MAGEA4 and breast carcinoma: [26] Particularly, EBNA1 expression is essential for viral episome maintenance and replication and it is expressed in all known forms of latency. In the present study we indeed demonstrated the expression of EBNA1 in a subset of breast carcinoma tumor cells by IHC analysis with two different clones of monoclonal antibodies (1H4 and 2B4). Hennard and co-workers [20] reported EBNA1 2B4 mAb cross-reactivity with MAGE-4, a protein expressed in various human cancers.