Systemic administration of 3-bromopyruvate reveals its interaction with serum proteins in a rat model

BACKGROUND: 3-bromopyruvate (3-BrPA) is a glycolytic inhibitor that affects cancer cells by targeting energy metabolism. Preclinical reports have established that a 1.75 mM dose of 3-BrPA is effective and sufficient to inhibit tumor growth when administered under a loco-regional approach (intraarterial and intratumoral). This loco-regional therapeutic dose was found to be nontoxic when given systemically as well. Yet, the mechanism underlying this lack of toxicity of 1.75 mM 3-BrPA during systemic delivery is unknown. Here, we investigated the mechanism associated with the lack of organ toxicity when 1.75 mM 3-BrPA was administered systemically using radiolabeled ((14)C)-3-BrPA in Sprague–Dawley rats. FINDINGS: Data obtained from tissue-autoradiography of rats infused with (14)C-3-BrPA showed strong (14)C-signal in tissue sections of various organs except the brain corroborating that 3-BrPA does not cross the blood–brain barrier. Significantly, Hematoxylin & Eosin staining and apoptosis assay of tissue sections positive for (14)C-signal showed no signs of toxicity or apoptosis. Convincingly, the (14)C-signal observed in tissue-autoradiography emanates from 3-BrPA that is non-reactive or non-toxic, hence we further investigated whether the lack of toxicity is due to its interaction or alkylation with serum components. Analysis of serum proteins by 1D and 2D-gel electrophoretic autoradiography showed that (14)C-BrPA selectively binds to peptides of molecular mass ~50-60 kDa. Mass spectrometry data suggested that (14)C-BrPA could interact with alpha1-antitrypsin and a peptide of albuminoid-family. CONCLUSION: Our data indicate that selective interaction of 3-BrPA with serum proteins could contribute to the apparent lack of tissue-toxicity at the indicated close when the drug is given systematically in Sprague–Dawley rats.