Modulation of prostate cancer cell gene expression by cell-to-cell contact with bone marrow stromal cells or osteoblasts

After prostate cancer cells (PCa) arrive in bone, interactions with cells that include long bone osteoblasts (LBOB) and bone marrow stromal cells (BMSC) lead to metastasis formation. The effect of heterotypic cell-cell contact between PCa cells and BMSC or LBOB on PCa cell gene expression is poorly understood. To establish the role of heterotypic contact in bone metastasis formation, we mixed and co-cultured PC3 cells with rat BMSC, LBOB, or human prostate stromal cells (PS15). PC3 cells were then re-isolated for gene array analysis, and imaged using in situ hybridization to confirm that heterotypic contact regulates gene expression. The gene expression was examined using focused gene arrays containing 96 each of tumor metastasis genes or osteogenesis genes. A total of 18 out of 192 genes in PC3 cells were found to be under or over expressed subsequent to heterotypic contact with BMSC when analyzed. A total of 15 genes out of 192 were regulated in co-culture with LBOB, and 19 genes with PS15. Only two genes, uPA and Collagen III, were regulated by contact with BMSC or LBOB (both are bone derived cells), but not by contact with PS15. The relationship between cell-cell contact and uPA expression was further explored by varying cell ratios in co-culture. uPA over-expression in PC3 was related to the BMSC:PC3 ratio, and was maximum at a 10:1 ratio, where most PC3 cells would be in contact with BMSC, as predicted by a theoretical model of heterotypic contact. In situ staining of micropatterned PC3 and BMSC cells showed that uPA over-expression localizes to regions of heterotypic cell-cell contact. Taken together, our results suggest that heterotypic cell-to-cell contact between PC3 and BMSC proportionally enhances gene expression for uPA, providing a mechanism for localized control of invasiveness.