Prostate cancer in US Air Force veterans of the Vietnam war

Quantum chemical pathways for the formation of 2,3,7,8-tetrachloro dibenzo-p-dioxin (TCDD) from 2,4,5-trichlorophenol: a mechanistic and thermo-kinetic study

CONTEXT

Dioxins, specifically 2,3,7,8-tetrachlorinated dibenzo-p-dioxin (TCDD), are highly toxic dioxins known for their severe health impacts and persistent environmental pollutants. This study focuses on understanding the formation pathways of TCDD from its precursor molecule 2,4,5-trichlorophenol (2,4,5-TCP). In our exploration of reaction pathways from 2,4,5-trichlorophenol (TCP), we delve into three reaction mechanisms: free-radical, direct condensation, and anionic. Our findings highlight the significance of the radical mechanism, particularly propagated by H radicals, with a notable increase in dioxin formation around 900 K. These results are consistent with experimental observations indicating an increase in the conversion of trichlorophenol from 600 to 900 K in the non-catalytic gas phase reaction. Thermodynamic parameters (∆H, ∆S, and ∆G), reaction barriers, and rate constants (k) were calculated across a temperature range of 300-1200 K to support the findings and provide insights into the optimal temperature range for controlling dioxins during the incineration process.

METHOD

In this study, quantum chemical calculations were conducted using density functional theory (DFT) with the B3LYP functional and the 6-311 +  + G(d,p) basis set in Gaussian 16 software. Stationary points, including transition states (TS), were confirmed with frequency calculations. Intrinsic reaction coordinate (IRC) calculations ensured minimum energy paths between TS and products, visualized in GaussView 6.0 Program. Single-point energy calculations utilized a more precise basis set, 6-311 +  + G(3df,2p), for enhanced energy accuracy, incorporating zero-point vibrational energy (ZPE) and other energy corrections. These calculations were repeated over a temperature range of 298.15-1200 K at 1 atm pressure. Finally, rate constant (k) expressions associated with TCDD formation were determined using transition state theory (TST).

Agent orange exposure and prostate cancer risk in the million veteran program

BACKGROUND

The US government considers veterans to have been exposed to Agent Orange if they served in Vietnam while the carcinogen was in use, and these veterans are often deemed at high risk of prostate cancer (PCa). Here, we assess whether presumed Agent Orange exposure is independently associated with increased risk of any metastatic or fatal PCa in a diverse Veteran cohort still alive in the modern era (at least 2011), when accounting for race/ethnicity, family history, and genetic risk.

PATIENTS AND METHODS

Participants in the Million Veteran Program (MVP; enrollment began in 2011) who were on active duty during the Vietnam War era (August 1964-April 1975) were included (n = 301,470). Agent Orange exposure was determined using the US government definition. Genetic risk was assessed via a validated polygenic hazard score. Associations with age at diagnosis of any PCa, metastatic PCa, and death from PCa were assessed via Cox proportional hazards models.

RESULTS AND INTERPRETATION

On univariable analysis, exposure to Agent Orange was not associated with increased PCa (hazard ratio [HR]: 1.02, 95% confidence interval [CI]: 1.00-1.04, p = 0.06), metastatic PCa (HR: 0.98, 95% CI: 0.91-1.05, p = 0.55), or fatal PCa (HR: 0.94, 95% CI: 0.79-1.09, p = 0.41). When accounting for race/ethnicity and family history, Agent Orange exposure was independently associated with slightly increased risk of PCa (HR: 1.06, 95% CI: 1.04-1.09, <10-6) but not with metastatic PCa (HR: 1.07, 95% CI: 0.98-1.15, p = 0.10) or PCa death (HR: 1.02, 95% CI: 0.83-1.23, p = 0.09). Similar results were found when accounting for genetic risk. Agent Orange exposure history may not improve modern PCa risk stratification.

Potential AhR-independent mechanisms of 2,3,7,8-Tetrachlorodibenzo-p-dioxin inhibition of human glioblastoma A172 cells migration

The toxicity of 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is generally believed to be mediated by aryl hydrocarbon receptor (AhR), but some evidence suggests that the effects of TCDD can also be produced through AhR-independent mechanisms. In previous experiments, we found that mainly AhR-dependent mechanism was involved in the migration inhibition of glioblastoma U87 cells by TCDD. Due to the heterogeneity of glioblastomas, not all tumor cells have significant AhR expression. The effects and mechanisms of TCDD on the migration of glioblastomas with low AhR expression are still unclear. We employed a glioblastoma cell line A172 with low AhR expression as a model, using wound healing and Transwell® assay to detect the effect of TCDD on cell migration. We found that TCDD can inhibit the migration of A172 cells without activating AhR signaling pathway. Further, after being pre-treated with AhR antagonist CH223191, the inhibition of TCDD on A172 cells migration was not changed, indicating that the effect of TCDD on A172 cells is not dependent on AhR activation. By transcriptome sequencing analysis, we propose dysregulation of the expression of certain migration-related genes, such as IL6, IL1B, CXCL8, FOS, SYK, and PTGS2 involved in cytokines, MAPK, NF-κB, and IL-17 signaling pathways, as potential AhR-independent mechanisms that mediate the inhibition of TCDD migration in A172 cells.

