Abstract 3575: Angiotensin-(1-7) and temozolomide provide combinatorial inhibition of glioblastoma cell growth
Authors: Calipari Erin S. , Tallant E Ann , Lesser Glenn , Debinski Waldemar , Gallagher Patricia E. 
Published: February 2011

Glioblastoma multiforme (GBM), an anaplastic, highly cellular, poorly differentiated tumor, is the predominant malignant brain tumor diagnosed in adults. Standard treatment for glioblastoma consists of surgical resection and radiation with the possible addition of chemotherapy. For example, temozolomide, an orally active imidazotetrazinone pro-drug that exerts its anti-neoplastic effect by interfering with DNA replication, proved to be efficacious in patients with glioblastoma. Even with aggressive therapy, the average survival rate for most patients is less than one year. This poor prognosis suggests a need for novel approaches for the treatment of glioblastoma. Angiotensin-(1-7) [Ang-(1-7)], an endogenous, seven amino acid peptide targeting the mas receptor, significantly reduced the serum-stimulated growth of human G48a glioblastoma cells isolated from a primary, high-grade astrocytoma. Incubation of the glioblastoma cells for 4 days with 100 nM Ang-(1-7) or 10 μM temozolomide caused a greater than 40% reduction in cell growth. More importantly, an additive inhibition (72.0% decrease) of glioblastoma cell growth was obtained by co-incubation of Ang-(1-7) and temozolomide. The combinatorial effect of the two drugs suggests differing mechanisms of action. Treatment of human G48a cells with 100 nM Ang-(1-7) reduced phosphorylation of the mitogen-activated protein kinases, extracellular signal-regulated kinase (ERK)1 and ERK2, by 66.8% and 45.5% (n = 3), respectively, indicating that the anti-proliferative effects may occur, at least in part, through inhibition of the ERK signal transduction pathway. The decrease in ERK activation was associated with a 4.8 ± 1.3-fold increase in the dual-specificity phosphatase DUSP1/MKP-1 (n = 4; p&lt;0.05). This suggests that the heptapeptide regulates DUSP1 to reduce ERK1/ERK2 auto-phosphorylation and activation and inhibit glioblastoma cell growth. Ang-(1-7) treatment also caused a time-dependent decrease in both vascular endothelial growth factor (VEGF) and placental growth factor (PlGF) mRNAs with maximal attenuation at 8 and 16 h, respectively (VEGF - 1.0 ± 0.1 vs. 0.58 ± 0.14; p&lt;0.05; n=5; PlGF - 1.0 ± 0.1 vs. 0.62 ± 0.12; p&lt;0.05; n=5). This reduction correlates with results from our recently completed Phase I clinical trial demonstrating a decrease in plasma PlGF in four patients who exhibited stable disease for greater than 3 months following treatment with Ang-(1-7). Taken together, these data suggest that Ang-(1-7) may serve as a first-in-class, targeted, anti-angiogenic chemotherapeutic agent for glioblastoma. Since Ang-(1-7) exerts its anti-proliferative effects through activation of the G protein-coupled receptor mas, representing a unique mechanism of action distinct from other cell growth modulators, the heptapeptide could be administered singly or with other chemotherapeutic agents to provide synergistic effects.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3575.