Triple-negative breast cancer (TNBC) represents one of the most aggressive malignancies, frequently developing TNBC therapeutic resistance. Recent single-cell analysis reveals that two distinct myeloid circuits govern this resistance. These circuits appear to be programmed by either inflammation or resolution processes. Specifically, the phenotype depends heavily on the tumor's histological subtype. Understanding these pathways is essential for developing effective precision oncology strategies in the future.

Divergent Macrophage Phenotypes in TNBC Therapeutic Resistance

Researchers have discovered that macrophages within refractory tumors split into two opposing phenotypes. In epithelial-like tumors, the microenvironment recruits pro-inflammatory macrophages and neutrophils. These cells primarily utilize ω-6 fatty acid pathways to produce prostaglandins, which suppress the local immune response. Conversely, mesenchymal-like tumors expand pro-resolution macrophages. These cells undergo significant metabolic reprogramming via ω-3 fatty acid uptake and the production of resolvins. Furthermore, a critical discovery involves macrophage-secreted C1q. This protein acts as a principal antagonist to T-cell function. In particular, C1q targets mitochondria to induce metabolic dysfunction. Consequently, this process effectively silences the anti-tumor immune attack and promotes TNBC therapeutic resistance.

Targeting Metabolic Regulators to Overcome Evasion

Although these two axes appear distinct, they share a common upstream regulator known as ELOVL5. This fatty acid elongase is integral to both ω-3 and ω-6 metabolism. Therefore, knocking down ELOVL5 can mitigate the immunosuppression driven by both macrophage subsets. This convergent mechanism provides a promising therapeutic vulnerability. Moreover, targeting these circuits may resensitize resistant tumors to standard immuno-chemotherapy. In contrast to broad-spectrum treatments, focusing on these metabolic programs allows for a more nuanced approach to cancer care. Ultimately, disrupting these myeloid programs could restore immunosurveillance and improve outcomes for patients with refractory disease.

Frequently Asked Questions

How do different TNBC subtypes exhibit resistance?

Epithelial-like tumors utilize pro-inflammatory myeloid cells and ω-6 fatty acids, while mesenchymal-like tumors rely on pro-resolution macrophages and ω-3 fatty acid pathways to evade the immune system.

What role does C1q play in treatment failure?

C1q is secreted by pro-resolution macrophages and directly impairs T-cell mitochondria. This leads to metabolic dysfunction, preventing T-cells from destroying cancer cells effectively.

Why is ELOVL5 considered a strategic target?

ELOVL5 is an enzyme that regulates the fatty acid pathways used by both types of immunosuppressive macrophages. Targeting it may stop multiple resistance mechanisms simultaneously.

Disclaimer: This content is for informational and educational purposes only. It does not constitute medical advice or a professional recommendation. Always seek the advice of a qualified healthcare provider for any medical condition or treatment. Refer to the latest local and national guidelines for clinical practice.

References

Yu L et al. Inflammation- and resolution-programmed myeloid circuits govern therapeutic resistance in epithelial and mesenchymal triple-negative breast cancer. J Clin Invest. 2026 Feb 17. doi: undefined. PMID: 41701526.

Yang Y et al. The immune-metabolic crosstalk between CD3+C1q+TAM and CD8+T cells associated with relapse-free survival in HCC. Front Immunol. 2023 Feb 09. doi: 10.3389/fimmu.2023.1033497.

Medina-Estrada I et al. Macrophage Heterogeneity in the Breast Cancer Microenvironment. Front Oncol. 2020 Sep 02. doi: 10.3389/fonc.2020.551920.