Prostate-specific Antigen Expression Research Articles

Design, synthesis and evaluation of novel prostate-specific membrane antigen-targeted aryl [18F]fluorosulfate PET tracers

The expression of prostate-specific membrane antigen (PSMA) in prostate cancer is 100–1000 times higher than that in normal tissues, and it has shown great advantages in the diagnosis and treatment of prostate cancer. The combination of PSMA and PET imaging technology based on the principle of metabolic imaging can achieve high sensitivity and high specificity for diagnosis. Due to its suitable half-life (109 min) and good positron abundance (97%), as well as its cyclotron accelerated generation, 18F has the potential to be commercialize, which has attracted much attention. In this article, we synthesized a series of fluorosulfate PET tracers targeting PSMA. All four analogues have shown high affinity to PSMA (IC50 = 1.85–5.15 nM). After the radioisotope exchange labeling, [18F]L9 and [18F]L10 have PSMA specific cellular uptake (0.65 ± 0.04% AD and 1.19 ± 0.03% AD) and effectively accumulated in 22Rv1 xenograft mice model. This study demonstrates that PSMA-1007-based PSMA-targeted aryl [18F]fluorosulfate novel tracers have the potential for PET imaging in tumor tissues.

Impact of Circulating Tumor Cell-Expressed Prostate-Specific Membrane Antigen and Prostate-Specific Antigen Transcripts in Different Stages of Prostate Cancer.

Prostate-specific membrane antigen (PSMA)-based images, which visually quantify PSMA expression, are used to determine prostate cancer micrometastases. This study evaluated whether a circulating tumor cell (CTC)-based transcript platform, including PSMA mRNA, could help identify potential prognostic markers in prostate cancer. We prospectively enrolled 21 healthy individuals and 247 patients with prostate cancer [localized prostate cancer (LPCa), n = 94; metastatic hormone-sensitive prostate cancer (mHSPC), n = 44; and metastatic castration-resistant prostate cancer (mCRPC), n = 109]. The mRNA expression of six transcripts [PSMA, prostate-specific antigen (PSA), AR, AR-V7, EpCAM, and KRT 19] from CTCs was measured, and their relationship with biochemical recurrence (BCR) in LPCa and mCRPC progression-free survival (PFS) rate in mHSPC was assessed. PSA-PFS and radiological-PFS were also calculated to identify potential biomarkers for predicting androgen receptor signaling inhibitor (ARSI) and taxane-based chemotherapy resistance in mCRPC. CTC detection rates were 75.5%, 95.3%, and 98.0% for LPCa, mHSPC, and mCRPC, respectively. In LPCa, PSMA [hazard ratio (HR), 3.35; P = 0.028) and PSA mRNA (HR, 1.42; P = 0.047] expressions were associated with BCR. Patients with mHSPC with high PSMA (HR, 4.26; P = 0.020) and PSA mRNA (HR, 3.52; P = 0.042) expressions showed significantly worse mCRPC-PFS rates than those with low expression. Increased PSA and PSMA mRNA expressions were significantly associated with shorter PSA-PFS and radiological PFS in mCPRC, indicating an association with drug resistance. PSMA and PSA mRNA expressions are associated with BCR in LPCa. In advanced prostate cancer, PSMA and PSA mRNA can also predict rapid progression from mHSPC to mCRPC and ARSI or taxane-based chemotherapy resistance.

Enhancing the anticancer effect of androgen deprivation therapy by monocarboxylate transporter 1 inhibitor in prostate cancer cells.

Tumor initiation and progression necessitate a metabolic shift in cancer cells. Consequently, the progression of prostate cancer (PCa), a leading cause of cancer-related deaths in males globally, involves a shift from lipogenic to glycolytic metabolism. Androgen deprivation therapy (ADT) serves as the standard treatment for advanced-stage PCa. However, despite initial patient responses, castrate resistance emerges ultimately, necessitating novel therapeutic approaches. Therefore, in this study, we aimed to investigate the role of monocarboxylate transporters (MCTs) in PCa post-ADT and evaluate their potential as therapeutic targets. PCa cells (LNCaP and C4-2 cell line), which has high prostate-specific membrane antigen (PSMA) and androgen receptor (AR) expression among PCa cell lines, was used in this study. We assessed the expression of MCT1 in PCa cells subjected to ADT using charcoal-stripped bovine serum (CSS)-containing medium or enzalutamide (ENZ). Furthermore, we evaluated the synergistic anticancer effects of combined treatment with ENZ and SR13800, an MCT1 inhibitor. Short-term ADT led to a significant upregulation in folate hydrolase 1 (FOLH1) and solute carrier family 16 member 1 (SLC16A1) gene levels, with elevated PSMA and MCT1 protein levels. Long-term ADT induced notable changes in cell morphology with further upregulation of FOLH1/PSMA and SLC16A1/MCT1 levels. Treatment with ENZ, a nonsteroidal anti-androgen, also increased PSMA and MCT1 expression. However, combined therapy with ENZ and SR13800 led to reduced PSMA level, decreased cell viability, and suppressed expression of cancer stem cell markers and migration indicators. Additionally, analysis of human PCa tissues revealed a positive correlation between PSMA and MCT1 expression in tumor regions. Our results demonstrate that ADT led to a significant upregulation in MCT1 levels. However, the combination of ENZ and SR13800 demonstrated a promising synergistic anticancer effect, highlighting a potential therapeutic significance for patients with PCa undergoing ADT.

