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

Transcriptome-wide association analysis identifies candidate susceptibility genes for prostate-specific antigen levels in men without prostate cancer

Deciphering the genetic basis of prostate-specific antigen (PSA) levels may improve their utility for prostate cancer (PCa) screening. Using genome-wide association study (GWAS) summary statistics from 95,768 PCa-free men, we conducted a transcriptome-wide association study (TWAS) to examine impacts of genetically predicted gene expression on PSA. Analyses identified 41 statistically significant (p < 0.05/12,192 = 4.10 × 10-6) associations in whole blood and 39 statistically significant (p < 0.05/13,844 = 3.61 × 10-6) associations in prostate tissue, with 18 genes associated in both tissues. Cross-tissue analyses identified 155 statistically significantly (p < 0.05/22,249 = 2.25 × 10-6) genes. Out of 173 unique PSA-associated genes across analyses, we replicated 151 (87.3%) in a TWAS of 209,318 PCa-free individuals from the Million Veteran Program. Based on conditional analyses, we found 20 genes (11 single tissue, nine cross-tissue) that were associated with PSA levels in the discovery TWAS that were not attributable to a lead variant from a GWAS. Ten of these 20 genes replicated, and two of the replicated genes had colocalization probability of >0.5: CCNA2 and HIST1H2BN. Six of the 20 identified genes are not known to impact PCa risk. Fine-mapping based on whole blood and prostate tissue revealed five protein-coding genes with evidence of causal relationships with PSA levels. Of these five genes, four exhibited evidence of colocalization and one was conditionally independent of previous GWAS findings. These results yield hypotheses that should be further explored to improve understanding of genetic factors underlying PSA levels.

Biochemical activity induced by a germline variation in KLK3 (PSA) associates with cellular function and clinical outcome in prostate cancer

Genetic variation at the 19q13.3 KLK locus is linked with prostate cancer susceptibility. The non-synonymous KLK3 SNP, rs17632542 (c.536T>C; Ile163Thr-substitution in PSA) is associated with reduced prostate cancer risk, however, the functional relevance is unknown. Here, we identify that the SNP variant-induced change in PSA biochemical activity as a previously undescribed function mediating prostate cancer pathogenesis. The 'Thr' PSA variant led to small subcutaneous tumours, supporting reduced prostate cancer risk. However, 'Thr' PSA also displayed higher metastatic potential with pronounced osteolytic activity in an experimental metastasis in-vivo model. Biochemical characterization of this PSA variant demonstrated markedly reduced proteolytic activity that correlated with differences in in-vivo tumour burden. The SNP is associated with increased risk for aggressive disease and prostate cancer-specific mortality in three independent cohorts, highlighting its critical function in mediating metastasis. Carriers of this SNP allele had reduced serum total PSA and a higher free/total PSA ratio that could contribute to late biopsy decisions and delay in diagnosis. Our results provide a molecular explanation for the prominent 19q13.3 KLK locus, rs17632542 SNP, association with a spectrum of prostate cancer clinical outcomes.

Genetic polymorphisms at 19q13.33 are associated with [-2]proPSA (p2PSA) levels and provide additional predictive value to prostate health index for prostate cancer

BACKGROUND

Prostate health index (phi), a derivative of [-2]proPSA (p2PSA), has shown better accuracy than prostate-specific antigen (PSA) in prostate cancer (PCa) detection. The present study was to investigate whether previously identified PSA-associated single nucleotide polymorphisms (SNPs) influence p2PSA or phi levels and lead to potential clinical utility.

METHODS

We conducted an observational prospective study with 2268 consecutive patients who underwent prostate biopsy in three tertiary medical centers from August 2013 to March 2019. Genotyping data of the 46 candidate genes with a ± 100 kb window were tested for association with p2PSA and phi levels using linear regression. Multivariable logistic regression models were performed and internally validated using repeated tenfold cross-validation. We further calculated personalized phi cutoff values based on the significant genotypes. Discriminative performance was assessed using decision curve analysis and net reclassification improvement (NRI) index.

