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Cytostatic potential of novel agents that inhibit the regulation of intracellular pH.

Wong P, Kleemann HW, Tannock IF - Br. J. Cancer (2002)

Bottom Line: Previously available inhibitors of these exchangers were toxic (e.g. 4,4-diisothiocyanstilbene-2,2-disulphonic acid), and/or non-specific (e.g. 5-N-ethyl-N-isopropyl amiloride).Our results suggest that cariporide has similar efficacy and potency to 5-N-ethyl-N-isopropyl amiloride for inhibition of Na(+)/H(+) exchange while S3705 is more potent and efficient than 4,4-diisothiocyanstilbene-2,2-disulphonic acid in inhibiting Na+-dependent Cl(-)/HCO3(-) exchange.Our results indicate that cariporide and S3705 are selective cytostatic agents under in vitro conditions that reflect the slightly acidic microenvironment found in solid tumours.

View Article: PubMed Central - PubMed

Affiliation: Department of Medical Biophysics, Princess Margaret Hospital/Ontario Cancer Institute, University of Toronto, Toronto, M5G 2M9, Canada.

ABSTRACT
Cells within the acidic extracellular environment of solid tumours maintain their intracellular pH (pHi) through the activity of membrane-based ion exchange mechanisms including the Na(+)/H(+) antiport and the Na(+)-dependent Cl(-)/HCO(3)(-) exchanger. Inhibition of these regulatory mechanisms has been proposed as an approach to tumour therapy. Previously available inhibitors of these exchangers were toxic (e.g. 4,4-diisothiocyanstilbene-2,2-disulphonic acid), and/or non-specific (e.g. 5-N-ethyl-N-isopropyl amiloride). Using two human (MCF7, MDA-MB231) and one murine (EMT6) breast cancer cell lines, we evaluated the influence of two new agents, cariporide (an inhibitor of the Na(+)/H(+) antiport) and S3705 (an inhibitor of the Na(+)-dependent Cl(-)/HCO(3)(-) exchanger) on the regulation of intracellular pH (pHi). The cytotoxicity of the two agents was assessed by using clonogenic assays. Our results suggest that cariporide has similar efficacy and potency to 5-N-ethyl-N-isopropyl amiloride for inhibition of Na(+)/H(+) exchange while S3705 is more potent and efficient than 4,4-diisothiocyanstilbene-2,2-disulphonic acid in inhibiting Na+-dependent Cl(-)/HCO3(-) exchange. The agents inhibited the growth of tumour cells when they were incubated at low pHe (7.0-6.8), but were non-toxic to cells grown at doses that inhibited the regulation of pHi. Our results indicate that cariporide and S3705 are selective cytostatic agents under in vitro conditions that reflect the slightly acidic microenvironment found in solid tumours.

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Comparison of the inhibitory effects of DIDS and S3705 on the activity of the Na+ dependent Cl−/ HCO3− exchanger (measured by H+ efflux rate in μM s−1) for (A) MCF7 and (B) EMT6 cells. Experiments were performed in the absence of serum. The results indicated are the mean±s.e.m. of at least three experiments.
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fig2: Comparison of the inhibitory effects of DIDS and S3705 on the activity of the Na+ dependent Cl−/ HCO3− exchanger (measured by H+ efflux rate in μM s−1) for (A) MCF7 and (B) EMT6 cells. Experiments were performed in the absence of serum. The results indicated are the mean±s.e.m. of at least three experiments.

Mentions: Similarly, we compared the efficacy and potency of S3705 and DIDS to inhibit the activity of the Na+-dependent Cl−/HCO3− exchanger. In the absence of 10% FBS, S3705 was more effective and more potent than DIDS (Figure 2Figure 2


Cytostatic potential of novel agents that inhibit the regulation of intracellular pH.

Wong P, Kleemann HW, Tannock IF - Br. J. Cancer (2002)

Comparison of the inhibitory effects of DIDS and S3705 on the activity of the Na+ dependent Cl−/ HCO3− exchanger (measured by H+ efflux rate in μM s−1) for (A) MCF7 and (B) EMT6 cells. Experiments were performed in the absence of serum. The results indicated are the mean±s.e.m. of at least three experiments.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2376112&req=5

fig2: Comparison of the inhibitory effects of DIDS and S3705 on the activity of the Na+ dependent Cl−/ HCO3− exchanger (measured by H+ efflux rate in μM s−1) for (A) MCF7 and (B) EMT6 cells. Experiments were performed in the absence of serum. The results indicated are the mean±s.e.m. of at least three experiments.
Mentions: Similarly, we compared the efficacy and potency of S3705 and DIDS to inhibit the activity of the Na+-dependent Cl−/HCO3− exchanger. In the absence of 10% FBS, S3705 was more effective and more potent than DIDS (Figure 2Figure 2

Bottom Line: Previously available inhibitors of these exchangers were toxic (e.g. 4,4-diisothiocyanstilbene-2,2-disulphonic acid), and/or non-specific (e.g. 5-N-ethyl-N-isopropyl amiloride).Our results suggest that cariporide has similar efficacy and potency to 5-N-ethyl-N-isopropyl amiloride for inhibition of Na(+)/H(+) exchange while S3705 is more potent and efficient than 4,4-diisothiocyanstilbene-2,2-disulphonic acid in inhibiting Na+-dependent Cl(-)/HCO3(-) exchange.Our results indicate that cariporide and S3705 are selective cytostatic agents under in vitro conditions that reflect the slightly acidic microenvironment found in solid tumours.

View Article: PubMed Central - PubMed

Affiliation: Department of Medical Biophysics, Princess Margaret Hospital/Ontario Cancer Institute, University of Toronto, Toronto, M5G 2M9, Canada.

ABSTRACT
Cells within the acidic extracellular environment of solid tumours maintain their intracellular pH (pHi) through the activity of membrane-based ion exchange mechanisms including the Na(+)/H(+) antiport and the Na(+)-dependent Cl(-)/HCO(3)(-) exchanger. Inhibition of these regulatory mechanisms has been proposed as an approach to tumour therapy. Previously available inhibitors of these exchangers were toxic (e.g. 4,4-diisothiocyanstilbene-2,2-disulphonic acid), and/or non-specific (e.g. 5-N-ethyl-N-isopropyl amiloride). Using two human (MCF7, MDA-MB231) and one murine (EMT6) breast cancer cell lines, we evaluated the influence of two new agents, cariporide (an inhibitor of the Na(+)/H(+) antiport) and S3705 (an inhibitor of the Na(+)-dependent Cl(-)/HCO(3)(-) exchanger) on the regulation of intracellular pH (pHi). The cytotoxicity of the two agents was assessed by using clonogenic assays. Our results suggest that cariporide has similar efficacy and potency to 5-N-ethyl-N-isopropyl amiloride for inhibition of Na(+)/H(+) exchange while S3705 is more potent and efficient than 4,4-diisothiocyanstilbene-2,2-disulphonic acid in inhibiting Na+-dependent Cl(-)/HCO3(-) exchange. The agents inhibited the growth of tumour cells when they were incubated at low pHe (7.0-6.8), but were non-toxic to cells grown at doses that inhibited the regulation of pHi. Our results indicate that cariporide and S3705 are selective cytostatic agents under in vitro conditions that reflect the slightly acidic microenvironment found in solid tumours.

Show MeSH
Related in: MedlinePlus