Moreover, as shown in the Figure S1a-b, SFRP1 was not significantly affected by SFRP2 siRNA, and SFRP1 siRNA had no effect on the SFRP2 levels, in PHF21B-RNAi#1 PCa cells, suggesting that either SFRP1 or SFRP2 siRNA rescued TOPflash activity and self-renewal ability in PHF21B-silenced cells was not attributed to the siRNA cross-reaction. This evidence concerns the gene SFRP2 and posterior cortical atrophy.