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ASS1 and ASL suppress growth in clear cell renal cell carcinoma via altered nitrogen metabolism
Sanika Khare1, Laura C Kim1, Graham Lobel1
1Abramson Family Cancer Research Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA.
Background:
Kidney cancer is a common adult malignancy in the USA. Clear cell renal cell carcinoma (ccRCC), the predominant subtype of kidney cancer, is characterized by widespread metabolic changes. Urea metabolism is one such altered pathway in ccRCC. The aim of this study was to elucidate the contributions of urea cycle enzymes, argininosuccinate synthase 1 (ASS1), and argininosuccinate lyase (ASL) towards ccRCC progression.
Methods:
We employed a combination of computational, genetic, and metabolomic tools along with in vivo animal models to establish a tumor-suppressive role for ASS1 and ASL in ccRCC.
Results:
We show that the mRNA and protein expression of urea cycle enzymes ASS1 and ASL are reduced in ccRCC tumors when compared to the normal kidney. Furthermore, the loss of ASL in HK-2 cells (immortalized renal epithelial cells) promotes growth in 2D and 3D growth assays, while combined re-expression of ASS1 and ASL in ccRCC cell lines suppresses growth in 2D, 3D, and in vivo xenograft models. We establish that this suppression is dependent on their enzymatic activity. Finally, we demonstrate that conservation of cellular aspartate, regulation of nitric oxide synthesis, and pyrimidine production play pivotal roles in ASS1+ASL-mediated growth suppression in ccRCC.
Conclusions:
ccRCC tumors downregulate the components of the urea cycle including the enzymes argininosuccinate synthase 1 (ASS1) and argininosuccinate lyase (ASL). These cytosolic enzymes lie at a critical metabolic hub in the cell and are involved in aspartate catabolism and arginine and nitric oxide biosynthesis. Loss of ASS1 and ASL helps cells redirect aspartate towards pyrimidine synthesis and support enhanced proliferation. Additionally, reduced levels of ASS1 and ASL might help regulate nitric oxide (NO) generation and mitigate its cytotoxic effects. Overall, our work adds to the understanding of urea cycle enzymes in a context-independent of ureagenesis, their role in ccRCC progression, and uncovers novel potential metabolic vulnerabilities in ccRCC.
Insights
Kidney cancer cells downregulate urea cycle enzymes argininosuccinate synthase 1 (ASS1) and argininosuccinate lyase (ASL). Restoring these enzymes suppresses tumor growth, revealing new therapeutic targets for clear cell renal cell carcinoma (ccRCC).
Area of Science:
- Oncology
- Metabolic pathways
- Cancer biology
Background:
- Kidney cancer, particularly clear cell renal cell carcinoma (ccRCC), exhibits significant metabolic alterations.
- Urea metabolism is identified as one such altered pathway in ccRCC progression.
Purpose of the Study:
- To investigate the role of urea cycle enzymes, specifically argininosuccinate synthase 1 (ASS1) and argininosuccinate lyase (ASL), in ccRCC progression.
- To elucidate the tumor-suppressive functions of ASS1 and ASL in ccRCC.
Main Methods:
- Utilized a combination of computational, genetic, and metabolomic approaches.
- Employed in vivo animal models and cell-based assays (2D and 3D growth).
- Assessed mRNA and protein expression levels of ASS1 and ASL.
Main Results:
- Reduced expression of ASS1 and ASL observed in ccRCC tumors compared to normal kidney tissue.
- Loss of ASL promoted cell growth, while re-expression of ASS1 and ASL suppressed ccRCC cell proliferation in vitro and in vivo.
- Growth suppression was dependent on enzymatic activity, involving aspartate conservation, nitric oxide synthesis regulation, and pyrimidine production.
Conclusions:
- Downregulation of ASS1 and ASL is a key feature of ccRCC, contributing to tumor progression.
- These enzymes play a critical role in metabolic regulation, influencing aspartate flux towards pyrimidine synthesis and nitric oxide generation.
- The findings uncover potential metabolic vulnerabilities and novel therapeutic targets for ccRCC.
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