Microsatellite unstable colorectal cancers are associated with increased CD1a- and CD83-positive dendritic cell infiltration

Microsatellite instability (MSI) is characterized by a highly immunogenic tumor phenotype and abundant lymphocytic infiltrates. The aim of this study was to investigate the association between four immunohistochemically determined classes of dendritic cells (DC) with microsatellite instability status of 258 colorectal cancer (CRC) patients and to explore the possible role of those cells as prognostic factors for survival. We observed a distinct infiltration pattern of DCs both in tumor stroma (TS) and invasive front (IF), with DCs significantly prevailing in the IF (p < 0.0001). MSI cancer biopsies showed significantly higher infiltration of CD1a + and CD83+ DCs in the TS and IF compared to microsatellite stable CRCs. Survival analysis revealed that higher CD1a + and CD83+ DC numbers both in TS and IF correlated with longer survival of the patients after surgical therapy (p < 0.05, Log rank test). Cox multivariate analysis showed that lower infiltration with CD1a + DCs in TS (p = 0.039) and CD83+ DCs in IF (p = 0.022) was an independent prognostic factor for unfavorable outcome for CRC patients. The results of our study suggest that the immunohistochemically determined CD1a + and CD83+ DCs could be used as a feature of microsatellite instability and could be further explored as prognostic markers for patients’ outcome.