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The Na+, K+, ATPase inhibitor ouabain sensitizes resistant human malignant pleural mesothelioma cells to cisplatin by increased Bak expression
Umeå University, Faculty of Medicine, Medical Biosciences.
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URN: urn:nbn:se:umu:diva-2140OAI: diva2:139975
Available from: 2007-02-16 Created: 2007-02-16 Last updated: 2010-01-13Bibliographically approved
In thesis
1. Manipulation of potassium ion fluxes to induce apoptosis in lung cancer cells
Open this publication in new window or tab >>Manipulation of potassium ion fluxes to induce apoptosis in lung cancer cells
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Apoptosis is a special form of cell death that if non-functional may lead to diseases such as cancer. A reduction of the intracellular potassium ion (K+) content is necessary for activating enzymes important for the execution of apoptosis. Pharmacological modulation of K+ fluxes to reduce intracellular K+ in cancer cells might therefore force the cells into apoptosis and decrease tumour cell mass.

Human malignant pleural mesothelioma (MPM) is a form of cancer often caused by asbestos exposure. Although asbestos has been banned in the Western World, the incidence of MPM is expected to increase. Cisplatin is the first-line chemotherapy for MPM, but acquired resistance to the drug is a clinical problem.

This thesis is mainly based on work with the human malignant pleural mesothelioma cell line (P31 wt) and a cisplatin-resistant sub-line (P31 res). The aim was to first characterize K+ fluxes in P31 wt and P31 res cells, and then manipulate them in order to reduce intracellular K+ and induce apoptosis with K+ manipulation alone or in combination with cisplatin.

Characterization of K+ fluxes in P31 wt cells showed that: 1) ouabain, a digitalis-like drug, and specific blocker of the Na+, K+, ATPase pump, effectively inhibited K+ uptake, 2) bumetanide, a diuretic, and an inhibitor of the Na+, K+, 2Cl-¬-cotransporter, had a transient effect on K+ uptake, and 3) the antifungal drug amphotericin B stimulated K+ efflux.

In order to determine intracellular K+ content, the potassium-binding fluorescent probe PBFI-AM was used in a 96-well plate assay. After a 3-h incubation with ouabain, with or without bumetanide, combined with amphotericin B, the intracellular K+ content was reduced in P31 wt cells but not in P31 res cells.

Ouabain induced apoptosis in both P31 wt and P31 res cells. P31 res cells were sensitized to cisplatin by ouabain, since 10 mg/L cisplatin in combination with ouabain induced about the same percentage of apoptotic cells as 40 mg/L cisplatin. Apoptosis was executed via caspase-3 activation in both P31 wt and P31 res cells. Amphotericin B enhanced ouabain-induced apoptosis in P31 wt cells via caspase-9 activation, with increased caspase-3 activation and DNA fragmentation as consequences. Ouabain-induced apoptosis in P31 res cells was executed via increased expression of pro-apoptotic Bak. The combination of cisplatin with ouabain and amphotericin B was stressful to both P31 wt and P31 res cells, since SAPK/JNK a known factor in stress-induced apoptosis was activated.

In conclusion, K+ flux manipulation with clinical used drugs can induce apoptosis per se and also enhance cisplatin-induced apoptosis in P31 wt and P31 res cells.

Place, publisher, year, edition, pages
Umeå: Medicinsk biovetenskap, 2007. 33 p.
Umeå University medical dissertations, ISSN 0346-6612 ; 1086
Apoptosis, Cisplatin, Intracellular K+ content, Mesothelioma, Na+ K+ ATPase pump
National Category
Other Clinical Medicine
urn:nbn:se:umu:diva-1014 (URN)978-91-7264-264-5 (ISBN)
Public defence
2007-03-16, Betula, 6M, Umeå universitet, Umeå, 09:00 (English)
Available from: 2007-02-16 Created: 2007-02-16 Last updated: 2009-05-13Bibliographically approved

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