TMPRSS2 and Familial prostate cancer: (1) PCP4 gene loss occurs at high frequency in PCa patients, and decreased expression of PCP4 correlates with poor prognosis of PCa, particularly CRPC development; (2) TMPRSS2-ERG fusion frequently co-occurs with PCP4 deletion; (3) PCP4 suppresses prostate cancer progression in vitro and in vivo; (4) PCP4 is an androgen receptor (AR) suppressed gene; (5) PCP4 was involved in the stabilization of CAMKK2 protein; (6) PCP4 inhibits PCa progression by regulating Ca2+/CAMKK2/AMPK/AR signaling axis.