Therapy For Metastatic Prostate Cancer Research Articles

Combination of miR-99b-5p and Enzalutamide or Abiraterone Synergizes the Suppression of EMT-Mediated Metastasis in Prostate Cancer.

Prostate cancer (PCa) is the most frequently diagnosed cancer and second leading cause of cancer deaths among American men. Androgen deprivation therapy (ADT) has been systemically applied as a first-line therapy for PCa patients. Despite the initial responses, the majority of patients under ADT eventually experienced tumor progression to castration-resistant prostate cancer (CRPC), further leading to tumor metastasis to distant organs. Therefore, identifying the key molecular mechanisms underlying PCa progression remains crucial for the development of novel therapies for metastatic PCa. Previously, we identified that tumor-suppressive miR-99b-5p is frequently downregulated in aggressive African American (AA) PCa and European American (EA) CRPC, leading to upregulation of mTOR, androgen receptor (AR), and HIF-1α signaling. Given the fact that mTOR and HIF-1α signaling are critical upstream pathways that trigger the activation of epithelial-mesenchymal transition (EMT), we hypothesized that miR-99b-5p may play a critical functional role in regulating EMT-mediated PCa metastasis. To test this hypothesis, a series of cell biology, biochemical, and in vitro functional assays (wound healing, transwell migration, cell/ECM adhesion, and capillary-like tube formation assays) were performed to examine the effects of miR-99b-5p mimic on regulating EMT-mediated PCa metastasis processes. Our results have demonstrated that miR-99b-5p simultaneously targets MTOR and AR signaling, leading to upregulation of E-cadherin, downregulation of Snail/N-cadherin/Vimentin, and suppression of EMT-mediated PCa metastasis. MiR-99b-5p alone and in combination with enzalutamide or abiraterone significantly inhibits the EMT-mediated metastasis of AA PCa and EA CRPC.

Reproducible preclinical models of androgen receptor driven human prostate cancer bone metastasis.

Preclinical models recapitulating the metastatic phenotypes are essential for developing the next-generation therapies for metastatic prostate cancer (mPC). We aimed to establish a cohort of clinically relevant mPC models, particularly androgen receptor positive (AR+) bone metastasis models, from LuCaP patient-derived xenografts (PDX) that reflect the heterogeneity and complexity of mPC. PDX tumors were dissociated into single cells, modified to express luciferase, and were inoculated into NSG mice via intracardiac injection. The progression of metastases was monitored by bioluminescent imaging. Histological phenotypes of metastases were characterized by immunohistochemistry and immunofluorescence staining. Castration responses were further investigated in two AR-positive models. Our PDX-derived metastasis (PDM) model collection comprises three AR+ adenocarcinomas (ARPC) and one AR- neuroendocrine carcinoma (NEPC). All ARPC models developed bone metastases with either an osteoblastic, osteolytic, or mixed phenotype, while the NEPC model mainly developed brain metastasis. Different mechanisms of castration resistance were observed in two AR+ PDM models with distinct genotypes, such as combined loss of TP53 and RB1 in one model and expression of AR splice variant 7 (AR-V7) expression in another model. Intriguingly, the castration-resistant tumors displayed inter- and intra-tumor as well as organ-specific heterogeneity in lineage specification. Genetically diverse PDM models provide a clinically relevant system for biomarker identification and personalized medicine in metastatic castration-resistant prostate cancer.

Clinical Management of Advanced Prostate Cancer: Where Does Radiopharmaceutical Therapy Fit in the Treatment Algorithm?

Most men with newly appreciated metastatic prostate cancer are optimally treated with a backbone consisting of androgen receptor-directed therapy with or without taxane chemotherapy. Despite improvements in disease outcomes, prostate cancer remains an extremely heterogeneous disease with variable mechanisms of therapeutic resistance. As a result, it remains a leading cause of cancer-related death in men. Radiopharmaceutical therapy has emerged as an alternative, non-androgen receptor-directed treatment modality for metastatic castration-resistant prostate cancer that impacts patient survival and represents a potentially more personalized approach. In this review, we aim to outline the current treatment landscape for metastatic prostate cancer with a focus on radiopharmaceutical therapy, specifically 177Lu-PSMA-617. In addition, we illustrate various clinical challenges with 177Lu-PSMA-617 treatment to date and explore investigative efforts to leverage radiopharmaceutical therapies as part of combination regimens or earlier in the treatment algorithm to further improve patient outcomes. Finally, we introduce ongoing studies of alternative radiopharmaceutical therapies in metastatic prostate cancer that may be incorporated into the treatment algorithm pending further study.

