The Botanical Drug PBI-05204, a Supercritical CO2 Extract of Nerium Oleander, Inhibits Growth of Human Glioblastoma, Reduces Akt/mTOR Activities, and Modulates GSC Cell-Renewal Properties.

Alessandro Colapietro,Tara L Conway,Claudio Festuccia,Flora Vitale,Giovanni Luca Gravina,Alessandra Rossetti,Assunta Leda Biordi,Daoyan Wei,Peiying Yang,Stefano Martellucci,Robert A Newman,Francesco Marampon,Sharmistha Chakraborty,Andrea Mancini,Vincenzo Mattei

doi:10.3389/fphar.2020.552428

Abstract

Glioblastoma multiform (GBM) is the most common primary glial tumor resulting in very low patient survival despite current extensive therapeutic efforts. Emerging evidence suggests that more effective treatments are required to overcome tumor heterogeneity, drug resistance and a complex tumor-supporting microenvironment. PBI-05204 is a specifically formulated botanical drug consisting of a modified supercritical C02 extract of Nerium oleander that has undergone both phase I and phase II clinical trials in the United States for treatment of patients with a variety of advanced cancers. The present study was designed to investigate the antitumor efficacy of this botanical drug against glioblastoma using both in vitro and in vivo cancer models as well as exploring efficacy against glioblastoma stem cells. All three human GBM cell lines, U87MG, U251, and T98G, were inhibited by PBI-05204 in a concentration dependent manner that was characterized by induction of apoptosis as evidenced by increased ANNEXIN V staining and caspase activities. The expression of proteins associated with both Akt and mTOR pathway was suppressed by PBI-05240 in all treated human GBM cell lines. PBI-05204 significantly suppressed U87 spheroid formation and the expression of important stem cell markers such as SOX2, CD44, and CXCR4. Oral administration of PBI-05204 resulted in a dose-dependent inhibition of U87MG, U251, and T98G xenograft growth. Additionally, PBI-05204–treated mice carrying U87-Luc cells as an orthotropic model exhibited significantly delayed onset of tumor proliferation and significantly increased overall survival. Immunohistochemical staining of xenograft derived tumor sections revealed dose-dependent declines in expression of Ki67 and CD31 positive stained cells but increased TUNEL staining. PBI-05204 represents a novel therapeutic botanical drug approach for treatment of glioblastoma as demonstrated by significant responses with in vivo tumor models. Both in vitro cell culture and immunohistochemical studies of tumor tissue suggest drug induction of tumor cell apoptosis and inhibition of PI3k/mTOR pathways as well as cancer stemness. Given the fact that PBI-05204 has already been examined in phase I and II clinical trials for cancer patients, its efficacy when combined with standard of care chemotherapy and radiotherapy should be explored in future clinical trials of this difficult to treat brain cancer.

Highlights

Glioblastoma multiform (GBM; WHO grade IV) is a commonly diagnosed primary glial tumor, characterized by a higher percentage of treatment failures and poor prognosis even with aggressive surgical and chemo-radio therapies (Preusser et al, 2011; Seystahl et al, 2016; Batash et al, 2017)
Morphologic changes were associated with a concentration-dependent increase in drug mediated apoptosis as evidenced by PI and Annexin V staining via flow cytometry and increased caspase activities
While surgery is the primary form of treatment it is seldom curative when used as a single treatment modality due to the fact that malignant cells invade healthy brain tissue at a microscopic level, not allowing a microscopically complete resection

Summary

Introduction

Glioblastoma multiform (GBM; WHO grade IV) is a commonly diagnosed primary glial tumor, characterized by a higher percentage of treatment failures and poor prognosis even with aggressive surgical and chemo-radio therapies (Preusser et al, 2011; Seystahl et al, 2016; Batash et al, 2017). The diagnosis of GBM often occurs after patients become symptomatic, after which the disease is already extensively spread within brain tissue (Batash et al, 2017). Treatment options for GBM patients are limited. Lack of neurosurgical removal of tumor is a major cause for poor prognosis for adult patient with GBM with a 5-year survival rate of less than 5% (D’Alessio et al, 2019). Development of novel therapeutic modalities is necessary to improve the survival of patients with GBM

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