To determine a mechanism for TRIM24-mediated activation of Met expression (c-Met), previously reported to drive formation of mammary metaplastic carcinosarcoma tumors when overexpressed27,30, we performed Assay for Transposase Accessible Chromatin with high-throughput sequencing (ATAC-Seq) of murine primary cell lines; an MMTV-Cre-only cell line (823), derived from a spontaneous mammary outgrowth, and a TRIM24COE metaplastic carcinosarcoma-derived primary line (897). Here, MET is linked to carcinosarcoma.