Agent Orange exposure and prostate cancer risk in the Million Veteran Program

Purpose

Exposure to Agent Orange, a known carcinogen, might increase risk of prostate cancer (PCa). We sought to investigate the association of Agent Orange exposure and PCa risk when accounting for race/ethnicity, family history, and genetic risk in a diverse population of US Vietnam War veterans.

Methods & Materials

This study utilized the Million Veteran Program (MVP), a national, population-based cohort study of United States military veterans conducted 2011-2021 with 590,750 male participants available for analysis. Agent Orange exposure was obtained using records from the Department of Veterans Affairs (VA) using the US government definition of Agent Orange exposure: active service in Vietnam while Agent Orange was in use. Only veterans who were on active duty (anywhere in the world) during the Vietnam War were included in this analysis (211,180 participants). Genetic risk was assessed via a previously validated polygenic hazard score calculated from genotype data. Age at diagnosis of any PCa, diagnosis of metastatic PCa, and death from PCa were assessed via Cox proportional hazards models.

Results

Exposure to Agent Orange was associated with increased PCa diagnosis (HR 1.04, 95% CI 1.01-1.06, p=0.003), primarily among Non-Hispanic White men (HR 1.09, 95% CI 1.06- 1.12, p<0.001). When accounting for race/ethnicity and family history, Agent Orange exposure remained an independent risk factor for PCa diagnosis (HR 1.06, 95% CI 1.04-1.09, p<0.05). Univariable associations of Agent Orange exposure with PCa metastasis (HR 1.08, 95% CI 0.99-1.17) and PCa death (HR 1.02, 95% CI 0.84-1.22) did not reach significance on multivariable analysis. Similar results were found when accounting for polygenic hazard score.

Conclusions

Among US Vietnam War veterans, Agent Orange exposure is an independent risk factor for PCa diagnosis, though associations with PCa metastasis or death are unclear when accounting for race/ethnicity, family history, and/or polygenic risk.

Obesity and Morbidity Risk in the U.S. Veteran

The obesity epidemic in the United States has been well documented and serves as the basis for a number of health interventions across the nation. However, those who have served in the U.S. military (Veteran population) suffer from obesity in higher numbers and have an overall disproportionate poorer health status when compared to the health of the older non-Veteran population in the U.S. which may further compound their overall health risk. This study examined both the commonalities and the differences in obesity rates and the associated co-morbidities among the U.S. Veteran population, utilizing data from the 2018 Behavioral Risk Factor Surveillance System (BRFSS). These data are considered by the Centers for Disease Control and Prevention (CDC) to be the nation’s best source for health-related survey data, and the 2018 version includes 437,467 observations. Study findings show not only a significantly higher risk of obesity in the U.S. Veteran population, but also a significantly higher level (higher odds ratio) of the associated co-morbidities when compared to non-Veterans, including coronary heart disease (CHD) or angina (odds ratio (OR) = 2.63); stroke (OR = 1.86); skin cancer (OR = 2.18); other cancers (OR = 1.73); chronic obstructive pulmonary disease (COPD) (OR = 1.52), emphysema, or chronic bronchitis; arthritis (OR = 1.52), rheumatoid arthritis, gout, lupus, or fibromyalgia; depressive disorders (OR = 0.84), and diabetes (OR = 1.61) at the 0.95 confidence interval level.

