Tagging SNPs in the kallikrein genes 3 and 2 on 19q13 and their associations with prostate cancer in men of European origin

An embedded method for gene identification problems involving unwanted data heterogeneity

BACKGROUND

Modern applications such as bioinformatics collecting data in various ways can easily result in heterogeneous data. Traditional variable selection methods assume samples are independent and identically distributed, which however is not suitable for these applications. Some existing statistical models capable of taking care of unwanted variation were developed for gene identification involving heterogeneous data, but they lack model predictability and suffer from variable redundancy.

RESULTS

By accounting for the unwanted heterogeneity effectively, our method have shown its superiority over several state-of-the art methods, which is validated by the experimental results in both unsupervised and supervised gene identification problems. Moreover, we also applied our method to a pan-cancer study where our method can identify the most discriminative genes best distinguishing different cancer types.

CONCLUSIONS

This article provides an alternative gene identification method that can accounting for unwanted data heterogeneity. It is a promising method to provide new insights into the complex cancer biology and clues for understanding tumorigenesis and tumor progression.

Kallikarein-related peptidase 3 common genetic variant and the risk of prostate cancer

Kallikarein-related peptidase 3 (KLK3) gene polymorphisms seem to play a role in susceptibility to prostate cancer (PC). The purpose of this study was to investigate the association between rs2735839 polymorphism of KLK3 gene and risk of PC in an Iranian population. In this case-control study, rs2735839 was genotyped in 532 patients with PC and 602 controls with benign prostate hyperplasia (BPH) using polymerase chain reaction-restriction fragment length polymorphism assay. The frequency of GG, AG, and AA genotypes of KLK3 polymorphism was 24.6% and 76.2%, 46.6% and 21.7%, and 28.8% and 2.1%, in patients with BPH and PC, respectively (P < 0.001). The frequency of G allele in patients with BPH and PC was 47.9% and 87%, respectively (odds ratio: 7.31; confidence interval: 5.88-9.10; P < 0.001). Patients with AG and GG genotypes had a higher total serum level of prostate-specific antigen (PSA) compared to those with AA genotype (P < 0.001). Patients with this polymorphism had higher risk of tumor with higher grade (P = 0.23), advanced stage (P = 0.11), perineural invasion (P = 0.07), and vascular invasion (P = 0.07) compared to those without it but this difference was not statistically significant. Based on our results, KLK3 gene polymorphism was associated with the risk of PC. Higher levels of PSA in the presence of KLK3 polymorphism in patients with PC indicated that rs2735839 polymorphism could be a risk factor for increased levels of PSA.

A genetic-based approach to personalized prostate cancer screening and treatment

PURPOSE OF REVIEW

Recent advances in sequencing technologies have allowed for the identification of genetic variants within germline DNA that can explain a significant portion of the genetic underpinnings of prostate cancer. Despite evidence suggesting that these genetic variants can be used for improved risk stratification, they have not yet been routinely incorporated into routine clinical practice. This review highlights their potential utility in prostate cancer screening.

RECENT FINDINGS

There are now almost 100 genetic variants, called single nucleotide polymorphisms (SNPs) that have been recently found to be associated with the risk of developing prostate cancer. In addition, some of these prostate cancer risk SNPs have also been found to influence prostate specific antigen (PSA) expression levels and potentially aggressive disease.

SUMMARY

Incorporation of panels of prostate cancer risk SNPs into clinical practice offers potential to provide improvements in patient selection for prostate cancer screening; PSA interpretation (e.g. by correcting for the presence of SNPs that influence PSA expression levels; decision for biopsy (using prostate cancer risk SNPs); and possibly the decision for treatment. A proposed clinical algorithm incorporating these prostate cancer risk SNPs is discussed.

The prostate cancer susceptibility variant rs2735839 near KLK3 gene is associated with aggressive prostate cancer and can stratify gleason score 7 patients

PURPOSE

Gleason score (GS) 7 prostate cancer is a heterogeneous disease with different clinical behavior. We sought to identify genetic biomarkers that may predict the aggressiveness of GS 7 diseases.

EXPERIMENTAL DESIGN

We genotyped 72 prostate cancer susceptibility SNPs identified in genome-wide association studies in 1,827 white men with histologically confirmed prostate adenocarcinoma. SNPs associated with disease aggressiveness were identified by comparing high-aggressive (GS ≥8) and low-aggressive (GS ≤6) cases. The significant SNPs were then tested to see whether they could further stratify GS 7 prostate cancer.

