Selective Targeting to Glioma with Nucleic Acid Aptamers.

Malignant glioma is characterised by a rapid growth rate and high capacity for invasive infiltration to surrounding brain tissue; hence, diagnosis and treatment is difficult and patient survival is poor. Aptamers contribute a promising and unique technology for the in vitro imaging of live cells and tissues, with a potentially bright future in clinical diagnostics and therapeutics for malignant glioma. The binding selectivity, uptake capacity and binding target of two DNA aptamers, SA43 and SA44, were investigated in glioma cells and patient tissues. The binding assay showed that SA43 and SA44 bound with strong affinity (Kd, 21.56 ± 4.60 nM and Kd, 21.11 ± 3.30 nM respectively) to the target U87MG cells. Quantitative analysis by flow cytometry showed that the aptamers were able to actively internalise in U87MG and 1321N1 glioma cells compared to the non-cancerous and non-glioma cell types. Confocal microscopy confirmed staining in the cytoplasm, and co-localisation studies with endoplasmic reticulum, Golgi apparatus and lysosomal markers suggested internalisation and compartmentalisation within the endomembrane system. Both aptamers selectively bound to Ku 70 and Ku 80 DNA repair proteins as determined by aptoprecipitation (AP) followed by mass spectrometry analysis and confirmation by Western blot. In addition, aptohistochemical (AHC) staining on paraffin embedded, formalin fixed patient tissues revealed that the binding selectivity was significantly higher for SA43 aptamer in glioma tissues (grade I, II, III and IV) compared to the non-cancerous tissues, whereas SA44 did not show selectivity towards glioma tissues. The results indicate that SA43 aptamer can differentiate between glioma and non-cancerous cells and tissues and therefore, shows promise for histological diagnosis of glioma.

Role of histone lysine methyltransferases SUV39H1 and SETDB1 in gliomagenesis: modulation of cell proliferation, migration, and colony formation.

Posttranslational modifications of histones are considered as critical regulators of gene expression, playing significant role in the pathogenesis and progression of tumors. Trimethylation of histone 3 lysine 9 (H3K9me3), a repressed transcription mark, is mainly regulated by the histone lysine N-methyltransferases (HKMTs), SUV39H1 and SETDB1. The present study investigated the implication of these HKMTs in glioma progression. SUV39H1 and SETDB1 expression was upregulated in glioma cell lines (GOS-3, 1321N1, T98G, U87MG) and in glioma tissues compared to normal brain being positively correlated with grade and histological malignancy. Suppression by siRNA of the two HKMTs for 24 and 48 h resulted in significantly reduced proliferation of GOS-3 and T98G glioma cells with siSUV39H1 effects been most prominent. Furthermore, HKMTs knockdown-induced apoptosis with a high rate of apoptotic cells have been observed after siSUV39H1 and siSETDB1 for both cell lines. Additionally, suppression of the two HKMTs reduced cell migration and clonogenic ability of both glioma cell lines. Our results indicate overexpression of SETDB1 and SUV39H1 in gliomas. Treatments that alter HKMT expression affect the proliferative and apoptotic rates in glioma cells as well as their migratory and colony formation capacity. These data suggest that both HKMTs and especially SUV39H1 may serve as novel biomarkers for future therapeutic targeting of these tumors.

Cell-type-dependent thyroid hormone effects on glioma tumor cell lines.

Purpose. The present study investigated the potential effects of long-term T3 treatment on glioma tumor cell lines. Thyroid hormone action on cell growth, differentiation and survival during development may be of therapeutic relevance Methods and Results 1321N1 cell line, an astrocytoma grade II, and U87MG, a glioblastoma grade IV, were exposed for 2 and 4 days in medium deprived of T3 and in medium containing 1 nM T3. T3 promoted re-differentiation in both cell lines. However, T3 increased cell proliferation in 1321N1 (2 days) which declined thereafter (4 days) while in U87MG resulted in suppression of cell proliferation. At the molecular level, a 2.9 fold increase in the expression of TRα1 receptor was observed in U87MG versus 1321N1, P < 0.05. TRß1 receptor was undetectable. These changes corresponded to a distinct pattern of T3-induced kinase signaling activation; T3 had no effect on ERK activation in both cell lines but significantly increased phospho-Akt levels in 1321N1. Conclusion. In conclusion, T3 can re-differentiate glioma tumor cells, whereas its effect on cell proliferation appears to be dependent on the type of tumor cell line with aggressive tumors being more sensitive to T3. TRα1 receptor may, at least in part, be implicated in this response.