Germline mutations in the ribonuclease L gene in families showing linkage with HPC1

Pooled genome linkage scan of aggressive prostate cancer: results from the International Consortium for Prostate Cancer Genetics

While it is widely appreciated that prostate cancers vary substantially in their propensity to progress to a life-threatening stage, the molecular events responsible for this progression have not been identified. Understanding these molecular mechanisms could provide important prognostic information relevant to more effective clinical management of this heterogeneous cancer. Hence, through genetic linkage analyses, we examined the hypothesis that the tendency to develop aggressive prostate cancer may have an important genetic component. Starting with 1,233 familial prostate cancer families with genome scan data available from the International Consortium for Prostate Cancer Genetics, we selected those that had at least three members with the phenotype of clinically aggressive prostate cancer, as defined by either high tumor grade and/or stage, resulting in 166 pedigrees (13%). Genome-wide linkage data were then pooled to perform a combined linkage analysis for these families. Linkage signals reaching a suggestive level of significance were found on chromosomes 6p22.3 (LOD = 3.0), 11q14.1-14.3 (LOD = 2.4), and 20p11.21-q11.21 (LOD = 2.5). For chromosome 11, stronger evidence of linkage (LOD = 3.3) was observed among pedigrees with an average at diagnosis of 65 years or younger. Other chromosomes that showed evidence for heterogeneity in linkage across strata were chromosome 7, with the strongest linkage signal among pedigrees without male-to-male disease transmission (7q21.11, LOD = 4.1), and chromosome 21, with the strongest linkage signal among pedigrees that had African American ancestry (21q22.13-22.3; LOD = 3.2). Our findings suggest several regions that may contain genes which, when mutated, predispose men to develop a more aggressive prostate cancer phenotype. This provides a basis for attempts to identify these genes, with potential clinical utility for men with aggressive prostate cancer and their relatives.

An Alternative SplicedRNASELVariant in Peripheral Blood Leukocytes

2-5A-Dependent RNase L is an endoribonuclease that catalyzes RNA degradation and promotes apoptosis during the innate antiviral response in mammalian cells. Prior studies showed that RNASEL is widely expressed and suggested the presence of mRNA species of different sizes but lacked a characterization of these variants. Using RT-PCR, we show that RNASEL is expressed in all human tissues examined, whereas an alternatively generated spliced variant lacking the third exon (RNASEL del_Ex3) is solely expressed in peripheral blood leukocytes (PBL). Quantitative RT-PCR measurements of RNA from different PBL cell types separated by fluorescence activated cell sorting (FACS) showed that complete RNASEL mRNA levels were significantly elevated in granulocytes compared with all other PBL cell types, whereas expression was lowest in CD8(+) T cells. The alternatively spliced RNASEL del_Ex3 transcript was present in all PBL cell types examined but at lower levels than the full-length RNASEL mRNA. The presence of high levels of RNase L protein in granulocytes was confirmed by immunohistochemistry. Our findings are the first to demonstrate the presence of an alternatively spliced RNASEL mRNA and to demonstrate the variable expression of RNase L in different leukocytes. Our results suggest that RNase L plays an important role in granulocytes as an innate immunity enzyme that controls viral infections.

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.

Tumour suppressor function of RNase L in a mouse model

RNase L is one of the key enzymes involved in the molecular mechanisms of interferon (IFN) actions. Upon binding with its activator, 5'-phosphorylated, 2'-5' oligoadenylates (2-5A), RNase L plays an important role in the antiviral and anti-proliferative functions of IFN, and exerts proapoptotic activity independent of IFN. In this study, we have found that RNase L retards proliferation in an IFN-dependent and independent fashion. To directly measure the effect of RNase L on tumour growth in the absence of other IFN-induced proteins, human RNase L cDNA was stably expressed in P-57 cells, an aggressive mouse fibrosarcoma cell line. Three clonal cell lines were isolated in which the overexpression of RNase L was 15-20-fold of the endogenous level. Groups of five nude mice were injected subcutaneously with either the human RNase L overexpressing clones (P-RL) or control cells transfected with an empty vector (P-Vec). Tumour growth by the two cell lines was monitored by measuring tumour volumes. In the P-RL group, tumour formation was significantly delayed and the tumours grew much slower compared to the control group. Morphologically, the P-RL tumour appeared to have more polygonal cells and increased single cell tumour necrosis. Interestingly, P-RL tumours eventually started to grow. Further analysis revealed, however, that these tumours no longer expressed ectopic RNase L. Our findings suggest that RNase L plays a critical role in the inhibition of fibrosarcoma growth in nude mice.

Messenger RNAs under differential translational control in Ki-ras-transformed cells

Microarrays have been used extensively to identify differential gene expression at the level of transcriptional control in oncogenesis. However, increasing evidence indicates that changes in translational control are critical to oncogenic transformation. This study identifies mRNA transcripts that are differentially regulated, primarily at the level of translation, in the immortalized human embryonic prostate epithelial cell line 267B1 and the v-Ki-ras-transformed counterpart by comparing total mRNA to polysome-bound mRNA by using Affymetrix oligonucleotide microarrays. Among the transcripts that were identified were those encoding proteins involved in DNA replication, cell cycle control, cell-to-cell interactions, electron transport, G protein signaling, and translation. Many of these proteins are known to contribute to oncogenesis or have the potential to contribute to oncogenesis. Differential expression of RNA-binding proteins and the presence of highly conserved motifs in the 5' and 3' untranslated regions of the mRNAs are consistent with multiple pathways and mechanisms governing the changes in translational control. Although Alu sequences were found to be associated with increased translation in transformed cells, an evolutionarily conserved motif was identified in the 3' untranslated regions of ephrinB1, calreticulin, integrin alpha3, and mucin3B that was associated with decreased polysome association in 267B1/Ki-ras.

Identification of germline MLH1 alterations in familial prostate cancer

Several linkage and loss of heterozygosity (LOH) analyses suggest that the region 3p21-p26, which is a chromosomal location of MLH1, could harbour a susceptibility gene for prostate cancer (PRCA). Furthermore, in a recent candidate single nucleotide polymorphism (SNP) analysis the I219V variation of the MLH1 gene was associated with PRCA. Microsatellite instability (MSI) and germ-line MLH1 mutations were originally demonstrated in hereditary non-polyposis colorectal cancer (HNPCC) but MSI and loss of MLH1 function have also been detected in PRCA. To assess the contribution of MLH1 germline mutations to the development of PRCA in Finland different approaches were used. First, the samples from 11 PRCA-colon cancer patients were screened for MLH1, MSH2 and MSH6 protein expression by immunohistochemistry (IHC). IHC revealed one patient with a putative MLH1 aberration and sequencing of this sample revealed five sequence variants including two missense variants P434L and I219V. Second, the samples from Finnish hereditary prostate cancer (HPC) families were used for the screening of MLH1 mutations which produced twelve MLH1 sequence variants including two missense mutations, I219V, as in the PRCA-colon cancer patient, and V647M. P434L and V647 were both novel, rare variants. Carrier frequencies of the I219V mutation were compared between hereditary prostate cancer (HPC) patients, unselected PRCA cases, patients with benign prostate hyperplasia and controls, but no differences between the sample groups were found. P434L was not present in this study population and V647M was a very rare variant found only in one HPC family. According to the present results, MLH1 does not have a major role in PRCA causation in Finland.

Molecular markers in the diagnosis of prostate cancer

The genetic alterations leading to prostate cancer are gradually being discovered. A wide variety of genes have been associated with prostate cancer development as well as tumor progression. Knowledge of gene polymorphisms associated with disease aid in the understanding of important pathways involved in this process and may result in the near future in clinical applications. Urinary molecular markers will soon be available to aid in the decision of repeat prostate biopsies. Recent findings suggest the importance of androgen signaling in disease development and progression. The further understanding of interaction of inflammation, diet, and genetic predisposition will improve risk stratification in the near future.

