Low Prostate-specific Membrane Antigen Research Articles

Novel technetium-99m-labeled bivalent PSMA-targeting probe based on hydroxamamide chelate for diagnosis of prostate cancer.

Prostate-specific membrane antigen (PSMA) is a well-known biomarker of prostate cancer. Previously, our group reported that the succinimidyl-cystatin-urea-glutamate (SCUE) moiety has a high affinity for PSMA. In this study, we developed the novel technetium-99m-labeled PSMA-targeting probe "[99mTc]Tc-(Ham-SCUE)2" based on a hydroxamamide chelate with a bivalent SCUE and evaluated its potential as a SPECT imaging probe for the diagnosis of PSMA-expressing prostate cancer. Ham-SCUE was synthesized by a one-step reaction with Ham-Mal and cysteine-urea-glutamine. Then, Ham-SCUE was reacted with [99mTc]NaTcO4 for 10min at room temperature to obtain [99mTc]Tc-(Ham-SCUE)2. [99mTc]Tc-(Ham-SCUE)2 was added to LNCaP (high PSMA expression) cells or PC3 (low PSMA expression) cells, and their radioactivity was measured 60min after administration. The blocking study was performed by co-incubation of LNCaP cells with various concentrations of 2-PMPA (a PSMA inhibitor) for 15min before adding [99mTc]Tc-(Ham-SCUE)2. The biodistribution of [99mTc]Tc-(Ham-SCUE)2 in LNCaP/PC3 dual xenografted C.B.-17/Icr scid/scid Jcl mice was evaluated for 120min after intravenous injection. The blocking study was performed by pretreatment of mice with 2-PMPA (10mg/kg weight). [99mTc]Tc-(Ham-SCUE)2 was acquired at radiochemical yields of 56% with a radiochemical purity of over 95%. The cellular uptake level of [99mTc]Tc-(Ham-SCUE)2 by LNCaP cells was significantly higher than that by PC3 cells (LNCaP: 11.12 ± 0.71 vs. PC3: 1.40 ± 0.13%uptake/mg protein, p < 0.01), and the uptake was significantly suppressed by pretreatment with 2-PMPA (2.56 ± 0.37%uptake/mg protein, p < 0.05). IC50 of 2-PMPA was 245 ± 47nM. In the in vivo study, the radioactivity of LNCaP tumor tissue was significantly higher than that of PC3 tumor tissue at 120min after the administration of [99mTc]Tc-(Ham-SCUE)2 (LNCaP: 9.97 ± 2.79, PC3: 1.16 ± 0.23%ID/g, p < 0.01), and was suppressed by pretreatment with 2-PMPA (2.50 ± 0.45%ID/g, p < 0.01). [99mTc]Tc-(Ham-SCUE)2 has the potential to be a SPECT imaging agent for diagnosing high PSMA-expressing prostate cancer.

The role of PSMA PET/CT in predicting downgrading in patients with Gleason score 4+4 prostate cancer in prostate biopsy

BackgroundTo investigate the predictable parameters associated with downgrading in patients with a Gleason score (GS) 8 (4+4) in prostate biopsy after radical prostatectomy.MethodsWe retrospectively analyzed 62 patients with a GS of 4+4 on prostate biopsy who underwent robotic radical prostatectomy between 2017 and 2022.Results38 of 62 (61.2%) were downgraded. In multivariable logistic regression model, Ga-68 prostate-specific membrane antigen (PSMA) positron-emission tomography (PET)/computed tomography (CT) SUV max was independent predictor of downgrading (OR 0.904; p = 0.011) and a Logistic Regression model was constructed using the following formula: Y = 1.465–0.95 (PSMA PET/CT SUV max). The model using this variable correctly predicted the downgrading in 72.6% of patients. The AUC for PSMA PET/CT SUV max was 0.709 the cut off being 8.8.A subgroup analysis was performed in 37 patients who had no other European Association of Urology (EAU) high risk features. 25 out of 37 (67.5%) were downgraded, and 21 of these 25 had organ confined disease. Low PSMA SUV max (<8.1) and percentage of GS 4+4 biopsy cores to cancer bearing cores (45.0%) were independently associated with downgrading to GS 7.ConclusionPSMA PET/CT can be used to predict downgrading in patients with GS 4+4 PCa. Patients with GS 4+4 disease, but no other EAU high risk features, low percentage of GS 4+4 biopsy cores to cancer bearing cores, and a low PSMA PET/CT SUV max are associated with a high likelihood of the cancer reclassification to intermediate risk group.