Risk for animal and human health related to the presence of dioxins and dioxin-like PCBs in feed and food

The European Commission asked EFSA for a scientific opinion on the risks for animal and human health related to the presence of dioxins (PCDD/Fs) and DL-PCBs in feed and food. The data from experimental animal and epidemiological studies were reviewed and it was decided to base the human risk assessment on effects observed in humans and to use animal data as supportive evidence. The critical effect was on semen quality, following pre- and postnatal exposure. The critical study showed a NOAEL of 7.0 pg WHO2005-TEQ/g fat in blood sampled at age 9 years based on PCDD/F-TEQs. No association was observed when including DL-PCB-TEQs. Using toxicokinetic modelling and taking into account the exposure from breastfeeding and a twofold higher intake during childhood, it was estimated that daily exposure in adolescents and adults should be below 0.25 pg TEQ/kg bw/day. The CONTAM Panel established a TWI of 2 pg TEQ/kg bw/week. With occurrence and consumption data from European countries, the mean and P95 intake of total TEQ by Adolescents, Adults, Elderly and Very Elderly varied between, respectively, 2.1 to 10.5, and 5.3 to 30.4 pg TEQ/kg bw/week, implying a considerable exceedance of the TWI. Toddlers and Other Children showed a higher exposure than older age groups, but this was accounted for when deriving the TWI. Exposure to PCDD/F-TEQ only was on average 2.4- and 2.7-fold lower for mean and P95 exposure than for total TEQ. PCDD/Fs and DL-PCBs are transferred to milk and eggs, and accumulate in fatty tissues and liver. Transfer rates and bioconcentration factors were identified for various species. The CONTAM Panel was not able to identify reference values in most farm and companion animals with the exception of NOAELs for mink, chicken and some fish species. The estimated exposure from feed for these species does not imply a risk.

Association between dioxin and cancer incidence and mortality: a meta-analysis

The objective of the present study was to systematically assess the association between dioxin/2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and cancer incidence and mortality. Systematic literature searches were conducted until July 2015 in Pubmed, Embase and Cochrane library to identify relevant studies. A random-effects model was applied to estimate the pooled odds ratio (OR), risk ratio (RR), standard incidence ratio (SIR) or standard mortality ratio (SMR) for cancer incidence or mortality. In addition, dose-response, meta-regression, subgroup, and publication bias analyses were conducted. Thirty-one studies involving 29,605 cancer cases and 3,478,748 participants were included. Higher external exposure level of TCDD was significantly associated with all cancer mortality (pooled SMR = 1.09, 95% CI: 1.01-1.19, p = 0.04), but not all cancer incidence (pooled RR = 1.01, 95% CI: 0.97-1.06, p = 0.49). Higher blood level of TCDD was both significantly associated with all cancer incidence (pooled RR = 1.57, 95% CI: 1.21-2.04, p = 0.001) and all cancer mortality (pooled SMR = 1.45, 95% CI: 1.25-1.69, p < 0.001). Subgroup analysis suggested that higher external exposure and blood level of TCDD were both significantly associated with the mortality caused by non-Hodgkin's lymphoma. In conclusion, external exposure and blood level of TCDD were both significantly associated with all cancer mortality, especially for non-Hodgkin's lymphoma.

Exposure to pesticides and prostate cancer: systematic review of the literature

INTRODUCTION

Investigations about the association between prostate cancer and environmental and/or occupational pesticide exposure have evidenced a possible role of these chemical substances on tumor etiology, related to their action as endocrine disruptors.

OBJECTIVE

To assess the association between pesticide exposure and prostate cancer by conducting a systematic review of the scientific literature.

MATERIALS AND METHODS

Articles published until August 18, 2015 were searched in the databases MEDLINE/Pubmed, Scielo, and Lilacs using the keywords "pesticides" and "prostate cancer". Only the analytical observational studies whose methodological quality met the criteria established by the New Castle-Ottawa scale were included in this review.

RESULTS

The review included 49 studies published between 1993 and 2015. All studies were in English and analyzed exposure to pesticides and/or agricultural activities. Most studies (32 articles) found a positive association between prostate cancer and pesticides or agricultural occupations, with estimates ranging from 1.01 to 14.10.

CONCLUSION

The evidence provided by the reviewed studies indicates a possible association between the development of prostate cancer and pesticide exposure and/or agricultural occupations.

Influence of dioxin exposure upon levels of prostate-specific antigen and steroid hormones in Vietnamese men

Most studies on the relationship between Agent Orange and prostate cancer have focused on US veterans of the Vietnam War. There have been few studies focusing on the relationship between levels of prostate-specific antigen (PSA) and dioxins or steroid hormones in Vietnamese men. In 2009-2011, we collected blood samples from 97 men who had resided in a "dioxin hotspot" and 85 men from a non-sprayed region in Vietnam. Then levels of PSA, dioxins, and steroid hormones were analyzed. Levels of most dioxins, furans, and non-ortho polychlorinated biphenyls were higher in the hotspot than those in the non-sprayed region. Levels of testosterone, dehydroepiandrosterone, and estradiol differed significantly between the hotspot and the non-sprayed region, but there were no correlations between levels of PSA and steroid hormones and dioxins in either of the two regions. Our findings suggest that PSA levels in Vietnamese men are not associated with levels of dioxin or steroid hormones in these two regions.

