TCF4 and colorectal carcinoma: To determine the impact of altered Wnt signaling (TCF4 activity) on the expression of OSBPL1A and TRAK1 isoforms, overexpression of a dominant negative form of TCF4 (dnTCF4) was used to interrupt the TCF4 mediated part of the Wnt-pathway in the two CRC cell lines, DLD1 and Ls174T [17].