In vitro dorsal root ganglia and human prostate cell line interaction: redefining perineural invasion in prostate cancer.
Little is understood regarding mechanisms of perineural invasion in prostate cancer progression. We present a novel model system and data that indicate perineural invasion is an active, specific, and reciprocal interaction between nerves and prostate cancer cells. Mouse dorsal root ganglia (DRG) and human prostate cancer cells (Du-145, LNCaP, PC3) and stromal cells (HTS-40F) were co-cultured in Matrigel matrix. Control cultures consisted of prostate cancer and stromal cells only and DRG only. Neurite outgrowth, cell colony growth, neurite-colony contact, and retrograde extension were quantitated with dark phase microscopy and image analysis (Optimas 6.1). Directional outgrowth of neurites was observed projecting into DU-145 colonies within 24 hr of co-culture. Cultures with the greatest number of DU-145 cells recruited significantly more neurites and established contact earlier, indicating this process was cell-seeding density dependent. Once neurite/DU-145 cell contact was established neurite growth diminished, suggesting an active neurite recruitment by DU-145 cells. Subsequent to neurite contact, DU-145 cells migrated along neurites in a retrograde fashion into the nerve/ganglion of origin (retrograde extension) establishing perineural invasion. In addition to perineural invasion, DU-145 colony growth was elevated in DRG co-cultures relative to DU-145-only control cell cultures. Similarly, the degree of neurite outgrowth was elevated in DRG-cell co-cultures relative to DRG-only control cultures. The same observations were made with LNCaP and PC3 cells, but interactions between stromal cells and nerves were not found. This study shows the utility of the prostate cancer/DRG in vitro system to study specific mechanism of prostate cancer cell-nerve interaction. Moreover, these data suggest that perineural invasion mechanisms involve active and reciprocal interactions between carcinoma cells and adjacent nerve/ganglions in prostate cancer progression.