Inhibition of tumor cell proliferation and motility by fibroblasts is both contact and soluble factor dependent

Significance Normal microenvironments can restrict cancer development and progression. Inhibition of tumor cell growth and motility by normal fibroblasts is one measurable manifestation of this multicomponential control. Here we show that inhibition withstands formalin fixation and can be augmented by the addition of conditioned medium derived from live cultures of tumor cells confronting the stromal fibroblasts. We describe a number of molecules involved in this process. This study lays the foundation for further mechanistic studies of this important phenomenon and its contribution to possible dormancy and the tumor’s resistance to therapy. Normal human and murine fibroblasts can inhibit proliferation of tumor cells when cocultured in vitro. The inhibitory capacity varies depending on the donor and the site of origin of the fibroblast. We showed previously that effective inhibition requires formation of a morphologically intact fibroblast monolayer before seeding of the tumor cells. Here we show that inhibition is extended to motility of tumor cells and we dissect the factors responsible for these inhibitory functions. We find that inhibition is due to two different sets of molecules: ( i ) the extracellular matrix (ECM) and other surface proteins of the fibroblasts, which are responsible for contact-dependent inhibition of tumor cell proliferation; and ( ii ) soluble factors secreted by fibroblasts when confronted with tumor cells (confronted conditioned media, CCM) contribute to inhibition of tumor cell proliferation and motility. However, conditioned media (CM) obtained from fibroblasts alone (nonconfronted conditioned media, NCM) did not inhibit tumor cell proliferation and motility. In addition, quantitative PCR (Q-PCR) data show up-regulation of proinflammatory genes. Moreover, comparison of CCM and NCM with an antibody array for 507 different soluble human proteins revealed differential expression of growth differentiation factor 15, dickkopf-related protein 1, endothelial-monocyte-activating polypeptide II, ectodysplasin A2, Galectin-3, chemokine (C-X-C motif) ligand 2, Nidogen1, urokinase, and matrix metalloproteinase 3.