Compared with the blank group, the expression of p-Smad2 protein in gastric cancer cells (Hgc27 and MKN45) in the M2c co culture group showed the same trend (Fig. 6h), while there was a significant difference in Smad2 protein expression between the two gastric cancer cell lines in the M2c co culture group. Here, SMAD2 is linked to gastric cancer.