RESUMEN
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.
RESUMEN
INTRODUCTION: HCC is the third leading cause of cancer-related death worldwide, with chronic viral hepatitis accounting for more than 70% of the cases. Therapeutic options are limited and ineffective. The increasing use of immune-based therapies in solid tumors highlights the need to expand our knowledge on the immunologic microenvironment of HCC. METHODS: Access to liver samples from 20 well-characterized patients with HCC associated with HCV (n = 9) or HBV (n = 11) gave us the opportunity to study the immunologic landscape in these tumors. For each patient, RNA-sequencing was performed on the tumor and surrounding nontumorous tissue. RESULTS: We found that both HCV- and HBV-HCC are associated with a predominance of downregulated genes (74% and 67%, respectively). Analysis of the immune landscape using a curated gene list showed 216 of 2481 (9%) immune genes in HCV-HCC and 164 of 2560 (6%) in HBV-HCC. However, only 8 immune genes (4%) were upregulated in HCV-HCC and 27 (16.5%) in HBV-HCC. HCV-HCC was characterized by an enrichment of downregulated genes related to T-cell activation and oxidative stress. The dramatic downregulation of immune genes related to T-cell activation in HCV-HCC prompted us to perform an extensive immunohistochemistry analysis on paraffin-embedded liver specimen. Interestingly, we found a significant reduction of immune-cell infiltration (CD3, CD8 and CD20 positive cells) within the tumor. Moreover, we observed that HCV-HCC is characterized by an enrichment of M2-like CD68-positive cells. These data are consistent with the dramatic downregulation of immune-cell infiltration seen in HCV-HCC. Conversely, HBV-HCC was characterized by upregulation of genes related to monocyte/macrophage activation and cell cycle control, and downregulation of genes involved in various cell metabolisms. CONCLUSION: This study demonstrates a distinctive molecular signature and immune landscape in HCC of different viral etiology, which could provide new insights into pathogenesis and lead to the development of novel immune-based therapies.