Genetic susceptibility and oxidative stress in prostate cancer: Integrated model with implications for prevention

Alcohol Consumption and the Risk of Prostate Cancer: A Dose-Response Meta-Analysis

Alcohol is widely consumed and is known as a major risk factor for several types of cancers. Yet, it is unclear whether alcohol consumption is associated with the risk of prostate cancer (PCa) or not. We conducted linear and non-linear dose–response meta-analyses of cohort studies on alcohol consumption and PCa risk by types of alcohol (total, wine, beer, and liquor) and PCa (non-aggressive and aggressive). Pubmed and Embase were searched through April 2020 to identify relevant studies. Summary relative risk (RR) and 95% confidence interval (CI) were estimated using a random-effects model. For non-aggressive PCa, by alcohol type, the risk increased linearly with liquor (RR per 14 g/day intake (alcohol content in standard drink) being 1.04 (95% CI = 1.02–1.06, I² = 0%, three studies) and non-linearly with beer (P_{non-linearity} = 0.045, four studies), with increased risk observed in the lower range (RR = 1.03, 95% CI = 1.01–1.05; 14 g/day), with 1.05 (95% CI = 1.01–1.08) at 28 g/day. Wine was not significantly associated with the risk of non-aggressive PCa. For aggressive PCa, a non-linear relationship of diverse shapes was indicated for all types of alcohol in the sensitivity analysis. Compared to non-drinking, a significant positive association was more apparent at lower dose for liquor (RR = 1.12, 95% CI = 1.04–1.20 at 14 g/day; RR = 1.16, 95% CI = 1.03–1.31 at 28 g/day; P_{non-linearity} = 0.005, three studies) but at higher doses for wine (RR = 1.02, 95% CI = 0.90–1.16 at 28 g/day, RR = 1.35, 95% CI = 1.08–1.67 at 56 g/day; P_{non-linearity} = 0.01, four studies). In contrast, decreased risks were indicated at lower doses of beer (RR = 0.85, 95% CI = 0.79–0.92 at 14 g/day; RR = 0.79, 95% CI = 0.70–0.90 at 28 g/day, P_{non-linearity} < 0.001, four studies). Total alcohol consumption was not associated with both types of PCa. In this study, we found heterogeneous associations between alcohol intake and PCa by types of alcohol and PCa.

Evaluation of serum prolidase activity and oxidative stress markers in men with BPH and prostate cancer

Background

Prostate cancer (PCa) and benign prostatic hyperplasia (BPH) are diseases of elderly men and are related to increased oxidative stress (OS). Although prolidase has a role in collagen metabolism, it is also used to evaluate OS in many diseases. However, there is a lack of data about serum prolidase activity (SPA) in prostate cancer. The aim of this study was to evaluate and compare SPA levels in males with BPH and PCa.

Methods

Evaluation was made of a total of 81 men who underwent transrectal ultrasound guided prostate biopsy for a definitive diagnosis due to high PSA levels. Patients were separated into 2 groups as BPH and PCa patients. Pre-biopsy malondialdehyde (MDA), superoxide dismutase (SOD), PSA levels and serum prolidase activities (SPA) were compared between the groups and the correlations of SPA with the other parameters were also investigated in both groups.

Results

BPH was diagnosed in 51 patients and PCa in 30. The mean age of patients was similar in both groups as 63.25 ± 5.81 years in the BPH group 65.30 ± 7.35 years in the PCa group(p:0.081). The median MDA and SOD levels were insignificantly increased in the PCa patients. SPA values were similar in BPH and PCa patients. SPA did not correlate with age, PSA, MDA or SOD levels in either group.

Conclusions

Our study results revealed that serum prolidase activity is similar in BPH and PCa cases and is not correlated with MDA, SOD or PSA levels.

