Integrating macrophages into organotypic co-cultures: a 3D in vitro model to study tumor-associated macrophages.
Tumor progression is controlled by signals from cellular and extra-cellular microenvironment including stromal cells and the extracellular matrix. Consequently, three-dimensional in vitro tumor models are essential to study the interaction of tumor cells with their microenvironment appropriately in a biologically relevant manner. We have previously used organotypic co-cultures to analyze the malignant growth of human squamous cell carcinoma (SCC) cell lines on a stromal equivalent in vitro. In this model, SCC cell lines are grown on a collagen-I gel containing fibroblasts. Since macrophages play a critical role in the progression of many tumor types, we now have expanded this model by integrating macrophages into the collagen gel of these organotypic tumor co-cultures. This model was established as a murine and a human system of skin SCCs. The effect of macrophages on tumor progression depends on their polarization. We demonstrate that macrophage polarization in organotypic co-cultures can be modulated towards and M1 or an M2 phenotype by adding recombinant IFN-γ and LPS or IL-4 respectively to the growth medium. IL-4 stimulation of macrophage-containing cultures resulted in enhanced tumor cell invasion evidenced by degradation of the basement membrane, enhanced collagenolytic activity and increased MMP-2 and MMP-9. Interestingly, extended co-culture with tumor cells for three weeks resulted in spontaneous M2 polarization of macrophages without IL-4 treatment. Thus, we demonstrate that macrophages can be successfully integrated into organotypic co-cultures of murine or human skin SCCs and that this model can be exploited to analyze macrophage activation towards a tumor supporting phenotype.
Group Tumor and Microenvironment, German Cancer Research Center (DKFZ), Heidelberg, Germany.
Nina
N
Linde
Claudia M
CM
Gutschalk
Claudia
C
Hoffmann
Dilan
D
Yilmaz
Margareta M
MM
Mueller
D000818:Animals; D002294:Carcinoma, Squamous Cell / Q000473:pathology; D018929:Cell Culture Techniques / Q000379:methods*; D045744:Cell Line, Tumor; D018920:Coculture Techniques; D006801:Humans; D015847:Interleukin-4 / Q000494:pharmacology; D008264:Macrophages / Q000187:drug effects / Q000473:pathology*; D051379:Mice; D009361:Neoplasm Invasiveness; D046509:Tissue Culture Techniques / Q000379:methods*; D014407:Tumor Cells, Cultured
D015847:Interleukin-4