library_construction_protocol: RNA from freshly collected cells was extracted using TRIzol Reagent. Libraries were prepared using KAPA Stranded mRNA Sequencing Kit (1 ug of total RNA). For 4T1/EMT6.5 co-cultured with Bend3 cells, tumor and endothelial cells were separated by FACS sorting prior to RNA extraction. RNA libraries were prepared for sequencing using standard Illumina protocols. HiSeq4000 (Illumina) using a flow cell generating 1x50bp single-end reads.