GPT and neoplasm: Ex vivo validation confirmed these findings, showing both significantly elevated absolute L/A concentration ratios, due to significantly increased lactate pools (Supplementary Figure S1), and LDH/GPT ratios in tumor tissue extracts compared to normal liver extracts in 1H spectroscopy (Fig. 2a, meantumor 4.83 ± 1.36, n = 17; meancontrol 3.24 ± 0.17; n = 4; Mann–Whitney-U-test-p = 0.009) and in enzyme activity assays (Fig. 2b, meantumor 8.48 ± 5.04, n = 17; meancontrol 2.81 ± 0.33; n = 4; Mann–Whitney-U-test-p = 0.001).