Efferocytosis in the microenvironment of Oral Squamous Cell Carcinoma: impact on immune response and tumor progression and dissemination

• Grant number: 22/06041-0
• Support Opportunities: Scholarships in Brazil - Post-Doctorate
• Effective date (Start): July 01, 2022
• Effective date (End): June 30, 2024
• Field of knowledge: Health Sciences - Dentistry
• Principal Investigator: Carlos Rossa Junior
• Grantee: Ianny Brum Reis
• Host Institution: Faculdade de Odontologia (FOAr). Universidade Estadual Paulista (UNESP). Campus de Araraquara. Araraquara , SP, Brazil
• Associated research grant: 20/00394-2 - Head and neck squamous cell carcinoma (HNSCC) invasion and distant metastasis: relevance and crosstalk between GALR2 and efferocytosis in the tumor microenvironment and hematogenic dissemination, AP.TEM

Abstract

Cell death is a frequent event in the microenvironment (TME) of Oral Squamous Cell Carcinoma (OSCC). Multiple cell types die in the TME, including neoplasic, stromal (fibroblasts, endothelial cells), adjacent non-neplasic epithelial cells and immune cells (neutrophils, macrophages, lymphocytes) within the tumor mass and in the surrounding stroma. Cell death may be the consequence/result of the primary cytotoxic therapy (chemo/radiotherapy) or it may occur as a natural process in the TME due to hypoxia, lack of nutrients, accumulation of cytotoxic by-products of cell metabolism. Diverse types of cell death may occur in the TME, including apoptosis, necrosis and pyroptosis. Apoptosis is considered immunologically silent, in contrast to necrosis and pyroptosis in which the cytosolic content is released, including cytokines, and other biologically-active molecules, such as ATP and PRR-activating damage-associated molecular patterns. Phagocytosing immune cells, particularly macrophages, are engaged in the process of removal of apoptotic cells, in a physiological process called efferocytosis. Effecytosis has reciprocal and dynamic influences with the immune response: phenotype of phagocytosing cells affects efficiency of efferocytosis, and he efferocytosis process also influences the phenotype of he phagocytes. Thus even the silent process of cell death by apoptosis may affect immune response, which may be important in the context of TME and tumor immunology. Cell death (occurring naturally or as a consequence of cytotoxic therapies) may have immunomodulatory (stimulant/suppressive) effects in the TME of OSCC, which may influence tumor progression (invasion/metastasis) and/or the response to (cytotoxic or immunomodulatory) therapeutic approaches, promoting treatment resistance or recurrence. The aim of the proposed studies is to assess how inhibition of efferocytosis in the ME affects the phenotype of immune cells, both in vitro and in vivo. We intend to use two experimental strategies to inhibit efferocytosis: I) a blocking antibody for phosphatidylserine (Bavituximab, Creative Biolabs), neutralizing the major eat me signal in apoptotic cells and II) a specific inhibitor of Rac1 GTPase (NSC23766, Tocris Bioscience), which is the master switch in effeocytosis. The central hypothesis is that inhibiting efferocytosis will affect tumor progression, metastasis and hematogenic dissemination by immunomodulatory influences in the TME. We propose in vitro experiments using tridimensional heterospheroid cultures and two in vivo pre-clinical models (chick chorioallantoic membrane-CAM and heterotopic xenograft models in nude mice) to investigate the influence of efferocytosis on tumor invasion and progression, verifying the correlation between these outcomes and the phenotype of innate immune cells. OSCC patient-derived samples will be used in association studies, looking into correlations between expression of efferocytosis markers, prevalence of different types of cell death and the phenotype of immune-infiltrating cells. (AU)