STAT3 and prostate cancer: And in castration-resistant prostate cancer cells (CRPC), IL-6 knockdown would lead to the low expression of related proteins in the JAK/STAT3 pathway, which could down-regulate PD-L1 in CRPC cells and reduce its binding to PD-1 on the surface of NK cells, thus affecting the content of NK cells in the tumor microenvironment (49).