Although the mechanism is still elusive, we speculate that it may be due to the functionally contradictory effects of some proteins critical for apoptotic signaling in different cell types induced by ATO, such as the proapoptotic effects of c-Jun-NH2-kinase (JNK) activation in ATO-induced ovarian cancer cells [27] in contrast to the antiapoptotic effects on JNK activation in some other cell lines [28, 29]. Here, MAPK8 is linked to ovarian carcinoma.