Clinical perspectives of PSMA PET/MRI for prostate cancer

Prostate cancer imaging has become an important diagnostic modality for tumor evaluation. Prostate-specific membrane antigen (PSMA) positron emission tomography (PET) has been extensively studied, and the results are robust and promising. The advent of the PET/magnetic resonance imaging (MRI) has added morphofunctional information from the standard of reference MRI to highly accurate molecular information from PET. Different PSMA ligands have been used for this purpose including 68gallium and 18fluorine-labeled PET probes, which have particular features including spatial resolution, imaging quality and tracer biodistribution. The use of PSMA PET imaging is well established for evaluating biochemical recurrence, even at low prostate-specific antigen (PSA) levels, but has also shown interesting applications for tumor detection, primary staging, assessment of therapeutic responses and treatment planning. This review will outline the potential role of PSMA PET/MRI for the clinical assessment of PCa.

Consensus of Chinese experts on the application of molecular imaging targeting prostate specific membrane antigen in prostate cancer patients / 中华外科杂志

Recently, prostate cancer has become the most common male urological cancer worldwide. However, it was difficult for the currently widely available imaging modalities to precisely diagnose this disease. With the development of nuclear medical technology, molecular imaging targeting prostate specific membrane antigen has been introduced into China. To promote the standardization of this imaging modality, the experts consensus was published by Chinese Anticancer Association Genitourinary Oncology Committee and recommendations for its application in the diagnosis and treatment of prostate cancer were attached, which would be helpful for doctors who are conducting or preparing for this examination.

Radical retropubic prostatectomy for prostate cancer with pelvic lymph node metastasis / 中华男科学杂志

Objective@#To investigate the safety and effectiveness of radical retropubic prostatectomy (RRP) with adjuvant androgen deprivation or external radiotherapy in the treatment of prostate cancer (PCa) with pelvic lymph node metastasis (PLNM).@*METHODS@#Twenty PCa patients underwent bilateral pedal lymphangiography (PLG) preoperatively, and 11 of them received lymph node aspiration for examination of the mRNA expressions of prostate-specific antigen (PSA) and prostate-specific membrane antigen (PSMA) in the lymph fluid by real-time RT-PCR. All the patients were treated by RRP with extended dissection of pelvic lymph nodes, and 3 of them by external radiotherapy in addition after recovery from urinary incontinence because of positive surgical margins, followed by adjuvant androgen deprivation therapy.@*RESULTS@#Real-time RT-PCR showed positive mRNA expressions of PSA and PSMA in the lymph fluid of the 11 patients, all pathologically confirmed with PLNM. The median intraoperative blood loss was 575 ml, with blood transfusion for 5 cases. Positive surgical margin was found in 3 cases, lymphorrhagia in 2 and urinary leakage in another 2 each. There were no such severe complications as vascular injury and rectum perforation. The patients were followed up for 6－48 (mean 42) months, during which, biochemical recurrence was observed in 12 cases at a median of 12 months postoperatively and 2 patients died at 12 and 48 months respectively.@*CONCLUSIONS@#Bilateral PLG and lymph node aspiration for examination of the mRNA expressions of PSA and PSMA in the lymph fluid help to confirm PLNM preoperatively. Radical retropubic prostatectomy with adjuvant androgen deprivation or external radiotherapy is safe and effective for the treatment of PCa with PLNM, but it should be chosen cautiously for those with Gleason 5+5.

Related biomarkers in the diagnosis of prostate cancer / 中华男科学杂志

Prostate cancer is one of the most common malignant tumors in the male urinary system as well as the second leading cause of cancer death in men. Prostate specific antigen (PSA) screening is the main method for the early diagnosis of prostate cancer, but has a low specificity for its detection. In recent years, a variety of tumor markers with high sensitivity and specificity have been found. This review focuses on some of the more promising tumor biomarkers such as prostate cancer antigen 3, early prostate cancer antigen, prostate-specific membrane antigen, alpha-methylacyl-CoA racemase, and vascular endothelial growth factor.

