Cyclic hydroxamic acid inhibitors of prostate cancer cell growth: selectivity and structure activity relationships.
BACKGROUND: Clinical symptoms of prostatitis, prostatodynia, and benign prostatic hyperplasia are relieved by the pollen extract cernilton, and the water-soluble fraction of this extract selectively inhibits growth of some prostate cancer cells. A cyclic hydroxamic acid, DIBOA, has been isolated from this extract and mimics its cell growth-inhibitory properties, but the specificity of DIBOA for inhibition of prostate cell growth has not been reported. METHODS: The in vitro growth inhibitory effects of DIBOA and nine structurally related compounds on DU-145 prostate cancer cells, MCF-7 breast cancer cells, and COS-7 monkey kidney cells were determined by treatment of the cells with various concentrations of the compounds for 2-6 days. RESULTS: The compounds exhibited a wide range of potencies, but none of them exhibited selective inhibition of DU-145 cell growth. MCF-7 cells were more sensitive to DIBOA than either DU-145 cells or COS-7 cells. 3,4-dihydroquinoline-2(1H)-one, compound (4), and 1-hydroxy-6-chloro-3,4-dihydroquinolin-2(1H)-one, compound (7), selectively inhibited MCF-7 cell growth at a concentration of 10 micrograms/ml. 1-hydroxy-3,4-dihydroquinolin-2(1H)-one, compound (3), and compound 7 were the most potent inhibitors of DU-145 cell growth. Treatment of DU-145 cells with 3 (100 micrograms/ml) substantially decreased the number of viable cells within 2 days, and no viable cells remained in the culture by day 4. CONCLUSIONS: It is unlikely that DIBOA, compound (1), is responsible for the selective growth inhibition of prostate cancer cells by the water-soluble fraction of the pollen extract cernilton. Cell morphology results indicate that the growth-inhibitory effects of DIBOA and structurally related agents on DU-145 cells are due to their ability to cause cell death.