Recently I've stumbled across an interesting video showing Natural Killer cells (NK cells) destroying cancer cells in their early stages. Since I've never heard whether there was any use of these cells in preventing cancer from spreading, I researched a few enquiring articles.
It claims that NK cells are safe for humans since as lymphocytes they're part of the innate immune system. They have the ability to deflect tumour cells without prior exposure to cell antigens in comparison to cytotoxic (means toxic to living cells - which also NK cells are) T cells which need this primary contact (T cells are already used in immunotherapy). Unfortunately, there are many ways cells escape the surveillance of the NK cells, and with highly invasive cancer cells they often don't stand a chance and what's more, they can be reprogrammed to promote metastatic growth. How cancer cells survive immune selection and avoid NK cell cytotoxicity remains unanswered and only further research might efficient immunotherapies.
link to the articles:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8920322/
https://www.immunology.org/public-information/bitesized-immunology/cells/natural-killer-cells
and to the video:
https://www.instagram.com/reel/CzxPgJmoVEZ/?igshid=MzRlODBiNWFlZA==