Increased mRNA Expression of CCL22 in Hepatocellular Carcinoma with Infiltration of FOXP3+ Regulatory T Cell

Purpose: Tumor-infiltrating lymphocytes are known to play an important role in the tumor-host reaction in various types of neoplasms including hepatocellular carcinoma (HCC). Chemokines and those receptors is sought to be a potent chemoattractant for lymphocytes. Although CXCR3 chemokines (CXCL9, CXCL10, CXCL11) for Th1 cells, and CCR4 chemokines (CCL17, CCL22) for regulatory T (Treg) cells have been shown to play the central roles for T cell migration, the mechanism of T cell infiltration in malignant tumor tissue is not fully understood, especially in HCC. The purpose of the present study was to estimate the correlation between mRNA expression of chemokines and tumor-infiltrating lymphocytes in HCC. Further we attempted the significance of chemokine expression in tumor progression. Methods: Fresh surgical specimens were obtained from 32 HCC patients who had undergone curative partial hepatectomy in the Chiba University Hospital (Chiba, Japan). We assessed mRNA expression levels of CXCR3 and its ligands (CXCL9, CXCL10, CXCL11) for Th1 tumor infiltrating lymphocytes by real-time quantitative RT-PCR. Foxp3, CCR4 and its ligands (CCL17, CCL22) mRNA was also examined. T cell infiltration in HCC was assessed by immunohistochemistry using anti-human CD4, CD8, and Foxp3 antibody. Analysis of correlation among tumor-infiltrating lymphocyte, each chemokine mRNA, and clinicopathological features were performed. Results: Tumor infiltrating cells were seen in various degrees in HCCs. The mRNA expression of CXCR3 and CXCR3 ligands (CXCL9, CXCL10, CXCL11) in HCC were lower than non-tumorous tissues. On the other hand, mRNA of CCR4, Foxp3, and CCR4 ligands (CCL17, CCL22) in HCC expressed significantly higher than non-tumorous tissues. Immunohistochemical analysis showed that the tumor infiltrating lymphocyte predominantly considered CD8+ T lymphocytes. The number of Foxp3+ Treg cells that had infiltrated in HCC was significantly higher than non-tumorous tissues. Significant close correlations were observed between the number of total infiltrating lymphocytes in these HCC and the expression of CXCL11 mRNA. The number of infiltrating Foxp3+ Treg cells correlated with CCL17 and CCL22 mRNA expression in HCC. Further, higher gene expression of CCL22 in HCC was significantly correlated with longer disease free survival and overall survival after tumor resection. Conclusion: These results indicate that increased gene expression of CCL22 may be a major factor for Treg infiltration and that may be a predictive marker for prognosis of HCC.