ABSTRACT
AIM: To explore the effects of chromodomain protein 8 (CBX8) on the proliferation and apoptosis of human glioma cells.METHODS: The expression of CBX8 in the tissues and cells was detected by Western blot and RT-qPCR.The overexpression (Flag-CBX8) and silencing (sh-CBX8) vectors of CBX8 were constructed and transfected into glioma T98G cells and U87MG cells.The cell proliferation was detected by MTT assay and BrdU staining.The cell apoptosis was analyzed by flow cytometry.The protein expression of Rb/E2F1 was detected by Western blot.RESULTS: Compared with normal brain tissues and astrocytes, the expression of CBX8 was increased in the glioma tissues and glioma cells.Overexpression of CBX8 promoted the cell proliferation, inhibited the cell apoptosis, and upregulated the protein levels of Rb/E2F1.On the contrary, silencing of CBX8 inhibited the cell proliferation, promoted the cell apoptosis, and decreased the protein levels of Rb/E2F1 in the T98G cells and U87MG cells.Moreover, the expression of cyclin D1 and Bcl-2/Bax ratio were reduced after transfection with sh-E2F1 in the T98G cells and U87MG cells.CONCLUSION: CBX8 may regulate the proliferation and apoptosis of glioma cells through Rb/E2F1 pathway.
ABSTRACT
Os gliomas são tumores cerebrais definidos patologicamente pela presença de células com características histológicas e imuno-histoquímicas que evidenciam diferenciação glial. Dentre eles, os astrocitomas são os mais frequentes em adultos. Estes tumores normalmente apresentam infiltração difusa no tecido adjacente, são resistentes aos tratamentos e têm uma tendência natural para a progressão maligna. O tratamento padrão atual consiste na realização de ressecção cirúrgica do tecido tumoral seguida de radio e quimioterapia concomitantes, porém o prognóstico permanece extremamente pobre. O quimioterápico padrão-ouro no tratamento de GBM é o agente alquilante de DNA temozolamida (TMZ). Entretanto, os danos induzidos pela TMZ podem ser revertidos pela ação da maquinaria de reparo de DNA, impedindo a morte celular e levando à resistência do GBM ao tratamento. No presente estudo correlacionamos a expressão dos genes ATM, BRCA2, BRIP1, EXO1, NEIL3, RAD54L e XRCC2, envolvidos em reparo de DNA e sabidamente superexpressos em GBM, com a resistência das linhagens celulares T98G e U87MG ao tratamento com TMZ. Mostramos que a linhagem T98G é a mais resistente ao tratamento com TMZ, e apresenta superexpressão de BRCA2, BRIP1, EXO1, NEIL3, RAD54L e XRCC2 e sub-expressão de ATM. Vimos também que a linhagem U87MG, mais sensível ao tratamento com TMZ, apresenta expressão reduzida dos genes ATM, BRCA2 e EXO1. Portanto, estes dados sugerem uma correlação positiva entre a expressão de genes de reparo de DNA e a resistência das células de GBM à TMZ.(AU)
Gliomas are brain tumors pathologically defined by the presence of cells with histological and immunohistochemical characteristics of glial differentiation. Among them, astrocytomas are the most common in adults. These tumors usually show diffuse infiltration into adjacent tissue, are resistant to treatment and have a natural tendency to malignant progression. The current standard treatment consists in surgical removal of the tumor followed by radiotherapy and concurrent chemotherapy. However, the prognosis remains extremely poor. The first line chemotherapy for GBM treatment is the DNA alkylating agent temozolamide (TMZ). Nevertheless, TMZ-induced damage can be reversed by the action of DNA repair machinery that prevents cell death and leads to relapse. In this study we correlated the expression of the DNA damage-signaling gene, ATM kinase, and the DNA repair genes BRCA2, BRIP1, EXO1, NEIL3, RAD54L and XRCC2, with the resistance of T98G and U87MG cell lines to TMZ. T98G cells were more resistant to TMZ treatment and showed overexpression of all DNA repair genes, while ATM kinase was down regulated. We also observed that U87MG cells, more sensitive to TMZ, have reduced expression of ATM, BRCA2 and EXO1. Therefore, these data suggest a positive correlation between the expression of DNA repair genes and the resistance of GBM cells to TMZ.(AU)
Subject(s)
Humans , Male , Adult , Brain Neoplasms , Glioblastoma , Alkylating Agents/therapeutic useABSTRACT
Aim To investigate the effect of asiatic acid on apoptosis and autophagy in human glioblastoma T98G cells. Methods MTT colorimetry was employed to assay the cellular proliferating activity. The fluores-cence microscope and Hoechst 33258 staining were used to detect the morphological changes. The cell ap-optosis and autophagy were analyzed by flow cytometry with Annexin-V/7-AAD and MDC staining respective-ly. The expressions of associated proteins were detected by Western blot to analyze the mechanism of apoptosis and autophagy. Results MTT assay showed that the growth of T 9 8 G cells was inhibited by asiatic acid ( IC50 =46. 3 μmol · L-1 ) . Annexin V/7-AAD stai-ning and Western blot revealed that asiatic acid in-duced apoptosis in T98 G cells by reducing the expres-sion of Akt, decreasing the mitochondrial membrane potential, and increasing the expression of Caspase-3. MDC staining and Western blot showed that the per-centage of MDC-positive cells was decreased and the expressions of Beclin-1 , LC3-II and Atgs were inhibi-ted by asiatic acid treatment. 5 μmol·L-1 chloroquine was used to up-regulate the expressions of LC3-Ⅱand Beclin-1 . Asiatic acid-inhibited autophagy was blocked and the total apoptotic rate was reduced remarkably. Conclusion Asiatic acid suppresses T98 G cells pro-liferation by inducing apoptosis and inhibiting cell au-tophagy, and the very role of inhibiting autophagy could promote apoptosis to a certain extent.