SACRAMENTO — Dogs are once again showing they deserve the title of man’s best friend. Thanks to some help from canines, researchers from the University of California-Davis Health have found a specific protein in the body that could create more effective immunotherapies. The protein would help trigger the immune system to better respond to and eliminate cancer.
The clinical study involved 21 pet dogs who developed metastatic lung disease from bone or skin cancer. The team treated dogs with the cytokine interleukin-15 (IL-15), which scientists believe benefits immunotherapy. However, IL-15 treatments in humans are sparse because some doses carry high toxicity risks.
“No one previously had administered IL-15 as an inhaled treatment in dogs to deliver it directly to the site of the cancer. We came up with that idea as a means of reducing exposure to the rest of the body, in order to improve the benefit-risk ratio, to improve the immune stimulating effects, and to reduce toxicity,” explains Robert J. Canter, a canine oncologist and chief of the UC Davis division of Surgical Oncology, in a university release.
“In this study, we used interleukin-15 to reinvigorate the immune system to make it recognize the cancer cells that had evaded the immune system and eliminate them.”
Inhaling IL-15 shrank cancerous tumors
Dogs inhaled a mist of IL-15 twice a day. The dosage increased over time to help with effectiveness, and for researchers to determine a safe dose. Within 14 days of inhaling the mist, the dogs’ health began to improve.
The doctors found that giving high amounts of IL-15 helps to ramp up the immune system’s defenses against multiple cancers in dogs. The overall response rate was near 40 percent. The tumors of two dogs shrank dramatically, and one went into remission for over a year.
“The inhaled IL-15 responses that we’ve seen in dogs are better than prior human studies, but clinical benefit is seen in less than half of the dogs. Using IL-15 in people has led to potentially favorable immune responses but has not yielded good tumor responses. This indicates that combining IL-15 with other immunotherapies may result in additive or synergistic responses,” says Robert B. Rebhun, a canine oncologist at UC Davis School of Veterinary Medicine and the associate director of the cancer program in the Center for Companion Animal Health.
The treatment works best along with other medications
The two key findings of the study were that dogs tolerated the IL-15 therapy well and within two weeks, it helped to suppress metastatic cancer. However, the researchers warn that IL-15 alone is not enough to completely eliminate cancer. Rather, they recommend it works best in combination with other cancer treatments.
“All of the canine patients in this study had advanced metastatic cancer, and the majority already had received prior chemotherapy, radiation therapy and, in some cases, immunotherapy. Studies are ongoing now to see whether we can predict which patients might respond to this therapy based on properties of the tumor or the patient’s immune status,” explains Dr. Rebhun.
The findings could also give insight into how the IL-15 treatment will react in humans, and potentially speed up the process of getting an IL-15 therapy as an additive option to chemo or immunotherapy.
The study is published in the Journal for ImmunoTherapy of Cancer.