Association of HO-1 and BRCA1 Is Critical for the Maintenance of Cellular Homeostasis in Prostate Cancer

Prostate cancer is the second leading cause of cancer-related death in men worldwide. Many factors that participate in the development of prostate cancer promote imbalance in the redox state of the cell. Accumulation of reactive oxygen species causes injury to cell structures, ultimately leading to cancer development. The antioxidant enzyme heme oxygenase 1 (HMOX1/HO-1) is responsible for the maintenance of the cellular homeostasis, playing a critical role in the oxidative stress and the regulation of prostate cancer development and progression. In the present study, the transcriptional regulation of HO-1 was investigated in prostate cancer. Interestingly, the tumor suppressor BRCA1 binds to the HO-1 promoter and modulates HO-1, inducing its protein levels through both the increment of its promoter activity and the induction of its transcriptional activation. In addition, in vitro and in vivo analyses show that BRCA1 also controls HO-1-negative targets: MMP9, uPA, and Cyclin D1. HO-1 transcriptional regulation is also modulated by oxidative and genotoxic agents. Induction of DNA damage by mitoxantrone and etoposide repressed HO-1 transcription, whereas hydrogen peroxide and doxorubicin induced its expression. Xenograft studies showed that HO-1 regulation by doxorubicin also occurs in vivo. Immunofluorescence analysis revealed that BRCA1 overexpression and/or doxorubicin exposure induced the cytoplasmic retention of HO-1. Finally, the transcription factor NRF2 cooperates with BRCA1 protein to activate HO-1 promoter activity. In summary, these results show that the activation of BRCA1-NRF2/HO-1 axis defines a new mechanism for the maintenance of the cellular homeostasis in prostate cancer.

IMPLICATIONS

Oxidative and genotoxic stress converge on HO-1 transcriptional activity through the combined actions of BRCA1 and NRF2.

Peripheral mononuclear leukocyte DNA damage, plasma prolidase activity, and oxidative status in patients with benign prostatic hyperplasia

OBJECTIVES

Prolidase plays a major role in collagen turnover, matrix remodeling, and cell growth. Benign prostatic hyperplasia (BPH) may be associated with an increased extracellular matrix deposition. Therefore, the present study was designed to investigate the plasma prolidase activity, oxidative status, and peripheral mononuclear leukocyte DNA damage in patients with BPH.

PATIENTS AND METHODS

Twenty-six male patients with BPH and 24 healthy male subjects were included in this study. Blood samples were collected from antecubital vein after an overnight fasting period, and the plasma was separated. Plasma prolidase activity, total antioxidant capacity (TAC), total oxidant status (TOS), and oxidative stress index (OSI) were determined. The peripheral lymphocyte oxidative DNA damage was determined using an alkaline single cell gel electrophoresis assay (comet assay).

RESULTS

The plasma prolidase activity, TOS levels, OSI values, and peripheral mononuclear leukocyte DNA damage were significantly higher (P < 0.001), while the TAC levels were significantly lower (P < 0.001) in patients with BPH than controls. In BPH patients, the prolidase activity was significantly associated with TAC levels (r = -0.366, P < 0.05), TOS levels (r = 0.573, P < 0.001), and OSI (r = 0.618, P < 0.001) and peripheral mononuclear leukocyte DNA damage (r = 0.461, P < 0.001).

CONCLUSIONS

Our results showed that BPH might be associated with an increased oxidative stress, and also an increased plasma prolidase activity. Increased prolidase activity might play an important role in the etiopathogenesis and/or progression of BPH.

Oxidative stress in prostate cancer: changing research concepts towards a novel paradigm for prevention and therapeutics

A mounting body of evidence suggests that increased production of reactive oxygen species (ROS) is linked to aging processes and to the etiopathogenesis of aging-related diseases, such as cancer, diabetes, atherosclerosis and degenerative diseases like Parkinson's and Alzheimer's. Excess ROS are deleterious to normal cells, while in cancer cells, they can lead to accelerated tumorigenesis. In prostate cancer (PC), oxidative stress, an innate key event characterized by supraphysiological ROS concentrations, has been identified as one of the hallmarks of the aggressive disease phenotype. Specifically, oxidative stress is associated with PC development, progression and the response to therapy. Nevertheless, a thorough understanding of the relationships between oxidative stress, redox homeostasis and the activation of proliferation and survival pathways in healthy and malignant prostate remains elusive. Moreover, the failure of chemoprevention strategies targeting oxidative stress reduced the level of interest in the field after the recent negative results of the Selenium and Vitamin E Cancer Prevention Trial (SELECT) trial. Therefore, a revisit of the concept is warranted and several key issues need to be addressed: The consequences of changes in ROS levels with respect to altered redox homeostasis and redox-regulated processes in PC need to be established. Similarly, the key molecular events that cause changes in the generation of ROS in PC and the role for therapeutic strategies aimed at ameliorating oxidative stress need to be identified. Moreover, the issues whether genetic/epigenetic susceptibility for oxidative stress-induced prostatic carcinogenesis is an individual phenomenon and what measurements adequately quantify prostatic oxidative stress are also crucial. Addressing these matters will provide a more rational basis to improve the design of redox-related clinical trials in PC. This review summarizes accepted concepts and principles in redox research, and explores their implications and limitations in PC.

