Abstract Purpose: The phase II ARROW study was designed to evaluate radioligand therapy (RLT) with 131I-LNTH-1095, an iodine-131–labeled small molecule targeting prostate-specific membrane antigen (PSMA), in combination with enzalutamide in subjects with metastatic castration-resistant prostate cancer after progression on prior abiraterone therapy. Patients and Methods: Men ≥18 years with PSMA-positive prostate cancer (PSMA PET tracer uptake >1× liver SUVmean in all CT-measurable lesions) were randomly assigned 2:1 to 131I-LNTH-1095 (4 cycles of 3.7 GBq/dose every 8 weeks) + enzalutamide (160 mg orally once daily) versus enzalutamide alone. The primary endpoint was PSA50 response. Secondary endpoints included radiographic progression-free survival (rPFS), objective response rate, overall survival (OS), and safety. Results: Of 177 screened subjects, 120 were randomly assigned (80: 131I-LNTH-1095 + enzalutamide; 40: enzalutamide monotherapy). PSA50 response was 62.9% [95% confidence interval (CI), 50.5–74.1] for 131I-LNTH-1095 + enzalutamide versus 31.3% (16.1–50) for enzalutamide alone (P = 0.003). The median rPFS was 14.0 months (95% CI, 8.64–18.20) for 131I-LNTH-1095 + enzalutamide versus 11.5 months (2.79–18.43) for enzalutamide alone (P = 0.10). The incidence of grade ≥3 treatment-emergent adverse events (TEAE) was 65.8% for 131I-LNTH-1095 + enzalutamide versus 41% for enzalutamide monotherapy; the most frequent TEAEs were fatigue (75% vs. 53.8%), nausea (59.2% vs. 33.3%), thrombocytopenia (51.3% vs. 0%), and decreased appetite (48.7% vs. 17.9%), respectively. Two deaths in the 131I-LNTH-1095 + enzalutamide group were considered treatment-related. The study was not powered to detect rPFS and OS differences. Conclusions: 131I-LNTH-1095 + enzalutamide was associated with a statistically significant improvement in PSA50 response compared with enzalutamide alone despite a lower dosing schedule (4 cycles of 3.7 GBq/dose every 8 weeks) than the other approved PSMA RLT agents. Grade ≥3 adverse events were more frequent with combination therapy, particularly hematologic toxicity.

Time to First New Anti-Cancer Treatment

rPFS, as determined by the local investigator (A), and OS (B).

Myeloid-derived suppressor cells (MDSCs) in the tumor microenvironment (TME) limit the efficacy of adoptive T cell therapies, highlighting the need to overcome tumor-associated immunosuppression. Sphingosine-1-phosphate (S1P), is an abundant signaling lipid in the TME. Here, we show that inhibition of sphingosine kinase-2 (SphK2), the enzyme generating S1P in MDSCs, reduces the suppressive activity of monocytic MDSCs (M-MDSCs) while promoting their differentiation toward a mature, immunogenic phenotype characterized by enhanced antigen presentation. Pharmacological SphK2 inhibition enhances the response to anti-PD-1 therapy in preclinical models of checkpoint-resistant breast, bladder, and melanoma cancers by mitigating MDSC-mediated suppression and limiting tumor progression. Mechanistically, S1P directly binds acetyl-CoA carboxylase-1 (ACC1) to inhibit its activity, thereby rewiring fatty-acid metabolism. Lowering intracellular S1P restores ACC activity, promotes phosphatidylcholine synthesis, and reduces MDSC immunosuppression. These findings identify the SphK2-ACC-phospholipid axis as a metabolic checkpoint controlling the immunogenicity of MDSCs and a potential therapeutic target for enhancing cancer immunotherapy.

Summary of 18F-piflufolastat maximum standardized uptake value (SUVmax) at baseline and EOT.

Demographic and Baseline characteristics of the Safety Population

Most Common Serious Treatment-Emergent Adverse Events

Best PSA decline from baseline (%), any measurement.

