BackgroundIntrahepatic cholangiocarcinoma (ICC) is a highly mortal malignancy with limited therapeutic options. Immunotherapies targeting PD-1/PD-L1 pathway represent a promising treatment for ICC. However, PD-L1 expression and microsatellite instability are not common in ICC. This study aimed to investigate whether HHLA2, a newly identified B7 family immune checkpoint for T cells, could be a therapeutic target next to PD-L1 in ICC.MethodsExpression levels of PD-L1 and HHLA2 as well as infiltrations of CD3+, CD8+, CD4 + Foxp3+, CD68+, CD163+ and CD20+ cells were evaluated by immunohistochemistry in 153 resected ICC samples. Comprehensive comparisons were made between PD-L1 and HHLA2 in terms of the expression rates, clinicopathological features and infiltrations of different immune cells. The expression level and prognostic significance of HHLA2 were further validated in an independent cohort.ResultsExpression of HHLA2 is more frequent than PD-L1 in ICC (49.0% vs 28.1%). Co-expression of both immune checkpoints was infrequent (13.1%) and 50% PD-L1 negative cases were with elevated HHLA2. HHLA2 overexpression was associated with sparser CD3+ tumor infiltrating lymphocytes (TILs), CD8+ TILs and a higher CD4 + Foxp3+/CD8+ TIL ratio, whereas PD-L1 expression was associated with prominent T cells and CD163+ tumor associated macrophages infiltrations. PD-L1 failed to stratify overall survival (OS) but HHLA2 was identified as an independent prognostic indicator for OS in two independent cohorts.ConclusionsCompared with PD-L1, HHLA2 is more prevalent and possesses more explicit prognostic significance, which confer the rationale for HHLA2 as a potential immunotherapeutic target next to PD-L1 for ICC patients.Electronic supplementary materialThe online version of this article (10.1186/s40425-019-0554-8) contains supplementary material, which is available to authorized users.

The prognosis of intrahepatic cholangiocarcinoma (ICC) remains poor whereas predictive models for survival prediction in ICC patients following curative resection are limited. Herein, we established a novel inflammation-based score derived from preoperative albumin to gamma-glutamyltransferase ratio (AGR) and evaluated its prognostic significance in ICC patients underwent curative resection. Prognostic value of AGR was retrospectively studied in a cohort comprising 206 ICC patients following curative resection. The predictive performance of AGR was compared with other inflammation-based scores and serological tumor markers in terms of concordance index (C-index). Further, prognostic nomograms incorporating AGR into the tumor-node-metastasis (TNM) staging systems were established to achieve a better discriminatory ability. The optimal cut-off value of AGR was 0.6. Multivariate analysis showed that AGR was an independent predictor for overall survival (OS; P = 0.003) and recurrence-free survival (RFS; P = 0.046). The C-index of AGR was superior to other inflammation-based scores and serological tumor markers in OS and RFS prediction. The established nomograms showed improved predictive accuracy compared with the TNM staging systems alone. These results indicate that AGR is an independent prognostic indicator for ICC underwent curative resection. The incorporation of AGR into the existing TNM staging systems achieved improved predictive accuracy.

The present RFS nomogram for AFP-negative HCC patients after curative resection provides an accurate and reliable prognostic model to facilitate recurrence surveillance. Once AFP-negative patients are predicted to have a high recurrence score, additional high-end imaging examinations, such as MRI or CT exams, should be considered, and the interval time of regular folow-up should be reduced.