Exploratory analysis of peripheral blood monocytes in breast cancer using prospective high-dimensional immune profiling
Abstract
Breast cancer is a heterogeneous disease characterized by diverse molecular and immune features and blood-based immunophenotyping may provide insights into systemic immune variation relevant to treatment. Baseline immune profiling before surgery or systemic therapy reflects the natural tumor–host interaction and systemic immune status. In this exploratory, hypothesis-generating study, we integrated in silico analysis of publicly available high-dimensional immune profiling data with an independent prospective assessment of selected peripheral immune populations. Publicly available mass cytometry data from CD45 + viable singlet peripheral blood mononuclear cells of healthy donors, hereditary breast and ovarian cancer predisposition carriers, and breast cancer patients were analyzed using the CATALYST pipeline in R. Based on the immune patterns identified in the public dataset, selected immune populations were subsequently examined in an independent cohort of 11 treatment-naïve breast cancer patients using eight-color flow cytometry. The two approaches were used as complementary analyses rather than as direct technical validation of one another. Unsupervised clustering identified 20 immune metaclusters, with CD4 + T-cell and CD14 + monocyte subsets showing the greatest variation across groups. Patients subsequently allocated to neoadjuvant chemotherapy exhibited higher lymphocyte percentages (median, 53% vs. 42%, P = 0.004) and classical CD14 + + CD16 − monocytes (median, 73% vs. 58%, P < 0.0001), whereas patients undergoing surgery showed higher non-classical CD14 + CD16 + + monocytes (median, 16% vs. 10, P = 0.078). CD80/CD86 co-expression further classified patients into high, moderate, and low activation profiles. These baseline immune differences were associated with subsequent treatment allocation but remain descriptive, as patients had not yet received treatment at the time of peripheral blood sampling, providing preliminary, hypothesis-generating evidence of peripheral immune variation in breast cancer and supporting further investigation of monocyte and lymphocyte populations in larger prospective cohorts.