Genomic signatures associated with the development, progression, and outcome of prostate cancer

Prostate cancer remains a common cause of cancer death in men. Applications of new genomic technologies to the recent development of high-quality prostate cancer models in multiple contexts have added great molecular insight into the development of and progression to metastasis. Genomic analysis of DNA, RNA, and protein alterations allows for the global assessment of this disease and provides the molecular framework to improve risk classification, outcome prediction, and development of targeted therapies. The creation of expression profiles and signatures will allow the evaluation of cancer phenotypes and give insight into determining those with increased risk of cancer, identification of critical pathways involved in the development of cancer, prediction of disease outcome, and assessment of the response of cancer to established and novel therapies.This review focuses on highlighting recent work in genomics and on its role in evaluating potential genetic modifiers of prostate cancer and novel biomarkers that may help with prostate cancer diagnosis, its potential to provide a better understanding of prostate cancer behavior and transition to metastatic disease, and its role in current and new therapies in prostate cancer. This framework has the exciting potential to be predictive and provide personalized and individual treatment to the large number of men diagnosed with prostate cancer each year.     

The convergence of hormone regulation and cell cycle in prostate physiology and prostate tumorigenesis

Despite the intense research focused on prostate cancer, it remains the most frequently diagnosed malignancy in men over 40-yr-of-age, and the second most frequent cause of cancer-related deaths in men in the United States (1). In 1990, the National Cancer Institute convened 50 experts and leaders from various disciplines in the prostate cancer field to discuss research directions that would help elucidate the molecular basis of this disease and reduce the incidence and mortality of prostate cancer (2). Critical issues identified at this meeting included the role of androgens and the regulation of cell cycle in prostate tumorigenesis and its progression to androgen-independence. Hormones and cell cycle clearly play important roles in normal and cancerous prostate physiology; however, little information has emerged that clearly delineates their function in the etiology of prostate cancer. Some of the mutational events that occur during prostate tumorigenesis and its progression to androgen-independence involve alterations to normal growth, developmental and apoptotic programs regulated by androgen, and the cell cycle. As such, the delineation of events by which prostate cancer cells circumvent these regulatory mechanisms will be central to our understanding of prostate tumorigenesis and to the development of new modalities to treat this disease. This article is then intended to summarize the functional convergence of androgen regulation and cell cycle in normal prostate physiology and prostate tumorigenesis.     

Epigenetic regulation of prostate cancer

Prostate cancer is a commonly diagnosed cancer in men and a leading cause of cancer deaths. Whilst the underlying mechanisms leading to prostate cancer are still to be determined, it is evident that both genetic and epigenetic changes contribute to the development and progression of this disease. Epigenetic changes involving DNA hypo- and hypermethylation, altered histone modifications and more recently changes in microRNA expression have been detected at a range of genes associated with prostate cancer. Furthermore, there is evidence that particular epigenetic changes are associated with different stages of the disease. Whilst early detection can lead to effective treatment, and androgen deprivation therapy has a high response rate, many tumours develop towards hormone-refractory prostate cancer, for which there is no successful treatment. Reliable markers for early detection and more effective treatment strategies are, therefore, needed. Consequently, there is a considerable interest in the potential of epigenetic changes as markers or targets for therapy in prostate cancer. Epigenetic modifiers that demethylate DNA and inhibit histone deacetylases have recently been explored to reactivate silenced gene expression in cancer. However, further understanding of the mechanisms and the effects of chromatin modulation in prostate cancer are required. In this review, we examine the current literature on epigenetic changes associated with prostate cancer and discuss the potential use of epigenetic modifiers for treatment of this disease.     

