The Multi-kinase Inhibitor Lenvatinib Interacts with the HDAC Inhibitor Entinostat to Kill Liver Cancer Cells

Prior studies from our group have combined the multi-kinase inhibitor sorafenib with HDAC inhibitors in GI tumor cells that resulted in the trials NCT02349867 and NCT01075113. The multi-kinase inhibitor lenvatinib, for the treatment of liver cancer, has fewer negative sequelae than sorafenib. We determined the mechanisms by which lenvatinib interacted with the HDAC inhibitor entinostat to kill hepatoma cells. Lenvatinib and entinostat interacted in an additive to greater-than-additive fashion to kill liver cancer cells. The drugs inactivated mTORC1 and mTORC2 and interacted to further increase the phosphorylation of ATM, ATG13 and eIF2α. Elevated eIF2α phosphorylation was responsible for reduced MCL-1 and BCL-XL expression and for increased Beclin1 and ATG5 expression. Over-expression of BCL-XL or knock down of Beclin1 or ATG5, significantly reduced killing. The drugs synergized to elevate ROS production; activation of ATM was ROS-dependent. ATM activation was required for enhanced phosphorylation of γH2AX, eIF2α and ATG13 S318. The drug combination reduced histone deacetylase protein expression which required autophagy. Knock down of HDACs1/2/3 prevented the lenvatinib and entinostat combination from regulating PD-L1 and MHCA expression. Collectively, our data demonstrate that lenvatinib and entinostat interact to kill liver cancer cells via ROS-dependent activation of ATM and inactivation of eIF2α, resulting in greater levels of toxic autophagosome formation and reduced expression of protective mitochondrial proteins.