TP53 and neoplasm: Using single-cell RNA sequencing (scRNA-seq), we compared these rare single-positive cells that underwent p53 LOH (pre-tumor p53-deficient, 1–3% of all mKate2+ cells) to their p53-proficient double-positive counterparts (pre-tumor p53 proficient), and to single positive cells isolated from full-blown tumors (tumor p53-deficient) (Fig. 1d, Fig. S1a–d and Methods).