Association of Serum Carotenoids and Retinoids with Intraprostatic Inflammation in Men without Prostate Cancer or Clinical Indication for Biopsy in the Placebo Arm of the Prostate Cancer Prevention Trial.

Non-supplemental carotenoids and retinol may potentiate antioxidant and anti-inflammatory mechanisms. Chronic intraprostatic inflammation is linked to prostate carcinogenesis. We investigated the association of circulating carotenoids and retinol with intraprostatic inflammation in benign tissue. We included 235 men from the Prostate Cancer Prevention Trial placebo arm who had a negative end-of-study biopsy, most (92.8%) done without clinical indication. α-carotene, ß-carotene, ß-cryptoxanthin, lycopene, and retinol were assessed by high-performance liquid chromatography using pooled year 1 and 4 serum. Presence and extent of intraprostatic inflammation in benign tissue was assessed in 3 (of 6-10) biopsy cores. Logistic (any core with inflammation vs none) and polytomous logistic (some or all cores with inflammation vs none) regression was used to estimate odds ratios (OR) and 95% confidence intervals (CI) of intraprostatic inflammation by concentration tertile adjusting for age, race, prostate cancer family history, and serum cholesterol. None of the carotenoids or retinol was associated with intraprostatic inflammation, except ß-cryptoxanthin, which appeared to be positively associated with any core with inflammation [vs none, T2: OR (95% CI) = 2.67 (1.19, 5.99); T3: 1.80 (0.84, 3.82), P-trend = 0.12]. These findings suggest that common circulating carotenoids and retinol are not useful dietary intervention targets for preventing prostate cancer via modulating intraprostatic inflammation.

Selenium and Sex Steroid Hormones in a U.S. Nationally Representative Sample of Men: A Role for the Link between Selenium and Estradiol in Prostate Carcinogenesis?

BACKGROUND: Given the recent findings from pooled studies about a potential inverse association between selenium levels and prostate cancer risk, this cross-sectional study aimed to investigate the association between serum selenium and serum concentrations of sex steroid hormones including estradiol in a nationally representative sample of U.S. men to investigate one mechanism by which selenium may influence prostate cancer risk. METHODS: The study included 1,420 men ages 20 years or older who participated in the Third National Health and Nutrition Examination Survey between 1988 and 1994. We calculated age/race-ethnicity-adjusted and multivariable-adjusted geometric mean serum concentrations of total and estimated free testosterone and estradiol, androstanediol glucuronide, and sex hormone binding globulin, and compared them across quartiles of serum selenium. RESULTS: Adjusting for age, race/ethnicity, smoking status, serum cotinine, household income, physical activity, alcohol consumption, and percent body fat, mean total estradiol [e.g., Q1, 38.00 pg/mL (95% confidence interval (CI), 36.03-40.08) vs. Q4, 35.29 pg/mL (95% CI, 33.53-37.14); P trend = 0.050] and free estradiol [e.g., Q1, 0.96 pg/mL (95% CI, 0.92-1.01) vs. Q4, 0.90 (95% CI, 0.85-0.95); P trend = 0.065] concentrations decreased over quartiles of selenium. Stratification by smoking and alcohol consumption, showed that the latter observation was stronger for never smokers (P interaction = 0.073) and those with limited alcohol intake (P interaction = 0.017). No associations were observed for the other sex steroid hormones studied. CONCLUSIONS: Our findings suggests that a possible mechanism by which selenium may be protective for prostate cancer is related to estrogen. IMPACT: Further studies of longitudinal measurements of serum and toenail selenium in relation to serum measurements of sex steroid hormones are needed.

Time-Resolved Fluorescence Resonance Energy Transfer Assay for Discovery of Small-Molecule Inhibitors of Methyl-CpG Binding Domain Protein 2.

Methylated DNA binding proteins such as Methyl-CpG Binding Domain Protein 2 (MBD2) can transduce DNA methylation alterations into a repressive signal by recruiting transcriptional co-repressor complexes. Interfering with MBD2 could lead to reactivation of tumor suppressor genes and therefore represents an attractive strategy for epigenetic therapy. We developed and compared fluorescence polarization (FP) and time-resolved fluorescence resonance energy transfer (TR-FRET)-based high-throughput screening (HTS) assays to identify small-molecule inhibitors of the interaction between the methyl binding domain of MBD2 (MBD2-MBD) and methylated DNA. Although both assays performed well in 96-well format, the TR-FRET assay (Z' factor = 0.58) emerged as a superior screening strategy compared with FP (Z' factor = 0.08) when evaluated in an HTS 384-well plate format. Using TR-FRET, we screened the Sigma LOPAC library for MBD2-MBD inhibitors and identified four compounds that also validated in a dose-response series. This included two known DNA intercalators (mitoxantrone and idarubicin) among two other inhibitory compounds (NF449 and aurintricarboxylic acid). All four compounds also inhibited the binding of SP-1, a transcription factor with a GC-rich binding sequence, to a methylated oligonucleotide, demonstrating that the activity was nonspecific. Our results provide proof of principle for using TR-FRET-based HTS to identify small-molecule inhibitors of MBD2 and other DNA-protein interactions.

