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Vitamin D can stimulate macrophages to kill lymphoma cells, according to research published in Science Translational Medicine.
The researchers found that activation of the vitamin D signaling pathway activates the antitumor activity of tumor-associated macrophages and improves the efficacy of antibody-dependent cellular cytotoxicity.
The team said these results support the use of vitamin D supplements to boost the effectiveness of existing lymphoma therapies.
Heiko Bruns, PhD, of the University Hospital Erlangen in Germany, and his colleagues knew that vitamin D plays a central role in regulating macrophages, and macrophages often fail to kill tumor cells, partly because of cancer’s ability to evade immune detection.
Previous research has shown that lymphoma patients with low vitamin D levels do not respond to chemotherapy or immunotherapy as well as their peers. And this prompted the recommendation that such patients should take vitamin D supplements before and during treatment.
To uncover the mechanism behind vitamin D’s potential benefits, Dr Bruns and his colleagues analyzed how the vitamin affects macrophages’ ability to fight lymphoma cells.
The researchers found that vitamin D stimulated macrophages to secrete a peptide called cathelicidin, which kills lymphoma cells by damaging their mitochondria.
Macrophages from lymphoma patients were unable to properly metabolize vitamin D. Therefore, the macrophages produced fewer cathelicidin peptides and failed to kill the lymphoma cells.
Treating the macrophages with vitamin D boosted the production of cathelicidin and, in turn, lymphoma cell death.
Similarly, the researchers found that, in healthy individuals with vitamin D deficiency, vitamin D supplements triggered macrophages to release more cathelicidin, making them more effective against cultured lymphoma cells.
Furthermore, treating macrophages from lymphoma patients with both vitamin D and rituximab killed lymphoma cells more effectively than treatment with rituximab alone.
The researchers said these results suggest vitamin D can potentially enhance immunotherapy to more effectively treat lymphoma.
