A NOVEL COCULTURE TECHNIQUE DEMONSTRATES THAT NORMAL HUMAN PROSTATIC FIBROBLASTS CONTRIBUTE TO TUMOR-FORMATION OF LNCAP CELLS BY RETARDING CELL-DEATH

The microenvironment influences the progression of an epithelial malig nancy. To examine the effect of fibroblasts on epithelial cells by dir ect cell-cell contact in vitro, a coculture system was designed to ass ess cell death and proliferation of two cell populations when grown to gether. We used a green fluorescent dye to stain fibroblasts and disti nguish them from unstained epithelial cells by a flow cytometer, We sh ow that tumor cell death is 5-fold less when cocultured with normal hu man prostatic fibroblasts than when cultured alone. In contrast, proli feration of tumor cells was similar when cocultured with normal human prostatic fibroblasts or when grown alone. The reduction in tumor cell death during coculture appears to play a significant role in promotin g tumor formation, Combination of prostatic fibroblasts with LNCaP xen ografts formed large tumors at a high frequency with a low apoptotic i ndex in vivo, whereas, LNCaP xenografts alone formed small infrequent tumors with a high apoptotic index. Therefore, prostatic fibroblasts p romote tumor formation by retarding the apoptotic pathways in tumor ce lls.