Abstract 2690: Sorafenib/regorafenib and phosphatidyl inositol 3 kinase/thymoma viral proto-oncogene inhibition interact to kill tumor cells

Abstract

Abstract The present study aimed to determine whether the multikinase inhibitors, sorafenib/regorafenib, worked in conjunction with PI3K/AKT inhibitors to enhance tumor cell death. It has been noted that combination of sorafenib/regorafenib with a PI3K inhibitor acetic acid (PX-866) resulted in tumor cell death, in a greater than additive fashion, in liver, colorectal, lung, breast, kidney and brain cancer cells. Similar data was obtained using AKT inhibitors perifosine and MK2206. Furthermore, even cells lacking PTEN remained as sensitive to this combinational approach as cells expressing PTEN. PX-866 treatment abolished AKT/GSK3 phosphorylation, with tumor cell death correlating with reduced activity of AKT and mTOR. Expression of activated AKT and to a lesser extent activated mTOR reduced drug combination lethality. Expression of B-cell lymphoma-extra large or dominant negative caspase 9, but not cellular FLICE-inhibitory protein short, protected cells from the drug combination. Treatment of cells with PX-866 increased protein levels of p62, LAMP2 and LC3/LC3II which correlated with the resulting increase in LC3-GFP vesicle numbers. Exposure of PX-866 treated cells to sorafenib reduced p62 and LAMP2 levels, decreased the ratio of LC3 to LC3II and reduced LC3-GFP vesicle levels. Knockdown of Beclin1 or ATG5 suppressed drug toxicity by ∼40%. In vivo, combination of either sorafenib and PX-866 or regorafenib and MK2206 cooperated to suppress the growth of established HuH7 and HCT116 tumors, respectively. Collectively our data demonstrates that the combination of sorafenib family kinase inhibitors with inhibitors of the PI3K/AKT pathway kills tumor cells in vitro and in vivo. Citation Format: Larry A. Booth, Nichola A. Cruickshanks, G B. Sajithlal, Hossein A. Hamed, Seyedmehrad Tavallai, J Syed, Steven Grant, Andrew Poklepovic, Paul Dent. Sorafenib/regorafenib and phosphatidyl inositol 3 kinase/thymoma viral proto-oncogene inhibition interact to kill tumor cells. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2690. doi:10.1158/1538-7445.AM2014-2690