This is consistent with the observation that the ERVK envelope protein is frequently expressed at the surface of tumor cells which appears to allow them to remain undetected by the immune system and still allow the recognition of ERVK Env as a non-self target, as evidenced by an ERVK Env-specific antibody response (Hahn et al., 2008; Wang-Johanning et al., 2012; Reis et al., 2013). Here, ERVW-1 is linked to neoplasm.