Biochemical and Biophysical Research Communications
Monensin inhibits glioblastoma angiogenesis via targeting multiple growth factor receptor signaling
Introduction
Although recent advances in multimodal therapies combing surgery, chemo-radiotherapy and targeted therapies, glioblastoma is still the most common primary malignant brain tumour in adults with median overall survival ranging from 15 to 21 months [1]. The resistance to standard therapies are complex, including activation of alternative signalling pathways, the vast vascularization and molecular heterogeneity, the stem cell-like characteristics, the influence of the blood-brain barrier and the expression level of o6-methylguanine-DNA methyltransferase [2]. Glioblastoma is highly angiogenic and angiogenic inhibitors, such as bevacizumab, have been actively under clinical trials for the treatment of recurrent glioblastoma [3]. Angiogenesis growth factors and their receptors, such as vascular endothelial growth factor (VEGF)/VEGFR and epidermal growth factor (EGF)/EGFR are highly expressed in tumor associated-endothelial cells and play essential roles in mediating tumor angiogenesis [4]. Targeting both glioblastoma cells and angiogenesis may present an effective therapeutic strategy for glioblastoma.
Monensin is an ionophore antibiotic isolated from Streptomyces cinnamonensis with antibacterial and antiparasitic potential [5]. Monensin is recently recognized as anti-cancer drug candidate. Substantial preclinical evidence demonstrates that monensin inhibits the growth of many cancers, such as renal cell carcinoma, prostate cancer, pancreatic cancer and head and neck cancer [6]. Monensin also acts synergistically with tyrosine kinase inhibitors and chemotherapeutic agents in cancer [7,8]. It is effective in targeting chemoresistant pancreatic cancer cells [9] and kills human cancer stem cells [10]. In addition, studies highlight the selective anti-tumor activity of monensin by showing that monensin is not toxic to normal cells [10,11]. Monensin inhibits the signalling pathways that are critical to cancer growth and survival, including NF-γB, STAT and EGFR [6]. In this work, we investigated the effects of monensin in glioblastoma angiogenesis using primary endothelia cells isolated from human glioblastoma tissues. Using in vitro and in vivo angiogenesis models, we demonstrate that monensin potently inhibits glioblastoma angiogenesis. In addition, glioblastoma endothelial cells are more sensitive to monensin compared to glioblastoma tumor cells. Finally, we demonstrate that monensin acts on endothelial cells through suppressing multiple growth factor receptor-mediated signaling pathways.
Section snippets
Primary endothelial cell (EC) isolation, cell culture and drugs
Human glioblastoma cell lines, U87, U251MG, T98G, A172, U251 N and U373 and HCC287 were obtained from the American Type Culture Collection. Cells were cultured in DMEM medium (Invitrogen) supplemented with 10% FBS and antibiotics (Life Technologies). Monensin (Cayman Chemical) was reconstituted in ethanol and used to treat cells at minimal 1: 1000 dilution. Recombinant human VEGF165 (R&D Systems) was reconstituted in water. Fresh glioblastoma tissues obtained during surgery from patients seen
Monensin at nanomolar concentration range inhibits glioblastoma angiogenesis via suppressing endothelial cell morphogenesis, migration, growth and survival
Angiogenesis is characterized by a number of cellular events including endothelial cell migration, adhesion and differentiation into tubular-structure. To investigate the effects of monensin in glioblastoma angiogenesis, we isolated and purified endothelial cells from fresh human glioblastoma tissues using the same protocol as previously described [12]. We next assayed in vitro endothelial tube formation using complete Matrigel matrix which are rich in extracellular matrix and endothelial cell
Discussion
Glioblastoma is characterized by an extensive microvascular proliferation and vascular permeability and thus angiogenesis inhibition in combination with standard therapy are hotly investigated in clinical trials for relapsed glioblastoma (eg, ClinicalTrials.gov Identifier: NCT01349660 and NCT01209442). Therapeutic manipulation of VEGF/VEGFR is the most studied clinical pathway in glioblastoma. Bevacizumab is a monoclonal antibody of VEGF and FDA-approved angiogenesis inhibitor for the treatment
Declaration of competing interest
All authors declare no conflict of interest.
Acknowledgement
This work was supported by Science and Technology Innovation seedling project of Sichuan (2016065).
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