Linkage analyses at the chromosome 1 loci 1q24-25 (HPC1), 1q42.2-43 (PCAP), and 1p36 (CAPB) in families with hereditary prostate cancer

A comparative mRNA- and miRNA transcriptomics reveals novel molecular signatures associated with metastatic prostate cancers

Background: Prostate cancer (PC) is a fatally aggressive urogenital cancer killing millions of men, globally. Thus, this study aims to identify key miRNAs, target genes, and drug targets associated with prostate cancer metastasis.

Methods: The miRNA and mRNA expression datasets of 148 prostate tissue biopsies (39 tumours and 109 normal tissues), were analysed by differential gene expression analysis, protein interactome mapping, biological pathway analysis, miRNA-mRNA networking, drug target analysis, and survival curve analysis.

Results: The dysregulated expression of 53 miRNAs and their 250 target genes involved in Hedgehog, ErbB, and cAMP signalling pathways connected to cell growth, migration, and proliferation of prostate cancer cells was detected. The subsequent miRNA-mRNA network and expression status analysis have helped us in narrowing down their number to 3 hub miRNAs (hsa-miR-455-3p, hsa-miR-548c-3p, and hsa-miR-582-5p) and 9 hub genes (NFIB, DICER1, GSK3B, DCAF7, FGFR1OP, ABHD2, NACC2, NR3C1, and FGF2). Further investigations with different systems biology methods have prioritized NR3C1, ABHD2, and GSK3B as potential genes involved in prostate cancer metastasis owing to their high mutation load and expression status. Interestingly, down regulation of NR3C1 seems to improve the prostate cancer patient survival rate beyond 150 months. The NR3C1, ABHD2, and GSK3B genes are predicted to be targeted by hsa-miR-582-5p, besides some antibodies, PROTACs and inhibitory molecules.

Conclusion: This study identified key miRNAs (miR-548c-3p and miR-582-5p) and target genes (NR3C1, ABHD2, and GSK3B) as potential biomarkers for metastatic prostate cancers from large-scale gene expression data using systems biology approaches.

Role of Precision Oncology in Type II Endometrial and Prostate Cancers in the African Population: Global Cancer Genomics Disparities

Precision oncology can be defined as molecular profiling of tumors to identify targetable alterations. Emerging research reports the high mortality rates associated with type II endometrial cancer in black women and with prostate cancer in men of African ancestry. The lack of adequate genetic reference information from the African genome is one of the major obstacles in exploring the benefits of precision oncology in the African context. Whilst external factors such as the geography, environment, health-care access and socio-economic status may contribute greatly towards the disparities observed in type II endometrial and prostate cancers in black populations compared to Caucasians, the contribution of African ancestry to the contribution of genetics to the etiology of these cancers cannot be ignored. Non-coding RNAs (ncRNAs) continue to emerge as important regulators of gene expression and the key molecular pathways involved in tumorigenesis. Particular attention is focused on activated/repressed genes and associated pathways, while the redundant pathways (pathways that have the same outcome or activate the same downstream effectors) are often ignored. However, comprehensive evidence to understand the relationship between type II endometrial cancer, prostate cancer and African ancestry remains poorly understood. The sub-Saharan African (SSA) region has both the highest incidence and mortality of both type II endometrial and prostate cancers. Understanding how the entire transcriptomic landscape of these two reproductive cancers is regulated by ncRNAs in an African cohort may help elucidate the relationship between race and pathological disparities of these two diseases. This review focuses on global disparities in medicine, PCa and ECa. The role of precision oncology in PCa and ECa in the African population will also be discussed.

Identification of Germline Genetic Variants that Increase Prostate Cancer Risk and Influence Development of Aggressive Disease

Prostate cancer (PrCa) is a heterogeneous disease, which presents in individual patients across a diverse phenotypic spectrum ranging from indolent to fatal forms. No robust biomarkers are currently available to enable routine screening for PrCa or to distinguish clinically significant forms, therefore late stage identification of advanced disease and overdiagnosis plus overtreatment of insignificant disease both remain areas of concern in healthcare provision. PrCa has a substantial heritable component, and technological advances since the completion of the Human Genome Project have facilitated improved identification of inherited genetic factors influencing susceptibility to development of the disease within families and populations. These genetic markers hold promise to enable improved understanding of the biological mechanisms underpinning PrCa development, facilitate genetically informed PrCa screening programmes and guide appropriate treatment provision. However, insight remains largely lacking regarding many aspects of their manifestation; especially in relation to genes associated with aggressive phenotypes, risk factors in non-European populations and appropriate approaches to enable accurate stratification of higher and lower risk individuals. This review discusses the methodology used in the elucidation of genetic loci, genes and individual causal variants responsible for modulating PrCa susceptibility; the current state of understanding of the allelic spectrum contributing to PrCa risk; and prospective future translational applications of these discoveries in the developing eras of genomics and personalised medicine.

The Impact of African Ancestry on Prostate Cancer Disparities in the Era of Precision Medicine

Prostate cancer disproportionately affects men of African ancestry at nearly twice the rate of men of European ancestry despite the advancement of treatment strategies and prevention. In this review, we discuss the underlying causes of these disparities including genetics, environmental/behavioral, and social determinants of health while highlighting the implications and challenges that contribute to the stark underrepresentation of men of African ancestry in clinical trials and genetic research studies. Reducing prostate cancer disparities through the development of personalized medicine approaches based on genetics will require a holistic understanding of the complex interplay of non-genetic factors that disproportionately exacerbate the observed disparity between men of African and European ancestries.

Papillary Thyroid Carcinoma Variants are Characterized by Co-dysregulation of Immune and Cancer Associated Genes

Papillary thyroid carcinoma (PTC) variants exhibit different prognosis, but critical characteristics of PTC variants that contribute to differences in pathogenesis are not well-known. This study aims to characterize dysregulated immune-associated and cancer-associated genes in three PTC subtypes to explore how the interplay between cancer and immune processes causes differential prognosis. RNA-sequencing data from The Cancer Genome Atlas (TCGA) were used to identify dysregulated genes in each variant. The dysregulation profiles of the subtypes were compared using functional pathways clustering and correlations to relevant clinical variables, genomic alterations, and microRNA regulation. We discovered that the dysregulation profiles of classical PTC (CPTC) and the tall cell variant (TCPTC) are similar and are distinct from that of the follicular variant (FVPTC). However, unique cancer or immune-associated genes are associated with clinical variables for each subtype. Cancer-related genes MUC1, FN1, and S100-family members were the most clinically relevant in CPTC, while APLN and IL16, both immune-related, were clinically relevant in FVPTC. RAET-family members, also immune-related, were clinically relevant in TCPTC. Collectively, our data suggest that dysregulation of both cancer and immune associated genes defines the gene expression landscapes of PTC variants, but different cancer or immune related genes may drive the phenotype of each variant.

Upregulation and Overexpression of DVL1, the Human Counterpart of the Drosophila Dishevelled Gene, in Prostate Cancer

Aims and Background

The Wnt/beta-catenin signaling pathway is one of the main carcinogenic mechanisms in human malignancies including prostate cancer. Recently, the DVL1 gene was identified as a middle molecule of the Wnt/beta-catenin signaling pathway. In addition, alterations of the DVL1 gene have been reported in breast and cervical cancer. The abnormality of beta-catenin in prostate cancer has been well studied, so the examination of the DVL1 gene in prostate cancer is appealing.

Methods

We investigated DVL1 messenger RNA alterations by semiquantitative PCR (SQ-PCR) in 20 primary prostate cancers and assessed the protein expression by immunohistochemical analysis in the same samples. In addition, DVL1 and beta-catenin protein expression was evaluated with a new validated set of 20 prostate cancers.

