Prostate-specific membrane antigen cleavage of vitamin B9 stimulates oncogenic signaling through metabotropic glutamate receptors

Treatment Response Imaging in Prostate Cancer

Objective criteria for measuring treatment response in prostate cancer are critical to clinical research and practice. The Prostate Cancer Working Group 3 criteria are widely accepted relying only on conventional imaging for radiographic treatment response. Prostate-specific membrane antigen PET/computed tomography was proven to be superior to conventional imaging in initial diagnosis and biochemical recurrence of prostate cancer. Moreover, there is growing evidence of its role in treatment response assessment in prostate cancer. This study will review the different criteria for imaging treatment response on conventional and advanced molecular imaging for different therapies, and the future perspective in posttherapy imaging.

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

BACKGROUND

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

PSMA-targeted radiotheranostics in modern nuclear medicine: then, now, and what of the future?

In 1853, the perception of prostate cancer (PCa) as a rare ailment prevailed, was described by the eminent Londoner surgeon John Adams. Rapidly forward to 2018, the landscape dramatically altered. Currently, men face a one-in-nine lifetime risk of PCa, accentuated by improved diagnostic methods and an ageing population. With more than three million men in the United States alone grappling with this disease, the overall risk of succumbing to stands at one in 39. The intricate clinical and biological diversity of PCa poses serious challenges in terms of imaging, ongoing monitoring, and disease management. In the field of theranostics, diagnostic and therapeutic approaches that harmoniously merge targeted imaging with treatments are integrated. A pivotal player in this arena is radiotheranostics, employing radionuclides for both imaging and therapy, with prostate-specific membrane antigen (PSMA) at the forefront. Clinical milestones have been reached, including FDA- and/or EMA-approved PSMA-targeted radiodiagnostic agents, such as [18F]DCFPyL (PYLARIFY®, Lantheus Holdings), [18F]rhPSMA-7.3 (POSLUMA®, Blue Earth Diagnostics) and [68Ga]Ga-PSMA-11 (Locametz®, Novartis/ ILLUCCIX®, Telix Pharmaceuticals), as well as PSMA-targeted radiotherapeutic agents, such as [177Lu]Lu-PSMA-617 (Pluvicto®, Novartis). Concurrently, ligand-drug and immune therapies designed to target PSMA are being advanced through rigorous preclinical research and clinical trials. This review delves into the annals of PSMA-targeted radiotheranostics, exploring its historical evolution as a signature molecule in PCa management. We scrutinise its clinical ramifications, acknowledge its limitations, and peer into the avenues that need further exploration. In the crucible of scientific inquiry, we aim to illuminate the path toward a future where the enigma of PCa is deciphered and where its menace is met with precise and effective countermeasures. In the following sections, we discuss the intriguing terrain of PCa radiotheranostics through the lens of PSMA, with the fervent hope of advancing our understanding and enhancing clinical practice.

[177Lu]Lu-PSMA-617 plus enzalutamide in patients with metastatic castration-resistant prostate cancer (ENZA-p): an open-label, multicentre, randomised, phase 2 trial

BACKGROUND

Enzalutamide and lutetium-177 [177Lu]Lu-prostate-specific membrane antigen (PSMA)-617 both improve overall survival in patients with metastatic castration-resistant prostate cancer. Androgen and PSMA receptors have a close intracellular relationship, with data suggesting complementary benefit if targeted concurrently. In this study, we assessed the activity and safety of enzalutamide plus adaptive-dosed [177Lu]Lu-PSMA-617 versus enzalutamide alone as first-line treatment for metastatic castration-resistant prostate cancer.

METHODS

ENZA-p was an open-label, randomised, controlled phase 2 trial done at 15 hospitals in Australia. Participants were men aged 18 years or older with metastatic castration-resistant prostate cancer not previously treated with docetaxel or androgen receptor pathway inhibitors for metastatic castration-resistant prostate cancer, gallium-68 [68Ga]Ga-PSMA-PET-CT (PSMA-PET-CT) positive disease, Eastern Cooperative Oncology Group performance status of 0-2, and at least two risk factors for early progression on enzalutamide. Participants were randomly assigned (1:1) by a centralised, web-based system using minimisation with a random component to stratify for study site, disease burden, use of early docetaxel, and previous treatment with abiraterone acetate. Patients were either given oral enzalutamide 160 mg daily alone or with adaptive-dosed (two or four doses) intravenous 7·5 GBq [177Lu]Lu-PSMA-617 every 6-8 weeks dependent on an interim PSMA-PET-CT (week 12). The primary endpoint was prostate-specific antigen (PSA) progression-free survival, defined as the interval from the date of randomisation to the date of first evidence of PSA progression, commencement of non-protocol anticancer therapy, or death. The analysis was done in the intention-to-treat population, using stratified Cox proportional hazards regression. This trial is registered with ClinicalTrials.gov, NCT04419402, and participant follow-up is ongoing.

FINDINGS

162 participants were randomly assigned between Aug 17, 2020, and July 26, 2022. 83 men were assigned to the enzalutamide plus [177Lu]Lu-PSMA-617 group, and 79 were assigned to the enzalutamide group. Median follow-up in this interim analysis was 20 months (IQR 18-21), with 32 (39%) of 83 patients in the enzalutamide plus [177Lu]Lu-PSMA-617 group and 16 (20%) of 79 patients in the enzalutamide group remaining on treatment at the data cutoff date. Median age was 71 years (IQR 64-76). Median PSA progression-free survival was 13·0 months (95% CI 11·0-17·0) in the enzalutamide plus [177Lu]Lu-PSMA-617 group and 7·8 months (95% CI 4·3-11·0) in the enzalutamide group (hazard ratio 0·43, 95% CI 0·29-0·63, p<0·0001). The most common adverse events (all grades) were fatigue (61 [75%] of 81 patients), nausea (38 [47%]), and dry mouth (32 [40%]) in the enzalutamide plus [177Lu]Lu-PSMA-617 group and fatigue (55 [70%] of 79), nausea (21 [27%]), and constipation (18 [23%]) in the enzalutamide group. Grade 3-5 adverse events occurred in 32 (40%) of 81 patients in the enzalutamide plus [177Lu]Lu-PSMA-617 group and 32 (41%) of 79 patients in the enzalutamide group. Grade 3 events that occurred only in the enzalutamide plus [177Lu]Lu-PSMA-617 group included anaemia (three [4%] of 81 participants) and decreased platelet count (one [1%] participant). No grade 4 or 5 events were attributed to treatment on central review in either group.

INTERPRETATION

The addition of [177Lu]Lu-PSMA-617 to enzalutamide improved PSA progression-free survival providing evidence of enhanced anticancer activity in patients with metastatic castration-resistant prostate cancer with risk factors for early progression on enzalutamide and warrants further evaluation of the combination more broadly in metastatic prostate cancer.

FUNDING

Prostate Cancer Research Alliance (Movember and Australian Federal Government), St Vincent's Clinic Foundation, GenesisCare, Roy Morgan Research, and Endocyte (a Novartis company).

Exploring the role of combined external beam radiotherapy and targeted radioligand therapy with [177Lu]Lu-PSMA-617 for prostate cancer - from bench to bedside

Management of prostate cancer (PC) might be improved by combining external beam radiotherapy (EBRT) and prostate-specific membrane antigen (PSMA)-targeted radioligand therapy (RLT) with lutetium-177 (177Lu)-labeled PSMA inhibitors. We hypothesized a higher efficacy of the combination due to augmentation of the radiation dose to the tumor and interactions of EBRT with PSMA expression potentially increasing radiopharmaceutical uptake. Therefore, this study analyzed the influence of radiation on PSMA expression levels in vitro. The results were translated to evaluate the efficacy of the combination of photon EBRT and [177Lu]Lu-PSMA-617 in a murine PC xenograft model. Finally, a clinical case report on a combined elective field EBRT with RLT dose escalation illustrates a proof-of-concept. Methods: PSMA gene and protein expression were assessed in human PSMA-overexpressing LNCaP cells after irradiation using reverse transcription quantitative polymerase chain reaction (RT-qPCR), flow cytometry and On-Cell Western assays. In the in vivo therapy study, LNCaP tumor-bearing BALB/c nu/nu mice were irradiated once with 2 Gy X-ray EBRT and injected with 40 MBq [177Lu]Lu-PSMA-617 after 4 h or received single or no treatment (n = 10 each). Tumor-absorbed doses by [177Lu]Lu-PSMA-617 were calculated according to the Medical Internal Radiation Dosimetry (MIRD) formalism after deriving time-activity curves using a gamma probe. An exemplified patient case is demonstrated where fractionated EBRT (54 Gy to prostate; 45 Gy to pelvic lymphatics) and three cycles of [177Lu]Lu-PSMA-617 (3.4-6.0 GBq per cycle) were sequentially combined under concurrent androgen deprivation for treating locally advanced PC. Results: At 4 h following irradiation with 2-8 Gy, LNCaP cells displayed a PSMA protein upregulation by around 18% relative to non-irradiated cells, and a stronger upregulation on mRNA level (up to 2.6-fold). This effect was reversed by 24 h when PSMA protein levels were downregulated by up to 22%. Mice treated with the combination therapy showed significantly improved outcomes regarding tumor control and median survival (p < 0.0001) as compared to single or no treatment. Relative to monotherapy with PSMA-RLT or EBRT, the tumor doubling time was prolonged 1.7- or 2.7-fold and the median survival was extended by 24% or 60% with the combination, respectively. Additionally, tumors treated with EBRT exhibited a 14% higher uptake of the radiopharmaceutical as evident from the calculated tumor-absorbed dose, albeit with high variability in the data. Concerning the patient case, the tri-modality treatment was well tolerated and the patient responded with a long-lasting complete biochemical remission for five years following end of PSMA-RLT. The patient then developed a biochemical relapse with oligo-recurrent disease on follow-up imaging. Conclusion: The present preclinical and clinical data demonstrate that the combination of EBRT with dose escalation by PSMA-RLT improves tumor control and potentially prolongs survival. This may pave the way for further clinical investigations of this approach to explore the curative potential of the combination therapy.

