Prostate-specific membrane antigen levels in sera from healthy men and patients with benign prostate hyperplasia or prostate cancer.

Prostate-specific membrane antigen (PSMA) serum levels have been proposed to be of prognostic significance in patients with advanced prostate disease. The objective of the present study was to confirm PSMA serum expression by Western blot techniques, to determine whether such data could assist in the differentiation of benign from malignant prostatic disease, and to determine the suitability of serum PSMA measurements in predicting recurrent or progressive prostate malignancies. We measured PSMA, a transmembrane glycoprotein identified in prostate epithelial cells, in the sera of 236 normal individuals and cancer patients by Western blot analysis. Within the normal male population, PSMA levels increase with age and were found to be significantly elevated in subjects more than 50 years of age when compared to those of younger men. We did not confirm previous reports that serum PSMA measurements could distinguish late-stage prostate carcinoma from early-stage prostate carcinoma, nor did we find PSMA to be more effective than prostate-specific antigen in monitoring prostate cancer patient prognosis. Furthermore, we found elevated serum PSMA in healthy females, and, similar to the healthy male population, the levels increased with age, with the highest levels found in the sera from breast cancer patients. These latter observations further support that PSMA is not a specific biomarker for prostate cancer and that a variety of normal and diseased tissue may contribute to the serum levels of PSMA.     

Correlation of primary tumor prostate-specific membrane antigen expression with disease recurrence in prostate cancer.

PURPOSE: The restricted expression of the surface glycoprotein prostrate-specific membrane antigen (PSMA) to normal prostate tissue, primary and metastatic prostate cancer (PCa), and the neovasculature of various nonprostatic epithelial malignancies has enabled targeting strategies for PCa treatment using anti-PSMA antibodies. EXPERIMENTAL DESIGN: Using prostatectomy specimens, immunohistochemical staining for PSMA (7E11 antibody) was performed on formalin-fixed paraffin-embedded sections of 136 cases of PCa. Cytoplasmic immunoreactivity was scored for intensity and distribution, and results were correlated with tumor grade, pathological stage, DNA ploidy status (Feulgen spectroscopy), and disease recurrence. PSMA mRNA expression in selected primary tumors and metastatic lesions was also detected using in situ hybridization and autoradiography. RESULTS: Generally, PCa cells expressed relatively increased levels of PSMA as compared with benign elements. Among the PCa cases, increased (high) PSMA expression correlated with tumor grade (P = 0.030), pathological stage (P = 0.029), aneuploidy (P = 0.010), and biochemical recurrence (P = 0.001). The mean serum prostate-specific antigen level of 18.28 ng/ml at the time of diagnosis for the PSMA-overexpressing tumors was significantly greater than the mean serum prostate-specific antigen of 9.10 ng/ml for the non-PMSA-overexpressing group (P = 0.006). On multivariate analysis, pathological stage (P = 0.018) and PSMA expression (P = 0.002) were independent predictors of biochemical recurrence. PSMA protein overexpression in high-grade primary PCa tumors and metastatic lesions also correlated with increased PSMA mRNA expression levels using in situ hybridization and autoradiography. CONCLUSIONS: This study demonstrates for the first time that overexpression of PSMA in primary PCa correlates with other adverse traditional prognostic factors and independently predicts disease outcome.     

Quantitation of serum prostate-specific membrane antigen by a novel protein biochip immunoassay discriminates benign from malignant prostate disease

The lack of a sensitive immunoassay for quantitating serum prostate-specific membrane antigen (PSMA) hinders its clinical utility as a diagnostic/prognostic biomarker. An innovative protein biochip immunoassay was used to quantitate and compare serum PSMA levels in healthy men and patients with either benign or malignant prostate disease. PSMA was captured from serum by anti-PSMA antibody bound to ProteinChip arrays, the captured PSMA detected by surface-enhanced laser desorption/ionization mass spectrometry, and quantitated by comparing the mass signal integrals to a standard curve established using purified recombinant PSMA. The average serum PSMA value for prostate cancer (623.1 ng/ml) was significantly different (P < 0.001) from that for benign prostate hyperplasia (117.1 ng/ml) and the normal groups (age <50, 272.9 ng/ml; age >50, 359.4 ng/ml). These initial results suggest that serum PSMA may be a more effective biomarker than prostate-specific antigen for differentiating benign from malignant prostate disease and warrants additional evaluation of the surface-enhanced laser desorption/ionization PSMA immunoassay to determine its diagnostic utility.     

