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Cancer Res. 2014 Feb 1;74(3):896-907. doi: 10.1158/0008-5472.CAN-13-1702. Epub 2013 Nov 27.

Prognostic and therapeutic impact of argininosuccinate synthetase 1 control in bladder cancer as monitored longitudinally by PET imaging.

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1
Authors' Affiliations: Barts Cancer Institute-a Cancer Research UK Center of Excellence, John Vane Science Center, Queen Mary University of London; Department of Medicine, Imperial College, Charing Cross Campus; St Bartholomew's Hospital, Barts Health NHS Trust, West Smithfield, London; Wellcome Trust Center for Human Genetics, Oxford; Cancer Research UK Cambridge Research Institute, Li Ka Shing Center; Hutchison/MRC Research Center, University of Cambridge, Medical Research Council Cancer Unit; Pharmacometrics Ltd., Cambridge; Dundee Cancer Center, University of Dundee, Ninewells Hospital, Dundee, United Kingdom; Laboratory of Cancer Genetics and Translational Oncology, S Croce General Hospital, Cuneo, Italy; Department of Structural Biology, Medical University of Lodz, Lodz, Poland; Polaris Group, San Diego, California; Department of Pathology, Chi-Mei Medical Center; Department of Biotechnology, Southern Taiwan University of Science and Technology, Tainan, Taiwan; and National Institute of Cancer Research, National Health Research Institutes, Tainan, Taiwan.

Abstract

Targeted therapies have yet to have significant impact on the survival of patients with bladder cancer. In this study, we focused on the urea cycle enzyme argininosuccinate synthetase 1 (ASS1) as a therapeutic target in bladder cancer, based on our discovery of the prognostic and functional import of ASS1 in this setting. ASS1 expression status in bladder tumors from 183 Caucasian and 295 Asian patients was analyzed, along with its hypothesized prognostic impact and association with clinicopathologic features, including tumor size and invasion. Furthermore, the genetics, biology, and therapeutic implications of ASS1 loss were investigated in urothelial cancer cells. We detected ASS1 negativity in 40% of bladder cancers, in which multivariate analysis indicated worse disease-specific and metastasis-free survival. ASS1 loss secondary to epigenetic silencing was accompanied by increased tumor cell proliferation and invasion, consistent with a tumor-suppressor role for ASS1. In developing a treatment approach, we identified a novel targeted antimetabolite strategy to exploit arginine deprivation with pegylated arginine deiminase (ADI-PEG20) as a therapeutic. ADI-PEG20 was synthetically lethal in ASS1-methylated bladder cells and its exposure was associated with a marked reduction in intracellular levels of thymidine, due to suppression of both uptake and de novo synthesis. We found that thymidine uptake correlated with thymidine kinase-1 protein levels and that thymidine levels were imageable with [(18)F]-fluoro-L-thymidine (FLT)-positron emission tomography (PET). In contrast, inhibition of de novo synthesis was linked to decreased expression of thymidylate synthase and dihydrofolate reductase. Notably, inhibition of de novo synthesis was associated with potentiation of ADI-PEG20 activity by the antifolate drug pemetrexed. Taken together, our findings argue that arginine deprivation combined with antifolates warrants clinical investigation in ASS1-negative urothelial and related cancers, using FLT-PET as an early surrogate marker of response.

PMID:
24285724
DOI:
10.1158/0008-5472.CAN-13-1702
[Indexed for MEDLINE]
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