Effect of a src inhibitory peptide based on connexin43 on neural stem cells with glioma-driver mutations

Abstract Glioblastomas are one of the most malignant tumors. Glioma Stem Cells (GSCs) are a subpopulation of cells resistant to standard treatments, responsible for tumor recurrence. Strong evidence supports that Neural Stem Cells (NSCs) from the subventricular zone (SVZ) are the origin of GSCs. This transition frequently concurs with epidermal growth factor receptor (EGFR) overexpression or mutations, such as EGFRvIII. Our group designed a cell penetrating peptide based on connexin43 (TAT-Cx43266-283) that inhibits the oncoprotein c-Src and therefore targets GSCs, increasing survival in glioma-bearing mice. Because c-Src and EGFR signaling are closely related, we explored the effect of TAT-Cx43266-283 in the transition of NSCs to GSCs. We compared the effect of TAT-Cx43266-283, control peptides, temozolomide and erlotinib, a common EGFR inhibitor, in SVZ NSCs (Control-NSCs) and murine NSC and patient-derived GSCs with key glioma-driver mutations in Nf1, PTEN and EGFR. EGFR signaling pathway was analyzed by Western blot. Furthermore, we are analyzing the effect of TAT-Cx43266-283 in a mouse model where tumors originate from SVZ NSCs with glioma-driver mutations. Our results showed a strong effect of TAT-Cx43266-283 in cell viability of NSCs and patient-derived GSCs with EGFR amplification or active EGFRvIII, without significant effects in Control-NSCs. Importantly, we found a lower effect of temozolomide, erlotinib, and other control peptides in these cells. Western blot analyses suggest that TAT-Cx43266-283 decreases EGFR, EGFRvIII and c-Src activity. Preliminary in vivo results suggest that TAT-Cx43266-283 decreases tumor size and enhances survival in mice bearing gliomas initiated by altered NSCs. So far, our results show that TAT-Cx43266-283 impairs EGFR signaling pathway with the subsequent reduction in the proliferation and survival of NSCs or GSCs with EGFR alterations. These results stress the relevance of TAT-Cx43266-283 as a future therapy against glioblastoma, alone or in combination with other treatments.