Monocarboxylate transporter-1 (MCT-1) inhibitors screened from autodisplayed FV-antibody library.

Monocarboxylate transporter-1 (MCT-1) inhibitors were screened from the Fv-antibody library, which contained complementary determining region 3 with randomized amino acid sequences (11 residues) through site-directed mutagenesis. Fv-antibodies against MCT-1 were screened from the autodisplayed Fv-antibody library. Two clones were screened, and the binding affinity (KD) against MCT-1 was estimated using flow cytometry. The screened Fv-antibodies were expressed as soluble fusion proteins (Fv-1 and Fv-2) and the KD for MCT-1 was estimated using the SPR biosensor. The inhibitory activity of the expressed Fv-antibodies was observed in HEK293T and Jurkat cell lines by measuring intracellular pH and lactate accumulation. The level of cell viability in HEK293T and Jurkat cell lines was decreased by the inhibitory activity of the expressed Fv-antibodies. The binding properties of the Fv-antibodies to MCT-1 were analyzed using molecular docking simulations. Overall, the results showed that the screened Fv-antibodies against MCT-1 from the Fv-antibody library had high binding affinity and inhibitory activity against MCT-1, which could be used as potential therapeutic drug candidates for the MCT-1 inhibitor.

Visualizing reactive astrocyte-neuron interaction in Alzheimer's disease using 11C-acetate and 18F-FDG.

Reactive astrogliosis is a hallmark of Alzheimer's disease (AD). However, a clinically validated neuroimaging probe to visualize the reactive astrogliosis is yet to be discovered. Here, we show that PET imaging with 11C-acetate and 18F-fluorodeoxyglucose (18F-FDG) functionally visualizes the reactive astrocyte-mediated neuronal hypometabolism in the brains with neuroinflammation and AD. To investigate the alterations of acetate and glucose metabolism in the diseased brains and their impact on the AD pathology, we adopted multifaceted approaches including microPET imaging, autoradiography, immunohistochemistry, metabolomics, and electrophysiology. Two AD rodent models, APP/PS1 and 5xFAD transgenic mice, one adenovirus-induced rat model of reactive astrogliosis, and post-mortem human brain tissues were used in this study. We further curated a proof-of-concept human study that included 11C-acetate and 18F-FDG PET imaging analyses along with neuropsychological assessments from 11 AD patients and 10 healthy control subjects. We demonstrate that reactive astrocytes excessively absorb acetate through elevated monocarboxylate transporter-1 (MCT1) in rodent models of both reactive astrogliosis and AD. The elevated acetate uptake is associated with reactive astrogliosis and boosts the aberrant astrocytic GABA synthesis when amyloid-ß is present. The excessive astrocytic GABA subsequently suppresses neuronal activity, which could lead to glucose uptake through decreased glucose transporter-3 in the diseased brains. We further demonstrate that 11C-acetate uptake was significantly increased in the entorhinal cortex, hippocampus and temporo-parietal neocortex of the AD patients compared to the healthy controls, while 18F-FDG uptake was significantly reduced in the same regions. Additionally, we discover a strong correlation between the patients' cognitive function and the PET signals of both 11C-acetate and 18F-FDG. We demonstrate the potential value of PET imaging with 11C-acetate and 18F-FDG by visualizing reactive astrogliosis and the associated neuronal glucose hypometablosim for AD patients. Our findings further suggest that the acetate-boosted reactive astrocyte-neuron interaction could contribute to the cognitive decline in AD.

Monocarboxylate Transporter 1 May Benefit Cerebral Ischemia via Facilitating Lactate Transport From Glial Cells to Neurons.

