ICOS-Positive Regulatory T Cells in Hepatocellular Carcinoma: The Perspective from Digital Pathology Analysis

Abstract

Introduction: Inducible co-stimulator (ICOS), an important co-stimulatory receptors on effector T cells (Teffs), may also contribute to tumor growth due to its high expression on regulatory T cells (Tregs). This study explored the clinical significance of ICOS-expressing Tregs in hepatocellular carcinoma (HCC). Methods: Tumor tissues from HCC patients who received curative hepatectomy were obtained at a referral center. Dual immunohistochemistry was performed to evaluate the expression of ICOS and Foxp3. The cell densities and proximities between stained cells in regions of interest were measured by digital pathology and the associations with clinical outcome were analyzed. Results: A total of 142 patients (male: female= 112: 30, median age of 61.0 years) were enrolled. Among them, 87 (61.3%) had chronic hepatitis B virus infection and 33 (23.2%) had chronic hepatitis C infection. Low AFP level (<20 ng/ml) and early-stage were significantly associated with improved overall survival (OS). The density of ICOS＋Foxp3＋ cells and the ratio of ICOS+Foxp3+/total Foxp3+ cells were significantly higher (p<0.001) in the tumor center than in the peritumor area. Patients with a high density of ICOS＋Foxp3＋ cells or a high ratio of ICOS+Foxp3+/total Foxp3+ cells in the tumor center trended to have a shorter OS. A shorter distance between ICOS＋Foxp3＋ cells and ICOS＋Foxp3－ cells (likely Teffs) in the tumor center was significantly associated with a shorter OS (p=0.030), suggesting active immunosuppression of ICOS＋ Tregs on ICOS＋ Teffs. Conclusion: An increased abundance of ICOS＋ Tregs in the tumor center in comparison to the peritumor area indicates a strong immunosuppressive tumor microenvironment of HCC. A high proportion of ICOS+Foxp3+ cells and a shorter distance between ICOS+ Tregs and other ICOS+ cells were associated with a poor OS, suggesting that depleting ICOS+ Tregs might provide clinical benefit for patients with HCC.

Engaging stimulatory immune checkpoint interactions in the tumour immune microenvironment of primary liver cancers – how to push the gas after having released the brake

“…Upregulation of ICOSL on HCC tumour-derived plasmacytoid DCs (pDCs) was hypothesised to activate type 1 regulatory T (Tr1) cells only ( 53 ). However, in HCC TILs, ICOS is upregulated both on Tregs as well as on CD4 + TILs that demonstrated features of recent activation and displayed increased proliferative capacity as well ( 54 – 57 ). Therefore, ICOS signaling in HCC might both enhance and hamper local tumour control by liver-resident immune cells.…”