RESULTS

Three SNPs-rs2735839, rs10486567, and rs103294-were associated with biopsy-proven high-aggressive (GS ≥8) prostate cancer (P < 0.05). Furthermore, the frequency of the variant allele (A) at rs2735839 was significantly higher in patients with biopsy-proven GS 4+3 disease than in those with GS 3 + 4 disease (P = 0.003). In multivariate logistic regression analysis, patients carrying the A allele at rs2735839 exhibited a 1.85-fold (95% confidence interval, 1.31-2.61) increased risk of being GS 4 + 3 compared with those with GS 3 + 4. The rs2735839 is located 600 base pair downstream of the KLK3 gene (encoding PSA) on 19q13.33 and has been shown to modulate PSA level, providing strong biologic plausibility for its association with prostate cancer aggressiveness.

CONCLUSIONS

We confirmed the association of the rs2735839 with high-aggressive prostate cancer (GS ≥8). Moreover, we reported for the first time that rs2735839 can stratify GS 7 patients, which would be clinically important for more accurately assessing the clinical behavior of the intermediate-grade prostate cancer and for tailoring personalized treatment and posttreatment management.

Associations of prostate cancer risk variants with disease aggressiveness: results of the NCI-SPORE Genetics Working Group analysis of 18,343 cases

Genetic studies have identified single nucleotide polymorphisms (SNPs) associated with the risk of prostate cancer (PC). It remains unclear whether such genetic variants are associated with disease aggressiveness. The NCI-SPORE Genetics Working Group retrospectively collected clinicopathologic information and genotype data for 36 SNPs which at the time had been validated to be associated with PC risk from 25,674 cases with PC. Cases were grouped according to race, Gleason score (Gleason ≤ 6, 7, ≥ 8) and aggressiveness (non-aggressive, intermediate, and aggressive disease). Statistical analyses were used to compare the frequency of the SNPs between different disease cohorts. After adjusting for multiple testing, only PC-risk SNP rs2735839 (G) was significantly and inversely associated with aggressive (OR = 0.77; 95 % CI 0.69-0.87) and high-grade disease (OR = 0.77; 95 % CI 0.68-0.86) in European men. Similar associations with aggressive (OR = 0.72; 95 % CI 0.58-0.89) and high-grade disease (OR = 0.69; 95 % CI 0.54-0.87) were documented in African-American subjects. The G allele of rs2735839 was associated with disease aggressiveness even at low PSA levels (<4.0 ng/mL) in both European and African-American men. Our results provide further support that a PC-risk SNP rs2735839 near the KLK3 gene on chromosome 19q13 may be associated with aggressive and high-grade PC. Future prospectively designed, case-case GWAS are needed to identify additional SNPs associated with PC aggressiveness.

Association of INSIG2 polymorphism with overweight and LDL in children

Background

Dyslipidemia and overweight are common issues in children. Identifying genetic markers of risk could lead to targeted interventions. A polymorphism of SNP rs7566605 near insulin-induced gene 2 (INSIG2) has been identified as a strong candidate gene for obesity, through its feedback control of lipid synthesis.

Objective

To identify polymorphisms in INSIG2 which are associated with overweight (BMI ≥ 85% for age) and dyslipidemia in children. Hypothesis: The C allele of rs7566605 would be significantly associated with BMI and LDL.

Design/Methods

We genotyped 15 SNPs in/near INSIG2 in 1,058 healthy children (53% non-Hispanic white (NHW), 37% overweight) participating in a school based study. Genotype was compared with BMI and lipid markers, adjusting for age, gender, and puberty.

Results

We found a significant association between the SNP rs12464355 and LDL in NHW children, p < 0.001. The G allele is protective (lower LDL). A different SNP was associated with overweight in NHW: rs17047757. SNP rs7566605 was not associated with overweight or lipid levels.

Conclusions

We identified novel genetic associations between INSIG2 and both overweight and LDL in NHW children. Polymorphisms in INSIG2 may be important in the development of obesity through its effects on lipid regulation.

Genetic variants at 1q32.1, 10q11.2 and 19q13.41 are associated with prostate-specific antigen for prostate cancer screening in two Korean population-based cohort studies

Prostate-specific antigen (PSA) levels are affected by non-cancerous conditions such as benign prostatic hyperplasia, inflammations, and inherited factors. To search for genetic variants associated with PSA levels, we conducted a genome-wide association study (GWAS) using a two-stage design. A total of 554 men from the Korean Cancer Prevention Study-II were used as a discovery stage and 1575 men collected by the Korean Genome Epidemiology Study were used as a replication stage. Analysis by Genome-wide Human single-nucleotide polymorphism (SNP) array 5.0 was performed by using DNAs derived from venous blood. We analyzed the association between genetic variants and PSA levels using multivariate linear regression models, including age as a covariate. We detected 12 genome-wide significant signals on chromosome 1q32.1, 10q11.2, and 19q13.41 between PSA levels and SNPs. The top SNP associated with log PSA levels was rs2153904 in SLC45A3 (p values, 5.24×10(-9) to 2.00×10(-6)). We also investigated GWAS using 754 subjects from KCPS-II cohort whether our genome-wide significant loci were associated with a risk of prostate cancer (PCa) (200 PCa cases and 554 controls). Three of the SNPs on 10q11.2, rs7077830, rs2611489, and rs4631830, were associated with a risk of PCa. However, two loci, 1q32.1 and 19q13, were not significantly associated with a PCa risk. We suggest that our results for some but not all PCa risk SNPs to be associated with PSA levels could be used as an evidence for the advance of individual PCa screening strategies, such as applying a personalized cutoff value for PSA.

