Diversity of Memory CD8⁺ T Cells in Tumor-Draining Lymph Nodes from Patients with Bladder Cancer

The role of memory T cells in orchestrating memory responses to previously known tumor antigens is well documented. The aim of this study was to assess the frequency of different memory T cell subsets in tumor-draining lymph nodes of patients with bladder cancer (BC) and their prognostic significance. Mononuclear cells were isolated from 50 tumor-draining lymph nodes of untreated patients with BC and stained with antibodies against the markers CD8, CD95, CD45RO and CCR7. Data were collected using the FACSCalibur flow cytometer and analyzed using FlowJo software. Among the CD8⁺ cytotoxic lymphocytes, the frequency of different subsets was determined including total memory cells (CD8⁺CD45RO⁺CD95⁺), T central memory (TCM: CD8⁺CCR7⁺CD45RO⁺CD95⁺), T effector memory (TEM: CD8⁺CCR7^-CD45RO⁺CD95⁺), T stem cell memory (TSCM: CD8⁺CCR7⁺CD45RO^-CD95⁺) and naïve T cells (CD8⁺CCR7⁺CD45RO^-CD95^-). The analysis revealed that on average 49.32±20.15 (between 1.62% and 87.20%) percent of CD8⁺ lymphocytes in draining lymph nodes of BC had a memory phenotype. TCM cells showed the highest frequency (34.71±17.04), while TSCM cells (7.51±8.53) demonstrated the lowest. The total frequency of memory cells tended to be higher in patients with tumor invasion to muscle layer (P=0.052) and stage III (P=0.042) than in patients without invasion and stage I. The TCM subset was more frequent in patients with necrotic tumors than in patients without necrosis (P=0.048). TSCM significantly increased in patients with N2 compared to N0 (P=0.042). Conversely, the ratio of TSCM cells to total memory cells was higher in lower tumor stages (P=0.059), tumors without muscle invasion (P=0.026) and low T grouping (P=0.043). Overall the data indicated an increase in the frequency of memory T cells and their TSCM and TCM cells with tumor progression. In contrast, the ratio of TSCM to total memory cells was higher in less advanced tumors. These results suggest that the immune system is frequently exposed to tumor antigens and strives to create a memory T cell reservoir, but this is suppressed by inhibitory factors provided by the tumor. These findings emphasize the importance of understanding the dynamic interplay between memory T cell subsets and BC progression.