A fluorescence-coupled assay for gamma aminobutyric acid (GABA) reveals metabolic stress-induced modulation of GABA content in neuroendocrine cancer

• Published in: PloS one Vol. 9; no. 2; p. e88667
• Main Authors: Ippolito, Joseph E, Piwnica-Worms, David
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 13-02-2014; Public Library of Science (PLoS)
• Subjects: Acids; Adenocarcinoma; Adenocarcinoma - genetics; Adenocarcinoma - metabolism; Adenocarcinoma - mortality; Adenocarcinoma - pathology; Atlases as Topic; Biology; Biotechnology; Cancer; Cancer genetics; Carcinoma, Neuroendocrine - genetics; Carcinoma, Neuroendocrine - metabolism; Carcinoma, Neuroendocrine - mortality; Carcinoma, Neuroendocrine - pathology; Cell growth; Cell Line, Tumor; Cell survival; Cellular stress response; Clear cell-type renal cell carcinoma; Deprivation; E coli; Enzyme Assays; Enzymes; Escherichia coli; Fluorescence; GABA; gamma-Aminobutyric Acid - analysis; gamma-Aminobutyric Acid - metabolism; Gene expression; Gene Expression Regulation, Neoplastic; Genetic aspects; Genomes; Genomics; Glucose - deficiency; Glutamate; Glutamate decarboxylase; Glutamate Decarboxylase - genetics; Glutamate Decarboxylase - metabolism; Glutamate-ammonia ligase; Glutamate-Ammonia Ligase - genetics; Glutamate-Ammonia Ligase - metabolism; Glutamine; Glutamine - deficiency; Humans; Hydrogen-Ion Concentration; Kidney cancer; Kidneys; Male; Mass spectrometry; Medical prognosis; Medicine; Metabolism; Metabolites; Metastasis; Modulation; Neoplasms; Neuroendocrine tumors; NMR; Nuclear magnetic resonance; Oxazines - chemistry; Pathogenesis; Physiology; Polyamines; Prostate; Prostate cancer; Prostatic Neoplasms - genetics; Prostatic Neoplasms - metabolism; Prostatic Neoplasms - mortality; Prostatic Neoplasms - pathology; Scientific imaging; Signal Transduction; Stress; Stress, Physiological - genetics; Stresses; Survival; Survival Analysis; Synthesis; Trends; Tumor cell lines; Tumors; Xanthenes - chemistry; γ-Aminobutyric acid
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0088667

Pathways involved in the synthesis of the neurotransmitter gamma-aminobutyric acid (GABA) have been implicated in the pathogenesis of high grade neuroendocrine (NE) neoplasms as well as neoplasms from a non-NE lineage. Using The Cancer Genome Atlas, overexpression of the GABA synthetic enzyme, glutamate decarboxylase 1 (GAD1), was found to be associated with decreased disease free-survival in prostate adenocarcinoma and decreased overall survival in clear cell renal cell carcinomas. Furthermore, GAD1 was found to be expressed in castrate-resistant prostate cancer cell lines, but not androgen-responsive cell lines. Using a novel fluorescence-coupled enzymatic microplate assay for GABA mediated through reduction of resazurin in a prostate neuroendocrine carcinoma (PNEC) cell line, acid microenvironment-induced stress increased GABA levels while alkaline microenvironment-induced stress decreased GABA through modulation of GAD1 and glutamine synthetase (GLUL) activities. Moreover, glutamine but not glucose deprivation decreased GABA through modulation of GLUL. Consistent with evidence in prokaryotic and eukaryotic organisms that GABA synthesis mediated through GAD1 may play a crucial role in surviving stress, GABA may be an important mediator of stress survival in neoplasms. These findings identify GABA synthesis and metabolism as a potentially important pathway for regulating cancer cell stress response as well as a potential target for therapeutic strategies.