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In recent times, researchers working on tumor metabolism have paid increasing attention to the tumor microenvironment. Emerging evidence has confirmed that epigenetic modifications of cancer‑associated fibroblasts (CAFs) alters the characteristics of glucose metabolism to achieve a symbiotic relationship with the cancer cells. Epigallocatechin‑3‑gallate (EGCG) exerts anti‑tumor effects via a variety of mechanisms, although the underlying mechanism that accounts for the effects of EGCG on glucose metabolic alterations of CAFs have yet to be elucidated. In the present study, through co‑culture with colorectal cancer (CRC) cells, human intestinal fibroblasts were transformed into CAFs, and exhibited enhanced aerobic glycolysis. Induced CAFs were able to enhance the proliferation, migration and invasion of CRC cells in vitro . EGCG treatment led to direct inhibition of the proliferation and migration of CRC cells; furthermore, EGCG treatment of CAFs suppressed their tumor‑promoting capabilities by inhibiting their glycolytic activity. Blocking the lactic acid efflux of CAFs with a monocarboxylate transporter 4 (MCT4) inhibitor or through silencing MCT4 could also suppress their tumor‑promoting capabilities, indicating that lactate fulfills an important role in the metabolic coupling that occurs between CAFs and cancer cells. Taken together, the results of the present study showed that EGCG targeting of the metabolism of tumor stromal cells provided a safe and effective strategy of anti‑cancer therapy.

The synthesis of a mitochondria-targeted derivative of the classical mitochondrial uncoupler carbonyl cyanide-m-chlorophenylhydrazone (CCCP) by alkoxy substitution of CCCP with n-decyl(triphenyl)phosphonium cation yielded mitoCCCP, which was able to inhibit the uncoupling action of CCCP, tyrphostin A9 and niclosamide on rat liver mitochondria, but not that of 2,4-dinitrophenol, at a concentration of 1-2 μM. MitoCCCP did not uncouple mitochondria by itself at these concentrations, although it exhibited uncoupling action at tens of micromolar concentrations. Thus, mitoCCCP appeared to be a more effective mitochondrial recoupler than 6-ketocholestanol. Both mitoCCCP and 6-ketocholestanol did not inhibit the protonophoric activity of CCCP in artificial bilayer lipid membranes, which might compromise the simple proton-shuttling mechanism of the uncoupling activity on mitochondria., Competing Interests: The authors have declared that no competing interests exist.

Tetrahydrobiopterin (BH4) is a required cofactor for the synthesis of NO by endothelial nitric oxide synthase (eNOS), and endothelial BH4 bioavailability is a critical factor in regulating the balance between NO and superoxide production (eNOS coupling). Biosynthesis of BH4 is determined by the activity of GTP-cyclohydrolase I (GTPCH). However, BH4 levels may also be influenced by oxidation, forming 7,8-dihydrobiopterin (BH2), which promotes eNOS uncoupling. Conversely, dihydrofolate reductase (DHFR) can regenerate BH4 from BH2, but whether DHFR is functionally important in maintaining eNOS coupling remains unclear. To investigate the mechanism by which DHFR might regulate eNOS coupling in vivo, we treated wild-type, BH4-deficient (hph-1), and GTPCH-overexpressing (GCH-Tg) mice with methotrexate (MTX), to inhibit BH4 recycling by DHFR. MTX treatment resulted in a striking elevation in BH2 and a decreased BH4:BH2 ratio in the aortas of wild-type mice. These effects were magnified in hph-1 but diminished in GCH-Tg mice. Attenuated eNOS activity was observed in MTX-treated hph-1 but not wild-type or GCH-Tg mouse lung, suggesting that inhibition of DHFR in BH4-deficient states leads to eNOS uncoupling. Taken together, these data reveal a key role for DHFR in regulating the BH4 vs BH2 ratio and eNOS coupling under conditions of low total biopterin availability in vivo., (Copyright © 2011 Elsevier Inc. All rights reserved.)