Current clinical application of lutetium‑177 in solid tumors (Review).

Radionuclide-based therapy represents a novel treatment regimen for tumors. Among these therapies, lutetium-177 (177Lu) has gained significant attention due to its stability and safety, as well as its ability to emit both γ and β rays, allowing for both imaging with single photon emission computed tomography and tumor treatment. As a result, 177Lu can be used for both diagnosis and treatment for diseases such as prostatic and gastric cancer. Therefore, based on the available data, the present review provides a brief overview of the clinical applications of 177Lu-targeted radionuclide therapy in metastatic prostate cancer, neuroendocrine tumors and other types of solid tumors, and highlights the current therapeutic effect, reduction in damage to normal tissues and future research directions, including the development of new nuclides and the application of more nuclides in different tumors. In the future, such treatments could be used in more tumors.

Abstract 5967: Blockade of Wnt5A/ROR1 signaling as cancer stem cell targeting therapy for metastatic prostate cancer

Abstract BACKGROUND– Wnt5A and its non-canonical Wnt receptor, ROR1, have emerged as a promising new signaling pathway target for lethal, metastatic prostate cancer. Wnt5A has emerged as a significant marker of poor prognosis in circulating tumor cells (CTCs) of metastatic castration resistant prostate cancer (mCRPC) patients. ROR1 is expressed in lethal types of mCRPC, especially neuroendocrine prostate cancer (NEPC). A therapeutic ROR1 antibody, Zilovertamab, has been clinically tested in chronic lymphocytic leukemia (CLL) and metastatic breast cancer and shown to be safe. We sought to investigate Zilovertamab-based therapies for metastatic prostate cancer in pre-clinical model systems. HYPOTHESIS – Wnt5A/ROR1 signaling may mediate a cancer stem cell program which makes cells resistant to therapies which target the cell cycle and proliferation. Blocking ROR1 may reveal vulnerabilities which sensitize cancer cells to chemotherapies like docetaxel. METHODS– ROR1 expression was determined using RNASeq, qRT-PCR, FACS, IHC and Western blotting. ROR1 signaling was blocked using the anti-ROR1 therapeutic antibody, Zilovertamab, or CRISPRCas9 ROR1 knock out. Cell growth was measured using an Incucyte real time imaging system. Stem cell activity was assessed in 3D organoids. Cell cycle analysis was performed in live cells in 2D cultures and 3D organoids using the Fucci2BL bicistronic Fluorescent, Ubiquitination-based Cell Cycle Indicator reporter system. PDX PCSD13 tumor growth was measured via calipers and IVIS. RNASeq was performed on tumors. RESULTS– We showed that ROR1 was expressed at high levels in mCRPC cell lines: PC3, DU145, and in the bone metastatic prostate cancer PDX: PCSD13. CRISPR/Cas9 Knock out of ROR1 in PC3 and DU145 cells showed increased sensitivity to docetaxel inhibition of proliferation in vitro in 2D real time Incucyte proliferation assays and in 3D organoids. Organoid formation was significantly reduced in ROR1 KO cells. Cells expressing the FUCCI live cell cycle tracker showed docetaxel led to G2 arrest and ROR1 signaling inhibition increased efficacy of docetaxel induced cell cycle arrest. Treatment of PCSD13 PDX in vivo with Zilovertamab plus docetaxel synergistically increased tumor growth inhibition in vivo and modulated cancer stem cell and cell cycle expression profiles. CONCLUSIONS– Cancer stem cells represent the fundamental precursors from which all diverse tumor subpopulations evolve. Thus, therapeutic targeting of these tumor initiating stem/progenitor cells may prevent the evolutionary diversification of a tumor and overcome a critical clinical barrier to cancer treatment. We showed synergistic response in our PDX and PCs cell line models to Zilovertamab plus docetaxel. We are now conducting a phase 1b clinical trial with zilovertamab plus docetaxel in patients with metastatic CRPC (CirmD, NCT05156905, PI R Mckay). Citation Format: Christina A.M. Jamieson, Jamillah Murtadha, Christopher S. Oh, Michelle T. Muldong, Niloofar Etemadfard, Evodie Koutouan, Young E. Yoon, Sanghee Lee, Oh Kwon, Jong J. Oh, Min S. Kim, Karl Willert, Nicholas A. Cacalano, Catriona H.M. Jamieson, Terry Gaasterland, Rana R. Mckay, Christopher J. Kane, Anna A. Kulidjian, Charles E. Prussak. Blockade of Wnt5A/ROR1 signaling as cancer stem cell targeting therapy for metastatic prostate cancer [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 5967.

