ERVW-1 and cancer: With the purpose of screening for viral splicing transcripts in cancer cell lines, in our previous work (28), we undertook RT-PCR across splicing sites of full-length HERV-K in various cancer cell lines, including breast cancer, cervical cancer, prostate cancer, and head and neck cancer, which are expected to find 1X-spliced transcript for env and 2X-spliced transcript for np9 or rec, respectively, for type I and type II HERV-K-HML2 viruses (25).