Results

SQ-PCR revealed significant overexpression of DVL1 in prostate cancer (65%). Upregulation of the DVL1 gene product in prostate cancer was confirmed by immunostaining. With SQ-PCR and immunostaining, none of the cases showed underexpression or downregulation of DVL1. In addition, the data showed correlations between DVL1 mRNA and protein expression. Interestingly, the expression level of DVL1 increased with worsening histological grade. In addition, a correlation between DVL1 expression and beta-catenin expression was confirmed.

Conclusions

DVL1 was overexpressed in prostate cancer and its overexpression might be related to prostate cancer progression through the Wnt/beta-catenin pathway.

Prostate Cancer Disparities by Race and Ethnicity: From Nucleotide to Neighborhood

Prostate cancer (CaP) incidence, morbidity, and mortality rates vary substantially by race and ethnicity, with African American men experiencing among the highest CaP rates in the world. The causes of these disparities are multifactorial and complex, and likely involve differences in access to screening and treatment, exposure to CaP risk factors, variation in genomic susceptibility, and other biological factors. To date, the proportion of CaP that can be explained by environmental exposures is small and differences in the role factors play by race or ethnicity is poorly understood. In the absence of additional data, it is likely that environmental factors do not contribute greatly to CaP disparities. In contrast, CaP has one of the highest heritabilities of all major cancers and many CaP susceptibility genes have been identified. Some CaP loci, including the risk loci found at chromosome 8q24, have consistent effects in all racial/ethnic groups studied to date. However, replication of many susceptibility loci across race or ethnicity remains limited. It is likely that inequities in health care access strongly influences CaP disparities. CaP is a disease with a complex multifactorial etiology, and therefore any approach attempting to address racial/ethnic disparities in CaP must consider the many sources that influence risk, outcomes, and disparities.

Mice lacking have reduced signs of metabolic syndrome and non-alcoholic fatty liver disease

Metabolic syndrome (MetS) is a term used to characterize individuals having at least three of the following diseases: obesity, dyslipidemia, hyperglycemia, insulin resistance, hypertension, and nonalcoholic fatty liver disease (NAFLD). It is widespread, and the number of individuals with MetS is increasing. However, the events leading to the manifestation of MetS are not well-understood. Here, we show that loss of murine ARV1 (mARV1) results in resistance to acquiring diseases associated with MetS. Arv1^-/- animals fed a high-fat diet were resistant to diet-induced obesity, had lower blood cholesterol and triglyceride levels, and retained glucose tolerance and insulin sensitivity. Livers showed no gross morphological changes, contained lower levels of cholesterol, triglycerides, and fatty acids, and showed fewer signs of NAFLD. Knockout animals had elevated levels of liver farnesol X receptor (FXR) protein and its target, small heterodimer protein (SHP). They also had decreased levels of CYP7α1, CYP8β1, and mature SREBP1 protein, evidence suggesting that liver FXR signaling was activated. Strengthening this hypothesis was the fact that peroxisome proliferator-activating receptor α (PPARα) protein was elevated, along with its target, fibroblast growth factor 21 (FGF21). Arv1^-/- animals excreted more fecal cholesterol, free fatty acids, and bile acids. Their small intestines had 1) changes in bile acid composition, 2) an increase in the level of the intestinal FXR antagonist, tauromuricholic acid, and 3) showed signs of attenuated FXR signaling. Overall, we believe that ARV1 function is deleterious when consuming a high-fat diet. We further hypothesize that ARV1 is critical for initiating events required for the progression of diseases associated with MetS and NAFLD.

Endothelial Nitric Oxide Synthase Glu298Asp Polymorphism as a Risk Factor for Prostate Cancer

Background

The endothelial form of nitric oxide synthases (eNOS) seems to have an important role in vascular development, maintenance of the vascular tone and tumor growth in human prostate cancer (PC). The purpose of this study was to investigate the association between grade and stage of disease, age of diagnosis, vascular or perineural invasion, pre-diagnostic plasma prostate-specific antigen (PSA) levels, prostate cancer risk and Glu298Asp polymorphism of the eNOS gene.

Methods

Ninety-five prostate cancer patients and 111 benign prostate hyperplasia subjects were included. The Glu298Asp polymorphism of the eNOS gene was determined by polymerase chain reaction and restriction fragment length polymorphism

Results

The odds ratio (OR) between the GT and GG polymorphism was 0.76, indicating that the presence of the GT polymorphism decreased the risk of prostate cancer of more than 20% compared to the GG polymorphism. This difference, however, was not statistically significant. The GT polymorphism had an inverse association with cancer grade compared to the reference group (OR=0.47, p value=0.2).

Conclusions

These results suggest that prostate cancer development is not associated with the Glu298Asp polymorphism of the endothelial nitric oxide synthase gene in our population. Further studies in larger samples are needed to confirm our results and characterize the molecular mechanisms by which eNOS is involved in the susceptibility to prostate cancer.

Prostate Cancer Genetics: Variation by Race, Ethnicity, and Geography

Prostate cancer rates vary substantially by race, ethnicity, and geography. These disparities can be explained by variation in access to screening and treatment, variation in exposure to prostate cancer risk factors, and variation in the underlying biology of prostate carcinogenesis (including genomic propensity of some groups to develop biologically aggressive disease). It is clear that access to screening and access to treatment are critical influencing factors of prostate cancer rates; yet, even among geographically diverse populations with similar access to care (eg, low- and medium-income countries), African descent men have higher prostate cancer rates and poorer prognosis. To date, the proportion of prostate cancer that can be explained by environmental exposures is small, and the effect of these factors across different racial, ethnic, or geographical populations is poorly understood. In contrast, prostate cancer has one of the highest heritabilities of all major cancers. Numerous genetic susceptibility markers have been identified from family-based studies, candidate gene association studies, and genome-wide association studies. Some prostate cancer loci, including the risk loci found at chromosome 8q24, have consistent effects in all groups studied to date. However, replication of many susceptibility loci across race, ethnicity, and geography remains limited, and additional studies in certain populations (particularly in men of African descent) are needed to better understand the underlying genetic basis of prostate cancer.

Gene interference strategies as a new tool for the treatment of prostate cancer

Prostate cancer (PCa) is one of the most common cancer in men. It affects older men and the incidence increases with age; the median age at diagnosis is 67 years. The diagnosis of PCa is essentially based on three tools: digital rectal exam, serum concentration of prostate specific antigen, and transrectal ultrasound-guided biopsy. Currently, the therapeutic treatments of this cancer are different and range from the prostatectomy to hormonal therapy, to radiation therapy, to immunotherapy, and to chemotherapy. However, additional efforts are required in order to find new weapons for the treatment of metastatic setting of disease. The purpose of this review is to highlight new therapeutic strategies based on gene interference; in fact, numerous siRNA and miRNA in the therapeutic treatment of PCa are reported below.

Prostate cancer: germline prediction for a commonly variable malignancy

What's known on the subject? and What does the study add? Prostate cancer is a heterogeneous disease and biomarkers to predict its incidence and subsequent clinical behaviour are needed to tailor screening, prevention and therapeutic strategies. Rare mutations in genes such as BRCA1, BRCA2 and HOXB13 can affect prostate cancer incidence and/or clinical behaviour. Genome wide association studies (GWAS) have identified more common genetic variations that explain an estimated 20% of familial prostate cancer risk. In this review, we focus on the potential of germline genetic variation to provide biomarkers for prostate cancer screening, prevention and management. We discuss how germline genetics may have a role in treatment selection if reliable pharmacogenetic predictors of efficacy and toxicity can be identified. We have outlined possible mechanisms for including germline investigation in future prostate cancer clinical trials.