Abstract 6023: 225Ac-FL-020 is a novel PSMA-targeting radionuclide drug conjugate (RDC) with superior in vivo anti-tumor activity

Abstract Despite significant developments over the last few decades, metastatic castration-resistant prostate cancer (mCRPC) remains incurable. Prostate specific membrane antigen (PSMA), a prostate cancer-specific membrane marker which directly correlates with androgen independence, metastasis, and disease progression, has been well-established as a radioligand target for the diagnosis and treatment of mCRPC. Lutetium-177 (177Lu)-PSMA-617 (PLUVICTOTM) was approved in 2022 for the treatment of progressive PSMA-positive mCRPC. However, only 30% of patients showed a radiological response in the registrational trial. Meanwhile, recent clinical experience has shown very limited efficacy in low PSMA expressing patients. These data collectively request for further improvement in the clinical benefit of PSMA-targeted radiotherapy. Actinium-225 (225Ac), an alpha emitter, is significantly more potent on cancer cell killing and has a shorter range in tissue penetration when compared to the beta emitter 177Lu. Such a profile supports the development of 225Ac based radiotherapies. Using our proprietary Clear-XTM technology platform, we developed 225Ac-FL-020, a novel 225Ac-based PSMA radioligand therapy candidate which has demonstrated prominent pre-clinical properties. We have assessed the binding affinity against PSMA of the non-labeled vector FL-020 in vitro. The in vivo biodistribution profile of FL-020 was characterized by SPECT/CT imaging and biodistribution using Indium-111 (111In)-FL-020 in PSMA high LNCaP tumor-bearing nude mice. In addition, anti-tumor activities of 225Ac-FL-020 were evaluated in the LNCaP xenograft model and directly compared to 225Ac-PSMA-617. FL-020 was found bound to LNCaP cells with an IC50 value of 51.55 nM. Meanwhile, the off-target screening showed that less than 50% inhibition of binding or activity was observed by FL-020 at 10 µM against 85 targets including receptors, ion channels, enzymes, and transporters, indicating the high selectivity of FL-020. Moreover, 111In-FL-020 displayed a very promising in vivo distribution profile with high and sustained tumor uptake and fast systemic clearance. Furthermore, 225Ac-FL-020 exhibited superior anti-tumor activity compared to 225Ac-PSMA-617 at the same dose level (10 KBq/mouse) in the LNCaP xenograft model with a favorable safety profile as indicated by body weight and hematological parameters. A mechanistic study was also conducted in 225Ac-FL-020-treated LNCaP tumor samples where DNA double-strand breaks and tumor cell apoptosis were observed, confirming the MOA of alpha emitters. Taken together, these results collectively demonstrate that 225Ac-FL-020 is a potent and selective PSMA-targeting radioligand therapy candidate with superior anti-tumor activity and a favorable safety profile warranting further clinical development. Citation Format: Fa Liu, Jiangwei Zhang, Junyu Yang, Kirstine T. Thrane, Mathias W. Hallund, Rikke V. Grønlund, Nicholas C. Wong. 225Ac-FL-020 is a novel PSMA-targeting radionuclide drug conjugate (RDC) with superior in vivo anti-tumor activity [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 6023.

PSMA PET/CT as a predictive tool for subregional importance estimates in the parotid gland

Objective. Xerostomia and radiation-induced salivary gland dysfunction remain a common side effect for head-and-neck radiotherapy patients, and attempts have been made to quantify the heterogeneity of the dose response within parotid glands. Prostate Specific Membrane Antigen (PSMA) ligands have demonstrated high uptake in salivary glands, which has been shown to correlate with gland functionality. Here we compare several models of parotid gland subregional relative importance with PSMA positron emission tomography (PET) uptake. We then develop a predictive model for Clark et al's relative importance estimates using PSMA PET and CT radiomic features, and demonstrate a methodology for predicting patient-specific importance deviations from the population. Approach. Intra-parotid gland uptake was compared with four regional importance models using 30 [18F]DCFPyL PSMA PET images. The correlation of uptake and importance was ascertained when numerous non-overlapping subregions were defined, while a paired t-test was used to compare binary region pairs. A radiomics-based predictive model of population importance was developed using a double cross-validation methodology. A model was then devised for supplementing population-level subregional importance estimates for each patient using patient-specific radiomic features. Main Results. Anticorrelative relationships were found to exist between PSMA PET uptake and four independent models of subregional parotid gland importance from the literature. Kernel Ridge Regression with principal component analysis feature selection performed best over test sets (Mean Absolute Error = 0.08), with gray level co-occurrence matrix (GLCM) features being particularly important. Deblurring PSMA PET images with neural blind deconvolution strengthened correlations and improved model performance. Significance. This study suggests that regions of relatively low PSMA PET uptake in parotid glands may exhibit relatively high dose-sensitivity. We’ve demonstrated the utility of PSMA PET radiomic features for predicting relative importance within subregions of parotid glands. PSMA PET appears to be a promising quantitative imaging modality for analyzing salivary gland functionality.

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.

