PFDN5 synergizes with anti-PD1 therapy to promote triple-negative breast cancer cell death through JAK2/STAT3/c-Myc signaling axis

Triple-negative breast cancer (TNBC) shows aggressive clinical behavior and lacks targeted therapeutic options, underscoring the need for novel treatment approaches. Prefoldin subunit 5 (PFDN5), a co-chaperone involved in tumor suppression and c-Myc regulation, remains largely unstudied in TNBC. This study aims to elucidate the functional role of PFDN5 in TNBC progression and its impact on the immune microenvironment. PFDN5 expression was examined in TNBC clinical specimens and cell lines. Functional assays, including proliferation, clonogenicity, migration, apoptosis, and epithelial-mesenchymal transition (EMT), were performed in vitro following stable PFDN5 overexpression or CRISPR/Cas9-mediated depletion. In vivo validation was performed using xenograft models in both immunodeficient and immunocompetent mice. Mechanistic studies incorporated bioinformatics, protein array analyses, and multi-dimensional characterization of tumor-immune interactions via single-cell RNA sequencing (scRNA-seq), spatial transcriptomics, and multiplex immunohistochemistry (mIHC). Furthermore, the therapeutic potential of PFDN5 overexpression in combination with anti-PD-1 immune checkpoint blockade was preliminarily evaluated in a mouse model. PFDN5 mRNA/protein levels were markedly reduced in TNBC, correlating with poor survival. Overexpression inhibited proliferation, colony formation, migration, EMT, and promoted apoptosis, whereas knockout enhanced tumorigenic traits. Mechanistic analyses integrating bioinformatics and protein arrays identified JAK/STAT signaling as a key pathway enriched in PFDN5-associated differentially expressed genes (DEGs) and proteins (DEPs). In vivo, PFDN5 overexpression significantly inhibited TNBC xenograft growth in nude mice, accompanied by reduced activation of JAK2/STAT3/c-Myc signaling. Single-cell and spatial transcriptomic analyses revealed that PFDN5 expression was linked to altered immune cell infiltration and immune checkpoint profiles. Specifically, mIHC demonstrated an inverse correlation between PFDN5 expression and the infiltration of CD8+ T cells and immunosuppressive regulatory T cells (Tregs). Combination therapy with PFDN5 overexpression and anti-PD-1 blockade induced synergistic antitumor effects, characterized by enhanced CD8+ T cell infiltration and improved tumor control. This study identifies PFDN5 as a critical tumor suppressor in TNBC, exerting dual functions by suppressing JAK2/STAT3/c-Myc signaling and modulating the immunosuppressive tumor microenvironment. Restoring PFDN5 expression improves the efficacy of immune checkpoint inhibitors, highlighting its potential as a therapeutic target. These findings provide a strong rationale for developing combination therapies targeting PFDN5 to overcome therapeutic resistance in TNBC.