Polymorphisms influencing prostate-specific antigen concentration may bias genome-wide association studies on prostate cancer

BACKGROUND

Genome-wide association studies (GWAS) have produced weak (OR = 1.1-1.5) but significant associations between single nucleotide polymorphisms (SNPs) and prostate cancer. However, these associations may be explained by detection bias caused by SNPs influencing PSA concentration. Thus, in a simulation study, we quantified the extent of bias in the association between a SNP and prostate cancer when the SNP influences PSA concentration.

METHODS

We generated 2,000 replicate cohorts of 20,000 men using real-world estimates of prostate cancer risk, prevalence of carrying ≥1 minor allele, PSA concentration, and the influence of a SNP on PSA concentration. We modeled risk ratios (RR) of 1.00, 1.25, and 1.50 for the association between carrying ≥1 minor allele and prostate cancer. We calculated mean betas from the replicate cohorts and quantified bias under each scenario.

RESULTS

Assuming no association between a SNP and prostate cancer, the estimated mean bias in betas ranged from 0.02 to 0.10 for ln PSA being 0.05 to 0.20 ng/mL higher in minor allele carriers; the mean biased RRs ranged from 1.03 to 1.11. Assuming true RRs = 1.25 and 1.50, the biased RRs were as large as 1.39 and 1.67, respectively.

CONCLUSION

Estimates of the association between SNPs and prostate cancer can be biased to the magnitude observed in published GWAS, possibly resulting in type I error. However, large associations (RR > 1.10) may not fully be explained by this bias.

IMPACT

The influence of SNPs on PSA concentration should be considered when interpreting results from GWAS on prostate cancer.

Genetic variation in KLK2 and KLK3 is associated with concentrations of hK2 and PSA in serum and seminal plasma in young men

BACKGROUND

Genetic variants in KLK2 and KLK3 have been associated with increased serum concentrations of their encoded proteins, human kallikrein-related peptidase 2 (hK2) and prostate-specific antigen (PSA), and with prostate cancer in older men. Low PSA concentrations in seminal plasma (SP) have been associated with low sperm motility. To evaluate whether KLK2 and KLK3 genetic variants affect physiological prostatic secretion, we studied the association of SNPs with hK2 and PSA concentrations in SP and serum of young, healthy men.

METHODS

Leukocyte DNA was extracted from 303 male military conscripts (median age 18.1 years). Nine SNPs across KLK2-KLK3 were genotyped. We measured PSA and hK2 in SP and serum using immunofluorometric assays. The association of genotype frequencies with hK2 and PSA concentrations was tested with the Kruskal-Wallis test.

RESULTS

Four KLK2 SNPs (rs198972, rs198977, rs198978, and rs80050017) were strongly associated with hK2 concentrations in SP and serum, with individuals homozygous for the major alleles having 3- to 7-fold higher concentrations than the intermediate concentrations found in other homozygotes and heterozygotes (all P < 0.001). Three of these SNPs were significantly associated with percentage of free PSA (%fPSA) in serum (all P < 0.007). Three KLK3 SNPs showed associations with PSA in SP, and the rs1058205 SNP was associated with total PSA in serum (P = 0.001) and %fPSA (P = 0.015).

CONCLUSIONS

Associations observed in young, healthy men between the SP and serum concentrations of hK2 and PSA and several genetic variants in KLK2 and KLK3 could be useful to refine models of PSA cutoff values in prostate cancer testing.

Personalized prostate specific antigen testing using genetic variants may reduce unnecessary prostate biopsies

PURPOSE

Recent studies have identified genetic variants associated with increased serum prostate specific antigen concentrations and prostate cancer risk, raising the possibility of diagnostic bias. By correcting for the effects of these variants on prostate specific antigen, it may be possible to create a personalized prostate specific antigen cutoff to more accurately identify individuals for whom biopsy is recommended. Therefore, we determined how many men would continue to meet common biopsy criteria after genetic correction of their measured prostate specific antigen concentrations.

MATERIALS AND METHODS

The genotypes of 4 single nucleotide polymorphisms previously associated with serum prostate specific antigen levels (rs2736098, rs10788160, rs11067228 and rs17632542) were determined in 964 healthy Caucasian volunteers without prostate cancer. Genetic correction of prostate specific antigen was performed by dividing an individual's prostate specific antigen value by his combined genetic risk. Analyses were used to compare the percentage of men who would meet commonly used biopsy thresholds (2.5 ng/ml or greater, or 4.0 ng/ml or greater) before and after genetic correction.

