Irradiation Mediates IFNα and CXCL9 Expression in Non-Small Cell Lung Cancer to Stimulate CD8+ T Cells Activity and Migration toward Tumors

Abstract

Irradiation-broken DNA fragments increase type I interferon and chemokines secretion in tumor cells. Since radiotherapy may augment tumor immunotherapy, we hypothesize that the chemokines increased by irradiation could recruit CD8⁺ T cells to suppress tumor proliferation. This study intended to unveil the secreted factors activating and recruiting CD8⁺ T cells in non-small-cell lung cancer (NSCLC). EGFR-positive A549 was selected and treated by X-irradiation (IR) to identify the overexpression of chemokines associated to CD8⁺ T cell cytotoxicity and recruitment. A transwell assay with Alexa 488-labeled CD8⁺ T cells was used to evaluate CD8⁺ T cell motility in vitro. A nuclear imaging platform by In¹¹¹-labeled nivolumab was used to track CD8⁺ T cells homing to tumors in vivo. The activation markers <i>GZMB</i>, <i>PRF-1</i>, and <i>IFNγ</i>, migration marker <i>CD183</i> (CXCR3), and inhibitory marker <i>CD274</i> (PD-1), were measured and compared in CD8⁺ T cells with A549 co-cultured, chemokines treated, and patients with late-stage lung cancer. We found that IR not only suppressed A549 proliferation but also induced <i>IFNα</i> and <i>CXCL9</i> expression (<i>p</i> < 0.05). <i>IFNα</i> majorly increased <i>IFNγ</i> levels in CD8⁺ T cells (<i>p</i> < 0.05) and synergistically with <i>CXCL9</i> enhanced CD8⁺ T cell migration in vitro (<i>p</i> < 0.05). We found that CXCR3 and PD-1 were down-regulated and up-regulated, respectively, in the peripheral blood CD8⁺ T cells in patients with lung cancer (n = 4 vs. healthy n = 3, both <i>p</i> < 0.05), which exhibited reduction of cell motility (<i>p</i> < 0.05). The in vivo nuclear imaging data indicated highly CD8⁺ T cells migrated to A549-induced tumors. In addition, we demonstrated that healthy PBMCs significantly suppressed the parallel tumor growth (<i>p</i> < 0.05) and the radioresistant tumor growth in the tumor xenograft mice (<i>p</i> < 0.05), but PBMCs from patients with lung cancer had lost the anti-tumor capacity. We demonstrated that IR induced <i>IFNα</i> and <i>CXCL9</i> expression in A549 cells, leading to CD8⁺ T cell migration. This study unveiled a potential mechanism for radiotherapy to activate and recruit CD8⁺ T cells to suppress lung tumors.