SMAD4 and metastatic prostate carcinoma: Further molecular aberrations including the loss of SMAD Family Member 4 (SMAD4), AR corepressors, mutations in AR, FOXA1, BRCA1/2, ATM, ATR, and RAD51 accompanied with the gain of function of the AR coactivator, CXCL12, CXCR4, RANK-RANKL, EMT, BAI1, and EZH2 lead to the development of metastatic prostate cancer [44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59].