There was a statistically significant albeit weak positive correlation between levels of MSMB and free PSA as well as between MSMB and total PSA in serum from cancer cases (Spearman r = 0.3990 and 0.3200, respectively) and in controls (Spearman r = 0.3421 and 0.2710, respectively), p<0.0001 in all (S5 Fig), and significant association between the free-to-total PSA ratio and the serum levels of MSMB in cases and controls (Spearman r = 0.2142; r = 0.1351, respectively), p<0.0001 in all (S5 Fig). This evidence concerns the gene KLK3 and cancer.