Summary of 18F-piflufolastat SUVmax by Number of 131I-LNTH-1095 Therapy Cycles

Effects of LCL768 on the growth of UM-SCC-1A-derived xenograft HNSCC tumors in vivo.

LCL768 reduces TCA cycle metabolism in HNSCC cells.

LCL768-mediated mitophagy is independent of p17, cell line, and induces Drp1’s nitrosylation.

Bioactive ceramide induces cell death in part by promoting mitophagy. C18-ceramide levels are commonly reduced in head and neck squamous cell carcinoma, which correlates with poor prognosis, suggesting the potential of harnessing ceramide for cancer treatment. In this study, we evaluated the ability of the ceramide analog D-erythro-14-(1-pyridinium)-N-octadecanoyl-sphingosine selenite (LCL768) to induce mitophagy and metabolic stress in head and neck squamous cell carcinoma. Mechanistically, LCL768 induced ceramide synthase 1 (CerS1)-mediated endogenous C18-ceramide accumulation in mitochondria to mediate mitophagy, which did not require the CerS1 transporter p17/PERMIT but was dependent on DRP1 activation via nitrosylation at C644. DRP1 facilitated the anchoring of the endoplasmic reticulum (ER) and mitochondrial membranes by promoting the association between phosphatidylethanolamine in the ER and cardiolipin in mitochondrial membranes. Mutations of Drp1 that prevented its binding to ER and mitochondrial membranes blocked CerS1/C18-ceramide mitochondrial accumulation, inhibiting LCL768-mediated mitophagy. In addition, LCL768-driven mitophagy altered mitochondrial metabolism, resulting in fumarate depletion and leading to tumor suppression in vivo. Exogenous fumarate supplementation prevented LCL768-mediated mitophagy, mitochondrial trafficking of CerS1, ER-mitochondrial tethering, and tumor suppression in mice. Fumarate metabolism was associated with PARKIN succination at a catalytic cysteine (Cys431), inhibiting its association with PINK1 and ubiquitin, thereby preventing mitophagy. LCL768-induced fumarate depletion attenuated PARKIN succination to promote PARKIN activation and mitophagy, indicating a feedforward mechanism that regulates mitophagy and fumarate metabolism through PARKIN succination. These data provide a mechanism whereby LCL768/CerS1-C18-ceramide-mediated mitophagy and tumor suppression are regulated by Drp1 nitrosylation, fumarate depletion, and PARKIN succination, providing a metabolic stress signature for lethal mitophagy.Significance: The identification of a metabolic link between ceramide-induced mitophagy, fission, and fumarate depletion reveals an effective tumor suppressive strategy for head and neck squamous cell carcinoma.

Drp1 mutations alter its ER or mitochondrial membrane interactions and change cancer metabolism by LCL768.

