library_construction_protocol: At the experimental endpoint, mice were perfused through the left ventricle with 1% PFA in PBS for 2 minutes. Extracted tumors were minced using razor blade and dissociated into single-cell suspensions by incubating in digestion medium made of FACS buffer (PBS + 2% FBS, 0.1% collagenase IV (Worthington, #LS004188), and 10 U/ml DNase type I (Sigma, #D4527)) for 30 minutes at 37°C. Digested cells were then filtered with 70 µm nylon mesh. Red blood cells (RBC) were lysed by incubating cells in 1× RBC Lysis buffer (eBioscience, #00-4300-54). Tumor cells were suspended in PBS with 0.4% BSA and submitted for 10x Genomics processing at Columbia Genome Center at Columbia University Medical Center. Libraries were prepared using the 10x Genomics Single Cell Gene Expression platform. The 3' or 5' Single Cell Gene Expression workflow was used to encapsulate individual cells (or nuclei) in droplets, where lysis and reverse transcription occurred with cell- and molecule-specific barcoding. Following cDNA amplification, libraries were constructed with 10x Genomics reagents. The resulting libraries were sequenced on an Illumina NovaSeq 6000 (or NextSeq 500/550 as appropriate).