HPC2/ELAC2 polymorphisms and prostate cancer risk: analysis by age of onset of disease

Carriage of Ser217Leu and Ala541Thr Variants of ELAC2 Gene and Risk Factors in Patients with Prostate Cancer in Burkina Faso

Background

Genetic factors are one of the significant contributors to prostate cancer (PCa) development, and hereditary prostate cancer 2 (HPC2) locus gene ELAC2 is considered a PCa susceptibility region. The HPC2/ELAC2 gene has been identified by linkage analysis in familial prostate cancer patients in the United States but has never been studied in Burkina Faso. The objective of the present study was to analyze the carriage of the C650T (Ser217Leu) and G1621A (Ala541Thr) mutations of the ELAC2 gene and the risk factors in prostate cancer patients in Burkina Faso.

Methods

This case-control study included 76 participants, including 38 histologically confirmed prostate cancer cases and 38 healthy controls without prostate abnormalities. PCR combined with restriction fragment length polymorphism (RFLP) was used to characterize the genotypes of the Ser217Leu and Ala541Thr polymorphisms of the ELAC2 gene. The correlations between the different genotypes and risk factors for prostate cancer were investigated.

Results

The C650T mutation was present in 44.73% of prostate cancer cases and 47.37% of controls. The G1621A mutation was present in 26.32% of prostate cancer cases and 15.79% of controls. We did not detect an association between prostate cancer risk and the Ser217Leu (p=0.972) and Ala541Thr (p=0.267) variants of the ELAC2 gene. Also, the two ELAC2 SNPs did not correlate with clinical stage, prostate-specific antigen (PSA) level at diagnosis, or the Gleason score on biopsies. However, we found that 100% of homozygous carriers of the T650 mutation have an A1621 mutation (p ≤ 0.001).

Conclusion

Ser217Leu and Ala541Thr polymorphisms of ELAC2, considered alone or in combination, are not associated with prostate cancer risk.

A Study of Ser217Leu and Ala541Thr Polymorphism in the Men Afflicted with Prostate Cancer and in the Men being Suspicious of Prostate Cancer

Background and objective:

Prostate cancer is one of the most widespread cancers among men throughout the world. In addition, it is the second cause of death after lung cancer. Occurrence of the prostate cancer is variable in various regions of the world. Solely, there are three known risk factors for the prostate cancer, including: Age, inheritance and ethnic origin. ELAC2 protein is a phosphodiesterase enzyme encoded by ELAC2 gene in human. This gene is placed on chromosome 17, and it is believed that product of the mentioned gene is an endonuclease contributed in puberty of mitochondrion’s tRNA. From clinical viewpoint, variables of ELAC2 gene such as Ser217Leu and Ala541Thr Missense mutations which are accompanied by hereditary prostate cancer (HPC2).Objective of this study is to investigate Ser217Leu (rs4792311) and Ala541Thr (rs5030739) polymorphisms in the individuals with prostate cancer or those who are suspicious of prostate cancer with family past record/history.

Study method:

In this study conducted by case-control method in 2018, 102 men with prostate cancer and 98 men being suspicious of prostate cancer out of 10 families referred to shahid Rajaei Hospital in Tonekabon county to study and check were investigated. After collection of data using questionnaire, sampling from individuals and performance of the rest steps, study of polymorphism was carried out by PCR sequencing technique, and the results were analyzed by Chromas software.

Finding:

Of the total studied 102 individuals, 44 individuals (43.1%) were homozygote for Ser217Leu mutation, 36 individuals (35.2%) were heterozygote and 22 individuals (21.5%) lacked Missense mutation. for Ala541Thr mutation, 18 ones (17.6%) were heterozygote and 84 ones (82.3%) lacked Missense mutation. For Ser217Leu mutation, out of 98 suspicious individuals, 21 individuals (21.4%) were homozygote. 6 individuals (6.1%) were heterozygote and 71 individuals (72.4%) lacked the mutation. For Ala541Thr mutation, 15 ones (15.3%) were homozygote and 84 ones (84.6%) lacked the studied mutation.

