Circulating dendritic cells in early and advanced cancer patients: diminished percent in the metastatic disease

Despite the well demonstrated fundamental role of dendritic cells (DC) in generating antitumor immunity in experimental conditions, to date there are only few preliminary studies which investigate the percent of DC in the peripheral blood of cancer patients. Several cell surface markers have now been described which are specific to cultured DC, however their expression in vivo is still controversial. Recently, however, two DC subsets, consisting of immature and mature DC, have been shown to be present in peripheral blood, which can be recognized as CD123+ and CD11c+ cells, respectively. On this basis, we decided to investigate the presence of both mature and immature DC in the peripheral blood of early or advanced cancer patients. The study included 40 solid tumor patients, 18 of whom had a locally limited disease, while the other 22 showed distant organ metastases. CD123+ and CD11c+ cells were detected by FACS using monoclonal antibodies, and expressed as the percent of total leukocytes. The control group consisted of 50 healthy subjects. The mean percent of both CD123+ and CD11c+ cells was significantly lower in cancer patients than in controls. Moreover, the mean percent of both DC subsets was significantly lower in metastatic patients than in the non-metastatic ones. This study, demonstrating significantly lower percents of both immature and mature DC in the peripheral blood of cancer patients, particularly in those with distant organ metastases, suggests that DC deficiency may play a role in inducing cancer-related immunosuppression. Therefore, the demonstration of a diminished percent of DC in peripheral blood may represent a new interesting biological marker predicting a poor prognosis in human neoplasms, as with lymphocytopenia, the unfavourable prognostic significance of which has been well demonstrated.