For her innovative research on how cannabinoids affect the tumor immune microenvironment in melanoma, University of Colorado Cancer Center member Camille Stewart, MD, has been named to the 2023 cohort of the National Cancer Institute’s Early-Stage Surgeon Scientist Program (ESSP). The National Cancer Institute coordinates the United States National Cancer Program and is part of the National Institutes of Health (NIH).
The ESSP program is designed to train surgeon scientists and retain them in cancer research by supporting a program focused on cancer-related disease and basic/translational research. It brings together surgeon scientists from across the United States in cohorts that are trained together for up to three years.
Opportunity for education
“As I was starting to write up the project descriptions and grants for my cannabinoid research, I realized that I don’t know enough about immunology to thoughtfully attack this subject,” says Stewart, assistant professor of surgical oncology in the CU School of Medicine. “It’s something I’m interested in, and I know there is a gap in our knowledge about how cannabinoids interact with the immune system, but really understanding the nuances of the immune system and its role in malignancy — I just needed education on general immunology to give me the background context to do meaningful work.”
The ESSP award will give her the time and funding to get that education, Stewart says, as well as to look deeper into how cannabis affects the immune system in melanoma patients.
“The NCI gives the cancer center $125,000 a year to cover a part of my salary,” she says. “That protects my time, so I can use it to focus on education and research. My cohort also will come together a couple of times each year to focus on ways we can build up our research careers.”
Do cannabinoids suppress the immune system?
Stewart’s research is based on the hypothesis that because cannabinoids tend to be immunosuppressive, they may impede the ability of the immune system to fight melanoma, a cancer for which immunotherapy treatment is often used. Melanoma patients who use cannabis recreationally, or as a way to manage cancer-related anxiety, nausea, or other side effects, may be unwittingly hindering the efficacy of their treatment.
“Cannabis may be helpful in a wide variety of other conditions, but specifically for melanoma, a robust immune response is important,” Stewart says. “The standard of care treatment for patients with advanced melanoma are drugs called immune checkpoint inhibitors that ramp up your immune system against melanoma cells so that your own body can kill them.”
A previous study showed that people with advanced melanoma who participated in medical cannabis programs in Israel had significantly worse outcomes than advanced melanoma patients who were not part of a cannabis program. Stewart’s research is attempting to find out why that is.
“Melanoma cells with high levels of cannabinoid receptors respond better to immune checkpoint inhibitors,” she says. “My hypothesis is that people who use exogenous cannabinoids like CBD or THC end up decreasing their immune system’s response to the melanoma because it decreases those receptors.”
By comparing patients with melanoma who use cannabinoids to those who don’t, Stewart and her research team will help elucidate the relationship between circulating cannabinoid levels, cannabinoid receptors, and immune cells around the tumor, as well peripheral immune cells. Their findings could inform conversations about cannabinoid use in patients with melanoma and others with tumors responsive to immune checkpoint inhibitors, as well as potentially leading to changes in treatment as well.
As she moves forward in her research and education funded by the ESSP grant, Stewart is proud to have been chosen as part of the 2023 cohort and excited to see her research funded by such a visible program within the NIH.
“The goal of this award is for me to develop into the kind of surgeon-scientist the NCI is hoping to create,” she says. “I also think it’s really great that the federal government sees the value in cannabinoid research.”