Gemcitabine-cisplatin chemotherapy plus anti-PD-L1 therapy reinvigorates antitumor immune response by reprogramming the intrahepatic cholangiocarcinoma microenvironment.

[PURPOSE] Gemcitabine-cisplatin chemotherapy combined with anti-PD-L1 (GCP) therapy exhibits potent antitumor efficacy in patients with advanced intrahepatic cholangiocarcinoma (ICC). We aim to determine the intra-tumoral changes of ICC following GCP therapy in this study.

[METHODS] We performed single-cell RNA-seq (scRNA-seq) of 15 samples from 3 ICC patients receiving GCP therapy. The major findings of scRNA-seq analyses were further validated via analyzing the bulk RNA-seq data from the FU-iCCA cohort (n=244), as well as performing immunohistochemistry (IHC) and multiplex immunofluorescence (mIF) staining on a treatment-naïve tissue microarray (TMA) cohort (n=89) and a GCP-treated cohort (n=32).

[RESULTS] For the scRNA-seq cohort, two patients achieved tumor regression and underwent liver resection after GCP combination therapy. The intra-tumoral enrichment of CCL18 macrophages correlated with poor prognosis of ICC patients after curative resection in the TMA cohort. Reduced fractions of CCL18 and SPP1 macrophages were observed in the GCP-treated ICC specimens which achieved pathological response. Our scRNA-seq analyses revealed significant alterations in the tumor microenvironment following GCP therapy: tumor-infiltrating macrophages underwent a distinct antitumor phenotypic shift, transitioning from M2 toward M1 polarization; concurrently, CD8 T cells exhibited enhanced costimulatory signaling characterized by CD81 upregulation and malignant cells demonstrated diminished immune escape characteristics alongside heightened activity in immune response-related pathways.

[CONCLUSIONS] Our preliminary findings reveal a generally reactivated antitumor immune response in ICC following GCP therapy, which could partly illuminate the enigmatic black box of intra-tumoral cellular states associated with treatment response.