Abnormal E-cadherin expression and prostate cell blood dissemination as markers of biological recurrence in cancer

Until now, no molecular parameter has been available for predicting the metastatic potential of prostate tumours, which leaves their outcome uncertain despite an apparent benign histology or early stage. Abnormal expression of adhesion molecules, such as E-cadherin, can be contributing factors for increased invasiveness and metastatic potential. Histological analysis for E-cadherin expression was carried out on paraffin-embedded tumour tissues. Tumour metastatic potential was indirectly evaluated by detecting circulating prostate cells (CPC), using reverse transciptase-polymerase chain reaction (RT-PCR) and prostate-specific membrane antigen (PSMA) as a target. Patients were followed-up for a median of 14 months (range 10--19 months) after surgery with serum prostate-specific antigen (PSA) level measurement. Interestingly, 23 of 44 localised tumours exhibited aberrant E-cadherin expression. Prior to primary surgery, PSMA RT-PCR detected the spread of prostate cells to the blood in 24 patients. Statistical analysis showed that abnormal E-cadherin expression in the tumours was the only variable that was independently correlated with prostate cell dissemination in the blood (P<0.0001). In logistic regression analysis, abnormal E-cadherin expression was a significant independent predictor for a later biological relapse. This impaired adhesion status was clearly correlated with a haematogenous spread of the primary tumour cells. It could therefore be an objective way to restrict the indications for radical surgery to patients not presenting with this feature.     

Effect of exogenous testosterone replacement on prostate-specific antigen and prostate-specific membrane antigen levels in hypogonadal men

Previous studies have suggested that serum prostate-specific antigen (PSA) levels are under androgenic influence, especially in patients with adenocarcinoma of the prostate. PSMA (prostate-specific membrane antigen) is thought to reflect hormonal or clonal resistance or an independence with respect to testosterone regulation. The influence of testosterone on serum PSA expression in normal men is not clear. We studied the effect of exogenous testosterone administration on the serum levels of PSA and PSMA in hypogonadal men. Serial serum PSA, serum PSMA by Western blot, and serum total testosterone levels were obtained at intervals of every 2–4 weeks in 10 hypogonadal men undergoing treatment with exogenous testosterone, delivered as testosterone enanthate injection or by testosterone patch. Linear and quadratic orthogonal polynomial scores were calculated for PSMA, PSA, and testosterone. A 2-tailed, paired t-test failed to demonstrate a significant correlation between serum PSA (linear P = 0.432, quadratic P = 0.290) or PSMA (linear P = 0.162, quadratic P = 0.973) and serum testosterone levels. This study suggests that in hypogonadal men, neither PSMA nor PSA expression is testosterone-dependent.     

前列腺特异性膜抗原和前列腺特异性抗原表达强度与前列腺癌Gleason评分之间的相关性研究

目的研究前列腺特异性膜抗原(PSMA)和前列腺特异性抗原(PSA)的表达强度与前列腺癌Gleason评分之间的相关性。方法制备抗PSMA膜外段表位的单克隆抗体,应用免疫组织化学方法检测前列腺癌中PSMA的表达,统计分析其与Gleason评分之间的相关性,并和PSA与Gleason评分之间的相关性进行对比。结果制备出8株分泌抗PSMA膜外段表位的单抗的杂交瘤细胞株。免疫组化结果表明,PSMA的表达强度与前列腺癌的Gleason评分之间存在相关性。在分化差的前列腺癌中,PSMA水平高于分化中等和分化良好的前列腺癌(P<0.01),而PSA在前列腺癌中的表达无明显差异(P>0.05)。结论PSMA表达水平在分化差的前列腺癌中明显升高,与Gleason评分存在相关性,可以作为前列腺癌的Gleason分级的标记物,提示PSMA可以作为对激素疗法效果不敏感的低分化前列腺癌抗体介导的免疫治疗靶点。     

