MUC1-C auto-regulatory complex with EBNA1 is responsible for latent Epstein-Barr virus-associated gastric cancer progression

Latent Epstein-Barr Virus (EBV) infection promotes cancers derived from B-lymphocytes and epithelial cells. EBV-encoded nuclear antigen 1 (EBNA1) is uniformly expressed in EBV-associated cancers. The MUC1 gene evolved in mammals to protect barrier tissues from viral infections. We report that MUC1 and the encoded oncogenic MUC1-C protein are upregulated in EBV-associated gastric cancers (EBVaGCs). We demonstrate that EBNA1 forms a complex with MUC1-C that regulates EBNA1 and MUC1-C expression. EBNA1 appropriates MUC1-C for (i) inducing DNA methyltransferases and DNA methylation, (ii) suppressing p21 and driving cell cycle progression, (iii) increasing survivin in promoting survival, and (iv) regulating MYC as an effector of EBV latency. MUC1-C thereby functions in maintaining EBV episomes and regulating EBV latency and lytic genes. In regard to EBVaGC progression, MUC1-C regulates expression of the SOX2 and NOTCH1-3 stemness genes, self-renewal capacity, and tumorigenicity. These findings indicate that EBNA1 co-opts MUC1-C functions that promote EBV latency and that MUC1-C is necessary for EBVaGC pathogenesis.