Project description:Many cancers rely on glycolytic metabolism to fuel rapid proliferation. This has spurred interest in designing drugs that target tumor glycolysis such as AZD3965, a small molecule inhibitor of Monocarboxylate Transporter 1 (MCT1) currently undergoing Phase I evaluation for cancer treatment. Since MCT1 mediates proton-linked transport of monocarboxylates such as lactate and pyruvate across the plasma membrane (Halestrap and Meredith, 2004), AZD3965 is thought to block tumor growth through disruption of lactate transport and glycolysis. Here we show that MCT1 inhibition impairs proliferation of glycolytic breast cancer cells that express MCT4 via disruption of pyruvate rather than lactate export. We found that MCT1 expression is elevated in glycolytic breast tumors and cell lines as well as in malignant breast and lung tissues. High MCT1 expression predicts poor prognosis in breast and lung cancer patients. Stable knockdown and AZD3965-mediated inhibition of MCT1 promote oxidative metabolism. Acute inhibition of MCT1 reduces pyruvate export rate but does not consistently alter lactate transport or glycolytic flux in breast cancer cells that also express MCT4. Despite the lack of glycolysis impairment, MCT1 loss-of-function decreases breast cancer cell proliferation and blocks growth of mammary fat pad xenograft tumors. Our data suggest that MCT1 expression is elevated in glycolytic cancers to promote pyruvate export, which when inhibited enhances oxidative metabolism and reduces proliferation. This study presents an alternative molecular consequence of MCT1 inhibitors that further supports their use as anti-cancer therapeutics. Since MCT1 levels are elevated in glycolytic and malignant breast tumors, we hypothesized that MCT1 may contribute to the Warburg effect metabolic phenotype. To test this hypothesis, we generated whole genome microarray data from breast cancer cell lines either a) expressing a short hairpin (sh)RNA-mediated stable knockdown of MCT1; or b) treated for 24 hours with an MCT1 inhibitor (AZD3965). Scramble shRNA or DMSO were used as controls, and all conditions were analzed in triplicate. The cell lines used â HS578T, SUM149PT, and SUM159PT â are among the most glycolytic in a panel of 31 breast cancer cell lines.
Project description:Many cancers rely on glycolytic metabolism to fuel rapid proliferation. This has spurred interest in designing drugs that target tumor glycolysis such as AZD3965, a small molecule inhibitor of Monocarboxylate Transporter 1 (MCT1) currently undergoing Phase I evaluation for cancer treatment. Since MCT1 mediates proton-linked transport of monocarboxylates such as lactate and pyruvate across the plasma membrane (Halestrap and Meredith, 2004), AZD3965 is thought to block tumor growth through disruption of lactate transport and glycolysis. Here we show that MCT1 inhibition impairs proliferation of glycolytic breast cancer cells that express MCT4 via disruption of pyruvate rather than lactate export. We found that MCT1 expression is elevated in glycolytic breast tumors and cell lines as well as in malignant breast and lung tissues. High MCT1 expression predicts poor prognosis in breast and lung cancer patients. Stable knockdown and AZD3965-mediated inhibition of MCT1 promote oxidative metabolism. Acute inhibition of MCT1 reduces pyruvate export rate but does not consistently alter lactate transport or glycolytic flux in breast cancer cells that also express MCT4. Despite the lack of glycolysis impairment, MCT1 loss-of-function decreases breast cancer cell proliferation and blocks growth of mammary fat pad xenograft tumors. Our data suggest that MCT1 expression is elevated in glycolytic cancers to promote pyruvate export, which when inhibited enhances oxidative metabolism and reduces proliferation. This study presents an alternative molecular consequence of MCT1 inhibitors that further supports their use as anti-cancer therapeutics.
