Xenograft tumors were harvested, cut into small chunks and snap frozen using liquid nitrogren and stored at -80°C until sample preparation. Tissue processing and nuclei RNA fixation of the snap frozen PDX samples were performed using Chromium Next GEM Single Cell Fixed RNA Sample Preparation Kit (10x Genomics). Fixation was then quenched and samples were stored at -80°C until sequencing. Single nuclei RNAseq libraries were prepared according to Chromium Single Cell Gene Expression 3v3.1 kit (10x Genomics), similar to the cDNA synthesis and barcoding process for each single cell. Single-cell nuclei RNA libraries were sequenced using NovaSeq (read configuration: Paired End 28-10-10-90; 1% PhiX Spike-in; read depth 100M/sample).