Phenotype-dependent apoptosis signalling in mesothelioma cells after selenite exposure

<p>Abstract</p> <p>Background</p> <p>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.</p> <p>Methods</p> <p>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.</p> <p>Results</p> <p>In both cell lines, 10 μM 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.</p> <p>Conclusion</p> <p>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.</p

The consequences of interactions between dispersal distance and resolution of habitat clustering for dispersal success

Habitat clustering results from processes of habitat loss and fragmentation, which operate at different resolutions and with different intensities, e.g. forest clear-cutting or thinning. Individual movements also vary at different spatial scales according to landscape structure and species dispersal strategies. Disentangling the relative impact of habitat loss and fragmentation on the long-term survival of species requires understanding how clustering at one resolution interacts with the amount of habitat, dispersal distance and clustering at other resolutions, to affect dispersal success. We addressed this problem by quantifying the magnitude of these interactions and how they were affected by the intensity of habitat removal. Individual-based simulations were conducted on artificial fractal landscapes where the intensity of habitat removal and the amount of clustering were varied independently at two nested resolutions, while the total amount of habitat in the landscape was controlled for. We show that the way the amount of habitat, the dispersal distance and the amount of clustering affect dispersal success depends on the resolution at which habitat clustering occurs, the intensity at which habitat is removed, and the strength of habitat selection. Our findings highlight: (a) the importance of explicitly considering scale-dependent biological responses to landscape change; and (b) the need to identify the appropriate scale at which to manage fragmentation, thus avoiding mismatches between the scale of ecological processes and the scale of management