Abstract Background: Non-Hispanic Black American patients (BA) with prostate cancer (PCa) tend to fare worse than their Non-Hispanic White American counterparts (WA), even with consideration of socioeconomic disparities. Clinically, BA face diagnosis at younger age with worse clinical outcomes. Stromal cells adjacent to the tumor, including carcinoma-associated fibroblasts (CAFs), play a critical role in tumorigenesis of PCa. Dysfunction in the tumor microenvironment play a crucial role in mediating prostate cancer tumorigenesis and is emerging as a key target for cancer therapy in solid tumors. Methods: To investigate whether DNA methylation varies in tumor adjacent stroma (TAS) among PCa patients with different geographical ancestries, areas immediate adjacent to tumor (i.e., less than 1mm) removed for methylation analysis. A complete genome-wide DNA methylation of PCa stroma using 17 BA and 15 WA patients who had radical prostatectomy was carried out. Methyl-Captured (mCap) sequencing data was generated for TAS of prostate cancer FFPE tissues. Methylated sites were identified with the MACS2 callpeak function using a band width of 300 bp and a false discovery rate of q < 0.05. A consensus peak set was derived from the aligned reads of BA and WA prostate cancer stroma samples that were sequenced. Pathway analysis was performed using Ingenuity Pathway Analysis (IPA) tools. CAFs from primary tumors of BA and WA was prepared by tissue culture and treated with demethylating agent (i.e., 5-Azacytidine) for 24 hours followed by maintenance of the cells in drug-free medium for 7-10 days and subjected to mCap sequencing. Results: We found racial disparities in genome-wide DNA methylation in TAS between the two populations in which BA PCa patients had significantly increased in global DNA methylation as compared to their WA counterpart (p value < 0.001). Hypomethylation occurred in CAFs from BA patients treated with 5-Azacytidine. We identified 1041 methylated sites corresponding to 409 unique genes that were differentially methylated in BA vs WA (p value < 0.05). Pathway analysis identified significant association between methylated genes in BA TAS and immune response pathways including IL-13, JACK/STAT, T cell receptors, NF-KB, and PD-1, PDL1 cancer immunotherapy. Evaluation of the methylome profile between patients based on the post-prostatectomy resection margins, negative (R0) vs positive (R1), showed that R0 resections had significantly greater (p value < 0.001) methylation than R1 resections. Further analysis identified 984 sites corresponding to 373 differentially methylated, unique genes (p value < 0.05). Conclusion: Tumor-adjacent stroma of BA prostate cancer patients has a distinct methylome as compared to WA patients. Differences in immune response pathways suggests a distinct immune response in TAS in men of different races. Citation Format: Santosh Sankaran, James Nguyen, Tara Jennings, Vinay Kumar, Michael B. Lilly, Michael M. Ittmann, Patricia Castro, Liankun Song, Thomas Keane, Weiping Chu, Xiaolin Zi, Omid Yazdanpanah, Arash Rezazadeh Kalebasty, Farah Rahmatpanah. Tumor-microenvironment from African-American prostate cancer exhibit methylation of multiple immune modulators [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 2148.

Abstract Reprogrammed cellular metabolism is one of the key features of cancer and tumor microenvironment. L-3-phosphoserine phosphatase (PSPH) is one of the five rate-limiting enzymes in the biosynthesis of serine from glucose that supports cell proliferation. Here, we aim to study the role of PSPH in prostate cancer (PCa) and its tumor microenvironment. We find that PSPH not only is overexpressed in prostate cancer cell lines compared to normal prostate epithelial cells (PrEC) and benign prostate epithelial cells (BPH-1), but also exhibits a higher level in patient-derived carcinoma-associated fibroblasts (CAFs) compared to the matched benign associated fibroblasts (BAFs), which are derived from fresh radical prostatectomy specimens of African American (AA) and European American (EA) men. Notably, MDAPCa2b cells derived from an AA prostate cancer patient and AA CAFs have even higher expression of PSPH protein. The mRNA levels of PSPH are also significantly elevated in prostate cancer tissues in AA men compared to EA men and predict poor survival in PCa patients. Knock-down of PSPH expression significantly inhibits the proliferation and colony formation of prostate cancer cells. Growth of xenograft tumors derived from PSPH knockdown MDAPCa2b cells has also been suppressed markedly. Gene expression profiling revealed that suppression of PSPH expression by shRNAs in LNCaP and MDAPCa2b cells is associated with the regulation of gene expression related to metabolism, immunity, extracellular matrix remodeling, and Ion channels. Similarly, analysis of publicly available PCa RNA seq databases also demonstrates that PSPH amplification or over-expression is associated with alterations of gene expression related to metabolism and immunity. Our results suggest that PSPH is upregulated in prostate cancer cells and their surrounding fibroblasts to support tumor growth via reprogramming metabolic pathways and transcriptomes. Citation Format: Liankun Song, Noriko Yokoyama, Jun Xie, Yunjie Hu, Zhenyu (Arthur) Jia, Beverly Wang, Dan Mercola, Edward Uchio, