RB1 and small cell carcinoma: In line with this, transcriptomic upregulation of basal markers is observed in prostate adenocarcinoma cell lines after the sole inactivation of TP53 and RB1. 51 Similar results were obtained in a preclinical model leveraging human prostate epithelial cells with concurrent inactivation of TP53/RB1, as well as overexpression of MYC, BCL2 and a constitutively active AKT isoform.68 Engraftment in vivo of such cells leads to the formation of tumors again exhibiting multiple histologies such as adenocarcinoma, squamous, small cell carcinomas, and mixed phenotypes.