Overall survival with [177Lu]Lu-PSMA-617 versus cabazitaxel in metastatic castration-resistant prostate cancer (TheraP): secondary outcomes of a randomised, open-label, phase 2 trial

The TheraP study reported improved prostate-specific antigen responses with lutetium-177 [177Lu]Lu-PSMA-617 versus cabazitaxel in men with metastatic castration-resistant prostate cancer progressing after docetaxel. In this Article, we report the secondary outcome of overall survival with mature follow-up, and an updated imaging biomarker analysis. We also report the outcomes of participants excluded due to ineligibility on gallium-68 [68Ga]Ga-PSMA-11 and 2-[18F]fluoro-2-deoxy-D-glucose (2-[18F]FDG) PET-CT. TheraP was an open-label, randomised phase 2 trial at 11 centres in Australia. Eligible participants had metastatic castration-resistant prostate cancer progressing after docetaxel, and PET imaging with [68Ga]Ga-PSMA-11 and 2-[18F]FDG that showed prostate-specific membrane antigen (PSMA)-positive disease and no sites of metastatic disease with discordant 2-[18F]FDG-positive and PSMA-negative findings. Participants were randomly assigned (1:1) to treatment with [177Lu]Lu-PSMA-617 (every 6 weeks for a maximum of six cycles; starting at 8·5 GBq, decreasing by 0.5 GBq to 6·0 GBq for the sixth cycle) versus cabazitaxel (20 mg/m2 every 3 weeks, maximum of ten cycles). Overall survival was analysed by intention-to-treat and summarised as restricted mean survival time (RMST) to account for non-proportional hazards, with a 36-month restriction time corresponding to median follow-up. This trial is registered with ClinicalTrials.gov, NCT03392428, and is complete. 291 men were registered from Feb 6, 2018, to Sept 3, 2019; after study imaging, 200 were eligible and randomly assigned to treatment with [177Lu]Lu-PSMA-617 (n=99) or cabazitaxel (n=101). After completing study treatment, 20 (20%) participants assigned to cabazitaxel and 32 (32%) assigned to [177Lu]Lu-PSMA-617 were subsequently treated with the alternative regimen. After a median follow-up of 35·7 months (IQR 31·1 to 39·2), 77 (78%) participants had died in the [177Lu]Lu-PSMA-617 group and 70 (69%) participants had died in the cabazitaxel group. Overall survival was similar among those assigned to [177Lu]Lu-PSMA-617 versus those assigned to cabazitaxel (RMST 19·1 months [95% CI 16·9 to 21·4] vs 19·6 months [17·4 to 21·8]; difference -0·5 months [95% CI -3·7 to 2·7]; p=0·77). No additional safety signals were identified with the longer follow-up in this analysis. 80 (27%) of 291 men who were registered after initial eligibility screening were excluded after [68Ga]Ga-PSMA-11 and 2-[18F]FDG PET. In the 61 of these men with follow-up available, RMST was 11·0 months (95% CI 9·0 to 13·1). These results support the use of [177Lu]Lu-PSMA-617 as an alternative to cabazitaxel for PSMA-positive metastatic castration-resistant prostate cancer progressing after docetaxel. We did not find evidence that overall survival differed between the randomised groups. Median overall survival was shorter for men who were excluded because of low PSMA expression or 2-[18F]FDG-discordant disease. Australian and New Zealand Urogenital and Prostate Cancer Trials Group, Prostate Cancer Foundation of Australia, Endocyte (a Novartis company), Australian Nuclear Science and Technology Organization, Movember, It's a Bloke Thing, CAN4CANCER, and The Distinguished Gentleman's Ride.

Tumoral Ki67 and PSMA Expression in Fresh Pre-PSMA-RLT Biopsies and Its Relation With PSMA-PET Imaging and Outcomes of PSMA-RLT in Patients With mCRPC.

Prostate specific membrane antigen (PSMA) directed radioligand therapy (RLT) is a novel therapy for metastatic castration-resistant prostate cancer (mCRPC) patients. However, it is still poorly understood why approximately 40% of the patients does not respond to PSMA-RLT. The aims of this study were to evaluate the pretreatment PSMA expression on immunohistochemistry (IHC) and PSMA uptake on PET/CT imaging in mCRPC patients who underwent PSMA-RLT. We correlated these parameters and a cell proliferation marker (Ki67) to the therapeutic efficacy of PSMA-RLT. In this retrospective study, mCRPC patients who underwent PSMA-RLT were analyzed. Patients biopsies were scored for immunohistochemical Ki67 expression, PSMA staining intensity and percentage of cells with PSMA expression. Moreover, the PSMA tracer uptake of the tumor lesion(s) and healthy organs on PET/CT imaging was assessed. The primary outcome was to evaluate the association between histological PSMA protein expression of tumor in pre-PSMA-RLT biopsies and the PSMA uptake on PSMA PET/CT imaging of the biopsied lesion. Secondary outcomes were to assess the relationship between PSMA expression and Ki67 on IHC and the progression free survival (PFS) and overall survival (OS) following PSMA-RLT. In total, 22 mCRPC patients were included in this study. Nineteen (86%) patients showed a high and homogenous PSMA expression of >80% on IHC. Three (14%) patients had low PSMA expression on IHC. Although there was limited PSMA uptake on PET/CT imaging, these 3 patients had lower PSMA uptake on PET/CT imaging compared to the patients with high PSMA expression on IHC. Yet, no correlation was found between PSMA uptake on PET/CT imaging and PSMA expression on IHC (SUVmax: R2=0.046 and SUVavg: R2=0.036). The 3 patients had a shorter PFS compared to the patients with high PSMA expression on IHC (HR: 4.76, 95% CI: 1.14-19.99; P=.033). Patients with low Ki67 expression had a longer PFS and OS compared to patients with a high Ki67 expression (HR: 0.40, 95% CI: 0.15-1.06; P=.013) CONCLUSION: The PSMA uptake on PSMA-PET/CT generally followed the PSMA expression on IHC. However, heterogeneity may be missed on PSMA-PET/CT. Immunohistochemical PSMA and Ki67 expression in fresh tumor biopsies, may contribute to predict treatment efficacy of PSMA-RLT in mCRPC patients. This needs to be further explored in prospective cohorts.

