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

## TL;DR

This study examines immune-checkpoint expression in breast cancer patients and finds differences in expression patterns across tumor subtypes and grades.

## Contribution

The study identifies distinct immune-checkpoint expression profiles in different breast cancer subtypes and tumor grades, offering insights for immunotherapy strategies.

## Key findings

- Triple-negative and Her-2 tumors show higher PD-1, PD-L1, CTLA-4, and TIGIT expression compared to Luminal A and B tumors.
- High-grade tumors exhibit increased PD-1, PD-L1, LAG-3, and VISTA expression compared to lower-grade tumors.
- PD-L1/TIGIT co-expression in tumor-infiltrating cells is significantly different in triple-negative tumors compared to other subtypes.

## Abstract

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.