Expression of cytokeratin-19 as a marker of neoplastic progression of human prostate epithelial cells

BACKGROUND: Our earlier studies demonstrated neoplastic transformation of SV40-immortalized neonatal human prostate epithelial cells (267B1) by fractionated doses of ionizing radiation or by introduction of v-ki-ras oncogene. X-ray-treated 267B1 cells represent three different stages of neoplastic progression: nontumorigenic F3-SAC cells that acquired morphological changes and anchorage independence when treated with 2 x 2 Gy of X-rays; malignantly transformed 267B1-XR and 267B1-SXR cells that received 2-Gy doses to a total of 30 Gy. We also reported alterations in cell size, morphology, actin stress fibers, and levels of actin-binding proteins in these transformed human prostate cells. METHODS: We analyzed intermediate filament-nuclear matrix (IF-NM) protein expression in the various 267B1 cells as a consequence of neoplastic progression by two-dimensional gel electrophoresis and immunofluorescence. RESULTS: Our present study revealed that the 267B1 cells experienced progressive changes in their intermediate filament protein composition during the process of neoplastic conversion, achieved either by X-rays or by ras-oncogene. In particular, we observed a stepwise downregulation of cytokeratin-19 in these in vitro transformed 267B1 cells. CONCLUSIONS: Our data suggest that loss of expression of cytokeratin-19 accompanied the morphological alterations associated with in vitro neoplastic transformation of SV40-immortalized prostate epithelial cells.