Benzotriazine Di-Oxide Prodrugs for Exploiting Hypoxia and Low Extracellular pH in Tumors

Extracellular acidification is an important feature of tumor microenvironments but has yet to be successfully exploited in cancer therapy. The reversal of the pH gradient across the plasma membrane in cells that regulate intracellular pH (pHi) has potential to drive the selective uptake of weak acid...

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Main Authors: Michael P. Hay, Hong Nam Shin, Way Wua Wong, Wan Wan Sahimi, Aaron T.D. Vaz, Pooja Yadav, Robert F. Anderson, Kevin O. Hicks, William R. Wilson
Format: Article
Language:English
Published: MDPI AG 2019-07-01
Series:Molecules
Subjects:
Online Access:https://www.mdpi.com/1420-3049/24/14/2524
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spelling doaj-f817294cf9cf4d298cd9a829268a2ea32020-11-25T00:37:05ZengMDPI AGMolecules1420-30492019-07-012414252410.3390/molecules24142524molecules24142524Benzotriazine Di-Oxide Prodrugs for Exploiting Hypoxia and Low Extracellular pH in TumorsMichael P. Hay0Hong Nam Shin1Way Wua Wong2Wan Wan Sahimi3Aaron T.D. Vaz4Pooja Yadav5Robert F. Anderson6Kevin O. Hicks7William R. Wilson8Auckland Cancer Society Research Centre, School of Medical Sciences, Faculty of Medical and Health Sciences, University of Auckland, Auckland 1142, New ZealandAuckland Cancer Society Research Centre, School of Medical Sciences, Faculty of Medical and Health Sciences, University of Auckland, Auckland 1142, New ZealandAuckland Cancer Society Research Centre, School of Medical Sciences, Faculty of Medical and Health Sciences, University of Auckland, Auckland 1142, New ZealandSchool of Chemical Sciences, University of Auckland, Auckland 1142, New ZealandAuckland Cancer Society Research Centre, School of Medical Sciences, Faculty of Medical and Health Sciences, University of Auckland, Auckland 1142, New ZealandAuckland Cancer Society Research Centre, School of Medical Sciences, Faculty of Medical and Health Sciences, University of Auckland, Auckland 1142, New ZealandAuckland Cancer Society Research Centre, School of Medical Sciences, Faculty of Medical and Health Sciences, University of Auckland, Auckland 1142, New ZealandAuckland Cancer Society Research Centre, School of Medical Sciences, Faculty of Medical and Health Sciences, University of Auckland, Auckland 1142, New ZealandAuckland Cancer Society Research Centre, School of Medical Sciences, Faculty of Medical and Health Sciences, University of Auckland, Auckland 1142, New ZealandExtracellular acidification is an important feature of tumor microenvironments but has yet to be successfully exploited in cancer therapy. The reversal of the pH gradient across the plasma membrane in cells that regulate intracellular pH (pHi) has potential to drive the selective uptake of weak acids at low extracellular pH (pHe). Here, we investigate the dual targeting of low pHe and hypoxia, another key feature of tumor microenvironments. We prepared eight bioreductive prodrugs based on the benzotriazine di-oxide (BTO) nucleus by appending alkanoic or aminoalkanoic acid sidechains. The BTO acids showed modest selectivity for both low pHe (pH 6.5 versus 7.4, ratios 2 to 5-fold) and anoxia (ratios 2 to 8-fold) in SiHa and FaDu cell cultures. Related neutral BTOs were not selective for acidosis, but had greater cytotoxic potency and hypoxic selectivity than the BTO acids. Investigation of the uptake and metabolism of representative BTO acids confirmed enhanced uptake at low pHe, but lower intracellular concentrations than expected for passive diffusion. Further, the modulation of intracellular reductase activity and competition by the cell-excluded electron acceptor WST-1 suggests that the majority of metabolic reductions of BTO acids occur at the cell surface, compromising the engagement of the resulting free radicals with intracellular targets. Thus, the present study provides support for designing bioreductive prodrugs that exploit pH-dependent partitioning, suggesting, however, that that the approach should be applied to prodrugs with obligate intracellular activation.https://www.mdpi.com/1420-3049/24/14/2524bioreductive prodrugsbenzotriazine di-oxidestumor acidosistumor hypoxiapH-dependent partitioningradical chemistrytirapazamineSN30000CEN-209chlorambucilWST-1
