MAPK3 and gastric cancer: Given that p-ERK plays an essential role in autophagy [38, 39], we used PD98059, an inhibitor of ERK1/2 signaling, to treat GC cells and found that PD98059 led to a prominent reduction in the phosphorylation of STAT3 at Ser727 without any effects on the phosphorylation of STAT3 at Tyr705 and total STAT3 protein levels (Fig. S6b).