Abstract 3036: Sensitivity of ONC201/TIC10 cancer therapeutic on neuroendocrine prostate cancer (NEPC) and neuroendocrine differentiation (NED)

Abstract Although androgen deprivation therapy and androgen receptor (AR) blockade are highly effective therapies for metastatic prostate cancer (PCa), most patients develop resistance, leading to castration-resistant prostate cancer (CRPC). A subset of CRPC shows neuroendocrine prostate cancer (NEPC) features, which are associated with poor prognosis and limited therapeutic strategies. NEPC is characterized by oncogenic driver activation and epigenetic changes, partly controlled by transcription factors like BRN2 and SOX2. AR has been shown to suppress BRN2 transcription, which is required for NEPC, and BRN2-dependent regulation of the NEPC marker SOX2 (Bishop et al., 2017). Dordaviprone (ONC201/TIC10) is a first-in-class small molecule that antagonizes DRD2, induces tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), and activates the integrated stress response (ISR). Neuroendocrine tumors express significant DRD2 levels, suggesting ONC201 as a potential therapeutic strategy in NEPC or when drivers for disease progression are overexpressed (OE). PCa cell lines PC3, DU145, LNCaP, and 22RV1 are ONC201 sensitive, with IC50=2.87 μM, 3.18 μM, 1.31 μM, and 1.16 μM, respectively (Ding et al., 2023). To characterize the association of BRN2/SOX2 dysregulation with ONC201 sensitivity, we transiently OE BRN2/SOX2 in PCa. We hypothesized that markers of neuroendocrine differentiation (NED), activation of the ISR, TRAIL, and ClpP and dopamine receptor expression contribute to NEPC cell death and sensitivity to ONC201. We performed CellTiter-Glo experiments to assess viability after 96 hours ± BRN2 OE. DU145 cells with BRN2 OE increased their sensitivity to ONC201 (IC50=2.75 µM) compared to empty vector (IC50=3.03 µM). Colony formation assays were conducted in PCa and analyzed 7 days after ONC201 treatment to show ONC201 effect on PCa cell lines. DU145 was treated at 0.5, 1, and 2 µM of ONC201. There were 95 ± 3.22 colonies for the control group, 83 ± 5.22 colonies with 0.5 µM, 74 ± 3.64 colonies with 1 µM, and 8 ± 2.03 colonies with 2 µM ONC201. DU145 showed a significant reduction in colony-forming ability when treated with 1 and 2 uM ONC201 compared to the control, with P values of <0.05 and <0.0001, respectively. We OE BRN2 and observed changes in NED markers and ISR pathway. In PC3, FoxO1 and ATF4 levels increased. In DU145, FoxO1, ENO2, PGP9.5, CgA, and ATF4 levels decreased. We reveal that DU145 OE at 48 hours does not result in greater expression of NEPC markers. BRN2 OE significantly increased PCa cell sensitivity to ONC201 and was evident without an increase in common phenotypical markers used for NEPC assessment (FoxO1, ENO2, PGP9.5, CgA). Expression change was not shown when PCa had an integral AR pathway. Ongoing efforts are observing ONC201 treatment effects on NED markers and the TRAIL pathway due to BRN2 OE and showing increased sensitivity of PCa to ONC201 with BRN2 OE. Citation Format: Elizabeth C. Ding, Maximilian Pinho-Schwermann, Shengliang Zhang, Connor Purcell, Wafik S. El-Deiry. Sensitivity of ONC201/TIC10 cancer therapeutic on neuroendocrine prostate cancer (NEPC) and neuroendocrine differentiation (NED) [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 3036.

