Targeting Foxp3 in Glioblastoma: Blockade of Tumor Intrinsic Effects Boosts Response to Chemo-Radiotherapy

Abstract

Glioblastoma (GBM) is the most common malignant primary brain tumor in adults. Although this disease carries a dismal prognosis due to its highly invasive nature and resistance to therapy, no significant therapeutic advances have emerged in the last 20 years. The transcription factor Forkhead box protein P3 (FOXP3), known for its central role in the immunosuppressive activity of regulatory T cells (Tregs), has also been detected in tumor cells, including GBM cells. However, the intrinsic role of FOXP3 in GBM cells is poorly understood. Thus, we aimed to evaluate the effect of FOXP3 blockade in GBM. Meta-analysis of transcriptomic data indicated that FOXP3, which expression was higher in GBM biopsies than in normal brain, was associated with worse prognosis and chemo-resistance. It also correlated with the expression of markers of immune-suppression and epithelial-mesenchymal transition. Expression of FOXP3 in GBM cell lines and patient-derived cultures was upregulated by chemo- and radiotherapy, and its blockade using a cell penetrating peptide (P60) inhibited GBM cell migration, induced cytotoxicity and enhanced radio- and chemo-sensitivity. To improve the local availability of P60, we developed an adenoviral vector (Ad.P60) that enhanced the apoptotic response of GBM cells and reduced chemoresistance. Local treatment with Ad.P60 in mice bearing intracranial GBM inhibited tumor growth and improved chemosensitivity to cisplatin, leading to long-term survival with combined chemo-gene therapy. Our results suggest that FOXP3 exerts protumoral intrinsic effects in GBM cells and thus, it could emerge as a valuable target to improve the response of these tumors to standard treatment.

Note:
Funding declaration: This work was supported by Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET, Fellowships to A.J.N.C, J.A.P.A., M.P.K. and M.G.F.), Instituto Nacional del Cáncer (Asistencia Financiera a Proyectos de Investigación en Cáncer IV to M.C.); Agencia Nacional de Promoción Científica y Tecnológica (PICT-2018-3088, PICT-2019-00117 and PICT-2022-11-00074 to M.C; fellowship to A.J.N.C, M.P.K. and N.G); Fundación Florencio Fiorini (2023 Research grant to N.G. and 2023 Cancer Research Award to M.C) and Consejo Interuniversitario Nacional (fellowship to M.G.F.). The study was also supported by grants from: International Society for Neurochemistry (ISN-CAEN 2023 program, fellowship to M.G.F.), Ministerio de Ciencia, Innovación y Universidades and FEDER, UE (MICIU/AEI /10.13039/501100011033, PID2021- 128283OA-I00 and PID2022-137265OB-I00).

Conflict of Interests: The authors declare no competing interests within this study.

Ethical Approval: All procedures followed NIH guidelines and were approved by the Institutional Committee for the Care and Use of Laboratory Animals (CICUAL) at the University of Buenos Aires. The use of patient-derived glioma cell cultures for biomedical research was approved by the Research Ethics Committee “Comité de Ética en Investigaciones Biomédicas de la Fundación para la Lucha contra Enfermedades Neurológicas de la Infancia (FLENI)”.

Keywords: NEURO-ONCOLOGY, DIFFUSE GLIOMAS, GLIOBLASTOMA, FOXP3, CHEMO-RADIORESISTANCE, gene therapy