Genomic Correlates of Prostate-Specific Membrane Antigen Expression and Response to 177Lu-PSMA-617: A Retrospective Multicenter Cohort Study.

While 177Lu-PSMA-617 (LuPSMA) is an effective therapy for many patients with metastatic castration-resistant prostate cancer (mCRPC), biomarkers associated with outcomes are not well defined. We hypothesized that prostate cancer mutational profile may associate with clinical activity of LuPSMA. We devised a study to evaluate associations between mCRPC mutational profile with LuPSMA clinical outcomes. This was a multicenter retrospective analysis of patients with mCRPC with next-generation sequencing (NGS) who received LuPSMA. PSA50 response (ie, ≥50% decline in prostate-specific antigen [PSA]) rate, PSA progression free survival (PSA PFS), and overall survival (OS) were compared between genetically defined subgroups. One hundred twenty-six patients with NGS results who received at least one cycle of LuPSMA were identified. The median age was 73 (IQR, 68-78) years, 124 (98.4%) received ≥1 prior androgen receptor-signaling inhibitor, and 121 (96%) received ≥1 taxane-based chemotherapy regimen. Fifty-eight (46%) patients with a DNA damage repair gene mutation (DNA damage response group) and 59 (46.8%) with a mutation in TP53, RB1, or PTEN tumor suppressor genes (TSG group) were identified. After adjusting for relevant confounders, the presence of ≥1 TSG mutation was associated with shorter PSA PFS (hazard ratio [HR], 1.93 [95% CI, 1.05 to 3.54]; P = .034) and OS (HR, 2.65 [95% CI, 1.15 to 6.11]; P = .023). There was improved OS favoring the DNA damage response group (HR, 0.37 [95% CI, 0.14 to 0.97]; P = .044) on multivariable analysis. Univariate analysis of patients with ATM mutations had significantly higher rates of PSA50 response, PSA PFS, and OS. Outcomes on LuPSMA varied on the basis of mutational profile. Prospective studies to define the clinical activity of LuPSMA in predefined genomic subgroups are justified.

Abstract 61: A novel immunotherapy for metastatic prostate cancer: A monoclonal antibody that can bind both STEAP1 and STEAP2

Abstract Prostate cancer (PCa) is the second most prevalent cancer among males, and the 5-year survival rate for patients with metastatic PCa (mPCa) is ~30%. Although significant progress has been made in improving survival in mPCa patients, many of these patients experience relapse or systemic toxicities. Protein expression of prostate-specific membrane antigen (PSMA), a common PCa antigen often targeted in PCa therapy, is unfortunately lost in the later stages of mPCa. In contrast, six transmembrane epithelial antigen of the prostate 1 and 2 (STEAP1 and STEAP2) are both overexpressed in most PCa compared to normal and vital organs and has emerged as a next-generation target in mPCa. We hypothesize that an antibody that binds to both STEAP1 and STEAP2 via their second extracellular domain (60% homology) could be useful therapeutically. Using an immunogen of this second extracellular domain, we raised several antibody clones that appear to have an affinity towards both STEAP1 and STEAP2 (STEAP1/2). The specificity and affinity of these antibody clones were successfully determined by immunofluorescence, flow cytometry and ELISA. Immunofluorescence results in PCa cell lines and those that overexpress STEAP1 and STEAP2 demonstrate the potential specificity of one clone for human STEAP1 and STEAP2. In addition, ELISA data revealed that the binding affinity of this clone to STEAP1 and STEAP2 is in the low nanomolar and low micromolar range, respectively. This monoclonal STEAP1/2 antibody has been sequenced and will become the basis for future development of immunotherapies thus expanding the therapeutic armamentarium for mPCa. Citation Format: Minzhi Sheng, Gobi Thillainadesan, Amanda Sparkes, Boyang Su, Esther Matus, Jessica Wright, Stanley Liu, Jean Gariepy, Hon S. Leong. A novel immunotherapy for metastatic prostate cancer: A monoclonal antibody that can bind both STEAP1 and STEAP2 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 61.

YAP1 Regulates the YAP1/AR/PSA Axis through Autophagy in Castration-Resistant Prostate Cancer and Mediates T-Cell Immune and Inflammatory Cytokine Infiltration.

