SMAD4 and gastric cancer: The 18 hub genes have been reported to be associated with gastric cancer, which are CCND2 [28], STAT3 [29], TP53 [30], MCL1 [31], MYC [32], FOXO1 [33], FOXO3 [34], BCL2L11 [35], GSK3B [36], CDKN1A [37], CDH1 [38], PTEN [39], MTOR [40], MAPK1 [41], CASP3, CDC42 [42], SMAD4 [43], and IL6 [44].