Tumor-infiltrating, interleukin-33-producing effector-memory CD8(+) T cells in resected hepatocellular carcinoma prolong patient survival.

Interleukin-33 (IL-33), a cytokine with pleiotropic functions, is elevated in serum of patients with hepatocellular carcinoma (HCC). This study investigated the effects of local IL-33 expression in resected HCC on patient survival and on the immunological and molecular tumor microenvironment. Tissue of resected HCCs was stained for hematoxylin and eosin, Masson trichrome, alpha-smooth muscle actin, IL-33, CD8, and IL-13 and analyzed by flow cytometry. Besides histomorphologic evaluation, the immunohistochemical stainings were analyzed for the respective cell numbers separately for tumor area, infiltrative margin, and distant liver stroma. These findings were correlated with clinical data and patient outcome. Further, gene expression of different HCC risk groups was compared using microarrays. In multivariable analysis, infiltration of HCCs by IL-33(+) cells (P=0.032) and CD8(+) cells (P=0.014) independently was associated with prolonged patient survival. Flow cytometry demonstrated that cytotoxically active subpopulations of CD8(+) cells, in particular CD8(+)CD62L(-)KLRG1(+)CD107a(+) effector-memory cells, are the main producers of IL-33 in these HCC patients. Using infiltration by IL-33(+) and CD8(+) cells as two separate factors, an HCC immune score was designed and evaluated that stratified patient survival (P=0.0004). This HCC immune score identified high- and low-risk patients who differ in gene expression profiles (P<0.001). Conclusion: Infiltration of HCCs by IL-33(+) and CD8(+) cells is independently associated with prolonged patient survival. We suggest that this is due to an induction of highly effective, cytotoxically active CD8(+)CD62L(-)KLRG1(+)CD107a(+) effector-memory cells producing IL-33. Based on these two independent factors, we established an HCC immune score that provides risk stratification for HCC patients and can be used in the clinical setting. (Hepatology 2015;61:1957-1967)