Alterations in PD-L1+ Myeloid Cells and Immune Infiltration Are Associated with Atezolizumab and Paclitaxel Therapy Success in a Triple-Negative Breast Cancer Model

YILMAZ K., Tavukcuoglu E., Yanik H., Seçken P., Celik E., Guler S., ...More

Medicina (Lithuania), vol.62, no.3, 2026 (SCI-Expanded, Scopus) identifier identifier

  • Publication Type: Article / Article
  • Volume: 62 Issue: 3
  • Publication Date: 2026
  • Doi Number: 10.3390/medicina62030600
  • Journal Name: Medicina (Lithuania)
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Directory of Open Access Journals
  • Keywords: atezolizumab, combination therapy, immune checkpoint inhibitors, metastasis, paclitaxel, treatment response, triple-negative breast cancer, tumor immune microenvironment
  • Hacettepe University Affiliated: Yes

Abstract

Background and Objectives: A combination of chemotherapy and immunotherapy may improve cancer treatment outcomes; however, determining which patient groups will benefit from immunotherapy is critical. Triple-negative breast cancer (TNBC) achieves limited benefit from immune checkpoint inhibitors (ICIs) and anti-PD-L1 blockade therapy. Materials and Methods: In this study, PD-L1 expression levels in myeloid-derived cells in the tumor microenvironment were determined in an experimental TNBC model. Results: Compared with tumor cells, granulocytes, monocytes, and macrophages had significantly higher PD-L1 expression. CD206+ tumor-associated macrophages (TAMs) expressed the highest level of PD-L1. PD-L1 positivity in TAMs was also significantly high in the lung, liver, lymph node, and spleen. Despite treatment initiation in late-stage tumorigenesis, the combination of paclitaxel and the anti-PD-L1 monoclonal antibody atezolizumab significantly reduced tumor growth. In addition, lung metastasis burden was reduced with combined treatment compared with chemotherapy or anti-PD-L1 monotherapy alone. Conclusions: As a result, alterations in PD-L1+ myeloid cells and immune infiltration can be associated with atezolizumab and paclitaxel therapy success in triple-negative breast cancer.