A critical review of the epidemiology of Agent Orange/TCDD and prostate cancer

To inform risk assessment and regulatory decision-making, the relationship between 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and prostate cancer requires clarification. This article systematically and critically reviews the epidemiologic evidence on the association between exposure to TCDD or Agent Orange, a TCDD-contaminated herbicide used during the Vietnam War, and prostate cancer risk. Articles evaluated include 11 studies of three cohorts, four case-control or cross-sectional studies, and three case-only studies of military veterans with information on estimated Agent Orange or TCDD exposure; 13 studies of seven cohorts, one case-control study, and eight proportionate morbidity or mortality studies of Vietnam veterans without information on Agent Orange exposure; 11 cohort studies of workers with occupational exposure to TCDD; and two studies of one community cohort with environmental exposure to TCDD. The most informative studies, including those of Vietnam veterans involved in Agent Orange spraying or other handling, herbicide manufacturing or spraying workers with occupational TCDD exposure, and community members exposed to TCDD through an industrial accident, consistently reported no significant increase in prostate cancer incidence or mortality. Only some potentially confounded studies of Vietnam veterans compared with the general population, studies with unreliable estimates of Agent Orange exposure, and analyses of selected subgroups of Vietnam veterans reported positive associations. Overall, epidemiologic research offers no consistent or convincing evidence of a causal relationship between exposure to Agent Orange or TCDD and prostate cancer. More accurate exposure assessment is needed in large epidemiologic studies to rule out a causal association more conclusively.

Serum concentrations of TCDD and other dioxin-like compounds in US Air Force veterans of Operation Ranch Hand

We measured serum concentrations of seven dibenzo-p-dioxin congeners (PCDDs), ten dibenzofurans (PCDFs), four non-ortho polychlorinated biphenyls (noPCBs) and six mono-ortho polychlorinated biphenyls (moPCBs) in 1950 veterans of the Vietnam War. The veterans were participants in the Air Force Health Study (AFHS) who attended the final medical examination in 2002. Blood samples were collected from 777 Ranch Hands involved in the aerial spraying of herbicides in Vietnam and a comparison group of 1173 veterans ("Comparisons") who served in Southeast Asia during the same time period. Results for moPCBs were based on a random subsample of 800 veterans. The median 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) concentrations in 2002 were 5.0 pg g(-1) lipid in Ranch Hands and 2.2 pg g(-1) lipid in Comparisons. No substantial differences were found in measured concentrations of other PCDDs, PCDFs, and noPCBs. Similarly, no substantial differences were found for moPCBs in the subsample. The median total dioxin toxic equivalent (TEQ) in Ranch Hands was 18.7 pg g(-1) lipid for PCDDs, 3.4 pg g(-1) lipid for PCDFs, and 3.2 pg g(-1) lipid for noPCBs. Median TEQs in Comparisons were 14.4 pg g(-1) lipid for PCDDs, 3.5 pg g(-1) lipid for PCDFs, and 3.3 pg g(-1) lipid for noPCBs. These TEQs, with the exception of PCDD TEQ in Ranch Hands (primarily due to elevated TCDD), were similar to or lower than those reported for similar age and gender groups in the 2001-2002 National Health and Nutrition Examination Survey (NHANES). These findings support the assumption that the Ranch Hand veterans were not more highly exposed to dioxin-like compounds other than TCDD than were Comparison veterans or the general US population.

High level of dioxin-TEQ in tissue is associated with Agent Orange exposure but not with biochemical recurrence after radical prostatectomy

BACKGROUND

Agent Orange (AO) was previously identified as a significant risk factor for biochemical recurrence (BCR) after radical prostatectomy (RP) in prostate cancer patients. In this study, we determined the levels of dioxin biological toxicity using toxic equivalency (TEQ) values and examined the impact of dioxin-TEQ level on BCR.

METHODS

A total of 93 men who underwent RP, with a median of 5.3 years of postoperative follow-up, were included in the study. The dioxin-TEQ level of each patient was measured using intraoperatively harvested abdominal subcutaneous fat. The dichotomous categorization of dioxin-TEQ by the 50th percentile (low<50% vs high 50%) was also used to regroup the patient cohort, regardless of the previous history of AO exposure. Comparisons between the dioxin-TEQ levels, clinicopathological characteristics and BCR in AO-exposed and -unexposed men were made to allocate possible risk factors. The multivariable logistic regression model was used to identify significant risk factors associated with BCR, adjusting for other confounding factors.

