Cherradi S, et al. - Researchers compared claudin (CLDN) gene expression as well as their prognostic value in colorectal cancer (CRC) samples, with different CRC molecular subtypes, vs in normal colon mucosa. They used gene expression data for a cohort of 143 primary CRC samples to assess CLDN expression and thereafter, compared with different molecular subtypes (C1 to C6 according to the Marisa’s classification, and CMS1 to CMS4 of the consensus classification) defined in the same CRC samples. In CRC sample, upregulation of CLDN1 and CLDN2 and downregulation of CLDN5, 7, 8, and 23 were detected, compared with normal mucosa. A strong prognostic value of expression of CLDN2 or CLDN4 alone was seen, which was increased when they were related. Longer OS in relation to lower expressions of CLDN11, CLDN12, and CLDN23 was reported in the CMS4/C4 subtypes. A prognostic value of CLDN6 and CLDN11 was evident in the CMS2 and C4 subtypes, respectively. Overall, in the evaluation of CLDN potential value as prognostic markers or therapeutic targets, it is necessary to consider CRC heterogeneity.