By contrast, cellular resolution spatial transcriptomics analysis of P1-ER2 revealed that epithelial cell expression of several genes—CLDN4 (encoding claudin 4), ACTB (encoding β-actin), KRT5 (encoding keratin 5) and CTSL2 (encoding lysosomal cysteine protease cathepsin V)—differed between DCIS and invasive compartments occupied by the same, P1-purple, clone (Extended Data Fig. 5f). This evidence concerns the gene CLDN4 and ductal breast carcinoma in situ.