collection DOAJ
language English
format Article
sources DOAJ
author Michael P. Hay
Hong Nam Shin
Way Wua Wong
Wan Wan Sahimi
Aaron T.D. Vaz
Pooja Yadav
Robert F. Anderson
Kevin O. Hicks
William R. Wilson
spellingShingle Michael P. Hay
Hong Nam Shin
Way Wua Wong
Wan Wan Sahimi
Aaron T.D. Vaz
Pooja Yadav
Robert F. Anderson
Kevin O. Hicks
William R. Wilson
Benzotriazine Di-Oxide Prodrugs for Exploiting Hypoxia and Low Extracellular pH in Tumors
Molecules
bioreductive prodrugs
benzotriazine di-oxides
tumor acidosis
tumor hypoxia
pH-dependent partitioning
radical chemistry
tirapazamine
SN30000
CEN-209
chlorambucil
WST-1
author_facet Michael P. Hay
Hong Nam Shin
Way Wua Wong
Wan Wan Sahimi
Aaron T.D. Vaz
Pooja Yadav
Robert F. Anderson
Kevin O. Hicks
William R. Wilson
author_sort Michael P. Hay
title Benzotriazine Di-Oxide Prodrugs for Exploiting Hypoxia and Low Extracellular pH in Tumors
title_short Benzotriazine Di-Oxide Prodrugs for Exploiting Hypoxia and Low Extracellular pH in Tumors
title_full Benzotriazine Di-Oxide Prodrugs for Exploiting Hypoxia and Low Extracellular pH in Tumors
title_fullStr Benzotriazine Di-Oxide Prodrugs for Exploiting Hypoxia and Low Extracellular pH in Tumors
title_full_unstemmed Benzotriazine Di-Oxide Prodrugs for Exploiting Hypoxia and Low Extracellular pH in Tumors
title_sort benzotriazine di-oxide prodrugs for exploiting hypoxia and low extracellular ph in tumors
publisher MDPI AG
series Molecules
issn 1420-3049
publishDate 2019-07-01
description Extracellular acidification is an important feature of tumor microenvironments but has yet to be successfully exploited in cancer therapy. The reversal of the pH gradient across the plasma membrane in cells that regulate intracellular pH (pHi) has potential to drive the selective uptake of weak acids at low extracellular pH (pHe). Here, we investigate the dual targeting of low pHe and hypoxia, another key feature of tumor microenvironments. We prepared eight bioreductive prodrugs based on the benzotriazine di-oxide (BTO) nucleus by appending alkanoic or aminoalkanoic acid sidechains. The BTO acids showed modest selectivity for both low pHe (pH 6.5 versus 7.4, ratios 2 to 5-fold) and anoxia (ratios 2 to 8-fold) in SiHa and FaDu cell cultures. Related neutral BTOs were not selective for acidosis, but had greater cytotoxic potency and hypoxic selectivity than the BTO acids. Investigation of the uptake and metabolism of representative BTO acids confirmed enhanced uptake at low pHe, but lower intracellular concentrations than expected for passive diffusion. Further, the modulation of intracellular reductase activity and competition by the cell-excluded electron acceptor WST-1 suggests that the majority of metabolic reductions of BTO acids occur at the cell surface, compromising the engagement of the resulting free radicals with intracellular targets. Thus, the present study provides support for designing bioreductive prodrugs that exploit pH-dependent partitioning, suggesting, however, that that the approach should be applied to prodrugs with obligate intracellular activation.
topic bioreductive prodrugs
benzotriazine di-oxides
tumor acidosis
tumor hypoxia
pH-dependent partitioning
radical chemistry
tirapazamine
SN30000
CEN-209
chlorambucil
WST-1
url https://www.mdpi.com/1420-3049/24/14/2524
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