CLDN7 and adenocarcinoma: Moreover, Xu et al. proved that the positivity rate of Claudin-7 expression was significantly lower in CRC tissues than in peritumoral normal tissue and Claudin-7 expression was correlated with the grade of differentiation, being downregulated in well-differentiated adenocarcinomas, further downregulated in moderately differentiated adenocarcinomas, and significantly downregulated in poorly differentiated adenocarcinoma [5].