Abstract 1278: Tertiary lymphoid structure formation in patient-derived xenograft (PDX) of head and neck paraganglioma: A novel xenogeneic model

Abstract Head and neck paragangliomas (HNPGL) are a rare type of neuroendocrine tumor that, although typically slow-growing, can become invasive and deadly. Treatment is primarily surgical, which can be highly invasive and, in some cases, not feasible. Alternative therapies, such as chemotherapy and targeted radiotherapy, have demonstrated limited efficacy. This study aims to address the critical need for suitable in vivo HNPGL models to advance translational research by establishing murine models of immunodeficient NOD.Cg-Prkdcscid Il2rgtm1Wjl/SzJ (NSG) mice engrafted with patient-derived tumor xenografts (PDXs). Interestingly, although HNPGL is not typically classified as a lymphocyte-dominant tumor due to the reduced presence of immune cells in its microenvironment, two consecutive generations of NSG mice engrafted with PDXs derived from a single aggressive HNPGL case in an adolescent patient, exhibited varying degrees of xenogeneic graft-versus-host disease (GVHD). This suggests the co-existence of the patient's tumor-infiltrating lymphocytes (TILs) within the PDXs. In the first generation, 34 days after PDXs implantation, mice exhibited clinical signs of GVHD, including weight loss, severe kyphosis, lethargy, piloerection, and fur loss. Ex vivo analysis revealed extensive lymphoid infiltration in multiple organs, including the spleen, lung, liver, and kidney. Immunohistochemical staining confirmed the presence of predominantly human T cell (CD3+) infiltrates, with a minor human B cell (CD20+) component, in both xenografts and the primary tumor. Notably, surgical resection and reimplantation of primary PDX into secondary NSG mice significantly promoted human B-cell expansion and the formation of a well-defined peritumoral tertiary lymphoid structure (TLS). Mice bearing these xenografts exhibited reduced GVHD, and a TLS with a histological organization resembling secondary lymphoid organs at 89 days. This TLS was characterized by a central core of hCD20+ B cells surrounded by a peripheral mantle of hCD3+ T cells, suggesting the formation of a mature TLS with a germinal center that may harbor reactive B cells. Our findings suggest that TLS formation in PDX model may facilitate tumor-specific antibody production and antigen presentation.These insights provide a foundation for leveraging PDX models with TLS as innovative tool for studying HNPGL microenvironment and asses immune signatures that could be used for the development of novel immunotherapeutic strategies. Citation Format: Sara Pagotto, Simone De Fabritiis, Carola Di Camillo, Francesco Del Pizzo, Silvia Perconti, Diana Liberata Esposito, Mario Sanna, Pasquale Simeone, Paola Lanuti, Manuela Iezzi, Renato Mariani-Costantini, Fabio Verginelli, Rosa Visone. Tertiary lymphoid structure formation in patient-derived xenograft (PDX) of head and neck paraganglioma: A novel xenogeneic model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 1278.