OBJECTIVES

• Prostate cancer is a heterogeneous disease and biomarkers to predict its incidence and subsequent clinical behaviour are needed to tailor screening, prevention and therapeutic strategies. • In this review we focus on the potential of germline genetic variation to provide these biomarkers.

METHODS

• We review the published literature on germline genetics in prostate cancer and examine the possibility of including germline genetic biomarkers in future prostate cancer clinical trials.

RESULTS

• Rare mutations in genes such as BRCA1, BRCA2 and HOXB13 can affect prostate cancer incidence and/or clinical behaviour. • Genome-wide association studies (GWAS) have identified more common genetic variations that explain an estimated 20% of familial prostate cancer risk. • Germline genetics may have a role in treatment selection, if reliable pharmacogenetic predictors of efficacy and toxicity can be identified.

CONCLUSION

• This rapidly emerging area of prostate cancer research may provide answers to current clinical conundrums in the prostate cancer treatment paradigm. We have outlined possible mechanisms for including germline investigation in future prostate cancer clinical trial design.

Genetic heterogeneity in Finnish hereditary prostate cancer using ordered subset analysis

Prostate cancer (PrCa) is the most common male cancer in developed countries and the second most common cause of cancer death after lung cancer. We recently reported a genome-wide linkage scan in 69 Finnish hereditary PrCa (HPC) families, which replicated the HPC9 locus on 17q21-q22 and identified a locus on 2q37. The aim of this study was to identify and to detect other loci linked to HPC. Here we used ordered subset analysis (OSA), conditioned on nonparametric linkage to these loci to detect other loci linked to HPC in subsets of families, but not the overall sample. We analyzed the families based on their evidence for linkage to chromosome 2, chromosome 17 and a maximum score using the strongest evidence of linkage from either of the two loci. Significant linkage to a 5-cM linkage interval with a peak OSA nonparametric allele-sharing LOD score of 4.876 on Xq26.3-q27 (ΔLOD=3.193, empirical P=0.009) was observed in a subset of 41 families weakly linked to 2q37, overlapping the HPCX1 locus. Two peaks that were novel to the analysis combining linkage evidence from both primary loci were identified; 18q12.1-q12.2 (OSA LOD=2.541, ΔLOD=1.651, P=0.03) and 22q11.1-q11.21 (OSA LOD=2.395, ΔLOD=2.36, P=0.006), which is close to HPC6. Using OSA allows us to find additional loci linked to HPC in subsets of families, and underlines the complex genetic heterogeneity of HPC even in highly aggregated families.

Analysis of Xq27-28 linkage in the international consortium for prostate cancer genetics (ICPCG) families

BACKGROUND

Genetic variants are likely to contribute to a portion of prostate cancer risk. Full elucidation of the genetic etiology of prostate cancer is difficult because of incomplete penetrance and genetic and phenotypic heterogeneity. Current evidence suggests that genetic linkage to prostate cancer has been found on several chromosomes including the X; however, identification of causative genes has been elusive.

METHODS

Parametric and non-parametric linkage analyses were performed using 26 microsatellite markers in each of 11 groups of multiple-case prostate cancer families from the International Consortium for Prostate Cancer Genetics (ICPCG). Meta-analyses of the resultant family-specific linkage statistics across the entire 1,323 families and in several predefined subsets were then performed.

RESULTS

Meta-analyses of linkage statistics resulted in a maximum parametric heterogeneity lod score (HLOD) of 1.28, and an allele-sharing lod score (LOD) of 2.0 in favor of linkage to Xq27-q28 at 138 cM. In subset analyses, families with average age at onset less than 65 years exhibited a maximum HLOD of 1.8 (at 138 cM) versus a maximum regional HLOD of only 0.32 in families with average age at onset of 65 years or older. Surprisingly, the subset of families with only 2-3 affected men and some evidence of male-to-male transmission of prostate cancer gave the strongest evidence of linkage to the region (HLOD = 3.24, 134 cM). For this subset, the HLOD was slightly increased (HLOD = 3.47 at 134 cM) when families used in the original published report of linkage to Xq27-28 were excluded.

CONCLUSIONS

Although there was not strong support for linkage to the Xq27-28 region in the complete set of families, the subset of families with earlier age at onset exhibited more evidence of linkage than families with later onset of disease. A subset of families with 2-3 affected individuals and with some evidence of male to male disease transmission showed stronger linkage signals. Our results suggest that the genetic basis for prostate cancer in our families is much more complex than a single susceptibility locus on the X chromosome, and that future explorations of the Xq27-28 region should focus on the subset of families identified here with the strongest evidence of linkage to this region.

The genetics of cancer risk

One hundred years ago, decades before the discovery of the structure of DNA, debate raged regarding how human traits were passed from one generation to the next. Phenotypes, including risk of disease, had long been recognized as having a familial component. Yet it was difficult to reconcile genetic segregation as described by Mendel with observations exhaustively documented by Karl Pearson and others regarding the normal distribution of human characteristics. In 1918, R. A. Fisher published his landmark article, "The Correlation Between Relatives on the Supposition of Mendelian Inheritance," bridging this divide and demonstrating that multiple alleles, all individually obeying Mendel's laws, account for the phenotypic variation observed in nature.Since that time, geneticists have sought to identify the link between genotype and phenotype. Trait-associated alleles vary in their frequency and degree of penetrance. Some minor alleles may approach a frequency of 50% in the human population, whereas others are present within only a few individuals. The spectrum for penetrance is similarly wide. These characteristics jointly determine the segregation pattern of a given trait, which, in turn, determine the method used to map the trait. Until recently, identification of rare, highly penetrant alleles was most practical. Revolutionary studies in genomics reported over the past decade have made interrogation of most of the spectrum of genetic variation feasible.The following article reviews recent discoveries in the genetic basis of inherited cancer risk and how these discoveries inform cancer biology and patient management. Although this article focuses on prostate cancer, the principles are generic for any cancer and, indeed, for any trait.

Genetics of prostate cancer risk

For decades, physicians and researchers have recognized that family history is a significant risk factor for prostate cancer. The identification of the genes responsible for inherited risk, however, proved difficult. With the sequencing of the human genome and the completion of the initial phases of the International HapMap Project, the tools are available to scan the entire genome and find genetic markers for disease. Since 2006, more than 30 inherited variants strongly associated with prostate cancer have been reported. As the inherited component of the disease is revealed, efforts are ongoing to translate genetic findings into the clinic.

Polymorphisms in mitochondrial genes and prostate cancer risk

The mitochondrion, conventionally thought to be an organelle specific to energy metabolism, is in fact multifunctional and implicated in many diseases, including cancer. To evaluate whether mitochondria-related genes are associated with increased risk for prostate cancer, we genotyped 24 single-nucleotide polymorphisms (SNP) within the mitochondrial genome and 376 tagSNPs localized to 78 nuclear-encoded mitochondrial genes. The tagSNPs were selected to achieve > or = 80% coverage based on linkage disequilibrium. We compared allele and haplotype frequencies in approximately 1,000 prostate cancer cases with approximately 500 population controls. An association with prostate cancer was not detected for any of the SNPs within the mitochondrial genome individually or for 10 mitochondrial common haplotypes when evaluated using a global score statistic. For the nuclear-encoded genes, none of the tagSNPs were significantly associated with prostate cancer after adjusting for multiple testing. Nonetheless, we evaluated unadjusted P values by comparing our results with those from the Cancer Genetic Markers of Susceptibility (CGEMS) phase I data set. Seven tagSNPs had unadjusted P < or = 0.05 in both our data and in CGEMS (two SNPs were identical and five were in strong linkage disequilibrium with CGEMS SNPs). These seven SNPs (rs17184211, rs4147684, rs4233367, rs2070902, rs3829037, rs7830235, and rs1203213) are located in genes MTRR, NDUFA9, NDUFS2, NDUFB9, and COX7A2, respectively. Five of the seven SNPs were further included in the CGEMS phase II study; however, none of the findings for these were replicated. Overall, these results suggest that polymorphisms in the mitochondrial genome and those in the nuclear-encoded mitochondrial genes evaluated are not substantial risk factors for prostate cancer.

