Determination of clonal pattern and the role of TRPM2/TRPM7 ion channels in malignant mesothelioma

Abstract

Malignant mesothelioma (MM) is an aggressive cancer of the mesothelial lining of pleura, peritoneum and other body cavities. It has been associated with long term exposure to asbestos and erionite. It is a relatively rare, but deadly disease and current therapies have still a very poor clinical outcome. This thesis presents two sets of data through which different aspects of malignant mesothelioma were explored. The first study was performed by the methylation-based HUMARA assay on a panel of primary MM tumors, to identify the clonal pattern of MM. The results indicate the polyclonal origin of the MM tumors analyzed (n = 6). The second study was focused on Ca2+ and Mg2+ permeable ion channels, Melastatin Related Transient Receptor Potential 2 (TRPM2) and Melastatin Related Transient Receptor Potential 7 (TRPM7), to investigate the role of these channels both in the transformation of primary human mesothelial cells (HM) upon exposure to asbestos fibers and in motility and survival of MM cells. A time-and dose-dependent correlation between TRPM2 and TRPM7 mRNA levels and cell exposure to asbestos fibers was observed. However, while TRPM2 protein was expressed at different extents in both HM and MM cells, the TRPM7 protein was present in all MM cells but in none of the HM primary cultures tested. Moreover, in MM cells infected by lentiviral particles encoding shRNA targeting TRPM7, no differences were observed in proliferation, wound healing and migration rates, compared to scramble shRNA transduced cells. On the contrary, in MM cells transduced with shRNA targeting TRPM2, the same cancer hallmarks were significantly higher than in uninfected cells or in controls infected with scramble shRNA. In summary, the results indicate that TRPM2 has a protective role against HM transformation upon asbestos exposure and influences the maintenance of the transformed phenotype of MM cells, possibly affecting the mechanisms of cell death.