Targeting the Akt-pathway to improve radiosensitivity in glioblastoma.

Glioblastoma multiforme (GMB) is the most malignant and common type of all astrocytic tumors. Current standard of care entails maximum surgical resection of the tumor, followed by radiotherapy and chemotherapy, usually by the alkylating agent Temozolomide (TMZ). Despite this aggressive combination therapy, the survival rate of GBM patients is still low. Deregulation of the phosphatidylinositol 3-kinase (PI3K) / Akt pathway is a frequent occurrence in GBM. Activation of the PI3K-Akt pathway results in disturbance of control of cell growth and cell survival, which contributes to a competitive growth advantage, metastatic competence as well as to therapy resistance. The PI3K-Akt pathway is therefore an attractive therapeutic target in GBM, because it serves as a convergence point for malignant processes and intervention might overcome resistance to chemotherapy and radiation. The present review shows the importance of Akt in GBM and its role in the DNA damage response. Furthermore, an overview is given of specific inhibitors of Akt which are currently being tested in preclinical and in early phase clinical studies.

Glutamate promotes cell growth by EGFR signaling on U-87MG human glioblastoma cell line.

Accumulating evidences suggest that glutamate plays a key role in the proliferation and invasion of malignant glioblastoma (GBM) tumors. It has been shown that GBM cells release and exploit glutamate for proliferation and invasion through AMPA glutamate receptors. Additionally, amplification of the epidermal growth factor receptor (EGFR) gene occurs in 40-50% of GBM. Since, PI3K/Akt is considered one of the main intracellular pathways involved in EGFR activation, AKT functions could trigger EGFR signaling. Thus, we investigated whether EGFR-phospho-Akt pathway is involved on the glutamate inducing U-87MG human GBM cell line proliferation. For these purpose, we treated the U-87MG cell line with 5 to 200 mM of glutamate and assessed the number of viable cells by trypan blue dye exclusion test. An increase in cell number (50%) was found at 5 mM glutamate, while the addition of DNQX (500 microM), an antagonist of AMPA receptor, inhibited the effect of glutamate on the U87-MG cells proliferation. Also, at 5 mM glutamate we observed an increase on the EGFR and phospho-Akt contents evaluated by immunohistochemistry. Moreover, U-87MG cells treated with glutamate exhibited an increase about 2 times in the EGFR mRNA expression. While, in the presence of the anti-EGFR gefitinib (50 muM) or the PI3K inhibitor wortmannin (5 muM), the U-87MG proliferation was restored to control levels. Together, our data suggest that glutamate signaling mediated by AMPA receptor induces U-87MG human GBM cell line proliferation via EGFR-phospho-Akt pathway.

Expressão imuno-histoquímica das metaloproteinases 2 e 9 não está associada à progressão do carcinoma de células escamosas de esôfago / Metalloproteinases 2 and 9 immunohistochemistry expression is not associated to esophageal squamous cell carcinoma progression

INTRODUÇÃO: O carcinoma de células escamosas do esôfago está entre os tipos mais agressivos de câncer e de pior prognóstico. As metaloproteinases de matriz (MMPs), especialmente as MMP-2 e MMP-9, vêm sendo utilizadas para avaliação prognóstica do câncer, associadas a invasão, tamanho e crescimento tumoral. OBJETIVO: O presente estudo visa investigar as expressões imuno-histoquímicas de MMP-2 e MMP-9, avaliando se existe correlação entre sua expressão e o estadiamento tumoral, invasão vascular, invasão local (pT) e diferenciação tumoral no carcinoma de células escamosas de esôfago. MATERIAL E MÉTODO: Foi realizado um estudo retrospectivo utilizando 31 blocos de parafina contendo tumores de carcinoma escamoso esofágico, obtidas por esofagectomias realizadas entre 1998 e 2003, no Hospital Universitário de Santa Maria (HUSM). Os cortes histológicos foram submetidos à reação imuno-histoquímica, com sistema de amplificação por polímero não-biotinilado Novolink para detecção de MMP-2 e MMP-9. RESULTADOS: A avaliação da MMP-2 apresentou positividade fraca em apenas cinco casos, não demonstrando correlação com as variáveis estudadas. Também não foram observadas associações significativas entre as variáveis do estudo e o grau de expressão imuno-histoquímica da MMP-9. CONCLUSÃO: A expressão imuno-histoquímica das MMP-2 e MMP-9 não parece ser influenciada pelos parâmetros investigados. Nesse sentido, estudos adicionais são necessários para melhor compreensão de sua associação aos fatores prognósticos do carcinoma de células escamosas de esôfago.

INTRODUCTION: Esophageal squamous cell carcinoma is an aggressive malignant neoplasia with poor prognosis. The expression of matrix metalloproteinases (MMPs), mainly 2 and 9, has been used for the prognostic evaluation of cancer in association with tumor invasion, size and tumoral growth analysis. OBJECTIVE: The aim of the present study was to investigate the immunohistochemical expression of MMP-2 and MMP-9 and evaluate if there is an association between their expression and tumor staging, vascular invasion, local invasion (pT) and tumoral differentiation in esophageal squamous cell carcinoma. MATERIAL AND METHODS: We conducted a retrospective study using 31 paraffin-embedded specimens of esophageal squamous cell carcinoma obtained by esophagectomies performed at Santa Maria University Hospital, Rio Grande do Sul State, Brazil between 1998 and 2003. The histological sections were immunohistochemically studied using a non-biotinylated Novolink system for MMP-2 and MMP-9 detection. RESULTS: MMP-2 immunohistochemical expression was detected only in 5 cases and did not demonstrate correlation with the variables analyzed. Furthermore, MMP-9 immunohistochemical expression was not significantly associated with the other variables. CONCLUSION: MMP-2 and MMP-9 immunohistochemical expression does not seem to be influenced by the variables reported in this study. Thus further investigations are required to a better understanding of their association with the prognostic factors of esophageal squamous cell carcinoma.