Molecular therapeutics in prostate cancer

The purpose of this review is to provide information on the molecular basis of prostate cancer biology and to identify some of the targets for therapy, and highlight some potential strategies for molecular treatment. Here we give a synopsis of what we have learned regarding molecular biology of cancer in general and the directions research might take in the future in order to impact prostate cancer specifically. This work is certainly not encyclopedic in nature and we apologize in advance to colleagues whose work we were no able to include. Hope lies in learning to utilize some of these molecular workings for better prevention, diagnosis, and treatment of the most common solid organ cancer in men. Prostate cancer is a formidable disease and at current rates of diagnosis will affect one-in-six men living in the United States (Greenlee et al., 2000) Many of these men are diagnosed at an early stage of the disease and can be effectively treated by surgery or radiation. However, a significant fraction of men are diagnosed with later stage disease or progress despite early curative therapeutic attempts. Unfortunately, many of these men succumb to prostate cancer, as management options are limited and not always successful. Through an understanding of the molecular processes that occur in the development and progression of prostate cancer, novel therapies will arise that will provide longer survival, better quality of life, and a chance for cure in men afflicted with this disease.     

A New Trick of an Old Molecule: Androgen Receptor Splice Variants Taking the Stage?!

Prostate cancer is the second leading cause of cancer-related death in American men. Although most prostate cancers are initially androgen-dependent and respond to androgen ablation therapy, majority of them eventually relapse and progress into incurable castration-resistant (or hormone refractory) prostate cancer. The underlying mechanisms are the focus of intensive investigation for development of more effective treatment. Mounting evidence from both clinical and basic research has demonstrated that the activity of the androgen receptor (AR) is still required for castration-resistant prostate cancer. Multiple mechanisms by which AR is re-activated under androgen-depleted conditions may be involved in the development of castration resistance. The recent identification of AR splicing variants may add another layer of complexity in AR biology. The present review summarizes recent progress in study of AR splicing variants in prostate cancer.     

Prostate cancer: Re-focusing on androgen receptor signaling

Prostate cancer is the most common, non-dermatologic cancer in men. Since prostate cancer is highly associated with increased age, the incidence of this disease is expected to increase as the population ages. In its initial stages prostate cancer depends upon the actions of androgen, and androgen deprivation therapy induces tumor regression. Currently, androgen deprivation is achieved by either surgical or chemical androgen blockade. Unfortunately, nearly all prostate cancer patients develop tumors that grow despite androgen blockade and ultimately relapse. Many alterations in prostate cancer cells contribute to this state. Although chemotherapy induces short remissions in some patients, there are no curative therapies for metastatic disease. This review summarizes our current understanding in androgen signaling and the mechanisms that allow tumor cells to bypass androgen manipulation therapy. The identification of novel survival pathways and effector molecules that drive androgen independent growth is necessary to develop effective therapies for advanced prostate cancers.     

The Impact of Prostate Cancer and Hormonal Therapy on Bone

Large-scale studies agree that the observed decline in prostate cancer mortality that began in the early 1990s, shortly after prostate-specific antigen testing was introduced in the United States, is most likely explained by more widespread treatment of prostate cancer, including hormonal therapy. Practitioners should be aware of the risk of the development of osteoporosis and of skeletal side effects related to hormonal therapy to optimize the care of men with prostate cancer.Key words: Hormone deprivation therapy, Androgen deprivation therapy, Bone destruction, Osteoporosis, OsteopeniaProstate cancer is the most commonly diagnosed cancer among men in the United States, with approximately 192,280 cases anticipated in 2009.¹ It also remains a common cause of cancer death, with 27,360 deaths anticipated in 2009. Moreover, the declining US death rates from cardiovascular and smoking-related disease coupled with the aging of the population associated with the Baby Boom generation may beget an anticipated increase in prostate cancer diagnoses in the coming years. It has been estimated that about 10% of the US population was over the age of 65 years in 2000 and that this proportion will approximately double by 2030.² As a condition of aging men, prostate cancer is apt to remain a significant, if not growing, public health problem.Current efforts to reduce the mortality burden of prostate cancer have included prostate-specific antigen (PSA)-based screening, but its effect on mortality as assessed in randomized trials, particularly during the first 10 years of follow-up, is controversial.^3,4 But these large-scale studies agree that the observed decline in prostate cancer mortality that began in the early 1990s, shortly after PSA testing was introduced in the United States, is most likely explained by more widespread treatment of prostate cancer, including hormonal therapy.⁵ Given these considerations, it is quite likely that hormone deprivation therapy will remain an important treatment for men with prostate cancer. Therefore, a thorough understanding of its long-term side effects is necessary if we are to optimize the care of men with prostate cancer.     