RESULTS

Genetic correction of serum prostate specific antigen results was associated with a significantly decreased percentage of men meeting biopsy thresholds. Genetic correction could lead to a 15% or 20% relative reduction in the total number of biopsies using a biopsy threshold of 2.5 ng/ml or greater, or 4.0 ng/ml or greater, respectively. In addition, genetic correction could result in an 18% to 22% reduction in the number of potentially unnecessary biopsies and a 3% decrease in potentially delayed diagnoses.

CONCLUSIONS

Our results suggest that 4 single nucleotide polymorphisms can be used to adjust a man's measured prostate specific antigen concentration and potentially delay or prevent unnecessary prostate biopsies in Caucasian men.

Androgen metabolism and JAK/STAT pathway genes and prostate cancer risk

BACKGROUND

Prostate cancer (PC) is the most frequently diagnosed solid tumor in U.S. men. Genome-wide association studies (GWAS) have identified over 40 risk-associated single nucleotide polymorphisms (SNPs), including variants in androgen pathway genes (e.g., KLK3 and AR). Androgens are important in PC and genes involved in this pathway are therefore candidates for conferring susceptibility to PC.

METHODS

In this hypothesis-testing study, we evaluated PC risk in association with SNPs in 22 candidate genes involved in androgen metabolism or interactions with the androgen receptor (AR). A total of 187 SNPs were genotyped in 1458 cases and 1351 age-matched controls from a population-based study. PC risk was estimated using adjusted unconditional logistic regression and multinomial regression models.

RESULTS

Single SNP analyses showed evidence (p < 0.05) for associations with 14 SNPs in 9 genes: NKX3.1, HSD17B3, AKR1C3, SULT2A1, CYP17A1, KLK3, JAK2, NCOA4 and STAT3. The most significant result was observed for rs2253502 in HSD17B3 (odds ratio, OR = 0.57, 95% CI: 0.39-0.84). In addition, five SNPs in four genes (CYP17A1, HSD17B4, NCOA4, and SULT2A1) were associated with more aggressive disease (p < 0.01).

CONCLUSIONS

Our results replicate previously reported associations for SNPs in CYP17A1, HSD17B3, ARK1C3, NKX3.1, NCOA4 and KLK3. In addition, novel associations were observed for SNPs in JAK2, HSD17B4, and SULT2A1. These results will require replication in larger studies.

Single nucleotide polymorphism barcoding to evaluate oral cancer risk using odds ratio-based genetic algorithms

Cancers often involve the synergistic effects of gene-gene interactions, but identifying these interactions remains challenging. Here, we present an odds ratio-based genetic algorithm (OR-GA) that is able to solve the problems associated with the simultaneous analysis of multiple independent single nucleotide polymorphisms (SNPs) that are associated with oral cancer. The SNP interactions between four SNPs-namely rs1799782, rs2040639, rs861539, rs2075685, and belonging to four genes (XRCC1, XRCC2, XRCC3, and XRCC4)-were tested in this study, respectively. The GA decomposes the SNPs sets into different SNP combinations with their corresponding genotypes (called SNP barcodes). The GA can effectively identify a specific SNP barcode that has an optimized fitness value and uses this to calculate the difference between the case and control groups. The SNP barcodes with a low fitness value are naturally removed from the population. Using two to four SNPs, the best SNP barcodes with maximum differences in occurrence between the case and control groups were generated by GA algorithm. Subsequently, the OR provides a quantitative measure of the multiple SNP synergies between the oral cancer and control groups by calculating the risk related to the best SNP barcodes and others. When these were compared to their corresponding non-SNP barcodes, the estimated ORs for oral cancer were found to be great than 1 [approx. 1.72-2.23; confidence intervals (CIs): 0.94-5.30, p < 0.03-0.07] for various specific SNP barcodes with two to four SNPs. In conclusion, the proposed OR-GA method successfully generates SNP barcodes, which allow oral cancer risk to be evaluated and in the process the OR-GA method identifies possible SNP-SNP interactions.

Association between Prostinogen (KLK15) genetic variants and prostate cancer risk and aggressiveness in Australia and a meta-analysis of GWAS data

BACKGROUND

Kallikrein 15 (KLK15)/Prostinogen is a plausible candidate for prostate cancer susceptibility. Elevated KLK15 expression has been reported in prostate cancer and it has been described as an unfavorable prognostic marker for the disease.