Abstract 560: IGF1 induces the expression of CYR61 in metastatic prostate cancer

Abstract The cysteine-rich angiogenic inducer 61 (CYR61) is a member of the cellular communication network (CCN) protein family that can be induced by growth factors. CYR61-specific functions are dependent on cellular context. In prostate cancer (PCa), CYR61 contributes to cell growth and survival through its interactions with extracellular ligands, such as integrins avb3 and a6b4, in the extracellular matrix space. Interestingly, CYR61 contains an insulin-like growth factor-binding protein domain suggesting that it may interact with insulin-like growth factor-I (IGF1). High serum levels of IGF1 are directly linked to PCa development and recently have been studied as a predictor of metastatic disease. Given the important roles that IGF1 and CYR61 play in PCa and their potential interaction, it is critical to investigate their molecular interplay. The correlation between PCa aggressiveness and circulating levels of CYR61 and IGF1 is poorly studied. Our goal was to assess the contribution of CYR61-IGF1 interaction to PCa cell proliferation. Their combined role may explain a proportion of aggressive PCa. This study was designed to characterize the role of IGF1-induced expression of CYR61 in metastatic PCa cellular models and to determine if this interaction contributes to aggressive tumor properties (e.g., proliferation, migration, tumorsphere formation). Using immunoblotting, we demonstrated that CYR61 is upregulated in the metastatic cell line PC3. Furthermore, optimized knockdown of CYR61 using siRNA significantly reduced PC3 cell proliferation, viability, and prostasphere formation. To examine the underlying mechanisms associated with IGF1 signaling, we assessed the activation of either the PI3/Akt and MAPK pathways in PC3 cells with CYR61 silencing. CYR61 siRNA-mediated knockdown decreased activation of the PI3/Akt pathway but did not affect the MAPK pathway. In addition, we found that IGF1 induces protein expression of CYR61 in a time-dependent manner, validated by both immunoblotting and confocal microscopy. In conclusion, these data provided evidence that CYR61 expression is induced by IGF1, and its inhibition decreased the capacity of metastatic PCa cells to proliferate, indicating a potential utilization of CYR61 inhibition in the therapy of metastatic PCa. Citation Format: Greisha L. Ortiz Hernandez, Mya Walker, Leanne Woods-Burnham, Rick A. Kittles, Carlos A. Casiano, Susan Neuhausen. IGF1 induces the expression of CYR61 in metastatic prostate cancer [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 560.

Lutetium-177 Labelled Anti-PSMA Monoclonal Antibody (Lu-TLX591) Therapy for Metastatic Prostate Cancer: Treatment Toxicity and Outcomes.

Whilst prostate cancer is the fourth most common cancer globally, effective therapies for patients with advanced disease are lacking. In recent years, interest in using theranostic agents to treat castrate-resistant prostate cancer (CRPC) and metastatic prostate cancer has emerged. Lu-TLX591 monoclonal antibody is a potential agent of significance; however, to date, reports on its toxicity and efficacy have been limited to small clinical trials in heavily pretreated patients. This retrospective study describes the real-world toxicity and efficacy profile of Lu-TLX591. Eighteen patients received Lu-TLX591 at two private oncology centres in Australia. Patients were eligible if they had CRPC or metastatic prostate cancer and prostate-specific membrane antigen (PSMA)-avid disease confirmed by PSMA-positron emission tomography (PET). Patients received two cycles of Lu-TLX591 monoclonal antibody (177 Lu-DOTA-rosopatamab) each dosed from 1.01-2.85 GBq, 14 days apart. Patient side effects, blood test results and radiology reports were recorded on the patient's electronic medical record (eMR). Prominent side effects included fatigue (55.6%), anorexia (16.7%), nausea (11.1%), and transfusion reactions (11.1%). All-grade haematological toxicities included lymphopenia (61.1%), anaemia (22.2%), leukopenia (27.8%), neutropenia (27.8%), and thrombocytopenia (27.8%). Grade 4 toxicity included lymphopenia (6.7%) and thrombocytopenia (6.7%). Patients' prostate-specific antigen (PSA) responses were as follows; ≥ 30% PSA decline (27.8%), ≥ 50% PSA decline (11.4%) and any PSA decline (38.9%). Follow-up radiology revealed 54.5% stable disease, 45.4% disease progression and 9.1% disease regression. Lu-TLX591 was safely administered at acceptable toxicity and its efficacy reflects previous clinical trials. Larger studies are required and are underway (NCT04786847; NCT05146973; NCT04876651) to determine Lu-TLX591 effectiveness amongst different prostate cancer populations and compare its efficacy against peptide-based radiopharmaceutical agents.

Strength through unity: Alkaline phosphatase-responsive AIEgen nanoprobe for aggregation-enhanced multi-mode imaging and photothermal therapy of metastatic prostate cancer

Strength through unity: Alkaline phosphatase-responsive AIEgen nanoprobe for aggregation-enhanced multi-mode imaging and photothermal therapy of metastatic prostate cancer

Stereotactic ablative radiation therapy in metastatic prostate cancer.

