CLDN1 and colorectal carcinoma: The estimated calcium treatment effects were greater among participants with baseline serum 25-OH-vitamin D concentrations below the median value of 22.69 ng/mL (claudin-1: 29%, p = 0.04; OCLD: 36%, p = 0.06; MUC12: 35%, p = 0.05), suggesting the link between vitamin D deficiency and TJ proteins in the human CRC.