Association between expression of GALR2/Galanin and chemokine/chemokine receptors and leukocyte infiltration in head and neck squamous cell carcinoma

Abstract

Leukocyte infiltration in head and neck squamous cell carcinoma (HNSCC) is associated with prognosis and response to treatment. This association is complex and may be positive (i.e., improved prognosis and response to treatment) or negative (i.e., worse prognosis and poor response to treatment) depending on the intensity of the immune cell infiltrate, of its composition and phenotype.The project associated with the present proposal (process #2020/00394-2) explores the independent and inter-related influences of two biological mechanisms/processes, namely expression of GALR2/Galanin and efferocytosis activity, on HNSCC progression and aggressiveness mediated by modulation of the immune response. The effector anti-tumoral response depends on the physical/spatial proximity between immune and neoplastic cells, and the infiltration of lymphocytes in the tumor microenvironment is contingent on its 'education' (imprinting process) in secondary lymphoid organs for their subsequent targeting to the specific/tumor sites via efferent lymphatic system and peripheral vascularization. After extravasation and entrance into perivascular tissues in the tumor site, further migration and activation of lymphocytes and innate immune (myeloid) cells is driven by molecules in the tumor microenvironment such as secreted products (cytokines, chemokines, growth factors) and components of the extracellular matrix.This proposal intends to investigate the association between gene expression of GALR2/Galanin and selected chemokines and chemokine receptors with overall leukocyte infiltration (associated with better prognosis and response to treatment) and with the presence of macrophages and regulatory T cells (associated with worse prognosis and poor response to treatment) in the HNSCC tumor microenvironment.Samples of HNSCC patients collected with the necessary ethical approval for the process 2020/00394-2 will be used. Expression of the selected genes (GALR2 and its ligand Galanin; CCR2 and its ligand CCL2; CCR5 and its ligands CCL4 and CCL5; CCR4 and its ligands CCL17 and CCL22; CCR6 and its ligand CCL20) will be determined by RT-qPCR. Leukocyte infiltration and the presence of macrophages and regulatory T cells will be determined by immunohistochemistry for CD45, CD68 and FOXP3, respectively. Data obtained will complement the investigation of the influence of GALR2/Galanin axis on the modulation of leukocyte infiltration in HNSCC and may yield insights on a possible crosstalk between GALR2/Galanin and the expression of chemokine / chemokine receptors influencing migration of monocyte/macrophages and regulatory T cells in HNSCC.