The 471delAAAG mutation and C353T polymorphism in the RNASEL gene in sporadic and inherited cancer in Israel

The rate of RNASEL 471delAAAG mutation was previously reported to be less than 7% in Ashkenazi prostate cancer patients. It seems plausible that the same mutation may also be involved in breast/ovarian cancer predisposition in Jewish individuals. To evaluate the role of this mutation in cancer predisposition, a total of 1011 individuals including 294 Jewish men with prostate cancer, 61 Ashkenazi women with ovarian cancer and 50 unaffected women, matched for age and ethnicity, were genotyped for sequence anomalies in a single RNASEL gene amplicon using DGGE and sequencing. Additionally, 209 Ashkenazi BRCA1/2 mutation carriers, 205 high-risk non-carriers matched for cancer type and age at diagnosis, and 192 healthy Ashkenazi women were screened, using DHPLC and restriction methods. The 471delAAAG mutation was detected in a single male with prostate cancer (1/294, 0.3%), in two ovarian cancer patients (2/141, 1.4%) and in one of 242 healthy controls (0.41%). An abnormal DHPLC profile identical to the one produced by the 471delAAAG mutation was noted in 23 additional women. The rate of this polymorphism was significantly elevated in high-risk non-carrier women (16/205; 7.8%) than in BRCA1/2 carriers (2/209; 1.0%) and controls (5/192; 2.6%) (chi = 11.670; P < 0.001). Sequence analysis disclosed a silent polymorphism in Valine at codon 118: c.353 C- > T.The 471delAAAG mutation occurs rarely in Israeli prostate and breast/ovarian cancer patients. A silent polymorphism in the RNASEL gene occurs more prevalently in high-risk Ashkenazi breast/ovarian cancer patients without a BRCA1/2 mutation.

Role of mitochondria in apoptosis induced by the 2-5A system and mechanisms involved

The 2-5A system (2-5OAS/RNaseL) is composed of the 2',5'oligoadenylate synthetase 1 (2-5OAS1) and 2-5A-dependent RNase (RNaseL), enzymes that play a key role in antiviral defence mechanisms. Activation of the 2-5A system by double stranded RNA (dsRNA) induces degradation of ribosomal RNAs and apoptosis in mammalian cells. To obtain further information into the molecular mechanisms by which RNaseL induces apoptosis, we expressed human RNaseL and 2-5OAS in HeLa cells using recombinant vaccinia viruses as vectors and we analysed in detail different biochemical markers of apoptosis. In this expression virus-cell system the activation of RNaseL, as index of rRNA degradation, is an upstream event of apoptosis induction. RNaseL induces apoptosis in a caspase-dependent manner (caspases 8, 9 and 2). At the beginning of apoptosis RNaseL and 2-5OAS are localized in the mitochondria and cytosol fractions, while at the onset of apoptosis both enzymes are largely in mitochondria. The 2-5A system induces the release of Cytochrome c from mitochondria to cytosol in a caspase dependent manner. The onset of apoptosis elicits the disruption of mitochondrial membrane potential (delta psi m), as well as the generation of reactive oxygen species (ROS). Moreover, the activation of RNaseL induces morphological alterations in the mitochondria. Apoptosis induced by the 2-5A system involves mitochondrial proteins, such as the human anti-apoptotic protein Bcl-2, which blocks both the apoptosis and the change of delta psi m induced by the activation of RNaseL. These findings provide new insights into the molecular mechanisms of apoptosis induction by the 2-5A system, demonstrating the importance of mitochondria in 2-5OAS/RNaseL-induced apoptosis.

Overcoming Resistance to Interferon-Induced Apoptosis of Renal Carcinoma and Melanoma Cells by DNA Demethylation

Epigenetic editing of gene expression by aberrant methylation of DNA may help tumor cells escape attack from the innate and acquired immune systems. Resistance to antiproliferative effects and apoptosis induction by interferons (IFNs) was postulated to result from silencing of IFN response genes by promoter hypermethylation. Treatment of human ACHN renal cell carcinoma (RCC) and A375 melanoma cells with the DNA demethylating nucleoside analog 5-AZA-2′-deoxycytidine (5-AZA-dC) synergistically augmented antiproliferative effects of IFN- alpha (α) 2 and IFN-beta (β). Either 5-AZA-dC or an antisense to DNA methyltransferase 1 (DNMT1) overcame resistance to apoptosis induction by IFNs with up to 85% apoptotic cells resulting from the combinations. No similar potentiation occurred in normal kidney epithelial cells. IFN response genes were augmented more than 10 times in expression by 5-AZA-dC. Demethylation by 5-AZA-dC of the promoter of the prototypic, apoptosis-associated IFN response gene XAF1 was confirmed by methylation-specific polymerase chain reaction. siRNA to XAF1 inhibited IFN-induced apoptosis; conversely, overexpression of XAF1 overcame resistance to apoptosis induction by IFN-β. As occurred with apoptosis-resistant melanoma cells in vitro, tumor growth inhibition in the nude mouse of human A375 melanoma xenografts resulted from treatment with 5-AZA-dC in combination with IFN-β, an effect not resulting from either single agent. The importance of epigenetic remodeling of expression of immune-modifying genes in tumor cells was further suggested by identifying reactivation of the cancer-testis antigens MAGE and RAGE in ACHN cells after DNMT1 depletion. Thus, inhibitors of DNMT1 may have clinical relevance for immune modulation by augmentation of cytokine effects and/or expression of tumor-associated antigens.

New Insights into Prostate Cancer Biology

Prostate cancer is common, biologically heterogeneous, and protean in its clinical manifestations. Through the use and analysis of isogenic cell lines, xeno-grafts, transgenic mice, and human tumors, one begins to deconvolute the precise biologic mechanisms that combine to create the native complexity and heterogeneity of this disease. In this article, the authors have underscored compelling recent discoveries in prostate cancer so as to provide the reader with molecular paradigms with which to interpret future insights into its biology. Although it was inevitably necessary to omit a significant amount of important research in prostate cancer, the work discussed here is exemplary of current prostate cancer research. Looking forward, it is hoped that the collective work of mapping genetic and biologic interactions among key regulators of prostate epithelial cells, epithelial-stromal interactions, host immune system, and host genetics will eventually result in a comprehensive understanding of prostate cancer. Although it is likely that the molecular characteristics of an individual's prostate cancer will be analyzed using limited molecular tools in the near future, eventual application of genomic technologies and nanotechnology offers the promise of robust future characterization. Such a characterization is likely to be required to maximize our ability to optimize and individualize preventive and treatment strategies.

Association of the polymorphisms of genes involved in androgen metabolism and signaling pathways with familial prostate cancer risk in a Japanese population

BACKGROUND

Androgen plays a central role in the normal and malignant development of prostate glands. Genetic polymorphisms of genes involved in androgen metabolism and signaling might be associated with the risk of prostate cancer.

METHODS

One hundred and two patients with prostate cancer with a family history and 117 healthy age- and residence-matched male controls were enrolled. Genotypes of the CAG repeat length of androgen receptor (AR), CYP17, 5alpha-reductase type II (SRD5A2), UDG-glucuronosyltransferase (UGT) 2B15, PSA promoter genes were analyzed.

RESULTS

For single polymorphisms, the presence of Y alleles showed a significantly lower risk of prostate cancer in comparison with the D/D genotype in UGT2B15 (odds ratio [OR]=0.41, 95% confidence interval [CI]=1.40-4.28, p=0.0015), and the presence of A2 alleles showed a weak tendency to decrease prostate cancer risk in comparison with the A1/A1 genotype in CYP17 (OR=0.69, 95% CI=0.39-1.23, p=0.21). The stratification of cases according to clinical stage and pathological grade showed that the A2/A2 genotype was significantly associated with localized stage cancer in comparison with metastatic stage cancer (OR=5.18, 95% CI=1.49-17.95, p=0.007). The combination of UGT2B15 and CYP17 genotypes could identify higher risk subjects even in subjects with low-risk UGT2B15 genotypes, i.e., Y/Y+D/Y genotypes (OR=1.97, 95% CI=0.92-4.22, p=0.079).

