Cierna et al. (2021) found that decreased levels of circulating IL-15 suggested PD-L1 overexpression in tumors of primary breast cancer patients and poor prognosis. Krizia et al. (Cierna et al., 2021) reported that higher IL-15 levels would lead to better outcomes in prostate cancer, which is consistent with our findings. Margolin et al. (2018) recently found that the injection of IL-15N72D: IL-15RαSu/IgG1 Fc complex could reduce cancer growth, induce NK cell expansion and improve survival in patients with incurable advanced melanoma, renal cell, non-small cell lung, and head and neck cancer. Here, IL15 is linked to head and neck cancer.