PRKAR1A and neoplasm: Using primary mammary cells obtained from Trp53+/− BALB/c mice, researchers performed a genome-wide CRISPR screen in vivo and identified several tumour suppressor genes, such as Axin1 and Prkar1a. Follow-up experiments using tumour organoids and direct intra-ductal genome editing showed that mutated Axin1 or Prkar1a, combined with Trp53 haplo-insufficiency, resulted in increased tumour growth [84].