前列腺特异性膜抗原在不同组织中的表达及其意义

目的：观察前列腺特异性膜抗原（PSMA）在前列腺不同病变组织及非前列腺肿瘤组织中的表达情况。从免疫化角度评价PSMA的前列腺组织器官特异性。方法：采用PSMA单克隆抗体，对111例前列腺不同病变组织和30例非前列腺肿瘤组织进行染色。结果：PSMA在绝大多数前列腺组织中存在不同程度的阳性表达，仅2例前列腺癌和4例前列腺良性增隆症呈阴性表达，而全部染色的非前列腺肿瘤组织中PSMA阴性表达。结论：PSMA仅在前列腺组织中表达，且在前列腺癌组织中呈明显高表达，是前列腺器官特异性的新型肿瘤标志物，在前列腺癌的诊断和免疫治疗方面具有良好的应用前景。     

前列腺特异性膜抗原PSMA的研究现状

近年来,前列腺特异性分子标志物——前列腺特异性膜抗原（prostrate specific membrane antigen,PSMA）倍受关注。目前研究报道多关于PSMA与前列腺癌及其相关组织的关系,部分文献报道PSMA与其他肿瘤的关系。本文主要从PSMA的一般情况、其与血管生成的关系以及在良性疾病、恶性肿瘤中的表达情况及诊断治疗进行综述。     

前列腺特异性膜抗原与前列腺癌的关系及其临床应用

前列腺特异性膜抗原(PSMA)是位于前列腺细胞膜上的Ⅱ型跨膜糖蛋白,特异地表达于上皮细胞,在前列腺癌及其转移灶中表达增高,特别是在晚期患者及对激素治疗不敏感的患者中其表达升高尤为明显.因此可作为靶蛋白,在前列腺癌的早期诊断、判断病情进展及预后,以及在前列腺癌的靶向治疗中具有重大意义.     

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。     

功能化PSMA在前列腺癌核素靶向治疗中的研究进展

前列腺癌（PCa）是男性生殖系统发病率最高的恶性肿瘤。研究证实，前列腺特异性膜抗原（PSMA）是一种有效的前列腺癌诊疗靶点。治疗核素177Lu/90Y标记的抗PSMA小分子/多肽/单抗表现出重要的抑癌活性，但也产生腺体、骨髓的特异性摄取和肾脏的非特异性摄取带来的正常器官损伤。而且小分子/多肽易于经循环系统清除，基于小分子/多肽的放射性靶向治疗往往需要较高剂量或频繁给药，导致在抑制肿瘤的同时，也产生难以预料的器官毒性。放射性核素靶向治疗依赖于将放射性核素传递到肿瘤表达的受体，但配体与受体结合容量有限。为提高核素的使用效率，延长核素治疗型PSMA分子探针的体内代谢，增加靶/非靶比值，对PSMA分子探针进行功能化修饰以期改善药代动力学行为的研究已经取得了巨大进展。本文就近年功能化PSMA分子探针在前列腺癌核素靶向治疗中的临床转化及临床研究展开综述。     

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。     

前列腺特异性膜抗原与前列腺癌的关系及其临床应用

前列腺特异性膜抗原（PSMA）是位于前列膛细胞膜上的II型跨膜糖蛋白，特异地表达于上皮细胞，在前列腺癌及其转移灶中表达增高，特别是在晚期患者及对激治疗不敏感的患者中其表达升高尤为明显，因此可作靶蛋白，在前列腺癌的早期诊断，判断病情进展及预后，以及在前列腺癌的靶向治疗中具有有重大意义。     