Prognostic factors in patients with acute liver failure undergoing live donor liver transplantation

Mortality from acute liver failure (ALF) is high. Live donor liver transplantation (LDLT) is the treatment of choice for ALF in Asia, because cadaveric donors are rare. We sought to review our results in ALF patients with undergoing LDLT at our center. One hundred two LDLTs were performed at our center from April 2002 to November 2007, 15 (14%) because of ALF. Mean (SEM; median, range) follow-up was 1,065 (189; 1400; 3-2046) days. Nine patients (60%) had acute exacerbation of chronic hepatitis B; and 6 (40%) had drug-induced liver injury. Age was 47 (3; 50; 27-65) years. Ten patients (67%) were men. At transplantation, laboratory values were included bilirubin, 449 (35) micromol/L; creatinine concentration, 182 (32) mmol/L. The international normalized ratio was 2.4 (0.2). The Model for End-Stage Liver Disease (MELD) score was 34 (2). Both inpatient and long-term mortality was 20% 3 of 15 patients died. The 5-year survival was 80%. Compared with survivors, patients who died had a significantly higher creatinine concentration 289 vs 155 micromol/L, international normalized ratio (3.4 vs 2.1), MELD score (47 vs 32). We conclude that despite being sick with median and mean MELD scores of 32 and 34, 80% of patients with ALF can achieve good long-term survival after LDLT.

Evaluation of genetic variations in the androgen and estrogen metabolic pathways as risk factors for sporadic and familial prostate cancer

Previous studies suggest that enzymes involved in the androgen metabolic pathway are susceptibility factors for prostate cancer. Estrogen metabolites functioning as genotoxins have also been proposed as risk factors. In this study, we systematically tested the hypothesis that common genetic variations for those enzymes involved in the androgen and estrogen metabolic pathways increase risk for sporadic and familial prostate cancer. From these two pathways, 46 polymorphisms (34 single nucleotide polymorphisms, 10 short tandem repeat polymorphisms, and 2 null alleles) in 25 genes were tested for possible associations. Those genes tested included PRL, LHB, CYP11A1, HSD3B1, HSD3B2, HSD17B2, CYP17, SRD5A2, AKR1C3, UGT2B15, AR, SHBG, and KLK3 from the androgen pathway and CYP19, HSD17B1, CYP1A1, CYP1A2, CYP1B1, COMT, GSTP1, GSTT1, GSTM1, NQO1, ESR1, and ESR2 from the estrogen pathway. A case-control study design was used with two sets of cases: familial cases with a strong prostate cancer family history (n = 438 from 178 families) and sporadic cases with a negative prostate cancer family history (n = 499). The controls (n = 493) were derived from a population-based collection. Our results provide suggestive findings for an association with either familial or sporadic prostate cancer with polymorphisms in four genes: AKR1C3, HSD17B1, NQO1, and GSTT1. Additional suggestive findings for an association with clinical variables (disease stage, grade, and/or node status) were observed for single nucleotide polymorphisms in eight genes: HSD3B2, SRD5A2, SHBG, ESR1, CYP1A1, CYP1B1, GSTT1, and NQO1. However, none of the findings were statistically significant after appropriate corrections for multiple comparisons. Given that the point estimates for the odds ratio for each of these polymorphisms are <2.0, much larger sample sizes will be required for confirmation.

Molecular biology of prostate-cancer pathogenesis

PURPOSE OF REVIEW

The genetic and molecular basis of prostate-cancer pathogenesis is reviewed.

RECENT FINDINGS

Several genetic loci have been found that are associated with hereditary predisposition to prostate cancer, but they account for a small fraction of all cases. A number of suppressor genes have been identified that are activated by either complete or partial genetic loss in sporadic prostate cancer. Chromosomal translocation results in transcriptional activation of truncated ETS transcription factors ERG and ETV1, the first candidates for dominant oncogenes for prostate cancer. Lastly, the androgen receptor is active throughout the course of prostate cancer and, in androgen-independent prostate cancer, takes on the role of a dominant oncogene as the target of gene amplification, overexpression, and the activation of mutations.

SUMMARY

Genetic lesions responsible for familial and sporadic prostate cancer are being revealed and they suggest that prostate cancer often initiates owing to an increased susceptibility to oxidative damage; it then progresses by affecting transcription factors, the PI3 kinase pathway, and other growth stimulatory pathways. The final common pathway after androgen ablation appears to be activation of androgen receptor.

Description of the International Consortium For Prostate Cancer Genetics, and failure to replicate linkage of hereditary prostate cancer to 20q13

The International Consortium for Prostate Cancer Genetics (ICPCG) is an international collaborative effort to pool pedigrees with hereditary prostate cancer (PC) in order to replicate linkage findings for PC. A strength of the ICPCG is the large number of well-characterized pedigrees, allowing linkage analyses within large subsets. Given the heterogeneity and complexity of PC, the historical difficulties of synthesizing different studies reporting positive and negative linkage replication, and the use of different statistical analysis methods and different stratification criteria, the ICPCG provides a valuable resource to evaluate linkage for hereditary PC. To date, linkage of chromosome 20 (HPC20) to hereditary PC has been one of the strongest linkage signals, yet the efforts to replicate this linkage have been limited. This paper reports a linkage analysis of chromosome 20 markers for 1,234 pedigrees with multiple cases of PC ascertained through the ICPCG, and represents the most thorough attempt to confirm or refute linkage to chromosome 20. From the original 158 Mayo pedigrees in which linkage was detected, the maximum heterogeneity LOD (HLOD) score, under a recessive model, was 2.78. In contrast, for the 1,076 pedigrees not included in the original study, the maximum HLOD score (recessive model) was 0.06. Although, a few small linkage signals for chromosome 20 were found in various strata of this pooled analysis, this large study failed to replicate linkage to HPC20. This study illustrates the value of the ICPCG family collection to evaluate reported linkage signals and suggests that the HPC20 region does not make a major contribution to PC susceptibility.

Finding prostate cancer susceptibility genes

Prostate cancer is a heterogeneous disease with multiple loci contributing to susceptibility. Traditionally, genome-wide scans using high-risk families have utilized stratification by number of affected individuals, family history of other cancers, or family age at diagnosis to improve genetic homogeneity. In addition to locus heterogeneity, for later onset diseases such as prostate cancer, a major limitation to mapping efforts is that key parental DNA samples are rarely available. The lack of available samples from upper generations reduces inheritance information, and as a result, the standard 10-cM genome scan does not provide full power to detect linkage. To increase the ability to find disease-associated loci, much denser genome-wide scans must be undertaken in multiple ethnic groups. In addition, new ways of defining homogenous subsets of families need to be developed.

