Antibody targets include both cell surface and intracellular HERV proteins and although antibody responses to HERV‐K (HML‐2) Gag, Env, Rec, and Np9 in cancer patients are the most frequently reported, antibodies to Env and Gag proteins from other HERVs, including HERV‐E, HERV‐H, HERV‐W and Human T‐lymphotropic virus (HTLV)‐related endogenous sequence‐1 (HRES‐1) have also been detected (Table 1). This evidence concerns the gene ERVW-1 and cancer.