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hERG1 channels are overexpressed in glioblastoma multiforme and modulate VEGF secretion in glioblastoma cell lines.

Masi A, Becchetti A, Restano-Cassulini R, Polvani S, Hofmann G, Buccoliero AM, Paglierani M, Pollo B, Taddei GL, Gallina P, Di Lorenzo N, Franceschetti S, Wanke E, Arcangeli A - Br. J. Cancer (2005)

Bottom Line: We studied the expression and properties of K(+) channels in primary cultures obtained from surgical specimens: human ether a gò-gò related (hERG)1 voltage-dependent K(+) channels, which have been found to be overexpressed in various human cancers, and human ether a gò-gò-like 2 channels, that share many of hERG1's biophysical features.The expression pattern of these two channels was compared to that of the classical inward rectifying K(+) channels, IRK, that are widely expressed in astrocytic cells and classically considered a marker of astrocytic differentiation.In our study, hERG1 was found to be specifically overexpressed in high-grade astrocytomas, that is, glioblastoma multiforme (GBM).

View Article: PubMed Central - PubMed

Affiliation: Department of Experimental Pathology and Oncology, University of Firenze, Italy.

ABSTRACT
Recent studies have led to considerable advancement in our understanding of the molecular mechanisms that underlie the relentless cell growth and invasiveness of human gliomas. Partial understanding of these mechanisms has (1) improved the classification for gliomas, by identifying prognostic subgroups, and (2) pointed to novel potential therapeutic targets. Some classes of ion channels have turned out to be involved in the pathogenesis and malignancy of gliomas. We studied the expression and properties of K(+) channels in primary cultures obtained from surgical specimens: human ether a gò-gò related (hERG)1 voltage-dependent K(+) channels, which have been found to be overexpressed in various human cancers, and human ether a gò-gò-like 2 channels, that share many of hERG1's biophysical features. The expression pattern of these two channels was compared to that of the classical inward rectifying K(+) channels, IRK, that are widely expressed in astrocytic cells and classically considered a marker of astrocytic differentiation. In our study, hERG1 was found to be specifically overexpressed in high-grade astrocytomas, that is, glioblastoma multiforme (GBM). In addition, we present evidence that, in GBM cell lines, hERG1 channel activity actively contributes to malignancy by promoting vascular endothelial growth factor secretion, thus stimulating the neoangiogenesis typical of high-grade gliomas. Our data provide important confirmation for studies proposing the hERG1 channel as a molecular marker of tumour progression and a possible target for novel anticancer therapies.

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WAY inhibition of IhERG in different experimental conditions. Whole-cell IhERG traces were studied as tail currents at −120 mV (for 80 ms), preceded by 10 s conditioning steps at 0 and −70 mV, as shown in the inset. Currents were measured in the absence (control) or presence of the indicated concentration of WAY. (A) Effects of 1 and 40 μM WAY diluted in (1) SES (upper panels); (2) culture medium incubated 15 min at 37°C, 5% CO2 (CM, middle panels); (3) CM incubated 24 h in the dishes containing the cells, at 37°C and 5% CO2 (CM 24 h, lower panels). (B) Percentage of IHERG block, calculated as explained in Materials and Methods, in the experimental conditions indicated in (A).
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fig7: WAY inhibition of IhERG in different experimental conditions. Whole-cell IhERG traces were studied as tail currents at −120 mV (for 80 ms), preceded by 10 s conditioning steps at 0 and −70 mV, as shown in the inset. Currents were measured in the absence (control) or presence of the indicated concentration of WAY. (A) Effects of 1 and 40 μM WAY diluted in (1) SES (upper panels); (2) culture medium incubated 15 min at 37°C, 5% CO2 (CM, middle panels); (3) CM incubated 24 h in the dishes containing the cells, at 37°C and 5% CO2 (CM 24 h, lower panels). (B) Percentage of IHERG block, calculated as explained in Materials and Methods, in the experimental conditions indicated in (A).

Mentions: Furthermore, we determined the dose dependence of WAY inhibition on IhERG, in the experimental conditions adopted for measuring VEGF secretion. In fact, the efficacy of hERG blockers might be altered by protein binding of the drug (Webster et al, 2001), or perhaps progressive degradation during long incubation. Thus, we tested the efficacy of WAY on IhERG after diluting the drug: (1) in SES, normally used for our patch-clamp experiments; (2) in the culture medium used for growing glioma cells during secretion experiments (CM); (3) in CM medium preincubated for 24 h in the same dishes containing the cells (CM 24 h). These experiments were carried out on our HEK-hERG1 stable cell line. IhERG was studied as tail current at −120 mV, after conditioning for 10 s at 0 mV (to produce maximal activation), and, subsequently, at −70 mV (to produce strong current deactivation, as further control that we were specifically measuring IhERG). As reported in Figure 7, 1 μM WAY produced almost complete inhibition only when diluted in SES (average percentage IhERG block was 90±2%). On the other hand, the effect of 1 μM WAY was drastically reduced after dilution in CM or CM 24 h. On the contrary, 40 μM WAY was strongly effective in all the experimental conditions that we have applied.


hERG1 channels are overexpressed in glioblastoma multiforme and modulate VEGF secretion in glioblastoma cell lines.

