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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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Reverse transcription–PCR of Kir 2.1, herg1 and helk2 transcripts in a representative pool of glioma samples. RNA extraction, RT and PCR amplification of the three transcripts was performed as reported in Materials and Methods. Only samples where a good amplification of the housekeeping gene gapdh (not shown) was achieved were processed for further analysis. DNA marker: 100 bp (New England Biolabs); the ‘no-RT' lane contains a sample of RNA added to the PCR reaction mixture without previous RT. Lane labelled ‘Brain' refers to total human brain RNA (see Materials and Methods). (A) Kir 2.1 transcript; (B) herg1 transcript; (C) helk2 transcript.
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fig3: Reverse transcription–PCR of Kir 2.1, herg1 and helk2 transcripts in a representative pool of glioma samples. RNA extraction, RT and PCR amplification of the three transcripts was performed as reported in Materials and Methods. Only samples where a good amplification of the housekeeping gene gapdh (not shown) was achieved were processed for further analysis. DNA marker: 100 bp (New England Biolabs); the ‘no-RT' lane contains a sample of RNA added to the PCR reaction mixture without previous RT. Lane labelled ‘Brain' refers to total human brain RNA (see Materials and Methods). (A) Kir 2.1 transcript; (B) herg1 transcript; (C) helk2 transcript.

Mentions: The electrophysiological data show that the ion channels under investigation are expressed on the plasma membrane and present usual properties. It was however necessary to complement this biophysical evidence with molecular data. mRNA and protein expression patterns do not always fully overlap; thus, a study based on mere electrophysiological analysis could underestimate the importance and utility of these marker gene. In addition, RT–PCR allows the molecular identification of the ion channels responsible for the ion currents recorded by patch-clamp investigation. To address these issues, we performed an RT–PCR survey of the most likely candidate genes: Kir 2.1, a molecular component of IIRK, known to be highly expressed in cortical astrocytes (Olsen and Sontheimer, 2004), herg1, a molecular component of IhERG, the member of the herg family most frequently expressed by tumour cells (Crociani et al, 2003) and helk2. Representative examples of the PCR-amplified transcripts are reported in Figure 3.


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)

Reverse transcription–PCR of Kir 2.1, herg1 and helk2 transcripts in a representative pool of glioma samples. RNA extraction, RT and PCR amplification of the three transcripts was performed as reported in Materials and Methods. Only samples where a good amplification of the housekeeping gene gapdh (not shown) was achieved were processed for further analysis. DNA marker: 100 bp (New England Biolabs); the ‘no-RT' lane contains a sample of RNA added to the PCR reaction mixture without previous RT. Lane labelled ‘Brain' refers to total human brain RNA (see Materials and Methods). (A) Kir 2.1 transcript; (B) herg1 transcript; (C) helk2 transcript.
© Copyright Policy
Related In: Results  -  Collection

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

fig3: Reverse transcription–PCR of Kir 2.1, herg1 and helk2 transcripts in a representative pool of glioma samples. RNA extraction, RT and PCR amplification of the three transcripts was performed as reported in Materials and Methods. Only samples where a good amplification of the housekeeping gene gapdh (not shown) was achieved were processed for further analysis. DNA marker: 100 bp (New England Biolabs); the ‘no-RT' lane contains a sample of RNA added to the PCR reaction mixture without previous RT. Lane labelled ‘Brain' refers to total human brain RNA (see Materials and Methods). (A) Kir 2.1 transcript; (B) herg1 transcript; (C) helk2 transcript.
Mentions: The electrophysiological data show that the ion channels under investigation are expressed on the plasma membrane and present usual properties. It was however necessary to complement this biophysical evidence with molecular data. mRNA and protein expression patterns do not always fully overlap; thus, a study based on mere electrophysiological analysis could underestimate the importance and utility of these marker gene. In addition, RT–PCR allows the molecular identification of the ion channels responsible for the ion currents recorded by patch-clamp investigation. To address these issues, we performed an RT–PCR survey of the most likely candidate genes: Kir 2.1, a molecular component of IIRK, known to be highly expressed in cortical astrocytes (Olsen and Sontheimer, 2004), herg1, a molecular component of IhERG, the member of the herg family most frequently expressed by tumour cells (Crociani et al, 2003) and helk2. Representative examples of the PCR-amplified transcripts are reported in Figure 3.

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