Unravelling the genetics of prostate cancer

This review describes what is currently known about the genetics of prostate cancer. Traditionally, the genetics of a suspected inherited cancer predisposition have generally been thought of in terms of a single, high-risk gene with a dominant mode of inheritance. Such a gene might be observed in families, as has been documented in familial breast cancer (BRCA1/2), familial colorectal cancer (HNPCC), retinoblastoma (RB1), and Wilms tumor (WT1). This review investigates the evidence for the existence, first of familial prostate cancer, and second, for the presence of such a high-risk gene in those families by epidemiological and experimental approaches. Another current area of interest in prostate cancer is the investigation of the contribution of common lower penetrance genes to the disease. This alternative approach has become popular, as it raises the issue of frequently seen genetic variations such as single nucleotide polymorphisms (SNPs) having relevance to the risk of developing the disease. Finally, this article will explore the way forward, with emphasis on worldwide collaboration from teams attempting to find the genes responsible for the disease and investment in new technologies that will aid in their discovery.

The clinical genetics of prostate cancer

Prostate cancer is the most common cancer in men and the second highest cause of cancer-related mortality in the U.K. A genetic component in predisposition to prostate cancer has been recognized for decades. One of the strongest epidemiological risk factors for prostate cancer is a positive family history. The hunt for the genes that predispose to prostate cancer in families has been the focus of many research groups worldwide for the past 10 years. Both epidemiological and twin studies support a role for genetic predisposition to prostate cancer. Familial cancer loci have been found, but the genes that cause familial prostate cancer remain largely elusive. Unravelling the genetics of prostate cancer is challenging and is likely to involve the analysis of numerous predisposition genes. Current evidence supports the hypothesis that excess familial risk of prostate cancer could be due to the inheritance of multiple moderate-risk genetic variants. Although research on hereditary prostate cancer has improved our knowledge of the genetic aetiology of the disease, a lot of questions still remain unanswered.

This article explores the current evidence that there is a genetic component to the aetiology of prostate cancer and attempts to put into context the diverse findings that have been shown to be possibly associated with the development of hereditary prostate cancer. Linkage searches over the last decade are summarised. It explores issues as to why understanding the genetics of prostate cancer has been so difficult and why despite this, it is still a major focus of research. Finally, current and future management strategies of men with Hereditary Prostate Cancer (HPC) are discussed.

Environmental, genetic, and molecular features of prostate cancer

Prostate cancer is the sixth most common cancer in the world and the third leading cause of cancer in men. The increase in the understanding of prostate carcinogenesis over the past 15 years has helped to define crucial steps in the natural history of the disease, namely initiation and progression to androgen independence. This heterogeneous disease encompasses a range of environmental and familial factors, which provides strong support for the use of chemopreventive strategies. Most patients with advanced prostate cancer are treated with androgen-deprivation therapy, which leads to a striking regression of androgen-responsive cancer cells. A transition from an androgen-responsive to an androgen-unresponsive stage is seen during the clinical course in almost all patients with prostate cancer. This transition also signals a substantial worsening of prognosis. Here, we review the most important findings in prostate carcinogenesis and the molecular anomalies associated with the androgen-refractory stage.

Hereditary prostate cancer in African American families: linkage analysis using markers that map to five candidate susceptibility loci

African American men have the highest incidence of prostate cancer in the world. Despite this statistic, linkage studies designed to localise prostate cancer susceptibility alleles have included primarily men of Caucasian descent. In this report, we performed a linkage analysis using 33 African American prostate cancer families from two independent research groups. In total, 126 individuals (including 89 men with prostate cancer) were genotyped using markers that map to five prostate cancer susceptibility loci, namely HPC1 at 1q24–25, PCAP at 1q42.2–43, CAPB at 1p36, HPC20 on chromosome 20, and HPCX at Xq27–28. Multipoint mode-of-inheritance-free linkage analyses were performed using the GENEHUNTER software. Some evidence of prostate cancer was detected to HPC1 using all families with a maximum NPL Z score of 1.12 near marker D1S413 (P=0.13). Increased evidence of linkage was observed in the 24 families with prostate cancer diagnosis prior to age 65 years and in the 20 families with male-to-male transmission. Some evidence of prostate cancer linkage was also detected at markers mapping to PCAP, HPC20, and HPCX. Continued collection and analysis of African American prostate cancer families will lead to an improved understanding of inherited susceptibility in this high-risk group.

Identification of a prostate cancer susceptibility locus on chromosome 7q11-21 in Jewish families

Results from over a dozen prostate cancer susceptibility genome-wide scans, encompassing some 1,500 hereditary prostate cancer families, indicate that prostate cancer is an extremely heterogeneous disease with multiple loci contributing to overall susceptibility. In an attempt to reduce locus heterogeneity, we performed a genomewide linkage scan for prostate cancer susceptibility genes with 36 Jewish families, which represent a stratification of hereditary prostate cancer families with potentially increased locus homogeneity. The 36 Jewish families represent a combined dataset of 17 Jewish families from the Fred Hutchinson Cancer Research Center-based Prostate Cancer Genetic Research Study dataset and 19 Ashkenazi Jewish families collected at Johns Hopkins University. All available family members, including 94 affected men, were genotyped at markers distributed across the genome with an average interval of <10 centimorgans. Nonparametric multipoint linkage analyses were the primary approach, although parametric analyses were performed as well. Our strongest signal was a significant linkage peak at 7q11-21, with a nonparametric linkage (NPL) score of 3.01 (P = 0.0013). Simulations indicated that this corresponds to a genomewide empirical P = 0.006. All other regions had NPL P values >/=0.02. After genotyping additional markers within the 7q11-21 peak, the NPL score increased to 3.35 (P = 0.0004) at D7S634 with an allele-sharing logarithm of odds of 3.12 (P = 0.00007). These studies highlight the utility of analyzing defined sets of families with a common origin for reducing locus heterogeneity problems associated with studying complex traits.

Populations at high risk for prostate cancer

Although prostate cancer tends to be a slow-growing neoplasm affecting older men, there is clearly a subset of patients at high risk for developing early and possibly more aggressive disease. This group of high-risk patients includes men with a family history of prostate cancer and various histologic features such as PIN and ASAP identified on an initial biopsy. Black American men have a much higher risk of developing prostate cancer when compared with white men and especially Asian men. This finding may reflect both genetic and environmental factors. Screening men at increased risk of developing prostate cancer appears to be a logical strategy, especially in light of recent reports that suggest a benefit to aggressive treatment.

Results of a genome-wide linkage analysis in prostate cancer families ascertained through the ACTANE consortium

BACKGROUND

The aggregation of prostate cancer within families suggests a major inherited component to the disease. Genetic linkage studies have identified several chromosomal regions that may contain prostate cancer susceptibility loci, but none has been definitively implicated.

METHODS

We performed a genome-wide linkage search based on 64 families, 63 with at least 3 cases of prostate cancer, ascertained in five countries. The majority of cases from these centers presented with clinically detected disease. Four hundred and one polymorphic markers were typed in 268 individuals. Multipoint heterogeneity analysis was conducted under three models of susceptibility; non-parametric analyses were also performed.

RESULTS

Some weak evidence of linkage, under at least one of the genetic models, was observed to markers on chromosomes 2 (heterogeneity LOD (HLOD) = 1.15, P = 0.021), 3 (HLOD = 1.25, P = 0.016), 4 (HLOD = 1.28, P = 0.015), 5 (HLOD = 1.20, P = 0.019), 6 (HLOD = 1.41, P = 0.011), and 11 (HLOD = 1.24, P = 0.018), and in two regions on chromosome 18 (HLOD = 1.40, P = 0.011 and HLOD = 1.34, P = 0.013). There were no HLOD scores greater than 1.5 under any model, and no locus would be predicted to explain more than half of the genetic effect. No evidence in favor of linkage to previously suggested regions on chromosomes 1, 8, 17, 20, or X was found.

