Systematic characterization of the tumor microenvironment in Chinese patients with hepatocellular carcinoma highlights intratumoral B cells as a potential immunotherapy target

Hepatocellular carcinoma (HCC) is an immunogenic malignancy, which exhibits low responsiveness to programmed cell death protein-1 (PD-1)/programmed death ligand-1 (PD-L1) antibodies. Therefore, the identification of novel immunotherapeutic targets to treat HCC is imperative. Systematic characterization of the HCC tumor microenvironment (TME) can provide novel insight into additional therapeutic approaches. In the present study, the RNA-sequencing (RNA-seq) data of 360 patients with HCC were integrated from The Cancer Genome Atlas to assess the expression of membrane spanning 4-domains A1 (MS4A1; encoding CD20) in tumors and normal liver tissues. Immunofluorescence and multiplex tissue fluorescence analyses were performed and combined with flow cytometry staining to measure CD20/CD19 expression at the protein level. In addition, published single cell RNA-seq data of CD45(+) cells were derived from 16 treatment-naïve patients from Beijing Shijitan Hospital with HCC to illustrate the characteristics of CD19(+) B cells. The results indicated that the HCC TME included nuclear receptor subfamily 4 group A member 2(+) (NR4A2) B cells. Patients with HCC and high density of intratumoral B cells demonstrated compromised antitumor immunity manifested by low percentages of cytotoxic CD8(+) T cells and high density of regulatory T cells. Furthermore, PD-L1 expression was significantly correlated with the B cell signature marker CD20. The present study indicated that tumor-infiltrating B cells may play a negative role in antitumor immunity and serve as a promising target for HCC immunotherapy, alone or in combination with anti-PD-L1/PD-1 antibodies.