DDX43 encodes a ‘cancer testis antigen’ (also called HAGE), which is an RNA-dependent helicase with expression largely restricted to testis and a variety of cancer types.40 TDRD12 encodes a tudor domain-containing protein (also capable of functioning as an RNA-dependent helicase) found almost exclusively in testes.41 It is important in the biogenesis of piRNAs, which are also testis specific.41 Hence the heavy methylation of these genes in all control samples is consistent with their very restricted expression patterns in normal tissues. This evidence concerns the gene DDX43 and cancer.