The CONFIRM trial protocol: the utility of prostate-specific membrane antigen positron emission tomography/computed tomography in active surveillance for prostate cancer

OBJECTIVES

Primary objectives: To determine the additive value of prostate-specific membrane antigen (PSMA) positron emission tomography/computed tomography (PET/CT) in the risk stratification of men with newly diagnosed prostate cancer (PCa) who would have otherwise been deemed suitable for active surveillance (AS). Specifically, we aim to determine if PSMA PET/CT can detect a cohort of men on AS that are in fact high risk and likely to experience unfavourable outcomes should they remain on their current treatment pathway.

SECONDARY OBJECTIVES

to determine the additive value of PSMA PET/CT to repeat multiparametric magnetic resonance imaging (mpMRI) of the prostate and explore whether a confirmatory biopsy may be avoided in men with a negative PSMA PET/CT and a negative repeat mpMRI of the prostate (Prostate Imaging-Reporting and Data System score of <3). Furthermore, to develop a nomogram combining clinical, imaging and biomarker data to predict the likelihood of failure on AS in men with high-risk features. Also, a blood sample will be taken to perform a Prostate Health Index test at the time of confirmatory biopsy. Furthermore, a portion of this blood will be stored at a biobank for up to 5 years if a follow-up study on molecular biomarkers and genetic assays in this cohort of men is indicated, based on the results from the CONFIRM trial.

PATIENTS AND METHODS

The CONFIRM trial is a prospective, multicentre, pre-test/post-test, cohort study across Victoria, Australia, involving men with newly diagnosed low-risk PCa with high-risk features, considered suitable for AS and undergoing confirmatory biopsy. The trial's goal is to provide high-quality evidence to establish whether PSMA PET/CT has a role in risk-stratifying men deemed suitable for AS despite having high-risk feature(s).

RESULTS

The CONFIRM trial will measure the proportion of men deemed unsuitable for ongoing AS based on pathological upgrading and multidisciplinary team recommendation due to PSMA PET/CT scan and PSMA-targeted confirmatory biopsy. Additionally, the positive and negative predictive values, sensitivity, and specificity of PSMA PET/CT will be calculated in isolation and combined with repeat mpMRI of the prostate.

CONCLUSIONS

This trial will provide robust prospective data to determine if PSMA-PET/CT and standard of care (prostate biopsy ± repeat mpMRI) can improve diagnostic certainty in men undergoing confirmatory biopsy for low-grade PCa with high-risk features.

Theranostics - a sure cure for cancer after 100 years?

Cancer has remained a formidable challenge in medicine and has claimed an enormous number of lives worldwide. Theranostics, combining diagnostic methods with personalized therapeutic approaches, shows huge potential to advance the battle against cancer. This review aims to provide an overview of theranostics in oncology: exploring its history, current advances, challenges, and prospects. We present the fundamental evolution of theranostics from radiotherapeutics, cellular therapeutics, and nanotherapeutics, showcasing critical milestones in the last decade. From the early concept of targeted drug delivery to the emergence of personalized medicine, theranostics has benefited from advances in imaging technologies, molecular biology, and nanomedicine. Furthermore, we emphasize pertinent illustrations showcasing that revolutionary strategies in cancer management enhance diagnostic accuracy and provide targeted therapies customized for individual patients, thereby facilitating the implementation of personalized medicine. Finally, we describe future perspectives on current challenges, emerging topics, and advances in the field.

Neoadjuvant chemohormonal therapy before radical prostatectomy in high-risk prostate cancer: a mini-review

High-risk localized prostate cancer (PCa) has the potential of recurrence and progression to a lethal phenotype, and neoadjuvant therapy followed by radical prostatectomy (RP) may be an option for these patients. Docetaxel has been recently shown to be an effective chemotherapeutic agent for high-volume metastatic hormone-sensitive PCa and metastatic castration-resistant PCa, and these increased efficacy create the impetus to assess the potential role of preoperative docetaxel in high-risk localized PCa. In this mini-review, we found that neoadjuvant chemohormonal therapy (NCHT) may be an effective neoadjuvant regimen to improve oncological outcome of high-risk PCa. However, the addition of docetaxel in the neoadjuvant setting would unavoidably increase the rate of adverse events, impose additional economic burdens. Therefore, suitable patient selection is crucial and pathological response might be a surrogate endpoint. Furthermore, we also found that molecular imaging prostate-specific membrane antigen (PSMA) PET/CT was a promising tool to evaluation the effectiveness of NCHT, and the expression status of AR, AR-V7, Ki-67, PTEN and TP53 might be helpful for urologists to identify more suitable candidates for NCHT.

Synthesis and Preclinical Evaluation of Two Novel 68Ga-Labeled Bispecific PSMA/FAP-Targeted Tracers with 2-Nal-Containing PSMA-Targeted Pharmacophore and Pyridine-Based FAP-Targeted Pharmacophore

Some bispecific radiotracers have been developed to overcome the limitations of monospecific tracers and improve detection sensitivity for heterogeneous tumor lesions. Here, we aim to synthesize two bispecific tracers targeting prostate-specific membrane antigen (PSMA) and fibroblast activation protein (FAP), which are key markers expressed in prostate cancer. A pyridine-based FAP-targeted ligand was synthesized through multi-step organic synthesis and then connected to the 2-Nal-containing PSMA-targeted motif. The Ki(PSMA) values of Ga-complexed bispecific ligands, Ga-AV01084 and Ga-AV01088, were 11.6 ± 3.25 and 28.7 ± 6.05 nM, respectively, and the IC50(FAP) values of Ga-AV01084 and Ga-AV01088 were 10.9 ± 0.67 and 16.7 ± 1.53 nM, respectively. Both [68Ga]Ga-AV01084 and [68Ga]Ga-AV01088 enabled the visualization of PSMA-expressing LNCaP tumor xenografts and FAP-expressing HEK293T:hFAP tumor xenografts in PET images acquired at 1 h post-injection. However, the tumor uptake values from the bispecific tracers were still lower than those obtained from the monospecific tracers, PSMA-targeted [68Ga]Ga-PSMA-617 and FAP-targeted [68Ga]Ga-AV02070. Further investigations are needed to optimize the selection of linkers and targeted pharmacophores to improve the tumor uptake of bispecific PSMA/FAP tracers for prostate cancer imaging.

The Dedicated Imaging Post-Prostatectomy for Enhanced Radiotherapy outcomes (DIPPER) trial protocol: a multicentre, randomised trial of salvage radiotherapy versus surveillance for low-risk biochemical recurrence after radical prostatectomy

BACKGROUND

Salvage radiation therapy (SRT) and surveillance for low-risk prostate-specific antigen (PSA) recurrence have competing risks and benefits. The efficacy of early SRT to the prostate bed with or without pelvic lymph nodes compared to surveillance in patients with PSA recurrence after radical prostatectomy and no identifiable recurrent disease evident on prostate specific membrane antigen-positron emission tomography/computer tomography (PSMA-PET/CT) is unknown.

STUDY DESIGN

The Dedicated Imaging Post-Prostatectomy for Enhanced Radiotherapy outcomes (DIPPER) is an open-label, multicentre, randomised Phase II trial.

ENDPOINTS

The primary endpoint is 3-year event-free survival, with events comprising one of PSA recurrence (PSA ≥0.2 ng/mL higher than baseline), radiological evidence of metastatic disease, or initiation of systemic or other salvage treatments. Secondary endpoints include patient-reported outcomes, treatment patterns, participant perceptions, and cost-effectiveness.

ELIGIBILITY CRITERIA

Eligible participants have PSA recurrence of prostate cancer after radical prostatectomy, defined by serum PSA level of 0.2-0.5 ng/mL, deemed low risk according to modified European Association of Urology biochemical recurrence risk criteria (International Society for Urological Pathology Grade Group ≤2, PSA doubling time >12 months), with no definite/probable recurrent prostate cancer on PSMA-PET/CT.

PATIENTS AND METHODS

A total of 100 participants will be recruited from five Australian centres and randomised 1:1 to SRT or surveillance. Participants will undergo 6-monthly clinical evaluation for up to 36 months. Androgen-deprivation therapy is not permissible. Enrolment commenced May 2023.

TRIAL REGISTRATION

This trial has been registered with the Australian New Zealand Clinical Trials Registry (ACTRN: ACTRN12622001478707).

Nomogram to predict the presence of PSMA-negative but FDG-positive lesion in castration-resistant prostate cancer: a multicenter cohort study

Background

PSMA-negative but FDG-positive (PSMA-/FDG+) lesion in dual-tracer (68Ga-PSMA and 18F-FDG) positron emission tomography/computed tomography (PET/CT) is associated with an unfavorable response to Lutetium-177 (177Lu)-PSMA-617. This study sought to develop both radiomics and clinical models for the precise prediction of the presence of PSMA-/FDG+ lesions in patients with castration-resistant prostate cancer (CPRC).