The evolving role of stereotactic ablative radiation therapy (SABR) as metastasis-directed therapy (MDT) for oligometastatic prostate cancer (omPCa) will be discussed. Oligometastatic disease (OMD) is an intermediate state between localized and wide-spread malignant disease. OMD has recently been spotlighted given the increasing demonstration of clinical benefit from local therapies despite presence of metastatic disease and allure of the curative potential of MDT in select cases. Among the different forms of MDT, SABR has rapidly become a widely adopted treatment modality. Significant efforts in this space have focused on omPCa, owing to its relatively indolent biology, presence of a sensitive and specific serum biomarker and recent advances in molecular imaging. While most studies have evaluated the role of SABR MDT in hormone sensitive omPCa, new emerging clinical data also suggests benefits of SABR MDT for even castration-resistant disease. Treating omPCa with SABR MDT appears to generate an efficacy signal with minimal morbidity across both hormone-sensitive and castration-resistant disease. However, additional definitive omPCa trial data are needed. Future research efforts should investigate biomarkers for this heterogeneous disease space and the role of SABR MDT in combination with systemic agents to improve upon standard of care treatments.

A study to evaluate patient benefit/risk preferences for treatment of metastatic prostate cancer (mPC) in Hong Kong: A discrete choice experiment.

104 Background: The patient’s preference for treatment is dynamic across different cultures and at various stages of cancer. Yet little is known regarding their priorities in making treatment decisions. The study's primary objective is to examine the preference weightings in terms of risk/ benefit attributes of therapy in metastatic prostate cancer (mPC) patients in both the hormone-sensitive (mHSPC) and castration-resistant (mCRPC) settings. Methods: This is a non-interventional cross-sectional survey study. A discrete choice experiment was used to assess their priorities on treatment options. 300 consecutive patients with mPC (200 mHSPC and 100 mCRPC) diagnosed within 5 years were recruited from the specialty clinics of our hospital from Feb 2023 to Jul 2023. A facilitated group interview session of 5 patients was conducted to evaluate the importance and relevance of potential attributes selected from the literature search. Five attributes were adopted, and each has 3 levels compromised between real-life rates and expectations of patients from the interview session. Patients were randomized into 2 blocks by recruitment sequence and chose 1 medication profile out of 2 throughout the 9 questions in each block of the questionnaire. A mixed logit model was used for data analysis. Results: Median age was 75 (IQR:71-81). One hundred and seventy (56.7%) had no income, and 245 (81.7%) claimed to take care of themselves. The mean maximum amount affordable for treatment was US$20,456 (SD:43,568), and 160 (53.3%) said they would not consider further treatment if the cost exceeded their affordability. Compared to intravenous formulation, oral medication once/day had a non-statistically significant favorable preference (0.06 p:0.272), and oral medication twice/day had a negative statistically significant preference (-0.20 p:0.040). The percentage of retained self-care ability (4.37 p<0.001) and percentage of extension in life expectancy (2.83 p<0.001) had a statistically significant favorable preference. In contrast, the chance of adverse effects leading to complicated medication treatment or hospitalization (-6.97, p<0.001) and treatment cost (in HK$ million) (-3.14 p<0.001) had a negative statistically significant preference. The mCPRC group was more sensitive to changes in treatment cost (-3.61 vs. -2.97), percentage of extension in life expectancy (3.47 vs. 2.55) and the chance of adverse effects (-7.55 vs -6.80) than the mHSPC group. Those who could afford treatment were more sensitive to the percentage of retained self-care ability (4.89 vs. 4.02) and the chance of adverse effects (-7.57 vs -6.70) than those who could not. Conclusions: The chance of adverse effects took the largest weighting in treatment decisions, followed by the percentage of retained self-care ability.

Real-world genomic testing patterns in patients with prostate cancer.

97 Background: The armamentarium of therapies for metastatic prostate cancer (PCa) has now expanded to include genomically targeted agents and CPIs. Men with both somatic and germline alterations in the DNA damage repair (DDR) pathway, most commonly BRCA2, are candidates for PARP inhibitors. Recent data from the PROPEL and MAGNITUDE trials led to approval of PARP inhibitors in combination with novel hormonal therapies earlier in the PCa continuum, in the first-line metastatic castrate-resistant space. Some PCas harbor genomic alterations, such as TMB>10 m/Mb and MSI high, which predispose to increased responses to CPIs, leading to tumor agnostic approval of pembrolizumab in these patient populations. However, it is imperative to perform timely genomic testing to assess for presence of these alterations. Methods: We conducted a 15-question survey using the Qualtrics XM software to assess genomic testing patterns of various providers in academic and community settings managing PCa patients. The survey link was distributed electronically to providers predominantly in the Western United States. Results: A total of 47 survey responses were received, with 59.6% (28/47) self-identifying as medical oncologists (Onc), 21.3% (10/47) as urologists (Uro), 4.3% (2/47) as radiation oncologists, 8.5% (4/47) as advanced practitioners, and 6.4% (3/47) as other. Academic Onc comprised 23.4 % (11/47), community Onc comprised 36.2% (17/47), academic Uro comprised 17.0% (8/47), and community Uro comprised 4.6 % (2/47) of providers. Timing of ordering of germline and somatic genomic testing by selected provider type is outlined in the Table. Conclusions: Given availability of targeted therapies in PCa management, ordering germline and somatic germline genomic testing is imperative. Despite the small sample size, several trends emerge from this dataset. Oncs at academic centers tend to order genomic testing earlier than Oncs at community practices, while Uros were less likely to order genomic testing when compared to Oncs in general. [Table: see text]