The emergence of castration-resistant prostate cancer (CRPC) following androgen deprivation therapy (ADT) is associated with increased malignancy and limited treatment options. This study aims to investigate potential connections between immune cell infiltration and inflammatory cytokines with the YAP1/AR/PSA axis by exploring their interactions with autophagy. Our research reveals heightened levels of Yes-associated protein 1 (YAP1) expression in CRPC tissues compared with tissues from androgen-dependent prostate cancer (ADPC) and benign prostate hyperplasia (BPH). Additionally, a correlation was observed between YAP1 and PSA expressions in CRPC tissues, suggesting that YAP1 may exert a regulatory influence on PSA expression within CRPC. Enhanced YAP1 expression in C4-2 cells resulted in the upregulation of androgen receptor (AR) nuclear translocation and intracellular prostate-specific antigen (PSA) levels. Conversely, the suppression of YAP1 led to a decrease in PSA expression, suggesting that YAP1 may positively regulate the PSA in castration-resistant prostate cancer (CRPC) by facilitating AR nuclear import. The modulation of the autophagy activity exerts a significant impact on the expression levels of YAP1, the AR, and the PSA. Moreover, recent advancements in immunity and inflammation studies present promising avenues for potential therapies targeting prostate cancer (PC).

Evaluation of prostate-specific membrane antigen expression in locally advanced or metastatic breast carcinoma with 68 Ga-PSMA-11 positron-emission tomography/computed tomography imaging for potential theranostics.

Prostate-specific membrane antigen (PSMA) is ubiquitously expressed in tumor-associated neovasculature and may be a potential theranostic in many solid cancers, including breast carcinoma (BC). Herein, we analyzed the presence of PSMA in BC, through qualitative and quantitative parameters on 68 Ga-PSMA-11 positron-emission tomography/computed tomography (PET/CT), across various hormonal subtypes. This study examined 41 female patients of BC. All underwent 68 Ga-PSMA-11 PET/CT. For qualitative analysis, a visual estimation of PSMA expression was performed as per miPSMA scoring system (VISION trial) and a score ≥2 was considered eligible for lutetium-177 ( 177 Lu)-PSMA-617 radioligand therapy (Lu-PRLT). For quantitative analysis, maximum standardized uptake values (SUVmax) were determined and ratios >1 for SUVmax lesion to SUVmax liver were considered eligible for Lu-PRLT. PSMA expression was correlated with hormonal status using Chi-square test. The sensitivity, specificity and area under curve (AUC) of PSMA expression were determined using receiver-operating characteristics analysis ( P < 0.05). A total of 19 patients (46.3%) and 15 patients (36.7%) in stage IV were found eligible for Lu-PRLT based on qualitative and quantitative analyses, respectively. Strong PSMA expression was detected in triple-negative and hormonal receptors-negative/human epidermal growth factor receptor 2-positive status on qualitative PSMA expression analysis. A sensitivity of 65.5%, specificity of 93.3% and AUC of 0.857 for SUVmax 6.5 on 68 Ga-PSMA-11 PET/CT were detected for PSMA expression for considering Lu-PRLT. We found a modest number of BC patients suited for Lu-PRLT, indicating that PSMA PET/CT imaging may be a valuable modality for selecting theranostics in a carefully selected group of breast carcinoma.

Prostate-specific membrane antigen expression in endothelial cells of renal tumor-associated neovasculature and risk of recurrence for renal cell carcinoma.

377 Background: PSMA is highly expressed in prostate epithelial cancer cells and used not only for diagnostic but also for therapeutic purposes. Despite its name, PSMA is not specific in prostate cells and is also expressed endothelial cells within the neovasculature of other tumors including renal cell carcinoma. PSMA is particularly the correlation of increased PSMA expression with prostate cancer aggressiveness, but is unknown in renal cell carcinoma patients. Here we estimate whether PSMA expression in endothelial cells of renal tumor-associated neovasculature is associated with pathological venous invasion and prognosis for patients after renal tumor surgery. Methods: A total of 45 patients who underwent radical or partial nephrectomies performed at our institution were included in this study. We investigated pathological venous invasion and PSMA expression in tumor-associated vessels around renal cell carcinoma by immunostaining using removed tumor tissue. The PSMA immunostain was evaluated in tumor-associated vessels according to the staining intensity and divided into three groups: weak, moderate, and strong, respectively. Results: Higher PSMA expression group is increased the percentage of patients with histologically observed venous invasion. The level of PSMA immnostain were detected in 18 cases at weak, 11 at moderate, 16 at strong. Ten patients after surgery had recurrence during the observation period, and the prognosis was worse in the group with strong PSMA expression in tumor-associated vessels around renal cell carcinoma. Conclusions: PSMA expression in endothelial cells of renal tumor-associated neovasculature may be a novel prognostic factor for renal cell carcinoma.

Daro-PET: A phase 2 trial of darolutamide as a prostate-specific membrane antigen (PSMA) expression enhancer in patients with localized prostate cancer.

