Abstract
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.
Highlights
The role of long-chain polyunsaturated fatty acids (PUFA) in the etiopathology and treatment of cancer is poorly understood
Whether the antiproliferative and irreversible cytostatic effects of n–3 and n–6 PUFA in normal human urothelial (NHU) cells were dependent on functional p53 protein, we investigated whether ablation of p53 function, a major event in urothelial carcinogenesis [12, 13], would alter response or sensitivity to n –3 and n–6 PUFA
NHU cells exposed to 100 m linoleic acid (LA), ␥-linolenic acid (GLA), eicosapentaenoic acid (EPA), or Docosahexaenoic acid (DHA) for 72 h were not able to reestablish proliferation when replenished with growth medium devoid of fatty acids
Summary
The role of long-chain polyunsaturated fatty acids (PUFA) in the etiopathology and treatment of cancer is poorly understood. Long-chain polyunsaturated fatty acids (PUFA) of both n–3 and n–6 types can inhibit cell division, cause cell cycle arrest, and induce cell death in malignant epithelial cells of various tissue origins in vitro [1,2,3,4]. We have shown that n–3 and n–6 PUFA are growth inhibitory to proliferating NHU cells, whereas saturated stearic acid had no antiproliferative effect [7]. We suggested that these PUFA have a general antiproliferative effect on rapidly dividing cells, rather than showing any selective effect on neoplastically transformed cells. Whether the antiproliferative and irreversible cytostatic effects of n–3 and n–6 PUFA in NHU cells were dependent on functional p53 protein, we investigated whether ablation of p53 function, a major event in urothelial carcinogenesis [12, 13], would alter response or sensitivity to n –3 and n–6 PUFA
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