Monocarboxylate transporter 1 (MCT1) is expressed in glial cells and some populations of neurons. MCT1 facilitates astrocytes or oligodendrocytes (OLs) in the energy supplement of neurons, which is crucial for maintaining the neuronal activity and axonal function. It is suggested that MCT1 upregulation in cerebral ischemia is protective to ischemia/reperfusion (I/R) injury. Otherwise, its underlying mechanism has not been clearly discussed. In this review, it provides a novel insight that MCT1 may protect brain from I/R injury via facilitating lactate transport from glial cells (such as, astrocytes and OLs) to neurons. It extensively discusses (1) the structure and localization of MCT1; (2) the regulation of MCT1 in lactate transport among astrocytes, OLs, and neurons; and (3) the regulation of MCT1 in the cellular response of lactate accumulation under ischemic attack. At last, this review concludes that MCT1, in cerebral ischemia, may improve lactate transport from glial cells to neurons, which subsequently alleviates cellular damage induced by lactate accumulation (mostly in glial cells), and meets the energy metabolism of neurons.

Prognostic implications of combined high expression of CD47 and MCT1 in breast cancer: a retrospective study during a 10-year period.

Background: Clinical outcome after surgery of breast cancer needs more prognostic markers to predict currently. Cluster of differentiation 47 (CD47), due to its overexpression in various tumors and ability to inhibit phagocytosis, has been identified as a new immune checkpoint. Monocarboxylate transporter 1 (MCT1) is a protein involved in the immunomodulatory activities of the tumor microenvironment (TME) by maintaining the pH through aerobic glycolysis. Methods: We explored the expression of CD47 and MCT1 in breast invasive ductal carcinoma specimens to determine their association with prognosis. A total of 137 breast invasive ductal carcinoma tissues were collected for CD47 and MCT1 immunohistochemical staining. Results: Statistically analyzed, our study first indicated that in both univariate and multivariate analyses, the coexpression of CD47 and MCT1 was an independent prognostic factor for a poor 10-year overall survival rate (10-OS) and 10-year progression-free survival rate (10-DFS) (P<0.05). In addition, the combined high expression of these two markers also led to worse OS and PFS rates in the TNM (II + III), histologic grade (I + II), HER2 overexpression and basal-like subgroups. High expression of CD47 and MCT1 and combined high expression of CD47 and MCT1 were associated with clinicopathological parameters, such as histological grade, TNM stage, death status, and recurrence status in breast cancer patients. However, in the multivariate survival analysis, high expression of CD47 alone was not an independent prognostic factor for the 10-OS or the 10-DFS (P=0.104; P=0.153), and high expression of MCT1 alone was not an independent predictor for a poor 10-DFS (P=0.177) either. Conclusions: The coexpression of CD47 and MCT1 can serve as a prognostic biomarker leading to poor survival and an increased risk for recurrence, and this novel information could help guide the development of adjuvant therapy for breast cancer.

Pyruvate Supplementation Can Prevent HIIE-induced Metabolic Acidosis and Increase the Expression of MCT1/MCT4 in Skeletal Muscles of Rats / 中国生物化学与分子生物学报

As one of the causes of exercise-induced fatigue, exercise-induced metabolic acidosis has attracted much attention. The effect of pyruvate supplementation on exercise-induced metabolic acidosis is rarely reported, and its mechanism has not been fully elucidated. Monocarboxylate transporters (MCTs) play an important role in the maintenance of the acid-base balance, but it is not clear whether pyruvate can alleviate acidosis by increasing the expression of MCTs. In this study, pyruvate (616 mg/kg/day) was supplemented to rats for one week, and then acute HIIE was performed. The HIIE protocol comprised 13 repeats of a 60 s sprint session at 110% VO

Oligodendrocyte Dysfunction in Amyotrophic Lateral Sclerosis: Mechanisms and Therapeutic Perspectives.

Myelin is the lipid-rich structure formed by oligodendrocytes (OLs) that wraps the axons in multilayered sheaths, assuring protection, efficient saltatory signal conduction and metabolic support to neurons. In the last few years, the impact of OL dysfunction and myelin damage has progressively received more attention and is now considered to be a major contributing factor to neurodegeneration in several neurological diseases, including amyotrophic lateral sclerosis (ALS). Upon OL injury, oligodendrocyte precursor cells (OPCs) of adult nervous tissue sustain the generation of new OLs for myelin reconstitution, but this spontaneous regeneration process fails to successfully counteract myelin damage. Of note, the functions of OPCs exceed the formation and repair of myelin, and also involve the trophic support to axons and the capability to exert an immunomodulatory role, which are particularly relevant in the context of neurodegeneration. In this review, we deeply analyze the impact of dysfunctional OLs in ALS pathogenesis. The possible mechanisms underlying OL degeneration, defective OPC maturation, and impairment in energy supply to motor neurons (MNs) have also been examined to provide insights on future therapeutic interventions. On this basis, we discuss the potential therapeutic utility in ALS of several molecules, based on their remyelinating potential or capability to enhance energy metabolism.

