Cooperative effects of Janus and Aurora kinase inhibition by CEP701 in cells expressing Jak2V617F

in Journal of Cellular and Molecular Medicine (2013), 17(2), 265-276

The Janus kinase 2 mutant V617F occurs with high frequency in myeloproliferative neoplasms. Further mutations affecting the Janus kinase family have been discovered mostly in leukaemias and in ... [more ▼]

The Janus kinase 2 mutant V617F occurs with high frequency in myeloproliferative neoplasms. Further mutations affecting the Janus kinase family have been discovered mostly in leukaemias and in myeloproliferative neoplasms. Owing to their involvement in neoplasia, inflammatory diseases and in the immune response, Janus kinases are promising targets for kinase inhibitor therapy in these disease settings. Various quantitative assays including two newly developed screening assays were used to characterize the function of different small-molecule compounds in cells expressing Jak2V617F. A detailed comparative analysis of different Janus kinase inhibitors in our quantitative assays and the subsequent characterization of additional activities demonstrated for the first time that the most potent Jak2 inhibitor in our study, CEP701, also targets Aurora kinases. CEP701 shows a unique combination of both activities which is not found in other compounds also targeting Jak2. Furthermore, colony forming cell assays showed that Janus kinase 2 inhibitors preferentially suppressed the growth of erythroid colonies, whereas inhibitors of Aurora kinases preferentially blocked myeloid colony growth. CEP701 demonstrated a combined suppression of both colony types. Moreover, we show that combined application of a Janus and an Aurora kinase inhibitor recapitulated the effect observed for CEP701 but might allow for more flexibility in combining both activities in clinical settings, e.g. in the treatment of myeloproliferative neoplasms. The newly developed screening assays are high throughput compatible and allow an easy detection of new compounds with Janus kinase 2 inhibitory activity. © 2012 The Authors. Published by Foundation for Cellular and Molecular Medicine/Blackwell Publishing Ltd. [less ▲]

The actin filament cross-linker L-plastin confers resistance to TNF-alpha in MCF-7 breast cancer cells in a phosphorylation-dependent manner.

in Journal of Cellular and Molecular Medicine (2010), 14(6A), 1264-75

We used a tumour necrosis factor (TNF)-alpha resistant breast adenocarcinoma MCF-7 cell line to investigate the involvement of the actin cytoskeleton in the mechanism of cell resistance to this cytokine ... [more ▼]

We used a tumour necrosis factor (TNF)-alpha resistant breast adenocarcinoma MCF-7 cell line to investigate the involvement of the actin cytoskeleton in the mechanism of cell resistance to this cytokine. We found that TNF resistance correlates with the loss of cell epithelial properties and the gain of a mesenchymal phenotype, reminiscent of an epithelial-to-mesenchymal transition (EMT). Morphological changes were associated with a profound reorganization of the actin cytoskeleton and with a change in the repertoire of expressed actin cytoskeleton genes and EMT markers, as revealed by DNA microarray-based expression profiling. L-plastin, an F-actin cross-linking and stabilizing protein, was identified as one of the most significantly up-regulated genes in TNF-resistant cells. Knockdown of L-plastin in these cells revealed its crucial role in conferring TNF resistance. Importantly, overexpression of wild-type L-plastin in TNF-sensitive MCF-7 cells was sufficient to protect them against TNF-mediated cell death. Furthermore, we found that this effect is dependent on serine-5 phosphorylation of L-plastin and that non-conventional protein kinase C isoforms and the ceramide pathway may regulate its phosphorylation state. The protective role of L-plastin was not restricted to TNF-alpha resistant MCF-7 cells because a correlation between the expression of L-plastin and the resistance to TNF-alpha was observed in other breast cancer cell lines. Together, our study discloses a novel unexpected role of the actin bundling protein L-plastin as a cell protective protein against TNF-cytotoxicity. [less ▲]

IL-24: a classic cytokine and/or a potential cure for cancer?

in Journal of Cellular and Molecular Medicine (2008), 12(6A), 2505-2510

IL-24, a member of the IL-10 family of cytokines, is produced by monocytes and Th2 cells. Interestingly, immune cells do not appear to express specific IL-24 receptor chains (IL-20R1/IL-20R2 and IL-22R/IL ... [more ▼]

IL-24, a member of the IL-10 family of cytokines, is produced by monocytes and Th2 cells. Interestingly, immune cells do not appear to express specific IL-24 receptor chains (IL-20R1/IL-20R2 and IL-22R/IL-20R2), it is therefore unlikely that IL-24 has classical immune-modulating properties. Skin, on the other hand, seems to represent a major target tissue for IL-24 and related cytokines such as IL-19, -20, and -22. However, the initial interest in IL-24 did not arise from its physiological signalling properties through its cognate receptors but rather because of its tentative ability to selectively kill different cancer cells. In an attempt to further investigate the signalling events underlying the IL-24-induced cancer cell death, we found that melanoma cell lines did not react in the expected and previously described way. Using several different forms and delivery modes of IL-24, we were unable to detect any apoptosis-inducing properties of this cytokine in melanoma cells. In the present "Point of view" we will briefly summarise these findings and put them in context of published reports stating that IL-24 might be a long sought after treatment for several types of cancer. [less ▲]