RT Journal Article SR Electronic T1 18F-5-Fluoroaminosuberic Acid as a Potential Tracer to Gauge Oxidative Stress in Breast Cancer Models JF Journal of Nuclear Medicine JO J Nucl Med FD Society of Nuclear Medicine SP 367 OP 373 DO 10.2967/jnumed.116.180661 VO 58 IS 3 A1 Hua Yang A1 Silvia Jenni A1 Milena Colovic A1 Helen Merkens A1 Carlee Poleschuk A1 Isabel Rodrigo A1 Qing Miao A1 Bruce F. Johnson A1 Michael J. Rishel A1 Vesna Sossi A1 Jack M. Webster A1 François Bénard A1 Paul Schaffer YR 2017 UL http://jnm.snmjournals.org/content/58/3/367.abstract AB The cystine transporter (system xC−) is an antiporter of cystine and glutamate. It has relatively low basal expression in most tissues and becomes upregulated in cells under oxidative stress (OS) as one of the genes expressed in response to the antioxidant response element promoter. We have developed 18F-5-fluoroaminosuberic acid (FASu), a PET tracer that targets system xC−. The goal of this study was to evaluate 18F-FASu as a specific gauge for system xC− activity in vivo and its potential for breast cancer imaging. Methods: 18F-FASu specificity toward system xC− was studied by cell inhibition assay, cellular uptake after OS induction with diethyl maleate, with and without anti-xCT small interfering RNA knockdown, in vitro uptake studies, and in vivo uptake in a system xC−–transduced xenograft model. In addition, radiotracer uptake was evaluated in 3 breast cancer models: MDA-MB-231, MCF-7, and ZR-75-1. Results: Reactive oxygen species–inducing diethyl maleate increased glutathione levels and 18F-FASu uptake, whereas gene knockdown with anti-xCT small interfering RNA led to decreased tracer uptake. 18F-FASu uptake was robustly inhibited by system xC− inhibitors or substrates, whereas uptake was significantly higher in transduced cells and tumors expressing xCT than in wild-type HEK293T cells and tumors (P < 0.0001 for cells, P = 0.0086 for tumors). 18F-FASu demonstrated tumor uptake in all 3 breast cancer cell lines studied. Among them, triple-negative breast cancer MDA-MB-231, which has the highest xCT messenger RNA level, had the highest tracer uptake (P = 0.0058 when compared with MCF-7; P < 0.0001 when compared with ZR-75-1). Conclusion: 18F-FASu as a system xC− substrate is a specific PET tracer for functional monitoring of system xC− and OS imaging. By enabling noninvasive analysis of xC− responses in vivo, this biomarker may serve as a valuable target for the diagnosis and treatment monitoring of certain breast cancers.