Immunogenomic landscape of hepatocellular carcinoma with immune cell stroma and EBV-positive tumor-infiltrating lymphocytes

Abstract

Background & aims: The immunogenomic characteristics of hepatocellular carcinomas (HCCs) with immune cell stroma (HCC-IS), defined histologically, have not been clarified. We investigated the clinical and molecular features of HCC-IS and the prognostic impact of Epstein-Barr virus (EBV) infection.

Methods: We evaluated 219 patients with conventional HCC (C-HCC) and 47 with HCC-IS using in situ hybridization for EBV, immunohistochemistry, multiplex immunofluorescence staining, and whole exome and transcriptome sequencing. Human leukocyte antigen types were also extracted from the sequencing data. Genomic and prognostic parameters were compared between HCC-IS and C-HCC.

Results: CD8 T cell infiltration was more frequent in HCC-IS than C-HCC (mean fraction/sample, 22.6% vs. 8.9%, false discovery rate q <0.001), as was EBV positivity in CD20-positive tumor-infiltrating lymphocytes (TILs) (74.5% vs. 4.6%, p <0.001). CTNNB1 mutations were not identified in any HCC-IS, while they were present in 24.1% of C-HCC (p = 0.016). Inhibitory and stimulatory immune modulators were expressed at similar levels in HCC-IS and EBV-positive C-HCC. Global hypermethylation, and expression of PD-1 and PD-L1 in TILs, and PD-L1 in tumors, were also associated with HCC-IS (p <0.001), whereas human leukocyte antigen type did not differ according to HCC type or EBV positivity. HCC-IS was an independent factor for favorable recurrence-free survival (adjusted hazard ratio [aHR] 0.23; p = 0.002). However, a subgroup of tumors with a high density of EBV-positive TILs had poorer recurrence-free (aHR 25.48; p <0.001) and overall (aHR 9.6; p = 0.003) survival, and significant enrichment of CD8 T cell exhaustion signatures (q = 0.0296).

Conclusions: HCC-IS is a distinct HCC subtype associated with a good prognosis and frequent EBV-positive TILs. However, paradoxically, a high density of EBV-positive TILs in tumors is associated with inferior prognostic outcomes. Patients with HCC-IS could be candidates for immunotherapy.

Lay summary: Hepatocellular carcinomas with histologic evidence of abundant immune cell infiltration are characterized by frequent activation of Epstein-Barr virus in tumor-infiltrating lymphocytes and less aggressive clinical behavior. However, a high density of Epstein-Barr virus-positive tumor-infiltrating lymphocytes is associated with inferior prognostic outcomes, possibly as a result of immune escape due to significant CD8 T cell exhaustion.

Keywords: Epstein-Barr virus; Hepatocellular carcinoma; Immune; Sequencing.