N;-3 and n;-6 polyunsaturated fatty acids induce cytostasis in human urothelial cells independent of p53 gene function

The role of long-chain polyunsaturated fatty acids (PUFA) in the etiopathology and treatment of cancer is poorly understood. We have studied the effects of n;-3 and n;-6 PUFA on the proliferation and survival of normal human uroepithelial (NHU) cells, cells with disabled p53 function after stable transfection with the human papillomavirus 16 (HPV16) E6 gene (HU-E6), and p53-disabled cells that had passed through crisis and acquired karyotypic abnormalities (HU-E6P). The n;-3 and n;-6 PUFA had distinct reversible antiproliferative and irreversible cytostatic effects according to concentration and exposure time. The reversible antiproliferative effect was partly due to the production of lipoxygenase metabolites. NHU and HU-E6 cells were equally sensitive to n;-3 and n;-6 PUFA, but HU-E6P cells were more resistant to both the antiproliferative and cytostatic effects. Cytostatic concentrations of n;-3 and n;-6 PUFA did not induce apoptosis, but caused permanent growth arrest ("interphase" or "reproductive" cell death) and mRNA levels for genes involved in cell cycle control (p21, p16, p27, cdk1, cdk2, and cdk4) were not altered. Neither n;-3 nor n;-6 PUFA promoted acquisition of karyotypic abnormalities in HU-E6 cells, suggesting that n;-3 and n;-6 PUFA do not cause genotoxic damage.In conclusion, our studies show that the antiproliferative and cytostatic effects of n;-3 and n;-6 PUFA are not dependent on p53 function and, further, that transformation results in a loss of sensitivity to n;-3 and n;-6 PUFA-mediated growth inhibition.