Association between gene polymorphism of manganese superoxide dismutase and prostate cancer risk

Manganese superoxide dismutase (MnSOD) is the most effective antioxidant enzyme in mitochondria and protects cells from reactive oxygen species-induced oxidative damage. The aim of this study was to investigate the association between MnSOD Ala-9 Val gene polymorphism and prostate cancer (PCa) risk in Turkish men with prostate cancer. 33 patients with PCa and 81 control individuals were included in the study. We observed an association between MnSOD Ala/Ala frequency and a higher PCa risk. In addition, we found that the increased risk of early-onset PCa (under age of 65) in the men homozygous for Ala allele was higher than the men homozygous for Val allele. However, we determined that MnSOD Ala-9 Val genotype was not associated with the aggressiveness of the disease. The results of our study suggest that MnSOD Ala/Ala genotype may influence on early-onset of PCa patients, but no effect on subsequent development of the disease in Turkish men. However, our study has a limitation that is small numbers of individuals for cases and controls. Therefore, the presented study limited our statistical power to fully investigate the gene polymorphism on cancer risk.

Serum levels of selenium and smoking habits at age 50 influence long term prostate cancer risk; a 34 year ULSAM follow-up

BACKGROUND

Serum selenium level (s-Se) has been associated with prostate cancer (PrCa) risk. We investigated the relation between s-Se, smoking and non-screening detected PrCa and explored if polymorphisms in two DNA repair genes: OGG1 and MnSOD, influenced any effect of s-Se.

METHODS

ULSAM, a population based Swedish male cohort (n = 2322) investigated at age 50 for s-Se and s-Se influencing factors: serum cholesterol, erythrocyte sedimentation rate and smoking habits. At age 71 a subcohort, (n = 1005) was genotyped for OGG1 and MnSOD polymorphisms.

RESULTS

In a 34-year-follow-up, national registries identified 208 PrCa cases further confirmed in medical records. Participants with s-Se in the upper tertile had a non-significantly lower risk of PrCa. Smokers with s-Se in the two lower tertiles (≤80 μg/L) experienced a higher cumulative incidence of PrCa than smokers in the high selenium tertile (Hazard Ratio 2.39; 95% CI: 1.09-5.25). A high tertile selenium level in combination with non-wt rs125701 of the OGG1 gene in combination with smoking status or rs4880 related variation of MnSOD gene appeared to protect from PrCa.

CONCLUSIONS

S-Se levels and smoking habits influence long-term risk of PrCa. Smoking as a risk factor for PrCa in men with low s-Se is relevant to explore further. Exploratory analyses of variations in OGG1 and MnSOD genes indicate that hypotheses about patterns of exposure to selenium and smoking combined with data on genetic variation in genes involved in DNA repair can be valuable to pursue.

Oxidative stress and antioxidant status in prostate cancer patients: relation to Gleason score, treatment and bone metastasis

Over the last decade, epidemiological, experimental and clinical studies have implicated oxidative stress in the development and progression of prostate cancer. In the present study, we evaluated the oxidative status and antioxidant defense in patients with prostate cancer (PCa) taking into consideration: treatment, Gleason score and bone metastasis. For this, we measured concentrations of plasmatic thiobarbituric acid reactive substances (TBARS), serum protein carbonylation, whole blood catalase (CAT) and superoxide dismutase (SOD) activities, as well as the plasma and erythrocyte thiol levels and serum vitamin C and E concentration. This study was performed on 55 patients with PCa and 55 healthy men. TBARS levels and serum protein carbonylation were higher in PCa patients than in controls and altered levels of antioxidants were found in these patients. CAT activity was decreased and SOD activity was higher in PCa patients when compared with controls. Non-protein thiol levels were increased, however, serum vitamin C and vitamin E content were reduced in PCa patients when compared with controls. In addition, different parameters analyzed in PCa patients based on metastasis, treatment and Gleason score showed changes in oxidative stress biomarkers and antioxidant defenses. These findings may indicate an imbalance in the oxidant/antioxidant status, supporting the idea that oxidative stress plays a role in PCa, moreover, the oxidative profile appear to be modified by bone metastasis, treatment and Gleason score.

