New concepts in the pathology of prostatic epithelial carcinogenesis

Loss of LDAH associated with prostate cancer and hearing loss

Great strides in gene discovery have been made using a multitude of methods to associate phenotypes with genetic variants, but there still remains a substantial gap between observed symptoms and identified genetic defects. Herein, we use the convergence of various genetic and genomic techniques to investigate the underpinnings of a constellation of phenotypes that include prostate cancer (PCa) and sensorineural hearing loss (SNHL) in a human subject. Through interrogation of the subject's de novo, germline, balanced chromosomal translocation, we first identify a correlation between his disorders and a poorly annotated gene known as lipid droplet associated hydrolase (LDAH). Using data repositories of both germline and somatic variants, we identify convergent genomic evidence that substantiates a correlation between loss of LDAH and PCa. This correlation is validated through both in vitro and in vivo models that show loss of LDAH results in increased risk of PCa and, to a lesser extent, SNHL. By leveraging convergent evidence in emerging genomic data, we hypothesize that loss of LDAH is involved in PCa and other phenotypes observed in support of a genotype-phenotype association in an n-of-one human subject.

Inflammation, focal atrophic lesions, and prostatic intraepithelial neoplasia with respect to risk of lethal prostate cancer

BACKGROUND

A challenge in prostate cancer (PCa) management is identifying potentially lethal disease at diagnosis. Inflammation, focal prostatic atrophy, and prostatic intraepithelial neoplasia (PIN) are common in prostate tumor specimens, but it is not clear whether these lesions have prognostic significance.

METHODS

We conducted a case-control study nested in a cohort of men diagnosed with stage T1a-b PCa through transurethral resection of the prostate in Sweden. Cases are men who died of PCa (n = 228). Controls are men who survived more than 10 years after PCa diagnosis without metastases (n = 387). Slides were assessed for Gleason grade, inflammation, PIN, and four subtypes of focal prostatic atrophy: simple atrophy (SA), postatrophic hyperplasia (PAH), simple atrophy with cyst formation, and partial atrophy. We estimated OR and 95% CI for odds of lethal PCa with multivariable logistic regression.

RESULTS

Chronic inflammation and PIN were more frequently observed in tumors with PAH, but not SA. No specific type of atrophy or inflammation was significantly associated with lethal PCa overall, but there was a suggestion of a positive association for chronic inflammation. Independent of age, Gleason score, year of diagnosis, inflammation, and atrophy type, men with PIN were 89% more likely to die of PCa (95% CI: 1.04-3.42).

CONCLUSION

Our data show that PIN, and perhaps presence of moderate or severe chronic inflammation, may have prognostic significance for PCa.

IMPACT

Lesions in tumor adjacent tissue, and not just the tumor itself, may aid in identification of clinically relevant disease.

Molecular markers in prostate cancer. Part I: predicting lethality

Assessing the lethality of 'early,' potentially organ-confined prostate cancer (PCa) is one of the central controversies in modern-day urological clinical practice. Such cases are often considered for radical 'curative' treatment, although active surveillance may be equally appropriate for many men. Moreover, the balance between judicious intervention and overtreatment can be difficult to judge. The patient's age, comorbidities, family history and philosophy of self-health care can be weighed against clinical features such as the palpability of disease, the number and percentage of biopsy cores involved with the disease, histological grade, presenting prostate-specific antigen (PSA) and possible previous PSA kinetics. For many years, scientists and physicians have sought additional molecular factors that may be predictive for disease stage, progression and lethality. Usually, claims for a 'new' unique marker fall short of true clinical value. More often than not, such molecular markers are useful only in multivariate models. This review summarizes relevant molecular markers and models reported up to and including 2008.

