Predisposition for TMPRSS2-ERG fusion in prostate cancer by variants in DNA repair genes

Acquired copy number variation in prostate tumours: a review of common somatic copy number alterations, how they are formed and their clinical utility

Prostate cancer is one of the most commonly diagnosed cancers in men and unfortunately, disease will progress in up to a third of patients despite primary treatment. Currently, there is a significant lack of prognostic tests that accurately predict disease course; however, the acquisition of somatic chromosomal variation in the form of DNA copy number variants may help understand disease progression. Notably, studies have found that a higher burden of somatic copy number alterations (SCNA) correlates with more aggressive disease, recurrence after surgery and metastasis. Here we will review the literature surrounding SCNA formation, including the roles of key tumour suppressors and oncogenes (PTEN, BRCA2, NKX3.1, ERG and AR), and their potential to inform diagnostic and prognostic clinical testing to improve predictive value. Ultimately, SCNAs, or inherited germline alterations that predispose to SCNAs, could have significant clinical utility in diagnostic and prognostic tests, in addition to guiding therapeutic selection.

Germline Genetic Variants Associated with Somatic TMPRSS2:ERG Fusion Status in Prostate Cancer: A Genome-Wide Association Study

BACKGROUND

The prostate cancer subtype defined by the presence of TMPRSS2:ERG has been shown to be molecularly and epidemiologically distinct. However, few studies have investigated germline genetic variants associating with TMPRSS2:ERG fusion status.

METHODS

We performed a genome-wide association study with 396 TMPRSS2:ERG(+) cases, 390 TMPRSS2:ERG(-) cases, and 2,386 cancer-free controls from the Physicians' Health Study (PHS), the Health Professionals Follow-up Study (HPFS), and a Seattle-based Fred Hutchinson (FH) Cancer Center Prostate Cancer Study. We applied logistic regression models to test the associations between ∼5 million SNPs with TMPRSS2:ERG fusion status accounting for population stratification.

RESULTS

We did not identify genome-wide significant variants comparing the TMPRSS2:ERG(+) to the TMPRSS2:ERG(-) prostate cancer cases in the meta-analysis. When comparing TMPRSS2:ERG(+) prostate cancer cases with controls without prostate cancer, 10 genome-wide significant SNPs on chromosome 17q24.3 were observed in the meta-analysis. When comparing TMPRSS2:ERG(-) prostate cancer cases with controls without prostate cancer, two SNPs on chromosome 8q24.21 in the meta-analysis reached genome-wide significance.

CONCLUSIONS

We observed SNPs at several known prostate cancer risk loci (17q24.3, 1q32.1, and 8q24.21) that were differentially and exclusively associated with the risk of developing prostate tumors either with or without the gene fusion.

IMPACT

Our findings suggest that tumors with the TMPRSS2:ERG fusion exhibit a different germline genetic etiology compared with fusion negative cases.

Identification of a novel recurrent EEF2 gene amplification in familial prostate tumors

Recurrent tumor copy number variations (CNVs) in prostate cancer (PrCa) have predominantly been discovered in sporadic tumor cohorts. Here, we examined familial prostate tumors for novel CNVs as prior studies suggest these harbor distinct CNVs. Array comparative genomic hybridization of 12 tumors from an Australian PrCa family, PcTas9, highlighted multiple recurrent CNVs, including amplification of EEF2 (19p13.3) in 100% of tumors. The EEF2 CNV was examined in a further 26 familial and seven sporadic tumors from the Australian cohort and in 494 tumors unselected for family history from The Cancer Genome Atlas (TCGA). EEF2 overexpression was observed in seven PcTas9 tumors, in addition to seven other predominantly familial tumors (n_total  = 34%). EEF2 amplification was only observed in 1.4% of TCGA tumors, however 7.5% harbored an EEF2 deletion. Analysis of genes co-expressed with EEF2 revealed significant upregulation of two genes, ZNF74 and ADSL, and downregulation of PLSCR1 in both EEF2 amplified familial tumors and EEF2 deleted TCGA tumors. Furthermore, in TCGA tumors, EEF2 amplification and deletion were significantly associated with a higher Gleason score. In summary, we identified a novel PrCa CNV that was predominantly amplified in familial tumors and deleted in unselected tumors. Our results provide further evidence that familial tumors harbor distinct CNVs, potentially due to an inherited predisposition, but also suggest that regardless of how EEF2 is dysregulated, a similar set of genes involved in key cancer pathways are impacted. Given the current lack of gene-based biomarkers and clinical targets in PrCa, further investigation of EEF2 is warranted.

Leveraging the replication stress response to optimize cancer therapy

High-fidelity DNA replication is critical for the faithful transmission of genetic information to daughter cells. Following genotoxic stress, specialized DNA damage tolerance pathways are activated to ensure replication fork progression. These pathways include translesion DNA synthesis, template switching and repriming. In this Review, we describe how DNA damage tolerance pathways impact genome stability, their connection with tumorigenesis and their effects on cancer therapy response. We discuss recent findings that single-strand DNA gap accumulation impacts chemoresponse and explore a growing body of evidence that suggests that different DNA damage tolerance factors, including translesion synthesis polymerases, template switching proteins and enzymes affecting single-stranded DNA gaps, represent useful cancer targets. We further outline how the consequences of DNA damage tolerance mechanisms could inform the discovery of new biomarkers to refine cancer therapies.

The tumor mutational landscape of BRCA2-deficient primary and metastatic prostate cancer

Carriers of germline BRCA2 pathogenic sequence variants have elevated aggressive prostate cancer risk and are candidates for precision oncology treatments. We examined whether BRCA2-deficient (BRCA2^d) prostate tumors have distinct genomic alterations compared with BRCA2-intact (BRCA2ⁱ) tumors. Among 2536 primary and 899 metastatic prostate tumors from the ICGC, GENIE, and TCGA databases, we identified 138 primary and 85 metastatic BRCA2^d tumors. Total tumor mutation burden (TMB) was higher among primary BRCA2^d tumors, although pathogenic TMB did not differ by tumor BRCA2 status. Pathogenic and total single nucleotide variant (SNV) frequencies at KMT2D were higher in BRCA2^d primary tumors, as was the total SNV frequency at KMT2D in BRCA2^d metastatic tumors. Homozygous deletions at NEK3, RB1, and APC were enriched in BRCA2^d primary tumors, and RB1 deletions in metastatic BRCA2^d tumors as well. TMPRSS2-ETV1 fusions were more common in BRCA2^d tumors. These results identify somatic alterations that hallmark etiological and prognostic differences between BRCA2^d and BRCA2ⁱ prostate tumors.

Analysis of a large prostate cancer family identifies novel and recurrent gene fusion events providing evidence for inherited predisposition

There is strong interest in the characterisation of gene fusions and their use to enhance clinical practices in prostate cancer (PrCa). Significantly, ~50% of prostate tumours harbour a gene fusion. Inherited factors are thought to predispose to these events but, to date, only one study has investigated gene fusions in a familial context. Here, we examined the prevalence and diversity of gene fusions in 14 tumours from a single large PrCa family, PcTas9, using the TruSight® RNA Fusion Panel and Sanger sequencing validation. These fusions were then explored in The Cancer Genome Atlas (TCGA) PrCa data set (n = 494). Overall, 64.3% of PcTas9 tumours harboured a gene fusion, including known erythroblast transformation-specific (ETS) fusions involving ERG and ETV1, and two novel gene fusions, C19orf48:ETV4 and RYBP:FOXP1. Although 3' ETS genes were overexpressed in PcTas9 and TCGA tumour samples, 3' fusion of FOXP1 did not appear to alter its expression. In addition, PcTas9 fusion carriers were more likely to have lower-grade disease than noncarriers (p = 0.02). Likewise, TCGA tumours with high-grade disease were less likely to harbour fusions (p = 0.03). Our study further implicates an inherited predisposition to PrCa gene fusion events, which are associated with less aggressive tumours. This knowledge could lead to clinical strategies to predict men at risk for fusion-positive PrCa and, thus, identify patients who are more or less at risk of aggressive disease and/or responsive to particular therapies.

