Identification of Two Distinct Immune Subtypes in Hepatitis B Virus (HBV)-Associated Hepatocellular Carcinoma (HCC)

Simple Summary Chronic hepatitis B virus (HBV) infection remains a major public health problem and the most common risk factor for the development of hepatocellular carcinoma (HCC). The prognosis of HCC is still ominous because diagnosis is usually made at advanced stages and therapeutic options are limited. Immunotherapy is increasingly used for treatment of solid tumors, including advanced HCC. However, most HCC patients do not respond to immunotherapy. The tumor microenvironment (TME) plays a crucial role in intratumor heterogeneity and evolution, treatment failure, and, ultimately, disease outcome. However, there is very limited information on the TME of HBV-HCC. Our study provides evidence that HBV-HCC is characterized by two distinct immune subtypes, immune-high and immune-low. We documented a high expression of CTLA-4 in the immune-high subtype. Our results may have implications in the context of new treatment combinations for HCC to identify patients who might benefit the most from immunotherapy.Abstract HBV is the most common risk factor for HCC development, accounting for almost 50% of cases worldwide. Despite significant advances in immunotherapy, there is limited information on the HBV-HCC tumor microenvironment (TME), which may influence the response to checkpoint inhibitors. Here, we characterize the TME in a unique series of liver specimens from HBV-HCC patients to identify who might benefit from immunotherapy. By combining an extensive immunohistochemistry analysis with the transcriptomic profile of paired liver samples (tumor vs. nontumorous tissue) from 12 well-characterized Caucasian patients with HBV-HCC, we identified two distinct tumor subtypes that we defined immune-high and immune-low. The immune-high subtype, seen in half of the patients, is characterized by a high number of infiltrating B and T cells in association with stromal activation and a transcriptomic profile featuring inhibition of antigen presentation and CTL activation. All the immune-high tumors expressed high levels of CTLA-4 and low levels of PD-1, while PD-L1 was present only in four of six cases. In contrast, the immune-low subtype shows significantly lower lymphocyte infiltration and stromal activation. By whole exome sequencing, we documented that four out of six individuals with the immune-low subtype had missense mutations in the CTNNB1 gene, while only one patient had mutations in this gene in the immune-high subtype. Outside the tumor, there were no differences between the two subtypes. This study identifies two distinctive immune subtypes in HBV-associated HCC, regardless of the microenvironment observed in the surrounding nontumorous tissue, providing new insights into pathogenesis. These findings may be instrumental in the identification of patients who might benefit from immunotherapy.