Methods

A cohort of 298 patients who underwent dual-tracer PET/CT with a less than 5-day interval was included. The evaluation of the prognostic performance of the radiomics model drew upon the survival data derived from 40 patients with CRPC treated with 177Lu-PSMA-617 in an external cohort. Two endpoints were evaluated: (a) prostate-specific antigen (PSA) response rate, defined as a reduction exceeding 50% from baseline and (b) overall survival (OS), measured from the initiation of 177Lu-PSMA-617 to death from any cause.

Results

PSMA-/FDG+ lesions were identified in 56 (18.8%) CRPC patients. Both radiomics (area under the curve [AUC], 0.83) and clinical models (AUC, 0.78) demonstrated robust performance in PSMA-/FDG+ lesion prediction. Decision curve analysis revealed that the radiomics model yielded a net benefit over the 'screen all' strategy at a threshold probability of ⩾4%. At a 5% probability threshold, the radiomics model facilitated a 21% reduction in 18F-FDG PET/CT scans while only missing 2% of PSMA-/FDG+ cases. Patients with a low estimated score exhibited significantly prolonged OS (hazard ratio = 0.49, p = 0.029) and a higher PSA response rate (75% versus 35%, p = 0.011) compared to those with a high estimated score.

Conclusion

This study successfully developed two models with accurate estimations of the risk associated with PSMA-/FDG+ lesions in CRPC patients. These models held potential utility in aiding the selection of candidates for 177Lu-PSMA-617 treatment and guiding 68Ga-PSMA PET/CT-directed radiotherapy.

Reproducibility and Accuracy of the PRIMARY Score on PSMA PET and of PI-RADS on Multiparametric MRI for Prostate Cancer Diagnosis Within a Real-World Database

The PRIMARY score is a 5-category scale developed to identify clinically significant intraprostate malignancy (csPCa) on 68Ga-prostate-specific membrane antigen (PSMA)-11 PET/CT (68Ga-PSMA PET) using a combination of anatomic site, pattern, and intensity. Developed within the PRIMARY trial, the score requires evaluation in external datasets. This study aimed to assess the reproducibility and diagnostic accuracy of the PRIMARY score in a cohort of patients who underwent multiparametric MRI (mpMRI) and 68Ga-PSMA PET before prostate biopsy for the diagnosis of prostate cancer. Methods: In total, data from 242 men who had undergone 68Ga-PSMA PET and mpMRI before transperineal prostate biopsy were available for this ethics-approved retrospective study. 68Ga-PSMA PET and mpMRI data were centrally collated in a cloud-based deidentified image database. Six experienced prostate-focused nuclear medicine specialists were trained (1 h) in applying the PRIMARY score with 30 sample images. Six radiologists experienced in prostate mpMRI read images as per the Prostate Imaging-Reporting and Data System (PI-RADS), version 2.1. All images were read (with masking of clinical information) at least twice, with discordant findings sent to a masked third (or fourth) reader as necessary. Cohen κ was determined for both imaging scales as 5 categories and then collapsed to binary (negative and positive) categories (score 1 or 2 vs. 3, 4, or 5). Diagnostic performance parameters were calculated, with an International Society of Urological Pathology grade group of at least 2 (csPCa) on biopsy defined as the gold standard. Combined-imaging-positive results were defined as any PI-RADS score of 4 or 5 or as a PI-RADS score of 1-3 with a PRIMARY score of 3-5. Results: In total, 227 patients with histopathology, 68Ga-PSMA PET, and mpMRI imaging before prostate biopsy were included; 33% had no csPCa, and 67% had csPCa. Overall interrater reliability was higher for the PRIMARY scale (κ = 0.70) than for PI-RADS (κ = 0.58) when assessed as a binary category (benign vs. malignant). This was similar for all 5 categories (κ = 0.65 vs. 0.48). Diagnostic performance to detect csPCa was comparable between PSMA PET and mpMRI (sensitivity, 86% vs. 89%; specificity, 76% vs. 74%; positive predictive value, 88% vs. 88%; negative predictive value, 72% vs. 76%). Using combined imaging, sensitivity was 94%, specificity was 68%, positive predictive value was 86%, and negative predictive value was 85%. Conclusion: The PRIMARY score applied by first-user nuclear medicine specialists showed substantial interrater reproducibility, exceeding that of PI-RADS applied by mpMRI-experienced radiologists. Diagnostic performance was similar between the 2 modalities. The PRIMARY score should be considered when interpreting intraprostatic PSMA PET images.

Detection of PSMA expression on circulating tumor cells by blood-based liquid biopsy in prostate cancer

Background

For patients with mCRPC, PSMA-targeted radioligand treatment has significantly improved the clinical outcome. A blood-based liquid biopsy assay for recognizing PSMA protein expression on circulating tumor cells may be beneficial for better informing therapeutic decision-making and identifying the patients most likely to benefit from PSMA-targeted radioligand therapy.

Methods

Using high-throughput imaging and digital AI pathology algorithms, a four-color immunofluorescence assay has been developed to find PSMA protein expression on CTCs on a glass slide. Cell line cells (LNCaP/PC3s/22Rv1) spiked into healthy donor blood were used to study the precision, specificity, sensitivity, limit of detection, and overall accuracy of the assay. Clinical validation and low-pass whole-genome sequencing were performed in PSMA-PET-positive patients with high-risk mCRPC (N = 24) utilizing 3 mL of blood.

Results

The PSMA CTC IF assay achieved analytical specificity, sensitivity, and overall accuracy above 99% with high precision. In the clinical validation, 76% (16/21) of the cases were PSMA positive with CTC heterogeneity, and 88% (21/24) of the patients contained at least one conventional CTC per milliliter of blood. Thirty-six low-pass-sequenced CTCs from 11 individuals with mCRPC frequently exhibited copy number increases in AR and MYC and losses in RB1, PTEN, TP53, and BRCA2 locus.

Conclusions

The analytical validation utilizing Epic Sciences' liquid biopsy CTC platform demonstrated the potential to detect PSMA protein expression in CTCs from patients with mCRPC. This assay is positioned as an effective research tool to evaluate PSMA expression, heterogeneity, and therapeutic response in many ongoing clinical studies to target tumors that express PSMA.

How to Report PSMA PET

Prostate cancer (PCa) is the most common cancer diagnosed in men in most developed countries and a leading cause of cancer-related morbidity and mortality. Prostate-specific membrane antigen positron emission tomography (PSMA-PET) has become a valuable tool in the staging and assessment of disease recurrence in PCa, and more recently for assessment for treatment eligibility to PSMA radioligand therapy (RLT). Harmonization of PSMA-PET interpretation and synoptic reports are needed to communicate concisely and reproducibly PSMA-PET/CT to referring physicians and to support clinician therapeutic management decisions in various stages of the disease. Uniform image interpretation is also important to provide comparable data between clinical trials and to translate such data from research to daily practice. This review provides an overview of the value of PSMA-PET across the different clinical stages of PCa, discusses published reporting criteria for PSMA-PET, identifies pitfalls in reporting PSMA, and provides recommendations for synoptic reports.

Prognostic Value of PSMA PET/CT in Prostate Cancer

Prostate-specific membrane antigen (PSMA) is a transmembrane glycoprotein expressed in the majority of prostate cancer (PCa). PSMA has an enzymatic function that makes metabolic substrates such as folate available for utilization by PCa cells. Intracellular folate availability drives aggressive tumor phenotype. PSMA expression is, therefore, a marker of aggressive tumor biology. The large extracellular domain of PSMA is available for targeting by diagnostic and therapeutic radionuclides, making it a suitable cellular epitope for theranostics. PET imaging of radiolabeled PSMA ligands has several prognostic utilities. In the prebiopsy setting, intense PSMA avidity in a prostate lesion correlate well with clinically significant PCa (csPCa) on histology. When used for staging, PSMA PET imaging outperforms conventional imaging for the accurate staging of primary PCa, and findings on imaging predict post-treatment outcomes. The biggest contribution of PSMA PET imaging to PCa management is in the biochemical recurrence setting, where it has emerged as the most sensitive imaging modality for the localization of PCa recurrence by helping to guide salvage therapy. PSMA PET obtained for localizing the site of recurrence is prognostic, such that a higher lesion number predicts a less favorable outcome to salvage radiotherapy or surgical intervention. Systemic therapy is given to patients with advanced PCa with distant metastasis. PSMA PET is useful for predicting response to treatments with chemotherapy, first- and second-line androgen deprivation therapies, and PSMA-targeted radioligand therapy. Artificial intelligence using machine learning algorithms allows for the mining of information from clinical images not visible to the human eyes. Artificial intelligence applied to PSMA PET images, therefore, holds great promise for prognostication in PCa management.

