SFRP1 and posterior cortical atrophy: Given that the protein and mRNA levels of SFRP1 significantly decreased with increasing degree of malignancy, and 5Aza, a DNA methylation inhibitor, up-regulated both protein and mRNA levels of SFRP1 in PCa cell lines, we speculated that SFRP1 silencing was likely to be induced by SFRP1 gene methylation.