Effect of monocarboxylate transporter-1 on the biological behavior of iodine-refractory thyroid carcinoma.

BACKGROUND: Differentiated thyroid cancer (DTC) is the most common thyroid tumor, and the cells of DTC patients can lose the ability to differentiate in their natural state or during treatment and develop radioiodine-refractory DTC (RAI-R DTC), resulting in increased malignancy. Monocarboxylate transporter-1 (MCT1 ) is positively correlated with the level of malignant of various tumors, and its expression in RAI-R DTC cells is correlated with their biological cell traits. METHODS: Data from 14 iodine-refractory thyroid carcinoma patients were collected, and the effective radioiodine treatment group was used as the control group. The expression of MCT1 in iodine-refractory thyroid carcinoma and its effect on biological behaviors was observed and the molecular mechanism underlying RAI-R DTC was investigated to determine the cause of the loss of sensitivity of DTC to radioactive iodine using Immunohistochemical staining, Western blot, transwell assay, wound healing assay, flow cytogram assay. RESULTS: Compared to radioiodine-sensitive DTC (RAI-DTC), which was responded to iodine treatment, MCT1 was highly expressed in RAI-R DTC cells. The overexpression or inhibition of MCT1 altered the biological characteristics of papillary thyroid carcinoma (TPC-1) cells. The overexpression of MCT1 in TPC-1 cells increased the invasive, proliferative, and migratory abilities of the cells. Conversely, the downregulation of MCT1 decreased the invasive, proliferative and migratory abilities of the cells. CONCLUSIONS: The expression of MCT1 was enhanced in RAI-R DTC cells. MCT1 appears to be closely related to the invasive metastasis of RAI-R DTC cells, and it may be the cause of the loss of the iodine uptake ability of RAI-R DTC.

High expression of monocarboxylate transporter 4 (MCT 4), but not MCT 1, predicts poor prognosis in patients with non-small cell lung cancer.

BACKGROUND: The monocarboxylate transporter (MCT) family especially MCT1 and MCT4 have been recognized to play an important role in lactate transport, a key glycolytic product. The expression of MCT1 and MCT4 expression was previously found to be related to poor outcome in various cancer types. In this study, we investigated the expression status of MCT1 and MCT4 and their relationship with prognosis in non-small cell lung cancer (NSCLC). METHODS: Expression of MCT4 and MCT1 in NSCLC tumor and adjacent lung tissues were detected by immunohistochemistry. Kaplan-Meier plots were used to evaluate two proteins' prognostic role, and the log-rank test obtained the P value. For multivariate analysis, the Cox proportional-hazards regression method was performed. RESULTS: High MCT4 and MCT1 expression was observed in cancer cells, with a rate of 45% for MCT4 versus 15% for MCT1 among all NSCLC patients. High expression of MCT4, and not MCT1, was associated with worse overall survival (OS) [hazard ratio (HR) =1.96 (1.06-3.75), P=0.032] and progression-free survival (PFS) [HR =1.72 (1.05-2.93), P=0.032] in NSCLC patients. In our multivariate analysis, advanced cancer stage and high MCT4 level were identified as independent predictive indicators for both PFS [HR(MCT4) =1.888 (1.114-3.199), P=0.018 and OS [HR (MCT4) =2.421 (1.271-4.610), P=0.007]. Subgroup and interaction analyses were also performed in different clinical characteristic groups and no significant differences were observed. CONCLUSIONS: High MCT4 expression is a predictive marker for worse outcome in NSCLC patients.

Monocarboxylate transporter 1 and 4 inhibitors as potential therapeutics for treating solid tumours: A review with structure-activity relationship insights.

