carcinoma epidermoide de cabeça e pescoço; microambiente imune tumoral; imunossupressão; PD-L1; biópsia líquida; biomarcador.
Name: CAMILA BATISTA DANIEL
Publication date: 16/04/2024
Examining board:
Name |
Role |
|---|---|
| SANDRA LUCIA VENTORIN VON ZEIDLER | Advisor |
Summary: Immunosuppression is recognized as a hallmark of cancer and has been associated with worse outcomes. In head and neck squamous cell carcinoma (HNSCC), immunosuppression is a hallmark of the tumour and may be mediated by immunosuppressive inflammatory cells and PD-L1 expression. Given their participation in this process, our study aimed to describe the prognostic impact of these elements in tumour tissue and peripheral blood HNSCC patients. We conducted a multicentre retrospective study with biological samples and clinical data from HNSCC patients recruited at two centres in Brazil and the United Kingdom and healthy individuals. To analyse the inflammatory infiltrate, we used tumour tissue slides stained with haematoxylin and eosin and immunohistochemistry for PD-L1 analysis and neutrophil quantification. Absolute leukocyte counts were retrieved from pretreatment blood counts available in medical records. To evaluate the prognostic value of PD-L1 in liquid biopsy, we used serum and plasma samples obtained from patients and healthy individuals for quantification of soluble PD-L1 (sPD-L1) by ELISA. Fresh tumour tissue samples were used to analyse CD274 gene expression levels using the RT-qPCR technique. Furthermore, we analysed PD-L1 expression by flow cytometry in HNSCC cell lines and quantified sPD-L1 levels in the supernatant. The tumour microenvironment analysis showed that low levels of lymphocytes are associated with worse overall survival and disease-free survival. However, we did not observe this relationship with tumour-associated neutrophils and tumour PD-L1. When analysed together in a scoring system, we demonstrated that low levels of lymphocytes, high expression of PD-L1 and high infiltration of neutrophils are associated with a worse outcome. In blood, a high ratio of neutrophils and lymphocytes (NLR) was also associated with worse survival but was not correlated with inflammatory components of the tumour. High levels of sPD-L1 protein were associated with reduced overall survival, however our study did not identify a relationship between sPD-L1 levels in the blood and PD-L1 expression in tumour tissue, determined by immunohistochemistry and RT-qPCR. In contrast, the in vitro study showed that the levels of sPD-L1 released into the supernatant are strongly correlated with cytoplasmic and membrane expression. Our data further showed that sPD-L1 levels in patients were positively correlated with the number of leukocytes, neutrophils and monocytes in peripheral blood. Taken together, our results highlight the prognostic potential of markers of the tumour microenvironment analysed in a combined manner, in a scoring system, as a way of providing a more comprehensive overview of tumour behaviour, highlighting important events, such as immunosuppression. Our results highlight the prognostic potential of PD-L1 detected by liquid biopsy in HNSCC and indicate that the levels detected in the blood do not necessarily correspond to what is observed in the tumour. Therefore, it is believed that it should be analysed as an independent marker whose immunosuppressive role is carried out at a systemic level.
