Thymus hormone restrains aging inflammation and cancer

The thymus is the organ where immune cells mature. By age fifty, active thymic tissue has been largely replaced by fat in most people. With that atrophy comes a decline in the secreted factors the thymus normally produces. Researchers have now identified one such factor: thymulin, a peptide that regulates the activity of myeloid immune cells.

What does thymulin do?

Myeloid cells are part of the innate immune system. With aging, they become pro-inflammatory, producing more signaling molecules such as IL-1α, IL-1β, IL-6, and TNF-α. This chronic low-grade inflammation, sometimes called inflammaging, promotes tumor growth. The study, published in Nature Communications, shows that thymulin suppresses this inflammatory activation by blocking a signaling pathway (NF-κB) that drives it.

In mouse experiments, thymulin also enhanced the activity of T cells that attack tumors. Tumor growth was better controlled and survival improved. Tumors also became more responsive to an existing immunotherapy drug (anti-PD-L1). This effect was age-dependent: it was strongest in older animals.

Could this lead to future treatments?

The researchers used both mouse models and human patient tissue to support their findings. They also employed heterochronic parabiosis, a technique that combines young and old blood, and confirmed that young circulating factors suppressed inflammatory activation in aged myeloid cells. Thymulin appeared to be one of the relevant factors in that young blood.

Whether thymulin can be used therapeutically in humans remains unclear. The results are preliminary and based on animal studies and tissue analyses. Still, the direction is noteworthy: a peptide that both restrains inflammation and improves the response to cancer immunotherapy is, from a longevity perspective, an interesting lead.

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