Trp53 Mutation in Keratin 5 (Krt5)-Expressing Basal Cells Facilitates the Development of Basal Squamous-Like Invasive Bladder Cancer in the Chemical Carcinogenesis of Mouse Bladder.

The biological processes of urothelial carcinogenesis are not fully understood, particularly regarding the relationship between specific genetic events, cell of origin, and molecular subtypes of subsequent tumors. N-butyl-N-(4-hydroxybutyl)-nitrosamine (BBN)-induced mouse bladder cancer is widely accepted as a useful model that recapitulates the pathway of human bladder tumorigenesis from dysplasia to invasive cancer via carcinoma in situ. However, the long and variable time of tumorigenesis often hinders efficient preclinical or translational research. We hypothesized that Trp53 mutation in specific types of urothelial cells facilitates efficient development of clinically relevant bladder cancer. Using lineage tracing, we showed that Trp53 mutation in Krt5-expressing cells resulted in more efficient tumorigenesis of mouse muscle-invasive bladder cancer (MIBC) with squamous differentiation compared with Trp53 mutation in Upk2-expressing cells, or wild-type or hemizygous Trp53 in the entire urothelium. Mouse MIBC that developed at 24 weeks of BBN treatment showed morphologic and genetic similarities to the basal squamous subtypes of human MIBC, irrespective of pre-induction of Trp53 mutation or whether the cell of origin was Krt5- or Upk2-expressing cells. Our findings suggest that intermediate cells as well as basal cells also can give rise to basal-like MIBC, with pre-induction of Trp53 mutation accelerating MIBC. Thus, in BBN chemical carcinogenesis, pre-induction of Trp53 mutation in basal cells facilitates efficient modeling of the basal squamous subtype of human MIBC.