# Targeting the Tumor Microenvironment in Triple-Negative Breast Cancer: Emerging Roles of Monoclonal Antibodies and Immune Modulation

## TL;DR

This review explores how monoclonal antibodies and immune modulation can target the tumor microenvironment in triple-negative breast cancer to improve treatment outcomes.

## Contribution

The paper highlights emerging roles of monoclonal antibodies in modulating the immunosuppressive tumor microenvironment of TNBC.

## Key findings

- TNBC's immunosuppressive tumor microenvironment is a key driver of progression and resistance to treatment.
- Monoclonal antibodies show promise by disrupting immunosuppressive signaling and enhancing immune effector functions.
- Combination strategies and TME modulation are being explored to optimize monoclonal antibody efficacy in TNBC.

## Abstract

Triple-negative breast cancer (TNBC) is a subtype of breast cancer that lacks expression of estrogen, progesterone, and HER2 receptors. This cancer represents a major therapeutic challenge due to limited targeted treatment options and an immunosuppressive tumor microenvironment (TME). Recent advances highlight the potential of monoclonal antibodies (mAbs), especially those targeting immune checkpoints and TME components, as promising therapeutic agents. This narrative review highlights current knowledge on the interaction between TNBC and its microenvironment, emphasizing how mAbs disrupt immunosuppressive signaling, modulate stromal architecture, and enhance immune effector functions. We further explore combination strategies and ongoing clinical developments aimed at optimizing mAb efficacy within the complex TME of TNBC.

Triple-negative breast cancer (TNBC) is an aggressive and clinically challenging subtype of breast cancer characterized by the absence of estrogen receptor, progesterone receptor, and HER2 expression. This molecular phenotype narrows the availability of targeted therapies and contributes to high rates of early relapse, therapeutic resistance, and poor clinical outcomes. Mounting evidence pinpoints the tumor microenvironment (TME) as a central driver of TNBC progression, immune evasion, and resistance to treatment. The TME encompasses a complex and dynamic network of immune and stromal cells, extracellular matrix components, and soluble mediators that collectively shape tumor behavior and influence therapeutic response. Notably, TNBC often displays an immunologically active microenvironment, marked by high levels of tumor-infiltrating lymphocytes and immune checkpoint expression, opening a window for immune-based therapeutic strategies. This narrative review summarizes current knowledge on the cellular, molecular, and structural features of the TNBC tumor microenvironment, with particular focus on immunosuppressive mechanisms mediated by tumor-associated macrophages, myeloid-derived suppressor cells, cancer-associated fibroblasts, and dysfunctional T cells. We describe the clinical development and therapeutic impact of monoclonal antibodies, including immune checkpoint inhibitors and antibody–drug conjugates. Additionally, we discuss strategies aimed at modulating the TME to enhance monoclonal antibody efficacy, including immune cell reprogramming, extracellular matrix remodeling, cytokine/chemokine blockade, and combination treatment strategies. Finally, we highlight the role of biomarker-driven patient stratification and personalized therapeutic strategies, addressing current challenges and future directions in TME-targeted drug development. Together, these insights underscore the potential of integrating immune modulation and monoclonal antibody-based therapies to improve outcomes for TNBC patients.