前列腺特异膜抗原对前列腺疾病的临床诊断意义

目的评价血清中前列腺特异膜抗原（PSMA）浓度对前列腺疾病的辅助诊断意义。方法采用Western印迹分析检测患者血清中PSMA的浓度,前列腺特异抗原（PSA）检测采用通用的免疫化学发光法检测。分析二者在不同分组中的浓度差异及相关性。结果前列腺癌患者的血清中PSMA浓度显著高于正常人群,良性前列腺增生和前列腺炎的患者则低于正常人群,而PSA浓度无论是前列腺癌还是前列腺良性病变均高于正常人。结论前列腺特异膜抗原浓度可以作为区分前列腺癌和良性前列腺增生的辅助诊断标志物。     

人PSMA基因重组腺病毒的构建及其在树突状细胞上的表达

  目的   构建含有人前列腺特异性膜抗原基因（prostate specific membrane antigen,PSMA）的重组腺病毒,并将其感染树突状细胞（dendritic cell,DC）后检测其在DC上的表达。   方法   设计一对含有SfiⅠ酶切位点的PSMA基因上下游引物,以质粒pCMV-SPORT6/PSMA为模板,通过PCR扩增获得PSMA基因序列。片段回收、酶切处理,连接到穿梭质粒pShuttle-CMV-EGFP上,获得重组穿梭质粒pShuttle-EGFP-PSMA。经SfiⅠ酶切、PCR及插入片段测序鉴定正确后,将其用I-CeuI和I-SceI双酶切处理,转移至pAdxsi载体上,得到pAdxsi-GFP-PSMA病毒质粒,线性化后经HEK293细胞包装成复制缺陷型腺病毒Ad-PSMA-GFP;感染从健康志愿者外周血来源的DC,荧光倒置显微镜下观察绿色荧光蛋白（GFP）的表达,Western blot检测PSMA基因在DC上的表达。   结果   成功构建含有人PSMA基因的重组腺病毒,病毒滴度为2×1010 pfu/mL。构建好的Ad-PSMA-GFP可以在DC上高效和正确地表达。   结论   人PSMA重组腺病毒载体的成功构建及其在DC上的表达,为下一步研究奠定了基础。      

前列腺特异性膜抗原在前列腺癌患者外周血和组织中的表达及意义

目的探讨前列腺特异性膜抗原（PSMA）在前列腺癌患者（PCa）外周血和组织中的表达及其与肿瘤病理分级和临床分期之间的关系。方法采用RT-PCR方法检测前列腺特异性膜抗原（PSMA）在前列腺癌和良性增生患者外周血清中的表达;采用免疫组化法观察PSMA在前列腺不同病变组织中的表达。前列腺癌28例,前列腺上皮内瘤（PIN）7例,良性前列腺增生（BPH）30例。结果血清学检测显示PSMA mRNA在前列腺癌和良性病变组（包括PIN和BPH）患者外周血中阳性率分别为67.9%和8.1%,两者差异具有显著性（P〈0.01）。在局限性癌、局部进展性癌和远处转移癌患者外周血肿瘤细胞中,PSMA mRNA的阳性率分别为58.3%、66.7%和85.7%,随前列腺癌临床分期的进展而逐渐递增（P〈0.05）。在高分化、中分化和低分化前列腺癌中,PSMA mRNA的阳性率分别为87.5%、62.5%和50%,肿瘤分化越差,其阳性率越低（P〈0.05）。组织学检测显示PSMA在PCa、PIN、BPH三种不同前列腺病变组织中的阳性率分别为60.7%、28.6%和20.0%（P〈0.05）,在高、中、低分化前列腺癌组织中PSMA的阳性率分别为100.0%、50.0%和25.0%,与肿瘤Gleason评分之间呈负相关（P〈0.05）。在局限性癌、局部进展性癌和远处转移癌患者肿瘤组织中,PSMA的阳性率分别为58.3%（7/12）、77.8%（7/9）和42.9%（3/7）（P〉0.05）。结论PSMA在前列腺癌组织中明显高表达,并且表达量与前列腺癌临床分期和分化程度（组织学分级）密切相关;检测PSMA可能对前列腺癌诊断、治疗方案的选择及预后评估具有重要价值。     

Comparative study of monoclonal antibodies TURP-27 and HNK-1: their relationship to neural cell adhesion molecules and prostate tumor-associated antigens.