TPS348 Background: Prostate specific membrane antigen (PSMA) has been explored as a target in imaging studies using positron emission tomography (PSMA-PET) to unveil occult prostate cancer metastasis, and as a target for radioligand therapy. Preclinical and retrospective clinical studies suggest that PSMA expression can be rapidly increased by androgen suppression, which might impact the accuracy of disease detection using PSMA-PET scans and radioligand treatment efficacy. Methods: Daro-PET (NCT05900973) is a single-arm phase 2 study to evaluate the efficacy of a limited course of darolutamide as a PSMA expression enhancer in men planned for radical prostatectomy due to high-risk localized prostate cancer as per conventional imaging. PSMA PET/CT scans will be acquired before (PSMA-PET 1) and after (PSMA-PET 2) a 7-day treatment with darolutamide 600 mg PO q12 h. The primary endpoint is the proportion of patients achieving an increase in SUVmax of 20% or greater from PSMA-PET 1 to PSMA-PET 2. Key secondary endpoints include other PSMA PET parameters (e.g. SUVmean, Total lesion PSMA), proportion of planned management changes, detection of pelvic or extrapelvic metastatic disease, and safety. Correlative exploratory studies will include PSMA expression by immunohistochemistry, gene expression, and methylation patterns between tissue samples from prostate biopsy and prostatectomy. The trial will enroll up to 16 patients using a Simon’s two-stage design, with a power of 0.80 and a one-sided alpha error of 0.05. As of September 20th, 1 patient was included in the study. Clinical trial information: NCT05900973 .

Multimodal, PSMA-Targeted, PAMAM Dendrimer-Drug Conjugates for Treatment of Prostate Cancer: Preclinical Evaluation.

Prostate cancer (PC) is the second most common cancer and the fifth most frequent cause of cancer death among men. Prostate-specific membrane antigen (PSMA) expression is associated with aggressive PC, with expression in over 90% of patients with metastatic disease. Those characteristics have led to its use for PC diagnosis and therapies with radiopharmaceuticals, antibody-drug conjugates, and nanoparticles. Despite these advancements, none of the current therapeutics are curative and show some degree of toxicity. Here we present the synthesis and preclinical evaluation of a multimodal, PSMA-targeted dendrimer-drug conjugate (PT-DDC), synthesized using poly(amidoamine) (PAMAM) dendrimers. PT-DDC was designed to enable imaging of drug delivery, providing valuable insights to understand and enhance therapeutic response. The PT-DDC was synthesized through consecutive conjugation of generation-4 PAMAM dendrimers with maytansinoid-1 (DM1) a highly potent antimitotic agent, Cy5 infrared dye for optical imaging, 2,2',2"-(1,4,7-triazacyclononane-1,4,7-triyl)triacetic acid (NOTA) chelator for radiolabeling with copper-64 and positron emission tomography tomography/computed tomography (PET/CT), lysine-urea-glutamate (KEU) PSMA-targeting moiety and the remaining terminal primary amines were capped with butane-1,2-diol. Non-targeted control dendrimer-drug conjugate (Ctrl-DDC) was formulated without conjugation of KEU. PT-DDC and Ctrl-DDC were characterized using high-performance liquid chromatography, matrix assisted laser desorption ionization mass spectrometry and dynamic light scattering. In vitro and in vivo evaluation of PT-DDC and Ctrl-DDC were carried out in isogenic human prostate cancer PSMA+PC3 PIP and PSMA-PC3 flu cell lines, and in mice bearing the corresponding xenografts. PT-DDC was stable in 1×PBS and human blood plasma and required glutathione for DM1 release. Optical, PET/CT and biodistribution studies confirmed the in vivo PSMA-specificity of PT-DDC. PT-DDC demonstrated dose-dependent accumulation and cytotoxicity in PSMA+ PC3 PIP cells, and also showed growth inhibition of the corresponding tumors. PT-DDC did not accumulate in PSMA- PC3 flu tumors and did not inhibit their growth. Ctrl-DDC did not show PSMA specificity. In this study, we synthesized a multimodal theranostic agent capable of delivering DM1 and a radionuclide to PSMA+ tumors. This approach holds promise for enhancing image-guided treatment of aggressive, metastatic subtypes of prostate cancer.

PC Kz is the novel human prostate cancer model in vitro and in vivo

BACKGROUND: The use of relevant in vitro and in vivo model systems is important in preclinical studies of anticancer agents. The process of creating tumor models is methodically complicated and has a number of disadvantages. Among tumor models of prostate cancer, the most accessible are 2D models (DU145, 22Rv1, PC3, LNCaP, VCaP cell lines), their xenograft models in immunodeficient mice and some patient-derived xenograft models. However, this panel of experimental models is not perfect and needs further expansion.&#x0D; AIM: To create a new preclinical prostate cancer model, characterize it (morphology, tumorigenicity, tumor growth kinetics in vivo, verification of prostate-specific membrane antigen expression status, testosterone production, sensitivity to CYP17A1 inhibitors), and develop resistance to the steroid CYP17A1 inhibitor — abiraterone.&#x0D; METHODS: CYP17A1 expression in PC Kz cell line was evaluated by reverse transcription polymerase chain reaction. Testosterone concentration was determined with an enzyme-linked immunosorbent assay. The sensitivity to antitumor agents was studied with the MTT test. Tumorigenicity was evaluated by transplantation of PC Kz cell line into Balb/c nude mice. The prostate-specific membrane antigen expression status was assessed using the indirect reaction of surface immunofluorescence.&#x0D; RESULTS: The PC Kz cell line is characterized by a high level of CYP17A1 messenger RNA expression, comparable to that of the commercial 22Rv1 cell line. Immunophenotypic analysis demonstrated negative prostate-specific membrane antigen expression status of PC Kz cell line. A significant decrease (18%) in testosterone concentration in vitro was found, compared to the value in the control. This effect can be associated with the suppression of CYP17A1 gene expression.&#x0D; The studied PC Kz cell line is tumorigenic in Balb/c nude mice (100% tumorigenicity was detected during the first passage at a transplantation dose of 107 cells/mouse). A pathomorphological study of the structures of the obtained subcutaneous PC Kz xenografts verified their identity to the histological image of human prostate cancer. Furthermore, PC Kz/AA cell line was obtained, resistant to abiraterone; the index of resistance was 3.4.&#x0D; CONCLUSION: The derived PC Kz cell line was adapted for in vitro and in vivo growth, characterized by the main biological parameters, and can be recommended as an adequate test system to use in preclinical studies of new antitumor agents for the human prostate cancer treatment.