Pathological and molecular mechanisms of prostate carcinogenesis: implications for diagnosis, detection, prevention, and treatment

Prostate cancer is an increasing threat throughout the world. As a result of a demographic shift in population, the number of men at risk for developing prostate cancer is growing rapidly. For 2002, an estimated 189,000 prostate cancer cases were diagnosed in the U.S., accompanied by an estimated 30,200 prostate cancer deaths [Jemal et al., 2002]. Most prostate cancer is now diagnosed in men who were biopsied as a result of an elevated serum PSA (>4 ng/ml) level detected following routine screening. Autopsy studies [Breslow et al., 1977; Yatani et al., 1982; Sakr et al., 1993], and the recent results of the Prostate Cancer Prevention Trial (PCPT) [Thompson et al., 2003], a large scale clinical trial where all men entered the trial without an elevated PSA (<3 ng/ml) were subsequently biopsied, indicate the prevalence of histologic prostate cancer is much higher than anticipated by PSA screening. Environmental factors, such as diet and lifestyle, have long been recognized contributors to the development of prostate cancer. Recent studies of the molecular alterations in prostate cancer cells have begun to provide clues as to how prostate cancer may arise and progress. For example, while inflammation in the prostate has been suggested previously as a contributor to prostate cancer development [Gardner and Bennett, 1992; Platz, 1998; De Marzo et al., 1999; Nelson et al., 2003], research regarding the genetic and pathological aspects of prostate inflammation has only recently begun to receive attention. Here, we review the subject of inflammation and prostate cancer as part of a "chronic epithelial injury" hypothesis of prostate carcinogenesis, and the somatic genome and phenotypic changes characteristic of prostate cancer cells. We also present the implications of these changes for prostate cancer diagnosis, detection, prevention, and treatment.     

前列腺癌治疗靶点及相关药物药理药效学评估体系

前列腺癌一直是欧美男性高发疾病,在我国尤其是经济发达城市,近年来其发病率随着社会老年化进程加速而呈迅猛上升之势。据估,未来10 年,我国前列腺癌的发病或将进入高峰期,成为男性第1 大癌症杀手。目前前列腺癌尤其是晚期前列腺癌治疗药物的疗效有限且毒副作用较大,是困扰临床医生和患者的难题,故开发高效低毒的抗前列腺癌药物具有重要的现实意义。综述前列腺癌治疗靶点以及包含体内外模型和临床疗效评估指标的抗前列腺癌药物药理药效学评估体系,为前列腺癌治疗药物的研究与开发提供参考。     

WISP1/CCN4: A Potential Target for Inhibiting Prostate Cancer Growth and Spread to Bone

Prostate cancer (PC) is a leading cause of death in men however the factors that regulate its progression and eventual metastasis to bone remain unclear. Here we show that WISP1/CCN4 expression in prostate cancer tissues was up-regulated in early stages of the disease and, further, that it correlated with increased circulating levels of WISP1 in the sera of patients at early stages of the disease. WISP1 was also elevated in the mouse prostate cancer model TRAMP in the hypoplastic diseased tissue that develops prior to advanced carcinoma formation. When the ability of anti-WISP1 antibodies to reduce the spread of PC3-Luc cells to distant sites was tested it showed that twice weekly injections of anti-WISP1 antibodies reduced the number and overall size of distant tumors developed after intracardiac (IC) injection of PC3-Luc cells in mice. The ability of antibodies against WISP1 to inhibit growth of PC3-Luc cancer cells in mice was also evaluated and showed that twice weekly injections of anti-WISP1 antibodies reduced local tumor growth when examined in xenografts. To better understand the mechanism of action, the migration of PC3-Luc cells through membranes with or without a Matrigel™ barrier showed the cells were attracted to WISP1, and that this attraction was inhibited by treatment with anti-WISP1 antibodies. We also show the expression of WISP1 at the bone-tumor interface and in the stroma of early grade cancers suggested WISP1 expression is well placed to play roles in both fostering growth of the cancer and its spread to bone. In summary, the up-regulation of WISP1 in the early stages of cancer development coupled with its ability to inhibit spread and growth of prostate cancer cells makes it both a potential target and an accessible diagnostic marker for prostate cancer.     

