Compared with the blank group, the expression of p-Smad3 protein in gastric cancer cells (Hgc27 and MKN45) in the M2c co culture group showed the same trend (Fig. 6j), while there was a significant difference in Smad3 protein expression between the two gastric cancer cell lines M2c co culture groups. This evidence concerns the gene SMAD3 and gastric cancer.