a, b, Expression analysis by qPCR of Pkm1 and Pkm2 mRNA in tissues from wild-type mice and from four tumour cell lines, normalized to Actb and Rpl13a as housekeeping genes. c, Expression analysis by qPCR of Pkm1 and Pkm2 mRNA in tissues from wild-type mice and from six tumour cell lines. qPCR results were normalized to the housekeeping gene Rpl13a. d, e, The in vivo intratumoral lactate levels in LLC and B16 tumours correspond to the concentrations that have been determined to activate macrophages in vitro. Lactate concentration (mM) in control (DMEM) or LLC-tumour-conditioned medium (unfractionated, <3-kDa fraction and >3-kDa fraction). Most of the lactic acid is present in the <3-kDa fraction (d). The mean in vivo lactic acid concentrations in LLC and B16 tumours were measured using hydrophilic interaction chromatography and mass spectroscopy (e). All relative expression histograms represent three biological replicates displayed as mean ± s.e.m. BAT, brown adipose tissue; WAT, white adipose tissue.