Altered glycosylation pattern allows the distinction between prostate-specific antigen (PSA) from normal and tumor origins

Prostate-specific antigen (PSA) is a glycoprotein secreted by prostate epithelial cells. PSA is currently used as a marker of prostate carcinoma because high levels of PSA are indicative of a tumor situation. However, PSA tests still suffer from a lack of specificity to distinguish between benign prostate hyperplasia and prostate cancer. To determine whether PSA glycosylation could provide a means of differentiating between PSA from normal and tumor origins, N-glycan characterization of PSA from seminal fluid and prostate cancer cells (LNCaP cell line) by sequencing analysis and mass spectrometry was carried out. Glycans from normal PSA (that correspond to low and high pI PSA fractions) were sialylated biantennary complex structures, half of them being disialylated in the low pI PSA fraction and mostly monosialylated in the high pI PSA. PSA from LNCaP cells was purified to homogeneity, and its glycan analysis showed a significantly different pattern, especially in the outer ends of the biantennary complex structures. In contrast to normal PSA glycans, which were sialylated, LNCaP PSA oligosaccharides were all neutral and contained a higher fucose content. In 10-15% of the structures fucose was linked alpha1-2 to galactose, forming the H2 epitope absent in normal PSA. GalNAc was increased in LNCaP glycans to 65%, whereas in normal PSA it was only present in 25% of the structures. These carbohydrate differences allow a distinction to be made between PSA from normal and tumor origins and suggest a valuable biochemical tool for diagnosis and follow-up purposes.     

Glycotyping of prostate specific antigen

Measurement of serum levels of the prostate specific antigen (PSA) is now widely used for the diagnosis of prostate cancer and benign prostate hyperplasia. This serum marker is of value since it is derived only from the tissue of interest, but increased levels of PSA in serum do not allow a completely clear cut diagnosis of benign versus malignant changes. Since PSA is a glycoprotein with one asparagine linked oligosaccharide, and since malignant transformation often leads to an increased branching of such oligosaccharides, we initially studied the asparagine linked structures on PSA made by a cell line derived from malignant metastatic prostate tissue. We observed that unlike normal PSA, which bears only biantennary oligosaccharides, PSA from the metastatic cell line has a mixture of biantennary and triantennary oligosaccharides. Further experiments will reveal carbohydrate differences derived from the PSA from sera or, prostate tissue of normal versus prostate cancer patients, and of the utility of such carbo-hydrate differences as a possible diagnostic marker for prostate cancer.     

Oligosaccharide profiles of the prostate specific antigen in free and complexed forms from the prostate cancer patient serum and in seminal plasma: a glycopeptide approach

The oligosaccharide structures of prostate specific antigen (PSA) are expected to be useful in discriminating prostate cancer from benign conditions both accompanied by increased serum PSA levels. A large proportion of PSA forms a covalent complex with a glycoprotein, alpha(1)-antichymotrypsin, in human blood. In the present study, the glycan profiles of free and complexed forms of PSA from cancer patient serum and of seminal plasma PSA were compared by analyzing the glycopeptides obtained by lysylendopeptidase digestion of the electrophoretically separated PSA with mass spectrometry. The profiles of the PSA N-glycans from the free and complexed molecules were quite similar to each other and consisted of fucosylated biantennary oligosaccharides as the major class. They were mostly sialylated, and a considerable sialic acid fraction was alpha2,3-linked as determined by Streptococcus pneumoniae neuraminidase digestion of the glycopeptides. In the seminal plasma PSA, high-mannose and hybrid types of oligosaccharides were predominant, and the sialic acids attached to the latter as well as to biantennary oligosaccahrides were exclusively alpha2,6-linked because they were removed by Arthrobacter ureafaciens neuraminidase but resistant to S. pneumoniae neuraminidase. Complex-type oligosaccharides from other sources were found in the seminal plasma sample, indicating that analysis of released glycans carries a risk of being misleading. The results suggest that identification of alpha2,3-linked sialic acids on PSA potentially discriminates malignant from benign conditions, if the analysis is applied to oligosaccharides specifically attached to the N-glycosylation site of PSA in either a free or a complexed form in the serum.     

