Telomerase is activated in the prostate and seminal vesicles of the castrated rat

Experimentally elevated testosterone shortens telomeres across years in a free-living songbird

Reproductive investment often comes at a cost to longevity, but the mechanisms that underlie these long-term effects are not well understood. In male vertebrates, elevated testosterone has been shown to increase reproductive success, but simultaneously to decrease survival. One factor that may contribute to or serve as a biomarker of these long-term effects of testosterone on longevity is telomeres, which are often positively related to lifespan and have been shown to shorten in response to reproduction. In this longitudinal study, we measured the effects of experimentally elevated testosterone on telomere shortening in free-living, male dark-eyed juncos (Junco hyemalis carolinensis), a system in which the experimental elevation of testosterone has previously been shown to increase reproductive success and reduce survival. We found a small, significant effect of testosterone treatment on telomeres, with testosterone-treated males exhibiting significantly greater telomere shortening with age than controls. These results are consistent with the hypothesis that increased telomere shortening may be a long-term cost of elevated testosterone exposure. As both testosterone and telomeres are conserved physiological mechanisms, our results suggest that their interaction may apply broadly to the long-term costs of reproduction in male vertebrates.

Hormonal regulation of telomerase activity and hTERT expression in steroid-regulated tissues and cancer

Naturally, in somatic cells chromosome ends (telomeres) shorten during each cell division. This process ensures to limit proliferation of somatic cells to avoid malignant proliferation; however, it leads to proliferative senescence. Telomerase contains the reverse transcriptase TERT, which together with the TERC component, is responsible for protection of genome integrity by preventing shortening of telomeres through adding repetitive sequences. In addition, telomerase has non-telomeric function and supports growth factor independent growth. Unlike somatic cells, telomerase is detectable in stem cells, germ line cells, and cancer cells to support self-renewal and expansion. Elevated telomerase activity is reported in almost all of human cancers. Increased expression of hTERT gene or its reactivation is required for limitless cellular proliferation in immortal malignant cells. In hormonally regulated tissues as well as in prostate, breast and endometrial cancers, telomerase activity and hTERT expression are under control of steroid sex hormones and growth factors. Also, a number of hormones and growth factors are known to play a role in the carcinogenesis via regulation of hTERT levels or telomerase activity. Understanding the role of hormones in interaction with telomerase may help finding therapeutical targets for anticancer strategies. In this review, we outline the roles and functions of several steroid hormones and growth factors in telomerase regulation, particularly in hormone regulated cancers such as prostate, breast and endometrial cancer.

Telomeres, aging and reproduction

PURPOSE OF REVIEW

Women's fertility decay starts at the mid 30 s. However, the current delay of childbearing leads to ovarian aging and the need of assisted reproduction technologies (ART). Telomere biology is one of the main pathways involved in organismal aging. Thus, this review will focus on the knowledge acquired during the last 2 years about the telomere pathway and its influence on female fertility and the consequences for the newborn.

RECENT FINDINGS

New research on telomere biology reaffirms the relationship of telomere attrition and female infertility. Shorter maternal telomeres, which could be aggravated by external factors, underly premature ovarian aging and other complications including preeclampsia, preterm birth and idiopathic pregnancy loss. Finally, the telomere length of the fetus or the newborn is also affected by external factors, such as stress and nutrition.

SUMMARY

Recent evidence shows that telomeres are implicated in most processes related to female fertility, embryo development and the newborn's health. Thus, telomere length and telomerase activity may be good biomarkers for early detection of ovarian and pregnancy failures, opening the possibility to use telomere therapies to try to solve the infertility situation.

Antithetic hTERT Regulation by Androgens in Prostate Cancer Cells: hTERT Inhibition Is Mediated by the ING1 and ING2 Tumor Suppressors

Simple Summary

The expression of the catalytic subunit of the human telomerase reverse transcriptase subunit (hTERT) is hormonally controlled. Androgen treatment suppresses the hTERT expression at a transcriptional level in prostate cancer cells. Here, we identified the responsive promoter element that mediates the androgen receptor induced transrepression of hTERT. The negative androgen response element (nARE) is identified as 62 bp located in the core promoter of hTERT. Chromatin immunoprecipitations indicate an androgen-dependent recruitment of the androgen receptor (AR) ING1 and ING2 to the hTERT promoter. Interestingly, the androgen-induced transrepression is mediated by the class II tumor suppressors inhibitor of growth 1 and 2, namely ING1 and ING2, respectively.

Abstract

The human telomerase is a key factor during tumorigenesis in prostate cancer (PCa). The androgen receptor (AR) is a key drug target controlling PCa growth and regulates hTERT expression, but is described to either inhibit or to activate. Here, we reveal that androgens repress and activate hTERT expression in a concentration-dependent manner. Physiological low androgen levels activate, while, notably, supraphysiological androgen levels (SAL), used in bipolar androgen therapy (BAT), repress hTERT expression. We confirmed the SAL-mediated gene repression of hTERT in PCa cell lines, native human PCa samples derived from patients treated ex vivo, as well as in cancer spheroids derived from androgen-dependent or castration resistant PCa (CRPC) cells. Interestingly, chromatin immuno-precipitation (ChIP) combined with functional assays revealed a positive (pARE) and a negative androgen response element (nARE). The nARE was narrowed down to 63 bp in the hTERT core promoter region. AR and tumor suppressors, inhibitor of growth 1 and 2 (ING1 and ING2, respectively), are androgen-dependently recruited. Mechanistically, knockdown indicates that ING1 and ING2 mediate AR-regulated transrepression. Thus, our data suggest an oppositional, biphasic function of AR to control the hTERT expression, while the inhibition of hTERT by androgens is mediated by the AR co-repressors ING1 and ING2.

Reproductive aging and telomeres: Are women and men equally affected?

Successful reproduction is very important for individuals and for society. Currently, the human health span and lifespan are the object of intense and productive investigation with great achievements, compared to the last century. However, reproduction span does not progress concomitantly with lifespan. Reproductive organs age, decreasing the levels of sexual hormones, which are protectors of health through their action on several organs of the body. Thus, this is the starting point of the organismal decay and infertility. This starting point is easily detected in women. In men, it goes under the surface, undetected, but it goes, nevertheless. Regarding fertility, aging alters the hormonal equilibrium, decreases the potential of reproductive organs, diminishes the quality of the gametes and worsen the reproductive outcomes. All these events happen at a different pace and affecting different organs in women and men. The question is what molecular pathways are involved in reproductive aging and if there is a possible halting or even reversion of the aging events. Answers to all these points will be explained in the present review.

