MAPK1 and gastric cancer: MAPK1-109aa, encoded by circMAPK1 (hsa_circ_0004872), can inhibit the phosphorylation of mitogen-activated protein kinase 1 (MAPK1) by competitively binding to mitogen-activated protein kinase kinase 1, thereby suppressing the activation of MAPK1 and its downstream factors in MAPK pathway, finally attenuating the proliferation and metastasis of GC cells [44].