Discovery of 5-{2-[5-Chloro-2-(5-ethoxyquinoline-8-sulfonamido)phenyl]ethynyl}-4-methoxypyridine-2-carboxylic Acid, a Highly Selective in Vivo Useable Chemical Probe to Dissect MCT4 Biology

Biophysical and structural characterization of the impacts of MET phosphorylation on tepotinib binding

The receptor tyrosine kinase MET is activated by hepatocyte growth factor binding, followed by phosphorylation of the intracellular kinase domain (KD) mainly within the activation loop (A-loop) on Y1234 and Y1235. Dysregulation of MET can lead to both tumor growth and metastatic progression of cancer cells. Tepotinib is a highly selective, potent type Ib MET inhibitor and approved for treatment of non-small cell lung cancer harboring METex14 skipping alterations. Tepotinib binds to the ATP site of unphosphorylated MET with critical π-stacking contacts to Y1230 of the A-loop, resulting in a high residence time. In our study, we combined protein crystallography, biophysical methods (surface plasmon resonance, differential scanning fluorimetry), and mass spectrometry to clarify the impacts of A-loop conformation on tepotinib binding using different recombinant MET KD protein variants. We solved the first crystal structures of MET mutants Y1235D, Y1234E/1235E, and F1200I in complex with tepotinib. Our biophysical and structural data indicated a linkage between reduced residence times for tepotinib and modulation of A-loop conformation either by mutation (Y1235D), by affecting the overall Y1234/Y1235 phosphorylation status (L1195V and F1200I) or by disturbing critical π-stacking interactions with tepotinib (Y1230C). We corroborated these data with target engagement studies by fluorescence cross-correlation spectroscopy using KD constructs in cell lysates or full-length receptors from solubilized cellular membranes as WT or activated mutants (Y1235D and Y1234E/1235E). Collectively, our results provide further insight into the MET A-loop structural determinants that affect the binding of the selective inhibitor tepotinib.

Monocarboxylate transporter 4 promotes the migration of non‑cancerous L929 fibroblast cells by activating the IGF1/IGF1R/PIK3R3/SGK1 axis

The tumor microenvironment (TME) and Warburg effect are critical for the regulation of tumor metastasis. The monocarboxylate transporter (MCT) family members, particularly MCT4, which is encoded by the solute carrier family 16 member 3 gene, play an important role in the regulation of the TME and mediation of the Warburg effect by transporting lactate out of cancer cells. Migration and invasion are two key features of metastasis. Few studies have investigated the mechanism by which MCT4 promotes cell migration, and the suggested mechanisms by which MCT4 promotes migration vary in different tumor cell models. The purpose of the present study was to use non-cancerous cells as a research model to investigate the specific mechanism underlying the promotion of migration by MCT4. In a previous study, murine L929 cells overexpressing human MCT4 (MCT4-L929 cells) were generated and MCT4 was demonstrated to promote the migration and invasion of these non-cancerous cells. In the present study, MCT4-L929 cells and control-L929 cells were used to investigate the potential pathways and mechanisms through which MCT4 promotes cell migration. RNA sequencing analysis revealed 872 differentially expressed genes, comprising 337 and 535 upregulated and downregulated genes, respectively, in the MCT4-L929 cells. Reverse transcription-quantitative analysis and western blotting revealed that MCT4 overexpression increased the transcription and protein levels of insulin-like growth factor 1 (IGF1). In a wound healing assay, the migration of exogenous mouse IGF1-treated control-L929 cells was similar to that of MCT4-L929 cells. Additionally, the inhibition of IGF1 receptor (IGF1R) or serum/glucocorticoid regulated kinase 1 (SGK1), a downstream protein in the IGF1 and phosphoinositide 3-kinase PI3K regulatory subunit 3 (PIK3R3) pathways, in MCT4-L929 cells mitigated the cell migration-promoting effect of MCT4. These novel findings suggest that MCT4 may promote the migration of L929 fibroblast cells via activation of the IGF1/IGF1R/PIK3R3/SGK1 axis.