RESULTS

The median dioxin-TEQ level in 37 AO-exposed patients was significantly higher than that in 56 unexposed patients (22.3 vs 15.0 pg g(-1) fat, respectively, P<0.001). The men with AO exposure were more likely to have a high dioxin-TEQ level (P<0.001). Neither AO exposure nor the level of dioxin-TEQ was associated with BCR. Tumor stage (T3/T4 vs T2) and Gleason grade (Gleason 3+4) were independent risk factors for BCR after RP.

CONCLUSIONS

Exposure to AO significantly increases the adipose level of dioxin-TEQ in patients treated with RP. However, exposure to AO or a high dioxin-TEQ level was not associated with an increased risk of BCR after RP. This lack of association supports the current conclusion that the evidence of carcinogenicity of AO in prostate cancer patients is not sufficient and remains 'limited'.

The relationship between Agent Orange and prostate specific antigen: a comparison of a hotspot and a non-sprayed area in Vietnam

OBJECTIVES

The aim of this study was to explore the impact of Agent Orange exposure for prostate cancer with a comparison of the prostate specific antigen (PSA) levels between a hotspot and a non-sprayed area.

METHODS

The study was conducted in Phu Cat district (hotspot) and Kim Bang district (non-sprayed), with a total of 101 men in the hotspot and 97 men in the non-sprayed area older than 50 years of age. About 5 mL of whole blood and a health status questionnaire were collected from each subject in August 2009-2011.

RESULTS

The mean age of the subjects in the hotspot (68.0 years old) was significantly higher than that of those in the non-sprayed area (65.0 years old). No significant difference was found between the hotspot area (0.93 ng/mL) and the non-sprayed area (0.95 ng/mL) in terms of PSA levels. Likewise, this was not statistically significant after adjusting for age. The prevalence of high PSA levels (>3 ng/mL) did not differ significantly between the hotspot (14 men; 13.9 %) and non-sprayed area (9 men; 9.3 %). No significant difference was found between the hotspot area and the non-sprayed area in terms of occupation (farmer and others). In control subjects, no significant difference was found between the PSA levels in subjects exposed to Agent Orange and non-exposed subjects. Likewise, no significant difference was found between the PSA levels of combatants and civilians.

CONCLUSION

The PSA levels were not significantly different between the hotspot and the non-sprayed area.

Fatty acid patterns and risk of prostate cancer in a case-control study nested within the European Prospective Investigation into Cancer and Nutrition

BACKGROUND

Fatty acids in blood may be related to the risk of prostate cancer, but epidemiologic evidence is inconsistent. Blood fatty acids are correlated through shared food sources and common endogenous desaturation and elongation pathways. Studies of individual fatty acids cannot take this into account, but pattern analysis can. Treelet transform (TT) is a novel method that uses data correlation structures to derive sparse factors that explain variation.

OBJECTIVE

The objective was to gain further insight in the association between plasma fatty acids and risk of prostate cancer by applying TT to take data correlations into account.

DESIGN

We reanalyzed previously published data from a case-control study of prostate cancer nested within the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort. TT was used to derive factors explaining the variation in 26 plasma phospholipid fatty acids of 962 incident prostate cancer cases matched to 1061 controls. Multiple imputation was used to deal with missing data in covariates. ORs of prostate cancer according to factor scores were determined by using multivariable conditional logistic regression.

RESULTS

Four simple factors explained 38% of the variation in plasma fatty acids. A high score on a factor reflecting a long-chain n-3 PUFA pattern was associated with greater risk of prostate cancer (OR for highest compared with lowest quintile: 1.36; 95% CI: 0.99, 1.86; P-trend = 0.041).

CONCLUSION

Pattern analyses using TT groupings of correlated fatty acids indicate that intake or metabolism of long-chain n-3 PUFAs may be relevant to prostate cancer etiology.

Potential protective mechanisms of aryl hydrocarbon receptor (AHR) signaling in benign prostatic hyperplasia

The aryl hydrocarbon receptor (AHR) is an evolutionarily conserved ligand activated transcription factor best known for its role in mediating toxic responses to dioxin-like environmental contaminants. However, AHR signaling has also emerged as an active participant in processes of normal development and disease progression. Here, we review the role of AHR signaling in prostate development and disease processes, with a particular emphasis on benign prostatic hyperplasia (BPH). Inappropriate AHR activation has recently been associated with a decreased risk of symptomatic BPH in humans and has been shown to impair prostate development and disrupt endocrine signaling in rodents. We highlight known physiological responses to AHR activation in prostate and other tissues and discuss potential mechanisms by which it may act in adult human prostate to protect against symptomatic BPH.