前列腺特异性抗原人类激肽释放酶2和前列腺特异的膜抗原在前列腺癌患者外周血表达的临床意义

目的　探讨检测前列腺癌微转移的灵敏和特异性指标。方法　从 5 1例前列腺癌、33例前列腺增生 (BPH)患者及 32名正常人的外周血中分离单个核细胞 ,用巢式RT PCR方法检测其中前列腺上皮细胞前列腺特异性抗原 (PSA)、人类激肽释放酶 2 (hK2 )和前列腺特异的膜抗原 (PSMA)的表达。结果　PSA、hK2和PSMA在前列腺癌患者外周血中检出的阳性率分别为 5 2 .9%、4 3.1%和6 4 .7% ;正常人和BPH患者假阳性率分别为 6 .2 %、7.7%和 4 .6 % ,3项指标差异均有显著性 (P <0 .0 1)。各临床分期 (局限癌、侵袭性癌和转移癌 )间 ,PSA和hK2的阳性检出率差异无显著性 ;PSMA在各期前列腺癌中阳性检出率均较PSA和hK2高 ,且随临床分期进展 ,其阳性检出率亦增加 (P <0 .0 5 )。结论PSMA对前列腺癌诊断、治疗方案的选择及预后评估较PSA和hK2有更大的价值     

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。     

前列腺特异性抗原的临床应用

前列腺特异性抗原(PSA)是前列腺上皮细胞的分泌产物,可以迅速水解射精后产生的精液凝块.自1979年Wang等用免疫沉淀法提纯PSA后,PSA得到深入研究和广泛应用,成为肿瘤学和肿瘤标志物研究领域的重大进展,是前列腺癌(CAP)诊断,治疗和随访中最有价值的肿瘤标志物.本文介绍PSA在临床应用的现状.1.血清PSA的正常值瘤标的正常值是在健康人群中测定得到的.PSA是前列腺组织的特异性产物,前列腺感染疾病     

Prostate-specific membrane antigen-targeted photodynamic therapy induces rapid cytoskeletal disruption

Prostate-specific membrane antigen (PSMA), an established enzyme–biomarker for prostate cancer, has attracted considerable attention as a target for imaging and therapeutic applications. We aimed to determine the effects of PSMA-targeted photodynamic therapy (PDT) on cytoskeletal networks in prostate cancer cells. PSMA-targeted PDT resulted in rapid disruption of microtubules (α-/β-tubulin), microfilaments (actin), and intermediate filaments (cytokeratin 8/18) in the cytoplasm of LNCaP cells. The collapse of cytoplasmic microtubules and the later nuclear translocation of α-/β-tubulin were the most dramatic alternation. It is likely that these early changes of cytoskeletal networks are partly involved in the initiation of cell death.     

Prostate-specific Membrane Antigen (PSMA)-specific Monoclonal Antibodies in the Treatment of Prostate and Other Cancers

Prostate-specific membrane antigen (PSMA) is a cell surface glycoprotein that is expressed by prostate epithelial cells. PSMA-specific monoclonal antibodies have been utilized to characterize the biologic function and in vivo biodistribution of PSMA. PSMA is an attractive target protein for monoclonal antibody directed imaging or therapeutics for prostate cancer since its expression is relatively restricted to prostate epithelial cells and is over-expressed in prostate cancer, including in advanced stages. Currently, clinical usage of PSMA specific monoclonal antibodies has been limited to diagnostic immunohistochemistry and imaging of patients with prostate cancer. Novel applications for these antibodies will be discussed.     

Heterogeneity of Prostate-Specific Membrane Antigen (PSMA) Expression in Prostate Carcinoma with Distant Metastasis

Prostate-specific membrane antigen (PSMA) is a transmembrane protein that is overexpressed in advanced stage prostate adenocarcinomas. As a novel target for in vivo prognostic and therapeutic approaches, the distribution pattern of PSMA in primary and metastatic tumors is of significant interest. In this study we addressed the cellular distribution and heterogeneity of PSMA expression. Paraffin-embedded sections of 51 patients with primary prostate carcinoma and distant metastases were evaluated. Immunohistochemistry was used to determine the cellular localization, staining intensity and positive cell fraction which were related to tumor type and growth pattern. We demonstrated differences in the intracellular localization of the PSMA immunostaining which seem to be related to the tumor differentiation pattern. A significant number of the primary tumors (7/51) and metastases (6/51) presented with highly heterogeneous PSMA expression and in further 2 primary, and 8 metastatic tumors the staining was in the negative range (<10% positive tumor cells). A direct correlation between histological parameters and PSMA expression could not be demonstrated. Our findings clearly support the feasibility but also direct to potential failures of PSMA-targeted in vivo diagnostic and therapeutic approaches in prostate cancer patients with distant metastasis.     