Membrane-derived particles shed by PSMA-positive cells function as pro-angiogenic stimuli in tumors

Cell membrane-derived particles (Mp) are rounded membrane-enclosed particles that are shed from tumor cells. Mp are formed from tumor membranes and are capable of tumor targeting and immunotherapeutic agents because they share membrane homology with parental cells; thus, they are under consideration as a drug delivery vehicle. Prostate-specific membrane antigen (PSMA), a transmembrane glycoprotein with enzymatic functionality, is highly expressed in Mp and extracellular vesicles (EV) from prostate cancer (PCa) with poor clinical prognosis. Although PSMA expression was previously shown in EV and Mp isolated from cell lines and from the blood of patients with high-grade PCa, no pathophysiological effects have been linked to PCa-derived Mp. Here, we compared Mp from PSMA-expressing (PSMA-Mp) and PSMA-non-expressing (WT-Mp) cells side by side in vitro and in vivo. PSMA-Mp can transfer PSMA and new phenotypic characteristics to the tumor microenvironment. The consequence of PSMA transfer to cells and increased secretion of vascular endothelial growth factor-A (VEGF-A), pro-angiogenic and pro-lymphangiogenic mediators, with increased 4E binding protein 1 (4EBP-1) phosphorylation.

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.

Uncovering the Hidden Dangers and Molecular Mechanisms of Excess Folate: A Narrative Review

This review delves into the intricate relationship between excess folate (vitamin B9) intake, especially its synthetic form, namely, folic acid, and its implications on health and disease. While folate plays a pivotal role in the one-carbon cycle, which is essential for DNA synthesis, repair, and methylation, concerns arise about its excessive intake. The literature underscores potential deleterious effects, such as an increased risk of carcinogenesis; disruption in DNA methylation; and impacts on embryogenesis, pregnancy outcomes, neurodevelopment, and disease risk. Notably, these consequences stretch beyond the immediate effects, potentially influencing future generations through epigenetic reprogramming. The molecular mechanisms underlying these effects were examined, including altered one-carbon metabolism, the accumulation of unmetabolized folic acid, vitamin-B12-dependent mechanisms, altered methylation patterns, and interactions with critical receptors and signaling pathways. Furthermore, differences in the effects and mechanisms mediated by folic acid compared with natural folate are highlighted. Given the widespread folic acid supplementation, it is imperative to further research its optimal intake levels and the molecular pathways impacted by its excessive intake, ensuring the health and well-being of the global population.

A Novel Role of Prostate-Specific Membrane Antigen in Telomere Stability in Prostate Cancer Cells

Prostate-specific membrane antigen (PSMA) expression increases with prostate cancer grade and progression; however, the role of PSMA in prostate cancer progression remains poorly understood. Telomere stability is essential for the survival and genome stability of cancer cells. We found massive telomere DNA damage in PSMA-negative prostate cancer cells (PC-3 and DU145) compared with PSMA-positive prostate cancer (LNCaP) cells. The ectopic expression of PSMA suppressed telomere DNA damage in PC3 cells. PSMA inhibitor, 2-PMPA, and PSMA knockdown induced telomere DNA damage in PSMA-positive LNCaP cells but not in PSMA-negative PC-3 cells, suggesting that PSMA plays a critical role in telomere stability in prostate cancer cells. In addition, we observed that inhibition of PSMA or inhibition of glutamate receptor, which mediates PSMA-dependent activation of AKT, suppressed AKT phosphorylation, and caused telomere DNA damage. Furthermore, 2-PMPA-induced telomere DNA damage in LNCaP cells was associated with telomere aberrations, such as telomere-telomere fusions, sister-chromatid telomere fusions, and telomere breakages. AKT is reported to promote cell growth by stabilizing telomere association with telomere-binding proteins TRF1 and TPP1. We observed that TRF1 and TPP1 transfection of LNCaP cells attenuated the inhibitory effect of 2-PMPA on cell growth and telomere DNA damage. Together, these observations indicate that PSMA role in maintaining telomere stability in prostate cancer cells is mediated by AKT. Thus, these studies reveal an important role of PSMA in maintaining telomere stability that can promote cell survival and, thereby, prostate cancer progression.

IMPLICATIONS

Role of PSMA in telomere stability suggests a strong correlation between PSMA expression and prostate cancer progression.

GAD1 contributes to the progression and drug resistance in castration resistant prostate cancer

BACKGROUND

Prostate cancer is currently the second most lethal malignancy in men worldwide due to metastasis and invasion in advanced stages. Studies have revealed that androgen deprivation therapy can induce stable remission in patients with advanced prostate cancer, although most patients will develop castration-resistant prostate cancer (CRPC) in 1-2 years. Docetaxel and enzalutamide improve survival in patients with CRPC, although only for a short time, eventually patients develop primary or secondary resistance, causing disease progression or biochemical relapse.

METHODS

The gene expression profiles of docetaxel-sensitive or -resistant prostate cancer cell lines, namely GSE33455, GSE36135, GSE78201, GSE104935, and GSE143408, were sequentially analyzed for differentially expressed genes and progress-free interval significance. Subsequently, the overall survival significance and clinic-pathological features were analyzed by the R package. The implications of hub genes mutations, methylation in prostate cancer and the relationship with the tumor immune cell infiltration microenvironment were assessed with the help of cBioPortal, UALCAN and TISIDB web resources. Finally, effects of the hub genes on the progression and drug resistance in prostate cancer were explored using reverse transcription-polymerase chain reaction (RT-PCR), immunohistochemistry, cell phenotype, and drug sensitivity.

RESULT

Glutamate decarboxylase 1 (GAD1) was tentatively identified by bioinformatic analysis as an hub gene for the development of drug resistance, including docetaxel and enzalutamide, in prostate cancer. Additionally, GAD1 expression, mutation and methylation were significantly correlated with the clinicopathological features and the tumor immune microenvironment. RT-PCR, immunohistochemistry, cell phenotype and drug sensitivity experiments further demonstrated that GAD1 promoted prostate cancer progression and decreased the therapeutic effect of docetaxel or enzalutamide.

CONCLUSION

This research confirmed that GAD1 was a hub gene in the progression and development of drug resistance in prostate cancer. This helped to explain prostate cancer drug resistance and provides new immune-related therapeutic targets and biomarkers for it.

Castration-Resistant Prostate Cancer: From Uncovered Resistance Mechanisms to Current Treatments

Prostate cancer (PC) is the second most common cancer in men worldwide. Despite recent advances in diagnosis and treatment, castration-resistant prostate cancer (CRPC) remains a significant medical challenge. Prostate cancer cells can develop mechanisms to resist androgen deprivation therapy, such as AR overexpression, AR mutations, alterations in AR coregulators, increased steroidogenic signaling pathways, outlaw pathways, and bypass pathways. Various treatment options for CRPC exist, including androgen deprivation therapy, chemotherapy, immunotherapy, localized or systemic therapeutic radiation, and PARP inhibitors. However, more research is needed to combat CRPC effectively. Further investigation into the underlying mechanisms of the disease and the development of new therapeutic strategies will be crucial in improving patient outcomes. The present work summarizes the current knowledge regarding the underlying mechanisms that promote CRPC, including both AR-dependent and independent pathways. Additionally, we provide an overview of the currently approved therapeutic options for CRPC, with special emphasis on chemotherapy, radiation therapy, immunotherapy, PARP inhibitors, and potential combination strategies.

Emerging Role of Nuclear Medicine in Prostate Cancer: Current State and Future Perspectives

Prostate cancer is the most frequent epithelial neoplasia after skin cancer in men starting from 50 years and prostate-specific antigen (PSA) dosage can be used as an early screening tool. Prostate cancer imaging includes several radiological modalities, ranging from ultrasonography, computed tomography (CT), and magnetic resonance to nuclear medicine hybrid techniques such as single-photon emission computed tomography (SPECT)/CT and positron emission tomography (PET)/CT. Innovation in radiopharmaceutical compounds has introduced specific tracers with diagnostic and therapeutic indications, opening the horizons to targeted and very effective clinical care for patients with prostate cancer. The aim of the present review is to illustrate the current knowledge and future perspectives of nuclear medicine, including stand-alone diagnostic techniques and theragnostic approaches, in the clinical management of patients with prostate cancer from initial staging to advanced disease.

Vascularized tumor on a microfluidic chip to study mechanisms promoting tumor neovascularization and vascular targeted therapies

The cascade of events leading to tumor formation includes induction of a tumor supporting neovasculature as a primary hallmark of cancer. Developing vasculature is difficult to evaluate in vivo but can be captured using microfluidic chip technology and patient derived cells. Herein, we established an on chip approach to investigate the mechanisms promoting tumor vascularization and vascular targeted therapies via co-culture of metastatic renal cell carcinoma spheroids and endothelial cells in a 3D environment. Our model permitted real-time, high-resolution observation and assessment of tumor-induced angiogenesis, where endothelial cells sprout towards the tumor and mimic a vascular network. Bevacizumab, an angiogenic inhibitor, disrupted interactions between vessels and tumors, destroying the vascular network. The on chip approach enabled assessment of endothelial cell biology, vessel's functionality, drug delivery, and molecular expression of PSMA. Finally, observations in the vascularized tumor on chip permitted direct and conclusive quantification of this therapy in weeks as opposed to months in a comparable animal model.

Teaser

Vascularized tumor on microfluidic chip provides opportunity to study targeted therapies and improves preclinical drug discovery.

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).

