Modulation of exosome biogenesis and PD-L1 cargo sorting by ionizing radiation

• Grant number: 25/03546-1
• Support Opportunities: Scholarships in Brazil - Doctorate
• Start date: September 01, 2025
• End date: May 31, 2028
• Field of knowledge: Biological Sciences - Morphology - Cytology and Cell Biology
• Principal Investigator: Wanessa Fernanda Altei
• Grantee: Júlia Oliveira Dias
• Host Institution: Hospital do Câncer de Barretos. Fundação Pio XII (FP). Barretos , SP, Brazil

Abstract

Head and neck cancer (HNC) remains a cancer type with high failure rates, in which radiotherapy (RT) is a key treatment modality. Recent advances in RT techniques, including extreme hypofractionation, have improved tumor control and clinical outcomes. These techniques are thought to induce immunogenic cell death, modulating the immune microenvironment and enhancing responses to immunotherapy. However, combining RT with immunotherapy has yielded inconsistent clinical results, and fundamental radiobiological mechanisms remain unclear. Extracellular vesicles (EVs), particularly small EVs (sEVs), which encompass exosomes, play a crucial role in intercellular communication within the tumor microenvironment, affecting tumor progression and treatment response. Besides that, exosomes play well-established roles in cancer development, metabolism, and radioresistance. Notably, sEVs can carry programmed death-ligand 1 (EV-PD-L1), an immunosuppressive molecule involved in immune evasion. Previous studies indicate that RT increases sEV secretion in HNC cells, yet the specific subtypes of sEVs involved, their underlying biogenesis mechanisms and signaling pathways remain largely unexplored, which complicates the development of target therapies. This study aims to characterize radiation-induced sEVs in HNC cell lines in vitro and determine radiation effects in exosome biogenesis specifically, comparing conventional (2 Gy) and extreme fractionation (8 Gy) doses. We will utilize a live exosome reporter system to track exosome biogenesis and secretion following RT and evaluate colocalization of PD-L1 with exosomal markers to determine whether RT-induced EV-PD-L1 secretion originates from the endosomal pathway. With this, we will also investigate the potential of EV inhibitors to modulate EV-PD-L1 secretion. This project presents an innovative approach by integrating advanced fluorescence-based exosome tracking tools and precise characterization of sEVs. By bridging gaps in radiobiology and immunotherapy, this study will potentially contribute to the development of preclinical studies for improving HNC treatment outcomes. (AU)