What can surrogate tissues tell us about the oxidative stress status of the prostate? A hypothesis-generating in-vivo study

BACKGROUND

Prostatic oxidative stress (OS) is androgen-regulated and a key event in the development of prostate cancer (PC). Thus, reducing prostatic OS is an attractive target for PC prevention strategies. We sought to determine if the individual's prostatic OS status can be determined by examining the OS in surrogate androgen regulated tissues from the same host.

METHODOLOGY/PRINCIPAL FINDINGS

Adult male rats were divided equally into three groups: (A-) underwent bilateral orchiectomy, (A+) received continuous testosterone supplementation or (C) were eugonadal. Serum testosterone, 8-hydroxy-2-deoxyguanosine (8-OHdG) and anti-oxidative capacity (AOC) were determined after 72 hrs and the prostate, salivary glands and the hair follicles' Dermal Papillary Cells (DPC) from each animal were harvested, embedded into tissue microarray and examined for the expression of 8-OHdG by immuno-staining. Multi-variate regression was used to analyze inter-individual differences in OS staining within each androgen group and if there was a correlation between serum testosterone, 8-OHdG or AOC and Prostatic OS in tissues of same host. At the group level, 8-OHdG staining intensity directly correlated with serum testosterone levels in all three target tissues (p>0.01, Mann-Whitney Test). Although different levels of prostatic OS were noted between rats with similar serum testosterone levels and similar systemic OS measurements (p<0.01), there were no intra-individual differences between the OS status of the prostate and DPC (p<0.05).

CONCLUSIONS/SIGNIFICANCE

The level of prostatic OS is correlated with the OS of hair follicles and salivary glands, but not systemic OS. Moreover, systemic AOC negatively correlates with both prostatic and hair follicle OS. This suggests that hair follicle and salivary gland OS can serve as surrogate markers for the efficiency of OS reduction. This has tremendous potential for the rational evaluation of patient response to prevention strategies.

Superoxide dismutase 1 knockdown induces oxidative stress and DNA methylation loss in the prostate

Increased oxidative stress and concordant DNA methylation changes are found during aging and in many malignant processes including prostate cancer. Increased oxidative stress has been shown to inhibit DNA methyltransferase in in vitro assays, but whether this occurs in vivo is unknown. To generate increased oxidative stress we utilized mice containing mutations in the CuZnSOD (Sod1) gene, a major superoxide dismutase in mammals. Increased 8-hydroxy-2'-deoxyguanosine, an adduct indicating oxidative damage, was found in liver and prostate tissues at 2 and 12 mo Sod1 (+/-) mice compared to controls. Prostate tissues from Sod1 (+/-) mice demonstrated decreased weight at 2 mo compared to controls, but this difference was not significant at 12 mo. Histologic changes were not seen. Global DNA methylation was significantly decreased at 2 mo in the prostate in Sod1 (+/-) mice. 11p15 containing the epigenetically modulated insulin-like growth factor 2 (Igf2) and H19 genes, both which display oncogenic functions, may be particularly sensitive to oxidative stress. CpG island methylation at an intergenic CTCF binding site and the Igf2 P3 promoter was decreased in Sod1 mutants compared to controls. This is the first in vivo study to show that a deficiency of Sod1 leads to a decrease in DNA methylation. These studies indicate that increased oxidative stress, a factor implicated in neoplasia, can induce DNA hypomethylation in prostate tissues.