Selective recognition of enzymatically active prostate-specific antigen (PSA) by anti-PSA monoclonal antibodies

Prostate-specific antigen (PSA) is widely used as a serum marker for the diagnosis of prostate cancer. To evaluate two anti-free PSA monoclonal antibodies (mAbs) as potential tools in new generations of more relevant PSA assays, we report here their properties towards the recognition of specific forms of free PSA in seminal fluids, LNCaP supernatants, 'non-binding' PSA and sera from cancer patients. PSA from these different origins was immunopurified by the two anti-free PSA mAbs (5D3D11 and 6C8D8) as well as by an anti-total PSA mAb. The composition of the different immunopurified PSA fractions was analysed and their respective enzymatic activities were determined. In seminal fluid, enzymatically active PSA was equally purified with the three mAbs. In LNCaP supernatants and human sera, 5D3D11 immunopurified active PSA mainly, whereas 6C8D8 immunopurified PSA with residual activity. In sera of prostate cancer patients, we identified the presence of a mature inactive PSA form which can be activated into active PSA by use of high saline concentration or capture by an anti-total PSA mAb capable of enhancing PSA activity. According to PSA models built by comparative modelling with the crystal structure of horse prostate kallikrein described previously, we assume that active and activable PSA could correspond to mature intact PSA with open and closed conformations of the kallikrein loop. The specificity of 5D3D11 was restricted to both active and activable PSA, whereas 6C8D8 recognized all free PSA including intact PSA, proforms and internally cleaved PSA.     

Carbohydrate structure and differential binding of prostate specific antigen to Maackia amurensis lectin between prostate cancer and benign prostate hypertrophy

Serum prostate-specific antigen (PSA) assay is widely used for detection of prostate cancer. Because PSA is also synthesized from normal prostate, false positive diagnosis cannot be avoided by the conventional serum PSA test. To apply the cancer-associated carbohydrate alteration to the improvement of PSA assay, we first elucidated the structures of PSA purified from human seminal fluid. The predominant core structure of N-glycans of seminal fluid PSA was a complex type biantennary oligosaccharide and was consistent with the structure reported previously. However, we found the sialic acid alpha2-3 galactose linkage as an additional terminal carbohydrate structure on seminal fluid PSA. We then analyzed the carbohydrate moiety of serum PSA from the patients with prostate cancer and benign prostate hypertrophy using lectin affinity chromatography. Lectin binding was assessed by lectin affinity column chromatography followed by determining the amount of total and free PSA. Concanavalin A, Lens culinaris, Aleuria aurantia, Sambucus nigra, and Maackia amurensis lectins were tested for their binding to the carbohydrates on PSA. Among the lectins examined, the M. amurensis agglutinin-bound fraction of free serum PSA is increased in prostate cancer patients compared to benign prostate hypertrophy patients. The binding of PSA to M. amurensis agglutinin, which recognizes alpha2,3-linked sialic acid, was also confirmed by surface plasmon resonance analysis. These results suggest that the differential binding of free serum PSA to M. amurensis agglutinin lectin between prostate cancer and benign prostate hypertrophy could be a potential measure for diagnosis of prostate cancer.     

Combined hypermethylation of APC and GSTP1 as a molecular marker for prostate cancer: quantitative pyrosequencing analysis

A total of 149 human prostate tissues obtained from our institute were assessed: 52 specimens of benign prostate hyperplasia (BPH) and 97 specimens of prostate cancer (PCa). The methylation status of the genes of Adenomatous polyposis coli (APC) and glutathione-S-transferase-P1 (GSTP1) was analyzed by quantitative pyrosequencing. A methylation score (M score) was calculated to capture the combined methylation level of both genes. The methylation level of each single gene and that of both genes combined was significantly higher in PCa specimens than in BPH (each p < 0.001). The value of APC methylation, GSTP1 methylation, and M score for predicting PCa was measured by the area under the receiver operating characteristic (ROC) curve and reached 0.954, 0.942, and 0.983, respectively. The sensitivity and specificity of the M score in discriminating between PCa and BPH reached 92.8% and 100.0%, respectively. The M score was positively associated with the serum prostate-specific antigen (PSA) level (p trend < 0.001). Our study demonstrates that the quantitative measurement of two methylation markers might drastically improve the ability to discriminate PCa from BPH.     

