BETHESDA, Md.— A small protein known as interleukin-7 (IL-7) that stimulates the immune system in cancer patients could have a wide range of clinical implications, according to a study recently published by National Cancer Institute (NCI) researchers in The Journal of Experimental Medicine.
Finding that treating cancer patients with IL-7 leads to an increase in lymphocytes, which are key to the production of effective immune responses in the body, the researchers believe IL-7 could be used to treat other conditions such as the side effects of chemotherapy and HIV that often deplete the body of lymphocytes, says Dr. Claude Sportes, one of the study's lead authors. The protein could also be used to boost immune function in individuals older than 45 who experience a diminished capacity to regenerate lymphocytes, he adds.
"I don't want people to think we have found the fountain of youth, but these findings may lead to a large number of clinical applications for IL-7," Sportes says. "NCI has long been at the forefront of the clinical development of IL-7, and we plan to continue exploring the biologic properties of IL-7 in humans and to define its clinical applications."
Knowing from previous research that IL-7 helps restore T cell populations in animal models, the researchers set out to assess the effects of IL-7 treatment in humans. The researchers administered a laboratory-generated form of IL-7 (rhIL-7) to 16 cancer patients with solid tumors, who had not responded to standard treatment, under their skin every other day for 14 days. The patients, whose ages ranged from 20 to 71 years, each received a total of eight doses of rhIL-7.
The researchers found an increase in the total number of lymphocytes in the patient's bloodstreams, particularly in older individuals. These higher lymphocyte numbers remained elevated for up to six weeks after treatment ended. Treatment with rhIL-7 also had a notable effect on the number of memory CD4+ T cells, which play a key role in the body's defense against tumors and chronic, persistent viral infections.
In addition to potential clinical applications in depressed immune system disorders and diseases and restoration of diminished lymphocyte function in older adults, IL-7 could also be used to enhance immune responses to conventional vaccines, cancer vaccines or other forms of cancer immunotherapy, Sportes says. The researchers' next study will focus on IL-7's impact on increased immune response to vaccines, he says.
"Many of these potential uses may never pan out," Sportes says. "The findings are still very much in their infancy, but what we know of IL-7's properties lead us to believe it may have multiple uses. Potential clinical applications need to be tested systematically in order to define the field of clinical application for the drug. Our results are only a first step in a long process."
The study was conducted by researchers in NCI's Experimental Transplantation and Immunology and Pediatric Oncology branches, as well as the NIH Clinical Center, Cytheris Inc. in Rockville, Md. and The Cancer Center at Hackensack University Medical Center in New Jersey.