An innovative therapeutic strategy to treat Gliomas

Gliomas represent about 80% of all malignant brain tumours and the heterogeneity of their composition makes finding effective therapies very challenging. The most aggressive form of gliomas is represented by Glioblastoma Multiforme (GB). The therapeutic strategy currently used to treat GB consists in surgical resection of the tumour mass followed by cycles of radio- and chemotherapy. Unfortunately, this standard-of-care does not selectively act on glioma cells, resulting only partly effective; indeed, the overall survival of GB patients is of almost 15 months after diagnosis. Thus, there is a compelling need to find novel approaches that counteract glioma growth. In the latest years, our lab has studied the antineoplastic effects of a bacterial protein toxin CNF1 (Cytotoxic Necrotizing Factor 1) on gliomas (Vannini et al., 2014; Vannini et al., 2016; Vannini et al., 2017). Briefly, our data pointed out that the intracerebral delivery of CNF1 i) leads to multinucleation, senescence and eventually death of glioma cells and ii) preserves neuronal function in peritumoral areas. Despite all these promising results, CNF1 is neither able to selectively acts on glioma cells nor to cross the blood-brain barrier (BBB). For this last reason, CNF1 needs to be intracerebrally administrated following a very invasive protocol. Recent studies have demonstrated that Chlorotoxin (CTX; a 36 aminoacid peptide derived from the venom of the scorpion Leiurus quinquestriatus) is able to penetrate the BBB and, more interestingly, to selectively recognize and target glioma cells (Lyons et al., 2002; Dardevet et el, 2015). As a matter of fact, CTX is already employed in clinics as a drug vector and/or as a marker of tumour cells during the surgical resection of gliomas (Cohen et al., 2018; M. Veiseh et al., 2007). Importantly, it has been proved that CTX also shows minimal cross-reactivity with brain non-malignant cells (Lyons et al., 2002). Thus, in order to overcome CNF1 limitations, we developed a chimeric protein fusing CTX with CNF1 (i.e. CTX-CNF1). Thanks to in vitro studies, we show that CTX-CNF1 is effective in leading glioma cells to death through the activation of a senescence process and that a systemic administration of CTX-CNF1 is able to target glioma cells with high selectivity, provoking a significant increase in the survival rate of glioma-bearing animals