Prostate specific membrane antigen knockdown impairs the tumorigenicity of LNCaP prostate cancer cells by inhibiting the phosphatidylinositol 3-kinase/Akt signaling pathway / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Prostate specific membrane antigen (PSMA) can facilitate the growth, migration, and invasion of the LNCaP prostate cancer cell lines, but the underlying molecular mechanisms have not yet been clearly defined. Here, we investigated whether PSMA serves as a novel regulator of the phosphatidylinositol 3-kinase (PI3K)/Akt signaling by employing PSMA knockdown model and PI3K pharmacological inhibitor (LY294002) in LNCaP prostate cancer cells.</p><p><b>METHODS</b>PSMA knockdown had been stably established by transfecting with lentivirus-mediated siRNA in our previous study. Then, LNCaP cells were divided into interference, non-interference, and blank groups. We first testified the efficacy of PSMA knockdown in our LNCaP cell line. Then, we compared the expression of PSMA and total/activated Akt by Western blotting in the above three groups with or without LY294002 treatment. Furthermore, immunocytochemistry was performed to confirm the changes of activated Akt (p-Akt, Ser473) in groups. Besides, cell proliferation, migration, and cell cycle were measured by CCK-8 assay, Transwell analysis, and Flow cytometry respectively.</p><p><b>RESULTS</b>After PSMA knockdown, the level of p-Akt (Ser473) but not of total-Akt (Akt1/2) was significantly decreased when compared with the non-interference and blank groups. However, LY294002 administration significantly reduced the expression of p-Akt (Ser473) in all the three groups. The results of immunocytochemistry further confirmed that PSMA knockdown or LY294002 treatment was associated with p-Akt (Ser473) down-regulation. Decrease of cell proliferation, migration, and survival were also observed upon PSMA knockdown and LY294002 treatment.</p><p><b>CONCLUSIONS</b>Taken together, our results reveal that PI3K/Akt signaling pathway inhibition may serve as a novel molecular mechanism in LNCaP prostate cancer cells of PSMA knockdown and suggest that Akt (Ser473) may play a critical role as a downstream signaling target effector of PSMA in this cellular model.</p>

Construction, expression, and identification of the gene of human anti-prostate specific membrane antigen single-chain antibody / 中华男科学杂志

<p><b>OBJECTIVE</b>To construct, express and purify human fusion proteins composed of a single-chain antibody fragment scFv that recognizes the prostate specific membrane antigen (PSMA) protein, Fdt, HA2 and tp, and to analyze the binding activity of the expressed fusion proteins.</p><p><b>METHODS</b>The fusion protein genes scFv, scFv-tp, and scFv-Fdt-HA2-tp were amplified by PCR, and the genes obtained were then cloned into the expression vector pET28 and expressed in E. coli BL21. The expressed products were identified by SDS-PAGE and Western blot and purified with Ni(2+)-NTA chelating agarose. The antigen-binding activity of the fusion proteins was determined by ELISA.</p><p><b>RESULTS</b>The human anti-PSMA fusion gene was successfully constructed and expressed in M15 as the inclusion body after induced with IPTG. All the target proteins expressed could bind the PSMA antigen.</p><p><b>CONCLUSION</b>Fusion proteins can specifically bind the PSMA antigen. This finding contributes to the study of the targeted delivery of siRNA.</p>

PGC and PSMA in prostate cancer diagnosis: tissue analysis from biopsy samples

Purpose The discovery of new diagnostic tools for the diagnosis of prostate cancer (PCa) has become an important field of research. In this study, we analyzed the diagnostic value of the expression of the pepsinogen C (PGC) and prostate-specific membrane antigen (PSMA) genes in tissue samples obtained from prostate biopsies. Materials and Methods This study was comprised of 51 consecutive patients who underwent transrectal ultrasound (TRUS)-guided prostate biopsies between January 2010 and March 2010. The biopsies were performed with 12 cores, and an additional core was randomly retrieved from the peripheral zone from each patient for study purposes. The expression of the PGC and PSMA genes was analyzed from the cDNA from the samples via the qRT-PCR technology. The expression patterns of patients with PCa were compared with those of patients without a PCa diagnosis. Results PSMA was overexpressed in only 43.4% of PCa cases, and PGC was overexpressed in 72.7% of cases. The median expression of PSMA was 1.5 times (0.1 to 43.9) and the median PGC expression was 8.7 times (0.1 to 50.0) the expression observed in prostatic tissue from TRUS-guided biopsies of normal patients. Analysis of patients with high-risk PCa indicated that PGC was overexpressed in 71.4% of cases (with a median expression of 10.6 times), and PSMA was overexpressed in only 35.7% of cases (with a median expression of 4.5 times). Among patients with low-risk PCa, PGC was also overexpressed in 71.4% of cases (with a median expression of 5.9 times), and PSMA was overexpressed in only 42.8% of cases (with a median expression of 2.5 times). Conclusions PGC gene expression is significantly higher in prostatic tissue in men affected by PCa when compared to normal prostates. Further analyses are necessary to confirm our results. .

