Radiotherapy enhances CXCR3(high) CD8(+) T cells activation through inducing IFNγ-mediated ICAM-1 expression in lung cancer cells

Abstract

Abstract Radiotherapy (RT) not only damages tumors but also induces interferon (IFN) expression in tumors. IFNs-mediate PD-L1 exhausts CD8+ T cells but which also directly impact tumor cells and potentially activate anti-tumor immune surveillance. Little is known about the contradictory mechanism of IFNs in regulating CD8+ T-mediated anti-tumor activity in lung cancer. This study found that RT significantly improved PBMCs- and splenocytes-mediated inhibition of tumor cell viability. Meanwhile, RT induced IFNs and CXCL9/10 expression in the RT-treated lung cancer cells. Specifically, RT- and IFNγ-pretreated A549 significantly activated CD8+ T cells, resulting in significant inhibition of A549 colony formation. RNAseq results revealed that IFNγ induced PD-L1 and ICAM-1, whereas PD-L1 knockdown activated CD8+ T cells but ICAM-1 knockdown diminished CD8+ T cells activation. We further demonstrated that CXCR3 decreased in the CD8+ T cells of patients with lung cancer that expressed lower reactivation as co-cultured with A549 cells. In addition, inhibitors targeting CXCR3 and LFA-1 in CD8+ T cells significantly diminished splenocytes-mediated anti-LL/2shPdl1 colony formation. We validated that RT suppressed lung cancer and overexpress PD-L1 and ICAM-1, which exhibited opposite roles in regulating CD8+ T cell activity. CXCR3highCD8+ T cells levels with highly CXCL10 in healthy volunteers recognized ICAM-1 in RT- and IFNγ-treated A549 for further activating CD8+ T cells, but CXCR3lowCD8+ T cells with low CXCL10 in patients with lung cancer were exhausted by PD-L1 dominantly. This study clarified the possible mechanisms of RT and IFNs in regulating CD8+ T cell activation in lung cancer.