Bioengineered arginase I increases caspase-3 expression of hepatocellular and pancreatic carcinoma cells despite induction of argininosuccinate synthetase-1

BackgroundHepatocellular and pancreatic carcinomas are often auxotrophic for L-arginine, a semi-essential amino acid. The purpose of this study was to investigate cancer cell death using a significantly more active, cobalt-substituted bioengineered arginase.MethodsPanc-1, a human pancreatic carcinoma cell line, and Hep 3B, a human hepatocellular carcinoma cell line, were exposed to L-arginase. Flow cytometry was used to measure expression of Ki-67, caspase-3, and argininosuccinate synthetase-1 (ASS-1) 4 days after treatment. An MTT assay measured proliferation. The Student t test determined statistical significance.ResultsViability decreased by 31% ± 2% for Panc-1 cells (P < .0001) and 34% ± 1% (P < .0001) for Hep 3B cells after treatment. Both cell lines demonstrated a 4-fold increase activated caspase-3 expression after high dose treatment (P < .01), and 5-fold increase in ASS-1 expression (P < .002). Ki-67 expression did not vary in Hep 3B cells but decreased for Panc-1 cells (P < .015). The 50% inhibitory concentration was 8-fold higher for Panc-1 cells than for Hep 3B cells (P < .03).ConclusionIncreased ASS-1 expression by these cells, in order to increase L-arginine concentration, is inadequate, suggesting a mechanism by which arginine depletion can be used in multimodality therapy for arginine-dependent cancers.