Influence of extracellular pH on the cytotoxicity and DNA damage of a series of indolequinone compounds

R M Phillips, T H Ward

Research output: Contribution to journalArticle

11 Citations (Scopus)

Abstract

BACKGROUND: The existence of an acidic extracellular pH (pHe) within solid tumours is regarded as a potential target for drug development. The indolequinone EO9 has a complex mechanism of action which includes enhanced potency under acidic pHe conditions in vitro. In order to identify compounds which have a simpler mechanism of action where activation under acidic pHe is the predominant mechanism of toxicity, this study has determined the cytotoxic properties of a series of analogues of EO9 under both physiological and acidic pHe conditions.

MATERIALS AND METHODS: H460 human NSCLC cells were exposed to EO compounds under acidic (pH 6.04) and physiological (pH 7.24) pHe conditions for one hour and chemosensitivity assessed 4 days later using the MTT assay. For compounds of interest, DNA damage (both single strand breaks and cross links) in H460 cells was determined using the comet assay.

RESULTS: All the compounds tested were more potent under acidic pHe conditions although a broad range of enhancement ratios (defined as the IC50 at pHe 7.24/IC50 at pHe 6.04) were obtained ranging from 3.25 to 116.53. The activity of EO72 was significantly enhanced under acidic conditions and activity was associated with a pH dependent increase in DNA cross linking in H460 cells. As EO72 is a poor substrate for purified human DT-diaphorase, pHe conditions appear to be a major factor determining cell kill.

CONCLUSIONS: This study has identified several compounds whose cytotoxic properties in vitro are pHe dependent with EO72 emerging as the lead compound on the basis of the magnitude of the pH dependent chemosensitivity and the fact that it is a poor substrate for DT-diaphorase. Further studies are required to determine whether or not EO72 has suitable pharmacokinetic properties to allow it to reach regions of low pHe within solid tumours.

LanguageEnglish
Pages1795-801
Number of pages7
JournalAnticancer Research
Volume21
Issue number3B
Publication statusPublished - 11 Aug 2001
Externally publishedYes

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Indolequinones
apaziquone
DNA Damage
NAD(P)H Dehydrogenase (Quinone)
Inhibitory Concentration 50
Comet Assay
Neoplasms
Pharmacokinetics
DNA
Pharmaceutical Preparations

Cite this

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title = "Influence of extracellular pH on the cytotoxicity and DNA damage of a series of indolequinone compounds",
abstract = "BACKGROUND: The existence of an acidic extracellular pH (pHe) within solid tumours is regarded as a potential target for drug development. The indolequinone EO9 has a complex mechanism of action which includes enhanced potency under acidic pHe conditions in vitro. In order to identify compounds which have a simpler mechanism of action where activation under acidic pHe is the predominant mechanism of toxicity, this study has determined the cytotoxic properties of a series of analogues of EO9 under both physiological and acidic pHe conditions.MATERIALS AND METHODS: H460 human NSCLC cells were exposed to EO compounds under acidic (pH 6.04) and physiological (pH 7.24) pHe conditions for one hour and chemosensitivity assessed 4 days later using the MTT assay. For compounds of interest, DNA damage (both single strand breaks and cross links) in H460 cells was determined using the comet assay.RESULTS: All the compounds tested were more potent under acidic pHe conditions although a broad range of enhancement ratios (defined as the IC50 at pHe 7.24/IC50 at pHe 6.04) were obtained ranging from 3.25 to 116.53. The activity of EO72 was significantly enhanced under acidic conditions and activity was associated with a pH dependent increase in DNA cross linking in H460 cells. As EO72 is a poor substrate for purified human DT-diaphorase, pHe conditions appear to be a major factor determining cell kill.CONCLUSIONS: This study has identified several compounds whose cytotoxic properties in vitro are pHe dependent with EO72 emerging as the lead compound on the basis of the magnitude of the pH dependent chemosensitivity and the fact that it is a poor substrate for DT-diaphorase. Further studies are required to determine whether or not EO72 has suitable pharmacokinetic properties to allow it to reach regions of low pHe within solid tumours.",
keywords = "Antineoplastic Agents/pharmacology, Aziridines/pharmacology, Carcinoma, Non-Small-Cell Lung/drug therapy, Coloring Agents/pharmacology, Comet Assay, DNA Damage, Dose-Response Relationship, Drug, Humans, Hydrogen-Ion Concentration, Indolequinones, Indoles/pharmacology, Inhibitory Concentration 50, Lung Neoplasms/drug therapy, Models, Chemical, Recombinant Proteins/metabolism, Tetrazolium Salts/pharmacology, Thiazoles/pharmacology, Time Factors, Tumor Cells, Cultured",
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pages = "1795--801",
journal = "Anticancer Research",
issn = "0250-7005",
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}

Influence of extracellular pH on the cytotoxicity and DNA damage of a series of indolequinone compounds. / Phillips, R M; Ward, T H.