RESULTS

We detected 11 significant variants at 19q13.33 which were p2PSA-associated independent of PCa. The most significant SNP, rs198978 in KLK2 (P_combined  = 5.73 × 10^-9 ), was also associated with phi values (P_combined  = 3.20 × 10^-6 ). Compared to the two commonly used phi cutoffs of 27.0 and 36.0, the personalized phi cutoffs had a significant NRI for PCa ranged from 5.23% to 9.70% among men carrying variant types (all p < .01).

CONCLUSION

Rs198978, is independently associated with p2PSA values, and can improve the diagnostic ability of phi for PCa using personalized cutoff values.

Identification of coding region SNPs from specific and sensitive mRNA biomarkers for the deconvolution of the semen donor in a body fluid mixture

mRNA markers provide a very promising method for the identification of human body fluids or tissues in the context of forensic investigations. Previous studies have shown that different body fluids can be distinguished from each other according to their specific mRNA biomarkers. In this study, we evaluated eight semen-specific mRNA markers (KLK3, NKX3-1, CKB, KLK2, PRAC1, SEMG1, TGM4, and SORD) that encompass 12 coding single nucleotide polymorphisms (cSNPs) to identify the semen contributor in a mixed stain. Five highly specific and sensitive mRNA markers for blood, menstrual blood, saliva, vaginal secretions, and skin were also incorporated into the PCR system as body fluid-positive controls. Reverse transcription polymerase chain reaction (RT-PCR), multiplex PCR and SNaPshot mini-sequencing assays were established for the identification of semen-specific mRNA. The amplicon size ranged from 133 to 337 bp. The semen-specific system was examined against blood, menstrual blood, saliva, vaginal secretions, and skin swabs. The eight mRNA biomarkers were semen-specific and could be successfully typed in laboratory-generated mixtures composed of different body fluids supplemented with 1 ng of semen cDNA. This system possessed a high sensitivity that ranged from 1:10-1:100 for detecting trace amounts of semen in semen-containing body fluid mixtures. Additionally, our results demonstrated that the cSNPs polymorphisms included in the mRNA markers were concordant with genomic DNA (gDNA). Despite the presence of other body fluids, the system exhibited high sensitivity and specificity to the semen in the mixture. In future studies, we will add other cSNPs from the semen-specific genes using massively parallel sequencing to further improve our system.

Validation of prostate cancer risk variants rs10993994 and rs7098889 by CRISPR/Cas9 mediated genome editing

GWAS have identified numerous SNPs associated with prostate cancer risk. One such SNP is rs10993994. It is located in the β-microseminoprotein (MSMB) promoter region, mediates MSMB prostate secretion levels, and is linked to mRNA expression changes in both MSMB and the adjacent gene NCOA4. In addition, our previous work showed a second SNP, rs7098889, is in positive linkage disequilibrium with rs10993994 and associated with MSMB expression independent of rs10993994. Here, we generate a series of clones with single alleles removed by double guide RNA (gRNA) mediated CRISPR/Cas9 deletions, through which we demonstrate that each of these SNPs independently and greatly alters MSMB expression in an allele-specific manner. We further show that these SNPs have no substantial effect on the expression of NCOA4. These data demonstrate that a single SNP can have a large effect on gene expression and illustrate the importance of functional validation studies to deconvolute observed correlations. The method we have developed is generally applicable to test any SNP for which a relevant heterozygous cell line is available. AUTHOR SUMMARY: In pursuing the underlying biological mechanism of prostate cancer pathogenesis, scientists utilized the existence of common single nucleotide polymorphisms (SNPs) in the human genome as genetic markers to perform large scale genome wide association studies (GWAS) and have so far identified more than a hundred prostate cancer risk variants. Such variants provide an unbiased and systematic new venue to study the disease mechanism, and the next big challenge is to translate these genetic associations to the causal role of altered gene function in oncogenesis. The majority of these variants are waiting to be studied and lots of them may act in oncogenesis through gene expression regulation. To prove the concept, we took rs10993994 and its linked rs7098889 as an example and engineered single cell clones by allelic-specific CRISPR/Cas9 deletion to separate the effect of each allele. We observed that a single nucleotide difference would lead to surprisingly high level of MSMB gene expression change in a gene specific and cell-type specific manner. Our study strongly supports the notion that differential level of gene expression caused by risk variants and their associated genetic locus play a major role in oncogenesis and also highlights the importance of studying the function of MSMB encoded β-MSP in prostate cancer pathogenesis.

