SFRP4 and mesothelioma: CpG island methylation, along with down‐regulation of Sfrps, has been reported in cancers such as oesophageal carcinoma,50 ovarian cancer and mesothelioma.51, 52 Of 5 Sfrps, Sfrp4 was found with down‐regulated mRNA expression and hyper‐methylation in the foetal forebrain in PH group.