ERVW-1 and breast cancer: Since downregulated expression of HERV-K env RNA reduced the migration and invasion of BC cells, we further investigated the changes in these processes after restoring the expression of HERV-K env by transducing cells with a HERV-K env expression vector (+pLVX-Kenv; Figure S5B) or a vector with a synonymous mutant of HERV-K env (+pLVX-Kmut), whose purpose was to show specificity for shRNAenv, since the shRNAenv cannot knock down Kmut.