Conclusion:

Results of this research showed that, in the individuals with the prostate cancer, there is a relationship between Ser217Leu and Ala541Thr polymorphism of ELAC2 gene and/with prostate cancer, and the suspicious individuals gotten involved in the mutation must take action to prevent this cancer.

Molecular Updates in Prostate Cancer

A wide array of molecular markers and genomic signatures, reviewed in this article, may soon be used as adjuncts to currently established screening strategies, prognostic parameters, and early detection markers. Markers of genetic susceptibility to PCA, recurrent epigenetic and genetic alterations, including ETS gene fusions, PTEN alterations, and urine-based early detection marker PCA3, are discussed. Impact of recent genome-wide assessment on our understanding of key pathways of PCA development and progression and their potential clinical implications are highlighted.

Prostate Cancer Genetics: A Review

Over the past decades, research has focussed on identifying the genetic underpinnings of prostate cancer. It has been recognized that a number of forms of genetic changes coupled with epigenetic and gene expression changes can increase the prediction to develop prostate cancer. This review outlines the role of somatic copy number alterations (SCNAs), structural rearrangements, point mutations, and single nucleotide polymorphisms (SNPs) as well as miRNAs. Identifying relevant genetic changes offers the ability to develop novel biomarkers to allow early and accurate detection of prostate cancer as well as provide risk stratification of patients following their diagnosis. The concept of personalized or individualized medicine has gained significant attention. Therefore, a better understanding of the genetic and metabolic pathways underlying prostate cancer development offers the opportunity to explore new therapeutic interventions with the possibility of offering patient-specific targeted therapy.

The genetic epidemiology of prostate cancer and its clinical implications

Worldwide, familial and epidemiological studies have generated considerable evidence of an inherited component to prostate cancer. Indeed, rare highly penetrant genetic mutations have been implicated. Genome-wide association studies (GWAS) have also identified 76 susceptibility loci associated with prostate cancer risk, which occur commonly but are of low penetrance. However, these mutations interact multiplicatively, which can result in substantially increased risk. Currently, approximately 30% of the familial risk is due to such variants. Evaluating the functional aspects of these variants would contribute to our understanding of prostate cancer aetiology and would enable population risk stratification for screening. Furthermore, understanding the genetic risks of prostate cancer might inform predictions of treatment responses and toxicities, with the goal of personalized therapy. However, risk modelling and clinical translational research are needed before we can translate risk profiles generated from these variants into use in the clinical setting for targeted screening and treatment.

Molecular pathways in prostate cancer

Objectives

Prostate cancer is a prevalent disease with a high impact on patients’ morbidity and mortality. Despite efforts to profile prostate cancer, the genetic alterations and biological processes that correlate with disease progression remain partially elusive. The purpose of this study is to review the recent evidence relating to the initiation and progression of prostate cancer in relation to the familial correlation of the disease, the genetic aberrations resulting in prostate cancer and the new molecular biology data regarding prostate cancer.

Materials and Methods

A Medline database search identified all the existing publications on the molecular events associated with the pathogenesis and evolution of prostate cancer. Particular emphasis was given on the specific genetic phenomena associated with prostate cancer.

Results

Like other cancers, prostate cancer is caused by an accumulation of genetic alterations in a cell that drives it to malignant growth. Specific genes and gene alterations have been suggested to play a role in its development and progression. Aneuploidy, loss of heterozygosity, gene mutations, hypermethylation and inactivation of specific tumour suppressor genes such as GSTpi, APC, MDR1, GPX3 and others have been detected in prostate cancers, but generally only at a low or moderate frequency. The androgen receptor (AR) signalling pathway may play a crucial role in the early development of prostate cancer, as well as in the development of androgen-independent disease that fails to respond to hormone deprivation therapies. Other alterations linked to the transition to hormone-independence include amplification of MYC and increased expression of ERBB2 and BCL2. Inflammatory changes may also contribute to the development of prostate cancer.

Conclusion

The identification of specific molecular markers for prostate cancer may lead to its earliest detection and better prediction of its behavior. The better understanding of the molecular events affecting prostate cancer progression may result in the introduction of new drugs to target these events thus providing a potential cure and a tool for prevention of this very common disease.