DNA Polymerase and dRP-lyase activities of polymorphic variants of human Pol ι

Y-family DNA polymerase iota (Pol ι) is involved in DNA damage response and tolerance. Mutations and altered expression level of POLI gene are linked to a higher incidence of cancer. We biochemically characterized five active site polymorphic variants of human Pol ι: R71G (rs3218778), P118L (rs554252419), I236M (rs3218784), E251K (rs3218783) and P365R (rs200852409). We analyzed fidelity of nucleotide incorporation on undamaged DNA, efficiency and accuracy of DNA damage bypass, as well as 5'-deoxyribophosphate lyase (dRP-lyase) activity. The I236M and P118L variants were indistinguishable from the wild-type Pol ι in activity. The E251K and P365R substitutions altered the spectrum of nucleotide incorporation opposite several undamaged DNA bases. The P365R variant also reduced the dRP-lyase activity and possessed the decreased TLS activity opposite 8-oxo-G. The R71G mutation dramatically affected the catalytic activities of Pol ι. The reduced DNA polymerase activity of the R71G variant correlated with an enhanced fidelity of nucleotide incorporation on undamaged DNA, altered lesion-bypass activity and reduced dRP-lyase activity. Therefore, this amino acid substitution likely alters Pol ι functions in vivo.

Concomitant Pathogenic Mutations and Fusions of Driver Oncogenes in Tumors

Driver oncogene alterations have always been one of leading causes in the process of occurrence and development of tumors. And the effects of driver oncogene alterations on tumorigenesis and progression in different kinds of tumors have been studied heatedly. And the roles that the driver oncogenes alterations play have been elucidated clearly in previous studies. The phenomenon of concomitant driver oncogenes mutations and driver genes fusions has gained much concentration in the past two decades. And a growing number of studies reported this phenomenon, either coexistence or mutually exclusivity. Here we reviewed on the phenomenon of concomitant mutations in three common types of carcinomas—lung cancer, thyroid cancer, and leukemia, which have been studied relatively more detailed and more general compared with others.

DNA damage induces Yap5-dependent transcription of ECO1/CTF7 in Saccharomyces cerevisiae

Yeast Eco1 (ESCO2 in humans) acetyltransferase converts chromatin-bound cohesins to a DNA tethering state, thereby establishing sister chromatid cohesion. Eco1 establishes cohesion during DNA replication, after which Eco1 is targeted for degradation by SCF E3 ubiquitin ligase. SCF E3 ligase, and sequential phosphorylations that promote Eco1 ubiquitination and degradation, remain active throughout the M phase. In this way, Eco1 protein levels are high during S phase, but remain low throughout the remaining cell cycle. In response to DNA damage during M phase, however, Eco1 activity increases-providing for a new wave of cohesion establishment (termed Damage-Induced Cohesion, or DIC) which is critical for efficient DNA repair. To date, little evidence exists as to the mechanism through which Eco1 activity increases during M phase in response to DNA damage. Possibilities include that either the kinases or E3 ligase, that target Eco1 for degradation, are inhibited in response to DNA damage. Our results reveal instead that the degradation machinery remains fully active during M phase, despite the presence of DNA damage. In testing alternate models through which Eco1 activity increases in response to DNA damage, the results reveal that DNA damage induces new transcription of ECO1 and at a rate that exceeds the rate of Eco1 turnover, providing for rapid accumulation of Eco1 protein. We further show that DNA damage induction of ECO1 transcription is in part regulated by Yap5-a stress-induced transcription factor. Given the role for mutated ESCO2 (homolog of ECO1) in human birth defects, this study highlights the complex nature through which mutation of ESCO2, and defects in ESCO2 regulation, may promote developmental abnormalities and contribute to various diseases including cancer.

Ubiquitin and Ubiquitin-Like Proteins Are Essential Regulators of DNA Damage Bypass

Simple Summary

Ubiquitin and ubiquitin-like proteins are conjugated to many other proteins within the cell, to regulate their stability, localization, and activity. These modifications are essential for normal cellular function and the disruption of these processes contributes to numerous cancer types. In this review, we discuss how ubiquitin and ubiquitin-like proteins regulate the specialized replication pathways of DNA damage bypass, as well as how the disruption of these processes can contribute to cancer development. We also discuss how cancer cell survival relies on DNA damage bypass, and how targeting the regulation of these pathways by ubiquitin and ubiquitin-like proteins might be an effective strategy in anti-cancer therapies.

Abstract

Many endogenous and exogenous factors can induce genomic instability in human cells, in the form of DNA damage and mutations, that predispose them to cancer development. Normal cells rely on DNA damage bypass pathways such as translesion synthesis (TLS) and template switching (TS) to replicate past lesions that might otherwise result in prolonged replication stress and lethal double-strand breaks (DSBs). However, due to the lower fidelity of the specialized polymerases involved in TLS, the activation and suppression of these pathways must be tightly regulated by post-translational modifications such as ubiquitination in order to limit the risk of mutagenesis. Many cancer cells rely on the deregulation of DNA damage bypass to promote carcinogenesis and tumor formation, often giving them heightened resistance to DNA damage from chemotherapeutic agents. In this review, we discuss the key functions of ubiquitin and ubiquitin-like proteins in regulating DNA damage bypass in human cells, and highlight ways in which these processes are both deregulated in cancer progression and might be targeted in cancer therapy.

Three Human Pol ι Variants with Impaired Polymerase Activity Fail to Rescue H2O2 Sensitivity in POLI-Deficient Cells

Human Y-family DNA polymerase (pol) ι is involved in translesion DNA synthesis (TLS) and base excision repair (BER) of oxidative DNA damage. Genetic variations may alter the function of pol ι and affect cellular susceptibility to oxidative genotoxic agents, but their effects remain unclear. We investigated the impacts of 10 human missense germline variations on pol ι function by biochemical and cell-based assays. Both polymerase and deoxyribose phosphate (dRP) lyase activities were determined utilizing recombinant pol ι (residues 1-445) proteins. The K209Q, K228I, and Q386R variants showed 4- to 53-fold decreases in specificity constants (k_cat/K_m) for dCTP insertion opposite G and 8-oxo-7,8-dihydroguanine compared to the wild-type. The R126C and K345E variants showed wild-type-like polymerase activity, although these two variants (as well as the R209Q, K228I, and Q386R variants) showed greater than 6-fold decreases in dRP lyase activity compared to the wild-type. A CRISPR/Cas9-mediated POLI knockout conferred higher sensitivity to H₂O₂ in human embryonic kidney (HEK293) cells. Exogenous expression of the full-length wild-type, R126C, and K345E variants fully rescued the H₂O₂ sensitivity in POLI-deficient cells, while full-length R209Q, K228I, and Q386R variants did not rescue the sensitivity. Our results indicate that the R126C and K345E variants (having wild-type-like polymerase activity, albeit impaired in dRP lyase activity) could fully rescue the H₂O₂ sensitivity in POLI-deficient cells, while the R209Q, K228I, and Q386R variants, all impaired in polymerase and dRP lyase activity, failed to rescue the sensitivity, indicating the relative importance of TLS-related polymerase function of pol ι rather than its BER-related dRP lyase function in protection from oxidative stress. The possibility exists that the hypoactive pol ι variants increase the individual susceptibility to oxidative genotoxic agents.

