Moreover, the down-regulation of SFRP1 has been observed in many tumors, including breast cancer [14,40], ovarian cancer [17,41], bladder cancer [13,42], mesothelioma [15], prostate cancer [18,38], colorectal cancer [12,39], and non-small cell lung cancers [26]. This evidence concerns the gene SFRP1 and mesothelioma.