Much of the mechanism by which Wnt signaling drives proliferation during oncogenesis is attributed to its regulation of the cell cycle. Here, we show how Wnt/b-catenin signaling directs another hallmark of tumorigenesis, namely Warburg metabolism. Using biochemical assays and fluorescence lifetime imaging microscopy (FLIM) to probe metabolism in vitro and in living tumors, we observe that interference with Wnt signaling in colon cancer cells reduces glycolytic metabolism and results in small, poorly perfused tumors. We identify pyruvate dehydrogenase kinase 1 (PDK1) as an important direct target within a larger gene program for metabolism. PDK1 inhibits pyruvate flux to mitochondrial respiration and a rescue of its expression in Wnt-inhibited cancer cells rescues glycolysis as well as vessel growth in the tumor microenvironment. Thus, we identify an important mechanism by which Wntdriven Warburg metabolism directs the use of glucose for cancer cell proliferation and links it to vessel delivery of oxygen and nutrients.

LEF/TCFs direct the final step in Wnt/β-catenin signalling by recruiting β-catenin to genes for activation of transcription. Ancient, non-vertebrate TCFs contain two DNA binding domains, a High Mobility Group box for recognition of the Wnt Response Element (WRE; 5′-CTTTGWWS-3′) and the C-clamp domain for recognition of the GC-rich Helper motif (5′-RCCGCC-3′). Two vertebrate TCFs (TCF-1/TCF7 and TCF-4/TCF7L2) use the C-clamp as an alternatively spliced domain to regulate cell-cycle progression, but how the C-clamp influences TCF binding and activity genome-wide is not known. Here, we used a doxycycline inducible system with ChIP-seq to assess how the C-clamp influences human TCF1 binding genome-wide. Metabolic pulse-labeling of nascent RNA with 4′Thiouridine was used with RNA-seq to connect binding to the Wnt transcriptome. We find that the C-clamp enables targeting to a greater number of gene loci for stronger occupancy and transcription regulation. The C-clamp uses Helper sites concurrently with WREs for gene targeting, but it also targets TCF1 to sites that do not have readily identifiable canonical WREs. The coupled ChIP-seq/4′Thiouridine-seq analysis identified new Wnt target genes, including additional regulators of cell proliferation. Thus, C-clamp containing isoforms of TCFs are potent transcriptional regulators with an expanded transcriptome directed by C-clamp-Helper site interactions.

BackgroundThere is increasing evidence that oncogenic Wnt signaling directs metabolic reprogramming of cancer cells to favor aerobic glycolysis or Warburg metabolism. In colon cancer, this reprogramming is due to direct regulation of pyruvate dehydrogenase kinase 1 (PDK1) gene transcription. Additional metabolism genes are sensitive to Wnt signaling and exhibit correlative expression with PDK1. Whether these genes are also regulated at the transcriptional level, and therefore a part of a core metabolic gene program targeted by oncogenic WNT signaling, is not known.ResultsHere, we identify monocarboxylate transporter 1 (MCT-1; encoded by SLC16A1) as a direct target gene supporting Wnt-driven Warburg metabolism. We identify and validate Wnt response elements (WREs) in the proximal SLC16A1 promoter and show that they mediate sensitivity to Wnt inhibition via dominant-negative LEF-1 (dnLEF-1) expression and the small molecule Wnt inhibitor XAV939. We also show that WREs function in an independent and additive manner with c-Myc, the only other known oncogenic regulator of SLC16A1 transcription. MCT-1 can export lactate, the byproduct of Warburg metabolism, and it is the essential transporter of pyruvate as well as a glycolysis-targeting cancer drug, 3-bromopyruvate (3-BP). Using sulforhodamine B (SRB) assays to follow cell proliferation, we tested a panel of colon cancer cell lines for sensitivity to 3-BP. We observe that all cell lines are highly sensitive and that reduction of Wnt signaling by XAV939 treatment does not synergize with 3-BP, but instead is protective and promotes rapid recovery.ConclusionsWe conclude that MCT-1 is part of a core Wnt signaling gene program for glycolysis in colon cancer and that modulation of this program could play an important role in shaping sensitivity to drugs that target cancer metabolism.Electronic supplementary materialThe online version of this article (doi:10.1186/s40170-016-0159-3) contains supplementary material, which is available to authorized users.

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Objective We compare validation characteristics of four early warning systems for maternal morbidity. Study Design We used a retrospective cohort of severe maternal morbidity cases between January 2016 and December 2016 compared with a cohort of controls. We determined if the modified early obstetric warning score (MEOWS), maternal early recognition criteria (MERC), modified early warning system (MEWS), or maternal early warning trigger (MEWT) would have alerted. We developed criteria to determine which of these alerts was considered clinically “relevant.” Results We reviewed 79 morbidity cases and 123 controls. MEOWS and MERC were more sensitive than MEWS or MEWT (67.1 and 67.1% vs. 19% and 40.5%, p < 0.001); however, MEWT and MEWS were more specific (88.6% MEWT and 93.5% MEWS vs. 51.2% MEOWS and 60.2% MERC, p < 0.001). In the control population, 70% of MEWT alerts still appeared “relevant” to the clinical scenario in contrast to the MEOWS (32%) or MERC systems (31%). Conclusion There are limited comparative data regarding how early warning systems perform in an American population for maternal morbidity. None of the systems performs with high sensitivity and specificity. High-volume, high-acuity units may decide that the lower sensitivity of the MEWT is relatively acceptable when considering the high false trigger rate of the other more sensitive systems. In addition, triggers in the MEWT system were more likely to be clinically relevant even in cases that did not have severe morbidity.