OBJECTIVES

We performed a comprehensive analysis of association of variants in the KLK15 gene with prostate cancer risk and aggressiveness by genotyping tagSNPs, as well as putative functional SNPs identified by extensive bioinformatics analysis. METHODS AND DATA SOURCES: Twelve out of 22 SNPs, selected on the basis of linkage disequilibrium pattern, were analyzed in an Australian sample of 1,011 histologically verified prostate cancer cases and 1,405 ethnically matched controls. Replication was sought from two existing genome wide association studies (GWAS): the Cancer Genetic Markers of Susceptibility (CGEMS) project and a UK GWAS study.

RESULTS

Two KLK15 SNPs, rs2659053 and rs3745522, showed evidence of association (p<0.05) but were not present on the GWAS platforms. KLK15 SNP rs2659056 was found to be associated with prostate cancer aggressiveness and showed evidence of association in a replication cohort of 5,051 patients from the UK, Australia, and the CGEMS dataset of US samples. A highly significant association with Gleason score was observed when the data was combined from these three studies with an Odds Ratio (OR) of 0.85 (95% CI = 0.77-0.93; p = 2.7×10(-4)). The rs2659056 SNP is predicted to alter binding of the RORalpha transcription factor, which has a role in the control of cell growth and differentiation and has been suggested to control the metastatic behavior of prostate cancer cells.

CONCLUSIONS

Our findings suggest a role for KLK15 genetic variation in the etiology of prostate cancer among men of European ancestry, although further studies in very large sample sets are necessary to confirm effect sizes.

The physiology and pathobiology of human kallikrein-related peptidase 6 (KLK6)

The human kallikrein-related peptidase 6 (KLK6) gene belongs to the 15-member kallikrein (KLK) gene family mapping to chromosome 19q13.3-13.4. Encoding for an enzyme with trypsin-like properties, KLK6 can degrade components of the extracellular matrix. The successful utilisation of another KLK member (KLK3/PSA) for prostate cancer diagnosis has led many to evaluate KLK6 as a potential biomarker for other cancer and diseased states. The observed dysregulated expression in cancers, neurodegenerative diseases and skin conditions has led to the discovery that KLK6 participates in other cellular pathways including inflammation, receptor activation and regulation of apoptosis. Moreover, the improvements in high-throughput genomics have not only enabled the identification of sequence polymorphisms, but of transcript variants, whose functional significances have yet to be realised. This comprehensive review will summarise the current findings of KLK6 pathophysiology and discuss its potential as a viable biomarker.

Genetics of prostate cancer risk

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

Genetic correction of PSA values using sequence variants associated with PSA levels

Measuring serum levels of the prostate-specific antigen (PSA) is the most common screening method for prostate cancer. However, PSA levels are affected by a number of factors apart from neoplasia. Notably, around 40% of the variability of PSA levels in the general population is accounted for by inherited factors, suggesting that it may be possible to improve both sensitivity and specificity by adjusting test results for genetic effects. To search for sequence variants that associate with PSA levels, we performed a genome-wide association study and follow-up analysis using PSA information from 15,757 Icelandic and 454 British men not diagnosed with prostate cancer. Overall, we detected a genome-wide significant association between PSA levels and single-nucleotide polymorphisms (SNPs) at six loci: 5p15.33 (rs2736098), 10q11 (rs10993994), 10q26 (rs10788160), 12q24 (rs11067228), 17q12 (rs4430796), and 19q13.33 [rs17632542 (KLK3: I179T)], each with P(combined) <3 × 10(-10). Among 3834 men who underwent a biopsy of the prostate, the 10q26, 12q24, and 19q13.33 alleles that associate with high PSA levels are associated with higher probability of a negative biopsy (odds ratio between 1.15 and 1.27). Assessment of association between the six loci and prostate cancer risk in 5325 cases and 41,417 controls from Iceland, the Netherlands, Spain, Romania, and the United States showed that the SNPs at 10q26 and 12q24 were exclusively associated with PSA levels, whereas the other four loci also were associated with prostate cancer risk. We propose that a personalized PSA cutoff value, based on genotype, should be used when deciding to perform a prostate biopsy.

Association of KLK3 (PSA) genetic variants with prostate cancer risk and PSA levels

Genome-wide association studies have identified genetic markers in kallikrein-related peptidase 3 (KLK3) associated with prostate cancer. However, some of these markers are also associated with prostate-specific antigen (PSA) levels, so it is unclear whether the polymorphisms are causal or if the association with risk is solely due to detection bias through PSA screening. PSA is a biologically active serine protease, cleaving insulin-like growth factor-binding protein. We examined the association of single-nucleotide polymorphisms (SNPs) in KLK3 with prostate cancer risk, disease-specific survival and pre-diagnostic PSA levels in a case-control study nested within the Physicians' Health Study, which began in 1982, with over 27 years of follow-up. We genotyped SNPs spanning the entire KLK3 locus to capture common variation at high resolution. Six polymorphisms were significantly associated with prostate cancer incidence (P < 0.05); the odds ratios per minor allele ranged from 0.88 to 0.73. For four of these, the odds ratios were lower when restricting to cases diagnosed in the pre-PSA screening era (before 1989). The four alleles significantly associated with lower PSA levels were also associated with lower prostate cancer risk. KLK3 variants were not significantly associated with stage at diagnosis, risk of lethal cancer or survival. Our results suggest that detection bias due to the association of KLK3 variants with PSA levels cannot completely explain the association with prostate cancer risk. Understanding the mechanism by which genetic variation in KLK3 affects prostate cancer risk has important implications for study of the biological role of PSA in prostate tumorigenesis.