Telomere length and genotoxicity in the lung of rats following intragastric exposure to food-grade titanium dioxide and vegetable carbon particles

Vegetable carbon (E153) and titanium dioxide (E171) are widely used as black and white food colour additives. The aim of this study was to assess gastrointestinal tight junction and systemic genotoxic effects in rats following exposure to E153 and E171 for 10 weeks by oral gavage once a week. The expression of tight junction proteins was assessed in intestinal tissues. Levels of DNA strand breaks, oxidatively damaged DNA and telomere length were assessed in secondary organs. Hydrodynamic suspensions of E153 and E173 indicated mean particles sizes of 230 and 270 nm, respectively, and only E153 gave rise to intracellular production of reactive oxygen species in colon epithelial (Caco-2) cells. Rats exposed to E153 (6.4 mg/kg/week) or E171 (500 mg/kg/week) had decreased gene expression of the tight junction protein TJP1 (P < 0.05). E153 (6.4 mg/kg/week) also decreased OCLN (P < 0.05) in the colon and occludin protein expression in the small intestine (P < 0.05). Furthermore, E153 or E171 exposed rats had shorter telomeres in the lung (P < 0.05). Plasma from particle-exposed rats also produced telomere shortening in cultured lung epithelial cells. There were unaltered levels of oxidatively damaged DNA in the liver and lung and no changes in the DNA repair activity of oxidatively damaged DNA in the lung. Altogether, these results indicate that intragastric exposure to E153 and E171 is associated with reduced tight junction protein expression in the intestinal barrier and telomere length shortening in the lung in rats.

Study of telomerase reverse transcriptase and uterine-ovarian-specific genes expression in the endometrial tissue of ovariectomized female Sprague-Dawley rats

BACKGROUND

An in vivo study was carried out to study of telomerase reverse transcriptase and Uterine-Ovarian-specific genes expression in the endometrial tissue of ovariectomized female Sprague-Dawley rats.

MATERIAL AND METHODS

Twenty-four female Sprague-Dawley rats divided into 4 groups of six rats. The first and second groups were ovariectomized and given tamoxifen and tamoxifen-loaded SLN respectively for six days continuously. Group 3 served as the untreated ovariectomized control group and group 4 was made up of untreated normal healthy rats. At the end of the study, the rats were sacrificed and study of the genes expression and serum zinc and copper were carried out.

RESULTS

The results showed that the expression of TERT in the group treated with tamoxifen, and tamoxifen-loaded solid lipid nanoparticles, significantly decreased (p<0.001) compared with ovariectomized control group. The results also revealed that the treatment with tamoxifen-loaded solid lipid nanoparticles increased expression of UO-44 gene compared to ovariectomized control group, while there was no difference between tamoxifen treated and control group.

CONCLUSIONS

Encapsulation of tamoxifen in solid lipid nanoparticles increased its targeting efficiency and improved the impact of the drug on the serum levels of some trace elements.

Low-dose levels of bisphenol A inhibit telomerase via ER/GPR30-ERK signalling, impair DNA integrity and reduce cell proliferation in primary PBMC

Controversy exists about the human health risk of environmental exposure to bisphenol A (BPA). Telomerase activity is emerging both as biomarker and contributing factor for age-related diseases. The effects of BPA exposure at 1–1000 nM on telomerase, DNA integrity and cell proliferation were investigated in PBMC from human donors. Telomerase activity was determined by TRAP-ELISA assay and mRNA expression by qRT-PCR. Mechanistic studies were carried out on the ER/GPR30-ERK pathway using specific inhibitors/antagonists, the comet assay to quantify DNA damage and flow cytometry for cell proliferation. 24 h BPA exposure inhibited telomerase in a non-monotonic pattern with a peak inhibition of 32% at 1 nM (p ≤ 0.01). A significant telomerase inhibition was evident at 1 h after exposure with a minimum at 6 h. Elevated levels of DNA damage frequency and decrease in cell proliferation were evident upon long-term exposure. The results further demonstrate that BPA triggered rapidly an ER/GPR30-ERK transduction pathway that leads to decreased telomerase activity in human PBMC. This is the first study to demonstrate adverse impact of BPA at levels of current human exposure on telomerase in normal cells, mediated by ER/GPR30-ERK. The results suggest a potentially harmful influence of BPA on immune cells and should be addressed in future studies.

A triad of telomerase, androgen receptor and early growth response 1 in prostate cancer cells

Telomerase activation is one of the key mechanisms that allow cells to bypass replicative senescence. Telomerase activity is primarily regulated at the level of transcription of its catalytic unit- hTERT. Prostate cancer (PCa), akin to other cancers, is characterized by high telomerase activity. Existing data suggest that hTERT expression and telomerase activity are positively regulated by androgenic stimuli in androgen-dependent prostate cancer (ADPC) cells. A part of the present study reaffirmed this by demonstrating a decline in the hTERT expression and telomerase activity on "loss of AR" in ADPC cells. The study further addressed 2 unresolved queries, i) whether AR-mediated signaling is of any relevance to hTERT expression in castration-resistant prostate cancer (CRPC) and ii) whether this signaling involves EGR1. Our data suggest that AR-mediated signaling negatively regulates hTERT expression in CRPC cells. Incidental support for the possibility of EGR1 being a regulator of hTERT expression in PCa was provided by i) immunolocalization of hTERT and EGR1 proteins in the same cell type (secretory epithelium) of PCa and BPH tissues; ii) significantly (p< 0.001) higher levels of both these proteins in CRPC (PC3 and DU145), compared with ADPC (LNCaP) cells. A direct evidence for the role of EGR1 in hTERT expression was evident by a significant (p<0.0001) decrease in the hTERT transcript levels in the EGR1-silenced CRPC cells. Further, "gain of AR" led to a significant reduction in the levels of hTERT and EGR1 in CRPC cells. However, restoration of EGR1 levels prevented the decline in the hTERT transcript levels in these cells. Taken together, our data indicate that AR regulates the expression of EGR1, which in turn acts as a positive regulator of hTERT expression in CRPC cells. Thus, AR exerts an inhibitory effect on hTERT expression and telomerase activity by modulating EGR1 levels in CRPC cells.

