ABSTRACT
Macrophages are an important component of the stroma of neoplastic tissue often underestimated in conventional histologic sections. This chapter describes that tumor-associated macrophages (TAM) can interact both with the neoplastic as well as with the stromal components of tumor tissues. The percentage of TAM for each tumor is usually maintained as a relatively stable "individual" property during tumor growth and upon transplantation in syngeneic hosts. Tumor cells of different origin produce a 46-kDa protein related to platelet-derived growth factor and named vascular permeability factor or vascular endothelial growth factor. Intratumor macrophages from malignant neoplasms can be activated for tumor cytotoxicity by in vitro exposure to stimuli such as free or encapsulated IFNγ and bacterial products, though they do so less efficiently than young inflammatory phagocytes. The in vivo relevance of TAM has been approached by administering compounds that inhibit macrophage functions, by adoptively transfering macrophages, and by gene transfer.