CONCLUSION

Genetic polymorphisms of the genes involved in androgen metabolism and signaling were significantly associated with familial prostate cancer risk. Single nucleotide polymorphisms of low-penetrance genes could be targets to understand genetic susceptibility to familial prostate cancer.

Interactions of sequence variants in interleukin-1 receptor-associated kinase4 and the toll-like receptor 6-1-10 gene cluster increase prostate cancer risk

Chronic or recurrent inflammation has been suggested as a causal factor in several human malignancies, including prostate cancer. Genetic predisposition is also a strong risk factor in the development of prostate cancer. In particular, Toll-like receptors (TLR), especially the TLR6-1-10 gene cluster, are involved in prostate cancer development. Interleukin-1 receptor-associated kinases (IRAK) 1 and 4 are critical components in the TLR signaling pathway. In this large case-control study, we tested two hypotheses: (a) sequence variants in IRAK1 and IRAK4 are associated with prostate cancer risk and (b) sequence variants in IRAK1/4 and TLR1-6-10 interacts and confers a stronger risk to prostate cancer. We analyzed 11 single nucleotide polymorphisms (four in IRAK1 and seven in IRAK4) among 1,383 newly diagnosed prostate cancer patients and 780 population controls in Sweden. Although the single-nucleotide polymorphisms in IRAK1 and IRAK4 alone were not significantly associated with prostate cancer risk, one single-nucleotide polymorphism in IRAK4, when combined with the high-risk genotype at TLR6-1-10, conferred a significant excess risk of prostate cancer. In particular, men with the risk genotype at TLR6-1-10 and IRAK4-7987 CG/CC had an odds ratio of 9.68 (P = 0.03) when compared with men who had wild-type genotypes. Our findings suggest synergistic effects between sequence variants in IRAK4 and the TLR 6-1-10 gene cluster. Although this study was based on a priori hypothesis and was designed to address many common issues facing this type of study, our results need confirmation in even larger studies.

A common nonsense mutation in EphB2 is associated with prostate cancer risk in African American men with a positive family history

BACKGROUND

The EphB2 gene was recently implicated as a prostate cancer (PC) tumour suppressor gene, with somatic inactivating mutations occurring in approximately 10% of sporadic tumours. We evaluated the contribution of EphB2 to inherited PC susceptibility in African Americans (AA) by screening the gene for germline polymorphisms.

METHODS

Direct sequencing of the coding region of EphB2 was performed on 72 probands from the African American Hereditary Prostate Cancer Study (AAHPC). A case-control association analysis was then carried out using the AAHPC probands and an additional 183 cases of sporadic PC compared with 329 healthy AA male controls. In addition, we performed an ancestry adjusted association study where we adjusted for individual ancestry among all subjects, in order to rule out a spurious association due to population stratification.

RESULTS

Ten coding sequence variants were identified, including the K1019X (3055A-->T) nonsense mutation which was present in 15.3% of the AAHPC probands but only 1.7% of 231 European American (EA) control samples. We observed that the 3055A-->T mutation significantly increased risk for prostate cancer over twofold (Fisher's two sided test, p = 0.003). The T allele was significantly more common among AAHPC probands (15.3%) than among healthy AA male controls (5.2%) (odds ratio 3.31; 95% confidence interval 1.5 to 7.4; p = 0.008). The ancestry adjusted analyses confirmed the association.

CONCLUSIONS

Our data show that the K1019X mutation in the EphB2 gene differs in frequency between AA and EA, is associated with increased risk for PC in AA men with a positive family history, and may be an important genetic risk factor for prostate cancer in AA.

Allelic imbalance of HER2 variant in sporadic breast and ovarian cancer

Both breast and ovarian cancers are associated with HER2 receptor activation, which usually results from receptor overexpression and/or gene amplification. The HER-2 gene harbors a polymorphism at codon 655 (GTC/valine to ATC/isoleucine) in the transmembrane domain region, which has been associated with an elevated risk of breast cancer. The objective of this study was to determine whether the polymorphism is under a selection pressure during breast and ovarian carcinogenesis. The Ile/Val genotype was present in 41% (9/22) of the normal DNA of breast cancer patients. An allelic imbalance in the tumor tissue was found in three breast tumors, with overrepresentation of the Val allele. HER-2 was amplified and overexpressed in these tumors. Half of the eight ovarian tumor patients carried heterozygous Ile/Val genotypes. In contrast to breast tumors, all these ovarian cancer specimens showed the presence of the Ile allele. In our selected set of tumors, the Val allele was overrepresented in the subset of HER2-positive breast cancers and the Ile allele in serous ovarian cancer. Further analyses of tumors with known gene amplifications and overexpression may reveal novel associations between germline polymorphisms and development of sporadic tumors.

Cross-regulation between Notch and p63 in keratinocyte commitment to differentiation

Notch signaling promotes commitment of keratinocytes to differentiation and suppresses tumorigenesis. p63, a p53 family member, has been implicated in establishment of the keratinocyte cell fate and/or maintenance of epithelial self-renewal. Here we show that p63 expression is suppressed by Notch1 activation in both mouse and human keratinocytes through a mechanism independent of cell cycle withdrawal and requiring down-modulation of selected interferon-responsive genes, including IRF7 and/or IRF3. In turn, elevated p63 expression counteracts the ability of Notch1 to restrict growth and promote differentiation. p63 functions as a selective modulator of Notch1-dependent transcription and function, with the Hes-1 gene as one of its direct negative targets. Thus, a complex cross-talk between Notch and p63 is involved in the balance between keratinocyte self-renewal and differentiation.

RNase L plays a role in the antiviral response to West Nile virus

Alleles at the Flv locus determine disease outcome after a flavivirus infection in mice. Although comparable numbers of congenic resistant and susceptible mouse embryo fibroblasts (MEFs) are infected by the flavivirus West Nile virus (WNV), resistant MEFs produce approximately 100- to 150-fold lower titers than susceptible ones and flavivirus titers in the brains of resistant and susceptible animals can differ by >10,000-fold. The Flv locus was previously identified as the 2'-5' oligoadenylate synthetase 1b (Oas1b) gene. Oas gene expression is up-regulated by interferon (IFN), and after activation by double-stranded RNA, some mouse synthetases produce 2-5A, which activates latent RNase L to degrade viral and cellular RNAs. To determine whether the lower levels of intracellular flavivirus genomic RNA from resistant mice detected in cells at all times after infection were mediated by RNase L, RNase L activity levels in congenic resistant and susceptible cells were compared. Similar moderate levels of RNase L activation by transfected 2-5A were observed in both types of uninfected cells. After WNV infection, the mRNAs of IFN-beta and three Oas genes were up-regulated to similar levels in both types of cells. However, significant levels of RNase L activity were not detected until 72 h after WNV infection and the patterns of viral RNA cleavage products generated were similar in both types of cells. When RNase L activity was down-regulated in resistant cells via stable expression of a dominant negative RNase L mutant, approximately 5- to 10-times-higher yields of WNV were produced. Similarly, about approximately 5- to 10-times-higher virus yields were produced by susceptible C57BL/6 RNase L-/- cells compared to RNase L+/+ cells that were either left untreated or pretreated with IFN and/or poly(I) . poly(C). The data indicate that WNV genomic RNA is susceptible to RNase L cleavage and that RNase L plays a role in the cellular antiviral response to flaviviruses. The results suggest that RNase L activation is not a major component of the Oas1b-mediated flavivirus resistance phenotype.

