To quantify the impact of aging on tumor suppressor gene function, we generated a pool of barcoded lentiviral vectors encoding Cre and targeting 25 known or putative tumor suppressor genes as well as ‘sgInert’ non-targeting control vectors and a single-guide RNA (sgRNA) targeting an essential gene (Pcna) (Lenti-sgRNAAging/Cre; Fig. 2a)19. The gene discussed is PCNA; the disease is neoplasm.