TheXRCC4rs1805377 polymorphism is not associated with the risk of cancer: An updated meta-analysis

Objectives

A growing number of studies have reported that genes involved in the repair of DNA double-strand breaks might be cancer-susceptibility genes. The x-ray cross-complementing group 4 gene ( XRCC4) encodes a protein that functions in the repair of DNA double-strand breaks, and this meta-analysis aimed to investigate the relationship between the XRCC4 rs1805377 polymorphism and cancer occurrence.

Methods

We retrieved case–control studies that met the inclusion criteria from PubMed, Web of Science, Embase, and China National Knowledge Infrastructure databases. Associations between rs1805377 and cancer risk were evaluated by odds ratios (ORs) using a random effects model and 95% confidence intervals (CIs) as well as sensitivity and subgroup analyses.

Results

After inclusion criteria were met, the meta-analysis involved 24 studies that included 9,633 cancer patients and 10,544 healthy controls. No significant association was found between rs1805377 and the risk of cancer (pooled OR = 1.107; 95% CI = 0.955–1.284) in the dominant genetic model. Similarly, no significant association was observed in the subgroup analysis.

Conclusions

Through this meta-analysis, we found no association between the rs1805377 polymorphism and cancer occurrence. This may provide useful information for relevant future studies into the etiology of cancer.

Association of germline genetic variants with TMPRSS2-ERG fusion status in prostate cancer

Introduction: Oncogenic activation of ERG resulting from TMPRSS2-ERG gene fusion is a key molecular genetic alteration in prostate cancer (CaP). The frequency of ERG fusion is variable by race; however, there are limited data available on germline polymorphisms associating with ERG fusion status. The goal of this study is to identify the inherited risk variants associating with ERG status of CaP.

Materials and Methods: SNP genotyping was performed on the Illumina platform using Infinium Oncoarray SNP chip on blood derived genomic DNA samples from 400 patients treated by radical prostatectomy at a single military institution. ERG status was determined in whole mounted prostate specimens by immuno-histochemistry (IHC) for ERG protein expression. Data analysis approaches included association analyses based on EMMAX and imputation by IMPUTE2. Imputed SNPs were validated by ddPCR.

Results: SNP genotyping analysis using imputation identified rs34349373 (p 4.68 × 10^-8) and rs2055272 (p 5.62 × 10^-8) in TBC1D22B to be significantly associated with ERG fusion status in index tumor and non-index tumor foci. Imputed SNP rs2055272 was further experimentally validated by ddPCR with 98.04% (100/102) concordance. Initial discovery analysis based on SNPs on Oncoarray SNP chip, showed significant (p 10^-5) association for SNPs (rs6698333, rs1889877, rs3798999, rs10215144, rs3818136, rs9380660 and rs1792695) with ERG fusion status. The study also replicated two previously known ERG fusion associated SNPs (rs11704416 in chromsome 22; rs16901979 in chromosome 8).

Conclusions: This study identified SNPs associated with ERG status of CaP.

Impact: The findings may contribute towards defining the underlying genetics of ERG positive and ERG negative CaP patients.

Establishment of cohesion 1 homolog 2 facilitates cell aggressive behaviors and induces poor prognosis in renal cell carcinoma

Background and aims

Establishment of cohesion 1 homolog 2 (ESCO2) has been identified as an essential factor for cohesion in cell cycle in human multiple cancers. Nonetheless, its functional implication on prognosis and cellular behaviors of renal cell carcinoma (RCC) is rarely elucidated. We performed this study to detect the effects of ESCO2 in RCC progression.

Methods

We accessed The Cancer Genome Atlas (TCGA) database to evaluate the ESCO2 expression levels in tumor tissues, including 32 normal tissues and 289 tumor tissues. Quantitative real‐time PCR and Western blot were implemented for expression detection. After ESCO2 knockdown using siRNAs interference, functional experiments were conducted to explore the role of ESCO2, such as cell proliferation analysis and colony formation assay. Transwell assays for migration and invasion was also performed.

Results

In this study, ESCO2 was significantly increased in RCC tissues and cell lines. The RCC patients with high expression of ESCO2 were susceptible to unfavorable prognosis, and its expression has a marked association with clinical features containing age, gender, pathologic stage, and so on. Furthermore, knockdown of ESCO2 inhibited cell growth, invasion, and migration. Mechanistically, phosphorylation protein kinase B (AKT) and mammalian target of rapamycin (mTOR), proliferating cell nuclear antigen (PCNA), and p53 were all down‐regulated due to the ESCO2 inhibition.

Conclusions

Therefore, our results raised the possibility that ESCO2 may act as a promising option for tumor therapeutic interference by exhibiting enhanced selectivity over conventional chemotherapy.

Polymerase iota - an odd sibling among Y family polymerases

It has been two decades since the discovery of the most mutagenic human DNA polymerase, polymerase iota (Polι). Since then, the biochemical activity of this translesion synthesis (TLS) enzyme has been extensively explored, mostly through in vitro experiments, with some insight into its cellular activity. Polι is one of four members of the Y-family of polymerases, which are the best characterized DNA damage-tolerant polymerases involved in TLS. Polι shares some common Y-family features, including low catalytic efficiency and processivity, high infidelity, the ability to bypass some DNA lesions, and a deficiency in 3'→5' exonucleolytic proofreading. However, Polι exhibits numerous properties unique among the Y-family enzymes. Polι has an unusual catalytic pocket structure and prefers Hoogsteen over Watson-Crick pairing, and its replication fidelity strongly depends on the template; further, it prefers Mn²⁺ ions rather than Mg²⁺ as catalytic activators. In addition to its polymerase activity, Polι possesses also 5'-deoxyribose phosphate (dRP) lyase activity, and its ability to participate in base excision repair has been shown. As a highly error-prone polymerase, its regulation is crucial and mostly involves posttranslational modifications and protein-protein interactions. The upregulation and downregulation of Polι are correlated with different types of cancer and suggestions regarding the possible function of this polymerase have emerged from studies of various cancer lines. Nonetheless, after twenty years of research, the biological function of Polι  certainly remains unresolved.