Development of multidrug resistance (MDR) is one of the major causes leading to failure of cancer chemotherapy and radiotherapy. Monocarboxylate transporters (MCTs) MCT1 and MCT4, which are overexpressed in solid tumours, play a very important role in cancer cell survival and proliferation. These lactate transporters work complimentarily to drive lactate shuttle in tumour cells, which results in maintenance of H+ ion (pH) balance necessary for their survival. Inhibition of these transmembrane proteins has been demonstrated as a novel strategy to treat drug resistant solid cancers. Presently, only a few small molecule MCT1 inhibitors such as AZD3965 and AR-C155858 are known with clinical potential. Even lesser mention of MCT4 inhibitors, which include molecules having scaffolds such as pyrazole and indazole, is available in the literature. Current overview presents the status of recent developments undertaken in identification of efficacious MCT1 and/or MCT4 inhibitors as a potential anticancer therapy overcoming MDR. Further, detailed structure-activity relationships for different classes of compounds has been proposed to streamline the understandings learnt from ongoing research work. Through this review, we aim to highlight the importance of these excellent targets and facilitate future development of selective, potent and safe MCT1 and/or MCT4 inhibitors as promising chemotherapy for drug resistant cancer.

Nitric oxide might be an inducing factor in cognitive impairment in Alzheimer's disease via downregulating the monocarboxylate transporter 1.

Alzheimer's disease (AD) is a typical neurodegenerative disease in central nervous system (CNS). Generally speaking, patients with severe AD are often accompanied with cognitive impairment. Oligodendrocytes (OLs) are myelin-forming cells in CNS, and myelin injury potentially has something to do with the cognitive impairment in AD. Based on the previous experimental studies, it has been recognized that nitric oxide (NO), as a signaling molecule, might have an influence on the axon and myelin by affecting the energy transport mechanism of OLs through monocarboxylate transporter 1 (MCT1). Interestingly, a novel model of cell signaling----axo-myelinic synapse (AMS) has been put forward. In the context of this model, chances are that a new way is established in which NO can influence the pathogenesis of AD by down-regulating the expression of MCT1. As a consequence, it may provide attractive prospective and underlying drug targeting effects for the treatment of AD.

Radiosynthesis and validation of (±)-[18F]-3-fluoro-2-hydroxypropionate ([18F]-FLac) as a PET tracer of lactate to monitor MCT1-dependent lactate uptake in tumors.

Cancers develop metabolic strategies to cope with their microenvironment often characterized by hypoxia, limited nutrient bioavailability and exposure to anticancer treatments. Among these strategies, the metabolic symbiosis based on the exchange of lactate between hypoxic/glycolytic cancer cells that convert glucose to lactate and oxidative cancer cells that preferentially use lactate as an oxidative fuel optimizes the bioavailability of glucose to hypoxic cancer cells. This metabolic cooperation has been described in various human cancers and can provide resistance to anti-angiogenic therapies. It depends on the expression and activity of monocarboxylate transporters (MCTs) at the cell membrane. MCT4 is the main facilitator of lactate export by glycolytic cancer cells, and MCT1 is adapted for lactate uptake by oxidative cancer cells. While MCT1 inhibitor AZD3965 is currently tested in phase I clinical trials and other inhibitors of lactate metabolism have been developed for anticancer therapy, predicting and monitoring a response to the inhibition of lactate uptake is still an unmet clinical need. Here, we report the synthesis, evaluation and in vivo validation of (±)-[18F]-3-fluoro-2-hydroxypropionate ([18F]-FLac) as a tracer of lactate for positron emission tomography. [18F]-FLac offers the possibility to monitor MCT1-dependent lactate uptake and inhibition in tumors in vivo.

Monocarboxylate Transporter 1 in the Medial Prefrontal Cortex Developmentally Expresses in Oligodendrocytes and Associates with Neuronal Amounts.