Association of prostate cancer risk Loci with disease aggressiveness and prostate cancer-specific mortality

Genome-wide association studies have detected more than 30 inherited prostate cancer risk variants. While clearly associated with risk, their relationship with clinical outcome, particularly prostate cancer-specific mortality, is less well known. We investigated whether the risk variants are associated with various measures of disease aggressiveness and prostate cancer-specific mortality. In a cohort of 3,945 men of European ancestry with prostate cancer, we genotyped 36 single nucleotide polymorphisms (SNP): 35 known prostate cancer risk variants and one SNP (rs4054823) that was recently reported to be associated with prostate cancer aggressiveness. The majority of subjects had a diagnosis of prostate cancer between 1995 and 2004, and the cohort included a total of 580 prostate cancer-specific deaths. We evaluated associations between the 36 polymorphisms and prostate cancer survival, as well as other clinical parameters including age at diagnosis, prostate-specific antigen (PSA) at diagnosis, and Gleason score. Two SNPs, rs2735839 at chromosome 19q13 and rs7679673 at 4q24, were associated with prostate cancer-specific survival (P = 7 × 10(-4) and 0.014, respectively). A total of 12 SNPs were associated with other variables (P < 0.05): age at diagnosis, PSA at diagnosis, Gleason score, and/or disease aggressiveness based on D'Amico criteria. Genotype status at rs4054823 was not associated with aggressiveness or outcome. Our results identify two common polymorphisms associated with prostate cancer-specific mortality.

Replication of genetic variants from genome-wide association studies with metabolic traits in an island population of the Adriatic coast of Croatia

Twenty-two single-nucleotide polymorphisms (SNPs) in 10 gene regions previously identified in obesity and type 2 diabetes (T2D) genome-wide association studies (GWAS) were evaluated for association with metabolic traits in a sample from an island population of European descent. We performed a population-based study using 18 anthropometric and biochemical traits considered as continuous variables in a sample of 843 unrelated subjects (360 men and 483 women) aged 18-80 years old from the island of Hvar on the eastern Adriatic coast of Croatia. All eight GWAS SNPs in FTO were significantly associated with weight, body mass index, waist circumference and hip circumference; 20 of the 32 nominal P-values remained significant after permutation testing for multiple corrections. The strongest associations were found between the two TCF7L2 GWAS SNPs with fasting plasma glucose and HbA1c levels, all four P-values remained significant after permutation tests. Nominally significant associations were found between several SNPs and other metabolic traits; however, the significance did not hold after permutation tests. Although the sample size was modest, our study strongly replicated the association of FTO variants with obesity-related measures and TCF7L2 variants with T2D-related traits. The estimated effect sizes of these variants were larger or comparable to published studies. This is likely attributable to the homogenous genetic background of the relatively isolated study population.

Genome-wide linkage analysis of 1,233 prostate cancer pedigrees from the International Consortium for Prostate Cancer Genetics using novel sumLINK and sumLOD analyses

BACKGROUND

Prostate cancer (PC) is generally believed to have a strong inherited component, but the search for susceptibility genes has been hindered by the effects of genetic heterogeneity. The recently developed sumLINK and sumLOD statistics are powerful tools for linkage analysis in the presence of heterogeneity.

METHODS

We performed a secondary analysis of 1,233 PC pedigrees from the International Consortium for Prostate Cancer Genetics (ICPCG) using two novel statistics, the sumLINK and sumLOD. For both statistics, dominant and recessive genetic models were considered. False discovery rate (FDR) analysis was conducted to assess the effects of multiple testing.

RESULTS

Our analysis identified significant linkage evidence at chromosome 22q12, confirming previous findings by the initial conventional analyses of the same ICPCG data. Twelve other regions were identified with genome-wide suggestive evidence for linkage. Seven regions (1q23, 5q11, 5q35, 6p21, 8q12, 11q13, 20p11-q11) are near loci previously identified in the initial ICPCG pooled data analysis or the subset of aggressive PC pedigrees. Three other regions (1p12, 8p23, 19q13) confirm loci reported by others, and two (2p24, 6q27) are novel susceptibility loci. FDR testing indicates that over 70% of these results are likely true positive findings. Statistical recombinant mapping narrowed regions to an average of 9 cM.