Telomeres and telomerase in prostate cancer development and therapy

Aberrations in telomere biology are among the earliest events in prostate cancer tumorigenesis and continue during tumour progression. Substantial telomere shortening occurs in prostate cancer cells and high-grade prostatic intraepithelial neoplasia. Not all mechanisms of telomere shortening are understood, but oxidative stress from local inflammation might accelerate prostatic telomere loss. Critically short telomeres can drive the accumulation of tumour-promoting genomic alterations; however, continued telomere erosion is unsustainable and must be mitigated to ensure cancer cell survival and unlimited replication potential. Prostate cancers predominantly maintain telomeres by activating telomerase, but alternative mechanisms of telomere extension can occur in metastatic disease. Telomerase activity and telomere length assessment might be useful in prostate cancer diagnosis and prognosis. Telomere shortening in normal stromal cells has been associated with prostate cancer, whereas variable telomere lengths in prostate cancer cells and telomere shortening in cancer-associated stromal cells correlated with lethal disease. Single-agent telomerase-targeted treatments for solid cancers were ineffective in clinical trials but have not been investigated in prostate cancer and might be useful in combination with established regimens. Telomere-directed strategies have not been explored as extensively. Telomere deprotection strategies have the advantage of being effective in both telomerase-dependent and telomerase-independent cancers. Disruption of androgen receptor function in prostate cancer cells results in telomere dysfunction, indicating telomeres and telomerase as potential therapeutic targets in prostate cancer.

Normal human immune cells are sensitive to telomerase inhibition by Brassica-derived 3,3-diindolylmethane,partly mediated via ERα/β-AP1 signaling

SCOPE

Indole-3-carbinol (I3C) and 3,3'-diindolylmethane (DIM) from Brassica plants are regarded as promising anticancer phytochemicals. The enzyme telomerase is a very attractive target for cancer therapeutics; in normal cells such as lymphocytes, it plays a decisive role for cell maintenance. The effect of I3C and DIM on telomerase in normal human immune cells (PBMC) was studied compared to leukaemia cells (HL-60). Signalling of telomerase regulation via estrogen receptor (ER) was addressed.

METHODS AND RESULTS

Short-term treatment with I3C and DIM inhibited telomerase activity in leukaemia cells (>30 μM I3C; >3 μM DIM). In CD3/CD28 activated PBMC, inhibition was stronger, though (>3 μM I3C; >1 μM DIM). DIM long-term treatment resulted in DNA damage induction and proliferation inhibition in PBMC as determined by the comet assay and CFSE staining, respectively. A relevance of ERα/β-AP1 signaling for telomerase inhibition on enzyme activity, but not transcription level became evident indicating a nonclassical mode for ER regulation of telomerase by DIM.

CONCLUSION

Although desired in cancer cells, this study identified a potential adverse impact of I3C and DIM on telomerase action in normal human immune cells, partly mediated by an ER-dependent mechanism. These new findings should be considered for potential chronic high-dose chemoprevention strategies using these compounds.

Growing up or growing old? Cellular aging linked with testosterone reactivity to stress in youth

BACKGROUND

Given the established relation between testosterone and aging in older adults, we tested whether buccal telomere length (TL), an established cellular biomarker of aging, was associated with testosterone levels in youth.

METHODS

Children, mean age 10.2 years, were recruited from the greater New Orleans area, and salivary testosterone was measured diurnally and during an acute stressor. Buccal TL was measured using monochrome multiplex quantitative real-time polymerase chain reaction. Testosterone and TL data were available on 77 individuals. The association between buccal TL and testosterone was tested using multivariate generalized estimating equations to account for clustering of children within families.

RESULTS

Greater peak testosterone levels (β = -0.87, P < 0.01) and slower recovery (β = -0.56, P < 0.01) and reactivity (β = -1.22, P < 0.01) following a social stressor were significantly associated with shorter buccal TL after controlling for parental age at conception, child age, sex, sociodemographic factors and puberty. No association was initially present between diurnal measurements of testosterone or morning basal testosterone levels and buccal TL. Sex significantly moderated the relation between testosterone reactivity and buccal TL.

CONCLUSIONS

The association between testosterone and buccal TL supports gonadal maturation as a developmentally sensitive biomarker of aging within youth. As stress levels of testosterone were significantly associated with buccal TL, these findings are consistent with the growing literature linking stress exposure and accelerated maturation. The lack of association of diurnal testosterone or morning basal levels with buccal TL bolsters the notion of a shared stress-related maturational mechanism between cellular stress and the hypothalamic pituitary gonadal axis. These data provide novel evidence supporting the interaction of aging, physiologic stress and cellular processes as an underlying mechanism linking negative health outcomes and early life stress.

Estrogen and telomerase in human peripheral blood mononuclear cells

The enzyme telomerase plays an important role in sustaining the capacity of T lymphocytes for homeostatic replication. Recent data have suggested that gonadal steroids might modulate telomerase expression or activity within these cells. We used quantitative assay techniques for both telomerase mRNA expression and telomerase enzymatic activity to systematically examine the effects of physiologic concentrations of estradiol on human peripheral blood mononuclear cells under basal conditions and under conditions that normally enhance telomerase activity in T lymphocytes. Cells from women tended to exhibit higher responsiveness of telomerase activity to induction by T cell receptor engagement. However, we found no evidence of a direct effect of physiologic concentrations of estradiol on human telomerase reverse transcriptase (hTERT) mRNA expression, hTERT protein expression, or telomerase enzymatic activity in cultured PBMCs. While estrogen might exert developmental effects on T cells to alter telomerase responsiveness to T cell receptor engagement, mature peripheral T cells do not respond to estradiol with changes in expression or function of telomerase.

Ovarian stem cells and aging

OBJECTIVE

To review successes to date in the field of ovarian stem cell research and discuss the evidence supporting their potential to rejuvenate the follicular pool during adult life; to present factors that may contribute to their competence; and to address the question of why menopause is an inevitable outcome of advanced age if ovarian stem cells exist.

METHOD

In a review of the literature, relevant articles were identified through a PubMed literature search from inception to July 2010.