CONCLUSIONS

Genetic susceptibility to prostate cancer is likely to be controlled by many loci, with no single gene explaining a large fraction of the familial risk. Pooling of results from all available genome scans is likely to be required to obtain definitive linkage results.

Genome linkage screen for prostate cancer susceptibility loci: results from the Mayo Clinic Familial Prostate Cancer Study

Prostate cancer is one of the most common cancers among men and has long been recognized to occur in familial clusters. Brothers and sons of affected men have a twofold to threefold increased risk of developing prostate cancer. However, identification of genetic susceptibility loci for prostate cancer has been extremely difficult. Several putative loci identified by genetic linkage have been reported to exist on chromosomes 1 (HPC1, PCAP, and CAPB), X (HPCX), 17 (HPC2), and 20 (HPC20), with genes RNASEL (HPC1) and ELAC2 (HPC2) tentatively defined. In this study, we report our genome linkage scan in 160 prostate cancer families, using the ABI Prism Linkage Mapping Set Version 2 with 402 microsatellite markers. The most significant linkage was found for chromosome 20, with a recessive model heterogeneity LOD score (HLOD) of 4.77, and a model-free LOD score (LOD - ZLR) of 3.46 for the entire group of pedigrees. Linkage for chromosome 20 was most prominent among families with a late age of diagnosis (average age at diagnosis >/= 66 years; maximum LOD - ZLR = 2.82), with <5 affected family members (LOD - ZLR = 3.02), with presence of hereditary prostate cancer (LOD - ZLR = 2.81), or with no male-to-male transmission of disease (LOD - ZLR = 3.84). No other chromosome showed significant evidence for linkage. However, chromosomes 6 and X showed suggestive results, with maximum LOD - ZLR values of 1.38 and 1.36, respectively. Subset analyses suggest additional chromosomal regions worth further follow-up.

Genome-wide scan for linkage in finnish hereditary prostate cancer (HPC) families identifies novel susceptibility loci at 11q14 and 3p25-26

BACKGROUND

In order to identify predisposition loci to hereditary prostate cancer (HPC), we performed a genome-wide linkage analysis using samples from a genetically homogeneous population, with 13 Finnish multiplex prostate cancer families.

METHODS

Altogether 87 DNA samples were genotyped from 13 families. Logarithm-of-odds (LOD) scores were calculated for all autosomes using FASTLINK and GENEHUNTER designating all unaffected men and all women as unknown.

RESULTS

The highest LOD scores in the affected-only analyses were found at 11q14, where the two-point LOD score was 2.97 (theta = 0.0 at D11S901), GENEHUNTER heterogeneity LOD (HLOD) of 3.36, and a non-parametric-linkage (NPL) score of 2.67 (P = 0.008). A second positive site was at 3p25-26, with a two-point LOD score of 2.57 (theta = 0.01 at D3S1297), HLOD of 2.15, and NPL score of 2.27 (P = 0.02).

CONCLUSIONS

The results suggest two HPC regions in the Finnish population, which have not been reported previously and warrant further study.

The molecular genetics of prostate cancer

The molecular genetics of prostate cancer, the second most common cause of cancer-related death in men, is poorly understood. Inherited factors are believed to account for 42% of the risk of prostate cancer, and although multiple chromosomal loci of susceptibility have been identified, the target genes for these loci have not been well defined. Its heterogeneous nature suggests that the predisposition to prostate cancer may involve multiple genes and variable phenotypic expression. Genes that have been found to play a role in progression of prostate cancer include GSTP1 and PTEN, as well as the androgen receptor (AR) gene. Evidence suggests that the AR signaling pathway can be activated by other ligands when androgen levels are low. Recent findings have also implicated Kruppel-like factor 6 (KFL6), E-cadherin, the p40 subunit of eukaryotic translation initiation factor (eIF3-p40), and Elongin C, but confirmatory evidence is required to clarify the roles of these factors. Technologic advances, such as complementary DNA and tissue microarrays, have facilitated identification of genetic alterations and investigations of their function, but improved tools for searching and analyzing genes are still needed.

Oligogenic segregation analysis of hereditary prostate cancer pedigrees: evidence for multiple loci affecting age at onset

Previous studies have suggested strong evidence for a hereditary component to prostate cancer (PC) susceptibility. Here, we analyze 3,796 individuals in 263 PC families recruited as part of the ongoing Prostate Cancer Genetic Research Study (PROGRESS). We use Markov chain Monte Carlo (MCMC) oligogenic segregation analysis to estimate the number of quantitative trait loci (QTLs) and their contribution to the variance in age at onset of hereditary PC (HPC). We estimate 2 covariate effects: diagnosis of PC before and after prostate-specific antigen (PSA) test availability, and presence/absence of at least 1 blood relative with primary neuroepithelial brain cancer (BC). We find evidence that 2 to 3 QTLs contribute to the variance in age at onset of HPC. The 2 QTLs with the largest contribution to the total variance are both effectively dominant loci. We find that the covariate for diagnosis before and after PSA test availability is important. Our findings for the number of QTLs contributing to HPC and the variance contribution of these QTLs will be instructive in mapping and identifying these genes.

Searching for the gatekeeper oncogene of prostate cancer

Prostate cancer is a common malignancy that has a heterogeneous etiology and a variable outcome. Nearly all prostatic adenocarcinoma results from androgen-dependent tumor promotion. However, the cause of prostate cancer initiation is not well understood and only a few of the target oncogenes activated during prostate cancer initiation have been identified. Prostate cancer risk is strongly influenced by family history. Several genetic loci have been found to cosegregate with prostate cancer occurrence in high-risk families. Some candidate oncogenes that map to these loci have been implicated by the identification of mutations in high-risk kindreds. However, the roles of the putative oncogene products in the biochemical pathways that mediate carcinogenesis remain obscure and their influence on cancer etiology has yet to be supported by gene targeting experiments in mice. Moreover, the genes that have been implicated in hereditary prostate cancers do not appear to be mutated in sporadic cancers. Karyotypic and loss of heterozygosity analysis of sporadic prostate cancers have identified 8p, 10q, and 17p as the loci most often disrupted. Candidate oncogenes have been identified at each of these regions. Additional genes with pathogenic significance in prostate cancer have been identified by analysis of cDNA microarrays comparing benign and malignant prostate tissue, by differential genetic analysis of benign and malignant prostatic epithelium, and by induction of experimental prostate cancer in genetically engineered mice.

Age specific and attributable risks of familial prostate carcinoma from the family-cancer database

BACKGROUND

Familial risks by proband status and age are useful for clinical counseling, and they can be used to calculate population-attributable fractions (PAFs), which show the proportion of disease that could be prevented if the cause could be removed.

METHODS

The authors used the nationwide Swedish Family-Cancer Database on 10.2 million individuals and 182,104 fathers and 3710 sons with medically verified prostate carcinoma to calculate age specific familial standardized incidence ratios (SIRs) with 95% confidence intervals (95%CI) and familial PAFs for prostate carcinoma in sons ages 0-66 years.

