Decreased JNK activity in ER+ breast cancer cells likely contributes to the cell cycle and apoptotic responses observed upon CEP-1347 treatment, since the JNK inhibitor SP600125 mimicked the cell cycle and apoptotic effects of CEP-1347, and overexpression of c-Jun prevented the CEP-1347-induced increase in Bax expression. This evidence concerns the gene MAPK8 and breast cancer.