Background: The role of tumor associated macrophages (TAMs) in tumor angiogenesis and inflammation and the interactions between TAMs and tumor cells as well as lymphocytes appear to be critical factors in the development and progression of cancer.
Patients and methods: Carcinomas of the gastrointestinal tract have been analysed by tissue microarrays. TAMs and vessels were characterized by immunohistochemistry using the antibodies PG-M1, KP1, MRP8, MRP14, MRP8/14 and CD31, CD34, respectively.
Results: The number of all macrophages was significantly higher and lymphocyte densities were lower in tumor tissues than in tumor-free tissues. The MRP-antibodies identified a minority population of macrophages and a low numbers of these macrophages tended to occur in more advanced cancers. There was a positive correlation between the number of macrophages and the number of microvessels in all tumors, but no correlation between macrophages and vessel counts in tumor-free tissues.
Conclusion: The results indicated a suppressed immune response towards the tumors. The observed common characteristics regarding macrophage attraction, lymphocyte suppression and microvessel density suggested that these mechanisms are regulated similarly in all carcinomas of the GI-tract.