TCDD and cancer: a critical review of epidemiologic studies

The authors reviewed the epidemiologic studies on exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and cancer risk, published since the last full-scale review made by the International Agency for Research on Cancer Monographs program in 1997. The update of a cohort of US herbicide producers generated negative results overall; the internal analysis provided evidence of an increased "all-cancer" risk in the highest exposure category, with a statistically significant exposure-response association in some of the many analyses performed. The update of a similar Dutch cohort did not confirm the previously observed association with TCDD exposure. The updated surveillance of the Seveso population provided evidence of increased all-cancer mortality 15-20 years after exposure among those living in the most contaminated area but might also reflect random variation, as overall excesses in the most recent follow-up were not observed. Corresponding data on cancer incidence offer little support to the mortality results. Updated results from cohort studies of Vietnam veterans potentially exposed to TCDD did not consistently suggest an increased risk of cancer. Results of additional, smaller studies of other occupational groups potentially exposed to TCDD, and of community-based case-control studies, did not provide consistent evidence of an increased cancer risk. In conclusion, recent epidemiological evidence falls far short of conclusively demonstrating a causal link between TCDD exposure and cancer risk in humans. The emphasis on results for overall cancer risk-rather than risk for specific neoplasms-is not justified on epidemiologic grounds and is not a reason for ignoring the weaknesses of the available evidence.

Exposure to Agent Orange is a significant predictor of prostate-specific antigen (PSA)-based recurrence and a rapid PSA doubling time after radical prostatectomy

OBJECTIVE

To investigate and report the clinicopathological characteristics and outcomes after radical prostatectomy (RP) in patients with prostate cancer and previous exposure to Agent Orange (AO), particularly in relationship to race.

PATIENTS AND METHODS

In 1495 veterans who had undergone RP the clinicopathological characteristics, biochemical progression rates, and prostate-specific antigen (PSA) doubling time (DT) after recurrence between AO-exposed and unexposed men were compared using logistic and linear regression and Cox proportional hazards analyses, and stratified by race.

RESULTS

The 206 (14%) men with AO exposure were more likely to be black (P = 0.001), younger (P < 0.001), treated more recently (P < 0.001), have a higher body mass index (P = 0.001), have clinical stage T1 disease (P < 0.001), and have lower preoperative PSA levels (P = 0.001). After adjusting for several clinical characteristics, AO exposure was not significantly related to adverse pathological features but was significantly associated with biochemical progression risk (relative risk 1.55, 95% confidence interval 1.15-2.09, P = 0.004) and shorter PSADT (P < 0.001) after recurrence (8.2 vs 18.6 months). When stratified by race, these associations were present and similar in both races, with no significant interaction between race and AO exposure for predicting biochemical recurrence or mean adjusted PSADT (P interaction >0.20).

CONCLUSIONS

Patients with AO exposure and treated with RP were more likely to be black, present with lower risk features, have an increased risk of biochemical progression, and shorter PSADT after recurrence. When stratified by race, the association between AO exposure and poor outcomes was present in both races. These findings suggest that among selected men who choose RP, AO exposure might be associated with more aggressive prostate cancer.

The selective aryl hydrocarbon receptor modulator 6-methyl-1,3,8-trichlorodibenzofuran inhibits prostate tumor metastasis in TRAMP mice

The aryl hydrocarbon receptor (AhR) is a basic-helix-loop-helix transcription factor that binds halogenated aromatic hydrocarbons, polycyclic aromatic hydrocarbons, and endogenous compounds. We previously reported that AhR null (Ahr(-/-)) transgenic adenocarcinoma of the mouse prostate (TRAMP) mice on a C57BL/6J background develop prostate tumors with much greater frequency than AhR wild-type (Ahr(+/+)) TRAMP mice, suggesting that the AhR has tumor suppressor properties. Because AhR signaling pathway inactivation increased susceptibility to prostate tumorigenesis, we tested the hypothesis that a selective AhR modulator (SAhRM), 6-methyl-1,3,8-trichlorodibenzofuran (6-MCDF), can protect against prostate tumorigenesis. TRAMP mice on the standard C57BL/6JxFVB genetic background were fed 0, 10, or 40mg 6-MCDF/kg diet beginning at 8 weeks of age. Tumor incidence, pelvic lymph node metastasis, and serum vascular endothelial growth factor (VEGF) concentrations were determined at 140 days of age. Prostate tumor incidence and size were not significantly reduced in mice fed 6-MCDF. However, the frequency of pelvic lymph node metastasis was reduced fivefold in mice fed the 40mg 6-MCDF/kg diet. Serum VEGF concentrations were also reduced by 6-MCDF treatment, particularly in mice without prostate tumors, and 6-MCDF was shown to act directly on cultured prostates to inhibit VEGF secretion. Together, these results suggest that 6-MCDF inhibits metastasis, in part, by inhibiting prostatic VEGF production prior to tumor formation. This is the first report that 6-MCDF can confer protection against prostate cancer in vivo.

