Epidermal growth factor receptor-mediated autocrine and paracrine stimulation of human transitional cell carcinoma

Stromal-epithelial interactions may play a key role in tumor growth and metastasis. We have established a model to study the cellular and molecular basis of this paracrine interaction both in vivo and in vitro using a human transitional cell carcinoma cell line (WH). s.c. coinoculation of 1 x 10(6) WH cells with 1 x 10(6) nontumorigenic fetal rat urogenital sinus mesenchymal (rUGM) cells in athymic mice accelerated carcinoma growth 20 times faster than isolated WH cell inoculations and 4 times faster than coinoculations of the same number of NIH-3T3 or human bladder fibroblasts. Characterization of these chimeric tumors with immunohistochemical and DNA dot-blot analyses documented their predominantly human component. To evaluate the underlying mechanisms involved in this paracrine-mediated in vivo tumor growth acceleration, Northern analyses for growth factors (GFs) and extracellular matrix (ECM) expression in the different cell lines, as well as in vitro mitogenic assays, were performed. Northern analysis revealed basic fibroblast growth factor, transforming growth factor alpha, and epidermal growth factor receptor expression by WH cells but not rUGM cells; ECM components (fibronectin and collagens I and IV) were expressed only in the fibroblast cell lines. Cell type-specific paracrine growth factors are produced by cultured stromal and epithelial cells with a 2-3-fold bidirectional increase in WH and rUGM cell growth when cultured with reciprocal cell-type conditioned medium. An autocrine growth loop was observed for WH but not rUGM cells. WH cell growth is stimulated in vitro by low concentrations of transforming growth factor alpha and epidermal growth factor, while rUGM cell growth is stimulated 3-fold by basic fibroblast growth factor. Antiepidermal growth factor receptor antibodies completely inhibited autocrine and paracrine pathways stimulating WH cell growth, while anti-basic fibroblast growth factor antibodies had no inhibitory effect. These observations suggest that autocrine and paracrine growth factor stimulation of WH bladder carcinoma cell growth is most likely mediated by an epidermal growth factor receptor-related pathway. The predominant expression of ECM by fibroblasts in this model suggests that stromal cell ECM components may modulate tumor cell growth and angiogenesis possibly through mechanisms involving cellular adhesion, chemotaxis, or growth factor action.