RESULTS

The current concept that mammalian ovaries possess a static ovarian reserve is at odds with the experimental results discussed in this review. Ovarian stem cells are likely to be the source of germline stem cells during fetal and adult life, due to their potential to differentiate into competent oocytes given a suitable environment.

CONCLUSIONS

Stem cells in different compartments share properties such as pluripotency, self-renewal, and diminished regenerative potential in old age. Our model of ovarian stem cell aging suggests that menopause is driven by an age-related decline in ovarian stem cell function rather than depletion of a non-renewable follicular reserve. Understanding how ovarian stem cells interact with their surrounding environment moves us a step closer to controlling the female biological clock when it might be clinically desirable.

Molecular regulation of telomerase activity in aging

The process of aging is mitigated by the maintenance and repair of chromosome ends (telomeres), resulting in extended lifespan. This review examines the molecular mechanisms underlying the actions and regulation of the enzyme telomerase reverse transcriptase (TERT), which functions as the primary mechanism of telomere maintenance and regulates cellular life expectancy. Underpinning increased cell proliferation, telomerase is also a key factor in facilitating cancer cell immortalization. The review focuses on aspects of hormonal regulations of telomerase, and the intracellular pathways that converge to regulate telomerase activity with an emphasis on molecular interactions at protein and gene levels. In addition, the basic structure and function of two key telomerase enzyme components-the catalytic subunit TERT and the template RNA (TERC) are discussed briefly.

Women with high telomerase activity in luteinised granulosa cells have a higher pregnancy rate during in vitro fertilisation treatment

OBJECTIVE

To study the effect of telomerase activity (TA) in human luteinised granulosa cells (GCs) on the outcome of in vitro fertilisation treatment.

METHODS

Fifty-six women, aged 23 to 39 years, were enrolled and divided into four groups according to their levels of TA.

RESULTS

Seventeen cases in group A exhibited nondetectable TA, 16 cases in group B expressed low levels of TA (between 0.1 and 0.65 OD × mm), 14 cases in group C expressed moderate TA levels (between 0.66 and 1.00 OD × mm) and 9 cases in group D expressed high levels of TA (more than 1.00 OD × mm). The level of total serum testosterone (T) was significantly higher in groups C and D than in group A (1.43±0.10 vs. 1.08±0.11 nmol/L, P<0.030 and 1.56±0.08 vs. 1.08±0.11 nmol/L, P<0.005, respectively). The TA level was positively correlated with T (r=0.291, P<0.011). No obvious differences were observed in rates of fertilisation, cleavage, mature oocyte formation or good-quality embryos among the groups. The patients in group D exhibited the highest rates of embryo implantation and clinical pregnancy (with rates of 52.63% and 77.78%, respectively, compared with 18.92% and 29.41% in group A, 25.71% and 37.50% in group B and 48% and 50% in group C, with P<0.018 and P=0.112, respectively). The patients in group D also had a greater likelihood of becoming pregnant than those in group A (OR: 9.703, P < 0.023), group B (OR: 14.765, P<0.009) or group C (OR: 5.560, P=0.103).

CONCLUSIONS

Luteinised GCs have a certain potential for proliferation and TA of luteinised GCs may predict the clinical outcomes of IVF treatment. Some unknown regulatory mechanisms between TA and T should be studied in further trials.

The synthetic estrogen diethylstilbestrol (DES) inhibits the telomerase activity and gene expression of prostate cancer cells

BACKGROUND

Telomerase, which lengthens telomeres, is normally down-regulated in somatic cells and highly up-regulated in dividing cells, such as malignant cells. Human prostate cancer is androgen dependent. Estrogens, including the synthetic estrogen diethylstilbestrol (DES), are used in prostate cancer treatment to reduce androgen levels via feedback inhibition of the hypothalamic release of luteinizing hormone releasing hormone (LH-RH). DES has also direct anticancer activities, such as apoptosis induction. We investigated in vitro the effect of DES on telomerase activity and on gene expression in the presence and absence of androgens. We used two prostate cancer cell lines: LNCaP (androgen dependent) and PC3 (androgen independent).

METHODS

LNCaP and PC3 cells were treated with 0.1-1,000 nM testosterone or dihydrotestosterone (DHT) in the presence of DES (25 or 50 microM). Cell telomerase activity and gene expression (mRNA) were measured.

RESULTS

LNCaP: As expected, testosterone and DHT significantly increased telomerase activity and gene expression. However, these effects were inhibited by DES. Contrary to expectations, the combination of DES and testosterone functioned synergistically leading to complete inhibition of telomerase activity. PC3: Testosterone and DHT did not affect telomerase activity and gene expression, whereas DES, in the absence or presence of the androgens, significantly inhibited telomerase activity.

CONCLUSIONS

In the present study, we demonstrated the ability of DES to inhibit telomerase in prostate cancer cells. Androgens did not limit the inhibitory effect and even acted synergistically with DES in the LNCaP line. This phenomenon should be considered if telomerase inhibition is part of prostate cancer treatment.

Quantitative measurement of telomerase activity and localization of its catalytic subunit (hTERT) in chronic inflammation of capsule formation around various model implants and in sarcomas in a rat model

Telomerase is upregulated in some preneoplastic lesions and overexpressed in the majority of malignant tumors, but absent in most nonneoplastic somatic tissues. We analyzed telomerase activity using TRAP-assay in capsule tissues in a rat model with chronic inflammation and in tumor, and visualized the catalytic subunit of telomerase (hTERT) by immunhistochemistry. Significant elevated telomerase activity was found in tumor tissue compared with nonneoplastic tissue (p = 0.047). Cases with a strong inflammation in capsule tissue showed a specific telomerase activity. In these cases, there were no significant differences in telomerase activities compared with malignant tumor tissue. We demonstrate elevated telomerase activity and its diagnostic limits around model implants in a rat model, and visualize its expression not only in malignant tissue but also in inflammatory cells. So the quantitative measurement of telomerase activity should not be applied in general as a marker for malignancy in capsule tissue.