The polymorphisms (rs3213801 and rs5744533) of DNA polymerase kappa gene are not related with glioma risk and prognosis: A case-control study

DNA polymerase kappa (POLK), one of the specialized Y family DNA polymerases, functions in translesion synthesis and is suggested to be related with cancers. Single nucleotide polymorphisms (SNPs) in specialized DNA polymerases have been demonstrated to be associated with cancer risk. To evaluate the association of two common POLK variants (rs3213801 C>T and rs5744533 C>T) with glioma, we conducted a case‐control study and genotyped these two POLK variants in 605 patients and 1300 healthy controls. The association analysis revealed no significant correlations were observed between these two POLK SNPs and glioma risk. However, the POLK rs3213801 CT genotype was found to be higher in older glioma patients (≥40) than in younger patients (P = .026). Compared with patients harboring the CC genotype, the frequencies of POLK rs5744533 CT and CT+TT genotypes were increased in patients with lower World Health Organization (WHO) grade glioma (P = .028, 0.044, respectively). According to Kaplan‐Meier analysis and log‐rank tests, POLK SNPs were not correlated with either the overall survival or progression‐free survival. Nevertheless, multivariate analysis revealed that the age (≥40) could increase the risk of death in glioma patients (P < .05), while gross‐total resection and temozolomide treatment were found to play protective roles in glioma prognosis (P < .001, respectively). Overall, our results indicated that POLK variants rs3213801 and rs5744533 are not associated with glioma risk and prognosis. However, these polymorphisms are likely to be associated with certain glioma characteristics, such as age and WHO grade. The age, surgery types, and chemotherapy could be independent prognostic factors in glioma. More studies are required to confirm our findings.

Post-replication repair: Rad5/HLTF regulation, activity on undamaged templates, and relationship to cancer

The eukaryotic post-replication repair (PRR) pathway allows completion of DNA replication when replication forks encounter lesions on the DNA template and are mediated by post-translational ubiquitination of the DNA sliding clamp proliferating cell nuclear antigen (PCNA). Monoubiquitinated PCNA recruits translesion synthesis (TLS) polymerases to replicate past DNA lesions in an error-prone manner while addition of K63-linked polyubiquitin chains signals for error-free template switching to the sister chromatid. Central to both branches is the E3 ubiquitin ligase and DNA helicase Rad5/helicase-like transcription factor (HLTF). Mutations in PRR pathway components lead to genomic rearrangements, cancer predisposition, and cancer progression. Recent studies have challenged the notion that the PRR pathway is involved only in DNA lesion tolerance and have shed new light on its roles in cancer progression. Molecular details of Rad5/HLTF recruitment and function at replication forks have emerged. Mounting evidence indicates that PRR is required during lesion-less replication stress, leading to TLS polymerase activity on undamaged templates. Analysis of PRR mutation status in human cancers and PRR function in cancer models indicates that down regulation of PRR activity is a viable strategy to inhibit cancer cell growth and reduce chemoresistance. Here, we review these findings, discuss how they change our views of current PRR models, and look forward to targeting the PRR pathway in the clinic.

The correlation of ESCO1 expression with a prognosis of prostate cancer and anti-tumor effect of ESCO1 silencing

Background

Recently, it has been reported that establishment of sister chromatid cohesion N-acetyltransferase 1 (ESCO1) is involved in tumorigenesis. However, its role in prostate cancer remains unclear. In the present study, the association between ESCO1 expression and the prognosis of prostate cancer was investigated, and the potential molecular mechanisms underlying its actions in tumor progression were also examined.

Methods

Immunohistochemical analysis was performed to detect the expression of ESCO1 in benign prostatic hyperplasia (BPH), human prostate cancer, and metastasis tissue samples, and the association between the establishment of ESCO1 expression and the prognosis of prostate cancer was investigated. The effect of ESCO1 expression on the viability, migration, and invasion of prostate cancer cells in vitro was analyzed, along with the effect of ESCO1 silencing on the growth of prostate tumors in vivo.

Results

The results demonstrated an increase in the expression of ESCO1 in prostate cancer tissue when compared with BPH, and it was significantly associated with tumor malignancy and poor patient survival. Additionally, knockdown of ESCO1 significantly inhibited the viability and migration of prostate cancer cell. Furthermore, we found that knockdown of ESCO1 significantly inhibited tumor growth in vivo. Pathway analysis identified that the silencing of ESCO1 significantly decreased the phosphorylation levels of protein kinase B.

Conclusions

The results of the present study indicate that ESCO1 plays a vital role in the progression of human prostate cancer; furthermore, ESCO1 may potentially serve as a prognostic marker and a novel therapeutic target for this disease.

Mechanisms of DNA Damage Tolerance: Post-Translational Regulation of PCNA

DNA damage is a constant source of stress challenging genomic integrity. To ensure faithful duplication of our genomes, mechanisms have evolved to deal with damage encountered during replication. One such mechanism is referred to as DNA damage tolerance (DDT). DDT allows for replication to continue in the presence of a DNA lesion by promoting damage bypass. Two major DDT pathways exist: error-prone translesion synthesis (TLS) and error-free template switching (TS). TLS recruits low-fidelity DNA polymerases to directly replicate across the damaged template, whereas TS uses the nascent sister chromatid as a template for bypass. Both pathways must be tightly controlled to prevent the accumulation of mutations that can occur from the dysregulation of DDT proteins. A key regulator of error-prone versus error-free DDT is the replication clamp, proliferating cell nuclear antigen (PCNA). Post-translational modifications (PTMs) of PCNA, mainly by ubiquitin and SUMO (small ubiquitin-like modifier), play a critical role in DDT. In this review, we will discuss the different types of PTMs of PCNA and how they regulate DDT in response to replication stress. We will also cover the roles of PCNA PTMs in lagging strand synthesis, meiotic recombination, as well as somatic hypermutation and class switch recombination.

ESCO2 inhibits tumor metastasis via transcriptionally repressing MMP2 in colorectal cancer

Background

Establishment of cohesion 1 homolog 2 (ESCO2) plays important roles in the regulation of cohesion and genomic stability and has been implicated in human cancers. Yet, its clinical significance and biological function in colorectal cancer (CRC) are unknown.

Methods

The expression of ESCO2 was examined by quantitative real-time PCR, Western blot, and immunohistochemistry. The role of ESCO2 in the tumor metastasis of CRC and the related mechanisms were investigated using in vitro and in vivo models.

Results

In this study, we show that low expression of ESCO2 in CRC was closely correlated with lymphatic and distant metastasis. Patients with low ESCO2 expression experienced shorter overall survival and disease-free survival in two independent cohorts containing a total of 587 CRC cases. ESCO2 overexpression suppressed, whereas ESCO2 knockdown promoted cell migration in vitro and tumor metastasis in vivo via modulation of epithelial–mesenchymal transition (EMT) process. Mechanistically, ESCO2 inhibited the transcriptional activity of MMP2 promoter to downregulate its expression. Reexpression of MMP2 partially attenuated the ESCO2-mediated malignant phenotypes.

Conclusion

Collectively, our data suggest that ESCO2 serves as a potential prognostic factor and exerts antimetastatic activity in CRC.

ESCO1/2's roles in chromosome structure and interphase chromatin organization

In this study, Kawasumi et al. researched how ESCO1/2 acetyltransferases mediating SMC3 acetylation and sister chromatid cohesion (SCC) interact and contribute to chromosome structure and proliferation. Using chicken DT40 cell lines with mutations in ESCO1/2, SMC3 acetylation, and the cohesin remover WAPL, they show that cohesion establishment by vertebrate ESCO1/2 is linked to interphase chromatin architecture formation.