Mechanism of semen liquefaction and its potential for a novel non-hormonal contraception†

Semen liquefaction is a proteolytic process where a gel-like ejaculated semen becomes watery due to the enzymatic activity of prostate-derived serine proteases in the female reproductive tract. The liquefaction process is crucial for the sperm to gain their motility and successful transport to the fertilization site in Fallopian tubes (or oviducts in animals). Hyperviscous semen or failure in liquefaction is one of the causes of male infertility. Therefore, the biochemical inhibition of serine proteases in the female reproductive tract after ejaculation is a prime target for novel contraceptive development. Herein, we will discuss protein components in the ejaculates responsible for semen liquefaction and any developments of contraceptive methods in the past that involve the liquefaction process.

Prostate cancer risk SNP rs10993994 is a trans-eQTL for SNHG11 mediated through MSMB

How genome-wide association studies-identified single-nucleotide polymorphisms (SNPs) affect remote genes remains unknown. Expression quantitative trait locus (eQTL) association meta-analysis on 496 prostate tumor and 602 normal prostate samples with 117 SNPs revealed novel cis-eQTLs and trans-eQTLs. Mediation testing and colocalization analysis demonstrate that MSMB is a cis-acting mediator for SNHG11 (P < 0.01). Removing rs10993994 in LNCaP cell lines by CRISPR/Cas9 editing shows that the C-allele corresponds with an over 100-fold increase in MSMB expression and 5-fold increase in SNHG11 compared with the T-allele. Colocalization analysis confirmed that the same set of SNPs associated with MSMB expression is associated with SNHG11 expression (posterior probability of shared variants is 66.6% in tumor and 91.4% in benign). These analyses further demonstrate variants driving MSMB expression differ in tumor and normal, suggesting regulatory network rewiring during tumorigenesis.

Association of KLK3, VAMP8 and MDM4 Genetic Variants within microRNA Binding Sites with Prostate Cancer: Evidence from Serbian Population

A growing number of studies have suggested that genetic variants affecting the micro-RNA- binding mechanisms (miRSNPs) constitute a promising novel class of biomarkers for prostate cancer (PCa) biology. Among the most extensively studied miRSNPs in the context of cancer is the variation rs4245739 in the MDM4 gene, while a recent large-scale analysis revealed significant differences in genotype distributions between aggressive and non-aggressive disease for rs1058205 in KLK3 and rs1010 in VAMP8. In this study, we examined a total of 1083 subjects for these three variants using Taqman® SNP Genotyping Assays. Three hundred and fifty-five samples of peripheral blood were obtained from patients with PCa and 358 samples from patients with benign prostatic hyperplasia (BPH). The control group consisted of 370 healthy volunteers. Comparisons of genotype distributions among PCa and BPH patients, as well as between PCa patients and healthy controls, yielded no evidence of association between the analyzed genetic variants and the risk of developing PCa. However, all three tested genetic variants have shown the association with the parameters of PCa progression. For KLK3 variant rs1058205, minor allele C was found to associate with the lower serum PSA score in PCa patients (PSA > 20 ng/ml vs. PSA < 10 ng/ml comparison, Prec = 0.038; ORrec = 0.20, 95%CI 0.04-1.05). The obtained results point out the potential relevance of the tested genetic variants for the disease aggressiveness assessment.

Prostate Cancer Risk-Associated Single-Nucleotide Polymorphism Affects Prostate-Specific Antigen Glycosylation and Its Function

BACKGROUND

Genetic association studies have reported single-nucleotide polymorphisms (SNPs) at chromosome 19q13.3 to be associated with prostate cancer (PCa) risk. Recently, the rs61752561 SNP (Asp84Asn substitution) in exon 3 of the kallikrein-related peptidase 3 (KLK3) gene encoding prostate-specific antigen (PSA) was reported to be strongly associated with PCa risk (P = 2.3 × 10^-8). However, the biological contribution of the rs61752561 SNP to PCa risk has not been elucidated.

