Abstract
The immune checkpoint programmed death ligand‐1 (PD‐L1) is highly expressed in cancer cells, including ovarian cancer (OC) cells. High PD‐L1 expression in ovarian cancer correlates with poor prognosis, but the mechanisms that regulate the PD‐L1 expression in OC remain poorly understood. We have recently shown that IFNγ induces the PD‐L1 expression in OC cells, resulting in their increased proliferation and invasion. Here, we show that the IFNγ‐induced PD‐L1 expression in OC cells is associated with increased levels of STAT1, Tyr‐701 pSTAT1 and Ser‐727 pSTAT1 in OC cells. JAK1 and STAT1 suppression significantly decreases the IFNγ‐induced PD‐L1 mRNA and protein levels in OC cells. In addition, IRF1 suppression significantly decreases the IFNγ‐induced gene and protein levels of PD‐L1, indicating that the IFNγ‐induced PD‐L1 expression in OC cells is dependent on IRF1 signaling. Chromatin immunoprecipitation data demonstrate that IFNγ induces occupancy of STAT1, Ser‐727 pSTAT1 and IRF1 at STAT1 and IRF1 binding sites in human PD‐L1 promoter. Together, these results show that the IFNγ‐induced PD‐L1 expression in OC cells is regulated by IRF1/JAK1/STAT1 signaling, and suggest that targeting the IRF1/JAK1/STAT1 pathway may provide leverage to regulate the PD‐L1 levels in ovarian cancer.
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