RESULTS

The incidence of prostate carcinoma was doubled between the years 1961 and 1998. The familial SIRs for prostate carcinoma were 2.38 (95%CI, 2.18-2.59) for men with prostate carcinoma in the father only, 3.75 (95%CI, 2.73-4.95) for men with prostate carcinoma in a brother only, and 9.44 (95%CI, 5.76-14.03) for men with prostate carcinoma in both a father and a brother. The corresponding familial PAFs were 8.86%, 1.78%, and 0.99%, respectively, yielding a total PAF of 11.63%. Age specific risks were shown for the same proband histories. The SIR was 8.05 for prostate carcinoma before age 55 if a brother had been diagnosed before that age. If, in addition, a father was diagnosed at any age, then the SIR was 33.09.

CONCLUSIONS

The authors recommend that having a brother who is diagnosed with prostate carcinoma before age 55 years or having a brother and father who are diagnosed at any age are indications to screen for prostate carcinoma. The familial PAF of prostate carcinoma among a population of sons ages 0-66 years was 11.63%.

Hereditary prostate cancer: clinical aspects

PURPOSE

We review the current epidemiological and genetic knowledge regarding hereditary prostate cancer, and outline its clinical implications.

MATERIALS AND METHODS

Published articles on hereditary prostate cancer were identified using the MEDLINE data base.

RESULTS

A risk of prostate cancer, particularly early onset disease, is strongly affected by family history (number of relatives with prostate cancer and their age at diagnosis). A family history of prostate cancer increases the positive predictive value of prostate specific antigen testing and, hence, heredity should always be assessed when deciding whether to perform biopsies in a man with a prostate specific antigen level of 3 to 10 ng./ml. Epidemiological studies indicate that dominantly inherited susceptibility genes with high penetrance cause 5% to 10% of all prostate cancer cases, and as much as 30% to 40% of early onset disease. More than a half dozen chromosome loci that may comprise such genes have been mapped, but as of May 2002 no prostate cancer susceptibility gene of major importance had been cloned. Most likely, environmental factors and comparatively common variants of several other genes affect prostate cancer risk in families with or without multiple cases of the disease. On average, hereditary prostate cancer is diagnosed 6 to 7 years earlier than sporadic prostate cancer, but does not otherwise differ clinically from the sporadic form. As a consequence of the earlier onset, a greater proportion of men with hereditary prostate cancer die of the disease than those with nonhereditary prostate cancer. At present, the only clinically applicable measure to reduce prostate cancer mortality in families with hereditary disease is screening, with the aim of diagnosing the disease when it is still in a curable stage.

CONCLUSIONS

Hereditary susceptibility is now considered the strongest risk factor for prostate cancer and has profound clinical importance. The genetic mechanism behind such susceptibility has turned out to be more complex than initially thought, and will probably not be completely understood for many years to come.

Hormones and prostate cancer: current perspectives and future directions

Prostate cancer is the most commonly diagnosed non-skin cancer in men in most western countries. Despite the high morbidity and mortality from prostate cancer, its etiology remains obscure. Although compelling laboratory data suggest a role for androgens in prostate carcinogenesis, most epidemiologic data on humans are inconclusive. To provide insights and directions for future epidemiologic research on hormones and prostate cancer, this review focuses on current perspectives of serum-based studies and polymorphisms in relevant hormone-related genes. We highlight the importance of methodologic studies and investigations of hormone levels in the prostatic tissue to help clarify the often-contradictory data on serologic studies. We recommend careful analysis and cautious interpretation of studies of genetic markers, including repeats and single nucleotide polymorphisms (SNPs), as false positive and negative results may arise in many current and future studies with limited statistical power and non-representative samples from the population. The review also highlights the reasons to perform functional analyses of SNPs, a critical and often under-appreciated component of molecular epidemiologic investigations. The time is ripe for large-scale multidisciplinary investigations that incorporate molecular genetics, biochemistry, histopathology, and endocrinology into traditional epidemiologic studies. Such collaboration will lead to a deeper understanding of the etiologic pathways of prostate cancer, ultimately yielding better preventive, diagnostic, and therapeutic strategies.

Perspective: prostate cancer susceptibility genes

In many developed countries, prostate cancer is the most frequently diagnosed malignancy in men. The extent to which the marked racial/ethnic difference in its incidence rate is attributable to screening methods, environmental, hormonal, and/or genetic factors remains unknown. A positive family history is among the strongest epidemiological risk factors for prostate cancer. It is now well recognized that association of candidate genetic markers to this multifactorial malignancy is more difficult than the identification of susceptibility genes for some common cancers such as breast, ovary, and colon cancer. Several reasons may explain such a difficulty: 1) prostate cancer is diagnosed at a late age, thus often making it impossible to obtain DNA samples from living affected men for more than one generation; 2) the presence within high-risk pedigrees of phenocopies, associated with the lack of distinguishing features between hereditary and sporadic forms; and 3) the genetic heterogeneity of this complex disease along with the accompanying difficulty of developing appropriate statistical transmission models taking into account simultaneously multiple susceptibility genes, frequently showing moderate or low penetrance. Despite the localization of seven susceptibility loci, there has been limited confirmatory evidence of linkage for currently known candidate genes. Nonetheless, the discovery of the first prostate cancer susceptibility gene characterized by positional cloning, ELAC2 was achieved taking advantage of the Utah Family Resource. Moreover, common missense mutations in the ELAC2 gene were found to be significantly associated with an increased risk of diagnosis of prostate cancer in some studies. More recently, recombination map-ping and candidate gene analysis were used to map several genes, including the 2'-5'-oligoadenylate-dependent ribonuclease L (RNASEL) gene, to the critical region of HPC1. Two deleterious mutations in RNASEL segregate independently with the disease in two of the eight HPC1-linked families. Additional studies using larger cohorts are needed to fully evaluate the role of these two susceptibility genes in prostate cancer risk. Although a number of rare highly penetrant loci contribute to the Mendelian inheritance of prostate cancer, some of the familial risks may be due to shared environment and more specifically to common low-penetrance genetic variants. In this regard, it is not surprising that analyses of genes encoding key proteins involved in androgen biosynthesis and action, led to the observation of a significant association between a susceptibility to prostate cancer and common genetic variants, such as those found in 5alpha-reductase type 2 and AR genes.

A review of genetic polymorphisms and prostate cancer risk

In this study, we review a variety of genetic polymorphisms that may have an etiologic role in prostate cancer. We include associations identified in molecular epidemiology studies and the consistency of findings reported to date. Suggestions for further research are also offered. For the purposes of this review, we identified relevant articles through a MEDLINE search for the period of January 1987 through March 2001. The searches were limited to articles published in English. Medical subject headings were used to scan titles, abstracts, and subject headings in the databases using the keywords "prostate neoplasms," "genetics," and "polymorphisms."

Linkage and association of CYP17 gene in hereditary and sporadic prostate cancer

Androgens are essential for prostate development, growth and maintenance and the association between androgen levels and prostate cancer is well established. Since the CYP17 gene encodes the enzyme cytochrome P450c17alpha, which mediates 17alpha-hydroxylase and 17,20-lyase activities in the androgen biosynthesis pathway, sequence variations in the gene and association with increased risk to prostate cancer has been studied. In particular, several groups have studied the association between a polymorphism in the 5' promoter region and prostate cancer using a population-based association approach. However, the results from these studies were inconclusive. To further study this polymorphism and its possible role in hereditary prostate cancer (HPC), we performed a genetic linkage analysis and family-based association analysis in 159 families, each of which contains at least 3 first-degree relatives with prostate cancer. In addition, we performed a population-based association analysis to compare the risk of this polymorphism to hereditary and sporadic prostate cancer in 159 HPC probands, 249 sporadic prostate cancer patients and 211 unaffected control subjects. Evidence for linkage at the CYP17 gene region was found in the total 159 HPC families (LOD = 1.3, p = 0.01, at marker D10S222). However, family-based association tests did not provide evidence for overtransmission of either allele of the CYP17 polymorphism to affected individuals in the HPC families. The allele and genotype frequencies of the polymorphism were not statistically different among the HPC probands, sporadic cases and unaffected control subjects. In conclusion, our results suggest that the CYP17 gene or other genes in the region may increase the susceptibility to prostate cancer in men; however, the polymorphism in the 5' promoter region has a minor role if any in increasing prostate cancer susceptibility in our study sample.