Genetic changes and DNA damage responses in the prostate

The integrity of genomic DNA is challenged by genotoxic stress originating during normal cellular metabolism or by external insults. Cellular responses to DNA damage involve elegant checkpoint cascades enforcing cell cycle arrest, damage repair, apoptosis or cellular senescence. The loss or alterations of genes involved in the damage response pathways have been reported in many cancer susceptibility syndromes and in sporadic tumors. Furthermore, this surveillance pathway is activated during early tumourigenesis presumably due to uncontrolled replicative cycles and has been recognized as one of the main barriers against the development of cancer. This review discusses the relevance of prostatic epithelial cells in prostate tumourigenesis and highlights common molecular changes associated with prostate cancer. Furthermore, DNA damage responses of primary cultures of human prostatic epithelial cells and fresh human prostate tissues are discussed providing evidence for alterations in crucial DNA damage checkpoint molecules. New insights connecting prostate tumourigenesis to alterations and defects in the pathways maintaining genomic integrity will be discussed.

The rationale for inhibiting 5alpha-reductase isoenzymes in the prevention and treatment of prostate cancer

PURPOSE

Androgens are essential for prostatic growth and development but they also have a significant role in prostate disease pathogenesis. Dihydrotestosterone, the primary prostatic androgen, is transformed from testosterone by types 1 and 2 5alpha-reductase and, thus, a potential therapeutic benefit could be achieved through the inhibition of 5alpha-reductase.

MATERIALS AND METHODS

A literature review was performed using PubMed/MEDLINE and congress abstracts to examine evidence supporting the potential of 5alpha-reductase inhibitors in the primary prevention of prostate cancer and in limiting the progression of diagnosed disease.

RESULTS

Prostate disease development is associated with increased expression of each 5alpha-reductase isoenzyme with over expression of type 1 of particular importance in prostate cancer development and progression. The 2 5alpha-reductase inhibitors currently clinically available are finasteride, a type 2 5alpha-reductase inhibitor, and dutasteride, a dual 5alpha-reductase inhibitor. Dual inhibition by dutasteride has been shown to translate into a greater degree and consistency of dihydrotestosterone suppression compared with finasteride. The Prostate Cancer Prevention Trial showed that finasteride significantly decreased the 7-year risk of prostate cancer in men with prostate specific antigen 3.0 ng/ml or less, while the ongoing Reduction by Dutasteride of Prostate Cancer Events study is assessing whether dutasteride decreases the risk of biopsy detectable prostate cancer in men with prostate specific antigen 2.5 to 10 ng/ml and a previous negative biopsy. Small-scale studies have demonstrated potential effects of 5alpha-reductase inhibition in prostate cancer treatment that warrant further investigation, while dutasteride use in men undergoing expectant treatment is also being examined.

CONCLUSIONS

The inhibition of 5alpha-reductase represents a valid target for prostate cancer risk reduction and treatment strategies. The greater suppression of dihydrotestosterone observed with agents that inhibit each 5alpha-reductase isoenzyme may translate into enhanced outcomes and studies are under way to test this hypothesis.

Molecular pathology of prostate cancer

The incidence of prostate cancer has increased in Japan recently and is developing into a life-threatening disease for many Japanese men. This is a result of several convergent factors including the adoption of a Western lifestyle, the widespread use of prostate-specific antigen (PSA) testing, and an increased population of advanced years in Japanese men. Although there is much information to date relating to molecular events underlying the etiology of prostate cancer, it is still unclear as to how and when these genetic alterations occur in each step of tumorigenesis. One fruitful area of investigation has been in the analysis of chromosomal abnormalities commonly observed in prostate cancer. However, no single candidate gene has been definitely identified in cancer initiation and/or progression; in addition, less research has been devoted to understanding the molecular events that underlie tumor histogenesis in terms of likely precursor lesions, such as prostatic intraepithelial neoplasia (PIN). This article reviews the current knowledge of the molecular pathology of prostate cancer, including its histogenesis, genetic and epigenetic alterations, and hereditary factors.

Molecular characterization of an improved vector for evaluation of the tumor suppressor versus oncogene abilities of the androgen receptor

BACKGROUND

There is a growing body of evidence demonstrating that the function of the ligand-occupied androgen receptor (AR) within the nuclei of normal prostatic epithelial cells acts as a tumor suppressor gene. This is in contrast to the well-documented ability of the AR within prostate cancer cells to function as an oncogene. Thus, many groups are attempting to understand the biochemistry and signaling cascade differences involved in the switching of AR from a tumor suppressor to an oncogene.

