A three-dimensional spheroid-specific role for Wnt-β-catenin and Eph-ephrin signaling in nasopharyngeal carcinoma cells

One of the greatest unmet needs hindering the successful treatment of nasopharyngeal carcinomas (NPCs) is for representative physiological and cost-effective models. Although Epstein-Barr virus (EBV) infection is consistently present in NPCs, most studies have focused on EBV-negative NPCs. For the first time, we established and analyzed three-dimensional (3D) spheroid models of EBV-positive and EBV-negative NPC cells and compared these to classical two-dimensional (2D) cultures in various aspects of tumor phenotype and drug responses. Compared to 2D monolayers, the 3D spheroids showed significant increases in migration capacity, stemness characteristics, hypoxia and drug resistance. Co-culture with endothelial cells, which mimics essential interactions in the tumor microenvironment, effectively enhanced spheroid dissemination. Furthermore, RNA sequencing revealed significant changes at the transcriptional level in 3D spheroids compared to expression in 2D monolayers. In particular, we identified known (VEGF, AKT and mTOR) and novel (Wnt-β-catenin and Eph-ephrin) cell signaling pathways that are activated in NPC spheroids. Targeting these pathways in 3D spheroids using FDA-approved drugs was effective in monoculture and co-culture. These findings provide the first demonstration of the establishment of EBV-positive and EBV-negative NPC 3D spheroids with features that resemble advanced and metastatic NPCs. Furthermore, we show that NPC spheroids have potential use in identifying new drug targets.