Several of these display an expression pattern similar to a neighboring protein-coding gene, including cancer-associated genes DKK1 and CTSC [40,41] (Figure 1) and developmental regulators IRX2, SIX3 and ZNF536 [42], suggesting that they may be functional RNAs regulating nearby genes [43] or represent transcription from active enhancers [44]. This evidence concerns the gene DKK1 and cancer.