Cellular distribution and heterogeneity of PSA and PSMA expression in normal, hyperplasia and human prostate cancer

As promising targets for in vivo diagnostic, prognostic and therapeutic approaches, the distribution and staining pattern of prostate specific antigen [PSA] and prostate specific membrane antigen [PSMA] in tumors are of significant interest. To compare the cellular distribution and heterogeneity of PSA and PSMA expression in normal prostate [NP], benign prostatic hyperplasia [BPH] and primary prostatic tumors and to analyze their relation with the angiogenic activity according to Gleason grade [low, medium and high] in primary PC. The study was carried out in 6 NP, 44 BPH and 39 PC. Immunohistochemical analysis was performed. Monoclonal antibodies 3E6 and ER-PR8 were used to assess PSMA and PSA expression respectively. The evaluation of angiogenesis was made by CD34 immune marker. In our study we noticed differences in the intracellular localization of the PSMA immunostaining which seem to be related to the normal and pathological context. A significant number of primary tumors presented with apical pattern of PSMA [28/39]; whereas a relevant part of NP samples and BPH samples showed cytoplasmic localization [4/6 and 30/44, respectively] in luminal epithelial cells. Compared to PSMA, PSA was preferentially localized in cytoplasmic compartment in all type of prostate. A direct correlation between histological grade, PSMA expression and angiogenic activity could be demonstrated in primary PC. Simultaneous stains with PSA and PSMA in individual prostate tissue will greatly improve the detection rate and identify a high risk PC that could progress to metastatic phenotype. Our findings clearly support the feasibility but also direct the potential of PSMA-targeted in vivo therapeutic approaches in PC patients rather than PSA especially those with poorly differentiated adenocarcinoma

Glutamate carboxypeptidase II (GCPII) genetic variants as determinants of hyperhomocysteinemia: Implications in stroke susceptibility.

The rationale of this case-control study is to ascertain whether glutamate carboxypeptidase II (GCPII) variants serve as determinants of hyperhomocysteinemia and contribute to the etiology of stroke. Hyperhomocysteinemia was observed in stroke cases compared to controls (14.09 ± 7.62 mmol/L vs. 8.71 ± 4.35, P<0.0001). GCPII sequencing revealed two known variants (R190W and H475Y) and six novel variants (V108A, P160S, Y176H, G206R, G245S and D520E). Among the haplotypes of GCPII, all wild-haplotype H0 showed independent association with stroke risk (OR: 9.89, 95% CI: 4.13-23.68), while H2 representing P160S variant showed reduced risk (OR: 0.17, 95% CI: 0.06-0.50). When compared to subjects with H2 haplotype, H0 haplotype showed elevated homocysteine levels (18.26 ± 4.31 mmol/L vs. 13.66 ± 3.72 mmol/L, P = 0.002) and reduced plasma folate levels (7.09 ± 1.19 ng/ml vs. 8.21 ± 1.14 ng/ml, P = 0.007). Using GCPII genetic variants, dietary folate and gender as predictor variables and homocysteine as outcome variable, a multiple linear regression model was developed. This model explained 36% variability in plasma homocysteine levels. To conclude, GCPII haplotypes influenced susceptibility to stroke by influencing homocysteine levels.

