Fig. 3: NUMB loss drives spontaneous malignant transformation of the normal urothelium and accelerates carcinogen-induced bladder tumorigenesis.

a NUMB expression in the urothelium of untreated adult WT (WT) and NUMB-KO (KO) mice. Bars, 100 μm. Images are representative of the bladders of 28 WT and 23 NUMB-KO mice examined. b Left, Representative H&E images of the normal WT urothelium, and preneoplastic (Hyperplasia) and neoplastic (carcinoma in situ, CIS; invasive cancer, IC) urothelial lesions from NUMB-KO mice. The black arrowhead indicates IC. Bars, 100 μm. Right, Incidence (%) of histological phenotypes in the urothelium of untreated, aged-matched 4- to 12-month old WT (n = 28) and NUMB-KO (n = 23) mice. ****, p = 0.00002 by two-sided Pearson’s Chi-squared test. Odds ratio (OR) with 95% CI and associated two-sided p-value by Fisher’s exact test is shown. c Aged-matched 8- to 16-week-old WT (n = 39) and NUMB-KO (n = 37) mice were exposed to 0.05% BBN in the drinking water for 16 weeks followed by a 2-week washout period. Bladder tissues were harvested and examined for histological changes (H&E) and NUMB expression (IHC). Left, Representative images of a preneoplastic (Hyperplasia) lesion from BBN-WT mice and neoplastic (CIS and IC) lesions from BBN-NUMB-KO mice. Right, Incidence (%) of histological phenotypes in WT vs. KO mice at the end of treatment. Bars, 100 μm. *, p = 0.025 by two-sided Pearson’s Chi-squared test; OR (95% CI) with associated two-sided p-value by Fisher’s exact test is shown. d Kaplan–Meier plot showing the disease-specific survival (%) of aged-matched 8- to 16-week-old WT (n = 14) and NUMB-KO (n = 13) mice treated for 20 weeks with BBN before switching to regular drinking water. Mice were sacrificed according to endpoints. Dashed-line, WT (n = 10) and NUMB-KO (n = 10) untreated mice. HR, (95% CI) with two-sided p-value by Log Rank test are shown. e MIBC lesions excised from BBN-WT mice (n = 13) were compared to the normal urothelium of untreated WT mice (n = 8) for NUMB expression by IHC. Shown are three MIBC lesions, one NUMB^High (WT1) and two NUMB^Low (WT2, WT3), and the normal NUMB^High urothelium of untreated mice. Bars, 100 μm. f Quantification of the experiment in ‘e’ showing the incidence (%) of NUMB^Low vs. NUMB^High MIBC tumors induced by BBN treatment in WT mice. *, p = 0.018 by two-sided Fisher’s exact test. Source data are provided as Source Data file.