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Proteins of STAT family belongs to the transcription factors. Through their binding to the DNA specific sites and consequent regulation of transcription of various genes, these signaling proteins play an important role in many cell functions. Recent studies demonstrated persistent activation of STATs and loss of their natural inhibitors SOCS and PIAS in various human cancers. There is also evidence that experimental pharmacologic or genetic modulation of their function mignt by a new approach in anticancer treatment. The aim of this study was in vitro assesment and analysis of expression of STATs, SOCS and PIAS in glioblastoma cell lines undergoing treatment by PPARgamma agonists/antagonists because PPARgamma and STATs are tightly regulated by an overlapping set of nuclear regulatory proteins. We further analysed immunohistochemical expression of these proteins in vivo, with its correlation to grading in various brain tumors. The results of in vitro study showed decreased expression of phosphorylated form of STAT3 and increase of its inhibitors SOCS3 and PIAS3 in glioblastoma cell lines after treatment with IC50 of PPARgamma agonist ciglitazone. In vivo study failed to reveal changes in STAT3 and SOCS3 expression in either low and high grade astrocytomas, however we detect lower expression of STAT2 in low grade astrocytomas when comparing with high grade astrocytomas and lower expression of STAT3 in ependymomas when comparing with anaplastic ones. The results showed existing relationship between STAT and PPARgamma signaling in glial tumors and further suppport expected important role of STATs in regulation of growth and differentiation in these tumors.

The most frequent alterations found in astrocytomas are two major groups of signaling proteins: the cell cycle and the growth factor-regulated signaling pathways. The aim of our study was to detect changes in expression of the following proteins: the tumor suppressors PTEN, p53, and p21Waf1/Cip1, glial fibrillary acidic protein (GFAP, as a marker of astroglial differentiation), the phosphorylated form of protein kinase B/Akt (PKB/Akt), which is downstream to the epidermal growth factor receptor (EGFR), and MDM2, which degrades p53. Paraffin-embedded astrocytoma tissue samples from 89 patients were divided into low grade (grade I-II; 42 samples) and high grade astrocytomas (grade III-IV; 47 samples). Mouse monoclonal antibodies against GFAP, PTEN, PKB/Akt phosphorylated on serine 473, EGFR, p53, p21Waf1/Cip1 and MDM2 were used, followed by standard indirect immunohistochemical method. EGFR protein was detected in 29 % of low grade and in 60 % of high grade astrocytomas. The expression of phosphorylated PKB/Akt was found in roughly the same proportions: in 86% of low grade and in 79% of high grade astrocytomas. PTEN was not found in most of astrocytomas, 64% of low grade and 74% of high grade tumors showed no PTEN staining. Overexpression of the mutated form of p53 or loss of p53 expression, however, was found in about 63% in both groups of astrocytomas with no differences between them. GFAP expression was decreased in tumor astrocytes compared to normal astrocytes and this decreased with grading. GFAP positive tumor cells were detected in only 50% of low grade, and 32% of high grade astrocytomas. The level of MDM2 expression was similar in both grades. Loss of p21Waf1/Cip1 expression was shown in 20% of low and in 45% of high grade tumors. In the subgroup of high grade tumors with wild type p53, 86% showed p21Waf1/Cip1 expression, whereas in the subgroup of high grade tumors with altered p53, only 35% displayed p21Waf1/Cip1. We conclude that EGFR expression increases with astrocytoma grading. EGFR activation may subsequently lead to stimulation of the PKB/Akt survival pathway. PTEN defects may also participate in aggressive tumor behaviour through activation of the PKB/Akt pathway. The alteration of p53 supports the finding that the cell cycle regulation is also disrupted during development of astrocytomas. The changes in PTEN and p53 expression, and activation of PKB/Akt are events in the early stages of astrocytomagenesis. EGFR is one of the factors, which drives the progression of astrocytomas from low to high grade stage.