Prostate-specific membrane antigen can promote in vivo osseous metastasis of prostate cancer cells in mice

Reports remain insufficient on whether and how prostate-specific membrane antigen (PSMA) can influence in vivo osseous metastasis of prostate cancer (PCa). In the present study, the authors induced stable expression of PSMA in mouse PCa cell line RM-1. In vivo osseous metastasis was induced in 37 6-week-old female C57BL/6 mice weighing 22.45 ± 0.456 g. RM-1 cells were actively injected into the femoral bone cavity, leading to bilateral dissymmetry of bone density in the femoral bone. Tumor cells were also detected in bone tissue by pathological examination. The impact on bone density was demonstrated by the significant difference between animals injected with RM-PSMA cells (0.0738 ± 0.0185 g/cm²) and animals injected with RM-empty plasmid cells (0.0895 ± 0.0241 g/cm²). The lytic bone lesion of the RM-PSMA group (68.4%) was higher than that of the control group (27.8%). Immunohistochemistry showed that the expression of both vascular endothelial growth factor (VEGF) and matrix metalloproteinase-9 (MMP-9) was distinctly higher in the RM-PSMA group than in the control group, while ELISA and Western blot assay indicated that VEGF and MMP-9 were higher in the RM-PSMA group compared to the control group (in vitro). Thus, the present study proposed and then confirmed for the first time that PSMA can promote in vivo osseous metastasis of PCa by increasing sclerotic destruction of PCa cells. Further analyses also suggested that PSMA functions positively on the invasive ability of RM-1 by increasing the expression of MMP-9 and VEGF by osseous metastases in vivo.

Clinical molecular imaging with radiotracers: current status

Molecular imaging is defined as the visualization, characterization, and measurement of biological processes at the molecular and cellular levels in humans and other living systems. Most clinical molecular imaging is currently done using radioisotope-labeled agents to define the activity of various metabolic pathways in vivo or to determine the distribution and density of various receptors relevant to human disease. This paper briefly reviews most of the commonly used radiopharmaceuticals in nuclear medicine, as well as newer agents that are likely to become available in the near future. The metabolic pathways include those relevant to the thyroid, parathyroid, heart, brain, bones, kidneys, liver, pancreas, adrenals and tumor. The receptor systems include agents useful in evaluating movement disorders, dementia, cardiac sympathetic enervation and neoangiogenesis. Receptor systems relevant to tumors include somatostatin receptors [neuroendocrine tumors], prostate-specific membrane antigen, carbonic anhydrase IX [renal cancer], and CD-20 [lymphoma]. These agents, and newer agents that are being developed, are likely to become critical in the development of personalized medicine, where it will become increasingly important to determine whether a treatment that is targeted to a specific metabolic pathway or receptor is likely to be successful

Silencing effect of cell-specific RNA interference plasmid pPSMAe/p-shNS-ploy(A) loaded by transgenic vector Tf-PEG-PEI targeting nucleostemin on prostate cancer cells in vitro / 中华肿瘤杂志

<p><b>OBJECTIVE</b>To explore the transgenic efficiency of non-viral vector Tf-PEG-PEI and the cell specific silencing effect of plasmid pPSMAe/p-shNS-ploy(A) on prostate cancer cells.</p><p><b>METHODS</b>Polyethyleneimine (PEI) was modified by using polyethylene glycol and transferrin to synthesize the non-viral vector Tf-PEG-PEI. NS-specific plasmids pPSMAe/p-shNS-ploy(A) and Tf-PEG-PEI were used to transfect prostate cancer LNCap and PC-3 cells. The changes of cell morphology, proliferation ability and cell cycle were studied after down-regulating the NS gene level.</p><p><b>RESULTS</b>Tf-PEG-PEI was successfully modified. After transfection, the PSMA-expressing LNCaP cells became larger and showed more pseudopodia, having a tendency to differentiate. Their cell proliferation ability was reduced, and the detection of cell cycle showed a decrease of S phase and an increase of G(1) phase after knocking down NS gene. These targets were not changed in non-PSMA-expresing PC-3 cells.</p><p><b>CONCLUSIONS</b>The non-viral vector Tf-PEG-PEI has a high ability to transfer targeted gene into target cells. The cellular specificity of short-hairpin RNA transcription driven by PSMAe/p is confirmed by silencing NS gene. The use of cell specific promoter may be an effective strategy of gene therapy for prostate cancer.</p>

