Systemic immune activation coexists with compartment-specific regulatory enrichment in matched blood, peritumor, and tumor tissue from advanced oral squamous cell carcinoma

Abstract

Oral squamous cell carcinoma (OSCC) is the most prevalent form of oral cancer and is characterized by a poor prognosis and frequent immune evasion. While the tumor microenvironment (TME) plays a central role in modulating responses to therapy, its relationship with systemic immune signatures remains poorly understood. We performed high-dimensional immune profiling in matched peripheral blood, adjacent non-neoplastic peritumor mucosa, and tumor tissue from Human Papillomavirus (HPV)-negative, treatment-naïve patients with advanced OSCC. Soluble mediators were quantified by multiplex immunoassay, and immune cell phenotypes were assessed by multiparametric flow cytometry. Compartment-specific patterns were evaluated using paired and unpaired comparisons, dimensionality reduction, ordinal trend analysis, unsupervised clustering, and correlation networks. Seventeen plasma mediators were significantly elevated in OSCC patients compared with healthy donors. Paired cellular profiling identified compartment-specific differences across blood, peritumor and tumor, and selected PD-1 + CD95 + , CD25 + FoxP3 + , and PD-L1 + populations showed significant progressive trends along the blood-peritumor-tumor axis. CD4 + mucosal-associated invariant T (MAIT)-like cells (TCR Vα7.2 + CD161 + ) were relatively enriched in peritumor tissue, but the peritumor compartment was not uniformly intermediate across all populations. Correlation networks showed limited overlaps, with greater overlap between peritumor and tumor networks than between either tissue compartment and blood. Plasma profiling showed elevated pro-inflammatory cytokines, chemokines, and growth factors, consistent with systemic immune activation. Peripheral blood exhibited an activated phenotype with increased frequencies of activated T and NK cells, alongside CD4 - CD8 - TCR Vα7.2 + CD161 + cells. In contrast, the tumor microenvironment was enriched for CD95 + PD-1 + CD4 + and CD8 + T cells, NK cells and PD-L1 + monocytes and CD4 + MAIT-like cells. The peritumor compartment showed a distinct immune profile marked by regulatory T cell accumulation and other immunosuppressive mediators, rather than a uniform intermediate state between blood and tumor. Correlation networks revealed pronounced shifts in immune coordination across compartments. Advanced OSCC is associated with distinct systemic and tissue immune profiles. These exploratory findings identify compartment-specific immune features and selected monotonic trends that warrant future spatial, functional, and clinical validation.