B2M and colorectal carcinoma: For faecal samples from CRC patients, COX-2 mRNA expression was significantly correlated with B2M mRNA (r=0.70, P<0.001, Figure 1A), CEA mRNA (r=0.54, P<0.001, Figure 1B), and E-cad mRNA (r=0.61, P<0.001, Figure 1D) expressions, suggesting that the increased faecal expression of COX-2 mRNA is related to the number of exfoliated cells.