We have shown in Cld-1-Tg mice and colon cancer cell lines that increased claudin-1 expression can increase Notch signaling with downregulation of expression of mucosal defense genes Muc2, KLF4 and Tff3[5] and in this study microarray data and qRT-PCR analysis confirmed downregulation of these genes in the tumors of APC-Cldn1 mice. Here, CLDN1 is linked to malignant colon neoplasm.