Project description:Abstract: Therapeutic targeting of tumor angiogenesis with VEGF inhibitors results in demonstrable but transitory efficacy in certain human tumors and mouse models of cancer, limited by unconventional forms of adaptive/evasive resistance. In one such mouse model, potent angiogenesis inhibitors elicit compartmental reorganization of cancer cells around remaining blood vessels. The glucose and lactate transporters GLUT1 and MCT4 are induced in distal hypoxic cells in a HIF1α-dependent fashion, indicative of glycolysis. Tumor cells proximal to blood vessels instead express the lactate transporter MCT1, and p-S6, the latter reflecting mTOR signaling. Normoxic cancer cells import and metabolize lactate, resulting in upregulation of mTOR signaling via glutamine metabolism enhanced by lactate catabolism. Thus metabolic symbiosis is established in the face of angiogenesis inhibition, whereby hypoxic cancer cells import glucose and export lactate, while normoxic cells import and catabolize lactate. mTOR signaling inhibition disrupts this metabolic symbiosis, associated with upregulation of the glucose transporter GLUT2.
Project description:Ion balance is critical for membrane polarity, signaling and bioenergesis in cells. Here, we report that proton distribution resets metabolism and alters growth in hematopoietic cells. Multiple oncogenic mutations in acute myeloid leukemia utilize proton partitioning to enhance growth by epigenetically upregulating H+/lactate-co-transporter, MCT4, shuttling protons extracellularly to increase intracellular pH. Secondarily, activity of metabolic enzymes (hexokinase, pyruvate kinase and glucose-6-phosphate dehydrogenase) is increased, raising carbon flux through glycolysis and pentose phosphate pathway necessary for proliferation. MCT4-overexpression in normal hematopoietic stem and progenitor cells increases growth without malignant transformation. Yet, inhibiting MCT4 in AML decreases pHi and carbon flux that improves animal survival and, unexpectedly, elimination of leukemic initiating cells in vivo. AML with increased MCT4 expression have activating histone mark, H3K27ac, in MCT4 promoter where MLL-AF9 and BRD4 directly bind. These data demonstrate the sequential alteration of metabolism through epigenetic activation of proton regulator and point to cytoplasmic alkalization as a growth promoting strategy exploited by malignant cells. Inhibiting this process may diminish the competitive advantage of leukemia and potentially improve AML treatment.
Project description:Merkel cell polyomavirus (MCPyV) is an etiological agent of Merkel cell carcinoma (MCC), a highly aggressive skin cancer. The MCPyV small tumor antigen (ST) is required for maintenance of MCC and can transform normal cells. To gain insight into cellular perturbations induced by MCPyV ST, we performed transcriptome analysis of normal human fibroblasts with inducible expression of ST. MCPyV ST dynamically alters the cellular transcriptome with increased levels of glycolytic genes, including the monocarboxylate lactate transporter SLC16A1 (MCT1). Extracellular flux analysis revealed increased lactate export reflecting elevated aerobic glycolysis in ST expressing cells. Inhibition of MCT1 activity suppressed the growth of MCC cell lines and impaired MCPyV-dependent transformation of IMR90 cells. Both NF-κB and MYC have been shown to regulate MCT1 expression. While MYC was required for MCT1 induction, MCPyV-induced MCT1 levels decreased following knockdown of the NF-κB subunit RelA, supporting a synergistic activity between MCPyV and MYC in regulating MCT1 levels. Several MCC lines had high levels of MYCL and MYCN but not MYC. Increased levels of MYCL was more effective than MYC or MYCN in increasing extracellular acidification in MCC cells. Our results demonstrate the effects of MCPyV ST on the cellular transcriptome and reveal that transformation is dependent, at least in part, on elevated aerobic glycolysis.
Project description:Higher 13C-lactate labeling was seen in the more aggressive tumors, including all triple negative breast cancers. There was a significant correlation between lactate labeling and expression of the monocarboxylate transporter (MCT1), which mediates tumor cell pyruvate uptake, and a weaker correlation with expression of LDHA, which catalyzes label exchange between the injected pyruvate and the endogenous lactate pool.