Beyond prostate-specific antigen: new serologic biomarkers for improved diagnosis and management of prostate cancer

The use of total prostate-specific antigen (tPSA) measurement has dramatically improved the ability to detect prostate cancer at earlier stages. However, as the number of men presenting with advanced disease (and high tPSA levels) has decreased, and given the fact that tPSA is highly reflective of benign prostatic hyperplasia, the need has emerged for novel biomarkers specifically associated with prostate cancer in order to improve predictive models. Several new biomarkers have shown promise, and studies continue to investigate the role of these markers in the detection, staging, and prognosis of prostate cancer. As new useful biomarkers continue to emerge, guidelines for their employment, as well as coordination of further research studies, are needed; a systematic, phased, nomogram-based model is a rational way to manage these efforts.     

Nuclear matrix proteins as biomarkers in prostate cancer

The nuclear matrix (NM) is the structural framework of the nucleus that consists of the peripheral lamins and pore complexes, an internal ribonucleic protein network, and residual nucleoli. The NM contains proteins that contribute to the preservation of nuclear shape and its organization. These protein components better known as the NM proteins have been demonstrated to be tissue specific, and are altered in many cancers, including prostate cancer. Alterations in nuclear morphology are hallmarks of cancer and are believed to be associated with changes in NM protein composition. Prostate cancer is the most frequently diagnosed cancer in American men and many investigators have identified unique NM proteins that appear to be specific for this disease. These NM protein changes are associated with the development of prostate cancer, as well as in some cases being indicative of cancer stage. Identification of these NM proteins specific for prostate cancer provides an insight to understanding the molecular changes associated with this disease. This article reviews the role of NM proteins as tumor biomarkers in prostate cancer and the potential application of these proteins as therapeutic targets in the treatment of this disease.     

Effect of fatty acids on estradiol and testosterone binding to whole DU-145 prostate cells

Cancer of the prostate is one of the leading causes of cancer related deaths in men. An important role in the development of prostate cancer is played by androgens and androgen ablation is therefore currently used in cancer treatment. In the past, estrogens were widely used in treatment of prostate cancer, but there are indications that estrogens could also be involved in carcinogenesis. Lately, much research has been done on the modulation of the binding of steroid hormones to their receptors by polyunsaturated fatty acids (PUFAs), which could interfere with the steroid hormone's message. Therefore, the aim of this study was to determine in whole DU-145 human prostate cells the effect of EFAs and their metabolites on the binding and affinity of the estrogen receptor (ER) and androgen receptor (AR) to estradiol (E(2)) and testosterone (T), respectively. Fatty acids were dissolved in ethanol and added to the cell culture in a final ethanol concentration of 0.2% on the fourth day of incubation. The results showed that the PUFAs under investigation inhibited the AR's capacity, in contrast to the ER's capacity which was stimulated. However, the dissociation constants (K(d)) of the AR and ER complexes in the presence of the PUFAs, were as follows. Except for eicosapentaenoic acid (EPA) which decreased the AR dissociation constant and EPA and alpha-linolenic acid (ALA) which increased the ER dissociation constant, the remaining FAs had no significant effect on the K(d) values of both the AR and ER complexes. According to these priliminary results it is postulated that men should benefit with a diet rich in certain essential polyunsaturated fatty acids although its function remains to be clarified.     

Breast cancer clinical and translational research: analogies and implications for prostate cancer

Breast and prostate cancer, respectively, are the most common cancers in women and in men in the United States. The management of locally advanced prostate cancer involves a multidisciplinary approach, bearing similarity to the therapeutic approach to breast cancer. Better understanding of the molecular biology of these cancers and the identification of the role played by the cancer stem cells and the tumor microenvironment may translate into better clinical decision making regarding risk classification and treatment allocation. A systematic assessment is presented of the many parallel evolutions in defining and treating high-risk breast cancer as they pertain to prostate cancer.     

