Tofacitinib overcomes an IFNγ‐induced decrease in NK cell‐mediated cytotoxicity via the regulation of immune‐related molecules in LC‐2/ad

BACKGROUND: Immune checkpoint inhibitors targeting the programmed cell death‐1 (PD‐1)/PD‐1 ligand 1 (PD‐L1) axis have shown promising results in patients with nonsmall cell lung cancer (NSCLC). One major PD‐L1 inducer is IFNγ, which is secreted by T cells and NK cells. Importantly, IFNγ‐induced PD‐L1 is one of the major mechanisms by which cancer cells escape host immunity. METHODS: Here, we found that the NSCLC cell line, LC‐2/ad, has a unique character; the PD‐L1 expression in these cells is up‐regulated by both IFNγ and epidermal growth factor (EGF). RESULTS: Comparative analysis of the cell signaling pathway showed that IFNγ activates STAT1 signaling, while EGF activates AKT, MAPK, and ribosomal protein S6 kinase in LC‐2/ad cells. IFNγ‐induced PD‐L1, but not EGF‐induced PD‐L1, was clearly blocked by the JAK‐STAT inhibitor tofacitinib. Interestingly, IFNγ decreased the expression of NK cell‐activating ligands while increasing the expression of MHC class I molecules, resulting in a phenotype that can easily escape from NK cells, theoretically. Finally, we showed that IFNγ stimuli attenuated NK cell‐mediated cytotoxicity in LC‐2/ad cells, which was, however, blocked by tofacitinib. CONCLUSIONS: Taken together, our study shows that tofacitinib blocks the IFNγ‐induced transformation from an NK cell‐sensitive phenotype to an NK cell‐resistant one in IFNγ‐reacted LC‐2/ad cells, thereby implicating that tofacitinib may be a promising agent to overcome IFNγ‐induced tumor immune escape, although it may be adapted to the limited number of NSCLC patients.