Wild-type but not mutant androgen receptor inhibits expression of the hTERT telomerase subunit: a novel role of AR mutation for prostate cancer development

Androgens play a central role in prostate development and prostate cancer proliferation. Induction of telomerase is an early event in prostate carcinogenesis and is considered as a marker for both primary tumors and metastases. Interestingly, several reports suggest that telomerase activity is regulated by androgens in vivo. Here, we show that the wild-type (WT) human androgen receptor (AR) inhibits the expression of the human telomerase reverse transcriptase (hTERT) and telomerase activity via inhibition of hTERT promoter activity in the presence of androgen receptor agonists. However, pure androgen antagonists failed to repress hTERT transcription. The androgen-mediated repression of hTERT is abrogated in a human prostate cancer cell line exhibiting hormone-dependent growth, which expresses a mutant AR (T877A) frequently occurring in prostate cancer. We reveal that this single amino acid exchange is sufficient for the lack of transrepression. Interestingly, chromatin immunoprecipitation data suggest that, in contrast to the WT AR, the mutant AR is recruited less efficiently to the hTERT promoter in vivo, indicating that loss of transrepression results from reduced chromatin recruitment. Thus, our findings suggest that the WT AR inhibits expression of hTERT, which is indicative of a protective mechanism, whereas the T877A mutation of AR not only broadens the ligand spectrum of the receptor but abrogates this inhibitory mechanism in prostate cancer cells. This novel role of AR mutations in prostate cancer development suggests the benefit to a search for new AR antagonists that inhibit transactivation but allow transrepression.

Hedgehog signalling in prostate regeneration, neoplasia and metastasis

Metastatic cancers adopt certain properties of normal cells in developing or regenerating organs, such as the ability to proliferate and alter tissue organization. We find here that activity of the Hedgehog (Hh) signalling pathway, which has essential roles in developmental patterning, is required for regeneration of prostate epithelium, and that continuous pathway activation transforms prostate progenitor cells and renders them tumorigenic. Elevated pathway activity furthermore distinguishes metastatic from localized prostate cancer, and pathway manipulation can modulate invasiveness and metastasis. Pathway activity is triggered in response to endogenous expression of Hh ligands, and is dependent upon the expression of Smoothened, an essential Hh response component that is not expressed in benign prostate epithelial cells. Monitoring and manipulating Hh pathway activity may thus offer significant improvements in diagnosis and treatment of prostate cancers with metastatic potential.

Androgen ablation therapy for prostate carcinoma suppresses the immunoreactive telomerase subunit hTERT

BACKGROUND

Telomerase is a ribonucleoprotein complex that protects the ends of chromosomes from degradation. Its catalytic subunit, hTERT, controls its activity. Prior data in prostate carcinoma cases indicated that immunohistochemical hTERT reactivity increases with tumor grade and may be absent in lower grade cases. The effect of complete androgen ablation (CAA) on tumor hTERT expression was uncertain.

METHODS

hTERT immunostaining was performed on the cancerous pretreatment biopsy tissue of 30 men who consecutively underwent CAA with bicalutamide and goserelin acetate for 30 days prior to undergoing radical prostatectomy, and on their tumor tissue from radical prostatectomy. As controls, biopsy and prostatectomy samples from 30 untreated men were studied. Nuclear staining was evaluated by two observers, and the change in staining between biopsy and prostatectomy samples was evaluated using the Student t test in both groups.

RESULTS

The percent of reactive tumor nuclei in treated men declined from 36.7% to 13.2% (P = 0.0001), and declined from 19.8% to 16.1% in untreated men (P = 0.4). The greater mean hTERT reactivity in the treated men's biopsy specimens was attributed to an increased proportion of higher (Gleason score > or = 7) grade tumors. The decline in hTERT immunostaining remained significant after normalizing it to that of the untreated group (P = 0.002). The original Gleason scores, corresponding declines in the percentage of reactive tumor nuclei, and significance were: Gleason score < or = 6: 11% (P = 0.03); Gleason score of 7: 23% (P < 0.006); and Gleason score > or = 8: 46% (P < 0.005) (from a mean 63% to 17%).

CONCLUSIONS

CAA for prostate carcinoma can be considered an antitelomerase therapy. The steepest reduction in telomerase activity was noted in the highest grade tumors.

Bisphenol A from dental polycarbonate crown upregulates the expression of hTERT

Bisphenol A (BPA) is one of the endocrine-disrupting chemicals (EDCs) that possess estrogen-like biologic activity. Many dental materials have been reported to release BPA. However, there are few reports available on the release of BPA from dental polycarbonates. The purpose of this study was to investigate the release of BPA from dental polycarbonate crowns and to evaluate the estrogenic activity of BPA. Polycarbonate crowns were immersed in five solvents (water, ethanol, n-hepthane, acetic acid, and acetonitrile) at 37 or 65 degrees C for 24 h. The elution from the material was analyzed by high-performance liquid-chromatography (HPLC) and mass-spectrometry (MS) analysis. BPA release was detected corresponding to the degradation of dental polycarbonates under the some storage conditions (ethanol, acetic acid, and acetonitrile). A previous report proved that estrogen increased human telomerase catalytic subunit (hTERT) mRNA, whereas the effect of EDCs on the hTERT promoter has never been reported. The estrogenic activity of BPA was analyzed by luciferase assay with the use of the hTERT promoter. This assay revealed that BPA was a positive regulator of hTERT transcription. In addition, quantitative real-time PCR analysis showed that BPA increased the expression level of hTERT mRNA in MCF7 cells. Herein, it is demonstrated that hTERT is a new target of BPA.

Prostatic androgen repressed message-1 (PARM-1) may play a role in prostatic cell immortalisation

BACKGROUND

Prostatic androgen-repressed message-1 (PARM-1) has been cloned from the prostate. The transcript of the PARM-1 gene is overexpressed during regression of the prostate after androgen withdrawal. The regulation of PARM-1 by androgens is limited to this organ. We have studied the effects of PARM-1 overexpression in malignant prostate cells.

METHODS

The PARM-1 cDNA was introduced into the rat cancer cell line MAT LyLu along with a doxycycline-dependent regulator.

RESULTS

Maximal expression of PARM-1 (fivefold induction) was achieved by incubating the cells with 2 microM doxycycline for 48 hr. A study investigating the effect of PARM-1 overexpression on the transcription of 588 genes has shown that the TLP1 gene (encoding rat telomerase protein component 1) was the most up-regulated (fourfold). In addition, a dose-dependent increase in telomerase activity was observed in cells overexpressing PARM-1. In vivo, the androgen-deprived prostate showed an increased TLP1 level and increased telomerase activity.