Hormonal therapy in metastatic prostate cancer

Hormonal therapy in metastatic prostate cancer

Biochemical progression free and overall survival among Black men with stage IV prostate cancer in South Africa: Results from a prospective cohort study.

Men of African descent are disproportionately affected by prostate cancer (PCa), and many have metastatic disease at presentation. In South Africa (SA), androgen deprivation therapy (ADT) is the first-line treatment for stage IV PCa. To identify predictors of overall survival (OS) in Black South African men with stage IV PCa treated with ADT. Men diagnosed with prostate cancer (3/22/2016-10/30/2020) at Chris Hani Baragwanath Academic Hospital in Soweto, Johannesburg, were recruited for the Men of African Descent with Cancer of the Prostate study. We included men with newly diagnosed stage IV PCa treated with ADT who had a prostate-specific antigen (PSA) level drawn prior to initiation of ADT and had ≥1 PSA drawn ≥12 weeks after ADT start. We used Kaplan-Meier statistics to estimate OS and Cox regression models to identify predictors of OS. Of the 1097 men diagnosed with prostate cancer, we included 153 men with stage IV PCa who received ADT and met PSA requirements. The median age was 68.0 years (interquartile range 64-73 years). Median OS from time of ADT initiation was 3.39 years (95% confidence interval (CI): 3.14%-noncalculable), while biochemical progression-free survival was 2.36 years (95% CI: 2.03%-3.73%). Biochemical progression (HR 3.52, 95% CI: 1.85%-6.70%), PSA nadir level >4 ng/mL (HR 3.77, 95% CI: 1.86%-7.62%), alkaline phosphatase level at diagnosis >150 IU/dL (HR 3.09, 95% CI: 1.64%-5.83%), and hemoglobin at diagnosis <13.5 g/dL (HR 2.90, 95% CI: 1.28%-6.56%) were associated with worse OS. In this study, we identified factors associated with poor OS among Black South African men with stage IV PCa treated with ADT. These factors may be useful in identifying patients for upfront treatment escalation, including the use of docetaxel chemotherapy or escalation of therapy at the time of biochemical progression. In this study, we found that high alkaline phosphatase level, anemia at diagnosis, and high PSA nadir after initiation of androgen deprivation therapy are associated with worse overall survival among Black South African men treated with androgen deprivation therapy for metastatic prostate cancer.

PSMA-Directed Radioligand Therapy for Metastatic Prostate Cancer

PSMA-Directed Radioligand Therapy for Metastatic Prostate Cancer

The Theranostic Optimization of PSMA-GCK01 Does Not Compromise the Imaging Characteristics of [99mTc]Tc-PSMA-GCK01 Compared to Dedicated Diagnostic [99mTc]Tc-EDDA/HYNIC-iPSMA in Prostate Cancer