Modest induction of phase 2 enzyme activity in the F-344 rat prostate

BACKGROUND

Prostate cancer is the most commonly diagnosed malignancy in men and is thought to arise as a result of endogenous oxidative stress in the face of compromised carcinogen defenses. We tested whether carcinogen defense (phase 2) enzymes could be induced in the prostate tissues of rats after oral feeding of candidate phase 2 enzyme inducing compounds.

METHODS

Male F344 rats were gavage fed sulforaphane, beta-naphthoflavone, curcumin, dimethyl fumarate or vehicle control over five days, and on the sixth day, prostate, liver, kidney and bladder tissues were harvested. Cytosolic enzyme activities of nicotinamide quinone oxidoreductase (NQO1), total glutathione transferase (using DCNB) and mu-class glutathione transferase (using CDNB) were determined in the treated and control animals and compared.

RESULTS

In prostatic tissues, sulforaphane produced modest but significant increases in the enzymatic activities of NQO1, total GST and GST-mu compared to control animals. beta-naphthoflavone significantly increased NQO1 and GST-mu activities and curcumin increased total GST and GST-mu enzymatic activities. Dimethyl fumarate did not significantly increase prostatic phase 2 enzyme activity. Compared to control animals, sulforaphane also significantly induced NQO1 or total GST enzyme activity in the liver, kidney and, most significantly, in the bladder tissues. All compounds were well tolerated over the course of the gavage feedings.

CONCLUSION

Orally administered compounds will induce modestly phase 2 enzyme activity in the prostate although the significance of this degree of induction is unknown. The 4 different compounds also altered phase 2 enzyme activity to different degrees in different tissue types. Orally administered sulforaphane potently induces phase 2 enzymes in bladder tissues and should be investigated as a bladder cancer preventive agent.

Human monogenic disorders — a source of novel drug targets

The decrease in new drug applications and approvals over the past several years results from an underlying crisis in drug target identification and validation. Model organisms are being used to address this problem, in combination with novel approaches such as the International HapMap Project. What has been underappreciated is that discovery of new drug targets can also be revived by traditional Mendelian genetics. A large fraction of the human gene repertoire remains phenotypically uncharacterized, and is likely to encode many unanticipated and novel phenotypes that will be of interest to pharmaceutical and biotechnological drug developers.

RNASEL Mutation Screening and Association Study in Ashkenazi and Non-Ashkenazi Prostate Cancer Patients

Epidemiologic and genetic studies support the considerable effect of heritable factors on prostate tumorigenesis, although to date, no unequivocal susceptibility gene has been identified. The extensive study of RNASEL in prostate cancer patients worldwide has yielded conflicting results. We reevaluated the role of the RNASEL 471delAAAG Ashkenazi founder mutation in 1,642 Ashkenazi patients with prostate, bladder, breast/ovarian, and colon cancers; Ashkenazi controls; and in non-Ashkenazi prostate cancer patients and controls. The entire RNASEL coding sequence was also screened using denaturing high-performance liquid chromatography and multiplex ligation-dependent probe amplification for possible sequence variations or copy number changes in a population of prostate cancer patients. The 471delAAAG mutation was detected in 2.4% of the Ashkenazi prostate cancer patients; in 1.9% of patients with bladder, breast/ovarian, and colon cancers; and in 2.0% of the Ashkenazi controls. Seven additional variants were detected in RNASEL, including a novel potentially pathogenic splice site mutation, IVS5+1delG, although none were associated with increased prostate cancer risk. Multiplex ligation-dependent probe amplification analysis showed two RNASEL gene copies in all 300 prostate cancer patients tested. We estimated that the RNASEL 471delAAAG founder mutation, which was detected in 2% of the Ashkenazi Jews, originated between the 2nd and 5th centuries A.D., compared with the less frequent (1%) BRCA1 185delAG founder mutation, which originated hundreds of years earlier. Taken together, our analysis does not support a role for the RNASEL 471delAAAG Ashkenazi mutation nor for the other alterations detected in RNASEL in prostate cancer risk in Jewish men.

Identification of a novel Gammaretrovirus in prostate tumors of patients homozygous for R462Q RNASEL variant

Ribonuclease L (RNase L) is an important effector of the innate antiviral response. Mutations or variants that impair function of RNase L, particularly R462Q, have been proposed as susceptibility factors for prostate cancer. Given the role of this gene in viral defense, we sought to explore the possibility that a viral infection might contribute to prostate cancer in individuals harboring the R462Q variant. A viral detection DNA microarray composed of oligonucleotides corresponding to the most conserved sequences of all known viruses identified the presence of gammaretroviral sequences in cDNA samples from seven of 11 R462Q-homozygous (QQ) cases, and in one of eight heterozygous (RQ) and homozygous wild-type (RR) cases. An expanded survey of 86 tumors by specific RT-PCR detected the virus in eight of 20 QQ cases (40%), compared with only one sample (1.5%) among 66 RQ and RR cases. The full-length viral genome was cloned and sequenced independently from three positive QQ cases. The virus, named XMRV, is closely related to xenotropic murine leukemia viruses (MuLVs), but its sequence is clearly distinct from all known members of this group. Comparison of gag and pol sequences from different tumor isolates suggested infection with the same virus in all cases, yet sequence variation was consistent with the infections being independently acquired. Analysis of prostate tissues from XMRV-positive cases by in situ hybridization and immunohistochemistry showed that XMRV nucleic acid and protein can be detected in about 1% of stromal cells, predominantly fibroblasts and hematopoietic elements in regions adjacent to the carcinoma. These data provide to our knowledge the first demonstration that xenotropic MuLV-related viruses can produce an authentic human infection, and strongly implicate RNase L activity in the prevention or clearance of infection in vivo. These findings also raise questions about the possible relationship between exogenous infection and cancer development in genetically susceptible individuals.

Genome-wide linkage scan for prostate cancer susceptibility genes in men with aggressive disease: significant evidence for linkage at chromosome 15q12

Epidemiological and twin studies have consistently demonstrated a strong genetic component to prostate cancer (PCa) susceptibility. To date, numerous linkage studies have been performed to identify chromosomal regions containing PCa susceptibility genes. Unfortunately, results from these studies have failed to form any obvious consensus regarding which regions are most likely to contain genes that may contribute to PCa predisposition. One plausible explanation for the difficulty in mapping susceptibility loci is the existence of considerable heterogeneity in the phenotype of PCa, with significant variation in clinical stage and grade of disease even among family members. To address this issue, we performed a genome-wide linkage scan on 71 informative families with two or more men with aggressive PCa. When only men with aggressive PCa were coded as affected, statistically significant evidence for linkage at chromosome 15q12 was detected (LOD=3.49; genome-wide p=0.005). Furthermore, the evidence for linkage increased when analyses were restricted to Caucasian-American pedigrees (n=65; LOD=4.05) and pedigrees with two confirmed aggressive cases (n=42, LOD=4.76). Interestingly, a 1-LOD support interval about our peak at 15q12 overlaps a region of suggestive linkage, 15q11, identified by a recent linkage study on 1,233 PCa families by the International Consortium for Prostate Cancer Genetics. Using a more rigid definition of PCa in linkage studies will result in a severe reduction in sample sizes available for study, but may ultimately prove to increase statistical power to detect susceptibility genes for this multigenic trait.

Agents in development for prostate cancer prevention

Accumulated epidemiological evidence indicates that prostate cancer mortality should be preventable. As androgenic hormones have long been recognised to be required for normal prostatic development, and because androgen deprivation is an established treatment for advanced prostate cancer, androgen signalling has been an attractive target for prostate cancer prevention. Inhibitors of 5alpha-reductase, an enzyme necessary for the conversion of testosterone to the more potent androgen dihydrotestosterone, have reached pivotal clinical trials for prostate cancer prevention. In addition, new insights into the molecular pathogenesis of prostate cancer hint that chronic or recurrent prostate inflammation may contribute to the development of the disease. A variety of antioxidants and anti-inflammatory drugs, which are likely to be capable of attenuating pro-carcinogenic genome damage from reactive oxygen and nitrogen species, are also under current development for prostate cancer prevention. This review will consider the rational development of these and other new agents and approaches for prostate cancer prevention in the context of recent research progress in ascertaining the aetiology of prostate cancer.