Polymorphisms of HPC2/ELAC2 and SRD5A2 (5α-Reductase Type II) Genes in Prostate Cancer

Prostate cancer is the proliferation of malignant cells in the prostate gland. The HPC2/ELAC2 gene on chromosome 17p11.2 and SRD5A2 gene on chromosome 2p22–23 are predisposing genetic factors. We examined the relationship between Ser217Leu and Ala541Thr polymorphisms of the former gene, and Ala49Thr and Val89Leu polymorphisms of the latter gene to prostate cancer in Turkish men, using the polymerase chain reaction (PCR) method and appropriate restriction enzymes. The HPC2/ELAC2 gene Ser217-Leu and SRD5A2 gene Ala49Thr polymorphisms were associated with an increased risk of prostate cancer in Turkish men [for the HPC2/ELAC2 gene Ser217Leu polymorphism: odds ratio (OR) 2.7; confidence interval 95% (CI 95%) 1.6–4.8; p 0.000<0.05, and for the SRD5A2 gene Ala49Thr polymorphism: OR 2.4; CI 95% 1.2–4.9; p 0.004<0.05].

ELAC2 polymorphisms and prostate cancer risk: a meta-analysis based on 18 case-control studies

Polymorphisms in the elaC homolog-2 (ELAC2)/HPC2 gene have been hypothesized to alter the risk of prostate cancer. However, the results of the related published studies remained conflicting. We performed a meta-analysis of 18 studies evaluating the association between ELAC2 Ser217Leu and Ala541Thr polymorphisms and prostate cancer risk. Overall, ELAC2 Leu217 allele was associated with increased prostate cancer risk as compared with the Ser217 allele (odds ratio (OR)=1.13, 95% confidence interval (CI): 1.03–1.24, P=0.019 for heterogeneity), as well as in the heterozygote comparison (OR=1.21, 95% CI: 1.07–1.36, P=0.034 for heterogeneity) and the dominant genetic model (OR=1.20, 95% CI: 1.07–1.35, P=0.025 for heterogeneity). Furthermore, the ELAC2 Thr541 allele was associated with increased prostate cancer risk as compared with the Ala541 allele (OR=1.22, 95% CI: 1.00–0.48, P=0.131 for heterogeneity). In the stratified analyses for Ser217Leu polymorphism, there was significantly increased prostate cancer risk in Asian and Caucasian populations, and studies using sporadic and familial prostate cancer cases. Similar result was found in the Asian population in the stratified analyses for Ala541Thr polymorphism. This meta-analysis showed evidence that ELAC2 Ser217Leu and Ala541Thr polymorphisms were associated with prostate cancer risk, and might be low-penetrance susceptibility markers of prostate cancer.

Polymorphisms in the HPC/ELAC-2 and alpha 1-antitrypsin genes that correlate with human diseases in a North Indian population

Two genes HPC/ELAC-2 and AAT were studied in north Indian population. HPC/ELAC-2 was studied in prostate cancer cases and AAT was studied in COPD patients. HPC/ELAC-2 is considered as an important cancer-susceptibility gene in prostate cancer. There are two common polymorphisms of this gene, i.e., Ser217Leu and Ala541Thr. Alpha 1 antitrypsin is a highly polymorphic anti-elastase enzyme, especially active in the protection of alveoli and liver. In the present study, we observed the distribution of two deficient alleles PiZ and Pi S in COPD patients. We extracted the DNA from 157 prostate cancer cases, 200 COPD patients, 170 BPH and 370 healthy controls. The polymorphisms were studied by PCR-RFLP technique. The mutant genotype (Leu/Leu) of HPC/ELAC-2 was present in 9.6, 7.6 and 5.9% of BPH, cancer cases and healthy controls, respectively. Higher risk of Ser/Leu as well as Leu/Leu had shown when compared to healthy controls. That was about 1.5 and 1.7-fold (OR = 1.55; 95% CI = 0.96-2.51; OR = 1.70; 95% CI = 0.74-3.92), respectively. Risk was found to be increased in smokers and those consuming non-vegetarian diet. Our results suggest that the HPC/ELAC-2 polymorphisms, especially in localized cases, could help to predict prostate cancer risk and confirm its high prevalence of the leu/leu allele in north Indian population. Considering heterozygous PiZ genotype, we obtained an OR of 3.82 (P = 0.03). Multivariate analysis adjusted by age sex and drinking habit showed 4.15-fold increased risk for COPD in PiZ heterozygous individuals. No increased risk was observed in the individuals carrying PiS alleles.

