STAT1 and neoplasm: Based on numerous reports and our results, it can be speculated that CAR-NK cells secrete a large amount of IFN-γ after binding to target cells, and tumor cells react quickly to IFN-γ secreted by activated NK cells, which binds to interferon receptors and then activates JAK1, JAK2 and STAT1 in tumor cells, in turn upregulating the expression of PD-L1 on tumor cells (Figure 6A).