Prostate-specific antigen: An unfamiliar protein in the human salivary glands.

The presence of prostate-specific antigen (PSA) in saliva and salivary glands has been reported. Nevertheless, its release pathway in these glands remains to be elucidated. Here, we showed PSA subcellular distribution focusing on its plausible route in human salivary parenchyma. Sections of parotid and submandibular glands were subjected to the immunohistochemical demonstration of PSA by the streptavidin-biotin method revealed by alkaline phosphatase. Moreover, ultrathin sections were collected on nickel grids and processed for immunocytochemical analysis, to visualize the intracellular distribution pattern of PSA through the observation by transmission electron microscopy. By immunohistochemistry, in both parotid and submandibular glands PSA expression was detected in serous secretory acini and striated ducts. By immunocytochemistry, immunoreactivity was retrieved in the cytoplasmic compartment of acinar and ductal cells, often associated with small cytoplasmic vesicles. PSA labeling appeared also on rough endoplasmic reticulum and in the acini's lumen. A negligible PSA labeling appeared in most of the secretory granules of both glands. Our findings clearly support that human parotid and submandibular glands are involved in PSA secretion. Moreover, based on the immunoreactivity pattern, its release in oral cavity would probably occur by minor regulated secretory or constitutive-like secretory pathways.

Abstract C090: High GLUT1 membrane expression and low PSMA membrane expression in ductal adenocarcinoma and intraductal carcinoma of the prostate

Abstract Background: Both Ductal Adenocarcinoma (DAC) and Intraductal Carcinoma (IDC) of the prostate are generally associated with aggressive clinical behavior and poor prognosis and can be lethal. Furthermore, previous studies linked aggressive clinical behavior and poor prognosis with discordant FDG positivity and low Prostate-specific membrane antigen (PSMA) expression. A recent study only cited a DAC patient with low 68Ga-PSMA-11 PET/CT uptake but high 18F-FDG PET/CT uptake, however, there is lack of directly compared articles nor large data sets. IDC-P has similar cribriform pattern in the pathological structure as a mean differential diagnosis for DAC. Hence, the objective of this study was to investigate the expression of PSMA and GLUT1 in DAC and IDC-P patients. Methods: The study was conducted on 87 DAC or IDCP patients without any treatment and 97 PAC patients with a Gleason score ≥ 8 of prostate biopsies and prostatectomy samples between August 2017 and August 2022. We performed immunohistochemical staining and scoring of various cancer component samples from the patients to reflect the protein expression levels of PSMA and GLUT1. Results: PSMA expression in PAC tissues was significantly higher than in DAC/IDC-P tissues (141.2 vs 78.6, p &amp;lt; 0.001). There was no significant difference in PSMA membrane expression between DAC/IDC-P and adjacent acinar adenocarcinoma (78.6 vs 93.4, p = 0.166). GLUT1 expression was higher in DAC/IDC-P tissue than in acinar adenocarcinoma tissue adjacent to DAC/IDC-P (68.6 vs 51.3, p = 0.007), but was still lower than that in PAC tissue (68.6 vs 93.1, p = 0.0014). It is worth noting that GLUT1 membrane expression in DAC/IDC-P was significantly increased than in PAC (13.0 vs 6.6, p = 0.025), and in acinar adenocarcinoma adjacent to DAC/IDC-P (13.0 vs 2.0, p &amp;lt; 0.001). Conclusions: In DAC and IDC-P tissues, PSMA membrane expression is low, while GLUT1 expression, especially GLUT1 membrane expression is high. These findings imply that DAC and IDC-P cells may have higher glucose metabolic and raise interest in targeting membrane GLUT1 as a novel anticancer strategy for DAC/IDC-P and other prostate cancer with high glucose metabolism. Citation Format: Xingming Wang, Xiaomei Gao, Lin Qi, Ye Zhang, Hongling Yin, Yu Gan, Yi Cai. High GLUT1 membrane expression and low PSMA membrane expression in ductal adenocarcinoma and intraductal carcinoma of the prostate [abstract]. In: Proceedings of the 16th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2023 Sep 29-Oct 2;Orlando, FL. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2023;32(12 Suppl):Abstract nr C090.

