A heterologous 3-D coculture model of breast tumor cells and fibroblasts to study tumor-associated fibroblast differentiation

The objective of our study was to establish spheroid cocultures as a valid 3-D in vitro model mimicking tumor-fibroblast interactions in scirrhous bre ast tumors. The experimental setup was designed to verify if in cocultures (a) adherence and migration reflect the invasive potential of breast tumor cells, (b) breast tumor cells induce tumor-associated fibroblast differenti ation, and (c) tumor-derived fibroblasts better reflect the in vivo situati on than normal skin fibroblasts. Only one (SK-BR-3) out of five tumor cell types showed extensive fibroblast infiltration, MCF-7 cells frequently inva ded fibroblast spheroids; BT474, T47D, and ZR-75-1 were noninvasive. While tumor cell invasion was independent of fibroblast origin, tumor-associated myofibroblast differentiation defined by alpha -SMA expression was demonstr ated for tumor-derived but not normal skin fibroblasts in coculture indicat ing that (a) tumor cell invasion and myofibroblast differentiation are auto nomous processes and (b) cocultures with tumor-derived fibroblasts resemble advanced stages of desmoplastic carcinomas while cocultures with normal sk in fibroblasts rather reflect the early tumor development. The latter is al so implied by fibroblast-associated alterations in tumor cell morphology an d ECM distribution in the system. By using RNA arbitrarily primed PCR and c ells isolated from cocultures by fluorescence-activated and magnetic cell s eparation, peripheral myelin protein PMP22/SR13 has been identified as a no vel candidate with potential relevance in the interaction between tumor cel l and normal fibroblast since PMP22 mRNA was significantly reduced in norma l skin fibroblasts in coculture with BT474 cells. (C) 2001 Academic Press.