The role of PSMA PET/CT to predict upgrading in patients undergoing radical prostatectomy for ISUP grade group 1 prostate cancer.

To investigate the additive role of prostate-specific membrane antigen (PSMA) positron emission tomography/computed tomography (PET/CT) independent from multiparametric magnetic resonance imaging (mpMRI) and clinical-pathological parameters to predict pathological upgrading in patients with ISUP grade group (GG) 1 prostate cancer (PCa) at prostate biopsy. A total of 41 patients who underwent robotic radical prostatectomy (RP) for GG1 disease at prostate biopsy with preoperative PSMA PET/CT and mpMRI images available for central review were included in the study. Univariate and multivariate logistic regression analyses were performed to determine the independent predictors of pathological upgrading (GG ≥ 2). Final RP pathology revealed upgrading in 26 patients (65.9%); to GG 2 disease in 25 cases and GG 4 disease in one case. International Society of Urological Pathology (ISUP) upgrading rates for prostate imaging-reporting and data system (PIRADS)-5, PIRADS-4, and PIRADS ≤ 3 lesions were 78%, 74%, and 38%, respectively. Fourteen out of 15 (93.3%) patients with an SUVmax ≥ 5.6 and all patients with an SUVmax ≥ 6.5 (n = 10) had pathological upgrading. The upgrading rate in patients with SUV < 5.6 was 46.2% (12/26). Intraprostatic SUVmax ≥ 5.6 was found as the only independent predictor of pathological upgrading in multivariate analysis. High prostatic PSMA uptake was found to be a very reliable predictor of pathological upgrading, but low PSMA uptake cannot exclude pathological upgrading. Intraprostatic PSMA uptake along with previously known mpMRI and biopsy-related parameters should be considered when making a treatment decision in patients with GG1 PCa at prostate biopsy.

Improved Prostate-Specific Membrane Antigen (PSMA) Stimulation Using a Super Additive Effect of Dutasteride and Lovastatin In Vitro.

Prostate-specific membrane antigen (PSMA)-based imaging improved the detection of primary, recurrent and metastatic prostate cancer. However, in certain patients, a low PSMA surface expression can be a limitation for this promising diagnostic tool. Pharmacological induction of PSMA might be useful to further improve the detection rate of PSMA-based imaging. To achieve this, we tested dutasteride (Duta)-generally used for treatment of benign prostatic enlargement-and lovastatin (Lova)-a compound used to reduce blood lipid concentrations. We aimed to compare the individual effects of Duta and Lova on cell proliferation as well as PSMA expression. In addition, we tested if a combination treatment using lower concentrations of Duta and Lova can further induce PSMA expression. Our results show that a treatment with ≤1 μM Duta and ≥1 μM Lova lead to a significant upregulation of whole and cell surface PSMA expression in LNCaP, C4-2 and VCaP cells. Lower concentrations of Duta and Lova in combination (0.5 μM Duta + 0.5 μM Lova or 0.5 μM Duta + 1 μM Lova) were further capable of enhancing PSMA protein expression compared to a single compound treatment using higher concentrations in all tested cell lines (LNCaP, C4-2 and VCaP).

PET imaging of new target CDK19 in prostate cancer.

Prostate-specific membrane antigen (PSMA)-positron emission tomography (PET) is a superior method to predict patients' risk of cancer progression and response to specific therapies. However, its performance is limited for neuroendocrine prostate cancer (NEPC) and PSMA-low prostate cancer cells, resulting in diagnostic blind spots. Hence, identifying novel specific targets is our aim for diagnosing those prostate cancers with low PSMA expression. The Cancer Genome Atlas (TCGA) database and our cohorts from men with biopsy-proven high-risk metastatic prostate cancer were used to identify CDK19 and PSMA expression. PDX lines neP-09 and P-16 primary cells were used for cellular uptake and imaging mass cytometry in vitro. To evaluate in vivo CDK19-specific uptake of gallium(Ga)-68-IRM-015-DOTA, xenograft mice models and blocking assays were used. PET/CT imaging data were obtained to estimate the absorbed dose in organs. Our study group had reported the overexpression of a novel tissue-specific gene CDK19 in high-risk metastatic prostate cancer and CDK19 expression correlated with metastatic status and tumor staging, independently with PSMA and PSA levels. Following up on this new candidate for use in diagnostics, small molecules targeting CDK19 labeled with Ga-68 (68Ga-IRM-015-DOTA) were used for PET in this study. We found that the 68Ga-IRM-015-DOTA was specificity for prostate cancer cells, but the other cancer cells also took up little 68Ga-IRM-015-DOTA. Importantly, mouse imaging data showed that the NEPC and CRPC xenografts exhibited similar signal strength with 68Ga-IRM-015-DOTA, but 68Ga-PSMA-11 only stained the CRPC xenografts. Furthermore, target specificity was elucidated by a blocking experiment on a CDK19-bearing tumor xenograft. These data concluded that 68Ga-CDK19 PET/CT was an effective technology to detect lesions with or without PSMA in vitro, in vivo, and in the PDX model. Thus, we have generated a novel PET small molecule with predictive value for prostate cancer. The findings indicate that 68Ga-CDK19 may merit further evaluation as a predictive biomarker for PET scans in prospective cohorts and may facilitate the identification of molecular types of prostate cancer independent of PSMA.