METHODS

Recombinant PSA protein variants were generated to assess the SNP-mediated biochemical changes by stability and substrate activity assays. PC3 cell-PSA overexpression models were established to evaluate the effect of the SNP on PCa pathogenesis. Genotype-specific correlation of the SNP with total PSA (tPSA) concentrations and free/total (F/T) PSA ratio were determined from serum samples.

RESULTS

Functional analysis showed that the rs61752561 SNP affects PSA stability and structural conformation and creates an extra glycosylation site. This PSA variant had reduced enzymatic activity and the ability to stimulate proliferation and migration of PCa cells. Interestingly, the minor allele is associated with lower tPSA concentrations and high F/T PSA ratio in serum samples, indicating that the amino acid substitution may affect PSA immunoreactivity to the antibodies used in the clinical immunoassays.

CONCLUSIONS

The rs61752561 SNP appears to have a potential role in PCa pathogenesis by changing the glycosylation, protein stability, and PSA activity and may also affect the clinically measured F/T PSA ratio. Accounting for these effects on tPSA concentration and F/T PSA ratio may help to improve the accuracy of the current PSA test.

Mutations in the prostate specific antigen (PSA/KLK3) correlate with male infertility

Prostate specific antigen (PSA/KLK3) is known to be the chief executor of the fragmentation of semenogelins, dissolution of semen coagulum, thereby releasing sperm for active motility. Recent research has found that semenogelins also play significant roles in sperm fertility by affecting hyaluronidase activity, capacitation and motility, thereby making PSA important for sperm fertility beyond simple semen liquefaction. PSA level in semen has been shown to correlate with sperm motility, suggesting that PSA level/activity can affect fertility. However, no study investigating the genetic variations in the KLK3/PSA gene in male fertility has been undertaken. We analyzed the complete coding region of the KLK3 gene in ethnically matched 875 infertile and 290 fertile men to find if genetic variations in KLK3 correlate with infertility. Interestingly, this study identified 28 substitutions, of which 8 were novel (not available in public databases). Statistical comparison of the genotype frequencies showed that five SNPs, rs266881 (OR = 2.92, P < 0.0001), rs174776 (OR = 1.91, P < 0.0001), rs266875 (OR = 1.44, P = 0.016), rs35192866 (OR = 4.48, P = 0.025) and rs1810020 (OR = 2.08, P = 0.034) correlated with an increased risk of infertility. On the other hand, c.206 + 235 T > C, was more freuqent in the control group, showing protective association. Our findings suggest that polymorphisms in the KLK3 gene correlate with infertility risk.

Single-nucleotide polymorphism rs1058205 of KLK3 is associated with the risk of prostate cancer: A case-control study of Han Chinese men in Northeast China

BACKGROUND

Prostate cancer (PCa) is a serious public health concern for men worldwide. However, the risk factors for PCa remain largely unclear. Aim of this study was to investigate statistical associations between the risk of prostate cancer and the rs1058205 single-nucleotide polymorphism (SNP) of the KLK3 gene, which encodes the prostate specific antigen (PSA), in a case-control study of Han Chinese men in Northeast China.

METHODS

Using a high-resolution melting curve genotyping method, we determined the genotype and allele distributions of rs1058205 in 2 groups of Han Chinese men, consisting of 268 PCa patients and 298 healthy control subjects. Logistic regression was used to evaluate associations between rs1058205 genotypes and the risk of PCa. Tumor staging and Gleason score were included in a stratified analysis of PCa risk.