METHODS

To do this, of plasmid vectors for transgenic expression of AR are very useful. AR negative PC-3 human prostate cancer cells were transfected with a plasmid containing the full length coding sequence of AR without its 5'- or 3'-untranslated regions (UTRs) (i.e., pSG5-AR).

RESULTS

Transgenic expression of the AR protein results in profound growth inhibition which is not relieved by the addition of ligand. A new expression vector for the AR, pAR-IRES-EGFP, has been constructed that contains full-length 5'-UTR which includes the identified translation regulatory regions, the full length coding sequence and the partial 3'-UTR, which includes the identified post-transcriptional regulatory regions. When PC-3 cells were transfected with the pAR-IRES-EGFP vector, it was found that transgenic AR protein expression was not growth inhibitory until ligand was added.

CONCLUSIONS

These pSG5-AR versus pSAR-IRES-EGFP clones are being studied to determine the molecular pathways explaining their different response to AR and ligand.

Lycopene inhibits the growth of normal human prostate epithelial cells in vitro

Lycopene has repeatedly been shown to inhibit the growth of human prostate cells in vitro. However, previous studies with lycopene have focused on cancer specimens, and it is still unclear whether this carotenoid affects the growth of normal human prostate cells as well. Therefore, we investigated the effects of lycopene on normal human prostate epithelial cells (PrEC) by treating them with synthetic all-E-lycopene (up to 5 micromol/L) and assessing proliferation via [3H]thymidine incorporation. The effects of lycopene on cell cycle progression were investigated via flow cytometry. To elucidate whether lycopene modulates cyclins involved in cell cycle progression, protein expressions of cyclins D1 and E were analyzed. The results show that lycopene significantly inhibited the growth of PrEC in a dose-dependent fashion. Flow cytometry revealed a significant cell cycle arrest in the G0/G1 phase. This effect was confirmed by inhibition of cyclin D1 protein expression, whereas cyclin E levels remained unchanged. The results demonstrate that lycopene inhibits growth of nonneoplastic PrEC in vitro. We hypothesize that lycopene might likewise inhibit the growth of prostatic epithelial cells in vivo. This might have an effect on prostate development and/or on enlargement of prostate tissue as found in benign prostate hyperplasia, a potential precursor of prostate cancer.

Detection of HER-2/neu-positive circulating epithelial cells in prostate cancer patients

HER-2/neu may play a role in prostate carcinogenesis. The aim of this study was to use the expression of HER-2/neu as a molecular marker for the detection of circulating tumour cells (CTCs) in the blood of patients with prostate cancer (PC). Blood samples were collected from 42 patients with PC and nine healthy volunteers. Immunomagnetic beads were used to harvest epithelial cells from peripheral blood mononuclear cells. Total RNA was extracted and reverse transcribed before analysis by real-time PCR with HER-2/neu-specific primers. CTCs were HER-2/neu positive in six out of 11 (54%) patients with metastatic disease and in three out of 31 (9.6%) patients with localised PC (P=0.004). In blood samples from nine healthy volunteers, we detected no expression of HER-2/neu. The present method appears to be minimally invasive, highly sensitive and a specific approach for detecting CTCs in PC. Furthermore, it may help better target HER-2/neu in advanced PC.

Molecular pathways to prostate cancer

PURPOSE

Prostate cancer continues to be a prevalent disease in the United States and western countries. Advances in the fields of molecular biology and genetics coupled with new developments in biotechnology have increased our understanding of events associated with the initiation and progression of prostate cancer. We reviewed recent scientific discoveries relating to genetic predisposition, somatic alterations and epigenetic phenomena involved in the pathogenesis of prostate cancer.

MATERIALS AND METHODS

Reports published in the scientific literature with relevance to the molecular biology, genetics and epigenetics of prostate cancer were identified using the MEDLINE data base. Particular emphasis was placed on articles that investigated the contribution of somatic alterations to prostate cancer.

RESULTS

A multitude of genes have recently been identified that are believed to be relevant to prostate carcinogenesis. A contemporary model for prostate cancer progression should include the potential contribution of inflammation to the development of preneoplastic or neoplastic lesions. Abnormal methylation of important growth regulatory or caretaker genes represents an alternative pathway to cancer in addition to aneuploidy, loss of heterozygosity and gene mutations.