RNASEL germline variants are associated with pancreatic cancer

The RNASEL (encoding ribonuclease L) gene Glu265X mutation has been implicated in familial prostate cancer, and an association between the RNASEL Arg462Gln variant and sporadic and familial prostate cancer, has also been suggested. Because prostate cancer occurs in some familial pancreatic cancer families, we evaluated the role of the RNASEL gene variants Glu265X and Arg462Gln in the etiology of pancreatic cancer. Exon 2 of the RNASEL gene was directly sequenced in the germline of 36 familial and 75 sporadic pancreatic cancer patients and in 108 controls. The Glu265X mutation was identified in one (2.8%) familial and one (1.3%) sporadic pancreatic cancer case, but not in any of the controls. Arg462Gln variants were identified in 61 (56%) controls and in 55 (73%) sporadic pancreatic cancer cases with 8 (7%) and 12 (16%) homozygotes, respectively (p = 0.009). For homozygous carriers the increased risk for pancreatic cancer was 3.5 (odds ratio [OR] = 3.53, 95% confidence interval [CI] = 1.11-11.46, p = 0.03). The population attributable fraction (PAF) was 38.7% (95% CI = 0.08-0.80). In familial pancreatic cancer no association between Arg462Gln genotypes and pancreatic cancer risk was evident. In sporadic pancreatic cancer there were no significant differences between Arg462Gln genotypes regarding clinical characteristics. In familial pancreatic cancer, however, patients with Arg462Gln variants had more aggressive tumors with more high grade cancers (OR = 15.40, p = 0.009) and more distant metastases (OR = 7.00, p = 0.04) than patients with the wild-type genotype. Our results suggest that RNASEL variants Glu265X and Arg462Gln may contribute to the tumorigenesis of sporadic and familial pancreatic cancer, which has to be proven in large scale studies.

Association of hereditary prostate cancer gene polymorphic variants with sporadic aggressive prostate carcinoma

BACKGROUND

ELAC2, MSR1, and RNASEL are candidate genes for hereditary prostate carcinoma (HPC). While, studies have demonstrated that single nucleotide polymorphisms (SNPs) in these genes are associated with sporadic disease as well as HPC, these results are often not replicated in follow-up studies. Given that the majority of patients studied had localized disease and up to 50% of localized prostate cancer is clinically insignificant, the inability to replicate the initial findings may reflect that some subjects had indolent tumors. Herein, we examine patients with metastatic disease to determine if an association exists between HPC SNPs and unambiguously significant prostate cancer.

METHODS

We examined polymorphisms within ELAC2 (S217L, A541T, E622V), MSR1 (P275A, R293X, aIVS5-59c), and RNASEL (E265X, R462Q, D541E) in 150 European-Americans with metastatic prostate cancer and 170 prostate cancer-free controls using pyrosequencing assays.

RESULTS

Only ELAC2 217L (37% cases vs. 29% controls (P=0.034)) and RNASEL 541E (61% cases vs. 53% controls (P=0.045)) were over-represented. Analysis of genotypes revealed that presence of the leucine ELAC2 allele (OR 1.54: 95% CI=0.99-2.41, SS vs. SL, LL) and homozygosity for the glutamic acid RNASEL allele (OR 1.68: 95% CI=1.04-2.70, EE vs. DE, DD) were associated with increased risk. Patients with both genotypes were of particularly high-risk (OR 2.66: 95% CI=1.36-5.19).

CONCLUSIONS

These results suggest that, in a European-American population, ELAC2 217L and RNASEL 541E are associated with metastatic sporadic disease. ELAC2 and RNASEL SNP analysis may prove useful in determining which patients are at risk for developing clinically significant prostate carcinoma.

Prevalent mutations in prostate cancer

Quantitative and structural genetic alterations cause the development and progression of prostate cancer. A number of genes have been implicated in prostate cancer by genetic alterations and functional consequences of the genetic alterations. These include the ELAC2 (HPC2), MSR1, and RNASEL (HPC1) genes that have germline mutations in familial prostate cancer; AR, ATBF1, EPHB2 (ERK), KLF6, mitochondria DNA, p53, PTEN, and RAS that have somatic mutations in sporadic prostate cancer; AR, BRCA1, BRCA2, CHEK2 (RAD53), CYP17, CYP1B1, CYP3A4, GSTM1, GSTP1, GSTT1, PON1, SRD5A2, and VDR that have germline genetic variants associated with either hereditary and/or sporadic prostate cancer; and ANXA7 (ANX7), KLF5, NKX3-1 (NKX3.1), CDKN1B (p27), and MYC that have genomic copy number changes affecting gene function. More genes relevant to prostate cancer remain to be identified in each of these gene groups. For the genes that have been identified, most need additional genetic, functional, and/or biochemical examination. Identification and characterization of these genes will be a key step for improving the detection and treatment of prostate cancer.

Genomic search for prostate cancer predisposition loci in Utah pedigrees

BACKGROUND

We report a genome linkage scan in extended Utah pedigrees, utilizing a pedigree-splitting approach to reduce intra-familial heterogeneity.

METHODS

Fifty-nine pedigrees with at least four Prostate cancer (PrCa) cases and no more than two meioses separating PrCa cases were analyzed using the CIDR genomic search STRP marker set. Parametric linkage analyses using dominant and recessive models were performed on four datasets resulting from a pedigree splitting algorithm. In addition, age at diagnosis subset analyses were performed.

RESULTS

Four regions of interest (LODs>1.9) were identified on chromosomes 1p, 3q, 5q, and 22q. The linkage peaks on 1p, 3q, and 22q have been previously implicated for PrCa, though not significantly. The 1p region was supported by a single large Utah pedigree with a multipoint LOD score of 3.1. An additional 10 regions gave LOD scores>1.22 (nominal linkage evidence), including moderate evidence supporting the HPC20 region with a recessive model.

CONCLUSIONS

Our genome-wide search in the informative, extended Utah pedigrees continues to illustrate an ability to identify and replicate linkage peaks, and supports four regions of interest for PrCa predisposition genes.

The Interaction of Four Genes in the Inflammation Pathway Significantly Predicts Prostate Cancer Risk

It is widely hypothesized that the interactions of multiple genes influence individual risk to prostate cancer. However, current efforts at identifying prostate cancer risk genes primarily rely on single-gene approaches. In an attempt to fill this gap, we carried out a study to explore the joint effect of multiple genes in the inflammation pathway on prostate cancer risk. We studied 20 genes in the Toll-like receptor signaling pathway as well as several cytokines. For each of these genes, we selected and genotyped haplotype-tagging single nucleotide polymorphisms (SNP) among 1,383 cases and 780 controls from the CAPS (CAncer Prostate in Sweden) study population. A total of 57 SNPs were included in the final analysis. A data mining method, multifactor dimensionality reduction, was used to explore the interaction effects of SNPs on prostate cancer risk. Interaction effects were assessed for all possible n SNP combinations, where n = 2, 3, or 4. For each n SNP combination, the model providing lowest prediction error among 100 cross-validations was chosen. The statistical significance levels of the best models in each n SNP combination were determined using permutation tests. A four-SNP interaction (one SNP each from IL-10, IL-1RN, TIRAP, and TLR5) had the lowest prediction error (43.28%, P = 0.019). Our ability to analyze a large number of SNPs in a large sample size is one of the first efforts in exploring the effect of high-order gene-gene interactions on prostate cancer risk, and this is an important contribution to this new and quickly evolving field.

Review: Milstein Award lecture: interferons and cancer: where from here?

