Thesis, FRANZEN Rachelle

Abstract

Kidney cancer is a common malignancy that affects approximately one in forty men during their lifetime. Although most cases are detected incidentally at an early stage, some patients are diagnosed only after the onset of symptoms, when the disease is already advanced and frequently metastatic to the lungs. Immunotherapies currently represent a standard treatment for clear cell renal cell carcinoma (ccRCC). However, despite their clinical efficacy, the immune mechanisms underlying anti-tumor responses remain incompletely understood. Among the immune cells potentially involved are eosinophils, whose prognostic value has been suggested in several oncological settings. The aim of this study was to investigate the role of eosinophils in pulmonary metastases of ccRCC using a transcriptomic approach. Forty-eight female BALB/c mice were divided into two experiments: the first compared control mice with mice depleted of eosinophils using Anti-IL5 treatment, while the second reproduced the same comparison in the context of Anti-PD1 immunotherapy. Bulk RNA sequencing was performed on metastatic lung tissues to identify differentially expressed genes, dysregulated biological signatures, and changes in immune cell composition through deconvolution analysis. Immunohistochemistry (IHC) and RT-qPCR analyses were subsequently performed to validate the transcriptomic findings. Because eosinophil depletion had previously been shown to reduce pulmonary metastatic burden, transcriptomic analyses were performed to investigate the biological mechanisms associated with this observation. The results showed that eosinophil depletion was associated with the dysregulation of 72 genes in the experiment without Anti-PD1 treatment, compared with only 11 genes in the presence of immunotherapy. No differentially expressed genes were shared between the two experiments. Functional analyses mainly highlighted signatures related to cellular stress responses, protein folding, and immune-related processes. Deconvolution analysis also suggested alterations in several immune cell populations, particularly natural killer (NK) cells, although no significant differences were detected for eosinophils. Finally, neither IHC nor RT-qPCR analyses were able to validate the RNA-seq findings. Overall, this study suggests that eosinophils may contribute to a subtle modulation of the pulmonary metastatic microenvironment in ccRCC. However, the observed effects were of low magnitude, and the validation approaches used were unable to confirm the transcriptomic results. Further investigations will therefore be required to better characterize the role of eosinophils in metastatic progression and in the response to immunotherapies.