Aim To investigate the effect of 2-deoxy-D-glucose(2-DG)on the sensitivity of leukemia multi-drug resistant K562/ADMcells to adriamycin by inhib-iting glycolytic pathway as well as its molecular mecha-nisms.Methods The leukemia drug-resistant K562/ADM cells and parental K562 cells were used as the target cell models.The cell proliferating activity was assessed with an MTT colorimetric assay,and the gly-colysis including glucose consumption,lactate export, and hexokinase activity was determined by glucose, lactic acid and hexokinase (HK)testing kits.The ex-pression and phosphorylation of mammalian target of rapamycin(mTOR)and glucose transporter-4 (GLUT-4)expression were analyzed by western blot.Results K562/ADM drug-resistant cells possessed higher HK activity,GLUT-4 expression level and aerobic glycolic ability than K562 sensitive cells. 2-DG treatment markedly inhibited HK activity,glucose consumption, and lactate export both in K562 cells and K562/ADM cells,and suppressed the proliferation of the two cells in a time-and concentration-dependent manner.Low concentration of 2-DG or adriamycin could increase the expression and phosphorylation of mTOR.However, the co-administration of 2-DG and adriamycin markedly counteracted adriamycin-mediated enhancement of mTOR expression and phosphorylation and down-regu-lated GLUT-4 expression in K562/ADM cells,and 2-DG dramatically improved the sensitivity of K562/ADM cells to cytotoxicity.Conclusion 2-DG inhibits the proliferation of drug-resistant K562/ADM cells and en-hances the sensitivity to adriamycin by blocking aerobic glycolysis pathway through inhibiting hexokinase activi-ty,counteracting adriamycin-stimulated increased ex-pression and phosphorylation of mTOR and downregu-lating GLUT-4 expression.

Renal tubular secretion mediated by organic anion transporters(OATs)and the multidrug resistance-associated protein 4(MRP4)is an important means of drug and toxin excretion.Unfortunately,there are no biomarkers to evaluate their function.The aim of this study was to identify and characterize an endogenous biomarker of the renal tubular OATs-MRP4 channel.Twenty-six uremic toxins were selected as candidate compounds,of which kynurenic acid was identified as a potential biomarker by assessing the protein-binding ratio and the uptake in OAT1-,OAT3-,and MRP4-overexpressing cell lines.OAT1/3 and MRP4 mediated the transcellular vectorial transport of kynurenic acid in vitro.Serum kynurenic acid concentration was dramatically increased in rats treated with a rat OAT1/3(rOAT1/3)inhibitor and in rOAT1/3 double knockout(rOAT1/3-/-)rats,and the renal concentrations were markedly elevated by the rat MRP4(rMRP4)inhibitor.Kynurenic acid was not filtered at the glomerulus(99％of albumin binding),and was specifically secreted in renal tubules through the OAT1/3-MRP4 channel with an appropriate affinity(Km)(496.7 μM and 382.2 μM for OAT1 and OAT3,respectively)and renal clearance half-life(ti/2)in vivo(3.7±0.7 h).There is a strong correlation in area under the plasma drug concentration-time curve(AUC0-t)between cefmetazole and kynurenic acid,but not with creatinine,after inhibition of rOATs.In addition,the phase of increased kynurenic acid level is earlier than that of creatinine in acute kidney injury process.These results suggest that albumin-bound kynurenic acid is an appropriate endogenous biomarker for adjusting the dosage of drugs secreted by this channel or predicting kidney injury.