The murine monoclonal antibodies TURP-27 and HNK-1 have been shown to detect antigens which are heavily expressed by benign prostatic hyperplasia and carcinoma of the prostate. Western blot analysis of prostate extracts showed that monoclonal antibodies TURP-27 and HNK-1 bound glycoproteins with molecular weights of 180,000, 140,000, 120,000, 100,000, 90,000, and 69,000. Studies have shown that the HNK-1 carbohydrate epitope may be involved in cell adhesion and that it is a component of several characterized adhesion proteins. TURP-27 was found to bind at least three of these adhesion proteins: neural cell adhesion molecules; myelin-associated glycoprotein; and a second myelin glycoprotein, P0. Western blot analysis of prostate extracts showed that an antineural cell adhesion molecule serum bound the Mr 180,000 and 140,000 proteins. Based on reciprocal blocking and chemical tests, it was determined that the TURP-27 and HNK-1 epitopes are not identical. These data imply that the TURP-27 epitope may be a variant of the HNK-1 epitope or that the two epitopes are closely linked and that the TURP-27 and HNK-1 epitopes on prostate cells are positioned on neural cell adhesion molecule-like proteins.     

The role of an 80 kDa fragment of E-cadherin in the metastatic progression of prostate cancer.

PURPOSE: The purpose of this study was to evaluate an 80 kDa proteolytic fragment of E-cadherin as a potential biomarker for prostate cancer progression and to identify putative proteases that are responsible for the cleavage of E-cadherin. EXPERIMENTAL DESIGN: A wide spectrum of prostate cancer tissue and serum specimens representing different stages of prostate cancer was examined for the accumulation of the 80 kDa fragment of E-cadherin. Additionally, an expression array analysis was used to identify putative proteases that may have been involved in the cleavage of E-cadherin. RESULTS: A reproducible E-cadherin fragment was detected as a strong 80 kDa band in tissue samples. This fragment was detectable almost exclusively in metastatic sites. It was not visible in normal prostate tissue and was weak in 1 of 16 localized prostate cancers. The fragment is shed into the extracellular space and was detectable in patient serum in which the expression of the fragment showed a strong association with advanced prostate cancer. On the basis of cDNA expression analysis, several members of the metalloproteinase family could be identified as potentially responsible for the cleavage of the fragment from full-length E-cadherin. CONCLUSIONS: In this study, we present the first report of serum levels of the 80 kDa fragment of E-cadherin in prostate cancer patients. This fragment is exclusively seen in neoplastic prostate tissue and may represent a useful biomarker of prostate cancer disease progression. This study also demonstrates an association of increased levels of several metalloproteinases with metastatic prostate cancer and could provide a useful correlation between metalloproteinase expression/activity and E-cadherin cleavage and the metastatic progression of prostate cancer.     

Preferential association of prostate cancer cells expressing prostate specific membrane antigen to bone marrow matrix

Prostate specific membrane antigen (PSMA) is a transmembrane glycoprotein expressed almost exclusively in prostatic epithelial cells. Expression of PSMA is elevated in prostate cancer, with levels closely correlated with disease grade. Although the highest levels of PSMA expression are associated with high-grade, hormone-refractory and metastatic prostate cancer, the significance of elevated PSMA expression in advanced prostate cancer has yet to be fully elucidated. We provide evidence that prostatic carcinoma cells expressing PSMA exhibit reduced motility and increased attachment when grown on a bone marrow matrix substrate. This phenomenon occurs via activation of focal adhesion kinase and provides the first evidence of a link between PSMA expression and prostate cancer metastasis to the bone.     

Haptoglobin-beta chain defined by monoclonal antibody RM2 as a novel serum marker for prostate cancer

In our previous study, monoclonal antibody RM2, established toward the glycosyl epitope, reflected grade of malignancy of prostate cancer cells whereas RM2 reactivity to benign glands was negative or weak. RM2 reactivity was also detected in stroma, suggesting the glycoprotein RM2 recognizes could be released into the bloodstream. Then, we explored RM2 reactivity to sera of early prostate cancer. We compared RM2 reactivity to sera between 62 patients with early prostate cancer and 43 subjects with benign prostatic disease, and examined RM2 reactivity before and after radical prostatectomy in 15 patients by Western blotting. We also examined RM2 reactivity to sera of the other urogenital cancers. RM2 reactivity was significantly enhanced on a serum glycoprotein with molecular mass approximately 40 kDa, hereby termed GPX, in the patients with early prostate cancer when compared with those with benign prostatic disease (p < 0.0001). Setting an appropriate cutoff level, RM2 reactivity to GPX for detection of prostate cancer had sensitivity of 87% and specificity of 84%, respectively. Furthermore, the level of RM2 reactivity significantly decreased after radical prostatectomy (p = 0.006). However, increased RM2 reactivity to GPX was also observed in the other urogenital cancers. The proteomics approach identified GPX as haptoglobin-beta chain and RM2 showed preferential reactivity toward haptoglobin-beta chain derived from prostate cancer when compared with polyclonal anti-haptoglobin antibody. Haptoglobin-beta chain defined by RM2 is a novel serum marker that may be useful for detection of early prostate cancer when coupled with prostate-specific antigen because it is not specific to prostate cancer.     

