Mechanisms of Arginine Starvation Induced Cell Death

PEGylated Arginine Deiminase (ADI-PEG20) is a therapeutic that degrades extracellular arginine.  In tumors like sarcoma that cannot make their own arginine due to a urea cycle defect, this agent put tumors into a starvation state.  As ~90% of sarcomas are resistant to arginine starvation due to the loss of the expression of Argininosuccinate Synthetase 1 (ASS1), therapies involving ADI-PEG20 cross the numerous histologic barriers in sarcoma.  The aim of the proposal is to define the mechanisms of resistance to the arginine starvation to improve therapy based on intrinsic tumor metabolism.  In order to better understand what happens when sarcomas are treated with ADI-PEG20, recently published work by our group has demonstrated that a metabolic and proteomic rewiring takes place.  As the overall goal of sarcoma metabolic therapy is to develop a biomarker (ASS1) driven synthetic lethal strategy, identifying multiple metabolic targets is underway.  The purpose of this proposal is to study the effects that starvation has on the cell death machinery.  Preliminary data Initial data demonstrates a BAX/Bcl-xL dependent prosurvival that is not understood fully.  Overall, we hypothesize that the starvation response inhibits the ability of a tumor to enter into apoptosis by depleting key parts of the apoptosis cascade.  First, in AIM 1, we will define the effects of arginine starvation on the location of the apoptotic machinery within a cell.  The focus of this is on the subcellular location of BAX, which is needed to induce apoptosis. Next, in Aim 2, we will define what parts of the apoptotic machinery are affected by the arginine starvation response.  This will focus not only on the activators or inhibitors in the pathway. Finally, in Aim 3, we will confirm that our findings hold not only in a test tube, but also in complex living models such as a mouse. If the mechanisms of resistance to arginine starvation induced cell death can be determined, this would represent a highly significant contribution to the field of metabolic therapy in sarcoma.  The support for this project by the SFA will help to derive the preclinical data needed for future clinical trials utilize ADI-PEG20 for the treatment of sarcoma.