Histone deacetylase inhibition is synthetically lethal with arginine deprivation in pancreatic cancers with low argininosuccinate synthetase 1 expression

Abstract

Arginine (Arg) deprivation is a promising therapeutic approach for tumors with low argininosuccinate synthetase 1 (ASS1) expression. However, its efficacy as a single agent therapy needs to be improved as resistance is frequently observed.Methods: A tissue microarray was performed to assess ASS1 expression in surgical specimens of pancreatic ductal adenocarcinoma (PDAC) and its correlation with disease prognosis. An RNA-Seq analysis examined the role of ASS1 in regulating the global gene transcriptome. A high throughput screen of FDA-approved oncology drugs identified synthetic lethality between histone deacetylase (HDAC) inhibitors and Arg deprivation in PDAC cells with low ASS1 expression. We examined HDAC inhibitor panobinostat (PAN) and Arg deprivation in a panel of human PDAC cell lines, in ASS1-high and -knockdown/knockout isogenic models, in both anchorage-dependent and -independent cultures, and in multicellular complex cultures that model the PDAC tumor microenvironment. We examined the effects of combined Arg deprivation and PAN on DNA damage and the protein levels of key DNA repair enzymes. We also evaluated the efficacy of PAN and ADI-PEG20 (an Arg-degrading agent currently in Phase 2 clinical trials) in xenograft models with ASS1-low and -high PDAC tumors.Results: Low ASS1 protein level is a negative prognostic indicator in PDAC. Arg deprivation in ASS1-deficient PDAC cells upregulated asparagine synthetase (ASNS) which redirected aspartate (Asp) from being used for de novo nucleotide biosynthesis, thus causing nucleotide insufficiency and impairing cell cycle S-phase progression. Comprehensively validated, HDAC inhibitors and Arg deprivation showed synthetic lethality in ASS1-low PDAC cells. Mechanistically, combined Arg deprivation and HDAC inhibition triggered degradation of a key DNA repair enzyme C-terminal-binding protein interacting protein (CtIP), resulting in DNA damage and apoptosis. In addition, S-phase-retained ASS1-low PDAC cells (due to Arg deprivation) were also sensitized to DNA damage, thus yielding effective cell death. Compared to single agents, the combination of PAN and ADI-PEG20 showed better efficacy in suppressing ASS1-low PDAC tumor growth in mouse xenograft models.Conclusion: The combination of PAN and ADI-PEG20 is a rational translational therapeutic strategy for treating ASS1-low PDAC tumors through synergistic induction of DNA damage.

Reprogramming of Amino Acid Metabolism in Pancreatic Cancer: Recent Advances and Therapeutic Strategies

“…Mounting studies suggest that concurrent treatment with PEG-ADI and other drugs is a promising therapeutic strategy for treating ASS-low PDAC. Kim et al recently discovered that the histone deacetylase (HDAC) inhibitor panobinostat is synergistically lethal with ADI-PEG20 in ASS1-low pancreatic cancer ( 147 ). Furthermore, the effect of treating ASS-negative PDAC with the combination of PEG-ADI with chemotherapy or radiotherapy has been well-demonstrated.…”

Arginine metabolism: a potential target in pancreatic cancer therapy

“…According to the previous studies, the expression of ASS1 is low or negative in Panc1, AsPC1, and MiaPaca2, but high or positive in BxPC3 and Capan1. [ 14 , 27 ] Besides, ASS1 may also have a tumor suppressor function. [ 27 – 29 ] ASS1 low expression significantly correlated with high-grade pancreatic cancers and the poor prognosis of patients.…”

“…[ 14 , 27 ] Besides, ASS1 may also have a tumor suppressor function. [ 27 – 29 ] ASS1 low expression significantly correlated with high-grade pancreatic cancers and the poor prognosis of patients. [ 27 ] Additionally, it was shown that pancreatic cancers that have a reduced ASS expression were associated with a higher survivin expression, and increased lymph node metastasis and local invasion.…”

“…[ 26 , 30 , 47 ] Furthermore, arginine deprivation could significantly upregulate the expression of asparagine synthetase (ASNS) which redirects aspartate from de novo nucleotide biosynthesis, leading to nucleotide insufficiency and the triggering of cell cycle arrest at the S phase. [ 27 ] Additionally, arginine catabolism is the only source of the production of intracellular NO which can regulate cancer cell proliferation and growth. For instance, a low concentration of NO could stimulate tumor growth, while a high concentration results in cytotoxicity associated with the induction of DNA damage and apoptosis.…”

New insights into molecules and pathways of cancer metabolism and therapeutic implications

“…Arginine accelerates tumorigenesis via the enzyme argininosuccinate synthetase 1 (ASS1) which catalyzes the synthesis of argininosuccinate from citrulline and aspartate, and is the rate‐limiting enzyme in arginine biosynthesis [103] (Figure 3). This enzyme can be targeted for developing arginine deprivation therapy in multiple tumor types.…”