Dual probe difference specimen imaging for prostate cancer margin assessment.

Positive margin status due to incomplete removal of tumor tissue during radical prostatectomy for high-risk localized prostate cancer requires reoperation or adjuvant therapy, which increases morbidity and mortality. Adverse effects of prostate cancer treatments commonly include erectile dysfunction, urinary incontinence, and bowel dysfunction, making successful initial curative prostatectomy imperative. Current intraoperative tumor margin assessment is largely limited to frozen section analysis, which is a lengthy, labor-intensive process that is obtrusive to the clinical workflow within the operating room (OR). Therefore, a rapid method for prostate cancer margin assessment in the OR could improve outcomes for patients. Dual probe difference specimen imaging (DDSI), which uses paired antibody-based probes that are labeled with spectrally distinct fluorophores, was shown herein for prostate cancer margin assessment. The paired antibody-based probes consisted of a targeted probe to prostate-specific membrane antigen (PSMA) and an untargeted probe, which were used as a cocktail to stain resected murine tissue specimens including prostate tumor, adipose, muscle, and normal prostate. Ratiometric images (i.e., DDSI) of the difference between targeted and untargeted probe uptake were calculated and evaluated for accuracy using receiver operator characteristic curve analysis with area under the curve values used to evaluate the utility of the DDSI method to detect PSMA positive prostate cancer. Targeted and untargeted probe uptake was similar between the high and low PSMA expressing tumor due to nonspecific probe uptake after topical administration. The ratiometric DDSI approach showed substantial contrast difference between the PSMA positive tumors and their respective normal tissues (prostate, adipose, muscle). Furthermore, DDSI showed substantial contrast difference between the high PSMA expressing tumors and the minimally PSMA expressing tumors due to the ratiometric correction for the nonspecific uptake patterns in resected tissues. Previous work has shown that ratiometic imaging has strong predictive value for breast cancer margin status using topical administration. Translation of the ratiometric DDSI methodology herein from breast to prostate cancers demonstrates it as a robust, ratiometric technique that provides a molecularly specific imaging modality for intraoperative margin detection. Using the validated DDSI protocol on resected prostate cancers permitted rapid and accurate assessment of PSMA status as a surrogate for prostate cancer margin status. Future studies will further evaluate the utility of this technology to quantitatively characterize prostate margin status using PSMA as a biomarker.

Design of Chitosan-Coated, Quercetin-Loaded PLGA Nanoparticles for Enhanced PSMA-Specific Activity on LnCap Prostate Cancer Cells.

Nanoparticles are designed to entrap drugs at a high concentration, escape clearance by the immune system, be selectively taken up by cancer cells, and release bioactives in a rate-modulated manner. In this study, quercetin-loaded PLGA nanoparticles were prepared and optimized to determine whether coating with chitosan would increase the cellular uptake of the nanoparticles and if the targeting ability of folic acid as a ligand can provide selective toxicity and enhanced uptake in model LnCap prostate cancer cells, which express high levels of the receptor prostate-specific membrane antigen (PSMA), compared to PC-3 cells, that have relatively low PSMA expression. A design of experiments approach was used to optimize the PLGA nanoparticles to have the maximum quercetin loading, optimal cationic charge, and folic acid coating. We examined the in vitro release of quercetin and comparative cytotoxicity and cellular uptake of the optimized PLGA nanoparticles and revealed that the targeted nano-system provided sustained, pH-dependent quercetin release, and higher cytotoxicity and cellular uptake, compared to the non-targeted nano-system on LnCap cells. There was no significant difference in the cytotoxicity or cellular uptake between the targeted and non-targeted nano-systems on PC-3 cells (featured by low levels of PSMA), pointing to a PSMA-specific mechanism of action of the targeted nano-system. The findings suggest that the nano-system can be used as an efficient nanocarrier for the targeted delivery and release of quercetin (and other similar chemotherapeutics) against prostate cancer cells.

