PPP4R1L and Familial prostate cancer: PPP4R1L and SOX15 are significantly co-expressed (Pearson correlation coefficient = 0.51, P-value < 2.2 × 10−16) in tumor tissue but much less correlated in normal controls in prostate cancer (Pearson correlation coefficient = 0.24, P-value = 0.09; Fig. 4B and C).