Targeted elimination of prostate cancer by genetically directed human T lymphocytes

The genetic transfer of antigen receptors is a powerful approach to rapidly generate tumor-specific T lymphocytes. Unlike the physiologic T-cell receptor, chimeric antigen receptors (CARs) encompass immunoglobulin variable regions or receptor ligands as their antigen recognition moiety, thus permitting T cells to recognize tumor antigens in the absence of human leukocyte antigen expression. CARs encompassing the CD3zeta chain as their activating domain induce T-cell proliferation in vitro, but limited survival. The requirements for genetically targeted T cells to function in vivo are less well understood. We have, therefore, established animal models to assess the therapeutic efficacy of human peripheral blood T lymphocytes targeted to prostate-specific membrane antigen (PSMA), an antigen expressed in prostate cancer cells and the neovasculature of various solid tumors. In vivo specificity and antitumor activity were assessed in mice bearing established prostate adenocarcinomas, using serum prostate-secreted antigen, magnetic resonance, computed tomography, and bioluminescence imaging to investigate the response to therapy. In three tumor models, orthotopic, s.c., and pulmonary, we show that PSMA-targeted T cells effectively eliminate prostate cancer. Tumor eradication was directly proportional to the in vivo effector-to-tumor cell ratio. Serial imaging further reveals that the T cells must survive for at least 1 week to induce durable remissions. The eradication of xenogeneic tumors in a murine environment shows that the adoptively transferred T cells do not absolutely require in vivo costimulation to function. These results thus provide a strong rationale for undertaking phase I clinical studies to assess PSMA-targeted T cells in patients with metastatic prostate cancer.     

Combination of the PI3K Inhibitor ZSTK474 with a PSMA-Targeted Immunotoxin Accelerates Apoptosis and Regression of Prostate Cancer

The phosphoinositide 3-kinase (PI3K) pathway is activated in most advanced prostate cancers, yet so far treatments with PI3K inhibitors have been at best tumorostatic in preclinical cancer models and do not show significant antitumor efficacy in clinical trials. Results from tissue culture experiments in prostate cancer cells suggest that PI3K inhibitors should be combined with other cytotoxic agents; however, the general toxicity of such combinations prevents translating these experimental data into preclinical and clinical models. We investigated the emerging concept of tumor-targeted synthetic lethality in prostate cancer cells by using the pan-PI3K inhibitor ZSTK474 and the immunotoxin J591PE, a protein chimera between the single-chain variable fragment of the monoclonal antibody J591 against the prostate-specific membrane antigen (PSMA) and the truncated form of the Pseudomonas aeruginosa exotoxin A (PE38QQR). The combination of ZSTK474 and J591PE increased apoptosis within 6 hours and cell death (monitored at 24–48 hours) in the PSMA-expressing cells LNCaP, C4-2, and C4-2Luc but not in control cells that do not express PSMA (PC3 and BT549 cells). Mechanistic analysis suggested that induction of apoptosis requires Bcl-2-associated death promoter (BAD) dephosphorylation and decreased expression of myeloid leukemia cell differentiation protein 1 (MCL-1). A single injection of ZSTK474 and J591PE into engrafted prostate cancer C4-2Luc cells led to consistent and stable reduction of luminescence within 6 days. These results suggest that the combination of a PI3K inhibitor and a PSMA-targeted protein synthesis inhibitor toxin represents a promising novel strategy for advanced prostate cancer therapy that should be further investigated.     