Association of HPC2/ELAC2 and RNASEL non-synonymous variants with prostate cancer risk in African American familial and sporadic cases

INTRODUCTION

The RNASEL and HPC2/ELAC2 genes have been implicated in hereditary prostate cancer. Further assessment of the role of these genes in sporadic prostate cancer in African American men (AAM) is warranted.

METHODS

Genotyping of HPC2/ELAC2 variants (S217L, A541T), along with RNASEL variants (R462Q and E541D) was completed in 155 African American sporadic and 88 familial prostate cancer cases, and 296 healthy male controls. Logistic regression analysis was performed and odds ratios (OR) were calculated, while correcting for both age and population stratification using admixture informative markers.

RESULTS

The HPC2/ELAC2 217L allele was significantly associated with risk of prostate cancer when taking all cases into account (OR = 1.6; 1.0-2.6; P = 0.03). The RNASEL 541D allele was associated with a decrease in risk of prostate cancer in sporadic cases (OR = 0.4; 0.2-0.8; P = 0.01). We did not detect an association between prostate cancer risk and the RNASEL R462Q variant. Results from haplotype analyses of the two RNASEL variants revealed highly significant differences in haplotype allele frequencies between cases and controls suggesting a synergistic effect at the RNASEL locus. One haplotype in particular (462R-541D) is far more frequent in our control population and shows a strong protective effect against prostate cancer (OR = 0.47, P = 8.1 x 10(-9)).

CONCLUSIONS

These results suggest that HPC2/ELAC2 and RNASEL may play a role, however minor, in prostate cancer risk among AAM.

Sequence variants of elaC homolog 2 (Escherichia coli) (ELAC2) gene and susceptibility to prostate cancer in the Health Professionals Follow-Up Study

Two non-synonymous single-nucleotide polymorphisms (SNPs), Ser217Leu and Ala541Thr, in the elaC homolog 2 (Escherichia coli) (ELAC2) gene have been related to prostate cancer risk in previous studies, though with inconsistent results. The association of ELAC2 haplotypes with prostate cancer risk has not yet been explored. We assessed whether sequence variants in ELAC2 were associated with the risk of total or aggressive prostate cancer. In a nested case-control design within the Health Professionals Follow-Up Study, we identified 659 participants with prostate cancer diagnosed after they provided a blood specimen in 1993 and before January 2000. Controls were 656 age-matched men without prostate cancer who had had a prostate-specific antigen test after providing a blood specimen. We genotyped eight tagging SNPs in ELAC2 to test for the association between sequence variances in ELAC2 and prostate cancer. No individual SNP (including Ser217Leu) was associated with the risk of prostate cancer. Ala541Thr is a rare SNP in this population. One common haplotype (hap4) was statistically significantly associated with an increased risk of prostate cancer [odds ratio (OR) = 1.39, 95% confidence interval = 1.05-1.85]. Two common promoter SNPs and three common haplotypes were statistically significantly associated with aggressive prostate cancer (carriers versus non-carriers-snp2: OR = 1.43, snp3: OR = 0.69, hap1: OR = 1.47, hap2: OR = 0.72, hap4: OR = 1.51; global P-value for all common haplotypes = 0.11). Common SNPs and haplotypes of ELAC2 were associated with risk of aggressive prostate cancer.

Genetic susceptibility to prostate cancer in men of African descent: implications for global disparities in incidence and outcomes

INTRODUCTION

Disparities in prostate cancer incidence and outcomes are a hallmark of the global pattern of prostate cancer, with men of African descent suffering disproportionately from this disease. The causes of these disparities are poorly understood.

METHODS

A review of the literature was undertaken to evaluate the role that genetic susceptibility may play in prostate cancer etiology and outcomes, with a particular emphasis on disparities.