The nuclear receptors PPARs (peroxisome proliferator-activated receptors) are transcription factors activated by specific ligands. PPARs play an important role in carcinogenesis, inflammation, atherosclerosis, lipid metabolism and diabetes. There is evidence that activation of PPARs by specific ligands is able to suppress the growth of different types of human cancer by mechanisms including the growth arrest, apoptosis and induction of differentiation, although the detailed signalling pathways have not been completely elucidated to date. The aim of our study was to determine whether synthetic ligands of PPARalpha and PPARgamma could affect the viability, proliferation, differentiation, apoptosis and expression of some cell cycle related proteins in glial tumor cell lines. The study was performed on human glioblastoma cell lines U-87 MG, T98G, A172 and U-118 MG. Cell lines were treated by ligands of PPARalpha (bezafibrate, gemfibrozil) and PPARgamma (ciglitazone). MTT, flow cytometry, TUNEL assay and immunoblotting were used for detection of changes in cell viability, proliferation, differentiation and apoptosis. Bezafibrate, ciglitazone and gemfibrozil inhibited viability of glioblastoma cell lines. The synthetic ligands significantly reduced or induced the expression of cyclins, p27Kip1, p21Waf1/Cip1, MDM-2, Bcl-2, Bax, PARP, Caspase 3, androgen receptors, etc. and did not affect the expression of the differentiation marker GFAP. Flow cytometry confirmed arrest of the cell cycle although the detection of apoptosis was controversial. Apart from hypolipidemic and hypoglycaemic effects, PPAR ligands may also have significant cytostatic effects of potential use in anticancer treatment.

Modern molecular biology methods allow a more precise analysis of the biological characteristics of tumors and, consequently, a more precise treatment plan. The determination of apoptotic rate and expression of apoptosis-related proteins belong among the important prognostic/diagnostic markers in many tumors. The validity of these factors had not yet been sufficiently analyzed in astroglial tumors. The aim of this work was therefore to study mutual relationships between apoptotic rate, expression of apoptosis-regulating proteins and some clinical and histopathological data. The TUNEL method was used for the determination of apoptosis in 44 astroglial tumor specimens. The percentage of TUNEL positive cells was expressed by the TUNEL index (TI). The TI data was compared with the immunohistochemically detected expression of proteins involved in apoptosis (BCL-2, FAS, FAS-L, and caspase 1), with grading, age, proliferative activity (assessed by PCNA expression analysis) and overall survival of patients. The statistical evaluation of results was done by two-way sample analysis of variance. We have demonstrated significantly higher values of both TI and expression of FAS-L and caspase 1 in low grade tumors, which were characterized by a longer survival, lower average age and a lower expression of PCNA. FAS-L expression correlated significantly with the expression of the caspase 1. No significant difference was found between the expression of BCL-2 and FAS. These results suggest that the determination of TI in astroglial tumors may be an important prognostic marker. The expression of FAS-L and caspase 1 in low grade astroglial tumors could indicate the increased readiness to apoptosis via the FAS/FAS-L cascade.

Hormone receptor expression in human breast cancer cells does not always reflect tumor response to therapy. Thus, relations between hormone receptor status and other parameters need further examination. The aim of this study was to test the ability of estrogen receptors (ER) to induce progesterone receptor (PR) synthesis as well as to test their role in the regulation of cell proliferation. Measurement of the relation between expressions of ER and the estrogen receptor related protein p29 (ERRP) was a further goal. The results show that some hormone receptor phenotypes are closely related to tumor proliferative activity: in the ER-group, especially ER-PR-phenotype, proliferative activity shows no obvious relationship to phenotype status, suggesting that proliferation in this group probably is not under estrogen control, while in the ER+ group, PR expression was related to reduced proliferation. There was no clear association between ERRP and nuclear ER but the highest ERRP expression was most closely related to ER negative (ER-) or slightly positive (ER +/-) hormone receptor statuses. Tumors with these phenotypes are known to have a poorer prognosis. The conclusion drawn is that simultaneous estimation of proliferative activity, ERRP p29 expression and a comparison with ER/PR hormone receptor phenotype, could provide pathologist with a valuable tool for predicting hormone response and prognosis in breast cancer patients.

The immunohistochemically detected expression of p53, BCL-2, MDM-2 and PCNA proteins in samples of tumor tissues of 42 patients with astrocytomas or glioblastoma multiforme was statistically compared to degree of malignancy and overall survival. We found relation between p53 protein expression and survival in the high grade astrocytomas group (more cases of p53 immunonegative tumors with longer survival), and significantly higher BCL-2 protein expression as well as significantly higher MDM-2 protein expression in the group of low grade astrocytomas. PCNA protein expression showed any relation to tumor grade or survival. Despite the rather small number of samples these results support the hypothesis that MDM-2 protein may be a potent regulator of functional p53, expressed in low grade astrocytoma only.