a Kaplan-Meier plots of CRPC (n = 55) and NEPC (n = 21) patients stratified into three categories according to MYCN (N-Myc) expression and/or RB1 status. Univariate overall survival analysis was calculated from the time of initial diagnosis of metastatic disease to death from any cause. Patients still alive at the time of the last follow-up were censored. Patients with high N-Myc expression and RB1 deletion showed significantly worse survival compared to the other two groups (p = 0.031, Kaplan-Meier estimator (two-sided log-rank test)). b Survival plots of intact PN or PRN mice using the Kaplan-Meier estimator (**p = 0.0056, log-rank test). c Top: percentage of GEM tumor foci with conventional adenocarcinoma (including HGPIN, intracystic carcinoma, adenocarcinoma), poorly differentiated/neuroendocrine features, squamous differentiation, and intestinal differentiation based on pathologist assessment. Bottom: Hematoxylin and eosin (H&E) and IHC staining of NEPC focus for N-Myc, RB1, epithelial markers AR and CK8, reprogramming factor EZH2, and small cell neuroendocrine marker INSM1. Images are representative of 13 mice. Scale bar: 50 μm. d H&E and IHC of AR, N-Myc, INSM1 on primary tumor, lung, liver, and lymph node metastasis in a 19-week-old PRN mouse. Images are representative of 2 mice. Scale bar: 50 μm. e MRI coronal scans from P (n = 5), PR (n = 3); PN (n = 4); and PRN (n = 6) GEMs from 8 to 20 weeks of age. Mice were castrated at 12 weeks of age. f Fold change volume over time of P (n = 5), PR (n = 3); PN (n = 4); and PRN (n = 6) GEM tumors from mice castrated at 12 weeks. PRN: *p = 0.0187, **p = 0.0027, ***p = 0.0002, ****p < 0.0001, PN: #p = 0.0129, ##p = 0.0075, two-tailed t-test between indicated genotype and P mice. Data are presented as mean values +/− SEM. g H&Es of poorly differentiated subcutaneous mouse allograft primary tumor and metastases derived from Adeno-Cre-transduced PRN organoids. The dashed lines separate the tumor metastasis from normal tissue. Images are representative of 18 independent mice. Scale bar: 50 μm.