CTXN1 and ductal breast carcinoma in situ: Several genes important in cellular signal transduction such as PDE6G, CALCB, BDNF, SFRP2, and transport such as ATOX1, FXYD2, SLC7A9, were hypomethylated in later stages of TN-DCIS progression, with the exception of CTXN1, a mediator of intracellular and extracellular signaling.