Masi A, Becchetti A, Restano-Cassulini R, Polvani S, Hofmann G, Buccoliero AM, Paglierani M, Pollo B, Taddei GL, Gallina P, Di Lorenzo N, Franceschetti S, Wanke E, Arcangeli A - Br. J. Cancer (2005)

WAY inhibition of IhERG in different experimental conditions. Whole-cell IhERG traces were studied as tail currents at −120 mV (for 80 ms), preceded by 10 s conditioning steps at 0 and −70 mV, as shown in the inset. Currents were measured in the absence (control) or presence of the indicated concentration of WAY. (A) Effects of 1 and 40 μM WAY diluted in (1) SES (upper panels); (2) culture medium incubated 15 min at 37°C, 5% CO2 (CM, middle panels); (3) CM incubated 24 h in the dishes containing the cells, at 37°C and 5% CO2 (CM 24 h, lower panels). (B) Percentage of IHERG block, calculated as explained in Materials and Methods, in the experimental conditions indicated in (A).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2361632&req=5

fig7: WAY inhibition of IhERG in different experimental conditions. Whole-cell IhERG traces were studied as tail currents at −120 mV (for 80 ms), preceded by 10 s conditioning steps at 0 and −70 mV, as shown in the inset. Currents were measured in the absence (control) or presence of the indicated concentration of WAY. (A) Effects of 1 and 40 μM WAY diluted in (1) SES (upper panels); (2) culture medium incubated 15 min at 37°C, 5% CO2 (CM, middle panels); (3) CM incubated 24 h in the dishes containing the cells, at 37°C and 5% CO2 (CM 24 h, lower panels). (B) Percentage of IHERG block, calculated as explained in Materials and Methods, in the experimental conditions indicated in (A).
Mentions: Furthermore, we determined the dose dependence of WAY inhibition on IhERG, in the experimental conditions adopted for measuring VEGF secretion. In fact, the efficacy of hERG blockers might be altered by protein binding of the drug (Webster et al, 2001), or perhaps progressive degradation during long incubation. Thus, we tested the efficacy of WAY on IhERG after diluting the drug: (1) in SES, normally used for our patch-clamp experiments; (2) in the culture medium used for growing glioma cells during secretion experiments (CM); (3) in CM medium preincubated for 24 h in the same dishes containing the cells (CM 24 h). These experiments were carried out on our HEK-hERG1 stable cell line. IhERG was studied as tail current at −120 mV, after conditioning for 10 s at 0 mV (to produce maximal activation), and, subsequently, at −70 mV (to produce strong current deactivation, as further control that we were specifically measuring IhERG). As reported in Figure 7, 1 μM WAY produced almost complete inhibition only when diluted in SES (average percentage IhERG block was 90±2%). On the other hand, the effect of 1 μM WAY was drastically reduced after dilution in CM or CM 24 h. On the contrary, 40 μM WAY was strongly effective in all the experimental conditions that we have applied.

Bottom Line: We studied the expression and properties of K(+) channels in primary cultures obtained from surgical specimens: human ether a gò-gò related (hERG)1 voltage-dependent K(+) channels, which have been found to be overexpressed in various human cancers, and human ether a gò-gò-like 2 channels, that share many of hERG1's biophysical features.The expression pattern of these two channels was compared to that of the classical inward rectifying K(+) channels, IRK, that are widely expressed in astrocytic cells and classically considered a marker of astrocytic differentiation.In our study, hERG1 was found to be specifically overexpressed in high-grade astrocytomas, that is, glioblastoma multiforme (GBM).

View Article: PubMed Central - PubMed

Affiliation: Department of Experimental Pathology and Oncology, University of Firenze, Italy.

ABSTRACT
Recent studies have led to considerable advancement in our understanding of the molecular mechanisms that underlie the relentless cell growth and invasiveness of human gliomas. Partial understanding of these mechanisms has (1) improved the classification for gliomas, by identifying prognostic subgroups, and (2) pointed to novel potential therapeutic targets. Some classes of ion channels have turned out to be involved in the pathogenesis and malignancy of gliomas. We studied the expression and properties of K(+) channels in primary cultures obtained from surgical specimens: human ether a gò-gò related (hERG)1 voltage-dependent K(+) channels, which have been found to be overexpressed in various human cancers, and human ether a gò-gò-like 2 channels, that share many of hERG1's biophysical features. The expression pattern of these two channels was compared to that of the classical inward rectifying K(+) channels, IRK, that are widely expressed in astrocytic cells and classically considered a marker of astrocytic differentiation. In our study, hERG1 was found to be specifically overexpressed in high-grade astrocytomas, that is, glioblastoma multiforme (GBM). In addition, we present evidence that, in GBM cell lines, hERG1 channel activity actively contributes to malignancy by promoting vascular endothelial growth factor secretion, thus stimulating the neoangiogenesis typical of high-grade gliomas. Our data provide important confirmation for studies proposing the hERG1 channel as a molecular marker of tumour progression and a possible target for novel anticancer therapies.

Show MeSH
Related in: MedlinePlus