ESCO1/2 acetyltransferases mediating SMC3 acetylation and sister chromatid cohesion (SCC) are differentially required for genome integrity and development. Here we established chicken DT40 cell lines with mutations in ESCO1/2, SMC3 acetylation, and the cohesin remover WAPL. Both ESCO1 and ESCO2 promoted SCC, while ESCO2 was additionally and specifically required for proliferation and centromere integrity. ESCO1 overexpression fully suppressed the slow proliferation and centromeric separation phenotypes of esco2 cells but only partly suppressed its chromosome arm SCC defects. Concomitant inactivation of ESCO1 and ESCO2 caused lethality owing to compromised mitotic chromosome segregation. Neither wapl nor acetyl-mimicking smc3-QQ mutations rescued esco1 esco2 lethality. Notably, esco1 esco2 wapl conditional mutants showed very severe proliferation defects associated with catastrophic mitoses and also abnormal interphase chromatin organization patterns. The results indicate that cohesion establishment by vertebrate ESCO1/2 is linked to interphase chromatin architecture formation, a newly identified function of cohesin acetyltransferases that is both fundamentally and medically relevant.

Association Between Twelve Polymorphisms in Five X-ray Repair Cross-complementing Genes and the Risk of Urological Neoplasms: A Systematic Review and Meta-Analysis

Polymorphisms in X-ray repair cross-complementing (XRCC) genes have been implicated in altering the risk of various urological cancers. However, the results of reported studies are controversial. To ascertain whether polymorphisms in XRCC genes are associated with the risk of urological neoplasms, we conducted present updated meta-analysis and systematic review. Summary odds ratios (ORs) and corresponding 95% confidence intervals (CIs) were used to estimate the association. Finally, 54 publications comprising 129 case-control studies for twelve polymorphisms in five XRCC genes were enrolled. We identified that XRCC1-rs25489 polymorphism was associated with an increased risk of urological neoplasms in heterozygote and dominant models. Moreover, in the subgroup analysis by cancer type, we found that XRCC1-rs25489 polymorphism was associated with an increased risk of bladder cancer (BC) in heterozygote model. Although overall analyses suggested a null result for XRCC1-rs25487 polymorphism, in the stratified analysis by ethnicity, an increased risk of urological neoplasms for Asians in allelic and homozygote models was identified. While for other polymorphisms in XRCC genes, no significant association was uncovered. To sum up, our results indicated that XRCC1-rs25489 polymorphism is a risk factor for urological neoplasms, particularly for BC. Further studies with large sample size are needed to validate these findings.

Prostate cancer risk regions at 8q24 and 17q24 are differentially associated with somatic TMPRSS2:ERG fusion status

Molecular and epidemiological differences have been described between TMPRSS2:ERG fusion-positive and fusion-negative prostate cancer (PrCa). Assuming two molecularly distinct subtypes, we have examined 27 common PrCa risk variants, previously identified in genome-wide association studies, for subtype specific associations in a total of 1221 TMPRSS2:ERG phenotyped PrCa cases. In meta-analyses of a discovery set of 552 cases with TMPRSS2:ERG data and 7650 unaffected men from five centers we have found support for the hypothesis that several common risk variants are associated with one particular subtype rather than with PrCa in general. Risk variants were analyzed in case-case comparisons (296 TMPRSS2:ERG fusion-positive versus 256 fusion-negative cases) and an independent set of 669 cases with TMPRSS2:ERG data was established to replicate the top five candidates. Significant differences (P < 0.00185) between the two subtypes were observed for rs16901979 (8q24) and rs1859962 (17q24), which were enriched in TMPRSS2:ERG fusion-negative (OR = 0.53, P = 0.0007) and TMPRSS2:ERG fusion-positive PrCa (OR = 1.30, P = 0.0016), respectively. Expression quantitative trait locus analysis was performed to investigate mechanistic links between risk variants, fusion status and target gene mRNA levels. For rs1859962 at 17q24, genotype dependent expression was observed for the candidate target gene SOX9 in TMPRSS2:ERG fusion-positive PrCa, which was not evident in TMPRSS2:ERG negative tumors. The present study established evidence for the first two common PrCa risk variants differentially associated with TMPRSS2:ERG fusion status. TMPRSS2:ERG phenotyping of larger studies is required to determine comprehensive sets of variants with subtype-specific roles in PrCa.

Gene and pathway level analyses of germline DNA-repair gene variants and prostate cancer susceptibility using the iCOGS-genotyping array

BACKGROUND

Germline mutations within DNA-repair genes are implicated in susceptibility to multiple forms of cancer. For prostate cancer (PrCa), rare mutations in BRCA2 and BRCA1 give rise to moderately elevated risk, whereas two of B100 common, low-penetrance PrCa susceptibility variants identified so far by genome-wide association studies implicate RAD51B and RAD23B.

METHODS

Genotype data from the iCOGS array were imputed to the 1000 genomes phase 3 reference panel for 21 780 PrCa cases and 21 727 controls from the Prostate Cancer Association Group to Investigate Cancer Associated Alterations in the Genome (PRACTICAL) consortium. We subsequently performed single variant, gene and pathway-level analyses using 81 303 SNPs within 20 Kb of a panel of 179 DNA-repair genes.

RESULTS

Single SNP analyses identified only the previously reported association with RAD51B. Gene-level analyses using the SKAT-C test from the SNP-set (Sequence) Kernel Association Test (SKAT) identified a significant association with PrCa for MSH5. Pathway-level analyses suggested a possible role for the translesion synthesis pathway in PrCa risk and Homologous recombination/Fanconi Anaemia pathway for PrCa aggressiveness, even though after adjustment for multiple testing these did not remain significant.

CONCLUSIONS

MSH5 is a novel candidate gene warranting additional follow-up as a prospective PrCa-risk locus. MSH5 has previously been reported as a pleiotropic susceptibility locus for lung, colorectal and serous ovarian cancers.

Association of Prostate Cancer Risk Variants with TMPRSS2:ERG Status: Evidence for Distinct Molecular Subtypes

BACKGROUND

Numerous genetic variants have been confirmed as prostate cancer risk factors. These variants may confer susceptibility to the development of specific molecular alterations during tumor initiation and progression. The TMPRSS2:ERG gene fusion occurs in roughly 50% of prostate cancers. Genetic risk variants may influence the development of this fusion. We sought to determine whether prostate cancer risk variants are differentially associated with TMPRSS2:ERG fusion-positive and negative cancer.

METHODS

In the Health Professionals Follow-up Study and Physicians' Health Study Tumor Cohort, we evaluated the associations of 39 prostate cancer risk SNPs with TMPRSS2:ERG fusion status, measured by ERG protein expression. Logistic regression was performed to generate OR and 95% confidence intervals. The primary outcome was ERG(+) (n = 227) versus ERG(-) (n = 260) prostate cancer. A secondary outcome was ERG(+) or ERG(-) cancer versus controls without cancer.

RESULTS

Six of 39 SNPs were significantly associated (P < 0.05) with ERG(+) versus ERG(-) disease. Three SNPs were exclusively associated with the risk of ERG(+), one with risk of ERG(-), and two with associations trending in opposite directions for ERG(+) and ERG(-) Only two significant SNPs would be expected by chance.

CONCLUSIONS

Prostate cancer genetic risk variants are differentially associated with the development of ERG(+) and ERG(-) prostate cancer.

IMPACT

Our findings suggest the molecular process of prostate carcinogenesis may be distinct for men with different underlying genetic predisposition. When examining risk factors for prostate cancer, the integration of molecular subtypes may enhance understanding of the etiology of this disease. Cancer Epidemiol Biomarkers Prev; 25(5); 745-9. ©2016 AACR.

