Calcineurin is a Ca2؉ /calmodulin-dependent protein phosphatase that is abundantly expressed in several specific areas of the brain, which are exceptionally vulnerable to stroke, epilepsy, and neurodegenerative diseases. In this study, we assessed the effects of high level activity of calcineurin on neuronal cells. Virus-mediated high level constitutive activity of calcineurin rendered neuronal cells susceptible to apoptosis induced by serum reduction or by a brief exposure to calcium ionophore. Adenovirus-mediated, high level forced activity of calcineurin induced cytochrome c/caspase-3-dependent apoptosis in neurons. Preincubation with the calcineurin inhibitors cyclosporin A and FK506 reduced susceptibility to apoptosis. High level constitutive expression of Bcl-2 or CrmA or incubation with a specific caspase-3 inhibitor inhibited the calcineurin-induced apoptosis. These data indicate that high level constitutive activity of calcineurin predisposes neuronal cells to cytochrome c/caspase-3 dependent apoptosis even under sublethal conditions.

Various therapeutic approaches toward killing glioma cells by inducing apoptosis have been developed, but these approaches are often hampered by anti-apoptotic mechanisms. In this study, we attempted to develop a technique that overrides the resistance toward apoptosis in glioma cells. To date, p53-and Fas-mediated apoptotic pathways have been shown to be different. Therefore, we carried out a gene therapy that combines the pro-apoptotic effect of these two different pathways. The recombinant adenoviruses (Advs) for p53 and Fas ligand (FL) (Adv-p53 and Adv-FL, respectively) were constructed. Transfecting the p53 gene into glioma cell lines (A-172 and U251 glioma cells) led to overexpression of Bax, a protein that induces permeability transition; at the same time, this transfection brought about an overexpression of Fas. To intensify Fas-mediated apoptosis, we transferred the FL gene together Regardless of whether a cell line is resistant or sensitive to FL-and p53-mediated apoptosis, coinfection with Adv-p53 and Adv-FL dramatically enhanced the degree of apoptosis of glioma cells. Our results indicate that the coinfection approach can be used as a modality for the gene therapy of gliomas, overriding the apoptosis-resistant mechanisms in glioma cells. Cancer Gene Therapy (2000) 7, 732-738

The expression of connexin43, the primary gap-junction constituent of glial cells, was evaluated at the messenger RNA and protein levels in different grades of astrocytoma to investigate the relevance of gap junctions in herpes simplex virus-thymidine kinase (HSV-tk)-mediated gene therapy of brain tumors. Transduction of the retroviral-mediated HSV-tk gene into tumor cells with subsequent administration of ganciclovir has recently been used as an experimental therapeutic strategy for treatment of brain tumors. One aspect of this approach is the bystander effect, which augments the efficacy of this therapeutic approach. Glioblastoma cells with minimum levels of connexin43 protein were transfected with a connexin43 complementary DNA. These cells manifested a marked increase in the in vitro bystander effect, supporting the contention that the in vitro bystander effect is a consequence of metabolic cooperation between cells mediated by gap junctions. To assess relative levels of gap-junction protein expression in the relevant tumor type, we examined primary astrocytomas, primary astrocytoma cell cultures, and glioblastoma cell lines. Although most astrocytoma tumor samples expressed connexin43, they differed in the level of expression, with the greatest variation exhibited in high-grade astrocytomas. Primary glioblastoma cell cultures and established glioblastoma cell lines also displayed some variability in connexin43 levels. In aggregate, our results anticipate that glioblastomas will have a varied bystander effect during HSV-tk gene therapy depending on the level of connexin43 expression.

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ObjectiveThis single-arm, open-label, Phase II study evaluated the efficacy and safety of single-agent bevacizumab, a monoclonal antibody against vascular endothelial growth factor, in Japanese patients with recurrent malignant glioma.MethodsPatients with histologically confirmed, measurable glioblastoma or World Health Organization Grade III glioma, previously treated with temozolomide plus radiotherapy, received 10 mg/kg bevacizumab intravenous infusion every 2 weeks. The primary endpoint was 6-month progression-free survival in the patients with recurrent glioblastoma.ResultsOf the 31 patients enrolled, 29 (93.5%) had glioblastoma and 2 (6.5%) had Grade III glioma. Eleven (35.5%) patients were receiving corticosteroids at baseline; 17 (54.8%) and 14 (45.2%) patients had experienced one or two relapses, respectively. The 6-month progression-free survival rate in the 29 patients with recurrent glioblastoma was 33.9% (90% confidence interval, 19.2–48.5) and the median progression-free survival was 3.3 months. The 1-year survival rate was 34.5% with a median overall survival of 10.5 months. There were eight responders (all partial responses) giving an objective response rate of 27.6%. The disease control rate was 79.3%. Eight of the 11 patients taking corticosteroids at baseline reduced their dose or discontinued corticosteroids during the study. Bevacizumab was well-tolerated and Grade ≥3 adverse events of special interest to bevacizumab were as follows: hypertension [3 (9.7%) patients], congestive heart failure [1 (3.2%) patient] and venous thromboembolism [1 (3.2%) patient]. One asymptomatic Grade 1 cerebral hemorrhage was observed, which resolved without treatment.ConclusionSingle-agent bevacizumab provides clinical benefit for Japanese patients with recurrent glioblastoma.