FUNCTIONAL EXPRESSION OF SV40 IN NORMAL HUMAN PROSTATIC EPITHELIAL AND FIBROBLASTIC CELLS - DIFFERENTIATION PATTERN OF NONTUMORIGENIC CELL-LINES

To study mesenchymal-epithelial interactions associated with the norma l and pathological human prostate, we have developed a model of well d ifferentiated human prostate epithelial and fibroblastic cells. Normal human prostatic cells, either of epithelial or fibroblastic origins w ere successfully transfected with SV40 and strains with extended lifes pan were selected until the crisis was reached, within 20 and 30 passa ges for the epithelial and fibroblastic cells, respectively. Only a fe w clones emerged from the crisis: PNT1A (Cussenot et al: J Urol 143: 8 81-886, 1991), PNT1B and PNT2 epithelial cell lines. Successful immort alisation was achieved only with SV40 expressing both large T and smal l t oncogenes, while attempts to immortalise with a vector expressing SV40 large T alone have given a few strains showing no extended lifesp an and no cells which overcame the crisis. A PNT2 subclone named PNT2- LSD which developed spontaneously (less serum dependent) was selected, characterised and included in the analysed series. The epithelial cel l lines displayed a differentiation pattern which has been classified as follows (from high to low): PNT2>PNT2-LSD>PNT1A>PNT1B. Differentiat ion features studied were (i) the colony-forming ability of the PNT2 a nd PNT2-LSD compared to PNT1A and PNT1B, (ii) their respective doublin g time of 39, 29, 30 and 28 hours, (iii) their decreasing serum depend ency, (iv) the expression of cytokeratin 19 (a feature of well differe ntiated luminal cells of the glandular prostate) for PNT2 and PNT2-LSD . Furthermore, the mesenchymal derived pflsv1 cells were confirmed to be of fibroblastic nature. None of the cell lines analysed showed any tumourigenicity in nude mice over a period of 12 months. Serum depriva tion and direct steroid withdrawal during the culture triggered cell d eath by apoptosis, an event which could be overcome by EGF stimulation , particularly for the well differentiated PNT2 cells. This interestin g characteristic, which is similar to the high apoptotic rate observed ipl vivo for normal prostate, particularly after castration should le ad, together with the other properties of these cell lines, to a bette r understanding of the biology of the different cell compartments invo lved in the progression of prostate towards neoplasia.