CONCLUSIONS

Increased telomerase activity is often associated with the immortalisation of cancer cell lines, particularly prostatic ones. This could mean that PARM-1 is involved, via increased telomerase activity, in a survival program enabling certain prostatic cells to resist apoptosis, thus conferring a selective advantage to pre-cancerous or cancerous cells.

Expression-patterns of the RNA component (hTR)and the catalytic subunit (hTERT) of human telomerase in nonneoplastic prostate tissue, prostatic intraepithelial neoplasia, and prostate cancer

BACKGROUND

Telomerase, a ribonucleoprotein, is composed of a RNA component (hTR) and two protein subunits. One of these subunits, the catalytic subunit (human telomerase reverse transcriptase, hTERT), represents a reverse transcriptase. hTERT-expression is closely correlated with telomerase activity. The telomerase is thought to be involved in immortalization process. By adding hexamic repeats to the end of chromosomal DNA, the telomeres, the enzyme is able to stop progresssive telomeric DNA loss that occurs during cell division due to the end replication problem that stops the mitotic clock.

METHODS

Expression-patterns of hTR using radioactive in situ hybridization with (35)S-labelled RNA probes were compared with immunhistochemical staining for hTERT in 14 cases of archival paraffin-embedded samples of normal prostatic tissue, high-grade prostatic intraepithelial neoplasia (PIN), prostatic cancer, and one atypical adenomatous hyperplasia (AAH). Beside the expression-patterns each telomerase component was evaluated semiquantitatively.

RESULTS

hTERT and hTR can be found in nonneoplstic tissue and are upregulated in premalignant transformated lesions. AAH showed no hTERT-expression and low hTR-expression. There is a heterogenous expression within prostatic carcinomas.

CONCLUSIONS

No association was observed between the grade of the tumour differentiation and semiquantitative levels of hTR- or hTERT-expression. Telomerase is of limited value for the diagnostic of malignant or benign lesions in prostate.

Proximal location of mouse prostate epithelial stem cells: a model of prostatic homeostasis

Stem cells are believed to regulate normal prostatic homeostasis and to play a role in the etiology of prostate cancer and benign prostatic hyperplasia. We show here that the proximal region of mouse prostatic ducts is enriched in a subpopulation of epithelial cells that exhibit three important attributes of epithelial stem cells: they are slow cycling, possess a high in vitro proliferative potential, and can reconstitute highly branched glandular ductal structures in collagen gels. We propose a model of prostatic homeostasis in which mouse prostatic epithelial stem cells are concentrated in the proximal region of prostatic ducts while the transit-amplifying cells occupy the distal region of the ducts. This model can account for many biological differences between cells of the proximal and distal regions, and has implications for prostatic disease formation.

Quantification of telomerase activity, porphobilinogen deaminase and human telomerase reverse transcriptase mRNA in testicular tissue - new parameters for a molecular diagnostic classification of spermatogenesis disorders

The aim of the study was to evaluate the quantitative detection of human telomerase reverse transcriptase (hTERT) mRNA and telomerase activity as new molecular diagnostic parameters for a subclassification of spermatogenesis disorders. Telomerase activity was detected by a quantitative telomerase PCR ELISA, and hTERT mRNA expression was quantified by fluorescence real-time RT-PCR in a LightCycler in cryopreserved testicular tissue specimens. This was paralleled by a histological workup. The discriminant analysis showed that detection of normalized hTERT expression was able to correctly classify 89.0% of the investigated tissue specimens into the subgroups of full spermatogenesis, maturation arrest or Sertoli-cell-only syndrome. In contrast, discriminant analysis revealed an only 58% accuracy of telomerase activity for the investigated tissue specimens. This study shows that the quantification of hTERT expression in testicular tissue by real-time fluorescence RT-PCR is well suited for correctly classifying spermatogenesis disorders and proved to be markedly superior to the determination of telomerase activity.

Regulation of the human telomerase reverse transcriptase gene

Most somatic human cells lack telomerase activity because they do not express the telomerase reverse transcriptase (hTERT) gene. Conversely, most cancer cells express hTERT and are telomerase positive. For most tumors it is not clear whether hTERT expression is due to their origin from telomerase positive stem cells or to reactivation of the gene during tumorigenesis. Telomerase negative cells lack detectable cytoplasmic and nuclear hTERT transcripts; in telomerase positive cells 0.2 to 6 mRNA molecules/cell can be detected. This suggests that expression is regulated by changes in the rate of hTERT gene transcription. In tumor cell lines hTERT expression behaves like a recessive trait, indicating that lack of expression in normal cells is due to one or several repressors. Studies with monochromosomal hybrids indicate that several chromosomes may code for such repressors. A number of transcription factors, tumor suppressors, cell cycle inhibitors, cell fate determining molecules, hormone receptors and viral proteins have been implicated in the control of hTERT expression; but these studies have not yet provided a clear explanation for the tumor specific expression of the hTERT gene, and the cis-acting elements which are the targets of repression in normal cells still have to be identified.

Cell differentiation lineage in the prostate

Prostatic epithelium consists mainly of luminal and basal cells, which are presumed to differentiate from common progenitor/stem cells. We hypothesize that progenitor/stem cells are highly concentrated in the embryonic urogenital sinus epithelium from which prostatic epithelial buds develop. We further hypothesize that these epithelial progenitor/stem cells are also present within the basal compartment of adult prostatic epithelium and that the spectrum of differentiation markers of embryonic and adult progenitor/stem cells will be similar. The present study demonstrates that the majority of cells in embryonic urogenital sinus epithelium and developing prostatic epithelium (rat, mouse, and human) co-expressed luminal cytokeratins 8 and 18 (CK8, CK18), the basal cell cytokeratins (CK14, CK5), p63, and the so-called transitional or intermediate cell markers, cytokeratin 19 (CK19) and glutathione-S-transferase-pi (GSTpi). The majority of luminal cells in adult rodent and human prostates only expressed luminal markers (CK8, CK18), while the basal epithelial cell compartment contained several distinct subpopulations. In the adult prostate, the predominant basal epithelial subpopulation expressed the classical basal cell markers (CK5, CK14, p63) as well as CK19 and GSTpi. However, a small fraction of adult prostatic basal epithelial cells co-expressed the full spectrum of basal and luminal epithelial cell markers (CK5, CK14, CK8, CK18, CK19, p63, GSTpi). This adult prostatic basal epithelial cell subpopulation, thus, exhibited a cell differentiation marker profile similar to that expressed in embryonic urogenital sinus epithelium. These rare adult prostatic basal epithelial cells are proposed to be the progenitor/stem cell population. Thus, we propose that at all stages (embryonic to adult) prostatic epithelial progenitor/stem cells maintain a differentiation marker profile similar to that of the original embryonic progenitor of the prostate, namely urogenital sinus epithelium. Adult progenitor/stem cells co-express both luminal cell, basal cell, and intermediate cell markers. These progenitor/stem cells differentiate into mature luminal cells by maintaining CK8 and CK18, and losing all other makers. Progenitor/stem cells also give rise to mature basal cells by maintaining CK5, CK14, p63, CK19, and GSTpi and losing K8 and K18. Thus, adult prostate basal and luminal cells are proposed to be derived from a common pleuripotent progenitor/stem cell in the basal compartment that maintains its embryonic profile of differentiation markers from embryonic to adult stages.

