Our findings revealed that the mRNA expression levels of CLDN1, CLDN2, CLDN12, and CLDN14 were upregulated in colorectal cancer tissues relative to normal tissues in the Oncomine database, whereas CLDN3, CLDN5, CLDN7, CLDN8, CLDN11, CLDN15, and CLDN23 were downregulated, as previously reported. The gene discussed is CLDN15; the disease is colorectal cancer.