HUMAN-MALIGNANT ASTROCYTES EXPRESS MACROPHAGE PHENOTYPE

Six well-characterized specimens of cultured astrocytoma cells were in vestigated with a panel of macrophage markers. Our results show that t he macrophage markers OKM-1(CD11b), OKM5(CD36), EBM11(CD68), HAM56, Fa ctor 13, alpha-1-antichymotrypsin, alpha-1-antitrypsin, ferritin and l ysozyme are clearly reactive to neoplastic astrocytes whereas astrocyt es in normal brain specimens are not reactive. In order to obtain furt her confirmation concerning the reactivity of tumor cells in vivo, we simultaneously measured by flow cytometric analysis DNA content and HA M56 immunoreactivity in a freshly obtained tumor specimen. In this exp eriment we found a marked reactivity of aneuploid cells to HAM56. The macrophage phenotype of malignant astrocytes may reflect a similarity in functions of these cells and tumor-associated macrophages which pro mote tumor growth via the production of growth factors and angiogenic factors. Furthermore, our findings implicate that demonstration of mac rophages within malignant astrocytomas by using macrophage-specific an tibodies must be cautiously considered.