Androgen depletion activates telomerase in the prostate of the nonhuman primate, Macaca mulatta

BACKGROUND

The activity of telomerase, an enzyme that synthesizes telomeric repeats at the ends of chromosomes, is not detectable in normal human prostate. However, the majority of human prostate cancers exhibit telomerase activity. Since androgens play a major role in prostate tumorigenesis, we investigated the effect of androgen-depletion on the expression of telomerase activity in the prostate.

METHODS

Adult male rhesus monkeys were either bilaterally castrated or subjected to sham surgery (n = 5 each). Approximately 6 weeks later, the animals were killed and the different regions of the prostate gland were removed and frozen immediately. Telomerase activity was assayed using the telomeric repeat amplification protocol.

RESULTS

All five regions of the prostate from sham operated control animals failed to exhibit telomerase activity. In the castrated monkey, all regions of the prostate, except for the anterior lobe, expressed high levels of telomerase activity.

CONCLUSIONS

Our results indicate that in monkeys, androgen-ablation leads to up-regulation of telomerase activity. The negative-regulation of telomerase activity by androgens is probably lost during prostate tumorigenesis.

Retinoids down-regulate telomerase and telomere length in a pathway distinct from leukemia cell differentiation

Human telomerase, a cellular reverse transcriptase (hTERT), is a nuclear ribonucleoprotein enzyme complex that catalyzes the synthesis and extension of telomeric DNA. This enzyme is specifically activated in most malignant tumors but is usually inactive in normal somatic cells, suggesting that telomerase plays an important role in cellular immortalization and tumorigenesis. Terminal maturation of tumor cells has been associated with the repression of telomerase activity. Using maturation-sensitive and -resistant NB4 cell lines, we analyzed the pattern of telomerase expression during the therapeutic treatment of acute promyelocytic leukemia (APL) by retinoids. Two pathways leading to the down-regulation of hTERT and telomerase activity were identified. The first pathway results in a rapid down-regulation of telomerase that is associated with retinoic acid receptor (RAR)-dependent maturation of NB4 cells. Furthermore, during NB4 cell maturation, obtained independently of RAR by retinoic X receptor (RXR)-specific agonists (rexinoids), no change in telomerase activity was observed, suggesting that hTERT regulation requires a specific signaling and occurs autonomously. A second pathway of hTERT regulation, identified in the RAR-responsive, maturation-resistant NB4-R1 cell line, results in a down-regulation of telomerase that develops slowly during two weeks of all-trans retinoic acid (ATRA) treatment. This pathway leads to telomere shortening, growth arrest, and cell death, all events that are overcome by ectopic expression of hTERT. These findings demonstrate a clear and full dissociation between the process of tumor cell maturation and the regulation of hTERT mRNA expression and telomerase activity by retinoids. We propose telomerase expression as an efficient and selective target of retinoids in the therapy of tumors.

Induction of hTERT expression and telomerase activity by estrogens in human ovary epithelium cells

In mammals, molecular mechanisms and factors involved in the tight regulation of telomerase expression and activity are still largely undefined. In this study, we provide evidence for a role of estrogens and their receptors in the transcriptional regulation of hTERT, the catalytic subunit of human telomerase and, consequently, in the activation of the enzyme. Through a computer analysis of the hTERT 5'-flanking sequences, we identified a putative estrogen response element (ERE) which was capable of binding in vitro human estrogen receptor alpha (ERalpha). In vivo DNA footprinting revealed specific modifications of the ERE region in ERalpha-positive but not ERalpha-negative cells upon treatment with 17beta-estradiol (E2), indicative of estrogen-dependent chromatin remodelling. In the presence of E2, transient expression of ERalpha but not ERbeta remarkably increased hTERT promoter activity, and mutation of the ERE significantly reduced this effect. No telomerase activity was detected in human ovary epithelial cells grown in the absence of E2, but the addition of the hormone induced the enzyme within 3 h of treatment. The expression of hTERT mRNA and protein was induced in parallel with enzymatic activity. This prompt estrogen modulation of telomerase activity substantiates estrogen-dependent transcriptional regulation of the hTERT gene. The identification of hTERT as a target of estrogens represents a novel finding which advances the understanding of telomerase regulation in hormone-dependent cells and has implications for a potential role of hormones in their senescence and malignant conversion.

Effects of androgens on telomerase activity in normal and malignant prostate cells in vitro

BACKGROUND

Recent studies have shown that sex hormones regulate telomerase activity in endometrium and breast tissues. The present study was designed to clarify the effects of androgen on telomerase activity in normal and malignant prostate cells.

METHODS

Androgen-sensitive (LNCaP) and -independent (TSU-Pr1 and DU145) prostate cancer cell lines and normal prostate cells including basal cells were cultured in the presence or absence of 5alpha-dihydrotestosterone (DHT).

RESULTS

Prostate cancer cell lines exhibited high telomerase activity, and normal prostate cells showed low activity. Short or prolonged androgen-deprivation reduced telomerase activity in LNCaP cells, and DHT induced telomerase activity at the G(1) phase of the cell cycle. DHT did not modulate telomerase activity in TSU-Pr1, DU145, and normal cells.

CONCLUSIONS

LNCaP cells had an androgen-dependent pathway to activate telomerase, whereas TSU-Pr1 and DU145 cells as well as normal prostate cells had an androgen-independent pathway. These findings suggest that the regulatory mechanism of telomerase varies during the progression of prostate cancers.

