Glioblastoma-specific anti-TUFM nanobody for in-vitro immunoimaging and cancer stem cell targeting

// Neja Samec 1 , Ivana Jovcevska 1 , Jure Stojan 1 , Alja Zottel 1 , Mirjana Liovic 1 , Michael P. Myers 2 , Serge Muyldermans 3 , Jernej Sribar 4 , Igor Križaj 4 and Radovan Komel 1 1 Medical Centre for Molecular Biology, Institute of Biochemistry, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia 2 International Centre for Genetic Engineering and Biotechnology (ICGEB), Trieste, Italy 3 Cellular and Molecular Immunology, Bioengineering Sciences Department, Vrije Universiteit Brussel, Brussels, Belgium 4 Department of Molecular and Biomedical Sciences, Jožef Stefan Institute, Ljubljana, Slovenia Correspondence to: Radovan Komel, email: radovan.komel@mf.uni-lj.si Neja Samec, email: neja.samec@mf.uni-lj.si Keywords: glioblastoma multiforme; biomarkers; nanobodies; cytotoxicity; TUFM Received: October 20, 2017      Accepted: February 24, 2018      Published: April 03, 2018 ABSTRACT Glioblastoma multiforme (GBM) is the most common and lethal form of brain tumor. The prognosis for patients remains poor, despite the combination of new preoperative and intraoperative neuroimaging, radical surgery, and recent advances in radiotherapy and chemotherapy. To improve GBM therapy and patient outcome, sustained drug delivery to glioma cells is needed, while minimizing toxicity to adjacent neurons and glia cells. This might be achieved through an anti-proteomic approach based on nanobodies, the single-domain antigen-binding fragments of heavy-chain antibodies of the camelid adaptive immune system. We report here on the validation and quantification of a nanobody raised against mitochondrial translation elongation factor (TUFM). Differential expression of TUFM was examined in different GBM cell lines and GBM tissue at the protein and mRNA levels, as compared to their expression in neural stem cells and normal brain tissue. We further used in-silico modelling and immunocytochemistry to define the specificity of anti-TUFM nanobody (Nb206) towards GBM stem cells, as compared to GBM cell lines (U251MG and U87MG cells). Due to its specificity and pronounced inhibitory effect on GBM stem cell growth, we propose the use of this anti-TUFM nanobody for GBM in vitro immunoimaging and potentially also cancer stem cell targeting.