Several years ago, the presence of macrophages in the tumor microenvironment was thought to be an inflammatory response to kill the
cancer cells. Now, this is clear that the inflammatory cells that exit blood vessels and migrate to the
tumor tissue play an important role in
cancer progression. Various cells present in the tumor microenvironment enhance
cancer growth and invasiveness by secretion of
tumor-enhancing products. That is why
tumors should not be treated as only aggregates of
cancer cells but as separate structures. Macrophages form a major component of the inflammatory infiltration in
tumors, where they are termed tumor-associated macrophages (TAMs). To the best of our knowledge, up-to-date there were no studies on tumor associated macrophages and the role of the tumor microenvironment in
tumor invasion/
metastasis in dogs. This is the first study performed to asses if the number of TAMs and expression of MCSF-R (macrophages
colony stimulating factor receptor) and CD14 (LPS co-receptor) are associated with the grade of
tumor malignancy and its ability to metastasize. We have performed immunohistochemical analysis of 50 canine mammary
adenocarcinomas of various grade of
malignancy (1st, 2nd, 3rd) and
tumors that gave local or distant
metastases. The results indicate that in dogs, similarly to humans and mice, the number of tumor associated macrophages is related to the
cancer ability to metastasize. Our results also indicate that the expression of MCSF-R and, what is particularly new finding, CD14 is associated with
tumor malignancy and its ability to metastasize. Hence, these molecules play a role in
tumor progression,
metastasis and microenvironment interactions. These results show that in dogs we should treat the
tumor as a whole organ rather than just try to eliminate the
cancer cells.