Identification of MHC class II-restricted T-cell epitopes in prostate-specific membrane antigen.

An effective tumor vaccine may be required to induce both CTLs and T-helper (Th) responses against tumor-associated antigens. CD4+ Th cells that recognize MHC class II-restricted epitopes play a central role in the initiation and maintenance of antitumor immune responses. Prostate-specific membrane antigen (PSMA) is highly expressed in prostate cancer and thus is a potential target for prostate cancer immunotherapy. In this study, we attempted to identify Th epitopes derived from PSMA for enhancing prostate cancer vaccine by eliciting PSMA-specific Th responses. We first screened a panel of six epitope peptide candidates selected with the TEPITOPE program and found that all six peptides induced peptide-specific T-cell proliferation from one or more donors with estimated T-cell precursor frequencies of 0-4.17 x 10(-6). We then established peptide-specific T-cell clones for five of these six peptides and demonstrated that the T-cell clone specific for the PSMA(459) epitope (NYTLRVDCTPLMYSL) can recognize processed antigens from recombinant PSMA proteins. The PSMA(459) peptide was found to induce CD4+ T-cell responses in healthy individuals and prostate cancer patients with different HLA-DR alleles. To test the potential clinical application, human HLA-DR4 transgenic mice were immunized with PSMA(459) peptide and we found that PSMA(459) peptide immunization activated T cells that specifically responded to antigenic peptides derived from PSMA proteins and PSMA-positive tumor. Thus, the naturally processed Th epitope PSMA(459) could be included in prostate tumor vaccines to enhance PSMA-specific CTL responses.     

Expression of prostate specific membrane antigen and three alternatively spliced variants of PSMA in prostate cancer patients

Prostate specific membrane antigen (PSMA) is a folate gamma glutamyl carboxypeptidase that is oriented on the plasma membrane of normal and prostate cancer cells. A cytosolic version of PSMA, PSM', results from alternative splicing of the PSMA gene. Two additional alternatively spliced variants of PSMA, PSM-C and PSM-D, have been described recently. The ratio of PSMA to PSM' mRNA was higher in a small number of prostate cancer specimens compared to normal prostate cancer and benign prostatic hypertrophy (Su et al. Cancer Res 1995;55:1441). The intent of our study was to measure the gene expression of PSMA and the 3 PSMA splice variants in a large number of patient's tissues. A real-time, quantitative PCR assay was developed to quantify PSMA, PSM', PSM-C and PSM-D. Discrimination among the variants was achieved by designing unique primers and TaqMan probes for each gene. Amplification and detection was specific for the desired splice variant and was sensitive to one gene copy per reaction. The assay was used to quantify the gene expression in specimens of normal, benign, primary and metastatic prostate cancer from 72 patients. The mean PSMA expression (relative to 18S rRNA) was 2- to 3-fold lower in normal prostate (n = 4) compared to primary (n = 55, p = 0.31) and metastatic (n = 20, p = 0.33) prostate cancer. There was no difference in the PSMA expression between benign and cancerous prostate tissue from the same patients (n = 35). The ratio of PSMA to PSM' was lowest in the normal prostate and increased with increasing Gleason score (p < 0.001). The increased ratio in these tissues was a reflection of both increasing PSMA levels and decreasing PSM' mRNA. The expression of PSM-C did not differ in any of the tissue categories studied. The expression of PSM-D was similar in normal and primary prostate cancer but was 2-fold higher in lymph node (p < 0.005) and bone metastases (p < 0.05) compared to the primary tumors. Our results of the first detailed quantitative analysis of PSMA mRNA expression in patient's tissues demonstrate that PSMA and the 3 PSMA splice variants are expressed in normal, benign, cancerous and metastatic prostate cancer. We note increased PSMA expression in some malignant tissues, however, these increases are modest in magnitude. We also report that the expression of a novel splice variant, PSM-D, is elevated in prostate cancer metastases.     

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.