Cytotoxic effects of the novel isoflavone,phenoxodiol, on prostate cancer cell lines

Phenoxodiol is an isoflavone derivative that has been shown to elicit cytotoxic effects against a broad range of human cancers. We examined the effect of phenoxodiol on cell death pathways on the prostate cell lines LNCaP, DU145 and PC3, representative of different stages of prostate cancer, and its effects on cell death pathways in these cell lines. Cell proliferation assays demonstrated a significant reduction in the rate of cell proliferation after 48 h exposure to phenoxodiol (10 and 30 μM). FACS analysis and 3′-end labelling indicated that all three prostate cancer cell lines underwent substantial levels of cell death 48 h after treatment. Mitochondrial membrane depolarization, indicative of early-stage cell death signalling, using JC-1 detection, was also apparent in all cell lines after exposure to phenoxodiol in the absence of caspase-3 activation. Caspase inhibition assays indicated that phenoxodiol operates through a caspase-independent cell death pathway. These data demonstrate that phenoxodiol elicits anti-cancer effects in prostate cancer cell lines representative of early and later stages of development through an as-yet-unknown cell death mechanism. These data warrant the further investigation of phenoxodiol as a potential treatment for prostate cancer.     

Gene targeting to the stroma of the prostate and bone

Abstract Stromal–epithelial interactions mediated by paracrine signaling mechanisms dictate prostate development and progression of prostate cancer. The regulatory role of androgens in both the prostate stromal and epithelial compartments set the prostate apart from many other organs and tissues with regard to gene targeting. The identification of androgen-dependent prostate epithelial promoters has allowed successful gene targeting to the prostate epithelial compartment. Currently, there are no transgenic mouse models available to specifically alter gene expression within the prostate stromal compartment. As a primary metastatic site for prostate cancer is bone, the functional dissection of the bone stromal compartment is important for understanding stromal–epithelial interactions associated with metastatic tumor growth. Use of currently available methodologies for the expression or deletion of gene expression in recent research studies has advanced our understanding of the stroma. However, the complexity of stromal heterogeneity within the prostate remains a challenge to obtaining compartment or cell-lineage-specific in vivo models necessary for furthering our understanding of prostatic developmental, benign, tumorigenic, and metastatic growth.     

Prostate cancer risk in testosterone-treated men

Men with classical androgen deficiency have reduced prostate volume and blood prostate-specific antigen (PSA) levels compared with their age peers. As it is plausible that androgen deficiency partially protects against prostate disease, and that restoring androgen exposure increases risk to that of eugonadal men of the same age, men using ART should have age-appropriate surveillance for prostate disease. This should comprise rectal examination and blood PSA measurement at regular intervals (determined by age and family history) according to the recommendations, permanently revisited, published by ISSAM, EAU, Endocrine Society….

Testosterone replacement therapy is now being prescribed more often for aging men, the same population in which prostate cancer incidence increases; it has been suggested that administration in men with unrecognised prostate cancer might promote the development of clinically significant disease. In hypogonadal men who were candidates for testosterone therapy, a 14% incidence of occult cancer was found. A percentage (15.2%) of prostate cancer has been found in the placebo group (with normal DRE and PSA) in the prostate cancer prevention study investigating the chemoprevention potential of finasteride.

The hypothesis that high levels of circulating androgens is a risk factor for prostate cancer is supported by the dramatic regression, after castration, of tumour symptoms in men with advanced prostate cancer. However these effects, seen at a very late stage of cancer development, may not be relevant to reflect the effects of variations within a physiological range at an earlier stage.

Data from all published prospective studies on circulating level of total and free testosterone do not support the hypothesis that high levels of circulating androgens are associated with an increased risk of prostate cancer. A study on a large prospective cohort of 10,049 men, contributes to the gathering evidence that the long standing “androgen hypothesis” of increasing risk with increasing androgen levels can be rejected, suggesting instead that high levels within the reference range of androgens, estrogens and adrenal androgens decrease aggressive prostate cancer risk. Indeed, high-grade prostate cancer has been associated with low plasma level of testosterone. Furthermore, pre-treatment total testosterone was an independent predictor of extraprostatic disease in patients with localized prostate cancer; as testosterone decreases, patients have an increased likelihood of non-organ confined disease and low serum testosterone levels are associated with positive surgical margins in radical retropubic prostatectomy.

