Monocarboxylate transporter 1 blockade with AZD3965 inhibits lipid biosynthesis and increases tumour immune cell infiltration.

Background: Monocarboxylate transporter 1 (MCT1) is a regulator of cell metabolism and a therapeutic target for cancer treatment. Understanding the changes in tumour function accompanying MCT1 inhibition will better characterise the anti-tumour effects of MCT1 inhibitors, potentially enabling the identification of pharmacodynamic biomarkers for the clinical development of these agents.

Methods: We assessed the impact of the MCT1 inhibitor AZD3965 on tumour metabolism and immune cell infiltration as key determinants of tumour biological function in the MCT1-dependent Raji B cell lymphoma model.

Results: Treatment of Raji xenograft-bearing severe combined immunodeficiency mice with AZD3965 led to inhibition of tumour growth paralleled with a decrease in tumour choline, as detected by non-invasive in vivo proton nuclear magnetic resonance spectroscopy. This effect was attributed to inhibition of phosphocholine de novo synthesis following decreased choline kinase α protein and messenger RNA expression that correlated with the AZD3965-induced build-up in intracellular lactate. These changes were concomitant with increased tumour immune cell infiltration involving dendritic and natural killer cells.

Conclusions: Our data provide new insights into the metabolic and cellular changes that occur in the tumour microenvironment following MCT1 blockade, which may contribute to the anti-tumour activity of AZD3965 and could have potential as pharmacodynamic biomarkers of MCT1 inhibition.