CONCLUSIONS

The identification of molecular markers specific to early and late events in prostate cancer progression is critical for the development of improved detection and prognostication strategies. While there is evidence to support the association between inflammation and prostate cancer, the exact mechanisms by which these processes occur are not well defined. The significant contribution of somatic and epigenetic defects to prostate carcinogenesis underscores the need to develop therapeutic approaches that specifically target these molecular alterations.

Prostate pathology: histologic and molecular perspectives

The field of prostate cancer research is poised for dramatic improvements in our ability to better diagnose men at risk of prostate cancer and to better predict prognosis and response to treatment. Histopathologic and molecular analyses lie at the heart of these issues. Improvements in our understanding of the mechanisms of prostate carcinogenesis and in determining why the prostate seems to be so highly targeted for cancer development will lead to rational strategies of disease prevention.

Executive Summary of the National Cancer Institute Workshop: Highlights and recommendations

Prostate cancer chemoprevention represents a relatively new and promising strategy for reducing the immense public health burden of this devastating cancer of men in the United States and Western societies. Chemoprevention is defined as the administration of agents (drugs, biologics, and natural products) that modulate (inhibit) one or more steps in the multistage carcinogenesis process culminating in invasive adenocarcinoma of the prostate. In 2000, there were an estimated 170,000 new cases of prostate cancer and 31,000 deaths in the United States. During the past decade, the National Cancer Institute (NCI) organized the chemoprevention research program and began testing the first generation of promising agents (eg, 4-(hydroxy)-fenretinide [4-HPR], difluoromethylornithine [DFMO], antiandrogens) in high-risk cohorts and launched the first-large scale US phase 3 primary prevention trial, known as Prostate Cancer Prevention Trial (PCPT-1), in 18,000 average-risk men (age more than 55 years and prostate-specific antigen [PSA] less than 3 ng/mL) treated for 7 years with finasteride or placebo. In the summer of 1998, the NCI Prostate Cancer Progress Review Group (PRG) Report to the director of NCI was published in response to the leadership of the prostate cancer advocacy community in conjunction with Congress. To further elucidate and address critical issues identified in this report and to develop a research agenda for the newly created Prostate and Urologic Cancer Research Group in the Division of Cancer Prevention at NCI, the NCI organized the workshop "New Clinical Trial Strategies for Prostate Cancer Chemoprevention." The major objectives were to promote understanding and cooperation among the NCI, US Food and Drug Administration (FDA), academia, pharmaceutical industry, and the public regarding new opportunities for clinical prevention trials for prostate cancer. The workshop was divided into three concurrent breakout panels and a fourth joint integrative panel. The workshop addressed multiple key areas identified in the PRG report in the following panels: (1) Molecular Targets and Promising Agents in Clinical Development; (2) Intermediate Endpoint Biomarkers for Prevention Trials; (3) High-Risk Study Populations for Prevention Trials, and (4) Preventive Clinical Trial Designs and Regulatory Issues. Expert panelists were drawn from leading academic, pharmaceutical, and government scientists in basic research and clinical investigation. Key pharmaceutical, biotechnology, academic, and National Institutes of Health scientists presented overviews of their new agents and products in clinical development (representing the next generation of promising agents). Senior FDA physicians from the Center for Drugs and Center for Biologics presented on current standards for new drug and biologic approval for chemoprevention efficacy. Some of the key topics included recent advances in the state of knowledge of promising agents in the clinic based on molecular targets as well as bottlenecks in drug development for pharmaceutical sponsors; strategic modulable biomarkers that can serve as primary endpoints in phase 1/2 trials to assess preventive efficacy; high-risk cohorts with precancer (high-grade prostatic intraepithelial neoplasia) and representative clinical trial designs that are ready for immediate translation into efficient prevention trials, such as Bayesian sequential monitoring for early assessment of biologic activity and factorial designs for assessment of multiagent combinations. Finally, each expert panel generated recommendations for areas of future research emphasizing opportunities and infrastructure needs.