RB1 and Familial prostate cancer: NEPC tumors display neuroendocrine characteristics such as decreased AR signaling, deletion of RB1 and TP53 genes, and expression of synaptophysin and chromogranin A. It is interesting to note that in both lung and prostate cancers, tumors lacking the TP53 and RB1 genes are more likely to differentiate into small-cell tumors.