Novel Multiparametric Magnetic Resonance Imaging-Based Deep Learning and Clinical Parameter Integration for the Prediction of Long-Term Biochemical Recurrence-Free Survival in Prostate Cancer after Radical Prostatectomy

Radical prostatectomy (RP) is the main treatment of prostate cancer (PCa). Biochemical recurrence (BCR) following RP remains the first sign of aggressive disease; hence, better assessment of potential long-term post-RP BCR-free survival is crucial. Our study aimed to evaluate a combined clinical-deep learning (DL) model using multiparametric magnetic resonance imaging (mpMRI) for predicting long-term post-RP BCR-free survival in PCa. A total of 437 patients with PCa who underwent mpMRI followed by RP between 2008 and 2009 were enrolled; radiomics features were extracted from T2-weighted imaging, apparent diffusion coefficient maps, and contrast-enhanced sequences by manually delineating the index tumors. Deep features from the same set of imaging were extracted using a deep neural network based on pretrained EfficentNet-B0. Here, we present a clinical model (six clinical variables), radiomics model, DL model (DLM-Deep feature), combined clinical-radiomics model (CRM-Multi), and combined clinical-DL model (CDLM-Deep feature) that were built using Cox models regularized with the least absolute shrinkage and selection operator. We compared their prognostic performances using stratified fivefold cross-validation. In a median follow-up of 61 months, 110/437 patients experienced BCR. CDLM-Deep feature achieved the best performance (hazard ratio [HR] = 7.72), followed by DLM-Deep feature (HR = 4.37) or RM-Multi (HR = 2.67). CRM-Multi performed moderately. Our results confirm the superior performance of our mpMRI-derived DL algorithm over conventional radiomics.

Case Report: Long-term complete response to PSMA-targeted radioligand therapy and abiraterone in a metastatic prostate cancer patient

Despite decades of research and clinical trials, metastatic castration-resistant prostate cancer (mCRPC) remains incurable and typically fatal. Current treatments may provide modest increases in progression-free survival but can come with significant adverse effects and are disaggregated from the diagnostic imaging needed to fully assess the spread of metastatic disease. A theranostic approach, using radiolabeled ligands that target the cell surface protein PSMA, simplifies the visualization and disease treatment process by enabling both to use similar agents. Here, we describe an exemplary case wherein a gentleman in his 70s with mCRPC on diagnosis was treated with 177Lu-PSMA-617 and abiraterone, and remains disease-free to date, over five years later.

Prostate-specific membrane antigen (PSMA) as a potential target for molecular imaging and treatment in bone and soft tissue sarcomas

Bone and soft tissue sarcomas are a group of rare malignant tumours with major histological and anatomical varieties. In a metastatic setting, sarcomas have a poor prognosis due to limited response rates to chemotherapy. Radioligand therapy targeting prostate-specific membrane antigen (PSMA) may offer a new perspective. PSMA is a type II transmembrane glycoprotein which is present in all prostatic tissue and overexpressed in prostate cancer. Despite the name, PSMA is not prostate-specific. PSMA expression is also found in a multitude of non-prostatic diseases including a subgroup of sarcomas, mostly in its neovascular endothelial cells. On PET/CT imaging, multiple sarcomas have also shown intense PSMA-tracer accumulation. PSMA expression and PSMA-tracer uptake seem to be highest in patients with aggressive and advanced sarcomas, who are also in highest need of new therapeutic options. Although these results provide a good rationale for the future use of PSMA-targeted radioligand therapy in a selection of sarcoma patients, more research is needed to gain insight into optimal patient selection methods, PSMA-targeting antibodies and tracers, administered doses of radioligand therapy, and their efficacy and tolerability. In this review, mRNA expression of the FOLH1 gene which encodes PSMA, PSMA immunohistochemistry, PSMA-targeted imaging and PSMA-targeted therapy in sarcomas will be discussed.

The Potential of PSMA as a Vascular Target in TNBC

Recent studies proving prostate-specific membrane antigen (PSMA) expression on triple-negative breast cancer (TNBC) cells and adjacent endothelial cells suggest PSMA as a promising target for therapy of until now not-targetable cancer entities. In this study, PSMA and its isoform expression were analyzed in different TNBC cells, breast cancer stem cells (BCSCs), and tumor-associated endothelial cells. PSMA expression was detected in 91% of the investigated TNBC cell lines. The PSMA splice isoforms were predominantly found in the BCSCs. Tumor-conditioned media from two TNBC cell lines, BT-20 (high full-length PSMA expression, PSMAΔ18 expression) and Hs578T (low full-length PSMA expression, no isoform expression), showed significant pro-angiogenic effect with induction of tube formation in endothelial cells. All TNBC cell lines induced PSMA expression in human umbilical vein endothelial cells (HUVEC). Significant uptake of radiolabeled ligand [⁶⁸Ga]Ga-PSMA was detected in BCSC1 (4.2%), corresponding to the high PSMA expression. Moreover, hypoxic conditions increased the uptake of radiolabeled ligand [¹⁷⁷Lu]Lu-PSMA in MDA-MB-231 (0.4% vs. 3.4%, under hypoxia and normoxia, respectively) and MCF-10A (0.3% vs. 3.0%, under normoxia and hypoxia, respectively) significantly (p < 0.001). [¹⁷⁷Lu]Lu-PSMA-induced apoptosis rates were highest in BT-20 and MDA-MB-231 associated endothelial cells. Together, these findings demonstrate the potential of PSMA-targeted therapy in TNBC.

Synthesis and Preclinical Evaluation of Three Novel 68Ga-Labeled Bispecific PSMA/FAP-Targeting Tracers for Prostate Cancer Imaging

Tumor heterogeneity limits the efficacy and reliability of monospecific radiopharmaceuticals in prostate cancer diagnosis and therapy. To overcome this limitation and improve lesion detection sensitivity, we developed and evaluated three bispecific radiotracers that can target both prostate-specific membrane antigen (PSMA) and fibroblast activation protein (FAP), which are the two key proteins overexpressed in prostate cancer. Three FAP-targeting ligands with various linker lengths were synthesized through multistep organic synthesis, and then connected to the PSMA-targeting motif. IC₅₀(PSMA) and IC₅₀(FAP) values of Ga-complexed bispecific ligands, Ga-AV01017, Ga-AV01030, and Ga-AV01038 were 25.2-71.6 and 1.25-2.74 nM, respectively. The uptake values in PSMA-expressing LNCaP tumor xenografts were 4.38 ± 0.55, 5.17 ± 0.51, and 4.25 ± 0.86 %ID/g for [⁶⁸Ga]Ga-AV01017, [⁶⁸Ga]Ga-AV01030, and [⁶⁸Ga]Ga-AV01038, respectively, which were lower than the monospecific PSMA-targeting tracer [⁶⁸Ga]Ga-HTK03041 (23.1 ± 6.11 %ID/g). The uptake values in FAP-expressing HEK293T:hFAP tumor xenografts were 2.99 ± 0.37, 3.69 ± 0.81, 3.64 ± 0.83 %ID/g for [⁶⁸Ga]Ga-AV01017, [⁶⁸Ga]Ga-AV01030, and [⁶⁸Ga]Ga-AV01038, respectively, which were also lower than the monospecific FAP-targeting tracer, [⁶⁸Ga]Ga-FAPI-04 (12.5 ± 2.00 %ID/g). We observed that the bispecific tracers had prolonged blood retention, in which tracers with a longer linker tend to have a higher blood uptake and lower tumor uptake. Further investigations are needed to optimize the linker selection to generate promising bispecific PSMA/FAP-targeting tracers for prostate cancer imaging.

Using PSMA imaging for prognostication in localized and advanced prostate cancer

The use of prostate-specific membrane antigen (PSMA)-directed applications in modern prostate cancer management has evolved rapidly over the past few years, helping to establish new treatment pathways and provide further insights into prostate cancer biology. However, the prognostic implications of PSMA-PET have not been studied systematically, owing to rapid clinical implementation without long follow-up periods to determine intermediate-term and long-term oncological outcomes. Currently available data suggest that traditional prognostic factors and survival outcomes are associated with high PSMA expression (both according to immunohistochemistry and PET uptake) in men with localized and biochemically recurrent disease. Treatment with curative intent (primary and/or salvage) often fails when PSMA-positive metastases are present; however, the sensitivity of PSMA-PET in detecting all metastases is poor. Low PSMA-PET uptake in recurrent disease is a favourable prognostic factor; however, it can be associated with poor prognosis in conjunction with high ¹⁸F-fluorodeoxyglucose uptake in metastatic castration-resistant prostate cancer. Clinical trials embedding PSMA-PET for guiding management with reliable oncological outcomes are needed to support ongoing clinical use.

Bispecific PSMA antibodies and CAR-T in metastatic castration-resistant prostate cancer

Prostate cancer is the most common cancer among men and the second leading cause of cancer-related deaths in men in the United States. The treatment paradigm for prostate cancer has evolved with the emergence of a variety of novel therapies which have improved survival; however, treatment-related toxicities are abundant and durable responses remain rare. Immune checkpoint inhibitors have shown modest activity in a small subset of patients with prostate cancer and have not had an impact on most men with advanced disease. The discovery of prostate-specific membrane antigen (PSMA) and the understanding of its specificity to prostate cancer has identified it as an ideal tumor-associated antigen and has revived the enthusiasm for immunotherapeutics in prostate cancer. T-cell immunotherapy in the form of bispecific T-cell engagers (BiTEs) and chimeric antigen receptor (CAR) T-cell therapy have shown exceptional success in treating various hematologic malignancies, and are now being tested in patients with prostate cancer with drug design centered on various target ligands including not just PSMA, but others as well including six-transmembrane epithelial antigen of the prostate 1 (STEAP1) and prostate stem cell antigen (PSCA). This summative review will focus on the data surrounding PSMA-targeting T-cell therapies. Early clinical studies with both classes of T-cell redirecting therapies have demonstrated antitumor activity; however, there are multiple challenges with this class of agents, including dose-limiting toxicity, 'on-target, off-tumor' immune-related toxicity, and difficulty in maintaining sustained immune responses within a complex and overtly immunosuppressive tumor microenvironment. Reflecting on experiences from recent trials has been key toward understanding mechanisms of immune escape and limitations in developing these drugs in prostate cancer. Newer generation BiTE and CAR T-cell constructs, either alone or as part of combination therapy, are currently under investigation with modifications in drug design to overcome these barriers. Ongoing innovation in drug development will likely foster successful implementation of T-cell immunotherapy bringing transformational change to the treatment of prostate cancer.

