RAC2 and gastric cancer: Numerous studies have shown that the extracellular signal-regulated kinase (ERK)/MAPK pathways and downstream molecules (KRAS and NRAS: RAS family genes; Ras: small G-protein; BRAF: B-Raf proto-oncogene serine/threonine kinase; ERBB2 and ERBB3: ERBB epidermal growth factor receptor) [79,85,86] play a role in regulating cell motility in both gastric cancer (GC) and normal epithelial cells.