Prostate-specific antigen and 17-hydroxylase polymorphic genotypes in patients with prostate cancer and benign prostatic hyperplasia

We investigated the association of prostate cancer (PCa) and benign prostatic hyperplasia (BPH) with genetic polymorphisms in prostate-specific antigen (PSA) (-158 G/A) and 17-hydroxylase (CYP17) (-34 T/C) genes in a Turkish population. In this study, we investigated the distribution of these polymorphisms in 148 PCa patients, 136 BPH patients, and 102 healthy individuals as controls. The polymorphisms were analyzed using polymerase chain reaction-restriction fragment length polymorphism assay. Genotype and allele frequencies were calculated, and their associations with PCa or BPH risk are assayed. The frequency of PSA gene GA and GG genotypes was significantly higher in PCa patients than in controls (p = 0.017 and p = 0.019, respectively). GG genotype was also associated with BPH (p = 0.033). In a case analysis, according to Gleason score, the association of PSA gene GG genotype with Gleason score >7 was near to statistical significance (odds ratio, 2.94; 95% confidence interval, 0.95-9.28). There was also an association between CYP17 polymorphism and BPH (p = 0.004). No association was observed between PCa and CYP17 gene polymorphism. These data demonstrate that PSA gene promoter variation may play a significant role in the development of PCa and BPH, and that CYP17 gene polymorphism may be associated with BPH in the Turkish population studied.     

Malondialdehyde in benign prostate hypertrophy: a useful marker?

Benign prostate hypertrophy (BPH) is the most common benign tumor in men due to obstruction of the urethra and, finally, uremia. Malondialdehyde (MDA) is a product derived from peroxidation of polyunsaturated fatty acids and related esters. Evaluation of MDA in serum represents a non-invasive biomarker of oxidative stress. Prostate-specific antigen (PSA) is a sensitive marker for prostatic hypertrophy and cancer. We analyzed MDA serum levels to evaluate the oxidative stress in BPH. To this end, 22 BPH patients and 22 healthy donors were enrolled. Data show an increase of MDA level in BPH patients and a positive correlation between PSA and MDA levels. In conclusion, we describe a previously unknown relationship between PSA and MDA as an index of inflammation and oxidative stress in BPH.     

PSA在前列腺增生和前列腺癌中的诊断价值

目的：探讨临床上检测前列腺特异性抗原（PSA）的变化情况对前列腺增生和前列腺癌等疾病的诊断价值。方法：采用回顾性分析的方法,选取2010年6月至2012年4月在我院泌尿科接受治疗的前列腺增生患者64例定义为前列腺增生组（BPH）,前列腺癌患者83例定义为前列腺癌组（PCa）,另选取同期接受体检的健康人群137例作为对照组。分别检测三组患者入院时的游离前列腺特异性抗原和总前列腺特异性抗原的水平变化情况。对比并分析三组检测结果。结果：经检测,前列腺增生患者的血清总PSA明显高于对照组健康人群的正常值,而前列腺癌患者的血清总PSA比前列腺增生患者增高的更为明显。对照组游离PSA为（2．78±0．94）ng／mL,总PSA（1．05±0．57）ng／mL,游离PSA与总PSA的比值为,（0．38±0．61）;前列腺增生患者游离PSA为（6．36＋3．24）ng／mL,总PSA为（1．64±0．76）ng／mL,游离PSA与总PSA的比值为（0．26±0．23）;前列腺癌患者游离PSA为（12．42±4．97）ng／mL,总PSA为（1．44±0．78）ng／mL,游离PSA与总PSA的比值为（0．12±0．16）。组间比较差异明显,具有统计学意义（P〈0．05）。结论：对患者的PSA进行检测,对前列腺增生和前列腺癌的诊断具有良好的辅助作用和,临床价值。     

