ERVMER34-1 and squamous cell lung carcinoma: Among six cell lines which endogenously express HEMO (NCIH520, HCC827, OVMANA, Caco‐2, SW480, and HCT116), the lung squamous cell carcinoma NCIH520 and colorectal adenocarcinoma Caco‐2 cell lines were selected since they showed the highest HEMO expression levels (Fig. S3).