Inhibition of T-cell responses by intratumoral hepatic stellate cells contribute to migration and invasion of hepatocellular carcinoma

Abstract

The stroma of hepatocellular carcinoma (HCC) is markedly infiltrated with activated hepatic stellate cells (HSCs), and associated invasion and metastasis of HCC. However, little is known of the role of HSCs in immune responses in HCC. The Buffalo rat HCC model was established. Quiescent HSCs (qHSCs) and intratumoral HSCs (tHSCs) were isolated. Surface molecules of tHSC were detected by flow cytometry, and gene expression was analyzed by fluorescence quantitative RT-PCR. T cell proliferation was monitored by [(3)H]-thymidine ((3)H-TdR) incorporation into DNA, and cytotoxic activity was assessed by measuring the release of (51)Cr. The level of cytokine expression by T cells was measured by enzyme-linked immunosorbent assay. T cell apoptosis was detected by double-stained terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) and anti-CD3 antibodies. The migration and invasion of HCC was observed by transwell experiments. tHSCs express low levels of major histocompatibility complex (MHC) class I, MHC class II, and costimulatory molecules, and produce varying levels of cytokines. Addition of the tHSCs suppressed thymidine uptake by T cells that were stimulated by alloantigens or by anti-CD3-mediated T-cell receptor ligation. The tHSC-induced T-cell hyporesponsiveness was associated with enhanced T-cell apoptosis, and contributed to the migration and invasion of hepatoma cell. tHSCs was associated with markedly enhanced expression of B7-H1. Blockade of B7-H1/PD-1 ligation significantly reduced HSC immunomodulatory activity, and hepatoma cell migration and invasion. tHSCs can induce T cell apoptosis, suggesting an important role for B7-H1. The interactions between tHSCs and T cells may contribute to hepatic immune tolerance and invasion and migration of HCC.