PD04-04 MOLECULAR CORRELATES WITH PSMA EXPRESSION IN PROSTATE CANCER

You have accessJournal of UrologyCME1 Apr 2023PD04-04 MOLECULAR CORRELATES WITH PSMA EXPRESSION IN PROSTATE CANCER Adam Weiner, Eric Li, JJ Zhang, Elai Davicioni, Edward Schaeffer, Ashley Ross, Luca Valle, Paul Boutros, Jeremie Calais, Amar Kishan, and Robert Reiter Adam WeinerAdam Weiner More articles by this author , Eric LiEric Li More articles by this author , JJ ZhangJJ Zhang More articles by this author , Elai DavicioniElai Davicioni More articles by this author , Edward SchaefferEdward Schaeffer More articles by this author , Ashley RossAshley Ross More articles by this author , Luca ValleLuca Valle More articles by this author , Paul BoutrosPaul Boutros More articles by this author , Jeremie CalaisJeremie Calais More articles by this author , Amar KishanAmar Kishan More articles by this author , and Robert ReiterRobert Reiter More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000003228.04AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: Not all prostate cancer (PCa) is detected by prostate-specific membrane antigen (PSMA)-based imaging or responsive to PSMA-based radiopharmaceuticals. We sought to define the molecular processes associated with PSMA expression. METHODS: Using multiple datasets (n=5 Homo sapiens; n=2 mouse xenograft models; n=1 cell line), we correlated PSMA gene expression (FOLH1) with biological processes and treatments. RESULTS: In an exploratory analysis of a prospective cohort of 7,000 tumors from radical prostatectomy, tumors with high PSMA RNA expression (one standard deviation above mean) tended to demonstrate more androgen receptor activity, high genomic risk scores (Decipher), more markers of homologous recombination deficiency, less immune content, lower predicted response to radiotherapy (“PORTOS”), and enrichment for P13K/AKT/mTOR pathways (Figure 1). In a validation cohort, adenocarcinoma tumors (n=49) expressed more PSMA than benign tissue (n=12; Wilcoxon p=0.020) and castration resistant tumors (n=27; p=0.015). An additional cohort showed adenocarcinoma (n=110) expressed more PSMA than neuroendocrine tumors (n=20; p=4.4e-6). In a mouse xenograft model (n=1) of high-grade adenocarcinoma, PSMA expression declined as the model underwent conversion to castration resistance and subsequent neuroendocrine transformation following castration. From both mouse and human data, treatment with androgen deprivation was associated with an initial increase in PSMA expression. From TCGA (n=491), tumors with high PSMA expression also tended to have a higher mutational burden and fewer tumor infiltrating lymphocytes in a subset with immunohistochemistry data (n=330). To assess the association between PSMA and P13K/AKT/mTOR, we used data from a cell line exposed to the MAPK inhibitor trametinib which upregulates P13K/AKT/mTOR pathways. VCaP cells treated with both enzalutamide and trametinib expressed two-fold more PSMA compared to those treated with the individual medications or neither. CONCLUSIONS: PCa with high PSMA expression is characterized by relevant differences in biological processes. If corroborated with PSMA-PET avidity, these results could optimize precision PCa care by informing adjunctive molecular testing or treatment paradigms for low or high PSMA expressing tumors. Source of Funding: None © 2023 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 209Issue Supplement 4April 2023Page: e143 Advertisement Copyright & Permissions© 2023 by American Urological Association Education and Research, Inc.MetricsAuthor Information Adam Weiner More articles by this author Eric Li More articles by this author JJ Zhang More articles by this author Elai Davicioni More articles by this author Edward Schaeffer More articles by this author Ashley Ross More articles by this author Luca Valle More articles by this author Paul Boutros More articles by this author Jeremie Calais More articles by this author Amar Kishan More articles by this author Robert Reiter More articles by this author Expand All Advertisement PDF downloadLoading ...

99mTc-Labelled Low Molecular Weight Inhibitors of Prostate-Specific Membrane Antigen

High morbidity and mortality rates of prostate cancer (PCa) determine the requirement of looking for new methods of its early diagnosis. Methods of nuclear medicine have a special place in addressing this problem as they allow functional, metabolic and other processes imaging in body, which occur during the cancer development. This approach supposes the use of radiopharmaceuticals (RP), which are capable of selective binding to a specific biological target, for example, prostate-specific membrane antigen (PSMA), which is known to be overexpressed in PCa. Current development of new radiotracers for PCa imaging is focused on low molecular weight PSMA inhibitors due to their high specific binding to PSMA and rapid urinary excretion. Technetium-99m remains the appropriate radionuclide for diagnostic studies due to its optimal nuclear properties, ease of production and versatile coordination chemistry. Therefore, single-photon emission computed tomography (SPECT) imaging with 99mTc-PSMA radioligands can be a cost effective alternative to PET with 68Ga- or 18F-labeled RP. The aim of this review is to summarize and analyze currently available data on 99mTc-labeled low molecular weight PSMA inhibitors for metastatic PCa imaging.

Low TLR and PSMA-TV predict biochemical response to abiraterone acetate in metastatic prostate cancer patients developing castration resistance after chemohormonal therapy at hormone-sensitive stage.

