Dataset Information

Carbonic anhydrase IX is a pH-stat that sets an acidic tumour extracellular pH in vivo.

ABSTRACT:

Background

Tumour carbonic anhydrase IX (CAIX), a hypoxia-inducible tumour-associated cell surface enzyme, is thought to acidify the tumour microenvironment by hydrating CO₂ to form protons and bicarbonate, but there is no definitive evidence for this in solid tumours in vivo.

Methods

We used ¹H magnetic resonance spectroscopic imaging (MRSI) of the extracellular pH probe imidazolyl succinic acid (ISUCA) to measure and spatially map extracellular pH in HCT116 tumours transfected to express CAIX and empty vector controls in SCID mice. We also measured intracellular pH in situ with ³¹P MRS and measured lactate in freeze-clamped tumours.

Results

CAIX-expressing tumours had 0.15 pH-unit lower median extracellular pH than control tumours (pH 6.71 tumour vs pH 6.86 control, P?=?0.01). Importantly, CAIX expression imposed an upper limit for tumour extracellular pH at 6.93. Despite the increased lactate concentration in CAIX-expressing tumours, ³¹P MRS showed no difference in intracellular pH, suggesting that CAIX acidifies only the tumour extracellular space.

Conclusions

CAIX acidifies the tumour microenvironment, and also provides an extracellular pH control mechanism. We propose that CAIX thus acts as an extracellular pH-stat, maintaining an acidic tumour extracellular pH that is tolerated by cancer cells and favours invasion and metastasis.

SUBMITTER: Lee SH

PROVIDER: S-EPMC6162214 | biostudies-literature | 2018 Aug

REPOSITORIES: biostudies-literature

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Publications

Carbonic anhydrase IX is a pH-stat that sets an acidic tumour extracellular pH in vivo.

Lee Shen-Han SH McIntyre Dominick D Honess Davina D Hulikova Alzbeta A Pacheco-Torres Jesús J Cerdán Sebastián S Swietach Pawel P Harris Adrian L AL Griffiths John R JR

British journal of cancer 20180801 5

<h4>Background</h4>Tumour carbonic anhydrase IX (CAIX), a hypoxia-inducible tumour-associated cell surface enzyme, is thought to acidify the tumour microenvironment by hydrating CO<sub>2</sub> to form protons and bicarbonate, but there is no definitive evidence for this in solid tumours in vivo.<h4>Methods</h4>We used <sup>1</sup>H magnetic resonance spectroscopic imaging (MRSI) of the extracellular pH probe imidazolyl succinic acid (ISUCA) to measure and spatially map extracellular pH in HCT116 ...[more]

PMID: 30206370

Similar Datasets

Project description:Carbonic anhydrase IX (CA IX) is a transmembrane enzyme that is present in many types of solid tumors. Expression of CA IX is driven predominantly by the hypoxia-inducible factor (HIF) pathway and helps to maintain intracellular pH homeostasis under hypoxic conditions, resulting in acidification of the tumor microenvironment. Carnosine (?-alanyl-L-histidine) is an anti-tumorigenic agent that inhibits the proliferation of cancer cells. In this study, we investigated the role of CA IX in carnosine-mediated antitumor activity and whether the underlying mechanism involves transcriptional and translational modulation of HIF-1? and CA IX and/or altered CA IX function.The effect of carnosine was studied using two-dimensional cell monolayers of several cell lines with endogenous CA IX expression as well as Madin Darby canine kidney transfectants, three-dimensional HeLa spheroids, and an in vivo model of HeLa xenografts in nude mice. mRNA and protein expression and protein localization were analyzed by real-time PCR, western blot analysis, and immunofluorescence staining, respectively. Cell viability was measured by a flow cytometric assay. Expression of HIF-1? and CA IX in tumors was assessed by immunohistochemical staining. Real-time measurement of pH was performed using a sensor dish reader. Binding of CA IX to specific antibodies and metabolon partners was investigated by competitive ELISA and proximity ligation assays, respectively.Carnosine increased the expression levels of HIF-1? and HIF targets and increased the extracellular pH, suggesting an inhibitory effect on CA IX-mediated acidosis. Moreover, carnosine significantly inhibited the growth of three-dimensional spheroids and tumor xenografts compared with untreated controls. Competitive ELISA showed that carnosine disrupted binding between CA IX and antibodies specific for its catalytic domain. This finding was supported by reduced formation of the functional metabolon of CA IX and anion exchanger 2 in the presence of carnosine.Our results indicate that interaction of carnosine with CA IX leads to conformational changes of CA IX and impaired formation of its metabolon, which in turn disrupts CA IX function. These findings suggest that carnosine could be a promising anticancer drug through its ability to attenuate the activity of CA IX.

Dataset Information

Carbonic anhydrase IX is a pH-stat that sets an acidic tumour extracellular pH in vivo.

Background

Methods

Results

Conclusions

Publications

Carbonic anhydrase IX is a pH-stat that sets an acidic tumour extracellular pH in vivo.

Similar Datasets

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