In: Anticancer Research, Vol. 21, No. 3B, 11.08.2001, p. 1795-801.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Influence of extracellular pH on the cytotoxicity and DNA damage of a series of indolequinone compounds

AU - Phillips, R M

AU - Ward, T H

PY - 2001/8/11

Y1 - 2001/8/11

N2 - BACKGROUND: The existence of an acidic extracellular pH (pHe) within solid tumours is regarded as a potential target for drug development. The indolequinone EO9 has a complex mechanism of action which includes enhanced potency under acidic pHe conditions in vitro. In order to identify compounds which have a simpler mechanism of action where activation under acidic pHe is the predominant mechanism of toxicity, this study has determined the cytotoxic properties of a series of analogues of EO9 under both physiological and acidic pHe conditions.MATERIALS AND METHODS: H460 human NSCLC cells were exposed to EO compounds under acidic (pH 6.04) and physiological (pH 7.24) pHe conditions for one hour and chemosensitivity assessed 4 days later using the MTT assay. For compounds of interest, DNA damage (both single strand breaks and cross links) in H460 cells was determined using the comet assay.RESULTS: All the compounds tested were more potent under acidic pHe conditions although a broad range of enhancement ratios (defined as the IC50 at pHe 7.24/IC50 at pHe 6.04) were obtained ranging from 3.25 to 116.53. The activity of EO72 was significantly enhanced under acidic conditions and activity was associated with a pH dependent increase in DNA cross linking in H460 cells. As EO72 is a poor substrate for purified human DT-diaphorase, pHe conditions appear to be a major factor determining cell kill.CONCLUSIONS: This study has identified several compounds whose cytotoxic properties in vitro are pHe dependent with EO72 emerging as the lead compound on the basis of the magnitude of the pH dependent chemosensitivity and the fact that it is a poor substrate for DT-diaphorase. Further studies are required to determine whether or not EO72 has suitable pharmacokinetic properties to allow it to reach regions of low pHe within solid tumours.

AB - BACKGROUND: The existence of an acidic extracellular pH (pHe) within solid tumours is regarded as a potential target for drug development. The indolequinone EO9 has a complex mechanism of action which includes enhanced potency under acidic pHe conditions in vitro. In order to identify compounds which have a simpler mechanism of action where activation under acidic pHe is the predominant mechanism of toxicity, this study has determined the cytotoxic properties of a series of analogues of EO9 under both physiological and acidic pHe conditions.MATERIALS AND METHODS: H460 human NSCLC cells were exposed to EO compounds under acidic (pH 6.04) and physiological (pH 7.24) pHe conditions for one hour and chemosensitivity assessed 4 days later using the MTT assay. For compounds of interest, DNA damage (both single strand breaks and cross links) in H460 cells was determined using the comet assay.RESULTS: All the compounds tested were more potent under acidic pHe conditions although a broad range of enhancement ratios (defined as the IC50 at pHe 7.24/IC50 at pHe 6.04) were obtained ranging from 3.25 to 116.53. The activity of EO72 was significantly enhanced under acidic conditions and activity was associated with a pH dependent increase in DNA cross linking in H460 cells. As EO72 is a poor substrate for purified human DT-diaphorase, pHe conditions appear to be a major factor determining cell kill.CONCLUSIONS: This study has identified several compounds whose cytotoxic properties in vitro are pHe dependent with EO72 emerging as the lead compound on the basis of the magnitude of the pH dependent chemosensitivity and the fact that it is a poor substrate for DT-diaphorase. Further studies are required to determine whether or not EO72 has suitable pharmacokinetic properties to allow it to reach regions of low pHe within solid tumours.

KW - Antineoplastic Agents/pharmacology

KW - Aziridines/pharmacology

KW - Carcinoma, Non-Small-Cell Lung/drug therapy

KW - Coloring Agents/pharmacology

KW - Comet Assay

KW - DNA Damage

KW - Dose-Response Relationship, Drug

KW - Humans

KW - Hydrogen-Ion Concentration

KW - Indolequinones

KW - Indoles/pharmacology

KW - Inhibitory Concentration 50

KW - Lung Neoplasms/drug therapy

KW - Models, Chemical

KW - Recombinant Proteins/metabolism

KW - Tetrazolium Salts/pharmacology

KW - Thiazoles/pharmacology

KW - Time Factors

KW - Tumor Cells, Cultured

UR - http://ar.iiarjournals.org/

M3 - Article

VL - 21

SP - 1795

EP - 1801

JO - Anticancer Research

T2 - Anticancer Research

JF - Anticancer Research

SN - 0250-7005

IS - 3B

ER -