Prostate cancer control and survival in Vietnam veterans exposed to Agent Orange

BACKGROUND

In this study, we evaluated the impact of Agent Orange exposure on survival in Vietnam Veterans undergoing prostate brachytherapy.

METHODS AND MATERIAL

From May 1995 to January 2005, 81 Vietnam veterans (29 with Agent Orange exposure and 52 without) and 433 nonveterans of comparable age (mean age, 58 years) underwent prostate brachytherapy. The mean follow-up was 5.0 years. Biochemical progression-free survival (bPFS) was defined as a prostate-specific antigen (PSA)< or =0.40ng/mL after nadir. Patients with metastatic prostate cancer or hormone refractory disease without obvious metastases who died of any cause were classified as died of prostate cancer. All other deaths were attributed to the immediate cause of death. Multiple parameters were evaluated for impact on survival.

RESULTS

At 9 years, Agent Orange-exposed men were least likely to remain biochemically controlled (89.5%, 100%, and 97.2% in Agent Orange-exposed, nonexposed veterans, and nonveterans, respectively, p=0.012). No significant differences in cause-specific (CSS) (p=0.832) or overall survival (OS) (p=0.363) were discerned. In multivariate analysis, CSS was best predicted by Gleason Score and day 0 D(90), whereas Gleason Score, % positive biopsies, and D(90) predicted for bPFS. None of the evaluated parameters predicted for OS, however, a trend was identified for better OS in younger patients and those with a higher D(90). In addition, Agent Orange exposure did not predict for any of the survival parameters. To date, 22 patients have died (metastatic prostate cancer two, second malignancies nine, cardiovascular disease eight, trauma two, and pulmonary one).

CONCLUSIONS

In this cohort of prostate brachytherapy patients, Agent Orange exposure did not statistically impact survival in multivariate analysis.

AHR signaling in prostate growth, morphogenesis, and disease

Most evidence of aryl hydrocarbon receptor (AHR) signaling in prostate growth, morphogenesis, and disease stems from research using 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) to pharmacologically activate the AHR at various stages of development. This review discusses effects of TCDD on prostate morphogenesis and highlights interactions between AHR and other signaling pathways during normal and aberrant prostate growth. Although AHR signaling modulates estrogen and androgen signaling in other tissues, crosstalk between these steroid hormone receptors and AHR signaling cannot account for actions of TCDD on prostate morphogenesis. Instead, the AHR appears to act within a cooperative framework of developmental signals to regulate timing and patterning of prostate growth. Inappropriate activation of AHR signaling as a result of early life TCDD exposure disrupts the balance of these signals, impairs prostate morphogenesis, and has an imprinting effect on the developing prostate that predisposes to prostate disease in adulthood. Mechanisms of AHR signaling in prostate growth and disease are only beginning to be unraveled and recent studies have revealed its interactions with WNT5A, retinoic acid, fibroblast growth factor 10, and vascular endothelial growth factor signaling pathways.

Mortality patterns among women Vietnam-era veterans: results of a retrospective cohort study

PURPOSE

This research compiled and analyzed the data of two cohorts of women veterans who either served in Vietnam ("Vietnam veteran" cohort, n = 4586) or served elsewhere during the Vietnam War ("non-Vietnam veteran" cohort, n = 5325). All cause and cause-specific mortality were compared between Vietnam and non-Vietnam veteran cohorts, to the U.S. population, and to earlier research. Similar analyses were performed for nurses only.

METHODS

Vital status was determined through December 31, 2004, using primarily the U.S. Department of Veterans Affairs beneficiary file and the Social Security Administration Death Master File. Selected data were submitted to the National Center for Health Statistics for merging with the National Death Index to obtain cause of death. Cox proportional hazard analysis modeling was used to obtain adjusted relative risks (ARR). SEER( *)Stat software was used to compute standardized mortality ratios (SMR) for comparisons to the U.S. population.