Increased expression of ESCO1 is correlated with poor patient survival and its role in human bladder cancer

There is increasing evidence suggesting that establishment of sister chromatid cohesion N-acetyltransferase 1 (ESCO1) was involved in tumorigenesis. However, its role in bladder cancer remains unclear. In this study, we aimed to study the clinical correlation and biological significance of ESCO1 in bladder cancer. Our results showed that ESCO1 was significantly over-expressed in bladder cancer tissues compared with that in adjacent normal tissues. And, increased ESCO1 expression was significantly associated with higher grade (P < 0.001), higher tumor stage (P = 0.014), and multifocality (P = 0.042). Kaplan-Meier analysis and Cox proportional hazards model were performed to determine the prognostic significance of ESCO1, and the results showed that ESCO1 is a useful prognostic marker for bladder cancer patients. Moreover, we found that ESCO1 knockdown inhibited the growth, migration, and invasion of bladder cancer cells. In conclusion, our findings indicated that ESCO1 may play an important role in human bladder cancer, and ESCO1 might serve as a novel target and prognosis factor for human bladder cancer.

Two susceptibility loci identified for prostate cancer aggressiveness

Most men diagnosed with prostate cancer will experience indolent disease; hence, discovering genetic variants that distinguish aggressive from nonaggressive prostate cancer is of critical clinical importance for disease prevention and treatment. In a multistage, case-only genome-wide association study of 12,518 prostate cancer cases, we identify two loci associated with Gleason score, a pathological measure of disease aggressiveness: rs35148638 at 5q14.3 (RASA1, P=6.49 × 10(-9)) and rs78943174 at 3q26.31 (NAALADL2, P=4.18 × 10(-8)). In a stratified case-control analysis, the SNP at 5q14.3 appears specific for aggressive prostate cancer (P=8.85 × 10(-5)) with no association for nonaggressive prostate cancer compared with controls (P=0.57). The proximity of these loci to genes involved in vascular disease suggests potential biological mechanisms worthy of further investigation.

XomAnnotate: Analysis of Heterogeneous and Complex Exome- A Step towards Translational Medicine

In translational cancer medicine, implicated pathways and the relevant master genes are of focus. Exome's specificity, processing-time, and cost advantage makes it a compelling tool for this purpose. However, analysis of exome lacks reliable combinatory analysis tools and techniques. In this paper we present XomAnnotate – a meta- and functional-analysis software for exome. We compared UnifiedGenotyper, Freebayes, Delly, and Lumpy algorithms that were designed for whole-genome and combined their strengths in XomAnnotate for exome data through meta-analysis to identify comprehensive mutation profile (SNPs/SNVs, short inserts/deletes, and SVs) of patients. The mutation profile is annotated followed by functional analysis through pathway enrichment and network analysis to identify most critical genes and pathways implicated in the disease genesis. The efficacy of the software is verified through MDS and clustering and tested with available 11 familial non-BRCA1/BRCA2 breast cancer exome data. The results showed that the most significantly affected pathways across all samples are cell communication and antigen processing and presentation. ESCO1, HYAL1, RAF1 and PRKCA emerged as the key genes. Network analysis further showed the purine and propanotate metabolism pathways along with RAF1 and PRKCA genes to be master regulators in these patients. Therefore, XomAnnotate is able to use exome data to identify entire mutation landscape, pathways, and the master genes accurately with wide concordance from earlier microarray and whole-genome studies -- making it a suitable biomedical software for using exome in next-generation translational medicine.

ERG induces a mesenchymal-like state associated with chemoresistance in leukemia cells

Overexpression of the oncogene ERG (ETS-related gene) is an adverse prognostic factor in acute myeloid and T-cell lymphoblastic leukemia (AML and T-ALL). We hypothesize that ERG overexpression is associated with primary drug resistance thereby influencing the outcome in leukemia. We previously reported a cell-line based model of ERG overexpression which induced a potentially chemo-resistant spindle shape cell type. Herein, we report a specific transcriptional gene signature for the observed spindle shaped morphology. Genes significantly over-expressed after ERG induction strongly resembled adhesive mesenchymal-like genes that included integrins (ITGA10, ITGB5, ITGB3, ITGA2B), CD44, and CD24. Interestingly, the mesenchymal-like signature was accompanied by the repression of DNA chromatin remodeling and DNA repair genes, such as CHEK1, EZH2, SUZ12, and DNMT3a. The ERG-induced mesenchymal-like signature positively correlated with TMPRSS2-ERG prostate tissues and invasive breast cancer mRNA expression datasets reflecting a general ERG-driven pattern of malignancy. Furthermore, inhibitors modulating ERG druggable pathways WNT, PKC, and AKT, and chemotherapeutic agent cytarabine revealed ERG-induced drug resistance. In particular, PKC412 treatment enhanced proliferative rates and promoted spindle shape formation in ERG-induced cells. Nilotinib and dasatinib were effective at abolishing ERG-induced cells. Moreover, ERG overexpression also led to an increase in double strand breaks. This report provides mechanistic clues into ERG-driven drug resistance in the poor prognostic group of high ERG expressers, provides insight to improved drug targeted therapies, and provides novel markers for a mesenchymal-like state in acute leukemia.

TMPRSS2-ERG gene fusion in prostate cancer

BACKGROUND

The TMPRSS2-ERG gene fusion is one of the most widely spread chromosomal rearrangements in carcinomas. Since its discovery, a number of studies have examined its diagnostic, prognostic and therapeutic implications for prostate cancer where suitable biomarkers are still lacking. The publication data are inconsistent. The aim of this review was to critically evaluate the current clinical impact of this gene fusion.

METHODS

The PubMed online database was used to search relevant reviews and original articles.

RESULTS

Although the TMPRSS2-ERG gene fusion appears to be a suitable diagnostic biomarker, the prognostic implications of this gene fusion are still unclear. Several new strategies for therapeutically targeting ETS fusions and their modulators have been identified and are currently being investigated.

CONCLUSION

Due to the heterogeneity of prostate cancer, the combination of several biomarkers is necessary to accurately assess the presence of prostate cancer, predict its potential clinical outcome and decide on appropriate therapy (e.g. PARP inhibitors).

Biochemical analysis of six genetic variants of error-prone human DNA polymerase ι involved in translesion DNA synthesis

DNA polymerase (pol) ι is the most error-prone among the Y-family polymerases that participate in translesion synthesis (TLS). Pol ι can bypass various DNA lesions, e.g., N²-ethyl(Et)G, O⁶-methyl(Me)G, 8-oxo-7,8-dihydroguanine (8-oxoG), and an abasic site, though frequently with low fidelity. We assessed the biochemical effects of six reported genetic variations of human pol ι on its TLS properties, using the recombinant pol ι (residues 1–445) proteins and DNA templates containing a G, N²-EtG, O⁶-MeG, 8-oxoG, or abasic site. The Δ1–25 variant, which is the N-terminal truncation of 25 residues resulting from an initiation codon variant (c.3G > A) and also is the formerly misassigned wild-type, exhibited considerably higher polymerase activity than wild-type with Mg²⁺ (but not with Mn²⁺), coinciding with its steady-state kinetic data showing a ∼10-fold increase in k_cat/K_m for nucleotide incorporation opposite templates (only with Mg²⁺). The R96G variant, which lacks a R96 residue known to interact with the incoming nucleotide, lost much of its polymerase activity, consistent with the kinetic data displaying 5- to 72-fold decreases in k_cat/K_m for nucleotide incorporation opposite templates either with Mg²⁺ or Mn²⁺, except for that opposite N²-EtG with Mn²⁺ (showing a 9-fold increase for dCTP incorporation). The Δ1–25 variant bound DNA 20- to 29-fold more tightly than wild-type (with Mg²⁺), but the R96G variant bound DNA 2-fold less tightly than wild-type. The DNA-binding affinity of wild-type, but not of the Δ1–25 variant, was ∼7-fold stronger with 0.15 mM Mn²⁺ than with Mg²⁺. The results indicate that the R96G variation severely impairs most of the Mg²⁺- and Mn²⁺-dependent TLS abilities of pol ι, whereas the Δ1–25 variation selectively and substantially enhances the Mg²⁺-dependent TLS capability of pol ι, emphasizing the potential translational importance of these pol ι genetic variations, e.g., individual differences in TLS, mutation, and cancer susceptibility to genotoxic carcinogens.

