Abstract
Macrophages, which are key players in the tumor microenvironment and affect the prognosis of many cancers, interact with lymphatic vessels in tumor tissue. However, the prognostic role of tumor-associated macrophages (TAM) and lymphatic vessels in human colorectal cancer (CRC) remains controversial. We investigated the prognostic role of CD68+ and CLEVER-1+ (common lymphatic endothelial and vascular endothelial receptor 1) TAMs in addition to CLEVER-1+ lymphatic vessels in 498 stage I-IV CRC patients. The molecular markers were detected by immunohistochemical (IHC) analysis. The results showed that, in early stage I CRC and in young patients (age below median, ≤67.4 years), a high number of CD68+ and CLEVER-1+ TAMs was associated with longer disease-specific survival (DSS). In early stage I CRC, high intratumoral CLEVER-1+ lymphatic vessel density (LVD) predicted a favorable prognosis, whereas the opposite pattern was observed in stage II CRC. The highest density of CLEVER-1+ lymphatic vessels was found in metastatic disease. The combination of intratumoral CLEVER-1+ lymphatic vesselhigh + CD68+ TAMlow was associated with poor DSS in stage I-IV rectal cancer. The present results indicate that the prognostic significance of intratumoral macrophages and CLEVER-1+ lymphatic vessels differs according to disease stage, reflecting the dynamic changes occurring in the tumor microenvironment during disease progression.