CLDN1 and neoplasm: In addition, meta-analysis showed that claudin-1 was associated with early tumor stage (n = 3; RR, 0.75; 95% CI, 0.54–1.04; P = 0.09) and negative lymph node metastasis(n = 4; RR, 0.91; 95% CI, 0.82–1.02; P = 0.10), although it was not statistically significant.