Vol.:(0123456789) 1 3 Journal of Neuro-Oncology https://doi.org/10.1007/s11060-019-03252-6 LABORATORY INVESTIGATION G3BP1 knockdown sensitizes U87 glioblastoma cell line to Bortezomib by inhibiting stress granules assembly and potentializing apoptosis L. F. F. Bittencourt 1  · G. L. Negreiros‑Lima 2  · L. P. Sousa 2  · A. G. Silva 3  · I. B. S. Souza 3  · R. I. M. A. Ribeiro 3  · M. F. Dutra 1  · R. F. Silva 1  · A. C. F. Dias 1  · W. K. Martins 4  · L. S. Barcelos 1 Received: 2 May 2019 / Accepted: 25 July 2019 © Springer Science+Business Media, LLC, part of Springer Nature 2019 Abstract Introduction Glioblastoma multiforme (GBM) is the most lethal form of gliomas. New therapies are currently in development to tackle treatment limitations such as chemotherapy resistance. One mechanism of resistance may be the stress granules (SG) assembly, a stress-related cellular response that allows cells to recruit and protect mRNAs during stress. SG are composed of various proteins, being G3BP1 a core element that enucleates and results in SG assembly. Here, we aimed to evaluate the efects of inhibiting the G3PB1 expression in the chemotherapeutical-induced cell death of the U87 glioblastoma cell line. Materials and Methods G3BP1 mRNA and protein expression were modulated with short-interference RNA (siRNA). The viabil- ity of U87 cells after Bortezomib (BZM), a proteasome inhibitor, and Temozolomide (TMZ), an alkylating agent, was assessed by MTT assay. Apoptosis was evaluated by staining cells with Annexin-V/7-AAD and analyzing by fow cytometry. Caspase-3 activation was evaluated by immunoblotting. The chorioallantoic membrane in vivo assay was used to evaluate angiogenesis. Results When G3BP1 was knocked-down, the SG assembly was reduced and the BZM-treated cells, but not TMZ-treated cells, had a signifcant increase in the apoptotic response. Corroborating this data, we observed increased Caspase-3 activa- tion in the BZM-treated and G3BP1-knocked-down cells when compared to vehicle-treated and scramble-transfected cells. Worth mentioning, the conditioned culture medium of G3BP1-knocked-down BZM-treated cells inhibited angiogenesis when compared to controls. Conclusion Our data suggest G3BP1 knockdown diminishes SG formation and stimulates BZM-induced apoptosis of U87 cells in vitro, in addition to inhibiting glioblastoma-induced angiogenesis in vivo. Keywords Stress granules · G3BP1 · Glioblastoma multiforme · Bortezomib · Apoptosis · Angiogenesis Introduction Gliomas are the most common type of human primary brain tumors. The most lethal form is the glioblastoma multiforme (GBM), a class IV astrocyte-derived cancer which ranges in age-adjusted incidence rate from 0.59 to 3.69 per 100,000 per- sons depending on reporting country/organization [1]. Despite being relatively rare in comparison to breast or lung cancer, it is far more lethal. Survival rates in 5 years post-diagnosis are 5% with a survival median of 5–8 months [2]. New therapies, such as the small interfering RNA (siRNA), a common form of RNAi-based therapeutics, have been intensively investigated [3]. Silencing specifc genes associated with cancer chemo- therapy resistance and tumor progression can be potentially used as a novel antitumoral strategy in the near future [4, 5]. The stress granules (SG) have been studied for their role in cancer resistance to chemotherapy [6]. They are * L. S. Barcelos luciolasbarcelos@gmail.com 1 Departamento de Fisiologia E Biofísica, Instituto de Ciências Biológicas (ICB), Universidade Federal de Minas Gerais (UFMG), Av. Antônio Carlos, 6627 - Pampulha, Belo Horizonte, MG 31270-901, Brazil 2 Faculdade de Farmácia, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Grais, Brazil 3 Laboratório de Patologia Experimental, Universidade Federal de São João del-Rei (UFSJ), São João del-Rei, Minas Gerais, Brazil 4 Universidade Anhanguera de São Paulo, Pós-graduação Stricto-sensu e Pesquisa, São Paulo, Brazil