Mutations in the coding region of the hypoxanthine (guanine) phosphoribosyltransferase (HPRT) gene of Chinese hamster V-79 cells were examined after exposure ofthe cells to a high cytotoxic dose (0.48 pM; 35% survival) and a low noncytotoxic dose (0.04 ,M; 100% survival) of the ultimate carcinogen (+)-7R,8S-dihydroxy-9S, 10R-epoxy-7,8,9,10-

Earlier studies from our laboratories characterized the mutation profile of the optically active (+)-7R,8S-dihydroxy-9S,10R-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene [(+)-BPDE--the ultimate carcinogenic metabolite of benzo[a]pyrene] in the coding region of the hypoxanthine (guanine) phosphoribosyltransferase (HPRT) gene of Chinese hamster V-79 cells. In the present study, we evaluated the mutation profile of (-)-7S,8R-dihydroxy-9R, 10S-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene [(-)-BPDE-a weakly carcinogenic or inactive enantiomer] and compared its mutation profile with that of (+)-BPDE. In both diol epoxide enantiomers, the benzylic 7-hydroxy group and epoxide oxygen are trans. The mutation frequency for V-79 cells treated with DMSO vehicle or with a low, non-cytotoxic dose (0.5 microM) or a high cytotoxic dose (2.0 microM) of (-)-BPDE was 1, 25 or 185 8-azaguanine-resistant colonies/10(5) survivors, respectively. Independent 8-azaguanine-resistant clones were isolated, and complementary DNAs were prepared by reverse transcription. The coding region of the HPRT gene was amplified by the polymerase chain reaction and sequenced. Altogether, 92 (-)-BPDE-induced mutant clones were examined. At both doses, base substitutions were the most prevalent mutations observed (present in approximately 7% of the mutant clones), followed by exon deletions (present in approximately 22% of the mutant clones) and frame shift mutations (present in approximately 6% of the mutant clones) in the cDNAs analyzed. At the high cytotoxic dose, 5 out of 36 base substitutions occurred at AT base pairs (14%) and 31 at GC base pairs (86%). At the low, non-cytotoxic dose, 7 out of 34 base substitutions were at AT base pairs (21%) and 27 were at GC base pairs (79%). Although there was a trend towards an increase in the proportion of mutations at AT base pairs when the dose of (-)-BPDE was decreased, this trend was not statistically significant. The data also indicated no dose-dependent differences in the kinds of base substitutions or exon deletions in cDNAs induced by (-)-BPDE. Ninety-one per cent of the (-)-BPDE-induced mutations that occurred at guanine were on the non-transcribed strand of DNA and 9% were on the transcribed strand. In contrast to these results, 50% of the (-)-BPDE-induced mutations that occurred at adenine were on the transcribed strand and 50% on the non-transcribed strand.(ABSTRACT TRUNCATED AT 400 WORDS)

Abstract. Curcumin is a non-nutritive yellow pigment found in the spice turmeric, which is derived from the rhizome of the plant Curcuma longa Linn. Six cyclohexanone analogues of curcumin (A 1 -A 6 ) were investigated for their effects on growth and apoptosis in PC-3 human prostate cancer cells. The ability of these compounds to inhibit NF-κB activity in PC-3 cells was also determined. Five out of the six curcumin analogues (A 2 -A 6 ) had stronger inhibitory effects compared to curcumin on the growth of cultured PC-3 cells. Compounds A 2 -A 6 also had stronger stimulatory effects on apoptosis in PC-3 cells than curcumin, and these curcumin analogues more potently inhibited NF-κB activity than curcumin. The inhibitory effects of these compounds on NF-κB activity correlated with their effects on growth inhibition and apoptosis stimulation in PC-3 cells. The results of the present study provide a rationale for in vivo studies with A 2 -A 6 using suitable animal models of prostate cancer. IntroductionCurcumin is a non-nutritive yellow pigment found in the spice turmeric, which is derived from the rhizome of the plant Curcuma longa Linn. Curcumin lacks toxicity in humans (1), and extensive research over several decades has revealed that curcumin possesses anticancer, anti-inflammatory, antioxidant, antiviral and anti-bacterial activities (2,3). Curcumin suppressed cell proliferation or induced apoptosis in cultured prostate cancer cells and other types of cancer cells (4-10). Curcumin also inhibited prostate carcinogenesis (11). Studies from our laboratory and those of other authors have demonstrated enhanced anticancer activities of curcumin when combined with other anticancer agents (12-14). Findings of earlier studies showed that curcumin exerts a wide range of anticancer effects by modulating a diversity of signaling pathways, including nuclear factor-κB (NF-κB) and other pathways (15)(16)(17)(18)(19)(20). Curcumin has entered clinical trials for certain types of human cancer (21-23). However, the clinical efficacy of curcumin is limited, which is likely to be due to its low bioavailability (21-23). It was suggested that the β-diketone moiety of curcumin causes instability and poor metabolic properties (24-26). Enhanced stability was found in curcumin analogues by deleting the β-diketone moiety of the molecule (27). Recently, it was demonstrated that the cyclohexanone analogues of curcumin have enhanced stability in biological medium compared to curcumin (28). The cyclohexanone-containing curcumin analogue 2,6-bisp[(3-methoxy-4-hydroxyphenyl)methylene)]-cyclohexanone was found to be more potent than curcumin for inhibiting NF-κB in human breast cancer cells in vitro (29).In an earlier study, we synthesized a series of cyclohexanone curcumin analogues and determined their inhibitory effect on the activity of aldose reductase (30). In the present study, we investigated the effects of these curcumin analogues on the growth and apoptosis of human prostate cancer PC-3 cells. We also determined the inhibitory effect ...

The cancer epigenome is characterized by global DNA methylation and chromatin changes, such as the hypermethylation of specific CpG island promoters. Epigenetic agents like DNA methyltransferase or histone deacetylase inhibitors induce phenotype changes by reactivation of epigenetically silenced tumor suppressor genes. Despite initial promise in hematologic malignancies, epigenetic agents have not shown significant efficacy as monotherapy against solid tumors. Recent trials showed that epigenetic agents exert favorable modifier effects when combined with chemotherapy, hormonal therapy, or other epigenetic agents. Due to the novel nature of their mechanism, it is important to reconsider the optimal patient selection, drug regimen, study design, and outcome measures when pursuing future trials in order to discover the full potential of this new therapeutic modality.