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Human carbonyl reductase 1 (CBR1) converts the antitumor drug and anthracycline daunorubicin (DNR) into the alcohol metabolite daunorubicinol (DNROL) with significantly reduced antitumor activity and cardiotoxicity, and this limits the clinical use of DNR. Inhibition of CBR1 can thus increase the efficacy and decrease the toxicity of DNR. Here we report that (2)-epigallocatechin gallate (EGCG) from green tea is a promising inhibitor of CBR1. EGCG directly interacts with CBR1 and acts as a noncompetitive inhibitor with respect to the cofactor reduced nicotinamide adenine dinucleotide phosphate and the substrate isatin. The inhibition is dependent on the pH, and the gallate moiety of EGCG is required for activity. Molecular modeling has revealed that EGCG occupies the active site of CBR1. Furthermore, EGCG specifically enhanced the antitumor activity of DNR against hepatocellular carcinoma SMMC7721 cells expressing high levels of CBR1 and corresponding xenografts. We also demonstrated that EGCG could overcome the resistance to DNR by Hep3B cells stably expressing CBR1 but not by RNA interference of CBR1-HepG2 cells. The level of the metabolite DNROL was negatively correlated with that of EGCG in the cell extracts. Finally, EGCG decreased the cardiotoxicity of DNR in a human carcinoma xenograft model with both SMMC7721 and Hep3B cells in mice. Conclusion: These results strongly suggest that EGCG can inhibit CBR1 activity and enhance the effectiveness and decrease the cardiotoxicity of the anticancer drug DNR. These findings also indicate that a combination of EGCG and DNR might represent a novel approach for hepatocellular carcinoma therapy or chemoprevention. (HEPATOLOGY 2010;52:703-714) H epatocellular carcinoma (HCC) is one of the most common malignancies worldwide.

Aims/hypothesis More than 90% of Chinese familial early-onset type 2 diabetes mellitus is genetically unexplained. To investigate the molecular aetiology, we identified and characterised whether mutations in the KCNJ11 gene are responsible for these families. Methods KCNJ11 mutations were screened for 96 familial early-onset type 2 diabetic probands and their families. Functional significance of the identified mutations was confirmed by physiological analysis, molecular modelling and population survey. Results Three novel KCNJ11 mutations, R27H, R192H and S116F117del, were identified in three families with early-onset type 2 diabetes mellitus. Mutated KCNJ11 with R27H or R192H markedly reduced ATP sensitivity (E23K>R27H>C42R>R192H>R201H), but no ATP-sensitive potassium channel currents were detected in the loss-of-function S116F117del channel in vitro. Molecular modelling indicated that R192H had a larger effect on the channel ATP-binding pocket than R27H, which may qualitatively explain why the ATP sensitivity of the R192H mutation is seven times less than R27H. The shape of the S116F117del channel may be compressed, which may explain why the mutated channel had no currents. Discontinuation of insulin and implementation of sulfonylureas for R27H or R192H carriers and continuation/switch to insulin therapy for S116F117del carriers resulted in good glycaemic control. Conclusions/interpretation Our results suggest that genetic diagnosis for the KCNJ11 mutations in familial early-onset type 2 diabetes mellitus may help in understanding the molecular aetiology and in providing more personalised treatment for these specific forms of diabetes in Chinese and other Asian patients.

Tuberculosis (TB) continues to be a major cause of morbidity and mortality worldwide. The increasing emergence and spread of drug‐resistant TB poses a significant threat to disease control and calls for the urgent development of new drugs. The tryptophan biosynthetic pathway plays an important role in the survival of Mycobacterium tuberculosis. Thus, indole‐3‐glycerol phosphate synthase (IGPS), as an essential enzyme in this pathway, might be a potential target for anti‐TB drug design. In this study, we deduced the structure of IGPS of M. tuberculosis H37Rv by using homology modeling. On the basis of this deduced IGPS structure, screening was performed in a search for novel inhibitors, using the Maybridge database containing the structures of 60 000 compounds. ATB107 was identified as a potential binding molecule; it was tested, and shown to have antimycobacterial activity in vitro not only against the laboratory strain M. tuberculosis H37Rv, but also against clinical isolates of multidrug‐resistant TB strains. Most MDR‐TB strains tested were susceptible to 1 μg·mL−1 ATB107. ATB107 had little toxicity against THP‐1 macrophage cells, which are human monocytic leukemia cells. ATB107, which bound tightly to IGPS in vitro, was found to be a potent competitive inhibitor of the substrate 1‐(o‐carboxyphenylamino)‐1‐deoxyribulose‐5′‐phosphate, as shown by an increased Km value in the presence of ATB107. The results of site‐directed mutagenesis studies indicate that ATB107 might inhibit IGPS activity by reducing the binding affinity for substrate of residues Glu168 and Asn189. These results suggest that ATB107 is a novel potent inhibitor of IGPS, and that IGPS might be a potential target for the development of new anti‐TB drugs. Further evaluation of ATB107 in animal studies is warranted.

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