,351 cancers between 1998 and 2002. "The increased rate of biopsy with the use of computer-aided detection is not clearly associated with improved detection on invasive breast cancer."
The study is the largest yet to compare the two systems. The computer-assisted machines detected 4.20 cancers for every 1,000 women, while the old method found 4.15 per 1,000. However, the computer-aided detection led to 20-percent more biopsies of suspected tissue that turned out to be negative. On the other hand, the computer assist found less-dangerous cancers than the simple mammography, said Joshua Fenton, of the University of California at Sacramento, one of the study's authors.
"The results of this study will surprise and disappoint most mammographers," said Ferris Hall of the Beth Israel Deaconess Medical Center. "They constitute a substantial hit to this technology," he said.
The equipment from R2 Technology Inc., Kodak, and iCAD Inc. costs some US$150,000. The US Food and Drug Administration authorized the technique in 1998.
Two new drugs prolong lives of renal-cancer patients
WASHINGTON
Two new drugs belonging to a new breed of cancer treatments that inhibit angiogenesis doubled the life expectancy of people afflicted with advanced cases of kidney cancer.
The first drug, sunitinib (Sutent), was developed by US pharmaceutical giant Pfizer and given to cancer patients with previously untreated, metastatic renal cancer in Brazil, Europe, the United States, and Canada during phase-III clinical trials. Half of the 750 patients who took Sutent for six months saw growth of their tumors stymied and they lived almost one year, more than twice as long as patients given interferon alfa.
The second drug, Bayer's sorafenib, was prescribed to 451 patients with renal cancer resistant to standard chemotherapy treatments between November 2003 and March 2005. They survived an average 5.5 months while 452 patients who received a placebo died within 2.8 months.
Results of the trials are published in the New England Journal of Medicine.
The US Food and Drug Administration has given a green light to both sunitinib and sorafenib to treat advanced cancer of the kidney. Previously, only interferon alfa was authorized for use to treat this form of cancer, which is among the most aggressive. But the drug is very toxic, producing severe side effects.
British scientists develop anticancer chicken eggs
LONDON
British researchers have developed genetically modified chickens that can lay eggs containing the proteins required to develop anticancer drugs. The Roslin Institute said it produced five generations of chickens that can produce useful levels of proteins for the development of lifesaving cancer drugs in their eggs.
"One of the characteristics of lots of medical treatments these days is that they're very expensive," Prof. Harry Griffin, the institute's director, was quoted as saying on the BBC web site. "The idea of producing the proteins involved in treatments of flocks of laying hens means they can produce in bulk, they can produce cheaply and indeed the raw material for this production system is quite literally chicken feed."
According to the institute, it has bred about 500 genetically modified birds, though it may take another decade before a medicine is fully developed.
The BBC said on its web site that some of the birds had been modified to lay eggs which contain miR24-an antibody that has the potential to treat skin cancer-and others produce human interferon b-1a-which can be used to stop viruses from replicating in cells. The proteins are secrete
Hormone eyed as cancer treatment
CHICAGO
A hormone that regulates blood pressure has been shown to reduce lung-cancer tumors in mice and may provide a new way to treat this type of malignancy. In experiments on laboratory mice that had been injected with human lung-cancer cells, researchers found that the ones treated with the hormone angiotensin-(1-7) saw their tumors shrink by 30 percent, according to scientists at Wake Forest University School of Medicine.
In contrast, in mice treated with saline, the tumors more than doubled in size over the 28 days of the experiment.
The researchers were alerted to the potential anticancer properties of the hormone by earlier studies which found that rates of lung cancer were lower in people being treated for high blood pressure with angiotensin-converting-enzyme (ACE) inhibitors. These drugs increase levels of angiotensin-(1-7) in the bloodstream. The hormone helps to lower blood pressure by dilating, or enlarging, blood vessels.
The researchers believe the hormone's anticancer effect is due to its reduction of levels of the enzyme cyclooxgenase-2 (COX-2), which stimulates cell growth. "It acts like a dimmer switch on a light," said Patricia Gallagher, one of the authors of the paper, and a researcher at Wake Forest University Baptist Medical Center in Winston Salem, North Carolina.
COX-2 is found at higher levels in 70 to 90 percent of malignant lung tumors.
Researchers in the university's Comprehensive Cancer Center plan to start a small trial of the hormone in lung-cancer patients. "We hope that our clinical trials of angiotensin-(1-7) will lead to the identification of an effective new cancer treatment," said Frank Torti, director of the center.
d into the egg whites, and can then be extracted and purified.
Combo therapy promising for breast cancer
CHICAGO
An experimental new treatment for breast cancer can dramatically shrink, and in some cases eliminate, tumors in mice that have been infected with the disease.
The new therapy involves a combination of chemotherapy drug docetaxel (Taxotere) and a novel compound called JMR-132 that starves the tumor of growth-stimulating hormone. The compound binds to receptors on the tumor, and in so doing blocks the release of the growth hormone.
Tested separately, the drug and the growth-factor inhibitor were extremely effective at shrinking the tumors in mice infected with a hard-to-treat, estrogen-independent form of breast cancer.
On its own, Taxotere reduced the volume of the mice tumors by an average of 74 percent in three weeks. In mice treated with JMR-132, the volume reduction was 63 percent.
Together, the two therapies reduced the volume of the cancerous cells by more than 97 percent. In some cases, when the researchers examined the dead mice, they could not find any cancer cells at all.
What's more, the treatment did not appear to be toxic or trigger any other major side effects in the animals, suggesting it might be well tolerated in humans, the researchers said.
Breast cancer is the most common malignancy among women in the Western world and ranks second as a cause of cancer-related deaths.
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