RESULTS

The frequency of the TC genotype of rs1058205 in the PCa group was significantly lower than that in the control group (P = 0.049). The serum PSA level in participants with the TC genotype was significantly lower than that of the TT and CC genotypes in both the PCa and control groups (P < 0.010 for both). The TT genotype was associated with PCa, both with and without adjustment for age (P < 0.010 and P = 0.047, respectively). The TT genotype was also associated with the moderate- and high-risk PCa categories (P = 0.007 and 0.027, respectively).

CONCLUSION

The TT genotype may represent a useful biomarker for identifying high risk of PCa and as a postoperative prognosticator in Chinese PCa patients.

Genome-wide association study of prostate-specific antigen levels identifies novel loci independent of prostate cancer

Prostate-specific antigen (PSA) levels have been used for detection and surveillance of prostate cancer (PCa). However, factors other than PCa—such as genetics—can impact PSA. Here we present findings from a genome-wide association study (GWAS) of PSA in 28,503 Kaiser Permanente whites and 17,428 men from replication cohorts. We detect 40 genome-wide significant (P<5 × 10⁻⁸) single-nucleotide polymorphisms (SNPs): 19 novel, 15 previously identified for PSA (14 of which were also PCa-associated), and 6 previously identified for PCa only. Further analysis incorporating PCa cases suggests that at least half of the 40 SNPs are PSA-associated independent of PCa. The 40 SNPs explain 9.5% of PSA variation in non-Hispanic whites, and the remaining GWAS SNPs explain an additional 31.7%; this percentage is higher in younger men, supporting the genetic basis of PSA levels. These findings provide important information about genetic markers for PSA that may improve PCa screening, thereby reducing over-diagnosis and over-treatment.

Prostate-specific antigen is used as a biomarker of prostate cancer, but levels can be affected by other factors not related to cancer. Here, the authors find genes associated with prostate specific antigen levels in healthy men, which could be used to reduce over-diagnosis and over-treatment.

Transcriptome reveals the overexpression of a kallikrein gene cluster (KLK1/3/7/8/12) in the Tibetans with high altitude-associated polycythemia

High altitude-associated polycythemia (HAPC) is a very common disease. However, it the disease is still unmanageable and the related molecular mechanisms remain largely unclear. In the present study, we aimed to explore the molecular mechanisms responsible for the development of HAPC using transcriptome analysis. Transcriptome analysis was conducted in 3 pairs of gastric mucosa tissues from patients with HAPC and healthy residents at a similar altitude. Endoscopy and histopathological analyses were used to examine the injury to gastric tissues. Molecular remodeling was performed for the interaction between different KLK members and cholesterol. HAPC was found to lead to morphological changes and pathological damage to the gastric mucosa of patients. A total of 10,304 differentially expressed genes (DEGs) were identified. Among these genes, 4,941 DEGs were upregulated, while 5,363 DEGs were downregulated in the patients with HAPC (fold change ≥2, P<0.01 and FDR <0.01). In particular, the kallikrein gene cluster (KLK1/3/7/8/12) was upregulated >17-fold. All the members had high-score binding cholesterol, particularly for the polymers of KLK7. The kallikrein gene cluster (KLK1/3/7/8/12) is on chromosome 19q13.3-13.4. The elevated levels of KLK1, KLK3, KLK7, KLK8 and KLK12 may be closely associated with the hypertension, inflammation, obesity and other gastric injuries associated with polycythemia. The interaction of KLKs and cholesterol maybe play an important role in the development of hypertension. The findings of the present study revealed that HAPC induces gastric injury by upregulating the kallikrein gene cluster (KLK1/3/7/8/12), which can bind cholesterol and result in kallikrein hypertension. These findings provide some basic information for understanding the molecular mechanisms responsible for HAPC and HAPC-related diseases.

Beyond prostate-specific antigen: utilizing novel strategies to screen men for prostate cancer

PURPOSE OF REVIEW

The purpose of this article is to review blood and urine tests that are currently available and under investigation for a role in prostate cancer screening and detection.