Translesion DNA polymerases and cancer

DNA repair has been regarded as an important barrier to carcinogenesis. The newly discovered field of translesion synthesis (TLS) has made it apparent that mammalian cells need distinct polymerases to efficiently and accurately bypass DNA lesions. Perturbation of TLS polymerase activity by mutation, loss of expression, etc. is expected to result in the accumulation of mutations in cells exposed to specific carcinogens. Furthermore, several TLS polymerases can modulate cellular sensitivity to chemotherapeutic agents. TLS genes and TLS gene variations may thus be attractive pharmacologic and/or pharmacogenetic targets. We review herein current data with regards to the potential contribution of the primary TLS polymerase genes to cancer, their interaction with pharmacologic agents, and identify areas of interest for further research.

Role of rare variants in undetermined multiple adenomatous polyposis and early-onset colorectal cancer

Some 15-20% of multiple adenomatous polyposis have no genetic explanation and 20-30% of colorectal cancer (CRC) cases are thought to be due to inherited multifactorial causes. Accumulation of deleterious effects of low-frequency dominant and independently acting variants may be a partial explanation for such patients. The aim of this study was to type a selection of rare and low-frequency variants (<5%) to elucidate their role in CRC susceptibility. A total of 1181 subjects were included (866 controls; 315 cases). Cases comprised UK (n=184) and French (n=131) patients with MAP (n=187) or early-onset CRC (n=128). Seventy variants in 17 genes were examined in cases and controls. The effect of the variant effect on protein function was investigated in silico. Out of the 70 variants typed, 36 (51%) were tested for association. Twenty-one variants were rare (minor allele frequency (MAF) <1%). Four rare variants were found to have a significantly higher MAF in cases (EXO1-12, MLH1-1, CTNNB1-1 and BRCA2-37, P<0.05) than in controls. Pooling all rare variants with a MAF <0.5% showed an excess risk in cases (odds ratio=3.2; 95% confidence interval=1.1-9.5; P=0.04). Rare variants are important risk factors in CRC and, as such, should be systematically assayed alongside common variation in the search for the genetic basis of complex diseases.

Prostate cancer risk is not altered by TP53AIP1 germline mutations in a German case-control series

Prostate cancer susceptibility has previously been associated with truncating germline variants in the gene TP53AIP1 (tumor protein p53 regulated apoptosis inducing protein 1). For two apparently recurrent mutations (p.Q22fs and p.S32X) a remarkable OR of 5.1 was reported for prostate cancer risk. Since these findings have not been validated so far, we genotyped p.Q22fs and p.S32X in two German series with a total of 1,207 prostate cancer cases and 1,495 controls. The truncating variants were not significantly associated with prostate cancer in none of the two cohorts, nor in the combined analysis [odds ratio (OR) = 1.16; 95% confidence interval (CI 95%) = 0.62–2.15; p = 0.66]. Carriers showed no significant differences in family history of prostate cancer, age at diagnosis, Gleason score or PSA at diagnosis when compared to non-carrier prostate cancer cases. The large sample size of the combined cohort rejects a high-risk effect greater than 2.2 and indicates a limited role of TP53AIP1 in prostate cancer predisposition.

Y-family DNA polymerases and their role in tolerance of cellular DNA damage

The past 15 years have seen an explosion in our understanding of how cells replicate damaged DNA and how this can lead to mutagenesis. The Y-family DNA polymerases lie at the heart of this process, which is commonly known as translesion synthesis. This family of polymerases has unique features that enable them to synthesize DNA past damaged bases. However, as they exhibit low fidelity when copying undamaged DNA, it is essential that they are only called into play when they are absolutely required. Several layers of regulation ensure that this is achieved.

DNA methylation changes in prostate cancer

Epigenetic alterations contribute significantly to the development and progression of prostate cancer, the most prevalent malignant tumor in males of Western industrialized countries. Here, we review recent research on DNA methylation alterations in this cancer type. Hypermethylation of several genes including GSTP1 is well known to occur in a consistent and apparently coordinate fashion during the transition from intraepithelial neoplasia to frank carcinoma. These hypermethylation events have shown promise as biomarkers for detection of prostate carcinoma. Many other individual genes have been shown to undergo hypermethylation, which is typically associated with diminished expression. These investigations indicate additional candidates for biomarkers; in particular, hypermethylation events associated with progression can be employed to identify more aggressive cases. In addition, some of genes silenced by aberrant methylation in prostate have been shown to exhibit properties of tumor suppressors, revealing insights into mechanisms of carcinogenesis. Whereas most studies in the past have used candidate gene approaches, new techniques allowing genome-wide screening for altered methylation are increasingly employed in prostate cancer research and have already yielded encouraging results.

TMPRSS2/ERG fusion gene expression alters chemo- and radio-responsiveness in cell culture models of androgen independent prostate cancer

PURPOSE/OBJECTIVES

The androgen regulated transmembrane serine protease (TMPRSS2) and ETS transcription factor (ERG) gene fusion is a strong prognostic factor for disease recurrence following prostatectomy. Expression of TMPRSS2/ETS-related gene (ERG) fusion gene transcripts is linked with tumor proliferation, invasion, and an aggressive phenotype. The aim of this study was to define the effect of TMPRSS2/ERG fusion gene expression on chemo- and radiosensitivity in prostate tumor cell lines.

MATERIALS/METHODS

Clonogenic survival of PC3 and DU145 cells stably expressing TMPRSS2/ERG Types III and VI fusion genes was measured after X-irradiation (0-8 Gy) and Paclitaxel. Cell cycle changes and DNA double-strand break induction and repair were assessed. Differential gene expression was measured by microarray analysis. ERG signaling pathway interactions were studied using Ariadne Pathway Studio.

RESULTS

Expression of the TMPRSS2/ERG fusions in PC3 cells increased radiation sensitivity and decreased paclitaxel sensitivity. Increased radiosensitivity was associated with persistent DNA breaks 24 hr post-irradiation, down-regulation of genes involved in DNA repair and mitosis and up-regulation of ETV, an ETS transcription factor. However, DU145 Types III and VI demonstrated a different sensitivity phenotype and gene expression changes. Pathway analysis of ERG signaling further illustrated the variation between the PC3 and DU145 cell lines containing TMPRSS2/ERG fusions.