Transcriptional activities of tumor-specific survivin promoter and PSMA promoter and enhancer in human prostate cancer: evaluation and comparison / 中华男科学杂志

<p><b>OBJECTIVE</b>To detect and compare the transcriptional activities of prostate-specific membrane antigen (PSMA) promoter and enhancer and survivin promoter in different human prostate cancer cell lines, and to search for some evidence for the targeting gene therapy of human prostate cancer.</p><p><b>METHODS</b>The fragments of the PSMA promoter and enhancer and survivin promoter were amplified by PCR and inserted into pGL3-Basic. The recombinant plasmids were transiently transfected into human prostate cancer cell lines and normal Chang liver cells, and, their transcriptional activities in various cells were determined by measuring the expression of luciferase.</p><p><b>RESULTS</b>The survivin promoter exhibited a higher transcriptional activity than PSMA promoter and enhancer in tumor cell lines, and the S2pro promoter showed the highest activity, reaching one third of that of the CMV promoter.</p><p><b>CONCLUSION</b>The survivin promoter is highly activated in prostate cancer cell lines and may serve as a new tool for the transcriptional targeting gene therapy of prostate cancer.</p>

Prostate Specific Membrane Antigen mRNA in Blood as a Potential Predictor of Biochemical Recurrence after Radical Prostatectomy

We investigated whether the detection of prostate specific membrane antigen (PSMA) in blood preoperatively has predictive value for biochemical recurrence (BCR) after radical prostatectomy in patients with prostate cancer. All 134 patients scheduled to receive radical prostatectomy for prostate cancer were prospectively enrolled. The authors used nested reverse transcriptase-polymerase chain reaction (RT-PCR) assay to detect PSMA mRNA-bearing cells in peripheral blood, and analyzed the ability of PSMA mRNA positivity to predict BCR after surgery. PSMA-mRNA was detected in 24 (17.9%) patients by RT-PCR. Over a median follow-up of 20 months (range, 3 to 46 months), BCR developed in 15 patients (11.2%) and median time to BCR was 7 months (range, 3 to 25 months). Kaplan-Meier analysis revealed a significant difference between those positive or negative for PSMA in terms of recurrence-free actuarial probability (log rank P=0.0039). Multivariate analysis showed that positivity for PSMA mRNA (HR: 3.697, 95% CI 1.285-10.634, P=0.015) and a biopsy Gleason score of > or =7 (HR: 4.500, 95% CI 1.419-14.274, P=0.011) were independent preoperative predictors of BCR. The presence of PSMA mRNA in peripheral blood can be used to predict BCR after radical prostatectomy.

Advances in prostate-specific membrane antigen targeted therapies for prostate cancer / 中华男科学杂志

Prostate-specific membrane antigen (PSMA) is a type II integral membrane glycoprotein, specifically expressed in prostatic epithelial cells and strongly upregulated in prostate cancer. PSMA is also present in the neovasculature of other solid tumors. These findings have spurred the development of PSMA-targeted therapies for prostate cancer, including immunotherapy, radioimmunotherapy, chemotherapy and gene therapy, and initiated the clinical trials of the first-generation products. However, general clinical application of these therapies still requires extensive clinical studies to test their clinical safety, stability and efficacy.

Auto-dendritic cell vaccines pulsed with PSA, PSMA and PAP peptides for hormone-refractory prostate cancer / 中华男科学杂志

