The relationships between serum cytokine levels and tumor infiltrating immune cells and their clinical significance in colorectal cancer.

Increased inflammatory cell infiltration correlates to improved survival in colorectal cancer (CRC). Development and progression of CRC is associated with alterations in serum cytokine levels but their significance is not well defined. In this study, we investigated the relationships between the serum levels of 13 cytokines and the densities of eight types of tumor infiltrating inflammatory cells and their impact on disease-free survival (DFS), cancer-specific survival (CSS) and overall survival (OS) in a prospectively recruited group of 147 CRC patients. There were strong positive correlations between the serum concentrations of different cytokines, as well as between the different types of tumor infiltrating immune cells, whereas the associations between serum cytokines and tumor infiltrating immune cells were generally weak. High serum IL-12 levels associated with increased densities of peritumoral CD8(+) T cells, intraepithelial CD3(+) T cells and intratumoral neutrophils, while high serum CCL4 levels associated with increased densities of peritumoral CD68(+) cells. In multivariate survival models, increased infiltration of intraepithelial CD3(+) T cells and increased serum CCL4 associated with improved DFS, whereas higher intratumoral CD83(+) dendritic cell density and increased serum interferon gamma levels associated with improved CSS and OS. Also high density of peritumoral CD3(+) T cells associated with improved CSS. In conclusion, serum cytokines and tumor infiltrating immune cells in CRC represent entities with high intragroup correlations but relatively weak intergroup correlations. The results suggest that tumor infiltrating CD3(+) T cells, CD83(+) dendritic cells, serum CCL4 and serum interferon gamma represent relevant markers of disease outcome.