Proteogenomic Characterization of Triple-Negative Apocrine Carcinoma Reveals Molecular Features of Progression and Chemotherapy Response

Triple-negative apocrine carcinoma (TNAC) is an exceptionally rare, chemotherapy-insensitive subtype of triple-negative breast cancer (TNBC) characterized by androgen receptor (AR) positivity and low proliferative activity. Despite poor chemotherapy response, TNAC exhibits favorable long-term survival, suggesting distinct resistance mechanisms. Here, we integrate mass spectrometry-based proteomics and whole-exome sequencing (WES) to characterize TNACs molecular features. We identify progressive overexpression of PI3K/AKT and AR signaling proteins, along with ECM remodeling and upregulation of GTPase-related proteins, highlighting TNACs invasive potential. WES reveals somatic mutations in ECM-related genes (COL18A1) and immune-associated genes (C3, NRDC), implicating the tumor microenvironment. Unlike TNBC, post-chemotherapy TNAC proteomics shows mixed ribosomal regulation and heightened inflammation, rather than reliance on proliferation, suggesting a need for targeted metabolic and immune therapies. Our findings support PI3K/AKT inhibitors and AR antagonists, potentially alongside GTPase inhibitors, metabolic disruptors, and immune therapy, as alternative strategies to standard chemotherapy in TNAC.