MCL1 and cancer: It is known that survivin [31–38], Mcl-1 [39–47], XIAP [35, 36, 38, 44, 48–55], and cIPA2 [55] are strongly involved in treatment resistance of PDAC; survivin [56–69] and Mcl-1 [70, 71] play important roles in cancer stem cell (CSC) drug resistance and function.