Interferons (IFNs) remain the most broadly active cytokines for cancer treatment, yet ones for which the full potential is not reached. IFNs have impacted positively on both quality and quantity of life for hundreds of thousands of cancer patients with chronic leukemia, lymphoma, bladder carcinoma, melanoma, and renal carcinoma. The role of the IFN system in malignant pathogenesis continues to enhance understanding of how the IFN system may be modulated for therapeutic advantage. Reaching the full potential of IFNs as therapeutics for cancer will also result from additional understanding of the genes underlying apoptosis induction, angiogenesis inhibition, and influence on immunologic function. Food and Drug Administration (FDA) approval of IFNs occurred less than 20 years ago; after 40 years, third-generation products of early cytotoxics, such as 5- fluorouracil (5FU), are beginning to reach clinical approval. Thus, substantial potential exists for additional application of IFNs and IFN inducers as anticancer therapeutics, particularly when one considers that their pleiotropic cellular and molecular effects have yet to be fully defined.

A transcriptional signaling pathway in the IFN system mediated by 2'-5'-oligoadenylate activation of RNase L

Virus replication in higher vertebrates is restrained by IFNs that cause cells to transcribe genes encoding antiviral proteins, such as 2'-5' oligoadenylate synthetases. 2'-5' oligoadenylate synthetase is stimulated by dsRNA to produce 5'-phosphorylated, 2'-5'-linked oligoadenylates (2-5A), whose function is to activate RNase L. Although RNase L is required for a complete IFN antiviral response and mutations in the RNase L gene (RNASEL or HPC1) increase prostate cancer rates, it is unknown how 2-5A affects these biological endpoints through its receptor, RNase L. Presently, we show that 2-5A activation of RNase L produces a remarkable stimulation of transcription (>/=20-fold) for genes that suppress virus replication and prostate cancer. Unexpectedly, exposure of DU145 prostate cancer cells to physiologic levels of 2-5A (0.1 muM) induced approximately twice as many RNA species as it down-regulated. Among the 2-5A-induced genes are several IFN-stimulated genes, including IFN-inducible transcript 1/P56, IFN-inducible transcript 2/P54, IL-8, and IFN-stimulated gene 15. 2-5A also potently elevated RNA for macrophage inhibitory cytokine-1/nonsteroidal antiinflammatory drug-activated gene-1, a TGF-beta superfamily member implicated as an apoptotic suppressor of prostate cancer. Transcriptional signaling to the macrophage inhibitory cytokine-1/nonsteroidal antiinflammatory drug-activated gene-1 promoter by 2-5A was deficient in HeLa cells expressing a nuclease-dead mutant of RNase L and was dependent on the mitogen-activated protein kinases c-Jun N-terminal kinase and extracellular signal-regulated kinase, both of which were activated in response to 2-5A treatments. Because 2-5A and RNase L participate in defenses against viral infections and prostate cancer, our findings have implications for basic cellular mechanisms that control major pathogenic processes.

Mapping of the human RNASEL promoter and expression in cancer and normal cells

2',5'-Oligoadenylate (2-5A)-dependent RNase L is a ubiquitous endoribonuclease of higher vertebrates that functions in the interferon (IFN) antiviral response by degrading both viral and cellular single-stranded RNA (ssRNA). In addition, the RNase L gene, RNASEL, was mapped to the hereditary prostate cancer 1 (HPC1) gene. Previous analyses of human RNASEL determined its exon/intron structure but lacked a description of the promoter region. We thus mapped the RNASEL transcriptional start site using 5'-rapid amplification of cDNA ends (5'-RACE) and primer extension methods with RNA from human histiocytic lymphoma U937 cells. The promoter sequence was analyzed for potential transcription factor binding sites. Although a canonical IFN-gamma activation site (GAS) element (TTCCAAGAA) was identified (nucleotides -155 to -147), there was only slight induction of RNASEL promoter-reporter activity or of endogenous RNase L expression in response to IFN-alpha or IFN-gamma. Several sites for tissue-specific and general promoters were observed, however, which could explain the widespread expression of RNase L in mammalian cells. Accordingly, RNase L levels were determined and compared in different human and rodent cancer and normal cell types using a radiolabeled 2-5A derivative. In addition, levels of RNase L were established in various normal human tissues and cell types by immunoblotting and immunohistochemistry. Our findings are the first description of the human RNASEL promoter that allows constituitive expression in a range of normal and neoplastic cell types.

Structural elucidation of A-74528, an inhibitor for 2′,5′-phosphodiesterase isolated from Streptomyces sp

A-74528 (1) is a metabolite of Streptomyces sp. discovered in the screening for 2',5'-oligoadenylate phosphodiesterase inhibitors. The planar structure of 1 was mainly elucidated by NMR techniques including natural abundance INADEQUATE, and the relative configuration and the conformation were elucidated by the analyses of NOEs and assessment of dihedral angles predicted by QUANTA/CHARMm computations and coupling constants. It was proved that 1 is a highly fused polyketide with a side-chain branching site that never appeared before from the nature.

Nucleotide variations in genes encoding plasminogen activator inhibitor-2 and serine proteinase inhibitor B10 associated with prostate cancer

Genes encoding the serine proteinase inhibitor B family (SERPINBs) are mainly clustered on human chromosome 18 (18q21). Several serpins are known to affect malignant phenotypes of tumor cells, so aberrant genetic variants in this molecular family are candidates for conferring susceptibility for risk of cancer. We investigated whether eight selected non-synonymous variations within SERPINB loci at 18q21 might be associated with risk of prostate cancer in Japanese men. A case-control study involving 292 prostate-cancer patients and 384 controls revealed significant differences in regard to distribution of four missense variations in genes encoding plasminogen activator inhibitor 2 (PAI2) and SERPINB10. The most significant association was detected for the N120D polymorphism in the PAI2 gene (P = 5.0 x 10(-5)); men carrying the 120-N allele (120-N/N and 120-N/D genotypes) carried a 2.4-fold increased risk of prostate cancer (95% confidence interval 1.45-4.07). Associations were also detected for three other missense polymorphisms in those two genes. Strong linkage disequilibrium in the region encompassing PAI2 and SERPINB10 extended to about 50 kbp. The results suggested that missense variations in one or both of these genes confer important risks for prostate cancer, and may be themselves tumorigenic. Although confirmative replication studies on larger cohorts are awaited, clinical examination of these variations may become useful for identifying individuals at high risk for prostate cancer.

The 2,5 oligoadenylate synthetase/RNaseL pathway is a novel effector of BRCA1- and interferon-gamma-mediated apoptosis

BRCA1 has been reported to have roles in DNA damage repair, cell cycle checkpoint control, transcriptional regulation and ubiquitination. We have previously demonstrated that BRCA1 is a potent activator of a subset of interferon (IFN)-regulated genes and that BRCA1 synergistically activated a number of these genes in the presence of IFN-gamma, but not type I IFNs. Here we report that one of these targets, 2,5 oligoadenylate synthetase (2,5 OAS), is a mediator of BRCA1/IFN-gamma-induced apoptosis. We show that the induction of 2,5 OAS in response to IFN-gamma is BRCA1 and STAT1 dependent. Consistent with a role as a negative regulator of proliferation, transient transfection of 2,5 OAS into breast cancer cell lines results in decreased colony growth and apoptosis. Furthermore we show that IFN-gamma-induced apoptosis is dependent on functional BRCA1 and STAT1 and we demonstrate that IFN-gamma-induced apoptosis is dependent on 2,5 OAS induction. 2,5 OAS is the only known upstream regulator of RNaseL, a recently identified hereditary prostate tumour suppressor gene implicated in apoptosis. We propose that BRCA1 may be an upstream regulator of RNaseL, acting in concert with IFN-gamma to transcriptionally activate 2,5 OAS, leading to the downstream activation of RNaseL and apoptosis.