前列腺PI-RADS V2.1评分联合血清PSA相关指标对灰区前列腺癌的诊断价值研究

摘要 目的：探讨前列腺影像报告和数据系统第2.1版（PI-RADS V2.1）评分联合血清前列腺特异抗原（PSA）相关指标对灰区前列腺癌的诊断价值。方法：回顾性分析2016年1月至2019年12月的187例经病理证实且PSA为灰区（4-10 ng/mL）的前列腺癌或前列腺增生患者资料。根据病理结果分为前列腺癌（PCa）组与前列腺增生组（BPH）组。由两名经验丰富的MRI诊断医师通过盲法对所有患者MRI图像进行PI-RADS V2.1评分,统计并计算血清PSA相关指标：总前列腺特异抗原（t-PSA）、游离前列腺特异抗原（f-PSA）、游离前列腺特异抗原与总前列腺特异抗原比值（f-PSA/t-PSA）、前列腺特异抗原密度（PSAD）。采用t检验比较各项指标在两组间的差异性,并使用受试者工作曲线（ROC）分析各项指标对灰区前列腺癌的诊断效能。结果：PI-RADS V2.1评分与PSAD在PCa与BPH组之间的差异具有统计学意义（P＜0.05）,而t-PSA、f-PSA、f-PSA/t-PSA在PCa与BPH组之间的差异均无统计学意义（P＞0.05）。根据ROC曲线分析,PI-RADS V2.1评分、PSAD、PI-RADS V2.1评分联合PSAD诊断灰区前列腺癌的曲线下面积（AUC）分别为0.814、0.671及0.838,且PI-RADS V2.1评分联合PSAD的AUC显著高于单独应用PI-RADS V2.1评分（Z=1.989,P＜0.05）与PSAD（Z=3.174,P＜0.05）。结论：PI-RADS V2.1评分与PSAD对诊断灰区前列腺癌具有较高诊断效能,且联合PI-RADS V2.1评分与PSAD能进一步提高诊断效能。     

White button mushroom (Agaricus bisporus) disrupts androgen receptor signaling in human prostate cancer cells and patient-derived xenograft

White button mushroom (WBM) (Agaricus bisporus) is a potential prostate cancer (PCa) chemo-preventative and therapeutic agent. Our clinical phase І trial of WBM powder in patients with biochemically recurrent PCa indicated that WBM intake reduced the circulating levels of prostate-specific antigen (PSA). We hypothesized that WBM exerts its effects on PCa through the androgen receptor (AR) signaling axis. Therefore, we conducted a reverse translational study with androgen-dependent PCa cell lines (LNCaP and VCaP) and patient-derived-xenografts (PDX) from a prostate tumor (TM00298). In both LNCaP and VCaP cells, western blots and qRT-PCR assays indicated that WBM extract (6–30 mg/mL) suppressed DHT-induced PSA expression and cell proliferation in a dose-dependent manner. Immunofluorescence analysis of AR revealed that WBM extract interrupted the AR nuclear-cytoplasmic distribution. PSA promotor-luciferase assay suggested that WBM extract inhibited DHT-induced luciferase activity. RNA-Seq on WBM-treated LNCaP cells confirmed that WBM treatment suppressed the androgen response pathways and cell-cycle control pathways. Our PDX showed that oral intake of WBM extract (200 mg/kg/d) suppressed tumor growth and decreased PSA levels in both tumors and serum. In the present study, we also identified a conjugated linoleic acid isomer (CLA-9Z11E) as a strong AR antagonist by performing LanthaScreen TR-FRET AR Coactivator Interaction Assays. The inhibitory effect of CLA-9Z11E (IC50: 350 nM) was nearly two times stronger than the known AR antagonist, cyproterone acetate (IC50: 672 nM). The information gained from this study improves the overall understanding of how WBM may contribute to the prevention and treatment of PCa.     

Frequent 14-3-3 sigma promoter methylation in benign and malignant prostate lesions