To explore whether 68Ga-PSMA-11 PET/CT-derived parameters could predict biochemical response to abiraterone acetate (AA) treatment and prognosis in metastatic prostate cancer patients developing castration resistance after chemohormonal therapy at hormone-sensitive stage. The clinicopathologic data of 106 mCRPC cases receiving AA treatment were retrospectively analyzed. Logistic regression analysis was used to determine the independent predictors of biochemical response to AA treatment. Cox analyses were applied to investigate the independent prognostic factors for time to biochemical progression (TTBP) and radiological progression-free survival (rPFS). Survival analysis and ROC curve were also used. Multivariable Logistic analysis demonstrated that prior ADT duration ≥ 12months, low prostate specific membrane antigen receptor-expressing tumor volume (PSMA-TV), low tumor to liver ratio (TLR) were independent predictors of biochemical response to AA treatment. Multivariate Cox analysis demonstrated that low PSMA-TV and low TLR were independent prognostic factors of longer TTBP and rPFS. The TTBP and rPFS of patients with higher PSMA-TV or TLR were significantly decreased compared with that of patients with lower PSMA-TV and TLR. The area under ROC curve (AUC) of combining ADT duration, PSMA-TV and TLR was 0.82 for predicting biochemical response to AA, which was significantly increased compared with that of other 68Ga-PSMA-11 PET/CT-derived parameters alone. Low PSMA-TV, low TLR were vital independent predictors of biochemical response to AA treatment and were associated with preferable prognosis in mCRPC patients. Combining ADT duration, PSMA-TV and TLR performed well in distinguishing AA responders from non-responders in mCRPC patients.

Expression of prostate-specific membrane antigen in the neovasculature of primary tumors and lymph node metastasis of laryngeal squamous cell carcinomas.

BackgroundProstate-specific membrane antigen (PSMA) expression is encountered in tumor-associated neovascularization.MethodsPSMA-antibody was applied to the paraffin blocks of 51 patients who were diagnosed with squamous cell carcinoma of the larynx and underwent laryngectomy and one who underwent lymph node dissection. The percentage of vascular expression in tumoral and extratumoral stroma and lymph nodes and intensity score in tumoral epithelium were evaluated and divided into groups according to the level of PSMA expression. Final PSMA expression was determined by multiplying intensity and percentage scores.ResultsThe mean age was 61±10 years. Patients with perineural invasion, cartilage invasion, and local invasion exhibited higher PSMA expression scores. Age, tumor differentiation, tumor diameter, perineural invasion, tumor localization, capsular invasion, depth of invasion, surgical margin status, local invasion, nodal metastasis, TNM classification, and stage were similar in high and low PSMA expression groups. There was no PSMA expression in extratumoral vascular stroma. Significantly higher PSMA expression was observed in the vascular endothelium of metastatic lymph nodes compared with reactive lymph nodes. Patients with advanced-stage disease exhibited higher PSMA vascular expression scores compared to those with earlier stages (p<.001). PSMA expression was not correlated with overall survival, disease-specific survival, or disease-free survival (p>.05).ConclusionsOur study suggests that higher PSMA expression is associated with cartilage invasion, local invasion, and advanced-stage of disease. PSMA expression can be utilized for detection of lymph node metastasis and has some predictive role in cases of neck metastasis.

A Review on the Current State and Future Perspectives of [99mTc]Tc-Housed PSMA-i in Prostate Cancer.

Recently, prostate-specific membrane antigen (PSMA) has gained momentum in tumor nuclear molecular imaging as an excellent target for both the diagnosis and therapy of prostate cancer. Since 2008, after years of preclinical research efforts, a plentitude of radiolabeled compounds mainly based on low molecular weight PSMA inhibitors (PSMA-i) have been described for imaging and theranostic applications, and some of them have been transferred to the clinic. Most of these compounds include radiometals (e.g., 68Ga, 64Cu, 177Lu) for positron emission tomography (PET) imaging or endoradiotherapy. Nowadays, although the development of new PET tracers has caused a significant drop in single-photon emission tomography (SPECT) research programs and the development of new technetium-99m (99mTc) tracers is rare, this radionuclide remains the best atom for SPECT imaging owing to its ideal physical decay properties, convenient availability, and rich and versatile coordination chemistry. Indeed, 99mTc still plays a relevant role in diagnostic nuclear medicine, as the number of clinical examinations based on 99mTc outscores that of PET agents and 99mTc-PSMA SPECT/CT may be a cost-effective alternative for 68Ga-PSMA PET/CT. This review aims to give an overview of the specific features of the developed [99mTc]Tc-tagged PSMA agents with particular attention to [99mTc]Tc-PSMA-i. The chemical and pharmacological properties of the latter will be compared and discussed, highlighting the pros and cons with respect to [68Ga]Ga-PSMA11.