MCT4 blockade increases the efficacy of immune checkpoint blockade

BACKGROUND & AIMS

Intratumoral lactate accumulation and acidosis impair T-cell function and antitumor immunity. Interestingly, expression of the lactate transporter monocarboxylate transporter (MCT) 4, but not MCT1, turned out to be prognostic for the survival of patients with rectal cancer, indicating that single MCT4 blockade might be a promising strategy to overcome glycolysis-related therapy resistance.

METHODS

To determine whether blockade of MCT4 alone is sufficient to improve the efficacy of immune checkpoint blockade (ICB) therapy, we examined the effects of the selective MCT1 inhibitor AZD3965 and a novel MCT4 inhibitor in a colorectal carcinoma (CRC) tumor spheroid model co-cultured with blood leukocytes in vitro and the MC38 murine CRC model in vivo in combination with an antibody against programmed cell death ligand-1(PD-L1).

RESULTS

Inhibition of MCT4 was sufficient to reduce lactate efflux in three-dimensional (3D) CRC spheroids but not in two-dimensional cell-cultures. Co-administration of the MCT4 inhibitor and ICB augmented immune cell infiltration, T-cell function and decreased CRC spheroid viability in a 3D co-culture model of human CRC spheroids with blood leukocytes. Accordingly, combination of MCT4 and ICB increased intratumoral pH, improved leukocyte infiltration and T-cell activation, delayed tumor growth, and prolonged survival in vivo. MCT1 inhibition exerted no further beneficial impact.

CONCLUSIONS

These findings demonstrate that single MCT4 inhibition represents a novel therapeutic approach to reverse lactic-acid driven immunosuppression and might be suitable to improve ICB efficacy.

Paralog-dependent isogenic cell assay cascade generates highly selective SLC16A3 inhibitors

Despite being considered druggable and attractive therapeutic targets, most of the solute carrier (SLC) membrane transporters remain pharmacologically underexploited. One of the reasons for this is a lack of reliable chemical screening assays, made difficult by functional redundancies among SLCs. In this study we leveraged synthetic lethality between the lactate transporters SLC16A1 and SLC16A3 in a screening strategy that we call paralog-dependent isogenic cell assay (PARADISO). The system involves five isogenic cell lines, each dependent on various paralog genes for survival/fitness, arranged in a screening cascade tuned for the identification of SLC16A3 inhibitors. We screened a diversity-oriented library of ∼90,000 compounds and further developed our hits into slCeMM1, a paralog-selective and potent SLC16A3 inhibitor. By implementing chemoproteomics, we showed that slCeMM1 is selective also at the proteome-wide level, thus fulfilling an important criterion for chemical probes. This study represents a framework for the development of specific cell-based drug discovery assays.

Targeting monocarboxylate transporters (MCTs) in cancer: How close are we to the clinics?

As a result of metabolic reprogramming, cancer cells display high rates of glycolysis, causing an excess production of lactate along with an increase in extracellular acidity. Proton-linked monocarboxylate transporters (MCTs) are crucial in the maintenance of this metabolic phenotype, by mediating the proton-coupled lactate flux across cell membranes, also contributing to cancer cell pH regulation. Among the proteins codified by the SLC16 gene family, MCT1 and MCT4 isoforms are the most explored in cancers, being overexpressed in many cancer types, from solid tumours to haematological malignancies. Similarly to what occurs in particular physiological settings, MCT1 and MCT4 are able to mediate lactate shuttles among cancer cells, and also between cancer and stromal cells in the tumour microenvironment. This form of metabolic cooperation is responsible for important cancer aggressiveness features, such as cell proliferation, survival, angiogenesis, migration, invasion, metastasis, immune tolerance and therapy resistance. The growing understanding of MCT functions and regulation is offering a new path to the design of novel inhibitors that can be foreseen in clinical practices. This review provides an overview of the role of MCT isoforms in cancer and summarizes the recent advances in their pharmacological targeting, highlighting the potential of new potent and selective MCT1 and/or MCT4 inhibitors in cancer therapeutics, and anticipating its inclusion in clinical practice.