Dietary chemoprevention of PhIP induced carcinogenesis in male Fischer 344 rats with tomato and broccoli.

The heterocyclic amine, 2-amino-1-methyl-6-phenylimidazo[4,5-B]pyridine (PhIP), found in meats cooked at high temperatures, has been implicated in epidemiological and rodent studies for causing breast, prostate, and colorectal cancers. A previous animal study using a xenograft model has shown that whole tomato and broccoli, when eaten in combination, exhibit a marked effect on tumor reduction compared to when eaten alone. Our aim was to determine if PhIP-induced carcinogenesis can be prevented by dietary consumption of whole tomato + broccoli powders. Male Fischer 344 rats (n = 45) were randomized into the following treatment groups: control (AIN93G diet), PhIP (200 ppm in AIN93G diet for the first 20 weeks of the study), or tomato + broccoli + PhIP (mixed in AIN93G diet at 10% each and fed with PhIP for 20 weeks, and then without PhIP for 32 weeks). Study animals were monitored for 52 weeks and were euthanized as necessary based on a set of criteria for health status and tumor burden. Although there appeared to be some hepatic and intestinal toxicity due to the combination of PhIP and tomato + broccoli, these rodents had improved survival and reduced incidence and/or severity of PhIP-induced neoplastic lesions compared to the PhIP-alone treated group. Rats eating tomato + broccoli exhibited a marked decrease in the number and size of cribiform prostatic intraepitheilial neoplasia/carcinoma in situ (cribiform PIN/CIS) lesions and in the incidence of invasive intestinal adenocarcinomas and skin carcinomas. Although the apparent toxic effects of combined PhIP and tomato + broccoli need additional study, the results of this study support the hypothesis that a diet rich in tomato and broccoli can reduce or prevent dietary carcinogen-induced cancers.

Association of serum α-tocopherol with sex steroid hormones and interactions with smoking: implications for prostate cancer risk.

BACKGROUND: Vitamin E may protect against prostate cancer, possibly only in smokers and, we hypothesize, through altered sex steroid hormones. A controlled trial in smokers showed that sex hormone levels were inversely associated with baseline serum α-tocopherol and decreased in response to vitamin E supplementation. The vitamin E-hormone relation is understudied in non-smokers. METHODS: Serum sex steroid hormones and α-tocopherol were measured for 1,457 men in NHANES III. Multivariable-adjusted geometric mean hormone concentrations by α-tocopherol quintile were estimated. RESULTS: We observed lower mean testosterone, estradiol, and SHBG concentrations with increasing serum α-tocopherol (Q1 = 5.5 and Q5 = 4.6 ng/ml, p-trend = 0.0007; Q1 = 37.8 and Q5 = 33.1 pg/ml, p-trend = 0.02; Q1 = 38.8 and Q5 = 30.6 pg/ml, p-trend = 0.05, respectively). Interactions between serum α-tocopherol and exposure to cigarette smoke for total testosterone, total estradiol, and SHBG were found with the inverse relation observed only among smokers. CONCLUSIONS: Results from this nationally representative, cross-sectional study indicate an inverse association between serum α-tocopherol and circulating testosterone, estradiol, and SHBG, but only in men who smoked. Our findings support vitamin E selectively influencing sex hormones in smokers and afford possible mechanisms through which vitamin E may impact prostate cancer risk.

Defective human MutY phosphorylation exists in colorectal cancer cell lines with wild-type MutY alleles.

Oxidative DNA damage can generate a variety of cytotoxic DNA lesions such as 8-oxoguanine (8-oxoG), which is one of the most mutagenic bases formed from oxidation of genomic DNA because 8-oxoG can readily mispair with either cytosine or adenine. If unrepaired, further replication of A.8-oxoG mispairs results in C:G to A:T transversions, a form of genomic instability. We reported previously that repair of A.8-oxoG mispairs was defective and that 8-oxoG levels were elevated in several microsatellite stable human colorectal cancer cell lines lacking MutY mutations (human MutY homolog gene, hmyh, MYH MutY homolog protein). In this report, we provide biochemical evidence that the defective repair of A.8-oxoG may be due, at least in part, to defective phosphorylation of the MutY protein in these cell lines. In MutY-defective cell extracts, but not extracts with functional MutY, A.8-oxoG repair was increased by incubation with protein kinases A and C (PKA and PKC) and caesin kinase II. Treatment of these defective cells, but not cells with functional MutY, with phorbol-12-myristate-13-acetate also increased the cellular A.8-oxoG repair activity and decreased the elevated 8-oxoG levels. We show that MutY is serine-phosphorylated in vitro by the action of PKC and in the MutY-defective cells by phorbol-12-myristate-13-acetate but that MutY is already phosphorylated at baseline in proficient cell lines. Finally, using antibody-isolated MutY protein, we show that MutY can be directly phosphorylated by PKC that directly increases the level of MutY catalyzed A.8-oxoG repair.