Deciphering the Multifaceted Immune Landscape of Unresectable Primary Liver Cancer to Predict Immunotherapy Response.

Immunotherapies employing PD-1/PD-L1 immune checkpoint inhibitors (ICIs) are vital for primary liver cancer (PLC), but response rates remain unsatisfying. Accurate differentiation of responders from non-responders to immunotherapy is imperative. Here, single-cell-scaled mass cytometry analysis on sequential peripheral blood mononuclear cells (PBMCs) from ICI-treated PLC patients is conducted, and tissue residence of immune subpopulations is assessed via multiplex immunohistochemistry. In the discovery cohort (n = 24), responders have lower baseline B cell and HLA-DRCD8T cell, and higher CD14CD16 classical monocyte (CM) proportions. CMs decrease more in responders PBMCs, while HLA-DRCD8T cells conformably amplify after ICI-exposure. Responsive individuals display upregulated exhaustion and activation markers in peripheral immune lineages. In the expanded cohort of 77 patients, the augment of the B cells in non-responders is re-confirmed. Responders demonstrate much higher enrichment of B cells or tertiary lymphoid structures in tumor compared to non-responders. A prospective model that excelled in early discrimination of responders is developed using generalized linear model and achieves a satisfactory AUC over 0.9 in all three independent cohorts. Integratedly, the study unveils dynamic immune landscapes in PLC patients undergoing ICI-based therapy, aiding in PLC patient stratification for ICI-based treatment and fostering new response monitoring strategies.