Neutrophils in Cancer: Phenotypic Heterogeneity Across Tumor Models and Significant Alteration of Splenic Neutrophil Phenotype in Lymphosarcoma RLS40 Model Following DNase I Treatment

<b>Background/Objectives</b>: Neutrophils have recently gained significant attention due to their heterogeneity in tumor settings. Recent data showed neutrophil pro- and anti-tumor profiles during tumor progression. However, the concessive causes of neutrophil skewing toward one or another profile are not fully understood. <b>Methods</b>: In this study, using RT-qPCR, flowcytometry, and confocal microscopy, we investigated the phenotype of splenic neutrophils of mice bearing Lewis lung carcinoma LLC, RLS₄₀ lymphosarcoma, and B16 melanoma. <b>Results</b>: Our data showed an immunosuppressive phenotype in the case of the LLC model with PD-L1 and IL10 expression. In the B16 model, minimal changes in the neutrophil phenotype were observed, regardless of tumor size. In the RLS₄₀ model, the neutrophil phenotype was associated with the tumor growth rate, where, in aggressively progressed tumors (RLS₄₀^High), CCL17 was expressed, while, in mice with controlled tumor growth (RLS₄₀^Low), anti-tumor markers were expressed (FAS, ICAM-1, PD-L1). DNase I treatment significantly reduced tumor growth and metastasis in the RLS₄₀ model but not in B16, enhanced the anti-tumor profile in RLS₄₀ neutrophils, and tended to reduce NET formation induced by A23187. <b>Conclusions</b>: The phenotype of neutrophils from tumor-bearing mice is influenced by the tumor type and progression stage. DNase I had anti-tumor, antimetastatic, and immunostimulatory effects and significantly modified the neutrophil profile in the immunogenic model RLS₄₀.