Expression and Prognostic Significance of PD-1/PD-Ls in Breast Cancer Draining Lymph Nodes

Tumor-draining lymph nodes play a pivotal role in orchestrating immune cell trafficking and initiating antitumor responses. Among immunoregulatory molecules, programmed cell death protein 1 (PD-1) has emerged as a central mediator in tumor-induced immunosuppression.

To investigate the expression patterns of PD-1 and its ligands (PD-L1, PD-L2) in the tumor-draining lymph nodes of patients with breast cancer (BC).

Lymph node samples were freshly collected from BC patients undergoing surgery. Mononuclear cells were isolated and analyzed by flow cytometry for surface markers CD45, PD-1, PD-L1, and PD-L2. Data were analyzed using FlowJo v10.8.1.

PD-1 was detected on 9.48 ± 5.19% of CD45+ cells, whereas PD-L1 and PD-L2 were expressed at lower levels (1.73 ± 0.85% and 1.68 ± 0.84%, respectively). Despite a significant reduction in the percentage of CD45+ lymphocytes, the frequencies of PD-1+ and PD-L2+ subsets were significantly elevated in patients with poorly-differentiated and advanced-stage tumors (P<0.05). Additionally, the frequency of PD-1+ lymphocytes was significantly higher in patients with the triple-negative tumors (P=0.014) and in those negative for estrogen and progesterone receptor (P=0.001).

Elevated expression of PD-1 and its ligands in BC-draining lymph nodes is associated with adverse clinical features, suggesting their role in immune evasion. These findings along with higher frequency of PD-1+ lymphocyte in triple-negative patients may inform subtype-specific therapeutic strategies and predict responsiveness to PD-1/PD-Ls blockade therapies. Future studies should include functional analyses with broader immunophenotyping to further elucidate these mechanisms.