a, b, Representative chromatograms of (a) CP-CML and (b) BC-CML plasma samples derivatized with the keto acid-reactive OPD. Each OPD–keto acid peak was assigned as indicated. KG, α-ketoglutarate; PYR, pyruvate; KIV, keto-isovalerate; KIC, keto-isocaproate; KMV, keto-methylvalerate; IS, internal standard for keto acid analysis (OPD–α-ketovalerate). c, d, Plasma and intracellular branched-chain keto acid levels in CP- and BC-CML. c, d, Blood plasma fractions from leukaemic mice (c) or 5 × 106 live leukaemia cells purified by fluorescence-activated cell sorting (d) were methanol-extracted and dried under a vacuum. The dried extracts were labelled with OPD, extracted with ethyl acetate and analysed using an HPLC system equipped with a fluorescence detector. Open and closed bars indicate CP-CML (plasma, n = 9; intracellular, n = 5) and BC-CML (plasma, n = 10; intracellular, n = 6) specimens, respectively. *P < 0.05. Error bars, s.e.m. e, Molar amount of intracellular BCAAs and BCKAs in primary mouse BC-CML cells. The amount of each organic acid per one million cells was estimated using calibration curves obtained with reference standards for each compound. ‘%KA/AA’ shows the amount of a BCKA relative to the corresponding BCAA species.