Spontaneous and radiation-induced chromosomal instability and persistence of chromosome aberrations after radiotherapy in lymphocytes from prostate cancer patients

The aim of the study was to compare the spontaneous and ex vivo radiation-induced chromosomal damage in lymphocytes of untreated prostate cancer patients and age-matched healthy donors, and to evaluate the chromosomal damage, induced by radiotherapy, and its persistence. Blood samples from 102 prostate cancer patients were obtained before radiotherapy to investigate the excess acentric fragments and dicentric chromosomes. In addition, in a subgroup of ten patients, simple exchanges in chromosomes 2 and 4 were evaluated by fluorescent in situ hybridization (FISH), before the onset of therapy, in the middle and at the end of therapy, and 1 year later. Data were compared to blood samples from ten age-matched healthy donors. We found that spontaneous yields of acentric chromosome fragments and simple exchanges were significantly increased in lymphocytes of patients before onset of therapy, indicating chromosomal instability in these patients. Ex vivo radiation-induced aberrations were not significantly increased, indicating proficient repair of radiation-induced DNA double-strand breaks in lymphocytes of these patients. As expected, the yields of dicentric and acentric chromosomes, and the partial yields of simple exchanges, were increased after the onset of therapy. Surprisingly, yields after 1 year were comparable to those directly after radiotherapy, indicating persistence of chromosomal instability over this time. Our results indicate that prostate cancer patients are characterized by increased spontaneous chromosomal instability. This instability seems to result from defects other than a deficient repair of radiation-induced DNA double-strand breaks. Radiotherapy-induced chromosomal damage persists 1 year after treatment.

Fibrils of prostatic acid phosphatase fragments boost infections with XMRV (xenotropic murine leukemia virus-related virus), a human retrovirus associated with prostate cancer

The xenotropic murine leukemia virus-related virus (XMRV) has recently been detected in prostate cancer tissues and may play a role in tumorigenesis. It is currently unclear how this virus is transmitted and which factors promote its spread in the prostate. We show that amyloidogenic fragments known as semen-derived enhancer of virus infection (SEVI) originating from prostatic acid phosphatase greatly increase XMRV infections of primary prostatic epithelial and stromal cells. Hybrid simian/human immunodeficiency chimeric virus particles pseudotyped with XMRV envelope protein were used to demonstrate that the enhancing effect of SEVI, or of human semen itself, was at the level of viral attachment and entry. SEVI enhanced XMRV infectivity but did not bypass the requirement for the xenotropic and polytropic retrovirus receptor 1. Furthermore, XMRV RNA was detected in prostatic secretions of some men with prostate cancer. The fact that the precursor of SEVI is produced in abundance by the prostate indicates that XMRV replication occurs in an environment that provides a natural enhancer of viral infection, and this may play a role in the spread of this virus in the human population.

Inflammation, infection, and prostate cancer

PURPOSE OF REVIEW

Recent evidence suggesting that inflammation and infection play a role in the etiology of prostate cancer, and the discovery of a novel virus in men with a genetic susceptibility to prostate cancer is reviewed.

RECENT FINDINGS

Almost 20% of visceral cancers worldwide have proven infectious causes. There is substantial histologic, molecular genetic, and epidemiologic evidence that infections and inflammation are also important in the pathogenesis of prostate cancer. The R462Q allelic variant in RNASEL, an antiviral gene important in the innate immune response to viral infections, increases susceptibility to prostate cancer while resulting in vitro in deficient antiviral defenses, suggesting that prostate cancer could be caused by a virus. The study of R462Q carriers led to the discovery and biologic characterization of a novel retrovirus, xenotropic murine leukemia-related virus, isolated and cloned from prostate tissue of affected men. Biologic studies of this virus show that it is sensitive to inhibition by interferon and its downstream mediator, RNaseL, and that its DNA has integrated into the DNA of some men with prostate cancer.

SUMMARY

Inflammation triggered by infection and other causes underlies the development of prostate cancer, and xenotropic murine leukemia-related virus is a candidate etiologic agent. Ongoing studies seek to define its oncogenic potential and pathogenesis.

Pathological aggressiveness of prostatic carcinomas related to RNASEL R462Q allelic variants

PURPOSE

Allelic variations in the HPC1/RNASEL gene, especially the R462Q single nucleotide polymorphism, have been associated with increased susceptibility to prostate cancer. Prior studies have suggested that HPC1 or R462Q associated tumors present with more aggressive clinical features. We assessed a series of men undergoing radical prostatectomy for clinical and pathological measures of tumor aggressiveness according to the RNASEL R462Q genotype.