A genome screen of families with multiple cases of prostate cancer: evidence of genetic heterogeneity

We conducted a genomewide screen for prostate cancer-susceptibility genes on the basis of data from 98 families from the United States and Canada that had three or more verified diagnoses of prostate cancer among first- and second-degree relatives. We found a statistically significant excess of markers for which affected relatives exhibited modest amounts of excess allele-sharing; however, no single chromosomal region contained markers with excess allele-sharing of sufficient magnitude to indicate unequivocal evidence of linkage. Positive linkage signals of nominal statistical significance were found in two regions (5p-q and 12p) that have been identified as weakly positive in other data sets and in region 19p, which has not been identified previously. All these signals were considerably stronger for analyses restricted to families with mean age at onset below the median than for analyses of families with mean age at onset above the median. The data provided little support for any of the putative prostate cancer-susceptibility genes identified in other linkage studies.

Model-free linkage analysis with covariates confirms linkage of prostate cancer to chromosomes 1 and 4

As with many complex genetic diseases, genome scans for prostate cancer have given conflicting results, often failing to provide replication of previous findings. One factor contributing to the lack of consistency across studies is locus heterogeneity, which can weaken or even eliminate evidence for linkage that is present only in a subset of families. Currently, most analyses either fail to account for locus heterogeneity or attempt to account for it only by partitioning data sets into smaller and smaller portions. In the present study, we model locus heterogeneity among affected sib pairs with prostate cancer by including covariates in the linkage analysis that serve as surrogate measures of between-family linkage differences. The model is a modification of the Olson conditional logistic model for affected relative pairs. By including Gleason score, age at onset, male-to-male transmission, and/or number of affected first-degree family members as covariates, we detected linkage near three locations that were previously identified by linkage (1q24-25 [HPC1; LOD score 3.25, P=.00012], 1q42.2-43 [PCAP; LOD score 2.84, P=.0030], and 4q [LOD score 2.80, P=.00038]), near the androgen-receptor locus on Xq12-13 (AR; LOD score 3.06, P=.00053), and at five new locations (LOD score > 2.5). Without covariates, only a few weak-to-moderate linkage signals were found, none of which replicate findings of previous genome scans. We conclude that covariate-based linkage analysis greatly improves the likelihood that linked regions will be found by incorporation of information about heterogeneity within the sample.

Evaluation of linkage and association of HPC2/ELAC2 in patients with familial or sporadic prostate cancer

To investigate the relationship between HPC2/ELAC2 and prostate cancer risk, we performed the following analyses: (1) a linkage study of six markers in and around the HPC2/ELAC2 gene at 17p11 in 159 pedigrees with hereditary prostate cancer (HPC); (2) a mutation-screening analysis of all coding exons of the gene in 93 probands with HPC; (3) family-based and population-based association study of common HPC2/ELAC2 missense variants in 159 probands with HPC, 249 patients with sporadic prostate cancer, and 222 unaffected male control subjects. No evidence for linkage was found in the total sample, nor in any subset of pedigrees based on characteristics that included age at onset, number of affected members, male-to-male disease transmission, or race. Furthermore, only the two previously reported missense changes (Ser217Leu and Ala541Thr) were identified by mutational analysis of all HPC2/ELAC exons in 93 probands with HPC. In association analyses, family-based tests did not reveal excess transmission of the Leu217 and/or Thr541 alleles to affected offspring, and population-based tests failed to reveal any statistically significant difference in the allele frequencies of the two polymorphisms between patients with prostate cancer and control subjects. The results of this study lead us to reject the three alternative hypotheses of (1) a highly penetrant, major prostate cancer-susceptibility gene at 17p11, (2) the allelic variants Leu217 or Thr541 of HPC2/ELAC2 as high-penetrance mutations, and (3) the variants Leu217 or Thr541 as low-penetrance, risk-modifying alleles. However, we did observe a trend of higher Leu217 homozygous carrier rates in patients than in control subjects. Considering the impact of genetic heterogeneity, phenocopies, and incomplete penetrance on the linkage and association studies of prostate cancer and on the power to detect linkage and association in our study sample, our results cannot rule out the possibility of a highly penetrant prostate cancer gene at this locus that only segregates in a small number of pedigrees. Nor can we rule out a prostate cancer-modifier gene that confers a lower-than-reported risk. Additional larger studies are needed to more fully evaluate the role of this gene in prostate cancer risk.

Molecular genetics of prostate cancer

The molecular mechanisms underlying the development and progression of prostate cancer are poorly understood. Epidemiological studies have suggested that 5-10% of all prostate cancers are familial, and numerous chromosomal loci have been associated with prostate cancer in multicentre linkage studies. However, no putative susceptibility genes harboured in these chromosomal regions have thus far been identified. Several recurrent chromosomal alterations in prostate cancer have been detected in comparative genomic hybridization (CGH) and loss of heterozygosity (LOH) analysis. The target genes for many of these aberrations are still not known. It seems that the androgen receptor (AR) signalling pathway plays a crucial role in both early development as well as in late progression of the disease. Both germ-line and somatic genetic alterations in the AR gene have been demonstrated in prostate cancer patients. The intention of this review is to summarize the current knowledge of molecular mechanisms in the development of prostate cancer.

Heterogeneity in genetic susceptibility to prostate cancer

The incidence of prostate cancer is related to aging. Its increase in the last 10 years, varies from country to country and according to ethnic group, with its greatest incidence among African-American males and the least among Asian males. Only two risk factors have thus far been clearly established for prostate cancer: familial aggregation and ethnic origin. No dietary or environmental cause has yet been identified for prostate cancer. However, some variations in endogenous factors, such as sex steroids or IGF1 circulating levels, may partly explain differences in risk observed between different populations. Genetic polymorphisms of genes encoding for 5alpha-reductase, androgen receptor, or vitamin D receptor have been associated with different degrees of risk for prostate cancer and may explain variations in risk among ethnic groups or within geographic areas. Different studies support the theory that familial prostate cancer may be hereditary and not due to a similar lifestyle. Thus, familial inheritance is a parameter that must be considered when advising screening in high-risk families. Indeed, the relative risk for first-degree relatives of prostate cancer patients can reach 2, 5 and 11 when, respectively, 1, 2 and 3 first-degree relatives are affected. Some familial forms appear to be associated with transmission of a rare, putative, autosomal dominant gene (0.003-0.06 allele frequency) with a high penetrance (88% at age 85). Using this transmission model and linkage analysis, three predisposing loci on chromosome 1: HPC-1 (hereditary prostate cancer 1: 1q24-25), PCaP (predisposing for prostate cancer: 1q42-43) and CAPB (predisposing for prostate and brain tumor: 1p36) and one locus on chromosome 20 (HPC20: 20q13) have been described. Moreover, X-linked transmission has been suggested and related to another predisposing gene locus: HPCX (Xq27-28). It is possible that a large proportion of familial prostate cancer is due not to segregation of a few major gene mutations transmitted according to a monogenic inheritance, but rather to familial sharing of alleles at many loci, each contributing to a small increase in cancer risk.