PurposeRadiolabeled PSMA-ligands play a major role in today’s nuclear medicine. Since approval of [177Lu]Lu-PSMA-617 for therapy of metastatic prostate cancer, availability of 177Lu became bottleneck of supply due to the high demand. Recently, a theranostic PSMA-ligand, PSMA-GCK01, was developed which can be labeled either diagnostically with 99mTc or therapeutically with 188Re with both nuclides available from well-known generator systems. This novel tracer might aid to overcome aforementioned supply limitations. In this investigation, the biodistribution and general imaging characteristics of [99mTc]Tc-PSMA-GCK01 were compared with the diagnostic reference compound [99mTc]Tc-EDDA/HYNIC-iPSMA in patients with advanced stage prostate cancer. In addition, the binding of both ligands to PSMA was analyzed at the molecular level using molecular docking.ProceduresTwo cohorts (n = 19 vs. n = 21) of patients with metastatic castration-resistant prostate cancer matched for age, tumor stage, and Gleason score underwent a planar gamma camera imaging with [99mTc]Tc-EDDA/HYNIC-iPSMA or [99mTc]Tc-PSMA-GCK01 prior to PSMA-ligand therapy for PSMA-phenotyping. The imaging data were retrospective analyzed for salivary gland, kidney, liver, soft tissue, and tumor uptake on a semi-automated ROI-analysis using HERMES Medical Solutions AB (HMS, Sweden).ResultsThe data sets were semi-automated quantified on a ROI-based analysis. The tumor-to-background presented equal results of [99mTc]Tc-PSMA-GCK01 compared to [99mTc]Tc-EDDA/HYNIC-iPSMA. The physiological PSMA-positive organs like salivary gland presented also equal uptake in counts/MBq (salivary gland median 9.48 [99mTc]Tc-PSMA-GCK01 vs. median 9.11 [99mTc]Tc-EDDA/HYNIC-iPSMA), while liver-to-kidney ratio presented a slight shift to the liver parenchyma using [99mTc]Tc-PSMA-GCK01 (0.83) compared to [99mTc]Tc-EDDA/HYNIC-iPSMA (0.55) with no statistical significance. This is in agreement with the results from the docking study revealing only a minor difference in the docking scores for both ligands.ConclusionsThe novel theranostic tracer [99mTc]Tc/[188Re]Re-PSMA-GCK01 demonstrates comparable general imaging characteristic with the reference compound [99mTc]Tc-EDDA/HYNIC-iPSMA. These results pave the way for the PSMA-targeting imaging and theranostic agents for a broader, rather low-cost, generator applied radio-ligand therapy utilization.

PSMA-Expression Is Highly Associated with Histological Subtypes of Renal Cell Carcinoma: Potential Implications for Theranostic Approaches.

In renal cell carcinoma (RCC), accurate imaging methods are required for treatment planning and response assessment to therapy. In addition, there is an urgent need for new therapeutic options, especially in metastatic RCC. One way to combine diagnostics and therapy in a so-called theranostic approach is the use of radioligands directed against surface antigens. For instance, radioligands against prostate-specific membrane antigen (PSMA) have already been successfully used for diagnosis and radionuclide therapy of metastatic prostate cancer. Recent studies have demonstrated that PSMA is expressed not only in prostate cancer but also in the neovasculature of several solid tumors, which has raised hopes to use PSMA-guided theranostic approaches in other tumor entities, too. However, data on PSMA expression in different histopathological subtypes of RCC are sparse. Because a better understanding of PSMA expression in RCC is critical to assess which patients would benefit most from theranostic approaches using PSMA-targeted ligands, we investigated the expression pattern of PSMA in different subtypes of RCC on protein level. Immunohistochemical staining for PSMA was performed on formalin-fixed, paraffin-embedded archival material of major different histological subtypes of RCC (clear cell RCC (ccRCC)), papillary RCC (pRCC) and chromophobe RCC (cpRCC). The extent and intensity of PSMA staining were scored semi-quantitatively and correlated with the histological RCC subtypes. Group comparisons were calculated with the Kruskal-Wallis test. In all cases, immunoreactivity was detected only in the tumor-associated vessels and not in tumor cells. Staining intensity was the strongest in ccRCC, followed by cpRCC and pRCC. ccRCC showed the most diffuse staining pattern, followed by cpRCC and pRCC. Our results provide a rationale for PSMA-targeted theranostic approaches in ccRCC and cpRCC.

FRI242 Primary And Secondary Adrenal Insufficiency Post Transsphenoidal Surgery In Patient On Abiraterone Therapy

