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Introduction: Subependymal nodule (SEN) and subependymal giant cell astrocytoma (SEGA) are brain lesions frequently found in tuberous sclerosis (TS). As about 10-15% of SENs enlarge and transform into SEGAs, we examined here the possible mechanism of the phenomenon., Material and Methods: Using Western blot we studied 1 SEN and 3 SEGA samples; SEN and 1 SEGA came from the same TS patient. We evaluated e.g. the activation of the phosphorylated forms of proteins belonging to Akt, Erk and mTOR pathways., Results: Differences in Erk pathway activation between SEN and SEGA were found. There was no upregulation of p-Erk, p-Mek or p-RSK1 in the SEN specimen, whilst we found these proteins to be significantly uptriggered in SEGA samples. Also, for the first time, we found p-Akt, p-GSK3 and p-PDK1 upregulated in both SEN and SEGA from the same TS patient., Conclusions: Our current study shows for the first time the possible mechanism of SEN/SEGA transformation, where Erk pathway hyperactivation seems to be significant. We hypothesize that SEN/SEGA transformation may depend on Erk potentiation.

Ganglioglioma (GG) is a low-grade neoplasm, often associated with intractable epilepsy in pediatric patients. Available data suggest a relationship between GG and other glioneuronal lesions. So far, little is known about activation of kinases belonging to the mTor (mammalian target of rapamycin) pathway, although its upregulation is often found in brain tumors. Involvement of mTor kinase is responsible for excessive proliferation. In the current study we focused on the possible role of the Erk/Mapk (extracellular-signal-regulated kinase/mitogen-activated protein kinase) pathway in GG development. Eight GG tumors were resected from pediatric patients. Collected data reveal activation of proteins from the Erk pathway: Mek (extracellular regulated protein kinase kinase/mitogen-activated protein kinase kinase), Erk, Rsk1 (ribosomal S6 kinase 1), Rheb (Ras homolog enriched in brain) and Msk1 (mitogen- and stress-activated protein kinase 1), as detected by the western blot method. Moreover, activation of other proteins upstream of mTor - IGF-1R β (insulin-like growth factor 1β receptor), INR β (insulin receptor β), Akt/PKB (protein kinase B) - or downstream - 4E-BP1 (eukaryotic translation initiation factor 4E-binding protein 1) and rpS6 (ribosomal protein S6) - was also confirmed.

Atypical teratoid/rhabdoid tumor (AT/RT) is a highly malignant tumor typically appearing in childhood. Differentiation of AT/RT from other brain tumors is extremely important because of grim prognosis and necessity of more aggressive treatment. On the other hand, investigation is essential for new therapeutic agents based on continuously developing knowledge of AT/RT development mechanisms. Most AT/RT tumors have been demonstrated to harbor a chromosome 22 mutation in the region of hSNF5/INI1 gene, whose protein product participates in chromatin remodeling. Although the presence of this mutation is rather undisputable, additional molecular pathways underlying AT/RT development are poorly understood. Current paper discusses current views on molecular pathophysiology of the tumor., (© 2010 The Author(s). European Journal of Neurology © 2010 EFNS.)

A typical teratoid/rhabdoid tumor (AT/RT) is a highly malignant childhood brain tumor. Most AT/RTs are shown to contain chromosome 22 mutation in the region of hSNF5/INI1 gene, whose protein product participates in chromatin remodeling. Although the presence of this mutation is well described, molecular pathways underlying AT/RT development are poorly, if at all, understood. In the current paper we evaluate a case of AT/RT with special consideration of two pathways often implicated in tumor development: protein kinase B (PKB or Akt) and extracellular signal-regulated kinase (Erk). First, we confirmed expression of typical protein pattern being unique for AT/RT, including epithelial membrane antigen, S-100 and glial fibrillary acidic protein. In molecular analyses we tested the sample for activity of Akt and Erk kinase cascade. We found that Erk pathway signaling in the tumor was not upregulated. Neither c-Raf, MAPK nor Erk were hyperphosphorylated. On the other hand, we detected significant phosphorylation of Akt, phosphoinositide-dependent kinase-1 (PDK1) and glycogen synthase kinase 3 (GSK-3). At the same time, inhibitor of Akt pathway, phosphatase and tensin homolog (PTEN), was not upregulated. These results strongly support the hypothesis that Akt pathway contributes to chromatin remodeling disruption, promoting malignant transformation of AT/RT.

Medulloblastoma (MB) is the most common malignant brain tumour in children. Its aetiology is unknown, although several signalling pathways controlling cell proliferation are thought to participate in the progress of the neoplasm. Mutations of the genes encoding proteins participating in the pathways triggered by embryonic growth factors like Sonic hedgehog (Shh) or WNT are often found in MB. Another model of MB development is overexpression or mutation of several types of growth factor receptors, including IGF-IR, EGF-R and PDGFR, that have the ability to activate cellular kinases responsible for promoting cell proliferation. In order to test this hypothesis, in the current paper we tested the activation of two kinases, Akt/PKB (protein kinase B) and Erk (extracellular signal-regulated kinase) and their substrates in 10 sporadic medulloblastoma cases. We show that MBs are a highly heterogeneous group of tumours that show upregulation of various signalling pathways. Nevertheless, both Akt and Erk may contribute to the progression of MB, triggering, at least in some cases, the mTOR (mammalian target of rapamycin) pathway, controlling translation of several cell cycle-related proteins. We hypothesize that Akt and Erk activation may also be associated with downregulation of protein phosphatase 2A (PP2A).