Prostate-Specific Membrane Antigen (PSMA) Expression Predicts Need for Early Treatment in Prostate Cancer Patients Managed with Active Surveillance.

Metabolic dysregulation is an early event in carcinogenesis. Here, we examined the expression of enzymes involved in de novo lipogenesis (ATP-citrate lyase: ACLY), glucose uptake (Glucose Transporter 1: GLUT1), and folate-glutamate metabolism (Prostate-Specific Membrane Antigen: PSMA) as potential biomarkers of risk for early prostate cancer progression. Patients who were managed initially on active surveillance with a Gleason score of 6 or a low-volume Gleason score of 7 (3 + 4) were accrued from a prostate cancer diagnostic assessment program. Patients were asked to donate their baseline diagnostic biopsy tissues and permit access to their clinical data. PSMA, GLUT1, and ACLY expression were examined with immunohistochemistry (IHC) in baseline biopsies, quantitated by Histologic Score for expression in benign and malignant glands, and compared with patient time remaining on active surveillance (time-on-AS). All three markers showed trends for elevated expression in malignant compared to benign glands, which was statistically significant for ACLY. On univariate analysis, increased PSMA and GLUT1 expression in malignant glands was associated with shorter time-on-AS (HR: 5.06, [CI 95%: 1.83-13.94] and HR: 2.44, [CI 95%: 1.10-5.44], respectively). Malignant ACLY and benign gland PSMA and GLUT1 expression showed non-significant trends for such association. On multivariate analysis, overexpression of PSMA in malignant glands was an independent predictor of early PC progression (p = 0.006). This work suggests that the expression of metabolic enzymes determined by IHC on baseline diagnostic prostate biopsies may have value as biomarkers of risk for rapid PC progression. PSMA may be an independent predictor of risk for progression and should be investigated further in systematic studies.

Auraptene Enhances AMP-Activated Protein Kinase Phosphorylation and Thereby Inhibits the Proliferation, Migration and Expression of Androgen Receptors and Prostate-Specific Antigens in Prostate Cancer Cells.

Citrus hassaku extract reportedly activates AMPK. Because this extract contains an abundance of auraptene, we investigated whether pure auraptene activates AMPK and inhibits proliferation using prostate cancer cell lines. Indeed, auraptene inhibited the proliferation and migration of LNCaP cells and induced phosphorylation of AMPK or its downstream ACC in LNCaP, PC3, and HEK-293 cells, but not in DU145 cells not expressing LKB1. In addition, the mTOR-S6K pathway, located downstream from activated AMPK, was also markedly suppressed by auraptene treatment. Importantly, it was shown that auraptene reduced androgen receptor (AR) and prostate-specific antigen (PSA) expressions at both the protein and the mRNA level. This auraptene-induced downregulation of PSA was partially but significantly reversed by treatment with AMPK siRNA or the AMPK inhibitor compound C, suggesting AMPK activation to, at least partially, be causative. Finally, in DU145 cells lacking the LKB1 gene, exogenously induced LKB1 expression restored AMPK phosphorylation by auraptene, indicating the essential role of LKB1. In summary, auraptene is a potent AMPK activator that acts by elevating the AMP/ATP ratio, thereby potentially suppressing prostate cancer progression, via at least three molecular mechanisms, including suppression of the mTOR-S6K pathway, reduced lipid synthesis, and AR downregulation caused by AMPK activation.

Comparison of 68Ga-PSMA-HBED-CC and 18F-FDG PET/CT in the Evaluation of Adenoid Cystic Carcinoma-A Prospective Study.

18F-FDG PET/CT plays a major role in diagnosis and staging of head and neck cancer; however, FDG has lower uptake in adenoid cystic carcinoma (AdCC). Prostate-specific membrane antigen (PSMA) expression is found to be associated with endothelial cells or tumor neovasculature in malignant AdCC and salivary duct carcinoma. Thus, present study is aimed to compare the role of 68Ga-PSMA and 18F-FDG PET/CT in patients with primary and/or metastatic AdCC. Histopathologically proven AdCC patients were intravenously injected with 370 MBq (10 mCi) of 18F-FDG and 111-185 MBq (3-5 mCi) of 68Ga-PSMA. Images were acquired at 60 and 45 minutes postinjection for 18F-FDG and 68Ga-PSMA, respectively, on dedicated PET/CT scanners. Visual and semiquantitative analyses of PSMA expression in regional and metastatic sites were performed by 2 experienced nuclear medicine physicians. Seventeen patients (7 men, 10 women) having mean age of 44 ± 14.19 years were prospectively included in the study. Of 17 patients, FDG PET/CT was performed in only 14 (82%) patients. PSMA and FDG uptakes were seen at the primary site in 16 (94%) and 13 (93%) patients, respectively, whereas 1 patient was postradical tumor excision. Lung lesions (n = 7) and lymph nodes (n = 5) were detected on both FDG and PSMA PET scans. However, cerebellar and meningeal metastasis (n = 1, 6%) and bony lesions (n = 2, 12%) were detected only on PSMA PET/CT but not visualized on FDG PET/CT scan. PSMA may have theranostic importance in unresectable or metastatic AdCC, besides having a role in staging/restaging.