14-3-3Sigma is a putative tumor suppressor gene involved in cell cycle regulation and apoptosis following DNA damage. 14-3-3Sigma loss of expression has been reported is several human cancers, including prostate adenocarcinoma and precursor lesions, and promoter hypermethylation has been proposed as the mechanism underlying gene silencing. Here, we investigate the frequency and extent of 14-3-3sigma promoter methylation in benign and cancerous prostate tissues. We examined tumor tissue from 121 patients with prostate carcinoma (PCa), 39 paired high-grade prostatic intraepithelial neoplasias (HGPIN), 29 patients with benign prostate hyperplasia (BPH), as well as four prostate cancer cell lines using quantitative methylation-specific PCR (QMSP). The percentage of methylated alleles (PMA) was calculated and correlated with clinical and pathological parameters. RT-PCR was performed in the cell lines to assess 14-3-3sigma mRNA expression. PCa, HGPIN, BPH, and cancer cell lines showed ubiquitous 14-3-3sigma promoter methylation. However, the PMA of HGPIN was significantly lower than that of PCa or BPH (P < 0.0001), while PCa and BPH did not significantly differ. The PMA did not correlate with any clinicopathological parameter. All prostate cancer cell lines expressed 14-3-3sigmamRNA. 14-3-3Sigma promoter methylation is a frequent event in prostate tissues and cancer cell lines. Furthermore, there is a progressive accumulation of neoplastic cells with 14-3-3sigma methylated alleles from HGPIN to PCa, suggesting a role for this epigenetic event in prostate carcinogenesis. However, other mechanisms besides promoter methylation might be required for effective 14-3-3sigma downregulation.     

Serum vascular endothelial growth factor C level in patients with prostate cancer and benign prostatic hyperplasia

OBJECTIVE: To compare serum vascular endothelial growth factor C (VEGF-C) levels in patients with benign prostatic hyperplasia (BPH) and prostate cancer (PCa) and analyze VEGF-C levels in relation to clinicopathologic parameters. STUDY DESIGN: Fifty-eight patients with PCa and 61 patients with BPH were included in this study. Serum VEGF-C levels were assessed by enzyme-linked immunosorbent assay. RESULTS: The serum VEGF-C level for patients with PCa was 3,432.06 +/- 1,851.07 as opposed to 3,166.68 +/- 1,921.2 for patients with BPH. There was no statistically significant difference between the 2 groups (p = 0.4448). There was no correlation of VEGF-C to tumor stage, grading or the preoperative prostate-specific antigen values. CONCLUSION: We cannot recommend VEGF-C serum level as a marker for tumor growth in PCa.     

Androgen receptor signaling is required for androgen-sensitive human prostate cancer cell proliferation and survival

Background  

Androgens and androgen receptors (AR) regulate normal prostate development and growth. They also are involved in pathological development of prostatic diseases, including benign prostatic hyperplasia (BPH) and prostate cancer (PCa). Antiandrogen therapy for PCa, in conjunction with chemical or surgical castration, offers initial positive responses and leads to massive prostate cell death. However, cancer cells later appear as androgen-independent PCa. To investigate the role of AR in prostate cell proliferation and survival, we introduced a vector-based small interfering RNA (siRNA). This siRNA targeted 5'-untranslated region of AR mRNA for extended suppression of AR expression in androgen-sensitive human prostate LNCaP cells.     

The study of DJ-1 protein in tissue specimens,cultured cells and serum of prostate cancer patients

Two electrophoretically distinguishable isoforms of Dj-1 protein have been identified in a proteomic study of tissue specimens obtained from patients with confirmed prostate cancer (PCa) and benign prostatic hyperplasia (BPH). Dj-1 was also found in the cell lines PC-3, DU-145, LNCaP, BPH-1, and the lowest level of Dj-1 was found in BPH-1. An immunochemical study (ELISA) of serum levels of Dj-1, Bcl-2, IGF-1 and IGFBP-3 proteins revealed statistically significant differences between these two groups of patients only for Dj-1 (p = 0.004, the Wilcoxon-Mann-Whitney test). These data suggest that Dj-1 protein is a perspective candidate biomarker for PCa.     

CaT1 expression correlates with tumor grade in prostate cancer

Ca(2+) signaling is important for growth and survival of prostatic carcinoma (PCa) cells. Here we report that the gene for CaT1, a channel protein highly selective for Ca(2+), is expressed at high levels in human PCa and in the LNCaP PCa cell line. CaT1 mRNA levels were elevated in PCa specimens in comparison to benign prostatic hyperplasia (BPH) specimens and positively correlated with Gleason grade in a PCa series. CaT1 mRNA was suppressed by androgen and was induced by a specific androgen receptor antagonist in LNCaP cells, suggesting that the gene is negatively regulated by androgen. These findings are the first to implicate a Ca(2+) channel in PCa progression and suggest that CaT1 may be a novel target for therapy.