A clinical implication of these results concerns androgen supplementation which has become easier to administer with the advent of transdermal preparations (patch or gel) that achieve physiological testosterone serum levels without supra physiological escape levels. During the clinical development of a new testosterone patch in more than 200 primary or secondary hypogonadal patients, no prostate cancer was diagnosed.     

Mass spectrometry-based expression profiling of clinical prostate cancer

The maturation of MS technologies has provided a rich opportunity to interrogate protein expression patterns in normal and disease states by applying expression protein profiling methods. Major goals of this research strategy include the identification of protein biomarkers that demarcate normal and disease populations, and the identification of therapeutic biomarkers for the treatment of diseases such as cancer (Celis, J. E., and Gromov, P. (2003) Proteomics in translational cancer research: Toward an integrated approach. Cancer Cell 3, 9-151). Prostate cancer is one disease that would greatly benefit from implementing MS-based expression profiling methods because of the need to stratify the disease based on molecular markers. In this review, we will summarize the current MS-based methods to identify and validate biomarkers in human prostate cancer. Lastly, we propose a reverse proteomic approach implementing a quantitative MS research strategy to identify and quantify biomarkers implicated in prostate cancer development. With this approach, the absolute levels of prostate cancer biomarkers will be identified and quantified in normal and diseased samples by measuring the levels of native peptide biomarkers in relation to a chemically identical but isotopically labeled reference peptide. Ultimately, a centralized prostate cancer peptide biomarker expression database could function as a repository for the identification, quantification, and validation of protein biomarker(s) during prostate cancer progression in men.     

The role of vitamin D in prostate cancer

Prostate cancer is the second leading cause of cancer deaths in men in the United States. Developing new treatment strategies is critical to improving the health of men. This article will be a general review of the field with a focus on research from our laboratory. Our research has focused on four areas in which we have pursued the possible use of 1alpha,25(OH)(2)D(3) and its analogs to treat prostate cancer: 1) The ability of 1alpha,25(OH)(2)D(3) to up-regulate androgen receptors in LNCaP human prostate cancer cells. The implications of this finding on 1alpha,25(OH)(2)D(3)'s ability to inhibit cell growth in vivo are unclear at present.2) The reasons for an inability of 1alpha,25(OH)(2)D(3) to inhibit DU 145 prostate cancer cell growth were explored. We found that combination of an imidazole drug, Liarozole, with 1alpha,25(OH)(2)D(3) was capable of inhibiting DU 145 cell growth.3) A number of low-calcemic vitamin D analogs exhibit potent anti-proliferative activity on prostate cancer cells. We have developed a novel approach using the yeast two-hybrid system to screen for potent analogs.4) The results of a clinical trial of 1alpha,25(OH)(2)D(3) treatment of patients with early recurrent prostate cancer. We provide preliminary evidence that 1alpha,25(OH)(2)D(3) may be effective in slowing the rate of PSA rise in selected cases of prostate cancer.In conclusion, we believe that 1alpha,25(OH)(2)D(3) has a role in the treatment and/or prevention strategies being developed for prostate cancer. However, to increase antiproliferative potency without increasing side-effects, the use of less calcemic analogs appears to be the most reasonable approach.     

长非编码RNA 的表达与前列腺癌的研究进展

前列腺癌是全球发病率第二的男性恶性肿瘤,近年来我国前列腺癌的发病率显著上升。最近,大量研究发现,长非编码RNA表达水平的改变与前列腺癌的发生、发展、诊断、治疗和预后密切相关。该文就长非编码RNA与前列腺癌的关系及相关机理进行综述,有助于读者了解长非编码RNA在前列腺癌发病过程中的重要性,为前列腺癌的综合防治提供线索。