CD8+ lymphocyte infiltration and apoptosis in hepatocellular carcinoma

Aims. Tumour-infiltrating lymphocytes (TILs) play a role in local anti-tumour immunity. Tumour cells may escape from immune surveillance by expressing RCAS1, a receptor-binding cancer antigen expressed on SiSo cells, which inhibits T cell growth. In this study, the correlation between the density of CD8+ TILs, tumour cell apoptosis, and tumour RCAS1 expression was investigated in hepatocellular carcinoma (HCC). Methods. We obtained tissues from 60 patients with surgically resected HCCs. CD8+ TILS, apoptotic cancer cells, and RCAS1 expressing cancer cells were identified by immunohistochemistry. Results. The density of CD8+ T cells in tumours (mean: 9.5/HPF, HPF: high power field) was significantly less than in non-cancerous hepatic lobules (17.8/HPF, p<0.001) and in relation to the progression of tumour stage. The density of CD8+ T cells in tumours positively correlated with the occurrence of tumour cell apoptosis, but did not correlate with RCAS1 protein expression. Conclusions. CD8+ TILs may play a role in the occurrence of tumour cell apoptosis in HCC, but CD8+ TILs may not be controlled by RCAS1 in HCC.