Carbonic anhydrase 2 (CAII) supports tumor blood endothelial cell survival under lactic acidosis in the tumor microenvironment

Dorcas A Annan,Hiroshi Kikuchi,Tetsuya Kitamura,Kazuyuki Minowa,Tomoyoshi Soga,Masahiro Morimoto,Mohammad Towfik Alam,Kyoko Hida,Nobuo Shinohara,Yasuhiro Hida,Cong Li,Nako Maishi,Randa Dawood,Takayuki Hojo,Jin-Min Nam

doi:10.1186/s12964-019-0478-4

Dorcas A Annan, Hiroshi Kikuchi + Show 13 more

Open Access

https://doi.org/10.1186/s12964-019-0478-4

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Abstract

BackgroundTumor endothelial cells (TECs) perform tumor angiogenesis, which is essential for tumor growth and metastasis. Tumor cells produce large amounts of lactic acid from glycolysis; however, the mechanism underlying the survival of TECs to enable tumor angiogenesis under high lactic acid conditions in tumors remains poorly understood.MethodologyThe metabolomes of TECs and normal endothelial cells (NECs) were analyzed by capillary electrophoresis time-of-flight mass spectrometry. The expressions of pH regulators in TECs and NECs were determined by quantitative reverse transcription-PCR. Cell proliferation was measured by the MTS assay. Western blotting and ELISA were used to validate monocarboxylate transporter 1 and carbonic anhydrase 2 (CAII) protein expression within the cells, respectively. Human tumor xenograft models were used to access the effect of CA inhibition on tumor angiogenesis. Immunohistochemical staining was used to observe CAII expression, quantify tumor microvasculature, microvessel pericyte coverage, and hypoxia.ResultsThe present study shows that, unlike NECs, TECs proliferate in lactic acidic. TECs showed an upregulated CAII expression both in vitro and in vivo. CAII knockdown decreased TEC survival under lactic acidosis and nutrient-replete conditions. Vascular endothelial growth factor A and vascular endothelial growth factor receptor signaling induced CAII expression in NECs. CAII inhibition with acetazolamide minimally reduced tumor angiogenesis in vivo. However, matured blood vessel number increased after acetazolamide treatment, similar to bevacizumab treatment. Additionally, acetazolamide-treated mice showed decreased lung metastasis.ConclusionThese findings suggest that due to their effect on blood vessel maturity, pH regulators like CAII are promising targets of antiangiogenic therapy.1ZdJgANzaMPCEpiU7ctGHJVideo Graphical abstract

Highlights

Tumor endothelial cells (TECs) perform tumor angiogenesis, which is essential for tumor growth and metastasis
TECs are more sensitive to carbonic anhydrase II inhibition Considering that MCT1 inhibition can decrease tumor angiogenesis in vivo [20] and the upregulated CAII expression in TECs, we addressed the functional roles of MCT1 and CAII in TECs
Since our previous reports showed that A375-SM-conditioned medium (CM) contains significant amounts of vascular endothelial growth factor (VEGF) [6], we investigated the contribution of VEGF to CAII expression

Summary

Introduction

Tumor endothelial cells (TECs) perform tumor angiogenesis, which is essential for tumor growth and metastasis. Tumor cells produce large amounts of lactic acid from glycolysis; the mechanism underlying the survival of TECs to enable tumor angiogenesis under high lactic acid conditions in tumors remains poorly understood. Annan et al Cell Communication and Signaling (2019) 17:169 effects of acidity [12] and lactate [13] on NECs, have been independently reported, their cumulative effect (i.e., a state of lactic acidosis) on TECs, remains unknown. We hypothesized that TECs possess unique properties that promote their survival in a lactic acid-rich environment. To address this hypothesis, we identified the response of TECs and NECs to lactic acidosis., as well as the possible mechanism involved in their survival under lactic acidosis

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