RECENT FINDINGS

Compared with total prostate-specific antigen (PSA) alone, its combination with percentage free-to-total PSA contributes greater specificity for prostate cancer, and is a component of two newer blood tests called the 4kScore and Prostate Health Index. All three tests improve the prediction of high-grade disease and are commercially available options to aid in initial or repeat prostate biopsy decisions. PCA3 is a urinary marker that is currently available for repeat prostate biopsy decisions. Although PCA3 alone has inferior prediction of clinically significant disease and requires collection of urine after digital rectal examination, it may be combined with other clinical variables or other urine markers like TMPRSS2:ERG to improve performance. Little data are available to support a role for single nucleotide polymorphisms or other investigational markers in early detection.

SUMMARY

Several commercially available blood and urine tests have been shown to improve specificity of PSA for high-grade prostate cancer. Use of such tests would decrease unnecessary biopsy and overdiagnosis of indolent disease. Biopsy of men with moderately elevated PSA without use of such a reflex test should be discouraged.

Biomarkers in localized prostate cancer

Biomarkers can improve prostate cancer diagnosis and treatment. Accuracy of prostate-specific antigen (PSA) for early diagnosis of prostate cancer is not satisfactory, as it is an organ- but not cancer-specific biomarker, and it can be improved by using models that incorporate PSA along with other test results, such as prostate cancer antigen 3, the molecular forms of PSA (proPSA, benign PSA and intact PSA), as well as kallikreins. Recent reports suggest that new tools may be provided by metabolomic studies as shown by preliminary data on sarcosine. Additional molecular biomarkers have been identified by the use of genomics, proteomics and metabolomics. We review the most relevant biomarkers for early diagnosis and management of localized prostate cancer.

Trp(250) -hK2 is defective in intracellular trafficking and activates the unfolded protein response

hK2, a member of the kallikrein protease family encoded by KLK2, is expressed exclusively in prostate and is a putative adjunct tumor marker for prostate cancer screening. The T allele of rs198977, a single nucleotide polymorphism in exon 5 of KLK2, codes for W-hK2 and is associated with lower serum hK2 levels and higher risk of prostate cancer than the C allele encoding R-hK2. To elucidate the mechanism that underlies this SNP's function, we transfected plasmids expressing R-hK2 or W-hK2 into PC3, HeLa and HEK293A cells and measured the hK2 level in cell lysates and conditioned media. The level of W-hK2 was lower than R-hK2 in conditioned media but was not different from R-hK2 in cell lysates. W-hK2 was hardly colocalized with Golgi-targeted fluorescent protein whereas R-hK2 colocalized. Reporter assays related to the unfolded protein response (UPR) and phospho-eIF2α immunoblot showed that W-hK2 increased UPR activity more than R-hK2. These results indicated that W-hK2 had a defect in cellular trafficking from the ER to the Golgi complex due to its misfolding and that it activated the UPR, suggesting a mechanism to explain the association of the T allele with higher prostate cancer risk.

A simple-to-use method incorporating genomic markers into prostate cancer risk prediction tools facilitated future validation

OBJECTIVES

To incorporate single-nucleotide polymorphisms (SNPs) into the Prostate Cancer Prevention Trial Risk Calculator (PCPTRC).

STUDY DESIGN AND SETTING

A multivariate random-effects meta-analysis of likelihood ratios (LRs) for 30 validated SNPs was performed, allowing the incorporation of linkage disequilibrium. LRs for an SNP were defined as the ratio of the probability of observing the SNP in prostate cancer cases relative to controls and estimated by published allele or genotype frequencies. LRs were multiplied by the PCPTRC prior odds of prostate cancer to provide updated posterior odds.

RESULTS

In the meta-analysis (prostate cancer cases/controls = 386,538/985,968), all but two of the SNPs had at least one statistically significant allele LR (P < 0.05). The two SNPs with the largest LRs were rs16901979 [LR = 1.575 for one risk allele, 2.552 for two risk alleles (homozygous)] and rs1447295 (LR = 1.307 and 1.887, respectively).

CONCLUSION

The substantial investment in genome-wide association studies to discover SNPs associated with prostate cancer risk and the ability to integrate these findings into the PCPTRC allows investigators to validate these observations, to determine the clinical impact, and to ultimately improve clinical practice in the early detection of the most common cancer in men.