CONCLUSIONS

Our results represent genomic regions with the greatest consistency of positive linkage evidence across a very large collection of high-risk PC pedigrees using new statistical tests that deal powerfully with heterogeneity. These regions are excellent candidates for further study to identify PC predisposition genes.

Blood biomarker levels to aid discovery of cancer-related single-nucleotide polymorphisms: kallikreins and prostate cancer

Polymorphisms associated with prostate cancer include those in three genes encoding major secretory products of the prostate: KLK2 (encoding kallikrein-related peptidase 2; hK2), KLK3 (encoding prostate-specific antigen; PSA), and MSMB (encoding beta-microseminoprotein). PSA and hK2, members of the kallikrein family, are elevated in sera of men with prostate cancer. In a comprehensive analysis that included sequencing of all coding, flanking, and 2 kb of putative promoter regions of all 15 kallikrein (KLK) genes spanning approximately 280 kb on chromosome 19q, we identified novel single-nucleotide polymorphisms (SNP) and genotyped 104 SNPs in 1,419 cancer cases and 736 controls in Cancer Prostate in Sweden 1, with independent replication in 1,267 cases and 901 controls in Cancer Prostate in Sweden 2. This verified prior associations of SNPs in KLK2 and in MSMB (but not in KLK3) with prostate cancer. Twelve SNPs in KLK2 and KLK3 were associated with levels of PSA forms or hK2 in plasma of control subjects. Based on our comprehensive approach, this is likely to represent all common KLK variants associated with these phenotypes. A T allele at rs198977 in KLK2 was associated with increased cancer risk and a striking decrease of hK2 levels in blood. We also found a strong interaction between rs198977 genotype and hK2 levels in blood in predicting cancer risk. Based on this strong association, we developed a model for predicting prostate cancer risk from standard biomarkers, rs198977 genotype, and rs198977 x hK2 interaction; this model had greater accuracy than did biomarkers alone (area under the receiver operating characteristic curve, 0.874 versus 0.866), providing proof in principle to clinical application for our findings.

Common SNPs in FTO gene are associated with obesity related anthropometric traits in an island population from the eastern Adriatic coast of Croatia

BACKGROUND

Multiple studies have provided compelling evidence that the FTO gene variants are associated with obesity measures. The objective of the study was to investigate whether FTO variants are associated with a broad range of obesity related anthropometric traits in an island population.

METHODOLOGY/PRINCIPAL FINDINGS

We examined genetic association between 29 FTO SNPs and a comprehensive set of anthropometric traits in 843 unrelated individuals from an island population in the eastern Adriatic coast of Croatia. The traits include 11 anthropometrics (height, weight, waist circumference, hip circumference, bicondilar upper arm width, upper arm circumference, and biceps, triceps, subscapular, suprailiac and abdominal skin-fold thicknesses) and two derived measures (BMI and WHR). Using single locus score tests, 15 common SNPs were found to be significantly associated with "body fatness" measures such as weight, BMI, hip and waist circumferences with P-values ranging from 0.0004 to 0.01. Similar but less significant associations were also observed between these markers and bicondilar upper arm width and upper arm circumference. Most of these significant findings could be explained by a mediating effect of "body fatness". However, one unique association signal between upper arm width and rs16952517 (P-value = 0.00156) could not be explained by this mediating effect. In addition, using a principle component analysis and conditional association tests adjusted for "body fatness", two novel association signals were identified between upper arm circumference and rs11075986 (P-value = 0.00211) and rs16945088 (P-value = 0.00203).

CONCLUSIONS/SIGNIFICANCE

The current study confirmed the association of common variants of FTO gene with "body fatness" measures in an isolated island population. We also observed evidence of pleiotropic effects of FTO gene on fat-free mass, such as frame size and muscle mass assessed by bicondilar upper arm width and upper arm circumference respectively and these pleiotropic effects might be influenced by variants that are different from the ones associated with "body fatness".

A comprehensive resequence analysis of the KLK15-KLK3-KLK2 locus on chromosome 19q13.33

Single nucleotide polymorphisms (SNPs) in the KLK3 gene on chromosome 19q13.33 are associated with serum prostate-specific antigen (PSA) levels. Recent genome wide association studies of prostate cancer have yielded conflicting results for association of the same SNPs with prostate cancer risk. Since the KLK3 gene encodes the PSA protein that forms the basis for a widely used screening test for prostate cancer, it is critical to fully characterize genetic variation in this region and assess its relationship with the risk of prostate cancer. We have conducted a next-generation sequence analysis in 78 individuals of European ancestry to characterize common (minor allele frequency, MAF >1%) genetic variation in a 56 kb region on chromosome 19q13.33 centered on the KLK3 gene (chr19:56,019,829-56,076,043 bps). We identified 555 polymorphic loci in the process including 116 novel SNPs and 182 novel insertion/deletion polymorphisms (indels). Based on tagging analysis, 144 loci are necessary to tag the region at an r (2) threshold of 0.8 and MAF of 1% or higher, while 86 loci are required to tag the region at an r (2) threshold of 0.8 and MAF >5%. Our sequence data augments coverage by 35 and 78% as compared to variants in dbSNP and HapMap, respectively. We observed six non-synonymous amino acid or frame shift changes in the KLK3 gene and three changes in each of the neighboring genes, KLK15 and KLK2. Our study has generated a detailed map of common genetic variation in the genomic region surrounding the KLK3 gene, which should be useful for fine-mapping the association signal as well as determining the contribution of this locus to prostate cancer risk and/or regulation of PSA expression.

