Although metabolic reprogramming is recognized as a hallmark of tumorigenesis and progression, little is known about metabolic enzymes and oncometabolites that regulate breast cancer metastasis, and very few metabolic molecules have been identified as potential therapeutic targets. In this study, the transketolase (TKT) expression correlated with tumor size in the 4T1/BALB/c syngeneic model. In addition, TKT expression was higher in lymph node metastases compared with primary tumor or normal tissues of patients, and high TKT levels were associated with poor survival. Depletion of TKT or addition of alpha-ketoglutarate (αKG) enhanced the levels of tumor suppressors succinate dehydrogenase and fumarate hydratase (FH), decreasing oncometabolites succinate and fumarate, and further stabilizing HIF prolyl hydroxylase 2 (PHD2) and decreasing HIF1α, ultimately suppressing breast cancer metastasis. Reduced TKT or addition of αKG mediated a dynamic switch of glucose metabolism from glycolysis to oxidative phosphorylation. Various combinations of the TKT inhibitor oxythiamine, docetaxel, and doxorubicin enhanced cell death in triple-negative breast cancer (TNBC) cells. Furthermore, oxythiamine treatment led to increased levels of αKG in TNBC cells. Together, our study has identified a novel TKT-mediated αKG signaling pathway that regulates breast cancer oncogenesis and can be exploited as a modality for improving therapy. These findings uncover the clinical significance of TKT in breast cancer progression and metastasis and demonstrate effective therapy by inhibiting TKT or by adding αKG. .

BackgroundMicroRNAs (miRNAs) are a class of endogenous, small and highly conserved noncoding RNAs that control gene expression either by degradation of target mRNAs or by inhibition of protein translation. They play important roles in cancer progression. A single miRNA can provoke a chain reaction and further affect protein interaction network (PIN). Therefore, we developed a novel integrative approach to identify the functional roles and the regulated PIN of oncomirs.ResultsWe integrated the expression profiles of miRNA and mRNA with the human PIN to reveal miRNA-regulated PIN in specific biological conditions. The potential functions of miRNAs were determined by functional enrichment analysis and the activities of miRNA-regulated PINs were evaluated by the co-expression of protein-protein interactions (PPIs). The function of a specific miRNA, miR-148a, was further examined by clinical data analysis and cell-based experiments. We uncovered several miRNA-regulated networks which were enriched with functions related to cancer progression. One miRNA, miR-148a, was identified and its function is to decrease tumor proliferation and metastasis through its regulated PIN. Furthermore, we found that miR-148a could reduce the invasiveness, migratory and adhesive activities of gastric tumor cells. Most importantly, elevated miR-148a level in gastric cancer tissues was strongly correlated with distant metastasis, organ and peritoneal invasion and reduced survival rate.ConclusionsThis study provides a novel method to identify active oncomirs and their potential functions in gastric cancer progression. The present data suggest that miR-148a could be a potential prognostic biomarker of gastric cancer and function as a tumor suppressor through repressing the activity of its regulated PIN.

Gastric cancer is a leading cause of death worldwide, and patients have an overall 5-year survival rate of less than 10%. Using quantitative proteomic techniques together with microarray chips, we have established comprehensive proteome and transcriptome profiles of the metastatic gastric cancer TMC-1 cells and the noninvasive gastric cancer SC-M1 cell. Our qualitative protein profiling strategy offers the first comprehensive analysis of the gastric cancer cell proteome, identifying 926 and 909 proteins from SC-M1 and TMC-1 cells, respectively. Cleavable isotope-coded affinity tagging analysis allows quantitation of a total of 559 proteins (with a protein false-positive rate of <0.005), and 240 proteins were differentially expressed (>1.3-fold) between the SC-M1 and TMC-1 cells. We identified numerous proteins not previously associated with gastric cancer. Notably, a large subset of differentially expressed proteins was associated with tumor metastasis, including proteins functioning in cell-cell and cell-extracellular matrix (cell-ECM) adhesion, cell motility, proliferation, and tumor immunity. Gene expression profiling by DNA microarray revealed differential expression (of >2-fold) of about 1000 genes. The weak correlation observed between protein and mRNA profiles highlights the important complementarities of DNA microarray and proteomics approaches. These comparative data enabled us to map the disease-perturbed cell-cell and cell-ECM adhesion and Rho GTPase-mediated cytoskeletal pathways. Further validation of a subset of genes suggests the potential use of vimentin and galectin 1 as markers for metastasis. We demonstrate that combining proteomic and genomic approaches not only provides a rapid, robust, and sensitive platform to elucidate the molecular mechanisms underlying gastric cancer metastasis but also may identify candidate diagnostic markers and therapeutic targets.