IFNγ-induced PD-L1 expression is JAK2 but not JAK1 dependent and its inhibition enhances NK-cetuximab mediated ADCC of HNSCC cells

Abstract

Programmed death ligand 1 (PD-L1) is an immunosup-pressive molecule expressed by many cancer types, including a large proportion of head and neck cancers (HNC), and ligation of its receptor, programmed death 1 (PD-1), induces exhaustion of effector T cells. It has been shown that interferon gamma (IFNg) induces PD-L1 expression in many cancer types including glioblastoma, melanoma, lung and kidney cancer. Importantly, the sti-muli and mechanism for PD-L1 upregulation in HNC cells are not well characterized. IFNg signals through Janus Kinase 1/2 (JAK1/2) heterodimer complex and mediates signal transducer and activator of transcription 1 (STAT1) phosphorylation, leading to type I cytokine expression, upregulation of antigen presentation, and tumor cell recognition by cytolytic T lymphocytes (CTL). We investigated basal PD-L1 expression and the mechan-ism by which IFNg signaling upregulates PD-L1 in HNC cells including dependence on JAK/STAT pathway. We observed that IFNg signaling increased PD-L1 expression in a JAK2 but not JAK1 dependent fashion. In addition, interferon alpha (IFNa), which signals via JAK1/TYK2 did not upregulate PD-L1 expression while still upregu-lated HLA class I. Specific JAK2 inhibition downregulated NK cell-derived IFNg induced PD-L1 expression and enhanced cetuximab mediated ADCC. Our data suggest a crucial role for JAK2/STAT1 in IFNg mediated PD-L1 upregulation. JAK2 inhibition provides a promising strat-egy to increase tumor cell lysis through maintaining HLA class I while suppressing tumor cell expressed PD-L1 in combination with anti-EGFR cetuximab therapy.