Interaction between the androgen receptor and RNase L mediates a cross-talk between the interferon and androgen signaling pathways

Signaling by androgens and interferons (IFN) plays an important role in prostate cancer initiation and progression. Using microarray analysis, we describe here a functional cross-talk between dihydrotestosterone and interferon signaling. Glutathione S-transferase pull-down and co-immunoprecipitation experiments reveal that the androgen receptor and the interferon-activated RNase L interact with each other in a ligand-dependent manner. Furthermore, overexpression of wild type RNase L confers IFN sensitivity to a dihydrotestosterone-inducible reporter gene, whereas R462Q-mutated RNase L does not. Based on our data we hypothesize that in 22RV1 cells, activated androgen receptor (AR) contributes to the insensitivity to IFN of the cell. Accordingly, we show that AR knockdown restores responsiveness to IFNgamma. Our findings support a model in which both the activation of AR and the down-regulation of IFN signaling can synergize to promote cell survival and suppress apoptosis. This model provides the molecular basis to understand how mutated RNase L can lead to early onset PCa and illustrates how inflammatory cytokines and nuclear hormone signaling contribute to tumor development.

Molecular pathology of prostate cancer

The molecular pathology of prostate cancer is complex; not only are multiple genes involved in its pathogenesis, but additional environmental factors such as diet and inflammation are also involved. The exhaustive research into prostate cancer to date has demonstrated a complex interaction of multiple genes and environmental factors, some of which may be more important in individual prostate cancer cases. This is an exciting era, with the emergence of new investigative tools such as DNA microarray technology and the application of the field of proteomics to the study of human cancers. Knowledge of genetic changes underlying the initiation, development, and progression of prostate cancer is accumulating rapidly. With increasing knowledge, it may be possible to distinguish indolent from aggressive prostate tumours by molecular fingerprinting. This review discusses the most consistently reported molecular pathological findings in hereditary and sporadic prostate cancer, together with new concepts and technologies.

Molecular pathology of prostate cancer

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

Identifying Susceptibility Genes for Prostate Cancer--A Family-Based Association Study of Polymorphisms in CYP17, CYP19, CYP11A1, and LH-

Polymorphisms in genes that code for enzymes or hormones involved in the synthesis and metabolism of androgens are compelling biological candidates for prostate cancer. Four such genes, CYP17, CYP19, CYP11A1, and LH-beta, are involved in the synthesis and conversion of testosterone to dihydrotestosterone and estradiol. In a study of 715 men with and without prostate cancer from 266 familial and early-onset prostate cancer families, we examined the association between prostate cancer susceptibility and common single-nucleotide polymorphisms in each of these four candidate genes. Family-based association tests revealed a significant association between prostate cancer and a common single-nucleotide polymorphism in CYP17 (P=0.004), with preferential transmission of the minor allele to unaffected men. Conditional logistic regression analysis of 461 discordant sibling pairs from these same families reaffirmed the association between the presence of the minor allele in CYP17 and prostate cancer risk (odds ratio, 0.51; 95% confidence interval, 0.28-0.92). These findings suggest that variation in or around CYP17 predicts susceptibility to prostate cancer. Family-based association tests may be especially valuable in studies of genetic variation and prostate cancer risk because this approach minimizes confounding due to population substructure, which is of particular concern for prostate cancer given the tremendous variation in the worldwide incidence of this disease.

Arg462Gln sequence variation in the prostate-cancer-susceptibility gene RNASEL and age of onset of hereditary non-polyposis colorectal cancer: a case-control study

BACKGROUND

RNASEL is thought to be a susceptibility gene for hereditary prostate cancer and encodes the endoribonuclease RNase L, which has a role in apoptosis and is a candidate tumour-suppressor protein. A common sequence variation in RNASEL, Arg462Gln, has been associated with hereditary and sporadic prostate cancer, and the Gln variant has about three-fold reduced RNase activity in vitro. In view of the association between the age of onset of hereditary non-polyposis colorectal cancer and functionally different variants of P53, which play a key part in the apoptotic pathway, we aimed to assess whether the Arg462Gln variation of RNASEL affects the age of onset of hereditary non-polyposis colorectal cancer.

METHODS

We screened 251 patients with hereditary non-polyposis colorectal cancer who were unrelated, had pathogenic germline mutations in MSH2 (n=141) or MLH1 (n=110), and had colorectal carcinoma as the first tumour, for variation at codon 462 of RNASEL and compared them with 439 healthy controls.

FINDINGS

The median age of onset was 40 years (range 17-75) for patients with an Arg/Arg genotype at codon 462, 37 years (13-69) for patients with an Arg/Gln genotype, and 34 years (20-49) for those with a Gln/Gln genotype (p=0.0198). Only the RNASEL genotype had a significant effect on age of onset (p=0.0062) in an additive mode of inheritance. Pair-wise comparisons between genotype groups showed that the two homozygous groups (ie, Arg/Arg vs Gln/Gln) differed significantly in age of disease onset (mean age difference 4.8 years [SD 1.7], p=0.0044).

INTERPRETATION

A sequence variation in the prostate-cancer-susceptibility gene RNASEL has a role in a different, unassociated malignant disease. Genotypes at RNASEL codon 462 are associated with age of onset of hereditary non-polyposis colorectal cancer in a dose-dependent way, and might have a role in preventive strategies for this disease.

A combined genomewide linkage scan of 1,233 families for prostate cancer-susceptibility genes conducted by the international consortium for prostate cancer genetics

Evidence of the existence of major prostate cancer (PC)-susceptibility genes has been provided by multiple segregation analyses. Although genomewide screens have been performed in over a dozen independent studies, few chromosomal regions have been consistently identified as regions of interest. One of the major difficulties is genetic heterogeneity, possibly due to multiple, incompletely penetrant PC-susceptibility genes. In this study, we explored two approaches to overcome this difficulty, in an analysis of a large number of families with PC in the International Consortium for Prostate Cancer Genetics (ICPCG). One approach was to combine linkage data from a total of 1,233 families to increase the statistical power for detecting linkage. Using parametric (dominant and recessive) and nonparametric analyses, we identified five regions with "suggestive" linkage (LOD score >1.86): 5q12, 8p21, 15q11, 17q21, and 22q12. The second approach was to focus on subsets of families that are more likely to segregate highly penetrant mutations, including families with large numbers of affected individuals or early age at diagnosis. Stronger evidence of linkage in several regions was identified, including a "significant" linkage at 22q12, with a LOD score of 3.57, and five suggestive linkages (1q25, 8q13, 13q14, 16p13, and 17q21) in 269 families with at least five affected members. In addition, four additional suggestive linkages (3p24, 5q35, 11q22, and Xq12) were found in 606 families with mean age at diagnosis of < or = 65 years. Although it is difficult to determine the true statistical significance of these findings, a conservative interpretation of these results would be that if major PC-susceptibility genes do exist, they are most likely located in the regions generating suggestive or significant linkage signals in this large study.

Mice deficient in oocyte-specific oligoadenylate synthetase-like protein OAS1D display reduced fertility

The double-stranded RNA (dsRNA)-induced interferon response is a defense mechanism against viral infection. Upon interferon activation by dsRNA, 2',5'-oligoadenylate synthetase 1 (OAS1A) is induced; it binds dsRNA and converts ATP into 2',5'-linked oligomers of adenosine (called 2-5A), which activate RNase L that in turn degrades viral and cellular RNAs. In a screen to identify oocyte-specific genes, we identified a novel murine cDNA encoding an ovary-specific 2',5'-oligoadenylate synthetase-like protein, OAS1D, which displays 59% identity with OAS1A. OAS1D is predominantly cytoplasmic and is exclusively expressed in growing oocytes and early embryos. Like OAS1A, OAS1D binds the dsRNA mimetic poly(I-C), but unlike OAS1A, it lacks 2'-5' adenosine linking activity. OAS1D interacts with OAS1A and inhibits the enzymatic activity of OAS1A. Mutant mice lacking OAS1D (Oas1d(-/-)) display reduced fertility due to defects in ovarian follicle development, decreased efficiency of ovulation, and eggs that are fertilized arrest at the one-cell stage. These effects are exacerbated after activation of the interferon/OAS1A/RNase L pathway by poly(I-C). We propose that OAS1D suppresses the interferon/OAS/RNase L-mediated cellular destruction by interacting with OAS1A during oogenesis and early embryonic development.

