T lymphocytes, which recognize antigen peptides through specific T cell receptors (TCRs), play an important role in the human adaptive immune response. TCR diversity is closely associated with host immune response and cancer prognosis. Although tumor-infiltrating T lymphocytes have implications for tumor prognosis, few studies have performed a detailed characterization of TCR diversity in both tumor and non-tumor tissues in hepatitis B virus (HBV)-associated hepatocellular carcinoma (HCC). Here, we performed high-throughput sequencing of the TCRβ chain complementarity determining region 3 (CDR3) of liver-infiltrating T cells from 48 HBV-associated HCC patients. A significantly higher average number of CDR3 aa clonotypes (2259 vs. 1324, p < 0.001), and significantly higher TCR diversity (Gini coefficient, p < 0.001; Simpson index, p < 0.01; Shannon entropy, p < 0.001) were observed in tumor tissues compared with adjacent non-tumor tissues. The ratio of highly expanded clones (HECs) was significantly higher in non-tumor tissues than in tumor tissues when the HEC threshold was defined as 2% or greater (p < 0.05). Our analysis of the median Morisita-Horn index indicated weak TCR repertoire similarity between tumor and matched non-tumor tissues. The median number of shared clones in tumor tissue and matched non-tumor tissue from each patient was 360.5, representing 5.1-15.8% (10.6 ± 0.4%) of all clones in each patient. We observed extensive heterogeneity of T lymphocytes in tumors and higher HEC ratios in adjacent non-tumor tissues of HCC patients. The differential T cell repertoires in tumor and non-tumor tissues suggest a distinct T cell immune microenvironment in patients with HBV-associated HCC.
Keywords: Diversity; T cell receptor; hepatitis B virus; hepatocellular carcinoma; high-throughput sequencing.