Distant Nodes Seen on PSMA PET-CT Staging Predicts Post-Treatment Progression in Men with Newly Diagnosed Prostate Cancer-A Prospective Cohort Study

PSMA PET-CT scans are now recommended in international urological guidelines for primary staging and re-staging of prostate cancer. However, there is little published literature on the clinical outcomes for patients after treatment decisions made using PSMA PET-CT results. This is a multisite, prospective cohort study investigating the clinical outcomes of men who received treatment plans based on PSMA PET-CT results for primary staging. Men with biopsy proven prostate cancer received a PSMA PET-CT scan for primary staging. Treatment plans were recommended by multidisciplinary teams (MDT). After treatment, these men were followed with 6 monthly PSA tests and imaging or biopsies if recommended by MDT. The primary outcome was treatment progression defined as the addition or change of any treatment modalities such as androgen deprivation therapy, radiation therapy or chemotherapy. In total, 80% of men did not have any treatment progression after enactment of treatment based on PSMA PET-CT primary staging results at 29 months of follow up. Men who had distant nodes seen on PSMA PET-CT had a 5 times increased risk of treatment progression. Larger studies with longer follow up are needed to validate our results and optimise the way clinicians use PSMA PET-CT results to guide management.

Using 68Ga-PSMA-11 PET/CT for Therapy Response Assessment in Patients with Metastatic Castration-Resistant Prostate Cancer: Application of EAU/EANM Recommendations in Clinical Practice

For patients with metastatic castration-resistant prostate cancer (mCRPC), no reliable biomarkers for predicting therapeutic response or assisting in treatment selection and sequencing are currently available. Using the recent European Association of Urology and European Association of Nuclear Medicine recommendations, we aimed to compare response assessment between prostate-specific membrane antigen (PSMA) PET/CT and conventional imaging in mCRPC patients starting first-line treatment with a novel hormonal agent (NHA) and to perform a sequential comparative analysis of PSMA PET/CT-derived parameters after 4 and 12 wk of therapy. Methods: Data from 18 mCRPC patients who started NHA treatment and underwent ⁶⁸Ga-PSMA-11 PET/CT before therapy initiation (baseline), at week 4 (W4), and at week 12 (W12) in addition to conventional imaging (bone scintigraphy, CT) at baseline and W12 were retrospectively included. PET/CT images were quantitatively analyzed for maximum and mean SUV and total PSMA ligand-positive lesions. Comparative analysis of PET/CT-derived parameters was performed, and patients were classified as having nonprogressive disease or progressive disease (PD) according to ⁶⁸Ga-PSMA-11 PET/CT, prostate-specific antigen, and conventional imaging criteria. Results: Treatment response was evaluable by ⁶⁸Ga-PSMA-11 PET/CT in 16 of 18 patients (89%) and by conventional imaging in 11 of 18 patients (61%). Five of 16 patients classified as having PD by ⁶⁸Ga-PSMA-11 PET/CT at W12 had already met progression criteria at W4, and substantial agreement was observed between W4 and W12 (κ, 0.74) ⁶⁸Ga-PSMA-11 PET/CT results. Nonetheless, 2 of 16 patients (13%) were incorrectly classified as having PD because of a flare phenomenon on PSMA PET/CT that disappeared at W12. Conclusion: Volumetric assessments of ⁶⁸Ga-PSMA-11 PET/CT imaging can improve response evaluation in NHA-treated patients with mCRPC. Although early response assessments at W4 need to be approached with caution because of flare, ⁶⁸Ga-PSMA-11 PET/CT imaging at W4 and W12 revealed substantial agreement in therapy response assessments; these findings warrant further investigation to distinguish PD from flare at W4 and help improve the understanding of resistance to therapy.

The prevalence and prognosis of next-generation therapeutic targets in metastatic castration-resistant prostate cancer

The success of the PROfound, IPATential150, and TheraP trials promoted the transition from sequential treatment to therapeutic targets (TTs)-guided precision treatment in metastatic castration-resistant prostate cancer (mCRPC). The objective of this study was to evaluate the prevalence and prognostic value of TTs from these three trials. All included Chinese mCRPC patients underwent circulating tumor DNA (ctDNA) sequencing, PTEN status assessment, and dual-tracer [⁶⁸ Ga-prostate-specific membrane antigen (PSMA) and ¹⁸ F-fluorodexyglucose (FDG)] positron emission tomography/computed tomography (PET/CT). Previous treatment with cabazitaxel, Lu-PSMA or olaparib was unallowed. Patients with known significant sarcomatoid or spindle cell or neuroendocrine small cell components were also excluded. TTs were defined as positive as follows: (a) high PSMA and no PSMA-/FDG+ disease on dual-tracer PET/CT scans; (b) defects in homologous recombination repair (HRR) genes in ctDNA; and (c) loss of PTEN immunohistochemistry staining in tumor tissue. The prevalence and prognostic value on progression-free survival (PFS) of TTs were evaluated. A total of 106 consecutive mCRPC patients were included. The prevalence of positive PET/CT, HRR defect, and PTEN loss was 30%, 29% and 16%, respectively. Sixty-three patients had at least one TT. Metastatic volume (odds ratio = 5.0; P = 0.017) was the only independent factor of positive TT in multivariate analysis. Seventy-four patients received abiraterone after TT screening. Patients with positive PET/CT (P = 0.011) and HRR defect (P = 0.002) had a significantly shorter PFS after receiving abiraterone than patients with negative TTs. However, PTEN status was unrelated to PFS, which may be due to a less number of patients with PTEN loss (P = 0.952). Overall, patients with any positive TTs had a significantly shorter PFS after abiraterone than patients with negative TTs (P = 0.009). Nearly 60% of Chinese patients with mCRPC who had a poor prognosis on abiraterone were candidates for precision treatments based on the specific criteria of TTs.

Ex vivo γH2AX assay for tumor radiosensitivity in primary prostate cancer patients and correlation with clinical parameters

Backround

Accurate surrogate parameters for radio resistance are warranted for individualized radiotherapy (RT) concepts in prostate cancer (PCa). The purpose of this study was to assess intertumoral heterogeneity in terms of radio resistance using an ex-vivo γH2AX assay after irradiation of prostate biopsy cores and to investigate its correlation with clinical features of respective patients as well as imaging and genomic features of tumor areas.

Methods

Twenty one patients with histologically-proven PCa and pre-therapeutic multiparametric resonance imaging and prostate-specific membrane antigen positron emission tomography were included in the study. Biopsy cores were collected from 26 PCa foci. Residual γH2AX foci were counted 24 h after ex-vivo irradiation (with 0 and 4 Gy) of biopsy specimen and served as a surrogate for radio resistance. Clinical, genomic (next generation sequencing) and imaging features were collected and their association with the radio resistance was studied.

Results

In total 18 PCa lesions from 16 patients were included in the final analysis. The median γH2AX foci value per PCa lesion was 3.12. According to this, the patients were divided into two groups (radio sensitive vs. radio resistant) with significant differences in foci number (p < 0.0001). The patients in the radio sensitive group had significantly higher prostate specific antigen serum concentration (p = 0.015), tumor areas in the radio sensitive group had higher SUV (standardized uptake values in PSMA PET)-max and -mean values (p = 0.0037, p = 0.028) and lower ADC (apparent diffusion coefficient-mean values, p = 0.049). All later parameters had significant (p < 0.05) correlations in Pearson’s test. One patient in the radio sensitive group displayed a previously not reported loss of function frameshift mutation in the NBN gene (c.654_658delAAAAC) that introduces a premature termination codon and results in a truncated protein.

Conclusion

In this pilot study, significant differences in intertumoral radio resistance were observed and clinical as well as imaging parameters may be applied for their prediction. After further prospective validation in larger patient cohorts these finding may lead to individual RT dose prescription for PCa patients in the future.