CONCLUSIONS

The effect of TMPRSS2/ERG gene fusions had differing effects on radiosensitivity and chemosensitivity depending on cell line and fusion type. Further work is needed with clinical samples to establish whether TMPRSS2/ERG gene fusions affect radio- and chemosensitivity in vivo.

Germline BRCA mutation does not prevent response to taxane-based therapy for the treatment of castration-resistant prostate cancer

OBJECTIVE

• To investigate the relationship between BRCA mutation status and response to taxane-based chemotherapy, since BRCA mutation carriers with prostate cancer appear to have worse survival than non-carriers and docetaxel improves survival in patients with castration-resistant prostate cancer.

PATIENTS AND METHODS

• We determined BRCA mutation prevalence in 158 Ashkenazi Jewish (AJ) men with castration-resistant prostate cancer. Clinical data were collected as part of an institutional prostate cancer research database and through additional medical record review. • Clinical records and DNA samples were linked through a unique identifier, anonymizing the samples before genetic testing for the AJ BRCA1/2 founder mutations. • Response to taxane-based therapy was defined by the prostate-specific antigen nadir within 12 weeks of therapy.

RESULTS

• In all, 88 men received taxane-based treatment, seven of whom were BRCA carriers (three BRCA1, four BRCA2; 8%). Initial response to taxane was available for all seven BRCA carriers and for 69 non-carriers. • Overall, 71% (54/76) of patients responded to treatment, with no significant difference between carriers (57%) and non-carriers (72%) (absolute difference 15%; 95% confidence interval -23% to 53%; P= 0.4). • Among patients with an initial response, the median change in prostate-specific antigen was similar for BRCA carriers (-63%, interquartile range -71% to -57%) and non-carriers (-60%, interquartile range -78% to -35%) (P= 0.6). • At last follow-up, all seven BRCA carriers and 49 non-carriers had died from prostate cancer. One BRCA2 carrier treated with docetaxel plus platinum survived 37 months.

CONCLUSION

• In this small, hypothesis-generating study approximately half of BRCA carriers had a prostate-specific antigen response to taxane-based chemotherapy, suggesting that it is an active therapy in these individuals.

Cdk1-dependent destruction of Eco1 prevents cohesion establishment after S phase

Accurate genome segregation depends on cohesion mechanisms that link duplicated sister chromatids, thereby allowing their tension-dependent biorientation in metaphase. In Saccharomyces cerevisiae, cohesion is established during DNA replication when Eco1 acetylates the cohesin subunit Smc3. Cohesion establishment is restricted to S phase of the cell cycle, but the molecular basis of this regulation is unknown. Here, we show that Eco1 is negatively regulated by the protein kinase Cdk1. Phosphorylation of Eco1 after S phase targets it to SCF(Cdc4) for ubiquitination and subsequent degradation. A nonphosphorylatable mutant of Eco1 establishes cohesion after DNA replication, suggesting that Cdk1-dependent phosphorylation of Eco1 is a key factor limiting establishment to S phase. We also show that deregulation of Eco1 results in chromosome separation defects in anaphase. We conclude that this regulatory mechanism helps optimize the level of sister chromatid cohesion, ensuring a robust and efficient anaphase.

Therapeutic Effect of Epigallocatechin-3-gallate (EGCG) and Silibinin on ATM Dynamics in Prostate Cancer Cell Line LNCaP

Background

Epigallocatechin-3-gallate (EGCG) is a major ingredient of green tea (GT) and silibinin (SB), the active component of Silymarin presumably hold a potential to prevent pathogenomics. Prostate cancer exacerbation is triggered by fusion transcripts formed because of genomic instability induced by juxtapositioning of two genes. This chimeric transcript is implicated in androgen dependent and independent prostate cancer. Tremendous work is done on the characterization of the mediators involved in the disease refractoriness, yet no study has addressed clinical management of these prostate fusion transcripts impressively.

Methods

An abolished ATM dynamics challenges integrity of DNA. In agreement with this assumption, ATM and DNA-PK were impaired in LNCaP cell line to confirm a tight interaction of these mediators with the expression profile of TMPRSS2-ERG. Abolished ATM enhanced the expression of the fusion transcript. Similarly blunting of DNA-PK downregulated the expression of the fusion transcript giving a notion that DNA-PK is involved in the chromosomal translocation. LNCaP cell lines were analyzed for the effect of EGCG and SB on the expression profile of TMPRSS2-ERG.

Results

In this particular unprecedented study, treatment of the LNCaP cell line with EGCG and Silibilin recapitulated ATM expression and activity and downregulated the fusion transcript appearance.

Conclusions

These results underscore the therapeutic effect of EGCG and SB in mitigating the exacerbation of the disease with reference to the fusion transcripts.

Translesion synthesis polymerases in the prevention and promotion of carcinogenesis

A critical step in the transformation of cells to the malignant state of cancer is the induction of mutations in the DNA of cells damaged by genotoxic agents. Translesion DNA synthesis (TLS) is the process by which cells copy DNA containing unrepaired damage that blocks progression of the replication fork. The DNA polymerases that catalyze TLS in mammals have been the topic of intense investigation over the last decade. DNA polymerase η (Pol η) is best understood and is active in error-free bypass of UV-induced DNA damage. The other TLS polymerases (Pol ι, Pol κ, REV1, and Pol ζ) have been studied extensively in vitro, but their in vivo role is only now being investigated using knockout mouse models of carcinogenesis. This paper will focus on the studies of mice and humans with altered expression of TLS polymerases and the effects on cancer induced by environmental agents.

Germline BRCA mutations denote a clinicopathologic subset of prostate cancer

PURPOSE

Increased prostate cancer risk has been reported for BRCA mutation carriers, but BRCA-associated clinicopathologic features have not been clearly defined.

EXPERIMENTAL DESIGN

We determined BRCA mutation prevalence in 832 Ashkenazi Jewish men diagnosed with localized prostate cancer between 1988 and 2007 and 454 Ashkenazi Jewish controls and compared clinical outcome measures among 26 BRCA mutation carriers and 806 noncarriers. Kruskal-Wallis tests were used to compare age of diagnosis and Gleason score, and logistic regression models were used to determine associations between carrier status, prostate cancer risk, and Gleason score. Hazard ratios (HR) for clinical end points were estimated using Cox proportional hazards models.

RESULTS

BRCA2 mutations were associated with a 3-fold risk of prostate cancer [odds ratio, 3.18; 95% confidence interval (95% CI), 1.52-6.66; P = 0.002] and presented with more poorly differentiated (Gleason score > or =7) tumors (85% versus 57%; P = 0.0002) compared with non-BRCA-associated prostate cancer. BRCA1 mutations conferred no increased risk. After 7,254 person-years of follow-up, and adjusting for clinical stage, prostate-specific antigen, Gleason score, and treatment, BRCA2 and BRCA1 mutation carriers had a higher risk of recurrence [HR (95% CI), 2.41 (1.23-4.75) and 4.32 (1.31-13.62), respectively] and prostate cancer-specific death [HR (95% CI), 5.48 (2.03-14.79) and 5.16 (1.09-24.53), respectively] than noncarriers.

CONCLUSIONS

BRCA2 mutation carriers had an increased risk of prostate cancer and a higher histologic grade, and BRCA1 or BRCA2 mutations were associated with a more aggressive clinical course. These results may have implications for tailoring clinical management of this subset of hereditary prostate cancer.