18F-Prostate-Specific Membrane Antigen and 18F-Fluorodeoxyglucose PET/CT Unmasked the Characteristics of Prostate Lymphoma: A Case Report and Literature Review

Prostate lymphoma (PL) is rarely observed and may be concurrently presented with prostate adenocarcinoma. Moreover, the appearance of PL on conventional imaging is similar with prostate adenocarcinoma. Thus, most of PL is diagnosed through prostate biopsy, or accidentally found in the specimens of surgery. Prostate-specific membrane antigen (PSMA) PET/CT has improved the management of prostate adenocarcinoma. While, the question regarding whether it benefits the discovery of the characteristics of PL is unknown. A 32-year-old man presented with worsening dysuria for 1 month, and the prostate-specific antigen (PSA) concentration was normal. While the pelvic MRI showed a mass in the prostate and multiple enlarged lymph nodes in the bilateral inguinal area. Then, the diagnosis of prostate adenocarcinoma was considered, but the serum PSA was normal and he was younger than most patients. So, 18F-PSMA PET/CT was then performed to further reveal the characteristics of the lesion and guide biopsy. However, there was no abnormal PSMA uptake in the lesion of the prostate and lymph nodes of the pelvic cavity and bilateral inguinal area. These lesions presented with increased glucose metabolism on fluorodeoxyglucose (FDG) PET/CT, and the prostate biopsy was then performed. PL was confirmed based on the results of the histopathologic examination, and the patient subsequently received systemic chemotherapy plus radiotherapy. Fortunately, the symptoms and the lesions completely disappeared after radiotherapy. The clinical symptoms of PL are atypical, and PL and adenocarcinoma may be concurrently presented. Moreover, distinguishing PL from prostate adenocarcinoma based on the appearance of conventional imaging is difficult. As opposed to prostate adenocarcinoma, a high FDG-avidity and low PSMA uptake by lymphoma either in the prostate or metastases are seen. So, PSMA PET/CT combined with FDG PET/CT can non-invasively identify the characteristics and origin of PL.

Prostate-Specific Membrane Antigen (PSMA) Expression in Tumor-Associated Neovasculature Is an Independent Prognostic Marker in Patients with Ovarian Cancer.

Prostate-specific membrane antigen (PSMA) is present in the tumor-associated neovasculature of many cancer types. Current data in ovarian cancer are limited and controversial; thus, the aim of this study was to investigate PSMA expression in a larger and homogenous patient cohort. This might lead to further studies investigating the use of imaging and therapeutic modalities targeting PSMA. Eighty patients with advanced stage high-grade serous ovarian cancers were included. Using immunohistochemistry, PSMA and CD31, a marker for endothelial cells, were examined in whole tissue sections. Percentage and intensity of PSMA expression were determined in the neovasculature. Expression levels were correlated with clinicopathological parameters and survival. Low (≤10%), medium (20–80%), and high (≥90%) PSMA expression was found in 14, 46, and 20 ovarian cancer samples, respectively. PSMA expression was confined to tumor-associated neovasculature and significantly correlated with progression-free (HR 2.24, 95% CI 1.32–3.82, p = 0.003) and overall survival (HR 2.73, 95% CI 1.41–5.29, p = 0.003) in multivariate models, considering age, FIGO stage, and residual disease. This is the first study showing a clinical relevance for PSMA in patients with ovarian cancer. PSMA was detected in the vast majority of cancer samples and showed an impact on survival.

Clinical and molecular features of low prostate-specific membrane antigen (PSMA) expression in patients (pts) with metastatic castration resistant prostate cancer (mCRPC).

167 Background: Low PSMA uptake on positron-emission tomography is seen in up to 30% of mCRPC pts and represents a clinically distinct subgroup with adverse outcomes. We assessed transcriptional and clinical features associated with low PSMA ( FOLH1) gene expression in mCRPC. Methods: A retrospective analysis of mCRPC biopsy samples with RNA-seq data was undertaken. Normalized FOLH1 expression was compared across histologic subtypes and sites of disease. We assessed the association between FOLH1 expression, selected androgen receptor (AR) target genes, master regulators of neuroendocrine differentiation, and previously validated AR activity and treatment-associated small cell neuroendocrine carcinoma (t-SCNC) transcriptional signature scores using Pearson correlations. Associations between FOLH1 and both PSA50 response to subsequent AR-targeted therapy and overall survival (OS) were examined by logistic regression and Cox proportional hazard models, respectively. Results: Samples from 97 pts were identified, of which 18% harbored t-SCNC histology. 45% of pts had visceral metastases at the time of biopsy, and 41% received subsequent AR-targeted therapy. Median FOLH1 expression was lower in pts with visceral metastases vs no visceral metastases (14.7 vs 15.6, p = 0.02) but was not significantly different across t-SCNC vs adenocarcinoma biopsies (14.3 vs 15.4, p = 0.13). FOLH1 expression was positively correlated with AR transcriptional activity and AR target genes, and negatively correlated with master regulators of neuroendocrine differentiation and t-SCNC transcriptional signature scores (Table). Low FOLH1 expression did not predict PSA50 response to subsequent AR-targeted therapy (OR 0.97, p = 0.8), but was associated with shorter OS on univariate analysis (HR 1.09, 95% CI 1.02-1.16, p=0.01). A post-hoc analysis revealed a trend towards decreased median OS in pts with FOLH1 expression &lt;12 (7.5 vs 17.1 months, log-rank p = 0.06). Conclusions: In this retrospective analysis of mCRPC pts, low FOLH1 expression was associated with transcriptional features of t-SCNC, decreased AR activity, and shorter OS. These findings are hypothesis-generating and prospective validation is needed.[Table: see text]