RESULTS

The genetic contribution to prostate cancer is well established, and a number of candidate prostate cancer genes have been identified. Significant differences in the frequency of risk alleles in these genes have been identified across the major races. These allele frequency differences may in part explain an increased susceptibility to prostate cancer in some populations. In addition, non-genetic factors contribute significantly to prostate cancer disparities, and the cumulative contribution of both genetic and non-genetic factors to poor-prognosis prostate cancer may explain the poorer outcomes experienced by men of African descent.

CONCLUSIONS

Prostate cancer disparities are a function of genetic susceptibility as well as environment, behavior, and health care factors acting in the context of this genetic susceptibility. Elimination of global prostate cancer disparities requires a full understanding of the effects of all of these factors on prostate cancer etiology and outcomes.

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.

The eukaryotic Pso2p/Snm1p family revisited: in silico analyses of Pso2p A, B and Plasmodium groups

The eukaryotic family of Pso2/Snm1 exo/endonuclease proteins has important functions in repair of DNA damages induced by chemical interstrand cross-linking agents and ionizing radiation. These exo/endonucleases are also necessary for V(D)J recombination and genomic caretaking. However, despite the growing biochemical data about this family, little is known about the number of orthologous/paralogous Pso2p/Snm1p sequences in eukaryotes and how they are phylogenetically organized. In this work we have characterized new Pso2p/Snm1p sequences from the finished and unfinished eukaryotic genomes and performed an in-depth phylogenetic analysis. The results indicate that four phylogenetically related groups compose the Pso2p/Snm1p family: (i) the Artemis/Artemis-like group, (ii) the Pso2p A group, (iii) the Pso2p B group and (iv) the Pso2p Plasmodium group. Using the available biochemical and genomic information about Pso2p/Snm1p family, we concentrate our research in the study of Pso2p A, B and Plasmodium groups. The phylogenetic results showed that A and B groups can be organized in specific subgroups with different functions in DNA metabolism. Moreover, we subjected selected Pso2p A, B and Plasmodium proteins to hydrophobic cluster analysis (HCA) in order to map and to compare conserved regions within these sequences. Four conserved regions could be detected by HCA, which are distributed along the metallo-beta-lactamase and beta-CASP motifs. Interestingly, both Pso2p A and B proteins are structurally similar, while Pso2p Plasmodium proteins have a unique domain organization. The possible functions of A, B and Plasmodium groups are discussed.

Polymorphisms in the prostate-specific antigen gene promoter do not predict serum prostate-specific antigen levels in African-American men

A major problem with the use of serum prostate-specific antigen (PSA) in predicting prostate cancer risk is the considerable variability of such measurements. Cramer et al. identified a set of single-nucleotide polymorphisms (SNPs) in the upstream regulatory region of the PSA gene that were each associated with increased promoter activity and serum PSA, further suggesting that genotyping these SNPs could be useful in improving the predictive value of PSA screening. In order to replicate this finding, DNA samples from 475 African-American men were genotyped for the same SNPs and no association was observed with either serum PSA level or prostate cancer diagnosis.

Association of susceptibility alleles in ELAC2/HPC2, RNASEL/HPC1, and MSR1 with prostate cancer severity in European American and African American men

Reported associations of ELAC2/HPC2, RNASEL/HPC1, and MSR1 with prostate cancer have been inconsistent and understudied in African Americans. We evaluated the role of 16 sequence variants in these genes with prostate cancer using 888 European American and 131 African American cases, and 473 European American and 163 African American, controls. We observed significant differences in ELAC2, RNASEL, and MSR1 allele frequencies by race. However, we did not observe significant associations between prostate cancer and any variants examined for both races combined. Associations were observed when stratified by race, family history, or disease severity. European American men homozygous for MSR1 IVS7delTTA had an elevated risk for localized stage [odds ratio, (OR), 3.5; 95% confidence interval (95% CI), 1.4-6.9], low-grade (OR, 3.2; 95% CI, 1.4-7.3) disease overall, and with low-grade (OR, 2.9; 95% CI, 1.2-7.2) or late-stage disease (OR, 5.2; 95% CI, 1.1-25.7) in family history-negative African Americans. MSR1 Arg293X was associated with family history-negative high-grade disease (OR, 4.0; 95% CI, 1.1-14.1) in European Americans. RNASEL Arg462Gln was associated with low-grade (OR, 1.5; 95% CI, 1.04-2.2) and early-stage (OR, 1.5; 95% CI, 1.02-2.1) disease in family history-negative European Americans. In family history-positive individuals, Arg462Gln was inversely associated with low-grade (OR, 0.43; 95% CI, 0.21-0.88) and low-stage (OR, 0.46; 95% CI, 0.22-0.95) disease. In African Americans, Arg462Gln was associated with positive family history high-stage disease (OR, 14.8; 95% CI, 1.6-135.7). Meta-analyses revealed significant associations of prostate cancer with MSR1 IVS7delTTA, -14,742 A>G, and Arg293X in European Americans; Asp174Tyr in African Americans; RNASEL Arg462Gln in European American's overall and in family history-negative disease; and Glu265X in family history-positive European Americans. Therefore, MSR1 and RNASEL may play a role in prostate cancer progression and severity.

