ESR1 and cancer: Moreover, other MSA mechanisms of directing cancer cells to the apoptotic pathway were observed, such as the inactivation of PKC [73], inhibition of HDAC [6,32], blocking of androgen [71,74] or estrogen receptor (ER) [5] signaling, upregulation of CDK inhibitors (CDKI), which are inhibitors of kinases CDK2, -6 and -4 [7], and other molecular targets, such as the proteins regulated in development and DNA damage response 1 (REDD1), ERK 1/2, p38MAPK, JNK 1/2 or protein kinase AKT [3,26,69].