Project description:Monocarboxylate transporter 1 (MCT1) exhibits essential roles in cellular metabolism and energy supply. Although MCT1 is highly expressed in activated B cells, it is not clear how MCT1-governed monocarboxylates transportation is functionally coupled to antibody production during the glucose metabolism. Here, we report that B cell-lineage deficiency of MCT1 significantly influences the class-switch recombination (CSR), rendering impaired IgG antibody responses in Mct1f/fMb1Cre mice after immunization. Metabolic flux reveals that glucose metabolism is significantly reprogrammed from glycolysis to oxidative phosphorylation in Mct1-deficient B cells upon activation. Consistently, activation-induced cytidine deaminase (AID), is severely suppressed in Mct1-deficient B cells due to the decreased level of pyruvate metabolite. Mechanistically, MCT1 is required to maintain the optimal concentration of pyruvate to secure the sufficient acetylation of H3K27 for the elevated transcription of AID in activated B cells. Clinically, we found that MCT1 expression levels are significantly upregulated in systemic lupus erythematosus patients, and Mct1 deficiency can alleviate the symptoms of bm12-induced murine lupus model. Collectively, these results demonstrate that MCT1-mediated pyruvate metabolism is required for IgG antibody CSR through an epigenetic dependent AID transcription, revealing MCT1 as a potential target for vaccine development and SLE disease treatment.
Project description:We have hypothesized that carbonic anhydrases (CAs) play a role in stabilizing both intracellular and extracellular pH to a value that favors cancer progression and metastasis. This is likely in cooperation with the ion transport family. Here, we examined the expression pattern of selected ion transporters, glucose transporters, and carbonic anhydrases in a triple negative cell model of human breast cancer (UFH-001) and the effect of hypoxia. Heat map analysis of RNA transcripts from normoxic and hypoxic cells were significantly different. Additionally, our results show that transcription of the MCT1 monocarboxylate transporter, but not that of MCT4, was sensitive to hypoxia. Both MCT1 and MCT4 were robustly expressed at the protein level, but neither were significantly upregulated by hypoxia. Only low levels of the vATPase and NHE1 transcripts were detected, which is consistent with little to no detectable signal at the protein level. Our data also show high transcript levels of the GLUT1-glucose transporter, CAII and CAIX. Only GLUT1 and CAIX transcription were significantly increased by exposure to hypoxia. CAXII transcripts levels were very low, confirming the lack of expression at the protein level. Yet, CAXII transcription was significantly increased by hypoxia. Overall protein levels of our proteins of interest matched transcription patterns. These studies show a coordinate expression at both the transcriptional and translational levels of the monocarboxylate transporters, the GLUT1 transporter and CAIX in the aggressive triple negative UFH-001 breast cancer cells.
Project description:Gene expression levels were determined with control or MCT4 knockdown pancreatic cancer cells. MiaPaca2, Capan-2, and PL45 cells were transfected with non-specific or MCT4-specific RNAi. RNA was harvested at 72 hours post transfection and analyzed on Illumina microarrays.
Project description:Lactate is the most abundant circulating metabolic intermediate in mammals and an important energy source for many organs. To use lactate as a fuel, it must be oxidized to pyruvate for entry into the TCA cycle. It is usually described that this reaction occurs in the cytosol and requires the mitochondrial pyruvate carrier (MPC) for pyruvate transport into the mitochondria. Here, using 13C stable isotope tracing, we report that lactate can be oxidized in the heart tissue of mice even when the MPC is genetically deleted. MPC-independent lactate import and oxidation within mitochondria is dependent upon the monocarboxylate transporter 1 (MCT1/ Slc16a1). Mitochondria isolated from Mct1iCKO hearts have impaired respiration on lactate but not pyruvate. Lactate import coupled to mitochondrial lactate dehydrogenase activity functions as an electron shuttle which can produce NADH sufficient for respiration even when the TCA cycle is blocked. Cardiac-specific loss of MCT1 leads to rapid decompensation into heart failure with reduced ejection fraction in response to diverse cardiac injuries. Thus, we identify a new mitochondrial electron shuttle that enables the oxidation of lactate and is required to support cardiac energetics under stress conditions.