Administering [177Lu]Lu-PSMA-617 Prior to Radical Prostatectomy in Men with High-risk Localised Prostate Cancer (LuTectomy): A Single-centre, Single-arm, Phase 1/2 Study

BackgroundHigh-risk localised prostate cancer (HRCaP) has high rates of biochemical recurrence; [177Lu]Lu-PSMA-617 is effective in men with advanced prostate cancer. ObjectiveTo investigate the dosimetry, safety, and efficacy of upfront [177Lu]Lu-PSMA-617 in men with HRCaP prior to robotic radical prostatectomy (RP). Design, setting, and participantsIn this single-arm, phase I/II trial, we recruited men with HRCaP (any of prostate-specific antigen [PSA] >20 ng/ml, International Society of Urological Pathology (ISUP) grade group [GG] 3–5, and ≥cT2c), with high tumour uptake on [68Ga]Ga-PSMA-11 positron emission tomography/computed tomography (PSMA PET/CT), and scheduled for RP. InterventionCohort A (n = 10) received one cycle and cohort B (n = 10) received two cycles of [177Lu]Lu-PSMA-617 (5 GBq) followed by surgery 6 weeks later. Outcome measurements and statistical analysisThe primary endpoint was tumour radiation absorbed dose. Adverse events (AEs; Common Terminology Criteria for Adverse Events (CTCAE) version 5.0), surgical safety (Clavien-Dindo), imaging, and biochemical responses were evaluated (ClinicalTrials.gov: NCT04430192). Results and limitationsBetween May 29, 2020 and April 28, 2022, 20 patients were enrolled. The median PSA was 18 ng/ml (interquartile range [IQR] 11–35), Eighteen (90%) had GG ≥3, and six (30%) had N1 disease. The median (IQR) highest tumour radiation absorbed dose after cycle 1 for all lesions was 35.5 Gy (19.5–50.1), with 19.6 Gy (11.3–48.4) delivered to the prostate. Five patients received radiation to lymph nodes. Nine (45%) patients achieved >50% PSA decline. The most common AEs related to [177Lu]Lu-PSMA-617 were grade 1 fatigue in eight (40%), nausea in seven (35%), dry mouth in six (30%), and thrombocytopenia in four (20%) patients. No grade 3/4 toxicities or Clavien 3–5 complications occurred. Limitations include small a sample size. ConclusionsIn men with HRCaP and high prostate-specific membrane antigen (PSMA) expression, [177Lu]Lu-PSMA-617 delivered high levels of targeted radiation doses with few toxicities and without compromising surgical safety. Further studies of [177Lu]Lu-PSMA-617 in this population are worthwhile to determine whether meaningful long-term oncological benefits can be demonstrated. Patient summaryIn this study, we demonstrate that up to two cycles of [177Lu]Lu-PSMA-617 given prior to radical prostatectomy in patients with high-risk localised prostate cancer are safe and deliver targeted doses of radiation to tumour-affected tissues. It is tolerated well with minimal treatment-related adverse events, and surgery is safe with a low rate of complications. Activity measured through PSA reduction, repeat PSMA PET/CT, and histological response is promising.

Radiochemical and biological assessments of a PSMA-I&S cold kit for fast and inexpensive 99mTc-labeling for SPECT imaging and radioguided surgery in prostate cancer.

The expression of prostate-specific membrane antigen (PSMA) is upregulated in prostate cancer (PCa) cells and PSMA-ligands have been radiolabeled and used as radiopharmaceuticals for targeted radionuclide therapy (TRT), single photon emission computed tomography (SPECT) or positron emission tomography (PET) molecular imaging, and radioguided surgery in PCa patients. Herein, we aimed at radiolabeling the PSMA-I&S cold kit with 99mTc, resulting in a radiopharmaceutical with high radiochemical yield (RCY) and stability for SPECT imaging and radioguided surgery in PCa malignancies. Various pre-clinical assays were conducted to evaluate the [99mTc]Tc-PSMA-I&S obtained by the cold kit. These assays included assessments of RCY, radiochemical stability in saline, lipophilicity, serum protein binding (SPB), affinity for LNCaP-PCa cells (binding and internalization studies), and ex vivo biodistribution profile in naive and LNCaP-PCa-bearing mice. The radiopharmaceutical was obtained with good RCY (92.05% ± 2.20%) and remained stable for 6h. The lipophilicity was determined to be -2.41 ± 0.06, while the SPB was ∼97%. The binding percentages to LNCaP cells were 9.41% ± 0.57% (1h) and 10.45% ± 0.45% (4h), with 63.12 ± 0.93 (1h) and 65.72% ± 1.28% (4h) of the bound material being internalized. Blocking assays, employing an excess of unlabeled PSMA-I&S, resulted in a reduction in the binding percentage by 2.6 times. The ex vivo biodistribution profile confirmed high accumulation of [99mTc]Tc-PSMA-I&S in the tumor and the tumor-to-contralateral muscle ratio was ∼6.5. In conclusion, [99mTc]Tc-PSMA-I&S was successfully obtained by radiolabeling the cold kit using freshly eluted [99mTc]NaTcO4, exhibiting good RCY and radiochemical stability. The preclinical assays demonstrated that the radiopharmaceutical shows favorable characteristics for SPECT imaging and radioguided surgery in PCa patients.