A genomewide linkage analysis for prostate cancer susceptibility genes in families from Germany

Prostate cancer is a complex disease with a substantial genetic contribution involved in the disease risk. Several genomewide linkage studies conducted so far have demonstrated a strong heterogeneity of susceptibility. In order to assess candidate regions that are particularly relevant for the German population, we performed a genomewide linkage search on 139 prostate cancer families. A nonparametric method (Zlr scores), using GENEHUNTERPLUS, was applied at 500 markers (panel P1400, deCODE), with an average spacing of 7.25 cM. In the entire family collection, linkage was most evident at 8p22 (Zlr=2.47, P=0.0068), close to the previously identified susceptibility gene MSR1. Further local maxima with Zlr>2 (P<0.025) were observed at 1q, 5q and 15q. In a subgroup of 47 families, which matched the Johns Hopkins criteria of hereditary prostate cancer, suggestive linkage was found on 1p31 (Zlr=3.37, P=0.00038), a previously not described candidate region. The remaining 92 pedigrees, with no strong disease history, revealed a maximum Zlr=3.15 (P=0.00082) at 8q13, possibly indicating a gene with reduced penetrance or recessive inheritance. Our results suggest pronounced locus heterogeneity of prostate cancer susceptibility in Germany. In the present study population, the MSR1 gene could play a significant role. Other conspicuous loci, like 1p31 and 8q13, need further investigation in order to verify their relevance and to identify candidate genes.

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.

Modulation of CXCL14 (BRAK) expression in prostate cancer

BACKGROUND

Recent studies suggest inflammatory processes may be involved in the development or progression of prostate cancer. Chemokines are a family of cytokines that can play several roles in cancer progression including angiogenesis, inflammation, cell recruitment, and migration.

METHODS

Real-time quantitative RT-PCR, in situ RNA hybridization, laser capture microscopy, immunohistochemistry, and cDNA array based technologies were used to examine CXCL14 (BRAK) expression in paired normal and tumor prostate. To determine the role CXCL14 expression has on cancer progression, LAPC4 cells were engineered to overexpress mouse or human CXCL14, and xenograft studies were performed.

RESULTS

CXCL14 RNA expression was observed in normal and tumor prostate epithelium and focally in stromal cells adjacent to cancer. CXCL14 mRNA was significantly upregulated in localized prostate cancer and positively correlated with Gleason score. CXCL14 levels were unchanged in BPH specimens. LAPC4 cells expressing CXCL14 resulted in a 43% tumor growth inhibition (P = 0.019) in vivo compared to vector only xenografts.

CONCLUSIONS

CXCL14 mRNA upregulation is a common feature in prostate cancer. The finding that CXCL14 expression inhibits tumor growth suggests this gene has tumor suppressive functions.

Decreasing age at prostate cancer diagnosis over successive generations in prostate cancer families

BACKGROUND

The decline in age at prostate cancer diagnosis over the past decade is partially attributable to prostate specific antigen (PSA) screening. We examined age at diagnosis over successive generations within prostate cancer families.

METHODS

Families with at least two affected men were selected from the University of Michigan Prostate Cancer Genetics Project. The 1,345 individuals from 489 families were grouped into three generations.

RESULTS

Risk of prostate cancer diagnosis at a given age was estimated to increase 1.31 (95% CI: 1.13-1.51) times from one generation to the next. Among men diagnosed prior to the PSA era, inferences were similar (hazard ratio = 1.28, 95% CI: 0.97-1.68). No maternal versus paternal disease transmission effect was observed.

CONCLUSIONS

Age at prostate cancer diagnosis was observed to decrease over successive generations in families from an ongoing familial prostate cancer study. This finding, if confirmed, may have important implications for familial prostate cancer risk assessment.

Linkage and microarray analyses of susceptibility genes in ACI/Seg rats: a model for prostate cancers in the aged

ACI/Seg (ACI) rats develop prostate cancers spontaneously with aging, similar to humans. Here, to identify genes involved in prostate cancer susceptibility, we did linkage analysis and oligonucleotide microarray analysis. Linkage analysis was done using 118 effective rats, and prostate cancer susceptibility 1 (Pcs1), whose ACI allele dominantly induced prostate cancers, was mapped on chromosome 19 [logarithm of odds (LOD) score of 5.0]. PC resistance 1 (Pcr1), whose ACI allele dominantly and paradoxically suppressed the size of prostate cancers, was mapped on chromosome 2 (LOD score of 5.0). When linkage analysis was done in 51 rats with single or no macroscopic testicular tumors, which had larger prostates and higher testosterone levels than those with bilateral testicular tumors, Pcs2 and Pcr2 were mapped on chromosomes 20 and 1, respectively. By oligonucleotide microarray analysis with 8,800 probe sets and confirmation by quantitative reverse transcription-PCR, only two genes within these four loci were found to be differentially expressed >1.8-fold. Membrane metalloendopeptidase (Mme), known to inhibit androgen-independent growth of prostate cancers, on Pcr1 was expressed 2.0- to 5.5-fold higher in the ACI prostate, in accordance with its paradoxical effect. Cdkn1a on Pcs2 was expressed 1.5- to 4.5-fold lower in the ACI prostate. Additionally, genes responsible for testicular tumors and unilateral renal agenesis were mapped on chromosomes 11 and 14, respectively. These results showed that prostate cancer susceptibility of ACI rats involves at least four loci, and suggested Mme and Cdkn1a as candidates for Pcr1 and Pcs2.

A major locus for hereditary prostate cancer in Finland: localization by linkage disequilibrium of a haplotype in the HPCX region

BACKGROUND

Prostate cancer (PRCA) is the most common cancer in males in the western world. In Finland PRCA has an age-adjusted incidence of 81.5 per 100,000. We previously reported that in Finland, the late-onset cases in families with "no-male-to-male" (NMM) transmission of PRCA accounted for most of the linkage to the HPCX region (Xq27-28). The aim of the present study was to test for linkage disequilibrium (LD) and haplotype-sharing around marker DXS1205 between cases from hereditary prostate cancer (HPC) families and population controls. The initial allelic association was performed between 108 PRCA cases and 257 population controls genotyped for 23 markers in the Xq26-28 region. This resulted in a highly significant nominal one-sided Fisher's exact P-value of 0.0003 for allele ''180'' of marker DXS1205. Subsequently, a similar level of significance was observed for the same allele for marker DXS1205 (P=0.0002) when comparing 60 NMM cases and 257 controls. These results were still significant after Bonferroni correction for multiple testing. Fine mapping efforts included the genotyping of four additional markers D3S2390, bG82i1.9, bG82i1.1, bG82i1.0 and four single nucleotide polymorphisms (SNPs) to augment the original markers around DXS1205.

RESULTS

Our major finding is that markers extending from ''D3S2390'' to ''bG82i1.0'' flank the critical locus, about 150 kb. Levin and Bertell's LD measure (delta), a guide to localization of a possible variant, was 0.42 and 0.41 for alleles of markers bG82i1.9 and DXS1205, respectively.

CONCLUSIONS

In this study, the most significant haplotype comprised the three tightly linked, contiguous markers: ''cen-bG82i1.9-SNP-Hap B-bG82i1.1-tel'' [''197-2-234''] among several possible haplotypes (nominal Fisher's one-sided P=0.003). The two transcription units mapping within this interval are the LDOC1 and SPANXC genes. Positional cloning of the HPCX gene(s) is being facilitated by this exploration of the Xq26-28 region. This study represents the first report identifying a haplotype in the Xq27-28 region for an association between HPCX and X-linked prostate cancer with no-male-to-male transmission in the Finnish population.