Functional heterogeneity of MCT1 and MCT4 in metabolic reprogramming affects osteosarcoma growth and metastasis

BACKGROUND

Osteosarcoma is the most common primary malignant bone tumor in adolescents and children and prone to develop lung metastasis. Its prognosis has been virtually unimproved over the last few decades, especially in patients with metastases, who suffer from a dismal survival. Recently, increasing attention has been devoted to monocarboxylate transporters-related (MCTs) metabolic reprogramming. However, the role of MCT1 and MCT4 in osteosarcoma progression and the underlying mechanisms remain to be further elucidated.

METHODS

In this study, we established MCT1 and/or MCT4 knockout cell lines by CRISPR/Cas9 genome editing technology. Then, we assessed glycolysis and oxidative phosphorylation capacities by measuring lactate flux and oxygen consumption. We also performed flowcytometry to test circulating tumor cells and PET/CT to evaluate glucose uptake.

RESULTS

MCT1 was found to be involved in both glycolysis and oxidative respiration due to its ability to transport lactate in both directions. MCT1 inhibition significantly reduced circulating tumor cells and distant metastases partially by increasing oxidative stress. MCT4 was primarily related to glycolysis and responsible for lactate export when the concentration of extracellular lactate was high. MCT4 inhibition dramatically suppressed cell proliferation in vitro and impaired tumor growth with reduction of glucose uptake in vivo.

CONCLUSIONS

Our results demonstrate the functional heterogeneity and redundancy of MCT1 and MCT4 in glucose metabolism and tumor progression in osteosarcoma. Thus, combined inhibition of MCT1 and MCT4 may be a promising therapeutic strategy for treating tumors expressing both transporters.

Chemical Biology Approaches Confirm MCT4 as the Therapeutic Target of a Cellular Optimized Hit

Lactic acid transport is a key process maintaining glycolytic flux in tumors. Inhibition of this process will result in glycolytic shutdown, impacting on cell growth and survival and thus has been pursued as a therapeutic approach for cancers. Using a cell-based screen in a MCT4-dependent cell line, we identified and optimized compounds for their ability to inhibit the efflux of intracellular lactic acid with good physical and pharmacokinetic properties. To deconvolute the mechanism of lactic acid efflux inhibition, we have developed three assays to measure cellular target engagement. Specifically, we synthesized a biologically active photoaffinity probe (IC₅₀ < 10 nM), and using this probe, we demonstrated selective engagement of MCT4 of our parent molecule through a combination of confocal microscopy and in-cell chemoproteomics. As an orthogonal assay, the cellular thermal shift assay (CETSA) confirmed binding to MCT4 in the cellular system. Comparisons of lactic acid efflux potencies in cells with differential expression of MCT family members further confirmed that the optimized compounds inhibit the efflux of lactic acid through the inhibition of MCT4. Taken together, these data demonstrate the power of orthogonal chemical biology methods to determine cellular target engagement, particularly for proteins not readily amenable to traditional biophysical methods.

Discovery of Clinical Candidate AZD0095, a Selective Inhibitor of Monocarboxylate Transporter 4 (MCT4) for Oncology

Due to increased reliance on glycolysis, which produces lactate, monocarboxylate transporters (MCTs) are often upregulated in cancer. MCT4 is associated with the export of lactic acid from cancer cells under hypoxia, so inhibition of MCT4 may lead to cytotoxic levels of intracellular lactate. In addition, tumor-derived lactate is known to be immunosuppressive, so MCT4 inhibition may be of interest for immuno-oncology. At the outset, no potent and selective MCT4 inhibitors had been reported, but a screen identified a triazolopyrimidine hit, with no close structural analogues. Minor modifications to the triazolopyrimidine were made, alongside design of a constrained linker and broad SAR exploration of the biaryl tail to improve potency, physical properties, PK, and hERG. The resulting clinical candidate 15 (AZD0095) has excellent potency (1.3 nM), MCT1 selectivity (>1000×), secondary pharmacology, clean mechanism of action, suitable properties for oral administration in the clinic, and good preclinical efficacy in combination with cediranib.

Target 2035 – an update on private sector contributions

Target 2035, an international federation of biomedical scientists from the public and private sectors, is leveraging ‘open’ principles to develop a pharmacological tool for every human protein.