RNA-binding protein 14 promotes phase separation to sustain prostate specific antigen expression under androgen deprivation in human prostate cancer

Castration-resistant prostate cancer (CRPC) is a big challenge in managing prostate cancer patients. The androgen receptor (AR) pathway is a major driver even in CRPC under androgen deprivation. The mechanism in maintaining of the AR pathway under androgen deprivation remains elusive. The recent discovery of biomolecular condensate, a membrane-less intracellular construct formed by liquid-liquid phase separation (LLPS), that facilitate molecular assembly, encouraged the re-screening of our previous microarray data list. We selected Rbm14 as a target molecule for further analysis because it works as a coactivator of nuclear receptors as well as it facilitates formation of biomolecular condensates via its intrinsically disordered region. GFP-tagged Rbm14 transfected into HEK293T cells formed droplet-like puncta, which diminished following treatment with 1,6-hexanediol. Droplet-like structures were also observed in immunofluorescence for endogenous RBM14 of PC-3 and DU145 cells. Luciferase assay revealed that Rbm14 enhanced androgen-responsive element (ARE)-mediated reporter activity in all conditions with or without testosterone and AR. Co-immunoprecipitation confirmed the Rbm14–AR interaction. Long non-coding RNAs, including NEAT1, SRA1, and HOTAIR, were also interacted with Rbm14. Small interfering RNAs of NEAT1 reduced ARE-mediated reporter activity, while transfection of SRA1 and HOTAIR enhance the reporter activity. Treatment with 1,6-hexanediol as well as transfection with a dominant-negative splice variant of Rbm14 reduced expression of prostate specific antigen (PSA), a prototype of androgen-regulated gene, in LNCaP, PC-3, and DU145 cells under androgen deprivation. Immunohistochemically, RBM14 expression was substantially upregulated in prostate cancer tissues after androgen deprivation therapy than in untreated tumors. In conclusion, RBM14 is a novel factor involved in maintenance of PSA expression via phase separation under androgen deprivation in prostate cancer.

Antihormonal-Treatment Status Affects 68Ga-PSMA-HBED-CC PET Biodistribution in Patients with Prostate Cancer.

Androgen deprivation therapy (ADT) is known to influence the prostate-specific membrane antigen (PSMA) expression of prostate cancer, potentially complicating the interpretation of PSMA ligand PET findings and affecting PSMA radioligand therapy. However, the impact of ADT on PSMA ligand biodistribution in nontumorous organs is not well understood. Methods: Men (n = 112) with histologically proven prostate cancer who underwent 68Ga-PSMA-HBED-CC (68Ga-PSMA-11) PET/CT between November 2015 and July 2021 at the Medical University Vienna with known ADT status were retrospectively recruited. Fifty-six patients were on gonadotropin-releasing hormone-interfering ADT at the time of imaging (ADT group), whereas 56 patients with no history of ADT served as a control group. Physiologically PSMA-expressing organs (salivary glands, kidneys, liver, and spleen) were delineated, and their uptake was compared according to their data distributions. Multivariate regression analysis assessed the relationship between renal, hepatic, splenic, and salivary gland uptake and the explanatory variables metabolic tumor volume, glomerular filtration rate, and ADT status. Results: ADT was associated with lower levels of PSMA uptake in the kidneys (SUVmean: Δ[ADT - control] = -7.89; 95% CI, -10.73 to -5.04; P < 0.001), liver (SUVpeak: Δ[ADT - control] = -2.3; 95% CI, -5.72 to -0.93; P = 0.003), spleen (SUVpeak: Δ[ADT - control] = -1.27; 95% CI, -3.61 to -0.16; P = 0.033), and salivary glands (SUVmean: Δ[ADT - control] = -1.04; 95% CI, -2.48 to -0.13; P = 0.027). In a multivariate analysis, ADT was found to be associated with lower renal (SUVmean: β = -7.95; 95% CI, -11.06 to -4.84; P < 0.0001), hepatic (SUVpeak: β = -7.85; 95% CI, -11.78 to -3.91; P < 0.0001), splenic (SUVpeak: β = -5.83; 95% CI, -9.95 to -1.7; P = 0.006), and salivary gland (SUVmean: β = -1.47; 95% CI, -2.76 to -0.17; P = 0.027) uptake. A higher glomerular filtration rate was associated with a higher renal SUVmean (β = 0.16; 95% CI, 0.05 to 0.26; P = 0.0034). Conclusion: These findings suggest that ADT systemically modulates PSMA expression, which may have implications for treatment-optimizing and side-effect-minimizing strategies for PSMA radioligand therapies, particularly those using more potent 225Ac-labeled PSMA conjugates.