MATERIALS AND METHODS

A prospective analysis of 232 men treated for prostate cancer with radical prostatectomy was performed. Disease aggressiveness at diagnosis was assessed by age at disease onset, biopsy Gleason score, clinical T stage and pretreatment prostate specific antigen. Tumor aggressiveness was assessed pathologically by tumor volume, extraprostatic extension, seminal vesicle involvement and lymph node metastasis. Clinical and pathological characteristics were then correlated with RNASEL genotype.

RESULTS

Of the 232 men studied 104 (45%) were homozygous WT, 101 (43%) were heterozygous and 27 (12%) were homozygous for the R462Q variant, mirroring the distribution in the general population. No significant differences were seen between genotypes in age at disease onset, pretreatment characteristics or pathological features, as assessed by surgical grade and pathological stage. Tumors homozygous for the R462Q variant were of smaller volume than other genotypes (p = 0.02).

CONCLUSIONS

This prospective study suggests that prostate cancer in patients with the R462Q allelic variant of the HPC1/RNASEL gene is not associated with more aggressive clinical or pathological features in radical prostatectomy specimens.

Hypoxia and metabolism. Hypoxia, DNA repair and genetic instability

Areas of hypoxic tumour tissue are known to be resistant to treatment and are associated with a poor clinical prognosis. There are several reasons why this might be, including the capacity of hypoxia to drive genomic instability and alter DNA damage repair pathways. Significantly, current models fail to distinguish between the complexities of the hypoxic microenvironment and the biological effects of acute hypoxia exposures versus longer-term, chronic hypoxia exposures on the transcription and translation of proteins involved in genetic stability and cell survival. Acute and chronic hypoxia might lead to different biology within the tumour and this might have a direct effect on the design of new therapies for the treatment of hypoxic tumours.

Nuclear translocation of haeme oxygenase-1 is associated to prostate cancer

The role of oxidative stress in prostate cancer has been increasingly recognised. Acute and chronic inflammations generate reactive oxygen species that result in damage to cellular structures. Haeme oxygenase-1 (HO-1) has cytoprotective effects against oxidative damage. We hypothesise that modulation of HO-1 expression may be involved in the process of prostate carcinogenesis and prostate cancer progression. We thus studied HO-1 expression and localisation in 85 samples of organ-confined primary prostate cancer obtained via radical prostatectomy (Gleason grades 4–9) and in 39 specimens of benign prostatic hyperplasia (BPH). We assessed HO-1 expression by immunohistochemical staining. No significant difference was observed in the cytoplasmic positive reactivity among tumours (84%), non-neoplastic surrounding parenchyma (89%), or BPH samples (87%) (P=0.53). Haeme oxygenase-1 immunostaining was detected in the nuclei of prostate cancer cells in 55 of 85 (65%) patients but less often in non-neoplastic surrounding parenchyma (30 of 85, 35%) or in BPH (9 of 39, 23%) (P<0.0001). Immunocytochemical and western blot analysis showed HO-1 only in the cytoplasmic compartment of PC3 and LNCaP prostate cancer cell lines. Treatment with hemin, a well-known specific inducer of HO-1, led to clear nuclear localisation of HO-1 in both cell lines and highly induced HO-1 expression in both cellular compartments. These findings have demonstrated, for the first time, that HO-1 expression and nuclear localisation can define a new subgroup of prostate cancer primary tumours and that the modulation of HO-1 expression and its nuclear translocation could represent new avenues for therapy.

Tumor hypoxia, DNA repair and prostate cancer progression: new targets and new therapies

Increasingly, the tumor microenvironment and hypoxia are being studied as potential prognostic factors in prostate cancer given their effects on the hypoxia inducible factor-1α and vascular endothelial growth factor signaling pathways. Based on immunohistochemical studies using hypoxic cell markers and direct oxygen-electrode measurements, clinically relevant levels of hypoxia are detected in 30–90% of prostate cancers. Exciting new data suggest that hypoxia can alter cell-cycle checkpoints and DNA repair within the prostate epithelium, thereby driving genetic instability and tumor aggression. Novel therapies designed to target the hypoxic response and resulting defective DNA repair may therefore be effective as chemoprevention agents or as adjuncts to surgery, radiotherapy and chemotherapy to improve clinical outcome.