MAPK8 and gastric cancer: Conversely, both JNK and p38 MAPK signaling may positively regulate GADD45α in various cell types.19, 20 In agreement with the findings in other cells, pretreatment of gastric cancer cells with JNK inhibitor abolished the resultant induction of GADD45α by Cu-I, and pretreatment with p38 inhibitor notably decreased the GADD45α expression, although its induction by Cu-I still existed (Figure 5b).