NEW HAVEN, Conn. -- Researchers from the U.S., Australia, and Sweden have combined forces to isolate the gene for basal cell carcinoma of the skin, the most common human cancer. The findings, published in the June 14 issue of the journal Cell, could lead to a skin cream that would cure the disease, and to genetic testing for susceptibility to skin cancer.
Approximately one million cases of basal cell carcinoma occur each year, and its incidence is on the rise. The new gene, called PTC, is essential for keeping skin cells under control. "Genetic mutation of PTC is the key step in development of skin cancer,2 said Allen Bale, M.D., senior author of the Cell paper and director of the Cancer Genetics Program at the Yale Cancer Center.
The discovery paves the way for novel approaches to preventing and treating basal cell carcinoma, according to David J. Leffell, M.D., associate professor of dermatology at the Yale School of Medicine and a co-author of the report. 3Although still several years away, it1s not unreasonable to imagine an ointment that, when applied to the skin, may control the growth of the cancer,2 Leffell said. 3Because skin cancers occur externally rather than in internal organs, a dose of a medication that can replace the function of the faulty gene could be applied directly to the cancer while minimizing side effects.2
The search for the gene began with studies of a rare hereditary disorder, nevoid basal cell carcinoma syndrome (NBCCS). People with this syndrome often develop thousands of skin cancers and may also have birth defects and childhood brain tumors. In 1992, Bale mapped the NBCCS gene to human chromosome 9, and over the past 4 years he and his collaborators sorted through 40 genes from this region. In May, Bale's group reported isolation of PTC, a human gene similar to a previously reported fruit fly gene. "Nobody had a clue that this gene had anything to do with human cancer, but some of the features in fruit flies were strangely similar to the birth defects in NBCCS", said Bale.
The researchers found that individuals with NBCCS are born with a mutation of PTC in all of their cells. Further investigation revealed the same mutation in sporadic (noninherited) tumors, which account for the vast majority of basal cell carcinomas. In those tumors, the mutation was often caused by exposure to ultraviolet light.
Although NBCCS is rare, milder forms of genetic predisposition to skin cancer may be fairly common. Bale suggests genetic screening for those who have had more than two basal cell carcinomas to determine if they are genetically predisposed. 3Through a simple blood test, we can identify people who are cancer-prone,2 he noted. 3For those who are, more aggressive monitoring and preventive measures such as staying out of the sun and using sunscreen can be applied.2
Collaborating scientists included Michael Dean, Ph.D. from the National Cancer Institute in Frederick, Maryland, Brandon Wainwright, Ph.D. and Georgia Chenevix-Trench, Ph.D. from the University of Queensland and the Queensland Institute of Medical Research in Brisbane, Australia, and Rune Toftgard, Ph.D. from the Karolinska Institute in Huddinge, Sweden.