Patients with renal cell carcinoma (RCC) had increased immunosuppressive myeloid cells in their blood. The presence of a high number of myeloid-derived suppressor cells (MDSCs) in the blood was linked to immune suppression and cancer-related inflammation, which causes myeloid cells to migrate to tumour tissue. For a study, researchers sought to show that adding CD33+ CD11b+ MDSCs to the peripheral blood of a previously untreated RCC patient increased the number of monocytic CD33+CD11b+ MDSCs that also expressed PD-L1 and the membrane-bound enzyme hyaluronidase 2 (Hyal2). Because Hyal2+ myeloid cells might break down extracellular hyaluronan (HA), resulting in the buildup of pro-inflammatory HA fragments with low molecular weight, PD-L1 expression was related to immunological suppression, whereas Hyal2 expression was associated with inflammation. The data suggested that monocytic MDSCs might play a role in tumour-associated immune suppression and cancer-related inflammation. The presence of PD-L1+ HLA-DR+ macrophage-like or dendritic cell-like antigen-presenting cells in tumour stroma was found in organotypic tumour-tissue slice cultures produced from the same patient’s cancer tissue. Intracellular hyaluronan was typically seen in stroma-associated PD-L1+ cells. Overall, the outcomes show that the interaction between tumour-recruited myeloid cells and stromal HA might influence kidney cancer inflammation and immunological tolerance.
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