PSA-Stratified Performance of [18F]DCFPyL PET/CT in Biochemically Recurrent Prostate Cancer Patients under Androgen Deprivation Therapy

Based on in vitro studies, it is known that androgen deprivation therapy (ADT) increases prostate-specific membrane antigen (PSMA) expression on prostate cancer (PCa) cells. However, ADT also has cytoreductive effects which can decrease lesion size. The present evaluation was conducted to further analyze the influence of ongoing ADT on [18F]DCFPyL positron emission tomography/computed tomography (PET/CT) performance in the setting of biochemically recurrent PCa. We retrospectively evaluated two groups of PCa patients, previously treated with radical intent, who had undergone [18F]DCFPyL PET/CT because of biochemical relapse with a minimum PSA level of 0.4 ng/mL. One group consisted of 95 patients under ADT at the time of the PET examination, and the other consisted of 445 patients not receiving ADT at the time of PET/CT. The uptake characteristics of the cardiac blood pool, liver, parotid glands, and five most active lesions were measured and compared between these two groups. The overall detection rate of [18F]DCFPyL PET/CT in patients under ADT at the time of imaging was significantly higher than patients not under ADT (91.6% vs. 80.4%, p-value = 0.007). However, the PSA-stratified differences in detection rates between patients with and without ADT did not reach statistical significance. Except for the maximal standardized uptake values corrected for lean body mass (SULmax) in the PSA range of 1 to <2 ng/mL, the intensity and volume of [18F]DCFPyL accumulation were higher in patients with ADT compared to the patients without. Statistical significance was attained for the SULmax in PSA range of 0.5 to <1 ng/mL (p-value = 0.0004) and metabolic tumor volume (MTV) in all PSA ranges (p-values of 0.0005 to 0.03). No significant difference was observed for radiotracer uptake in normal organs between the two groups with and without ADT. In this study population with biochemical recurrence of PCa and measurable PSA, ongoing ADT at the time of [18F]DCFPyL PET/CT imaging was associated with higher radiotracer uptake and overall lesion detection rate. This could be due in part to the more aggressive disease phenotype in patients with ongoing ADT.

A Supramolecular Self-Assembling Nanoagent by Inducing Intracellular Aggregation of PSMA for Prostate Cancer Molecularly Targeted Theranostics

Prostate cancer (PCa) with prostate-specific membrane antigen (PSMA)-specific high expression is well suited for molecularly targeted theranostics. PSMA expression correlates with the malignancy of PCa, and its dimeric form can promote tumor progression by exerting enzymatic activity to activate downstream signal transduction. However, almost no studies have shown that arresting the procancer signaling of the PSMA receptors themselves can cause tumor cell death. Meanwhile, supramolecular self-assembling peptides are widely used to design anticancer agents due to their unique and excellent properties. Here, a PSMA-targeting supramolecular self-assembling nanotheranostic agent, DBT-2FFGACUPA, which actively targets PSMA receptors on PCa cell membranes and induces them to enter the cell and form large aggregates, is developed. This process not only selectively images PSMA-positive tumor cells but also suppresses the downstream procancer signals of PSMA, causing tumor cell death. This work provides an alternative approach and an advanced agent for molecularly targeted theranostics options in PCa that can induce tumor cell death without relying on any reported anticancer drugs.

Urothelial Carcinoma and Prostate-specific Membrane Antigen: Cellular, Imaging, and Prognostic Implications

CONTEXT

Staging, restaging, and surveillance of urothelial carcinoma (UC) is challenging due to suboptimal accuracy of standard of care imaging modalities. Prostate-specific membrane antigen (PSMA) imaging may serve to improve characterisation of UC.

OBJECTIVE

To appraise available literature regarding cellular, imaging, and prognostic implications of PSMA for UC.

EVIDENCE ACQUISITION

A systematic review was performed considering all available literature (including conference abstracts) published from 1990 to 2020 and reported according to Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines following registration in PROSPERO (CRD42020186744). All relevant texts relating to immunohistochemical analysis and PSMA-based imaging in UC were included and collated. Additionally, FOLH1 (gene encoding PSMA) expression according to The Cancer Genome Atlas (TCGA) database was analysed as well as according to consensus and TCGA molecular classification subtypes and subsequently compared with clinical outcomes.

EVIDENCE SYNTHESIS

PSMA expression across UC tumour tissue was heterogeneous (0-100%) but appeared to decrease with increased grade and stage. The TCGA analysis demonstrated loss of FOLH1 expression with increasing T stage (p = 0.0180) and N stage (p = 0.0269), and reduced FOLH1 expression was associated with worse disease-free survival. PSMA expression in UC neovasculature was variable but mostly increased (44-100%). Eleven reports of PSMA-based imaging for UC were identified, reporting on 18 patients. PSMA positron emission tomography (PET) imaging was positive in 17 out of 18 patients. The included literature review data were limited by mostly low-quality, retrospective studies.

CONCLUSIONS

Tissue PSMA, or FOLH1 expression, may inversely be associated with pathological and survival outcomes in localised UC. PSMA PET imaging may improve detection of metastatic disease and response to systemic therapy due to PSMA expression in neovasculature. Available evidence is limited; thus, larger, prospective studies are required to confirm early results and define populations that benefit most.

PATIENT SUMMARY

In this systematic review, we assess the potential role of prostate-specific membrane antigen in urothelial cancer. We found that its utility is in expression of blood vessels surrounding metastasis. We conclude that it may be beneficial in detecting metastasis and response to systemic therapies.

Prostate-specific Membrane Antigen Biology in Lethal Prostate Cancer and its Therapeutic Implications

CONTEXT

Prostate-specific membrane antigen (PSMA) is a promising, novel theranostic target in advanced prostate cancer (PCa). Multiple PSMA-targeted therapies are currently in clinical development, with some agents showing impressive antitumour activity, although optimal patient selection and therapeutic resistance remain ongoing challenges.

OBJECTIVE

To review the biology of PSMA and recent advances in PSMA-targeted therapies in PCa, and to discuss potential strategies for patient selection and further therapeutic development.

EVIDENCE ACQUISITION

A comprehensive literature search was performed using PubMed and review of American Society of Clinical Oncology and European Society of Medical Oncology annual meeting abstracts up to April 2021.

EVIDENCE SYNTHESIS

PSMA is a largely extracellular protein that is frequently, but heterogeneously, expressed by PCa cells. PSMA expression is associated with disease progression, worse clinical outcomes and the presence of tumour defects in DNA damage repair (DDR). PSMA is also expressed by other cancer cell types and is implicated in glutamate and folate metabolism. It may confer a tumour survival advantage in conditions of cellular stress. PSMA regulation is complex, and recent studies have shed light on interactions with androgen receptor, PI3K/Akt, and DDR signalling. A phase 2 clinical trial has shown that 177Lu-PSMA-617 causes tumour shrinkage and delays disease progression in a significant subset of patients with metastatic castration-resistant PCa in comparison to second-line chemotherapy. Numerous novel PSMA-targeting immunotherapies, small molecules, and antibody therapies are currently in clinical development, including in earlier stages of PCa, with emerging evidence of antitumour activity. To date, the regulation and function of PSMA in PCa cells remain poorly understood.

CONCLUSIONS

There has been rapid recent progress in PSMA-targeted therapies for the management of advanced PCa. Dissection of PSMA biology will help to identify biomarkers for and resistance mechanisms to these therapies and facilitate further therapeutic development to improve PCa patient outcomes.

PATIENT SUMMARY

There have been major advances in the development of therapies targeting a molecule, PSMA, in PCa. Radioactive molecules targeting PSMA can cause tumour shrinkage and delay progression in some patients with lethal disease. Future studies are needed to determine which patients are most likely to respond, and how other treatments can be combined with therapies targeting PSMA so that more patients may benefit.

Comparison of Multiparametric Magnetic Resonance Imaging with Prostate-Specific Membrane Antigen Positron-Emission Tomography Imaging in Primary Prostate Cancer Diagnosis: A Systematic Review and Meta-Analysis

Multiparametric magnetic-resonance imaging (mpMRI) has proven utility in diagnosing primary prostate cancer. However, the diagnostic potential of prostate-specific membrane antigen positron-emission tomography (PSMA PET) has yet to be established. This study aims to systematically review the current literature comparing the diagnostic performance of mpMRI and PSMA PET imaging to diagnose primary prostate cancer. A systematic literature search was performed up to December 2021. Quality analyses were conducted using the QUADAS-2 tool. The reference standard was whole-mount prostatectomy or prostate biopsy. Statistical analysis involved the pooling of the reported diagnostic performances of each modality, and differences in per-patient and per-lesion analysis were compared using a Fisher’s exact test. Ten articles were included in the meta-analysis. At a per-patient level, the pooled values of sensitivity, specificity, and area under the curve (AUC) for mpMRI and PSMA PET/CT were 0.87 (95% CI: 0.83−0.91) vs. 0.93 (95% CI: 0.90−0.96, p < 0.01); 0.47 (95% CI: 0.23−0.71) vs. 0.54 (95% CI: 0.23−0.84, p > 0.05); and 0.84 vs. 0.91, respectively. At a per-lesion level, the pooled sensitivity, specificity, and AUC value for mpMRI and PSMA PET/CT were lower, at 0.63 (95% CI: 0.52−0.74) vs. 0.79 (95% CI: 0.62−0.92, p < 0.001); 0.88 (95% CI: 0.81−0.95) vs. 0.71 (95% CI: 0.47−0.90, p < 0.05); and 0.83 vs. 0.84, respectively. High heterogeneity was observed between studies. PSMA PET/CT may better confirm the presence of prostate cancer than mpMRI. However, both modalities appear comparable in determining the localisation of the lesions.

Prostate-Specific Membrane Antigen Expression and Response to DNA Damaging Agents in Prostate Cancer

PURPOSE

Prostate-specific membrane antigen (PSMA) targeting therapies such as Lutetium-177 (177Lu)-PSMA-617 are affecting outcomes from metastatic castration-resistant prostate cancer (mCRPC). However, a significant subset of patients have prostate cancer cells lacking PSMA expression, raising concerns about treatment resistance attributable at least in part to heterogeneous PSMA expression. We have previously demonstrated an association between high PSMA expression and DNA damage repair defects in mCRPC biopsies and therefore hypothesized that DNA damage upregulates PSMA expression.