'Warburg effect' controls tumor growth, bacterial, viral infections and immunity - Genetic deconstruction and therapeutic perspectives

The evolutionary pressure for life transitioning from extended periods of hypoxia to an increasingly oxygenated atmosphere initiated drastic selections for a variety of biochemical pathways supporting the robust life currently present on the planet. First, we discuss how fermentative glycolysis, a primitive metabolic pathway present at the emergence of life, is instrumental for the rapid growth of cancer, regenerating tissues, immune cells but also bacteria and viruses during infections. The 'Warburg effect', activated via Myc and HIF-1 in response to growth factors and hypoxia, is an essential metabolic and energetic pathway which satisfies nutritional and energetic demands required for rapid genome replication. Second, we present the key role of lactic acid, the end-product of fermentative glycolysis able to move across cell membranes in both directions via monocarboxylate transporting proteins (i.e. MCT1/4) contributing to cell-pH homeostasis but also to the complex immune response via acidosis of the tumour microenvironment. Importantly lactate is recycled in multiple organs as a major metabolic precursor of gluconeogenesis and energy source protecting cells and animals from harsh nutritional or oxygen restrictions. Third, we revisit the Warburg effect via CRISPR-Cas9 disruption of glucose-6-phosphate isomerase (GPI-KO) or lactate dehydrogenases (LDHA/B-DKO) in two aggressive tumours (melanoma B16-F10, human adenocarcinoma LS174T). Full suppression of lactic acid production reduces but does not suppress tumour growth due to reactivation of OXPHOS. In contrast, disruption of the lactic acid transporters MCT1/4 suppressed glycolysis, mTORC1, and tumour growth as a result of intracellular acidosis. Finally, we briefly discuss the current clinical developments of an MCT1 specific drug AZ3965, and the recent progress for a specific in vivo MCT4 inhibitor, two drugs of very high potential for future cancer clinical applications.

Nickel(0)-catalysed linear-selective hydroarylation of 2-aminostyrenes with arylboronic acids by a bifunctional temporary directing group strategy

We report a nickel(0)-catalyzed linear-selective hydroarylation of 2-aminostyrenes with arylboronic acids using a bifunctional temporary directing group strategy. In the presence of a catalytic amount of commercially available 3,5-dibromosalicylaldehyde, an...

LINC00035 Transcriptional Regulation of SLC16A3 via CEBPB Affects Glycolysis and Cell Apoptosis in Ovarian Cancer

Objective

Ovarian cancer (OC) represents the most lethal gynecologic malignancy globally. Over the decades, lncRNAs have been considered as study focuses due to their genome-wide expression through multiple mechanisms in which regulation of target gene transcription through interaction with transcription factors or epigenetic proteins is proven. In the present work, we focus on the functional role of LINC00035 in OC and its regulation mechanism on gene expression.

Methods

We collected OC tissues and adjacent tumor-free tissues surgically resected from 67 OC patients. Cultured human OC cell lines SKOV3 and A2780 were assayed for their viability, migration, invasion, apoptosis in vitro using CCK-8 assays, transwell assays, and flow cytometric analysis. OC cell tumorigenesis in vivo was evaluated by mouse xenograft experiments. Glycolysis was evaluated by glucose uptake, lactate release, and ATP production assays. Luciferase activity assay, RNA immunoprecipitation (RIP), and RNA pull-down were performed to confirm the interactions among LINC00035, CEBPB, and SLC16A3.

Results

LINC00035 was upregulated in OC tissues. LINC00035 knockdown was shown to repress SKOV3 and A2780 cell viability, migration, invasion, induce their apoptosis, and reduce glucose uptake, lactate release, and ATP production. LINC00035 could recruit CEBPB into the SLC16A3 promoter region, thus increasing the SLC16A3 transcription. SLC16A3 was upregulated in OC tissues. SLC16A3 knockdown exerted similar effects on SKOV3 and A2780 cells as LINC00035 knockdown. Rescue experiments found SLC16A3 overexpression resisting to LINC00035 knockdown on SKOV3 and A2780 cell viability, migration, invasion, apoptosis, glucose uptake, lactate release, and ATP production. Results also showed LINC00035 knockdown could inhibit OC cell tumorigenesis in vivo.

Conclusion

The study reveals that LINC00035 promotes OC progression by regulating glycolysis and cell apoptosis through CEBPB-mediated transcriptional promotion of SLC16A3.