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Published on: June 16, 2019
Phenotype-dependent apoptosis signalling in mesothelioma cells after selenite exposure
Gustav Nilsonne1, Eric Olm, Adam Szulkin
1Department of Laboratory Medicine, Division of Pathology, Karolinska Institutet, Stockholm, Sweden. gustav.nilsonne@ki.se
Background:
Selenite is a promising anticancer agent which has been shown to induce apoptosis in malignant mesothelioma cells in a phenotype-dependent manner, where cells of the chemoresistant sarcomatoid phenotype are more sensitive.
Methods:
In this paper, we investigate the apoptosis signalling mechanisms in sarcomatoid and epithelioid mesothelioma cells after selenite treatment. Apoptosis was measured with the Annexin-PI assay. The mitochondrial membrane potential, the expression of Bax, Bcl-XL, and the activation of caspase-3 were assayed with flow cytometry and a cytokeratin 18 cleavage assay. Signalling through JNK, p38, p53, and cathepsins B, D, and E was investigated with chemical inhibitors. Furthermore, the expression, nuclear translocation and DNA-binding activity of p53 was investigated using ICC, EMSA and the monitoring of p21 expression as a downstream event. Levels of thioredoxin (Trx) were measured by ELISA.
Results:
In both cell lines, 10 microM selenite caused apoptosis and a marked loss of mitochondrial membrane potential. Bax was up-regulated only in the sarcomatoid cell line, while the epithelioid cell line down-regulated Bcl-XL and showed greater caspase-3 activation. Nuclear translocation of p53 was seen in both cell lines, but very little p21 expression was induced. Chemical inhibition of p53 did not protect the cells from apoptosis. p53 lost its DNA binding ability after selenite treatment and was enriched in an inactive form. Levels of thioredoxin decreased after selenite treatment. Chemical inhibition of MAP kinases and cathepsins showed that p38 and cathepsin B had some mediatory effect while JNK had an anti-apoptotic role.
Conclusion:
We delineate pathways of apoptosis signalling in response to selenite, showing differences between epithelioid and sarcomatoid mesothelioma cells. These differences may partly explain why sarcomatoid cells are more sensitive to selenite.
Insights
Selenite induces apoptosis in mesothelioma cells, with sarcomatoid cells being more sensitive due to distinct signaling pathways. This study clarifies selenite
Area of Science:
- Oncology
- Cell Biology
- Biochemistry
Background:
- Selenite demonstrates anticancer potential, selectively inducing apoptosis in malignant mesothelioma cells.
- Sarcomatoid mesothelioma cells exhibit higher sensitivity to selenite compared to epithelioid cells.
Purpose of the Study:
- To investigate the distinct apoptosis signaling mechanisms activated by selenite in sarcomatoid and epithelioid mesothelioma cell lines.
- To elucidate the role of p53, MAP kinases, and cathepsins in selenite-induced apoptosis.
Main Methods:
- Apoptosis induction and mitochondrial membrane potential were assessed using Annexin-PI assay and flow cytometry.
- Expression of apoptosis-related proteins (Bax, Bcl-XL), caspase-3 activation, p53, p21, and thioredoxin (Trx) were analyzed.
- Involvement of signaling pathways (JNK, p38, p53) and cathepsins was investigated using chemical inhibitors, ICC, EMSA, and ELISA.
Main Results:
- Selenite treatment induced apoptosis and mitochondrial dysfunction in both cell lines.
- Differential regulation of Bax and Bcl-XL, and greater caspase-3 activation were observed in sarcomatoid cells.
- p53 nuclear translocation occurred, but p53 DNA-binding activity was lost, and thioredoxin levels decreased; p38 and cathepsin B showed a mediatory role, while JNK exhibited an anti-apoptotic function.
Conclusions:
- Distinct apoptosis signaling pathways are activated by selenite in epithelioid and sarcomatoid mesothelioma cells.
- These pathway differences contribute to the observed higher sensitivity of sarcomatoid cells to selenite, offering potential therapeutic insights.
