Publications

Abstract Enhancer of zeste homolog 2 (EZH2), a catalytic component of polycomb repressive complex 2 (PRC2), is commonly overexpressed or mutated in many cancer types, both of hematological and solid nature. Till now, plenty of EZH2 small molecule inhibitors have been developed and some of them have already been tested in clinical trials. Most of these inhibitors, however, are effective only in limited cases in the context of EZH2 gain‐of‐function mutated tumors such as lymphomas. Other cancer types with aberrant EZH2 expression and function require alternative approaches for successful treatment. One possibility is to exploit synthetic lethal strategy, which is based on the phenomenon that concurrent loss of two genes is detrimental but the deletion of either of them leaves cell viable. In the context of EZH2/PRC2, the most promising synthetic lethal target seems to be SWItch/Sucrose Non‐Fermentable chromatin remodeling complex (SWI/SNF), which is known to counteract PRC2 functions. SWI/SNF is heavily involved in carcinogenesis and its subunits have been found mutated in approximately 20% of tumors of different kinds. In the current review, we summarize the existing knowledge of synthetic lethal relationships between EZH2/PRC2 and components of the SWI/SNF complex and discuss in detail the potential application of existing EZH2 inhibitors in cancer patients harboring mutations in SWI/SNF proteins. We also highlight recent discoveries of EZH2 involvement in tumor microenvironment regulation and consequences for future therapies. Although clinical studies are limited, the fundamental research might help to understand which patients are most likely to benefit from therapies using EZH2 inhibitors.

<p>Effect of miR-206 on expression of differentiation markers in SMS-CTR eRMS (SMS) and CW9019 aRMS (CW) cell lines.</p>

<p>PDF - 3176KB, Characterization of B16F10 wt and msVEGFR2 expressing clones 13.3 and 16.4 tumors in vivo.</p>

<title>Abstract</title> The nuclear factor erythroid 2-related factor 2 (Nrf2) is considered as a master cytoprotective factor regulating the expression of genes encoding anti-oxidant, anti-inflammatory, and detoxifying proteins. The role of Nrf2 in the pathophysiology of skeletal muscles has been evaluated in different experimental models, however, due to inconsistent data, we aimed to investigate how Nrf2 transcriptional deficiency (Nrf2^tKO) affects muscle functions both in an acute and chronic injury. The acute muscle damage was induced in mice of two genotypes – WT and Nrf2^tKO mice by cardiotoxin (CTX) injection. To investigate the role of Nrf2 in chronic muscle pathology,<italic> mdx </italic>mice that share genetic, biochemical, and histopathological features with Duchenne muscular dystrophy (DMD) were crossed with mice lacking transcriptionally active Nrf2 and double knockouts (<italic>mdx</italic>/Nrf2^tKO) were generated. To worsen the dystrophic phenotype, the analysis of disease pathology was also performed in aggravated conditions, by applying a long-term treadmill test.We have observed slightly increased muscle damage in Nrf2^tKO mice after CTX injection. Nevertheless, transcriptional ablation of Nrf2 in <italic>mdx</italic> mice did not significantly aggravate the most deleterious, pathological hallmarks of DMD related to degeneration, inflammation, fibrotic scar formation, angiogenesis, and the number and proliferation of satellite cells in non-exercised conditions. On the other hand, upon chronic exercises, the degeneration and inflammatory infiltration of the gastrocnemius muscle, but not diaphragm, turned to be increased in Nrf2^tKO<italic>mdx</italic> in comparison to <italic>mdx</italic> mice. <italic> </italic>In conclusion, the lack of transcriptionally active Nrf2 influences moderately muscle pathology in acute CTX-induced muscle injury and chronic DMD mouse model, without affecting muscle functionality. Hence, in general, we demonstrated that the deficiency of Nrf2 transcriptional activity has no profound impact on muscle pathology in various models of muscle injury.

Abstract Rhabdomyosarcoma (RMS) is an aggressive soft tissue cancer characterized by disturbed myogenic differentiation. Here we report a role for the oxidative stress response factor HO-1 in progression of RMS. We found that HO-1 was elevated and its effector target miR-206 decreased in RMS cell lines and clinical primary tumors of the more aggressive alveolar phenotype (aRMS). In embryonal RMS (eRMS), HO-1 expression was induced by Pax3/7-FoxO1, an aRMS hallmark oncogene, followed by a drop in miR-206 levels. Inhibition of HO-1 by tin protoporphyrin (SnPP) or siRNA downregulated Pax3/7-FoxO1 target genes and induced a myogenic program in RMS. These effects were not mediated by altered myoD expression; instead, cells with elevated HO-1 produced less reactive oxygen species, resulting in nuclear localization of HDAC4 and miR-206 repression. HO-1 inhibition by SnPP reduced growth and vascularization of RMS tumors in vivo accompanied by induction of miR-206. Effects of SnPP on miR-206 expression and RMS tumor growth were mimicked by pharmacologic inhibition of HDAC. Thus, HO-1 inhibition activates an miR-206–dependent myogenic program in RMS, offering a novel therapeutic strategy for treatment of this malignancy. Cancer Res; 76(19); 5707–18. ©2016 AACR.

Endothelium has an immense impact on the tissue regeneration, regulation of atherosclerosis and tumour growth. Therefore, modification of endothelial cell differentiation and function seems a promising target for many therapies. MicroRNAs are small RNA molecules, which recognize and inhibit specific mRNAs. In that way, they can regulate and orchestrate whole signalling pathways. It has been shown that microRNAs can fine-tune endothelial cell functions since they have either pro- and antiangiogenic activity, regulate expression of e.g. adhesion molecules or nitric oxide synthase. Furthermore, microRNAs modulate differentiation of embryonic stem cells to endothelial cells and their further specialization towards specific vascular bed. This review focuses mainly on the influence of microRNA on the angiogenesis and endothelial cell differentiation.

Through hypoxia-inducible factor 1 (HIF-1), hypoxia regulates the expression of numerous genes and is a potent inducer of angiogenesis. However, interleukin-8 (IL-8), an important angiogenic mediator, has been reported to be downregulated by HIF-1, although the mechanisms have not been elucidated. HIF-1 was induced in human endothelial cells by hypoxia and dimethyloxaloylglycine (DMOG). Interestingly, both hypoxia and DMOG attenuated IL-8 expression, and a similar effect has been obtained by adenoviral overexpression of the stable form of HIF-1alpha. Heme oxygenase-1 (HO-1) expression was also downregulated by HIF-1 induction. This suggests similar mechanisms of regulation of IL-8 and HO-1, indicating the involvement of Nrf2, a transcription factor previously linked to hypoxia-mediated inhibition of HO-1. Indeed, HIF-1-mediated downregulation of both IL-8 and HO-1 was associated with both lowered Nrf2 expression and induction of Bach1, a repressor of Nrf2 transcriptional activity. Accordingly, overexpression of Nrf2 reversed the inhibitory effect of HIF-1 on IL-8 and HO-1 expression. However, neither overexpression of HO-1 nor HO-1 inhibition affected IL-8 synthesis. The data indicate that HIF-1-dependent inhibition of IL-8 expression is caused by downregulation of Nrf2. However, expression of IL-8 is independent of HO-1. Cross-talk between HIF-1 and Nrf2 may influence the outcome of anti-angiogenic therapies aimed at targeting HIF-1. Antioxid.