<p><b>OBJECTIVE</b>To investigate the clinical safety and effects of auto-dendritic cells pulsed with HLA-A201-binding peptides prostate-specific antigen (PSA) , prostate-specific membrane antigen (PSMA) and prostatic acid phosphatase (PAP) in the treatment of hormone-refractory metastatic prostate cancer (HRPC).</p><p><b>METHODS</b>Sixteen HRPC patients with positive HLA-A201 were enrolled and their monocytes isolated and induced into dendritic cells with the combination of rhGM-CSF and rhIL4. The patients were inoculated subcutaneously near the inguinal region with auto-DCs pulsed with peptides PSA (KLQCVDLHV) , PSMA (ALDVYNGL L) and PAP (LLHETDSAV) every 2 weeks for 4 times, and the immunological and clinical responses were examined within 1 -2 weeks after the final vaccination.</p><p><b>RESULTS</b>Vaccination of dendritic cells was well tolerated and no toxicity was observed. The cytokine levels in the serum such as IL-2, IL-12 and IFN-gamma were significantly increased after the vaccination (P < 0.01). The delayed type hyper- sensitivity (DTH) test was positive in 4 of the patients (4/11), the percentage of antigen-special IFN-gamma+ CD8+ T increased in 5 (5/11), the level of the tumor marker PSA decreased in 6 (6/16) , hydrops abdominis reduced in 1 (1/16), and the size of the cervical lymph node lessened in 1 (1/16). Three patients showed partial remission (PR), 7 stability of the disease (SD), and the other 6 progression of the disease (PD).</p><p><b>CONCLUSION</b>Auto-DC vaccines loaded with PSA, PSMA and PAP peptides, capable of eliciting specific immune responses in HRPC patients, is a safe and effective option for the treatment of advanced HRPC.</p>

Updated application of prostate-specific membrane antigen to the diagnosis and treatment of prostate cancer / 中华男科学杂志

Prostate-specific membrane antigen (PSMA), the research of which has flourished in recent years, is a specific prostate cancer marker. PSMA plays a more and more important role in the early diagnosis, gene treatment and prognosis of the disease course of prostate cancer. This review focuses on the progress in researches of the structure, function, expression traits and gene expression of the PSMA protein, prostate cancer radioimmunoimaging, DNA vaccines and suicide gene therapy based on PSMA, as well as the role of PSMA in the clinical diagnosis and treatment of prostate cancer.

Clinical significance of expression of PSA, hK2, PSMA in the peripheral blood of patients with prostate cancer / 中华肿瘤杂志

<p><b>OBJECTIVE</b>To find sensitive and specific micro-metastic markers for prostate cancer.</p><p><b>METHODS</b>Using nested reverse transcription-PCR, we examined the expression of PSA, hK2 and PSMA mRNA in peripheral blood mononuclear cells of 51 patients with prostate cancer, 33 patients with benign prostate hyperplasia (BPH) and 32 normal young people.</p><p><b>RESULTS</b>The expression rates of PSA, hK2 and PSMA mRNA were 52.9%, 43.1% and 64.7%, respectively in prostate cancer group, and 6.2%, 7.7% and 4.6%, respectively in control group (BPH patients and normal young people) with statistical significance (P < 0.01). Although the expression rate of PSA and hK2 mRNA increased with cancer progression, there was no statistical significance among patients in different stages. The expression rate of PSMA mRNA was higher than that of PSA and hK2 mRNA in each clinical stage.</p><p><b>CONCLUSION</b>PSMA mRNA expression detected by nested RT-PCR is of greater value for the diagnosis, therapy choice and prognostic evaluation of prostate cancer patients.</p>

Correlation study of expression levels of prostate-specific membrane antigen and prostate-specific antigen with Gleason score of prostate carcinoma / 中华肿瘤杂志

<p><b>OBJECTIVE</b>To study the correlation of prostate-specific membrane antigen (PSMA) and prostate-specific antigen (PSA) expression with Gleason score of prostate carcinoma.</p><p><b>METHODS</b>Monoclonal antibodies against epitopes of PSMA extracellular domain were prepared, with which the expression of PSMA of prostate carcinoma (PC) was determined by immunohistochemical staining. Correlation of its expression with Gleason score of PC was statistically analyzed, and compared with that of PSA.</p><p><b>RESULTS</b>Eight hybridoma cell lines secreting monoclonal antibodies specific for PSMA were prepared. PSMA expression level was positively correlated with Gleason score. In poorly differentiated prostate carcinoma, the expression intensity of PSMA was higher than that of medium-and well-differentiated prostate carcinoma (P < 0.01). However, there was no correlation between level of PSA expression and Gleason score (P > 0.05).</p><p><b>CONCLUSION</b>PSMA expression level may be used as a useful surrogate marker in Gleason grading of prostate carcinoma. It may be a more suitable target than PSA in antibody mediated immunotherapy against poorly differentiated prostate carcinoma which is usually not sensitive to hormonal therapy.</p>