Uncovering the role of XPO6 in nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is a geographically prevalent malignancy, especially in southern China and Southeast Asia, with over 95% of cases in endemic regions linked to Epstein-Barr virus (EBV) infection. Despite advances in screening and chemoradiotherapy, advanced and treatment-resistant NPC remains a significant clinical challenge, characterized by high recurrence rates and limited therapeutic options. While immunotherapy, including anti-PD-1/PD-L1 agents, has been proposed to address this unmet need, responses are often suboptimal, underscoring the need to understand EBV-specific immune evasion mechanisms intrinsic to tumor cells. Our study focuses on Exportin-6 (XPO6), a nuclear export protein identified as a candidate mediator of immune resistance in EBV-positive NPC through a comprehensive CRISPR-Cas9 screen. The screen targeted 19,114 genes in the EBV-positive C666 NPC cell line and the EBV-negative HK1 NPC cell line. Both cell lines were subjected to cytotoxic pressure from NY-ESO-1-specific TCR-engineered T cells, a model that recapitulates antigen-specific antitumor immune responses. Analysis with MAGeCK highlighted XPO6 as an EBV-positive NPC-specific regulator, with its deletion significantly sensitizing tumor cells to T cell-mediated killing. To validate these findings, we generated XPO6 knockout (KO) and overexpression (OE) derivatives of the C666 cell line. Functional co-culture assays confirmed that XPO6 KO markedly reduced NPC cell viability in the presence of TCR-engineered T cells, directly demonstrating enhanced susceptibility to T cell-mediated cytotoxicity. Consistent with this, XPO6 KO C666 cells also exhibited increased secretion of T cell-derived proinflammatory cytokines, including IFN-gamma and TNF-alpha, indicating that XPO6 deletion amplifies the anti-tumor immune response beyond direct cytotoxicity. Conversely, XPO6 OE in C666 cells conferred increased resistance to T cell killing, confirming that XPO6 expression is sufficient to drive immune evasion in EBV-positive NPC. The precise molecular mechanism by which XPO6 mediates these effects remains to be fully elucidated and warrants further investigation. This study identifies XPO6 as a pivotal regulator of immune resistance specifically in EBV-positive NPC. Targeting XPO6 not only enhances tumor cell sensitivity to T cell cytotoxicity but also promotes a more robust T cell cytokine response, highlighting its potential as a therapeutic target to improve immunotherapeutic outcomes. Further exploration of the underlying molecular pathways through which XPO6 enables immune escape will be undertaken in the future.