EXPERIMENTAL DESIGN

To test this relationship between PSMA and DNA damage we conducted a screen of 147 anticancer agents (NCI/NIH FDA-approved anticancer "Oncology Set") and treated tumor cells with repeated ionizing irradiation.

RESULTS

The topoisomerase-2 inhibitors, daunorubicin and mitoxantrone, were identified from the screen to upregulate PSMA protein expression in castration-resistant LNCaP95 cells; this result was validated in vitro in LNCaP, LNCaP95, and 22Rv1 cell lines and in vivo using an mCRPC patient-derived xenograft model CP286 identified to have heterogeneous PSMA expression. As double-strand DNA break induction by topoisomerase-2 inhibitors upregulated PSMA, we next studied the impact of ionizing radiation on PSMA expression; this also upregulated PSMA protein expression in a dose-dependent fashion.

CONCLUSIONS

The results presented herein are the first, to our knowledge, to demonstrate that PSMA is upregulated in response to double-strand DNA damage by anticancer treatment. These data support the study of rational combinations that maximize the antitumor activity of PSMA-targeted therapeutic strategies by upregulating PSMA.

PSMA PET-CT Imaging Predicts Treatment Progression in Men with Biochemically Recurrent Prostate Cancer-A Prospective Study of Men with 3 Year Follow Up

Simple Summary

Prostate-specific membrane antigen (PSMA) positron emission tomography-computed tomography (PET-CT) is an essential imaging tool that is used to locate prostate cancer when it recurs. The results of this scan are used to guide clinical decisions for the management of cancer. However, the long-term effect of these clinical decisions is yet to be determined. In this study, we followed men with recurrent prostate cancer for 3 years after they had a clinical decision made based on a PSMA PET-CT. Our results showed that 75% of men had no addition or change in their treatment plan 3 years after their initial clinical decision was made. In men with a PSMA PET-CT that showed no suspected cancer, 85% had no addition or change to their treatment plan. This indicates that clinical decisions made using PSMA PET-CT in this setting can have a medium- to long-lasting effect.

Abstract

Prostate-specific membrane antigen (PSMA) positron emission tomography-computed tomography (PET-CT) is a novel imaging modality used to stage recurrent prostate cancer. It has the potential to improve prognostication and ultimately guide the timing of treatment for men with recurrent prostate cancer. This study aims to assess the clinical impact of PSMA PET-CT by analyzing its predictive value of treatment progression after 3 years of follow-up. In this prospective cohort study of 100 men, patients received a PSMA PET-CT for restaging of their disease which was used by a multi-disciplinary team to make a treatment decision. The primary endpoint was treatment progression. This was defined as the addition or change of any treatment modalities such as androgen deprivation therapy (ADT), radiation therapy or chemotherapy. The median follow-up time was 36 months (IQR 24–40 months). No treatment progression was found in 72 (75%) men and therefore 24 (25%) patients were found to have treatment progression. In men with a negative PSMA PET-CT result, 5/33 (15.1%) had treatment progression and 28/33 (84.8%) had no treatment progression. In conclusion, clinical decisions made with PSMA PET-CT results led to 75% of men having no treatment progression at 3 years of follow-up. In men with negative PSMA PET-CT results, this increased to 85% of men.

PSMA theragnostics for metastatic castration resistant prostate cancer

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PSMA targeted theragnostic agents have shown tremendous potential in detecting and treating metastatic prostate cancer.

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The PSMA small molecular inhibitor-based imaging agents achieve extraordinary tumor to background ratios and the PSMA small molecule therapeutic agents have shown impressive therapeutic index in mCRPC.

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The development and optimization of PSMA theragnostic agents provides invaluable information that may help guide development of future theragnostics for other solid tumors.

There has been tremendous growth in the development of theragnostics for personalized cancer diagnosis and treatment over the past two decades. In prostate cancer, the new generation of prostate specific membrane antigen (PSMA) small molecular inhibitor-based imaging agents achieve extraordinary tumor to background ratios and allow their therapeutic counterparts to deliver effective tumor doses while minimizing normal tissue toxicity. The PSMA targeted small molecule positron emission tomography (PET) agents ¹⁸F-DCFPyL (2-(3-{1-carboxy-5-((6-(18)F-fluoro-pyridine-3-carbonyl)-amino)-pentyl}-ureido)-pentanedioic acid) and Gallium-68 (⁶⁸Ga)-PSMA-11 have been approved by the United States Food and Drug Administration (FDA) for newly diagnosed high risk prostate cancer patients and for patients with biochemical recurrence. More recently, the Phase III VISION trial showed that Lutetium-177 (¹⁷⁷Lu)-PSMA-617 treatment increases progression-free survival and overall survival in patients with heavily pre-treated advanced PSMA-positive metastatic castration-resistant prostate cancer (mCRPC). Here, we review the PSMA targeted theragnostic pairs under clinical investigation for detection and treatment of metastatic prostate cancer.

Use of Glycoproteins-Prostate-Specific Membrane Antigen and Galectin-3 as Primary Tumor Markers and Therapeutic Targets in the Management of Metastatic Prostate Cancer

Simple Summary

Prostate specific membrane antigen and galectins are proteins expressed on cell surface and their expression is associated with cancer growth and spread. The goal of this research was to look at the pattern of these two glycoproteins in the human prostate cancer microenvironment. Prostate specific membrane antigen and galectins-1,3 and 8 were the most frequently detected glycoproteins in various phases of this disease. Furthermore, prostate specific membrane antigen and galectin-3 expression are good indicators of tumor aggressiveness, and their combined expression can be valuable tool for prostate cancer diagnosis and treatment in future. Together, our findings reveal a tightly regulated “Prostate specific membrane antigen-galectin-pattern” that accompanies disease in prostate cancer and point to a key role for combined prostate specific membrane antigen and galectin-3 inhibitors in prostate cancer treatment along with standard chemotherapy.

Abstract

Galectins and prostate specific membrane antigen (PSMA) are glycoproteins that are functionally implicated in prostate cancer (CaP). We undertook this study to analyze the “PSMA-galectin pattern” of the human CaP microenvironment with the overarching goal of selecting novel-molecular targets for prognostic and therapeutic purposes. We examined CaP cells and biopsy samples representing different stages of the disease and found that PSMA, Gal-1, Gal-3, and Gal-8 are the most abundantly expressed glycoproteins. In contrast, other galectins such as Gal-2, 4–7, 9–13, were uniformly expressed at lower levels across all cell lines. However, biopsy samples showed markedly higher expression of PSMA, Gal-1 and Gal-3. Independently PSA and Gleason score at diagnosis correlated with the expression of PSMA, Gal-3. Additionally, the combined index of PSMA and Gal-3 expression positively correlated with Gleason score and was a better predictor of tumor aggressiveness. Together, our results recognize a tightly regulated “PSMA-galectin- pattern” that accompanies disease in CaP and highlight a major role for the combined PSMA and Gal-3 inhibitors along with standard chemotherapy for prostate cancer treatment. Inhibitor combination studies show enzalutamide (ENZ), 2-phosphonomethyl pentanedioic acid (2-PMPA), and GB1107 as highly cytotoxic for LNCaP and LNCaP-KD cells, while Docetaxel (DOC) + GB1107 show greater efficacy in PC-3 cells. Overall, 2-PMPA and GB1107 demonstrate synergistic cytotoxic effects with ENZ and DOC in various CaP cell lines.

Advances in PSMA theranostics

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PSMA is an appealing target for theranostic because it is a transmembrane protein with a known substrate that is overexpessed on prostate cancer cells and internalizes upon ligand binding.

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There are a number of PSMA theranostic ligands in clinical evaluation, clinical trial, or clinically approved.

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PSMA theranostic ligands increase progression-free survival, overall survival, and pain in patients with metastatic castration resistant prostate cancer.

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A major obstacle to PSMA-targeted radioligand therapy is off-target toxicity in salivary glands.

The validation of prostate specific membrane antigen (PSMA) as a molecular target in metastatic castration-resistant prostate cancer has stimulated the development of multiple classes of theranostic ligands that specifically target PSMA. Theranostic ligands are used to image disease or selectively deliver cytotoxic radioactivity to cells expressing PSMA according to the radioisotope conjugated to the ligand. PSMA theranostics is a rapidly advancing field that is now integrating into clinical management of prostate cancer patients. In this review we summarize published research describing the biological role(s) and activity of PSMA, highlight the most clinically advanced PSMA targeting molecules and biomacromolecules, and identify next generation PSMA ligands that aim to further improve treatment efficacy. The goal of this review is to provide a comprehensive assessment of the current state-of-play and a roadmap to achieving further advances in PSMA theranostics.

The promising role and prognostic value of miR-198 in human diseases

The importance of microRNAs (miRNAs or miRs) has attracted more and more attention. MiRNA is an approximately 22-nucleotide, single-stranded, non-coding RNA molecule that affects the expression of downstream target genes. MiRNAs regulate the occurrence and development of human diseases. The objective of this article is to explore the abnormal expression of miR-198 in a variety of human diseases. The relationships between abnormally expressed miR-198 and clinicopathological characteristics are also summarized. Its roles in various diseases and potential molecular mechanisms include involvement in many biological processes, such as cell cycle regulation, proliferation, invasion, migration, apoptosis, and drug resistance. The potential value of miR-198 for disease diagnosis, treatment, and especially, prognosis, are discussed. More in-depth research on miRNA will support the conversion from basic research to clinical applications of this molecule.