CLDN1 and chronic obstructive pulmonary disease: Wnt target genes, including MMP7, VEGFA, CLDN1, CCND1, SOX9, RHOU, were also down-regulated in healthy smokers and smokers with COPD compared to healthy nonsmokers (p<0.05 for VEGFA and p<0.01 for the other genes; Figure 2, Table 3).