Autophagy, Warburg, and Warburg reverse effects in human cancer. Biomed Res Int. 2014;2014:926729. [PMID: 25197670 PMCID: PMC4145381 DOI: 10.1155/2014/926729]

3-bromopyruvate enhanced daunorubicin-induced cytotoxicity involved in monocarboxylate transporter 1 in breast cancer cells

Increasing evidence demonstrates that the hexokinase inhibitor 3-bromopyruvate (3-BrPA) induces the cell apoptotic death by inhibiting ATP generation in human cancer cells. Interestingly, some tumor cell lines are less sensitive to 3-BrPA-induced apoptosis than others. Moreover, the molecular mechanism of 3-BrPA-trigged apoptosis is unclear. In the present study, we examined the effects of 3-BrPA on the viability of the breast cancer cell lines MDA-MB-231 and MCF-7. We further investigated the potential roles of monocarboxylate transporter 1 (MCT1) in drug accumulation and efflux of breast cancer cells. Finally, we explored whether 3-BrPA enhanced daunorubicin (DNR)-induced cytotoxicity through regulation of MCT1 in breast cancer cells. MTT and colony formation assays were used to measure cell viability. Western blot analysis, flow cytometric analysis and fluorescent microscopy were used to determine the molecular mechanism of actions of MCT1 in different breast cancer cell lines. Whole-body bioluminescence imaging was used to investigate the effect of 3-BrPA in vivo. We found that 3-BrPA significantly inhibited cell growth and induced apoptosis in MCF-7 cell line, but not in MDA-MB-231 cells. Moreover, we observed that 3-BrPA efficiently enhanced DNR-induced cytotoxicity in MCF-7 cells by inhibiting the activity of ATP-dependent efflux pumps. We also found that MCT1 overexpression increased the efficacy of 3-BrPA in MDA-MB-231 cells. 3-BrPA markedly suppressed subcutaneous tumor growth in combination with DNR in nude mice implanted with MCF-7 cells. Lastly, our whole-body bioluminescence imaging data indicated that 3-BrPA promoted DNR accumulation in tumors. These findings collectively suggest that 3-BrPA enhanced DNR antitumor activity in breast cancer cells involved MCT-1, suggesting that inhibition of glycolysis could be an effective therapeutic approach for breast cancer treatment.

Cancer metabolism and oxidative stress: Insights into carcinogenesis and chemotherapy via the non-dihydrofolate reductase effects of methotrexate

Methotrexate has been in use as an anti-cancer agent for over 60 years. Though inhibition of dihydrofolate reductase is its best known mechanisms of action, its non-dihydrofolate reductase dependent mechanisms disrupt metabolic pathways resulting in a depletion of NAD(P)H and increasing oxidative stress. These mechanisms highlight a novel dependence of cancer cells on their metabolic abnormalities to buffer oxidative stress and chemotherapeutic agents interfere with these cellular abilities. Mitochondria appear to play a significant role in maintaining cancer cell viability and alterations in metabolism seen in cancer cells aid this mitochondrial ability. Further research is needed to understand the effects of other chemotherapeutic agents on these pathways.

•

Methotrexate inhibits multiple enzymes beyond dihydrofolate reductase.

•

Mitochondria serve a critical role in buffering cellular oxidative stress.

•

Metabolic derangements seen in cancer fuel this mitochondrial rescue function.

•

Methotrexate toxicity occurs secondary to a handicapping of this buffering function.

•

Many chemotherapeutic agents appear to have mechanisms affecting these pathways.