RESULTS

Women Vietnam veterans showed a significant deficit (ARR = 0.78, 95% confidence interval [CI] 0.62-0.98) in circulatory system disease relative to non-Vietnam veterans, but significant deficits also were observed when the Vietnam and non-Vietnam cohorts were each compared with women in the U.S. population (SMR = 0.65, 95% CI 0.54-0.77; SMR=0.82, 95% CI 0.73-0.93, respectively). Vietnam veterans had significantly lower mortality than women in the U.S. population for all causes (SMR = 0.87, 95% CI 0.80-0.94). Vietnam veterans were at significantly greater risk of mortality from motor vehicle accidents than non-Vietnam veterans (ARR = 2.60, 95% CI 1.22-5.55) and this appeared to be specific to service in Vietnam based on comparisons to the U.S. population. Patterns did not differ greatly for the analysis on nurse veterans or to earlier mortality studies of these cohorts.

CONCLUSION

Mortality from motor vehicle accidents was significantly associated with service in Vietnam. Mortality patterns generally resembled those reported on in the past.

Environmental and occupational causes of cancer: new evidence 2005-2007

What do we currently know about the occupational and environmental causes of cancer? As of 2007, the International Agency for Research on Cancer (IARC) identified 415 known or suspected carcinogens. Cancer arises through an extremely complicated web of multiple causes, and we will likely never know the full range of agents or combinations of agents. We do know that preventing exposure to individual carcinogens prevents the disease. Declines in cancer rates-such as the drop in male lung cancer cases from the reduction in tobacco smoking or the drop in bladder cancer among cohorts of dye workers from the elimination of exposure to specific aromatic amines-provides evidence that preventing cancer is possible when we act on what we know. Although the overall age-adjusted cancer incidence rates in the United States among both men and women have declined in the last decade, the rates of several types of cancers are on the rise; some of which are linked to environmental and occupational exposures. This report chronicles the most recent epidemiologic evidence linking occupational and environmental exposures with cancer. Peer-reviewed scientific studies published from January 2005 to June 2007 were reviewed, supplementing our state-of-the-evidence report published in September 2005. Despite weaknesses in certain individual studies, we consider the evidence linking the increased risk of several types of cancer with specific exposures somewhat strengthened by recent publications, among them brain cancer from exposure to non-ionizing radiation, particularly radiofrequency fields emitted by mobile telephones; breast cancer from exposure to the pesticide dichlorodiphenyltrichloroethane (DDT) before puberty; leukemia from exposure to 1,3-butadiene; lung cancer from exposure to air pollution; non-Hodgkin's lymphoma (NHL) from exposure to pesticides and solvents; and prostate cancer from exposure to pesticides, polyaromatic hydrocarbons (PAHs), and metal working fluids or mineral oils. In addition to NHL and prostate cancer, early findings from the National Institutes of Health Agricultural Health Study suggest that several additional cancers may be linked to a variety of pesticides. Our report also briefly describes the toxicological evidence related to the carcinogenic effect of specific chemicals and mechanisms that are difficult to study in humans, namely exposures to bis-phenol A and epigenetic, trans-generational effects. To underscore the multi-factorial, multi-stage nature of cancer, we also present a technical description of cancer causation summarizing current knowledge in molecular biology. We argue for a new cancer prevention paradigm, one based on an understanding that cancer is ultimately caused by multiple interacting factors rather than a paradigm based on dubious attributable fractions. This new cancer prevention paradigm demands that we limit exposure to avoidable environmental and occupational carcinogens, in combination with additional important risk factors like diet and lifestyle. The research literature related to environmental and occupational causes of cancer is constantly growing, and future updates will be carried out in light of new biological understanding of the mechanisms and new methods for studying exposures in human populations. The current state of knowledge is sufficient to compel us to act on what we know. We repeat the call of ecologist Sandra Steingraber: "From the right to know and the duty to inquire flows the obligation to act."

Nutritional hormesis

OBJECTIVE

Hormesis, the biological and toxicological concept that small quantities have opposite effects from large quantities, is reviewed with emphasis on its relevance to nutrition.

RESULTS

Hormetic and other dose-response relationships are categorized, depicted, and discussed. Evidence for nutritional hormesis is presented for essential vitamin and mineral nutrients, dietary restriction, alcohol (ethanol), natural dietary and some synthetic pesticides, some herbicides, and acrylamide. Some of the different hormetic mechanisms that have been proposed are reviewed.

CONCLUSIONS

The credence and relevance of hormesis to nutrition are considered to be established. The roles of hormesis in nutritional research and in formulating nutritional guidelines are discussed.

SPONSORSHIP

The New York City Department of Health and Mental Hygiene.