title: Phenotype-dependent apoptosis signalling in mesothelioma cells after selenite exposure.
abstract: 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.
  
  
  CONCLUSIONS
  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.
authors: Department of Laboratory Medicine, Division of Pathology, Karolinska Institutet, Stockholm, Sweden. gustav.nilsonne@ki.se
authors: Gustav
authors: G
authors: Nilsonne
authors: Eric
authors: E
authors: Olm
authors: Adam
authors: A
authors: Szulkin
authors: Filip
authors: F
authors: Mundt
authors: Agnes
authors: A
authors: Stein
authors: Branka
authors: B
authors: Kocic
authors: Anna-Klara
authors: AK
authors: Rundlöf
authors: Aristi P
authors: AP
authors: Fernandes
authors: Mikael
authors: M
authors: Björnstedt
authors: Katalin
authors: K
authors: Dobra
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D053148:Caspase 3 / Q000378:metabolism; D049109:Cell Proliferation; D005434:Flow Cytometry; D006801:Humans; D007124:Immunoenzyme Techniques; D008156:Luciferases / Q000378:metabolism; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D008654:Mesothelioma / Q000188:drug therapy* / Q000473:pathology*; D010641:Phenotype; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D018038:Sodium Selenite / Q000494:pharmacology*; D013879:Thioredoxins; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D051028:bcl-2-Associated X Protein / Q000378:metabolism
chemical_list: D019253:Proto-Oncogene Proteins c-bcl-2; D016159:Tumor Suppressor Protein p53; D051028:bcl-2-Associated X Protein; D013879:Thioredoxins; D008156:Luciferases; D053148:Caspase 3; D018038:Sodium Selenite