Tracing Nutrient Flux Following Monocarboxylate Transporter-1 Inhibition with AZD3965.

Nicoleta Baxan,Maciej Kaliszczak,Kathrin Heinzmann,John Latigo,Chris Barnes,Stephen Stribbling,Hector Keun,Alice Beckley,Francesco Mauri,Zachary T Schug,Gabriel N Valbuena,Laurence Carroll,Adrian Benito,Marta Braga,Gillian Mackay,Eric O Aboagye,Eyal Gottlieb

doi:10.3390/cancers12061703

Abstract

The monocarboxylate transporter 1 (MCT1) is a key element in tumor cell metabolism and inhibition of MCT1 with AZD3965 is undergoing clinical trials. We aimed to investigate nutrient fluxes associated with MCT1 inhibition by AZD3965 to identify possible biomarkers of drug action. We synthesized an 18F-labeled lactate analogue, [18F]-S-fluorolactate ([18F]-S-FL), that was used alongside [18F]fluorodeoxyglucose ([18F]FDG), and 13C-labeled glucose and lactate, to investigate the modulation of metabolism with AZD3965 in diffuse large B-cell lymphoma models in NOD/SCID mice. Comparative analysis of glucose and lactate-based probes showed a preference for glycolytic metabolism in vitro, whereas in vivo, both glucose and lactate were used as metabolic fuel. While intratumoral L-[1-13C]lactate and [18F]-S-FL were unchanged or lower at early (5 or 30 min) timepoints, these variables were higher compared to vehicle controls at 4 h following treatment with AZD3965, which indicates that inhibition of MCT1-mediated lactate import is reversed over time. Nonetheless, AZD3965 treatment impaired DLBCL tumor growth in mice. This was hypothesized to be a consequence of metabolic strain, as AZD3965 treatment showed a reduction in glycolytic intermediates and inhibition of the TCA cycle likely due to downregulated PDH activity. Glucose ([18F]FDG and D-[13C6]glucose) and lactate-based probes ([18F]-S-FL and L-[1-13C]lactate) can be successfully used as biomarkers for AZD3965 treatment.

Highlights

The monocarboxylate transporter 1 (MCT1) is a proton and monocarboxylate symporter that in humans is encoded by the SLC16A1 gene
The expression of MCT1 was confirmed in diffuse large B-cell lymphoma (DLBCL) patient tissue microarray (TMA) samples (Figure 1C, Figure S1)
We developed an 18 F-labeled lactate analogue and used it alongside L-[1-13 C]lactate, D-[13 C6 ]glucose and [18 F]FDG to investigate the altered nutrient flux of tumors in the presence of the MCT1 inhibitor AZD3965: we present evidence that lactate is consumed by the DLBCL tumor model used, and, perhaps consequentially, AZD3965-mediated inhibition of lactate influx is reversed within 4 h of treatment

Summary

Introduction

The monocarboxylate transporter 1 (MCT1) is a proton and monocarboxylate symporter that in humans is encoded by the SLC16A1 gene. MCT1, together with MCT4 (encoded by SLC16A3 gene), has been extensively studied for their roles in the cell membrane’s transport of monocarboxylates. AZD3965 is the most advanced [5,6,7] When tumors express both MCT1 and MCT4, as is the case in small cell lung cancer, MCT4 expression appears to be a negative prognostic factor for sensitivity to MCT1 inhibition [5]. This finding suggested that MCT1 inhibitor therapy will be most effective in cell lineages or tumor subpopulations expressing MCT1 but not MCT4. AZD3965 is currently undergoing a Cancer Research UK Centre for Drug Development sponsored Phase I trial in patients with advanced cancers (ClinicalTrials.gov identifier: NCT01791595)

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