EPR tumor oxygen imaging following administration of exogenous pyruvate. (a–c) EPR oxygen imaging of subcutaneous Hs766t (a), MiaPaCa-2 (b), and SU.86.86 (c) tumors pre- and post (10–60 min) IV pyruvate administration. Representative T2 weighted anatomical MR imaging and pO2 maps are provided N = 4 biological replicates per tumor type. (d) Temporal changes of mean pO2 and (e) percent hypoxic fraction (<10 mmHg) of pyruvate-treated PDAC tumors. Data presented as mean ± S.D. Proposed histological predictive biomarkers for pyruvate sensitivity. (f) Histological staining of monocarboxylate transporter (MCT) 1 expression in PDAC subcutaneous tumors. Corresponding images of positive pixel membrane staining are included. Human PDAC tissue microarray stained for MCT1 (g), MCT4 (h), and pyruvate kinase isoform M2 (i). (j) Distribution of percent positivity across well-differentiated human PDAC tissue cores. Scale bar = 100 μM. See also Additional file 1: Figure S5.