Abstract Disclosure: R.O. Akande: None. J. Abramowitz: None. S. Mirfakhraee: None. Introduction: This case report describes the co-existence of primary and secondary adrenal insufficiency in a patient who received abiraterone therapy for metastatic prostate cancer and had transsphenoidal surgery for symptomatic pituitary adenoma. It sheds light on the presentation of the patient and explains the subsequent management. Clinical Case: A 67-year-old man with a history of metastatic prostate cancer (status post prostatectomy and radiation) and recent transsphenoidal surgery for pituitary adenoma presented with 3+ pedal edema. The patient had been discharged on hydrocortisone as per neurosurgery protocol and continued abiraterone after his transsphenoidal surgery. His pedal edema started two months after discharge. He denied fatigue, nausea, and dizziness. His vital signs and electrolytes, including serum potassium, were within normal limits. The patient was diagnosed with mineralocorticoid excess in the context of combined primary and secondary adrenal insufficiency. His hydrocortisone was changed to prednisone 5mg daily and his pedal edema subsequently resolved. Conclusion: Abiraterone, a hormonal therapy for the treatment of metastatic prostate cancer, is an irreversible inhibitor of CYP17, a microsomal enzyme with 17 alpha-hydroxylase and 17,20-lyase activities. This inhibition reduces cortisol and androgen concentrations while stimulating ACTH production. Thus, abiraterone use led to primary adrenal insufficiency in this patient. As a result of the 17 alpha-hydroxylase and 17,20-lyase pathway inhibition, there is increased production of deoxycorticosterone, which can lead to fluid retention. This patient was post pituitary surgery with partial secondary adrenal insufficiency and received hydrocortisone postoperatively as an appropriate glucocorticoid replacement in this setting. He developed pedal edema due to mineralocorticoid excess from abiraterone use while on hydrocortisone therapy. He was placed on prednisone, a more potent synthetic glucocorticoid than hydrocortisone, with subsequent rapid resolution of his edema. Presentation: Friday, June 16, 2023

B-type Plexins promote the GTPase activity of Ran to affect androgen receptor nuclear translocation in prostate cancer.

Resistance to anti-androgen therapy for metastatic prostate cancer is a major clinical problem. Sema3C promotes resistance to androgen withdrawal via its receptor, PlexinB1. Activation of PlexinB1 promotes the ligand-independent nuclear translocation of the androgen receptor (AR), which may contribute to resistance to androgen deprivation therapy. However, the mechanism by which PlexinB1 promotes nuclear translocation is unclear. We show here that PlexinB1 and B2 regulate nuclear import by acting as GTPase activating proteins (GAPs) for the small RasGTPase Ran, a key regulator of nuclear trafficking. Purified PlexinB1/B2 protein catalyses the hydrolysis of RanGTP, and mutations in the GAP domain of PlexinB1 inhibit this activity. Activation of PlexinB1/B2 with Sema4D decreases the levels of RanGTP, while PlexinB1 or B2 depletion increases the levels of activated Ran in the cell. Ran directly associates with B-type plexins in a GTP-dependent manner. Sema4D is internalised by endocytosis, and PlexinB1 and Ran display overlapping patterns of expression. Furthermore, Sema4D/PlexinB1-induced AR nuclear translocation is dependent on the GAP domain of PlexinB1 and is blocked by the expression of non-functional Ran mutants. Depletion of PlexinB1 decreases the nuclear/cytoplasmic ratio of Ran, indicative of a higher RanGTP/GDP ratio. Plexins may promote the growth of androgen-independent prostate cancer through their activity as RanGAPs.

SERUM TESTOSTERONE AS A MARKER OF RESPONSE TO ANDROGEN DEPRIVATION THERAPY IN METASTATIC PROSTATE CANCER

Introduction: Prostate cancer (PCa) is the second most widespread cause of cancer and the sixth foremost cause of cancer death among men worldwide. The sustained presence of particular hormones and growth factors stimulates the prostate, such as other sex accessory tissues, in its growth, maintenance, and secretory function. In the current study, we investigated the association of serum testosterone level and prostate-specific antigen (PSA) level before androgen deprivation therapy in metastatic PCa (mPCa) treated with hormone therapy. Methods: This retrospective cohort was conducted from July 2017 to December 2019 in the Department of Urology, Post Graduate Institute of Medical Education and Research, Chandigarh on patients diagnosed with mPCa of age &gt;40 years. Total serum testosterone was measured by Electro chemiluminescent immune assay before the treatment. PSA in serum specimens was evaluated. Results: The mean age was 67.74±8.12 (55–80) years. Serum PSA levels at baseline, 3 months were 530.98±617.28 (ng/dL), and 56.31±89.04 (ng/dL), respectively. The baseline S. testosterone was 288.89±246.53 (ng/mL). Weak negative correlation between the two (p=0.051) As the serum testosterone levels decrease the PSA levels increase and vice-versa. Positive correlation between baseline testosterone and PSA decline (p&lt;0.05). On histopathology, 58.7% (n=71) of the patients had perineural involvement, while 41.3% (n=50) did not have perineural involvement. Conclusion: We conclude that the effect of testosterone might have a possible role in the assessment of treatment response as assessed by PSA. However, the exact implication and its role in disease assessment need to be examined in a larger prospective cohort.