Skin cancer is among the most common cancers worldwide, and a new study from the University of Dundee, Queen Mary University of London, and the Wellcome Sanger Institute has identified a concerning molecular link between a widely used immunosuppressive drug and the development of cutaneous squamous cell carcinoma, one of the most frequently diagnosed forms of skin cancer. The findings, published in Nature Communications, have direct implications for millions of patients who take azathioprine to manage inflammatory and autoimmune conditions.
What Azathioprine Is and Why It Raises Skin Cancer Concerns
Azathioprine is used to treat a range of serious conditions including inflammatory bowel disease, rheumatoid arthritis, and vasculitis, and is also prescribed to prevent organ rejection in transplant patients. Its widespread use reflects its effectiveness in managing conditions that, left untreated, can be life threatening.
It has been known for some time that azathioprine increases photosensitivity to UVA light, which raised early concerns about its potential role in skin cancer development. This new study goes further by identifying a specific molecular fingerprint, a mutational signature called Signature 32, that appears in skin cancer tumors and correlates directly with duration of azathioprine use. That fingerprint provides a direct biological link between the drug and cutaneous squamous cell carcinoma, moving beyond epidemiological association to molecular evidence.
How the Skin Cancer Mutational Signature Study Was Conducted
The research team performed mutational signature analysis on cutaneous squamous cell carcinoma tumors from 37 patients, many of whom had a history of azathioprine use. By analyzing the distinct patterns of DNA mutations left behind by different carcinogens, the researchers identified Signature 32 as a novel mutational pattern correlating specifically with long term azathioprine therapy.
Different carcinogens leave different mutational signatures in skin cancer tissue, and studying these signatures allows researchers to work backward from the tumor to determine what environmental or pharmaceutical factors may have contributed to its development. Professor Gareth Inman of the Cancer Research UK Beatson Institute noted that while patient numbers were small and findings should be verified in a larger independent cohort, the molecular study provides a strong case for an association between Signature 32 and long term azathioprine use.
What This Means for Skin Cancer Risk in Patients on Azathioprine
The research team was careful to clarify that their findings are not a call to discontinue azathioprine. As Professor Charlotte Proby of the University of Dundee stated, the risks of any medication must be weighed against its benefits, particularly when the drug is managing a potentially life threatening condition. What the findings do support is a more rigorous approach to skin cancer surveillance and sun protection for patients on azathioprine.
Proby recommended that all physicians counsel patients on azathioprine about year round UVA avoidance, including consistent use of high protection sunscreen, physical barriers such as hats and long sleeved clothing, and regular dermatological monitoring. Sunscreen with at least SPF 15 and four star UVA rating is advised for any exposed skin. Early diagnosis and prompt lesion removal should be standard components of routine patient management.
The Broader Implications for Skin Cancer Research and Treatment
Beyond the azathioprine link, the study also mapped the broader molecular landscape of cutaneous squamous cell carcinoma and identified potential therapeutic targets that may be developed into future skin cancer treatment approaches. Cutaneous squamous cell carcinoma accounts for more than 40,000 new diagnoses annually in the United Kingdom alone, with substantial health and economic consequences.
Understanding the mutational drivers of skin cancer at the molecular level is critical to developing more targeted and effective therapies. As researchers continue to refine mutational signature analysis as a diagnostic and investigative tool, studies like this one will become increasingly valuable for both clinical practice and drug development. For patients on long term immunosuppressive therapy, the message is clear: skin cancer surveillance and consistent sun protection are not optional precautions but essential components of care.
To read more about oncology research and clinical advances, visit the FOMAT blog. FOMAT conducts oncology clinical trials at sites across the United States. To learn more about active studies, visit FOMAT’s patient studies page.
For the full source, see the original publication in Nature Communications.