Ephrin receptor A2, the epithelial receptor for Epstein-Barr virus entry, is not available for efficient infection in human gastric organoids

Author summary Epstein-Barr virus (EBV) is associated with malignancies of lymphoid and epithelial cell lineages, including gastric cancer (GC). Although EBV is only associated with up to 10% of GC, this unique subset is genetically and epigenetically distinct from other forms of GC. However, the sequence of events leading to EBV-associated GC (EBVaGC) remains unclear. Ephrin receptor A2 (EPHA2) was identified as a receptor for EBV entry into epithelial cancer cell lines, yet the physiological relevance of its role in infection of healthy gastric epithelium was not explored. Using human adult healthy stem cell-derived gastric organoids, microscopy showed the EPHA2 receptor was strictly localized to cell-cell junctions and therefore inaccessible to EBV, resulting in poor infection. In contrast, EPHA2 expression was not confined to cell-cell junctions in cancer-derived organoids, rendering it accessible to EBV. Correspondingly, these organoids were more readily infected. Although EBV was not detected in healthy gastric epithelial tissue, immunohistochemical analysis identified EBV in inflamed epithelium. These results suggest viral entry requires initial changes to the gastric epithelium, likely induced by inflammation, to expose the virus receptor and enable efficient infection. Epstein-Barr virus (EBV) is best known for infection of B cells, in which it usually establishes an asymptomatic lifelong infection, but is also associated with the development of multiple B cell lymphomas. EBV also infects epithelial cells and is associated with all cases of undifferentiated nasopharyngeal carcinoma (NPC). EBV is etiologically linked with at least 8% of gastric cancer (EBVaGC) that comprises a genetically and epigenetically distinct subset of GC. Although we have a very good understanding of B cell entry and lymphomagenesis, the sequence of events leading to EBVaGC remains poorly understood. Recently, ephrin receptor A2 (EPHA2) was proposed as the epithelial cell receptor on human cancer cell lines. Although we confirm some of these results, we demonstrate that EBV does not infect healthy adult stem cell-derived gastric organoids. In matched pairs of normal and cancer-derived organoids from the same patient, EBV only reproducibly infected the cancer organoids. While there was no clear pattern of differential expression between normal and cancer organoids for EPHA2 at the RNA and protein level, the subcellular location of the protein differed markedly. Confocal microscopy showed EPHA2 localization at the cell-cell junctions in primary cells, but not in cancer cell lines. Furthermore, histologic analysis of patient tissue revealed the absence of EBV in healthy epithelium and presence of EBV in epithelial cells from inflamed tissue. These data suggest that the EPHA2 receptor is not accessible to EBV on healthy gastric epithelial cells with intact cell-cell contacts, but either this or another, yet to be identified receptor may become accessible following cellular changes induced by inflammation or transformation, rendering changes in the cellular architecture an essential prerequisite to EBV infection.

Automated summary

The study reveals that EBV infection in gastric cancer is associated with partial changes in the Ephrin receptor A2 (EPHA2) of gastric epithelial cells. In healthy gastric epithelium, this receptor is confined to cell-cell junctions, making it difficult for EBV infection, while it is expressed normally in cancer cells, making them susceptible to infection.