The missense mutations in the candidate prostate cancer gene ELAC2 do not alter enzymatic properties of its product

The candidate prostate cancer gene ELAC2 encodes tRNA 3' processing endoribonuclease (tRNase ZL). We produced recombinant human tRNase ZL's, which contain one to three amino-acid substitutions from three missense mutations (Ser217Leu, Ala541Thr, and Arg781His) that are associated with the occurrence of prostate cancer. These enzymes were examined for the pre-tRNA cleavage and the RNase 65 activity. We did not observe any differences in enzymatic properties such as Km and k(cat) values between the wild-type tRNase ZL and its variants. We conclude that there is no causality between the enzymatic properties of tRNase ZL and the prostate cancer.

Characterization of linkage disequilibrium structure, mutation history, and tagging SNPs, and their use in association analyses:ELAC2 and familial early-onset prostate cancer

In association analyses, it is critical that informative single-nucleotide polymorphisms (SNPs) be selected for study and utilized appropriately. We sequenced 38 kb, including exons of ELAC2, promoter region and conserved upstream intergenic sequences. A comprehensive characterization of linkage disequilibrium (LD) structure and mutation history was performed using our principal components analysis (PCA) method and a phylogenetic analysis. We identified a complex pattern of LD structure consistent with the occurrence of both recombination and mutation events within ELAC2. Four overlapping and noncontiguous LD groups were defined. Eight tagging SNPs (tSNPs) were identified, accounting for over 90% of the genetic variation of the 19 total variants. We tested associations between familial early-onset prostate cancer (PRCA) and each variant independently and in haplotypes. We performed these tests using all 19 variants and the 8 tSNPs; the results using tSNP haplotypes accurately represent the association evidence for the full haplotypes. We observed increased evidence for association when SNPs were analyzed in haplotypes. The phylogenetic analysis indicated three haplotypes, clustered farthest from the root-node, all of which were found more often in cases than controls. These three haplotypes together showed the best evidence of association with familial, early-onset PRCA (P=0.0024; odds ratio=2.23; 95% CI, 1.33-3.74), indicating possible allelic heterogeneity. Our results suggest that 8 tSNPs are required to comprehensively assess associations in ELAC2, and that haplotypes should be considered for analysis, and that a knowledge of mutation history may be helpful in parsing allelic heterogeneity and suggesting combinations of haplotypes to be tested.

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.

Structure of primate and rodent orthologs of the prostate cancer susceptibility gene ELAC2

