Background: Nasopharyngeal carcinoma (NPC) is a highly malignant epithelial cancer linked to Epstein–Barr virus (EBV) infection. Tumors are characterized by a lymphomononuclear infiltrate and the number of natural killer (NK) cells in tumors appears to be of prognostic significance. Standard treatment for NPC in adolescents and young adults consists of induction chemotherapy followed by radiochemotherapy. Though survival rates are above 80%, the majority of patients suffer from long-term side-effects, mainly related to radiotherapy. The addition of immunotherapy to induction chemotherapy could improve tumor response. Methods: We have investigated the killing of NPC cells by NK cells in the context of chemotherapy, using a panel of three nasopharyngeal carcinoma cell lines and a patient-derived xenograft. Cytotoxicity was measured using the calcein-release assay, while the contribution of different checkpoints and signaling pathways to killing was studied by siRNA-mediated gene silencing and chemical inhibitors. Results: Chemotherapeutics cisplatin, 5-fluorouracil and gemcitabine sensitized NPC cells to killing by NK cells. Chemotherapeutics led to upregulation of PD-1 in NK cells and PD-L1 in NPC cells via NF-κB. Inhibition of the PD-L1/PD-1 checkpoint by an anti-PD-1 antibody or siRNA increased NK-cell cytotoxicity towards NPC cells. Conclusion: The addition of an anti-PD-1 antibody to chemotherapy in patients with NPC could increase the efficacy of induction chemotherapy. If confirmed in a clinical trial, more efficient induction therapy could allow the dose of radiotherapy to be reduced and thereby diminish severe late effects of such therapy.

Background: Nasopharyngeal carcinoma (NPC) in endemic regions and younger patients is characterized by a prominent lymphomononuclear infiltration. Radiation is the principal therapeutic modality for patients with NPC. Recent data suggest that the efficacy of radiotherapy in various cancers can be augmented when combined with immune checkpoint blockade. Here, we investigate the effect of radiotherapy on the killing of NPC cells by Natural Killer (NK) cells. Methods: NPC cell lines and a patient-derived xenograft were exposed to NK cells in the context of radiotherapy. Cytotoxicity was measured using the calcein-release assay. The contribution of the PD-L1/PD-1 checkpoint and signaling pathways to killing were analyzed using specific inhibitors. Results: Radiotherapy sensitized NPC cells to NK cell killing and upregulated expression of PD-1 ligand (PD-L1) in NPC cells and PD-1 receptor (PD-1) in NK cells. Blocking of the PD-L1/PD-1 checkpoint further increased the killing of NPC cells by NK cells in the context of radiotherapy. Conclusion: Radiation boosts the killing of NPC cells by NK cells. Killing can be further augmented by blockade of the PD-L1/PD-1 checkpoint. The combination of radiotherapy with PD-L1/PD-1 checkpoint blockade could therefore increase the efficacy of radiotherapy in NPC tumors.

Nasopharyngeal carcinoma (NPC) is a highly malignant epithelial cancer linked to EBV infection. Addition of interferon-β (IFNβ) to chemo- and radiochemotherapy has led to survival rates >90% in children and adolescents. As NPC cells are sensitive to apoptosis via tumor necrosis factor-related apoptosis inducing ligand (TRAIL), we explored the role of TRAIL and IFNβ in the killing of NPC cells by natural killer (NK) cells. NPC cells, including cells of a patient-derived xenograft were exposed to NK cells in the presence or absence of IFNβ. NK cells killed NPC- but not nasoepithelial cells and killing was predominately mediated via TRAIL. Incubation of NK cells with IFNβ increased cytotoxicity against NPC cells. Concomitant incubation of NK- and NPC cells with IFNβ before coculture reduced cytotoxicity and could be overcome by blocking the PD-1/PD-L1 axis leading to the release of intracellular TRAIL from NK cells. In conclusion, combination of IFNβ and anti-PD-1, augmenting cytotoxicity of NK cells against NPC cells, could be a strategy to improve NPC-directed therapy and warrants further evaluation in vivo.

Background/Objectives: Melanoma is a highly malignant skin tumor with poor response to conventional chemotherapeutic regimens. Melanoma cells induce cytotoxic T cell-mediated immune responses, and immunotherapy has significantly improved survival rates for patients with advanced disease. Methods: Here, we investigate NK cell-mediated melanoma cell killing and its regulation by PD-L1/PD-1 blockade and IFNβ. Four melanoma cell lines were used in this study. To evaluate NK cell cytotoxicity, cells were exposed to NK cells with or without IFNβ. The calcein release assay was used to measure cell death, while specific inhibitors and siRNA silencing were applied to determine the contribution of individual effector pathways. Results: NK cells were able to kill melanoma cells with sensitivity to killing varying between different cell lines. Cytotoxic effects were mainly mediated through activation of the TRAIL signaling cascade. In cell lines with low sensitivity to NK cell killing, expression of PD-L1 was noted and killing by NK cells could be significantly increased by inhibition of the PD-L1/PD-1 checkpoint. Killing of melanoma cells could be further increased by incubation of NK cells with IFNβ. Conclusions: Our results point to a role of NK cells in the killing of melanoma cells and a potential clinical benefit of a combination therapy of IFNβ and anti-PD-1 antibody.

Nasopharyngeal carcinoma (NPC) is a malignant tumor that originates from the epithelial cells of the nasopharynx. NPC is closely linked to Epstein-Barr virus (EBV) infection, which necessitates the use of EBV-positive cell lines for accurate pathology studies. In this paper, we present a detailed comparison of the C666-1 and C17 cell lines using bulk RNA-sequencing (RNA-Seq) methods. By thoroughly examining the gene expression profiles of these cell lines, we aim to elucidate the molecular mechanisms that drive NPC progression and metastasis. Understanding these mechanisms is crucial for developing effective treatment strategies. Cancer cell line models are essential in this research, as they provide a controlled environment for studying the complex interplay between viral and host cellular factors. Additionally, our study highlights the differences between the two cell lines, which could be pivotal in designing new experiments and tailoring therapeutic approaches.