A new study in mice has shown that a specific type of T cell plays a key role in the surveillance of subclinical melanoma by preventing the growth and spread of cancer cells that resist eradication — a process known as the cancer-immune equilibrium.1

These cells, tissue-resident memory CD8+ T cells (TRM cells), may be a target for future anticancer immunotherapies, according to study researchers.

In the study, approximately 40% of a group of mice transplanted with cutaneous melanoma cells remained free of macroscopic skin lesions after epicutaneous inoculation; however, those mice that were deficient in TRM cell formation were more susceptible to tumor development.

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“Despite being tumor-free at the macroscopic level, mice frequently harbored melanoma cells in the epidermal layer of the skin long after inoculation, and intravital imaging revealed that these cells were dynamically surveyed by TRM cells,” the researchers explained.

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Further, when tumor-specific TRM cells were depleted, tumor outgrowth occurred in about 20% of mice with occult melanoma, showing that these cells were actively suppressing cancer progression.

“Our results provide unequivocal evidence that effective tumor suppression can result in a dynamic melanoma–immune equilibrium in skin and that such lesions can remain clinically occult for prolonged periods of time, if not indefinitely,” the researchers wrote.


  1. Park SL, Buzzai A, Rautela J, et al. Tissue-resident memory CD8+ T cells promote melanoma-immune equilibrium in skin [published online December 31, 2018]. Nature. doi: 10.1038/s41586-018-0812-9