Plasmacytoid dendritic cells (pDCs) are present in various primary and metastatic human neoplasms; however, their clinical significance in hepatocellular carcinoma (HCC) is unclear. In this study, we investigated the distribution, prognostic value, and potential function of pDCs in HCC patients undergoing curative resection. We performed immunohistochemical analyses of whole tumor sections from 224 patients to assess the expression of BDCA2, CD3, CD4, CD8, Foxp3, granzyme B, IL-17, and CD34. The findings were validated using tissue microarrays from another two independent cohorts totaling 841 HCC patients undergoing curative resection. Our results demonstrated that high numbers of BDCA2+ pDCs within tumors correlated with high alpha-fetoprotein levels, greater vascular invasion, advanced tumor-node-metastasis stage, shorter overall survival, and a higher recurrence rate. However, patient outcomes were not associated with pDCs in peritumoral stromal or nontumor tissues. Furthermore, an increase in intratumoral pDCs was associated with increased intratumoral infiltration of Foxp3+ regulatory T cells and IL-17-producing cells and correlated with tumor vascular density. Univariate and multivariate analyses revealed that the presence of intratumoral pDCs alone or in combination with regulatory T and/or IL-17-producing cells was an independent predictor of time to recurrence and overall survival. In conclusion, our study demonstrated that intratumoral infiltration by pDCs is a novel indicator for poor prognosis in patients with HCC, possibly through the induction of an immune tolerogenic and inflammatory tumor microenvironment comprising regulatory T and IL-17-producing cells. An assessment of the combination of these cells represents a superior predictor of patient outcome.
Keywords: Hepatocellular carcinoma; IL-17; Plasmacytoid dendritic cells; Prognosis; Treg cells.