Sabrina Dhooge

Argentina

Peripheral and tumor immune signatures predict response to immunotherapy in advanced HER2-negative breast cancer

Sabrina Dhooge¹, Ekaterina Friebel², Boffelli Lucia¹, Dutto Jeremias¹, Flores Ana Paula¹, Bustos Jeremias¹, Biasi Pilar ¹, Silvana Mouron³, Miguel Quintela-Fandino³, Burkhard Becher² Mariana Maccioni¹ and Nicolas Nuñez ¹

¹Centro de Investigaciones en Bioquímica Clínica e Inmunología, CIBICI-CONICET, Departamento de Bioquíımica Clínica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba, Argentina
²Institute of Experimental Immunology, University of Zurich, Zurich, Switzerland.
³Breast Cancer Clinical Research Unit – Clinical Research Program, CNIO РSpanish National Cancer Research Center, Madrid, Spain.

Abstract

Background

HER2-negative advanced breast cancer (BC) is an aggressive subtype that remains challenging to treat with conventional therapies. Although immune checkpoint blockade (ICB), such as PD-L1–targeted therapy, has shown clinical activity, responses remain heterogeneous and difficult to predict. Understanding the immune mechanisms driving treatment response is essential to refine patient selection and guide personalized therapeutic strategies. This study aimed to identify peripheral and tumor immune biomarkers associated with response to anti–PD-L1 therapy by integrating multi-omics immune profiling with clinical data to improve prediction of immunotherapy outcomes.

Methods

A prospective study was conducted in 26 patients with advanced BC. PBMCs were analyzed at baseline (week 0), prior to the initiation of anti-PD-L1 therapy, and at weeks 4, 8, and 28 during treatment using mass cytometry (CyTOF) and flow cytometry (FACS). Additionally, scRNA-seq data from responders (R) and non-responders (NR) in the Yuanyuan cohort, who were also treated with anti-PD-L1 therapy, were processed using Seurat to identify transcriptional profiles of regulatory T cells (Tregs). Statistical analyses included Mann-Whitney U tests to compare immune phenotypes and Kaplan-Meier analysis to evaluate survival outcomes, assessing correlations between immune signatures and clinical endpoints.

Results

CyTOF analysis revealed that at baseline, NRs to ICB therapy exhibited higher frequencies of PDL1+ monocytes, Ki67- Tregs, and naive B cells compared to Rs. Survival analysis revealed that Treg Ki67- and Mo PDL1+ cells were associated with poorer outcomes (p=0.009 and p=0.046, respectively).
scRNA-seq transcriptional profiling of FOXP3+ Tregs in the Yuanyuan cohort revealed a naive-like signature enriched in Rs, mirroring systemic differences observed in circulating immune cells.

Conclusions

Peripheral immune signatures, such as elevated Treg Ki67- and PDL1+ monocytes in NRs, and naive-like FOXP3+ Tregs in Rs, provide insights into mechanisms driving ICB response. These findings highlight the value of integrating peripheral and tumor biomarker analyses to enhance immunotherapy strategies in advanced BC.