Lactate is an energy substrate in adult brain especially when glucose is withdrawn or only lactate is present as main energy source. Besides, the most abundant lactate transporter in brain-monocarboxylate transporter 1 (MCT1)-was recognized recently. Despite this, MCT1 expressions in central nervous system (CNS) have not been clearly understood. Medial prefrontal cortex (mPFC), taking part in many higher executive functions in brain, is chosen here for observing MCT1 expressions in mice in 12 months. As results showed, MCT1 is gradually increased from an initial level at the 1st week to a high level at the 6th week and then gradually decreased to a low level at the 12th month. Besides, neuronal amounts change in a similar trend as MCT1 that neurons at the 6th week are more than that of at the 1st week and the 12th month. Also, MCT1 expressions are highly correlated with neuronal amounts, while MCT1 does not localize within neurons, instead localize around axons. On the other hand, MCT1 does localize to oligodendrocytes (OLs) without localizing to other glial cells (astrocytes and microglias). Importantly, the amounts of OLs change in a similar trend as MCT1, while the amounts of other glial cells do not change obviously in the mPFC in vivo in 12 months. These results demonstrate that the changeable expressions of MCT1 in the mPFC in vivo in 12 months may be mainly contributed by OLs and associate with the neuronal amounts. Above all, it infers that in vivo, MCT1 which is changeably expressed in OLs may further affect neuronal amounts in the mPFC in 12 months.

Lactate/pyruvate transporter MCT-1 is a direct Wnt target that confers sensitivity to 3-bromopyruvate in colon cancer.

BACKGROUND: There 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. RESULTS: Here, 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. CONCLUSIONS: We 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.

Lactate promotes glutamine uptake and metabolism in oxidative cancer cells.

Oxygenated cancer cells have a high metabolic plasticity as they can use glucose, glutamine and lactate as main substrates to support their bioenergetic and biosynthetic activities. Metabolic optimization requires integration. While glycolysis and glutaminolysis can cooperate to support cellular proliferation, oxidative lactate metabolism opposes glycolysis in oxidative cancer cells engaged in a symbiotic relation with their hypoxic/glycolytic neighbors. However, little is known concerning the relationship between oxidative lactate metabolism and glutamine metabolism. Using SiHa and HeLa human cancer cells, this study reports that intracellular lactate signaling promotes glutamine uptake and metabolism in oxidative cancer cells. It depends on the uptake of extracellular lactate by monocarboxylate transporter 1 (MCT1). Lactate first stabilizes hypoxia-inducible factor-2α (HIF-2α), and HIF-2α then transactivates c-Myc in a pathway that mimics a response to hypoxia. Consequently, lactate-induced c-Myc activation triggers the expression of glutamine transporter ASCT2 and of glutaminase 1 (GLS1), resulting in improved glutamine uptake and catabolism. Elucidation of this metabolic dependence could be of therapeutic interest. First, inhibitors of lactate uptake targeting MCT1 are currently entering clinical trials. They have the potential to indirectly repress glutaminolysis. Second, in oxidative cancer cells, resistance to glutaminolysis inhibition could arise from compensation by oxidative lactate metabolism and increased lactate signaling.

Diversity in the utilization of glucose and lactate in synthetic mammalian myotubes generated by engineered configurations of MyoD and E12 in otherwise non-differentiation growth conditions.

We previously used the expression of various combinations and configurations of MyoD and E12, two basic helix-loop-helix transcription factors (TF), to produce populations of myotubes assuming distinct morphology, myofibrillar development and Ca2+ dynamics, from mammalian C2C12 myoblasts in non-differentiation growth conditions. Here, we assessed the synthetically generated myotubes in terms of energetics, otherwise necessary to sustain their mechanical output as bio-actuators. We found that the myotubes exhibit changed expression of key regulators for the uptake and utilization of two major cellular fuels, glucose and lactate. Furthermore, while lactate transport was uniformly slowed in all the populations of myotubes, glucose uptake and utilization were modified by particular TF configuration. Our approach allows the production of a class of biomaterials with predetermined energetics that could be applied in biorobotics, where fuel of choice could be used, and also in reparative medicine where, for example, particular population of myotubes could be additionally employed as glucose sinks to mitigate effects of secondary metabolic syndrome.