For the first time, researchers have shown that a protein called SLC significantly inhibits the growth of lung cancer by stimulating an immune response against the disease, according to a new study at UCLA's Jonsson Cancer Center.
Dr. Steven Dubinett and his colleagues at UCLA's Jonsson Cancer Center discovered that SLC, or secondary lymphoid tissue chemokine, eradicated lung cancer in 40 percent of laboratory models and dramatically slowed tumor growth in the remaining models injected with the protein. Laboratory models not exposed to SLC experienced rapid, unrestricted tumor growth.
The findings, published in the May 1 issue of the Journal of Immunology, may serve as a basis for future treatments for lung and other kinds of cancer, said Dubinett, senior author of the study, an associate professor in the Division of Pulmonary and Critical Care Medicine at the UCLA School of Medicine and director of the Pulmonary Immunology Laboratory at the VA Greater Los Angeles Healthcare System.
"We're very encouraged by our results, and they have led us to the early stages of developing a genetic immunotherapy to maximize the cancer-fighting abilities of patients' immune systems," said Dubinett, who specializes in cancer-immunology research.
Dubinett anticipates that his research team may have a therapy available for testing in patients within one to two years.
SLC, found in the lymph nodes, is part of a group of proteins called chemokines. Chemokines have the ability to attract powerful white blood cells called lymphocytes and dendritic cells, which are central to the immune system's ability to recognize cancer and stimulate an attack against tumor cells.
When injected into tumors, SLC attracts lymphocytes and dendritic cells to the tumor, where it is believed that they corner and attack the cancer cells.
Dendritic cells usually are unsuccessful in stimulating the body to fight cancer, even though cancer cells express abnormal proteins and molecules. Scientists believe that cancer can trick the immune system and prevent dendritic cells from responding against tumor cells.
"But after we injected tumors with SLC, we noticed a significant increase in the amount of immune-enhancing proteins and a significant decrease in the number of immune-inhibiting proteins in those tumors," Dubinett said. "This shows that SLC can help prevent important immune cells from being tricked into ignoring invading cancer cells."
Bernard Fox, Ph.D., chief of molecular and tumor immunology at the Earle A. Chiles Research Institute at Providence/Portland Medical Center and an associate professor of molecular microbiology and immunology at Oregon Health Sciences University, said there is "significant reason" to believe that a cancer treatment using SLC would be effective against a variety of cancers in humans.
"The UCLA researchers' discovery that SLC can vigorously stimulate the immune system, combined with existing knowledge about this protein's ability to limit blood vessel formation, makes the protein extremely promising as a basis for new cancer treatments," Fox said. "The work also suggests that SLC could increase the effectiveness of currently available cancer vaccines."
Previous studies have shown that SLC can inhibit angiogenesis, or the formation of new blood vessels. A solid tumor cannot grow beyond the size of a pinhead unless it creates its own blood supply to obtain the oxygen and nutrients necessary for tumor growth and development.
Immune-based therapies are very appealing as cancer treatments because they can target and attack cancer cells while avoiding damage to healthy tissue, Dubinett said. And because immune-based therapies rely on white blood cells, which circulate through all areas of the human body to fight infection and foreign agents, these treatments can be used to fight cancers that originate in almost any area of the body. - By Kambra McConnel
[Contact: Kambra McConnel, Kim Irwin ]