McGill researcher makes breakthrough in Kaposi’s sarcoma

A hidden genetic defect may explain why some people develop Kaposi’s sarcoma even though their immune systems appear to be healthy, according to research by a Montreal team.

The rare cancer is caused by human herpesvirus 8 (HHV-8), which primarily affects people with weakened immune systems, such as those with HIV or undergoing immunosuppressive therapy.

The virus belongs to the same family as those that cause cold sores or chickenpox.

For reasons that are still poorly understood, it can sometimes also affect older adults with no apparent immune problems, particularly men of Mediterranean, Middle Eastern or Eastern European descent, as well as certain populations in Central Asia, South America and Inuit communities.

“In these cases, it has always remained a mystery,” said Dr. Donald Vinh, a microbiologist-infectious disease specialist and scientist with the Infectious Diseases and Global Health Immunity Program at the Research Institute of the McGill University Health Centre (RI-MUHC). “Why are certain people at risk, yet without other recognizable epidemiological risk factors?”

The Montreal team’s research uncovered the first known human case of RIG-I protein deficiency — a key component of natural antiviral immunity.

Their work shows that the abnormality, caused by a mutation in the DDX58 gene, prevents the body from detecting the virus responsible for the disease, therefore making it unable to control the infection.

The discovery could lead to more targeted and potentially effective treatments for the cancer, and possibly other diseases or cancers caused by viruses, the researchers noted.

The genetic defect, Dr. Vinh explained, does more than just weaken the immune response: it also allows the virus to hide within cells and reprogram them so they can survive and multiply, which promotes the development of cancer.

“We’ve discovered a new gene that allows this virus, at least in one human patient, to become cancerous,” Dr. Vinh said. “This helps us understand which molecular pathway might allow this virus to have its dangerous consequences.”

Kaposi’s sarcoma remains a rare cancer, he continued, meaning that the therapies available to treat it are less well-developed than others, such as breast or lung cancer.

Interferon alpha, an immunotherapy, is sometimes used, but with mixed results.

The new study suggests that other immunotherapies, such as interferon beta and potentially interferon omega, could be more effective and better tolerated.

“It has been shown that interferon beta is more effective than interferon alpha,” said Dr. Vinh. “It not only suppresses viral production but also the program that leads to cancerous changes. So, we hope this could be the beginning of a change in the treatment of this cancer.”

The findings of the study were published in the Journal of Allergy and Clinical Immunology.

This report by The Canadian Press was first published in French on May 14, 2026.