3-DIMENSIONAL COCULTURE OF HUMAN MONOCYTES AND MACROPHAGES WITH TUMOR-CELLS - ANALYSIS OF MACROPHAGE DIFFERENTIATION AND ACTIVATION

Here we report on an experimental system for generating TAM in vitro b y culturing human MO and MO-derived macrophages (MAC) within 3-dimensi onal multicellular tumor spheroids (MCS). MO as well as MO-derived MAC migrate into tumor spheroids and spread throughout the entire spheroi d within 16 hr. In contrast, fibroblast-spheroids were not infiltrated . The regular expression of MAC maturation-associated antigens on infi ltrating MO was suppressed within MCS of the undifferentiated bladder carcinoma line J82 with regard to carboxypeptidase M (CPM), MAX.3 anti gen and CD105. However, MAC within spheroids of highly differentiated papillary RT4 cells failed only the single antigen CD51, whereas MAC e xpressed the complete maturation-associated phenotype within nontumori genic HCV29 spheroids. Interestingly, the suppressive effect of J82 ca rcinoma cells could only be observed in 3-dimensional but not in monol ayer cultures. The J82-MCS induced suppression of CPM and MAX.3 expres sion was only seen to be operative on infiltrating blood MO: MO first differentiated for 2 days and subsequently co-cultured with J82-MCS sh owed normal expression of MAX.3 and CPM within the spheroid. Besides t he modulation of MAC phenotype, the cytokine response of intraspheroid al MAC was analyzed: upon co-culture MO secreted high IL-1 beta and IL -6 but low amounts of TNF-alpha as compared to MAC. This MO typical cy tokine pattern remained constant for up to 8 days in culture, again in dicating a disturbed MO to MAC maturation within tumor spheroids. In c onclusion, a 3-dimensional interaction with tumor cells in vitro resul ts in significant changes in the phenotype and function of the spheroi d-associated MO and MAC. (C) 1996 Wiley-Liss, Inc.