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News
A new study in Nature Communications reveals that thymulin — a hormone produced by the thymus — may be a missing link between aging, chronic inflammation, and poor cancer immunotherapy response. Researchers found that older mice had worse tumor outcomes and weaker responses to checkpoint inhibitors, but thymulin treatment reversed inflammaging and boosted survival. The findings could reshape how preclinical immunotherapy studies are designed.
A surgical oncologist's frustration over seven non-responding clinical trial patients sparked a discovery that could change how we think about aging and cancer immunotherapy. Dr. Fumito Ito of USC Keck School of Medicine found that older mice showed far more aggressive tumor growth and weaker responses to checkpoint inhibitors (anti-PD-1/PD-L1 therapy) compared to younger mice — a difference driven by age-related myeloid cell inflammation fueled by cytokines IL-1a, IL-1b, IL-6, and TNF-α.
The culprit? A decline in thymulin, a hormone produced by the thymus gland that shrinks with age. Using parabiosis and bone marrow chimera experiments, Ito's team showed that young circulating factors could suppress aged myeloid inflammation — and thymulin was identified as a key suppressor. Restoring thymulin in older mice improved tumor immunity, overall survival, and responsiveness to immunotherapy.
Key Takeaways:
Why it matters: Most cancer immunotherapy trials are informed by preclinical studies using young mice — but most cancer patients are older. This research highlights a critical gap and positions thymulin as a potential therapeutic target to improve immunotherapy outcomes in aging populations.
