Immune-Checkpoint Expression in Breast Cancer Patients: Clinicopathological Implications: A Retrospective Case Series Study

Immunotherapy with antibodies targeting immune checkpoints, in combination with standard therapies, is one of the areas with the most significant clinical research, particularly in aggressive tumors such as triple-negative breast cancer, where there have been relevant advances with antibodies against PD-1/PD-L1. However, it is essential to define the biological and molecular factors that influence survival and response to immunotherapy, as other immune control points, such as CTLA-4, TIM-3, LAG-3, TIGIT, and VISTA, also play a role. The immune checkpoints were studied by microarrays and immunohistochemistry in 243 samples from patients with breast cancer, according to the molecular subtype. Significant differences in PD-1, PL-1, CTLA-4, and TIGIT expression were observed between triple-negative and Her-2 tumors compared to Luminal A and Luminal B tumors. No differences in VISTA expression were observed between the different molecular subtypes. Patients with high-grade tumors showed higher PD-1, PD-L1, LAG-3, and VISTA expression than low and intermediate-grade tumors. We observed a significant difference in PD-L1/TIGIT co-expression in tumor-infiltrating cells from patients with triple-negative tumors compared to patients with Luminal A, Luminal B, and Her2+ tumors. These results are relevant in the context of clinical application.