Identification of prostate specific membrane antigen (PSMA) as the target of monoclonal antibody 107-1A4 by proteinchip; array, surface-enhanced laser desorption/ionization (SELDI) technology

Recently we described the generation of the prostate tissue-specific monoclonal antibody (MAb) 107-1A4, its expression pattern and preliminary targeting of human prostate cancer xenografts. In this report we demonstrate that the target antigen for MAb 107-1A4 is prostate-specific membrane antigen (PSMA) using immunoaffinity absorption followed by SDS-PAGE and mass spectrometric analysis of peptides produced by in-gel tryptic digestion. The identity of the antigen has been confirmed by Western blots using MAbs of known specificity. MAb 107-1A4 is not reactive on Western blots. The conformational epitope for 107-1A4 is on the extracellular domain of PSMA. In competition studies, the binding of MAb 107-1A4 to LNCaP cells is inhibited by itself but not by any other of several other anti-PSMA MAbs, suggesting that the epitope may be unique. These results suggest that 107-1A4 is reactive to a conformational epitope in the external domain of PSMA that is unique among the panel of anti-PSMA MAbs in this study. Furthermore this work demonstrates the ability of mass spectroscopy to elucidate antibody-ligand interaction.     

Presence and enzymatic activity of prostate-specific antigen in archival prostate cancer samples

Patients with advanced prostate cancer frequently have a poor prognosis as a result of metastasis. The serum prostate-specific antigen (PSA) test is widely used for the diagnosis of prostate cancer. The enzymatic activity of PSA may be involved in the invasion of prostate cancer. We set out to determine the prevalent form of PSA in human prostate adenocarcinoma samples by ELISA and Western blot analysis and its enzymatic activity using a synthetic substrate S-2586 and fibronectin. Our results show that in serum from prostate cancer patients and in tumour homogenates, the prevalent form was PSA bound to alpha1-antichymotrypsin. All homogenates showed enzymatic activity towards a synthetic PSA substrate, whereas only five samples showed activity at 28 kDa towards fibronectin as determined by enzymography, which is most likely due to active PSA. Human prostate cancer LNCaP cells produced largely inactive PSA. In comparison, 22Rv1 cells produced 29-fold less PSA, but with high specific activity. Similarly, our results from the human prostate cancer tissue samples also show that free PSA appears to exist in diverse forms of very different specific activity. Since PSA, as a serine protease, may be involved in the invasion of prostate cancer, our results suggest that prostate cancers have potentially diverse invasive capacity due to differences in specific enzymatic activity of PSA.     

Emerging role of immunotherapy in the management of prostate cancer

There has been a resurgence of interest in developing noncytotoxic immune therapies for patients with either hormone-naive biochemically relapsed post-primary therapy or castrate metastatic prostate cancer. The rationale for developing an immunotherapeutic approach has been based on the overexpression and underglycosylation of a wide variety of altered "self" molecules including prostate-specific antigen (PSA), acid phosphatase (ACP), prostate stem cell antigen (PSCA), and prostate-specific membrane antigen (PSMA), which can serve as targets for immune recognition and attack. In addition, such a strategy could theoretically make use of the patient's immune system to fight the tumor particularly if their disease is of reasonably low volume. A variety of immunotherapeutic approaches have been explored through phase I, II, and now phase III trials demonstrating that immunologic tolerance could be broken, as evidenced by the development of hightiter antibodies and T-cell responses specific for the tumor. What appears to be revolutionizing the immunotherapy field is the combination of vaccines with cytokines or immune modulators, which not only potentiate immune reactivity in vivo but foster dramatic antitumor responses. This review explores the challenges now faced in establishing a role for immune therapies for prostate cancer treatment.