IL-27 mediates HLA class i up-regulation,which can be inhibited by the IL-6 pathway,in HLA-deficient Small Cell Lung Cancer cells

Background: recently,immunotherapy with anti-pd-1 antibodies has shown clinical benefit in recurrent small cell lung cancer (sclc). since anti-pd-1 re-activates anti-tumor cytotoxic t lymphocyte (ctl) responses,it is crucial to understand the mechanisms regulating hla class i,and pd-l1 expression in hla-negative sclc. here we addressed the role of il-27,a cytokine related to both il-6 and il-12 families. methods: the human sclc cell lines nci-n592,-h69,-h146,-h446 and -h82 were treated in vitro with different cytokines (il-27,ifn-γ,il-6 or a soluble il-6r/il-6 chimera [sil-6r/il-6]) at different time points and analyzed for tyrosine-phosphorylated stat proteins by western blot,for surface molecule expression by immunofluorescence and facs analyses or for specific mrna expression by qrt-pcr. relative quantification of mrnas was calculated by the δδct method. the student's t test was used for the statistical analysis of experimental replicates. results: il-27 triggered stat1/3 phosphorylation and up-regulated the expression of surface hla class i antigen and of tap1 and tap2 mrna in four out of five sclc cell lines tested. the il-27-resistant nci-h146 cells showed up-regulation of hla class i by ifn-γ. ifn-γ also induced expression of pd-l1 in sclc cells,while il-27 was less potent in this respect. il-27 failed to activate stat1/3 phosphorylation in nci-h146 cells,which display a low expression of the il-27ra and gp130 receptor chains. as gp130 is shared in il-27r and il-6r complexes,we assessed its functionality in response to sil-6r/il-6. sil-6r/il-6 failed to trigger stat1/3 signaling in nci-h146 cells,suggesting low gp130 expression or uncoupling from signal transduction. although both sil-6r/il-6 and il-27 triggered stat1/3 phosphorylation,sil-6r/il-6 failed to up-regulate hla class i expression,in relationship to the weak activation of stat1. finally sil-6r/il-6 limited il-27-effects,particularly in nci-h69 cells,in a socs3-independent manner,but did not modify ifn-γ induced hla class i up-regulation. conclusions: in conclusion,il-27 is a potentially interesting cytokine for restoring hla class i expression for sclc combined immunotherapy purposes. however,the concomitant activation of the il-6 pathway may limit the il-27 effect on hla class i induction but did not significantly alter the responsiveness to ifn-γ. © 2017 the author(s).