Common variants in 8q24 are associated with risk for prostate cancer and tumor aggressiveness in men of European ancestry

BACKGROUND

Recent whole genome association studies have independently identified multiple prostate cancer (PC) risk variants on 8q24. We have evaluated association of common variants in this region with PC susceptibility and tumor aggressiveness in a sample of European American men.

METHODS

Forty-nine tagging SNPs including three previously reported significant variants (rs1447295, rs6983267, rs16901979) and seven variants in the 5' upstream region of the MYC proto-oncogene were tested for association with susceptibility to PC and tumor aggressiveness in 596 histologically verified PC cases and 567 ethnically matched controls.

RESULTS

Significant associations with susceptibility to PC were found at 17 SNPs, four of which (rs1016342, rs1378897, rs871135, and rs6470517) remained significant after adjusting for multiple corrections. One of the associated SNPs, rs871135, is located in the putative gene POU5F1P1 within the 8q24 region. An in slico analysis showed that the associated variant of this SNP alters a transcription factor implicating a plausible regulatory role. Additionally, one of the significantly associated SNPs, rs6470517, with PC susceptibility showed a significant over-representation of the G allele in cases with aggressive tumor.

CONCLUSIONS

Although this study does not directly confirm associations of the three specific SNPs (cited above), it corroborates reported signals of association in 8q24 reaffirming that genetic variation on 8q24 influences susceptibility to PC in men of European ancestry. Although our study did not confirm the allelic association of rs1447295, meta-analysis of this SNP provided support to previous reported associations. Further, this study implicates the 8q24 region with aggressive forms of PC.

MicroRNA-330 acts as tumor suppressor and induces apoptosis of prostate cancer cells through E2F1-mediated suppression of Akt phosphorylation

MicroRNAs (miRNAs) make up a novel class of gene regulators; they function as oncogenes or tumor suppressors by targeting tumor-suppressor genes or oncogenes. A recent study that analysed a large number of human cancer cell lines showed that miR-330 is a potential tumor-suppressor gene. However, the function and molecular mechanism of miR-330 in determining the aggressiveness of human prostate cancer has not been studied. Here, we show that miR-330 is significantly lower expressed in human prostate cancer cell lines than in nontumorigenic prostate epithelial cells. Bioinformatics analyses reveal a conserved target site for miR-330 in the 3'-untranslated region (UTR) of E2F1 at nucleotides 1018-1024. MiR-330 significantly suppressed the activity of a luciferase reporter containing the E2F1-3'-UTR in the cells. This activity could be abolished with the transfection of anti-miR-330 or mutated E2F1-3'-UTR. In addition, the expression level of miR-330 and E2F1 was inversely correlated in cell lines and prostate cancer specimens. After overexpressing of miR-330 in PC-3 cells, cell growth was suppressed by reducing E2F1-mediated Akt phosphorylation and thereby inducing apoptosis. Collectively, this is the first study to show that E2F1 is negatively regulated by miR-330 and also show that miR-330 induces apoptosis in prostate cancer cells through E2F1-mediated suppression of Akt phosphorylation.

Reflections on the tissue kallikrein and kallikrein-related peptidase family – from mice to men – what have we learnt in the last two decades?

The genes encoding the kininogenase, glandular tissue kallikrein, in rodents and man were first described in the mid-1980s. Remarkably, they appeared to be part of a much larger highly conserved family of genes (GK) in rodents, but only had two paralogs in man. This discrepancy was not rectified until the late 1990s/2000 with the identification of a cluster of 12 more kallikrein-related (KLK) genes in the human 19q13 locus and the subsequent identification of their rodent homologs. Interestingly, there are remarkable similarities in expression patterns, hormonal regulation and functional attributes of the old (GK) and new (KLK) families which underscore the evolutionary conservation across these loci and species. This historical perspective focuses on the lessons learned from earlier studies on the rodentGKgene families and the striking similarities of some attributes, yet uniqueness, of others. These earlier findings have all contributed to the current status of the KLK serine peptidase-encoding gene family as an exciting source of new biomarkers and therapeutic targets.