Using pegylated arginine deiminase (ADI-PEG20) for the treatment of sarcomas that lack argininosuccinate synthesase 1 expression.

Abstract

10526 Background: To better understand the metabolism of sarcomas, we explored the role of argininosuccinate synthase 1 (ASS1), the rate-limiting enzyme in the conversion of citrulline to arginine in the urea cycle. When ASS1 is not expressed the amino acid arginine becomes an essential amino acid that must be delivered from the diet. The potential for therapeutic manipulation of this pathway with pegylated arginine deiminase (ADI-PEG20) was explored using metabolomic mass spectroscopy. Methods: Immunohistochemistry (IHC) of ASS1 expression on 701 patient specimens representing 45 subtypes of sarcoma was performed. Proliferation and cell death were analyzed in a panel of cell lines. Clonogenic assays were performed using ADI-PEG20 and chloroquine. Autophagy induction and inhibition was assessed. Xenograft models were tested. Metabolomic mass spectroscopy was performed in the presence and absence of ADI-PEG20. Results: lHC analysis demonstrated that ASS1 is not expressed in over 85% of sarcomas (619 of 701 patient samples). Treatment of a panel of LMS, synovial, ASPS, GIST, MPNST, chondrosarcoma, osteosarcoma, and Ewings sarcoma cell lines with ADI-PEG20 resulted in cell cycle arrest but not apoptosis when ASS1 expression was low (13/15 lines). Xenografts of the ASS1 low MNNG/HOS cells and SKLMS1 cells into nude mice followed by treatment with ADI-PEG20 +/- chloroquine demonstrated significantly slower tumor growth as compared to PBS or chloroquine treated controls. Treatment of sarcomas that lack ASS1 with ADI-PEG20 induced autophagy. Global analysis of metabolomic mass spectroscopy demonstrated alterations in PKM2, glutamine dependence, the Warburg effect, the TCA cycle and glutathione biology. Conclusions: This suggests that sarcomas may be sensitive to the arginine depletion therapy using ADI-PEG20. Autophagy induction has global metabolic consequences for sarcoma. Successful control of tumor burden by using arginine deprivation therapy and autophagy inhibition in our preclinical studies will help to orient clinical trials for this innovative treatment in patients with sarcoma that lack ASS1 expression.