The importance of being dehydroepiandrosterone sulfate (in the blood of primates): a longer and healthier life?

The general aging sequence in tissues of healthy human beings is proposed to be: capillary endothelial cell damage --> arteriosclerosis --> decreased blood flow --> metabolic dysregulation --> secondary tissue damage. Molecular O2 is an obligatory substrate for the successive syntheses of 17alpha-OH pregnenolone and dehydroepiandrosterone (DHEA) by cytochrome P450c17 in the zona reticularis of the adrenal cortex, in which it is suggested that arteriosclerosis --> decreased blood flow --> O2 and glucose deficit --> decreased O2-requiring synthesis of DHEA --> eventual decrease in number of DHEA-synthesizing cells. Aging changes in the zona reticularis synergize with those in the hypothalamo-hypophyseal machinery that controls it neurally and hormonally, with ACTH-evoked pulsatile floods of cortisol coming from the adrenal zona fasciculata, with the onslaught of free radicals generated by the metabolism of catecholamines released from interdigitating cells of the adrenal medulla, and with age-correlated disabilities of erythrocytes to bind and release O2 to decrease the viability of the DHEA and dehydroepiandrosterone sulfate (DHEAS)-forming cells. One of the chief functions of serum DHEAS in the male may be to act as an allosteric facilitator of the binding of testosterone (T) to serum albumin, thereby helping target T to specific receptors and to allosteric sites for rapid and efficient action at the cellular level. There is reason to consider combining O2 therapy with appropriate administration of DHEA and T to optimize steroid functionality in the healthy aging male, and thus, possibly, to alleviate some of the age-related cognitive and physical decrements that occur.

Stem cell features of benign and malignant prostate epithelial cells

PURPOSE

We present a new hypothesis suggesting that the different malignant potential of benign prostatic hyperplasia (BPH) and high grade prostatic intraepithelial neoplasia may be explained by distinct alterations in stem cell-like properties.

MATERIALS AND METHODS

We used our results and the recent literature to develop this hypothesis in the context of an updated prostate stem cell model.

RESULTS

While high grade prostatic intraepithelial neoplasia is a likely precursor lesion to many prostatic adenocarcinomas, BPH rarely if ever progresses directly to carcinoma. Prostate epithelium contains basal and secretory compartments. Secretory cells appear to differentiate from basal cells. Thus, prostatic stem cells most likely reside in the basal compartment. In BPH there is a slight increase in epithelial proliferation, yet most replicating epithelial cells within BPH maintain their normal restriction to the basal compartment. In high grade prostatic intraepithelial neoplasia there is a marked increase in cell proliferation. In contrast to BPH, the majority of proliferating cells in high grade prostatic intraepithelial neoplasia reside in the secretory compartment. The biological significance of this topographic infidelity of proliferation in high grade prostatic intraepithelial neoplasia remains unclear but may relate mechanistically to down regulation of the cyclin dependent kinase inhibitor, p27kip1. Normal basal cells express GSTP1, an enzyme that inactivates reactive electrophiles and organic hydroperoxides, and that may protect cells from deoxyribonucleic acid damaging agents. In contrast, normal secretory cells and high grade prostatic intraepithelial neoplasia cells do not express this enzyme.

CONCLUSIONS

We propose that topographic infidelity of proliferation produces a population of secretory cells replicating in the absence of key genome protective mechanisms, thus setting the stage for an accumulation of genomic alterations and instability in high grade prostatic intraepithelial neoplasia. This action occurs along with activation of telomerase, resulting in an immortal clone capable of developing into invasive carcinoma. The model predicts that genome protection remains intact in BPH, minimizing its malignant potential.

Telomerase activity in normal adult Brown Norway rat seminal vesicle: regional distribution and age-dependent changes

Telomerase activity is essential for protection of cells against the telomere erosion that occurs with each round of cell replication, and thus appears to play a role in the indefinite replication potential of some, but not all, eukaryotic cells. In this regard, some tissues contain stem cells that have a long proliferative life-span and are capable of regenerating or renewing the somatic epithelial cell population within the tissue. Because the adult seminal vesicle exhibits the ability to regenerate during androgen-replacement after castration, we hypothesized that a pool of cells with regenerating potential is present in the adult seminal vesicle, which expresses telomerase activity. In this study, we used a highly sensitive PCR-based telomerase assay [the telomeric repeat amplification protocol (TRAP) assay] to detect telomerase activity in rat seminal vesicle. Our results show that telomerase activity is, indeed, present in the normal adult rat seminal vesicle, but that, in the presence of seminal vesicle fluid, telomerase activity cannot be detected. In fact, seminal vesicle fluid was found to contain some factor(s) that is inhibitory for the TRAP assay. In addition, we found that telomerase activity in the seminal vesicle changes with age and is regionally distributed within the distal, intermediate, and proximal segments of the duct. These results suggest that as is the case for the rat prostate, a population of telomerase-positive cells is present within the adult rat seminal vesicle, and thereby, this organ retains throughout life the potential to regenerate in response to androgen replacement following castration-induced apoptotic cell death.

Novel nuclear phosphoprotein pp32 is highly expressed in intermediate- and high-grade prostate cancer

BACKGROUND

pp32 is a differentiation-regulated nuclear phosphoprotein that is highly expressed in many cancers, but is restricted to self-renewing and long-lived normal cell populations. During murine embryogenesis, pp32 is expressed in primitive cell populations, diminishing as tissues terminally differentiate. Functionally, pp32 confers resistance to programmed cell death and, paradoxically, inhibits transformation mediated in vitro by a broad range of oncogenes, suggesting that pp32 is a multifunctional molecule with potentially complex activities in cancer.

METHODS

We studied pp32 expression in prostatic adenocarcinomas and benign prostatic hyperplasia by in situ hybridization.

RESULTS

In benign prostatic tissues, moderate pp32 expression occurs only in the basal cells. This study found elevated pp32 expression in 98% (54/55) of prostatic adenocarcinomas of Gleason score > or = 5 (P < 0.0001).

CONCLUSIONS

These results suggest that pp32 may be diagnostically useful and may contribute mechanistically to prostate tumor development. In comparison to other molecular alterations, increased pp32 expression is one of the most frequent events in primary prostate cancer.