The human ELAC2 gene was the first candidate prostate cancer susceptibility gene identified by linkage analysis and positional cloning. DNA sequence indicates a protein of 826 amino acids encoded by 24 exons. In the present study, we characterized the coding sequence of chimpanzee and gorilla ELAC2 orthologs by direct sequencing of genomic fragments, and of cynomolgus monkey and rat orthologs by screening cDNA libraries. The orthologs characterized in the chimpanzee, gorilla and cynomolgus monkey also encode proteins of 826 amino acids, sharing 98.9%, 98.5% and 93.7% sequence identity with the human protein. Our analyses of the mouse ELAC2 gene identified two alternative mRNA transcripts. One is translated into a protein of 824 a.a. (mouse ELAC2), whereas the other one encodes a protein of 831 amino acids (mouse ELAC2A) resulting from an alternatively spliced form of 25 exons. The rat ELAC2 gene ortholog also expressed two similar alternatively spliced transcripts. These two forms are ubiquitously expressed in mouse and rat tissues. The highest levels of expression of the ELAC2 form are observed in the testis while the lowest levels are seen in the prostate and in the muscle. However, it is of interest to note that the relative abundance of the rat and mouse ELAC2 transcripts, measured by real-time quantitative PCR, is higher than the respective ELAC2A forms in all surveyed tissues except for the prostate and the muscle. The ELAC2A transcript levels are 4.1 to 5.0-fold higher than the ELAC2 levels in the prostate of rat and mouse, respectively. A fine analysis of the conserved domains on the primary structure of ELAC2 orthologs revealed the presence of a putative beta-CASP domain shared by the PSO2 (SNM1) DNA interstrand cross-link repair proteins, and the 73-kDa subunit of mRNA 3' end cleavage and polyadenylation specificity factor (CPSF73) as well as Artemis proteins, thus suggesting a potential interaction of ELAC2 gene product with nucleic acids and more specifically with RNA targets. Taken together, these data offer useful tools to further study the regulation and cellular function of ELAC2 gene in experimental models and provide further insight concerning conserved amino acid motifs that could have biological significance.

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.

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.

HPC2/ELAC2 gene variants associated with incident prostate cancer

The HPC2/ELAC2 gene on chromosome 17p11 was identified as a candidate gene for hereditary prostate cancer (HPC) susceptibility. Two HPC2 gene missense variants, Ser217Leu (Leu217) and Ala541Thr (Thr541) have been associated with incident prostate cancer cases in some studies, but not in others. We tested for possible associations between the two HPC2 gene variants and prostate cancer risk in incident prostate cancer cases (199) and healthy male controls (525) from the Calgary region. The Thr541 variant showed linkage disequilibrium with the Leu217 variant. The number of Leu217 homozygotes in the case and control groups (8.6 versus 8.5%) was not statistically different. Leu217 carrier status was associated with prostate cancer risk (cases 61.8% versus controls 50.3%) (OR 1.6, 95% CI 1.15-2.23). Additional analysis found that this association was not due to the co-existence of Thr541 variant (OR1.59, P=0.009). Logistic regression found that the relationship between the log odds of being a Thr541carrier and age depends on case/control status. Thr541 carriers had an increased risk for late-onset prostate cancer (P=0.028). Prostate intraepithelial neoplasia (PIN) was more common in the Leu217 allele carriers compared to non-carriers (42.3 versus 26.7%) (OR 2.05, 95% CI 1.10-3.83), and in the Thr541 carriers compared to non-carriers (50.0 versus 34.6%) (OR 1.89, 95% CI 0.75-4.78). In summary, the HPC2 gene variants Leu217 and Thr541 were associated with an increased risk for prostate cancer and for PIN in males undergoing radical prostatectomies in the Calgary region.

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.

A candidate prostate cancer susceptibility gene encodes tRNA 3' processing endoribonuclease

tRNA 3' processing endoribonuclease (3' tRNase) is an enzyme responsible for the removal of a 3' trailer from precursor tRNA (pre-tRNA). We purified approximately 85 kDa 3' tRNase from pig liver and determined its partial sequences. BLAST search of them suggested that the enzyme was the product of a candidate human prostate cancer susceptibility gene, ELAC2, the biological function of which was totally unknown. We cloned a human ELAC2 cDNA and expressed the ELAC2 protein in Escherichia coli. The recombinant ELAC2 was able to cleave human pre-tRNA(Arg) efficiently. The 3' tRNase activity of the yeast ortholog YKR079C was also observed. The C-terminal half of human ELAC2 was able to remove a 3' trailer from pre-tRNA(Arg), while the N-terminal half failed to do so. In the human genome exists a gene, ELAC1, which seems to correspond to the C-terminal half of 3' tRNase from ELAC2. We showed that human ELAC1 also has 3'-tRNase activity. Furthermore, we examined eight ELAC2 variants that seem to be associated with the occurrence of prostate cancer for 3'-tRNase activity. Seven ELAC2 variants which contain one to three amino acid substitutions showed efficient 3'-tRNase activities, while one truncated variant, which lacked a C-terminal half region, had no activity.