How a rogue immune signal fuels a rare skin cancer, and how to shut it down

An international team of researchers has discovered how a molecule normally used by the immune system to fight infection is hijacked to help cancer cells grow in cutaneous T-cell lymphoma (CTCL), and identified a way to block it. This work is published on date in Cancer and Metabolism.

A cancer that starts in the skin
CTCL is a rare and often difficult-to-treat cancer that begins when a type of white blood cell, called a T cell, turns malignant and settles in the skin. As the disease advances, it can spread through the blood and become life-threatening. Doctors have long noticed that patients with CTCL tend to have unusually high levels of a signaling molecule called Interleukin-17A, or IL-17A, but exactly what that molecule was doing to the tumor remained a mystery.

Turning a fuel gauge into a cancer’s growth switch
IL-17A is best known as an alarm signal: it helps rally the immune system against bacteria and fungi. The new study, led by co-corresponding authors Priyanka Sharma (IPBS) and Rahul Purwar (IIT Bombay), shows that in CTCL, malignant T cells carry unusually high numbers of the receptor that “listens” for IL-17A. When the malignant cells receive that signal, they respond by revving up their own internal power plants: the mitochondria.

Specifically, the team found that IL-17A boosts the activity of a molecular machine called Electron Transport Chain (ETC) complex I, one of the engines mitochondria use to generate energy. With this engine running harder, the cancer cells produce more energy currency (ATP) and gain a survival advantage, allowing them to proliferate more readily and resist cell death.

The researchers confirmed this chain of events using skin and blood samples donated by CTCL patients, several malignant T-cell lines grown in the laboratory, and a combination of imaging, proteomics (a technique that measures thousands of proteins at once), and biochemical assays, building a consistent picture across multiple independent experiments.

Switching off the engine slows the cancer down
Having pinpointed ETC complex I as the link between IL-17A and tumor growth, the team tested whether disabling it could undercut the cancer’s advantage. Using both a chemical inhibitor and a genetic technique that silences the gene encoding a complex I component, they found that blocking this mitochondrial engine curbed the cancer cells’ energy production and slowed their proliferation, while sparing healthy T cells at the doses tested.

Why it matters
CTCL remains hard to treat, and existing therapies often lose effectiveness over time as tumors adapt. By revealing that malignant T cells depend on this IL-17A-driven metabolic engine to thrive, the study points to a new therapeutic strategy: targeting the cancer’s energy production rather than only its immune signaling. The authors suggest that combining ETC complex I–targeting approaches with existing CTCL treatments could offer a new way to outmaneuver the tumor’s adaptability.

The researchers caution that this is a laboratory-based study and that further work, including trials in larger and more diverse patient groups, will be needed before any such strategy can be tested in the clinic. They also note that IL-17A’s role in the body is complex, since it also affects healthy immune cells, meaning any future therapy would need to target the tumor’s vulnerability specifically without disrupting normal immune defenses.

About the collaboration
This work reflects an international collaboration between IPBS (CNRS, Université de Toulouse) in France, IIT Bombay’s Department of Biosciences and Bioengineering, the Medical Oncology department at Tata Memorial Hospital in Mumbai, India, and the Robert Bosch Center for Tumor Diseases in Stuttgart, Germany.

Reference: Attrish D, Dhamija B, Mukherjee D, Sawant V, Marathe S, Saul D, Basu M, Banik A, Sharma N, Shet T, Jain H, Kosinsky RL, Sharma P*, Purwar R*. (2026) Interleukin-17A regulates malignant T-cell proliferation via Electron Transport Chain complex I. Cancer Metab doi.org/10.1186/s40170-026-00453-2

Contacts: 
IPBS Communication office | Communication@ipbs.fr
Researcher | Priyanka Sharma | priyanka.sharma@ipbs.fr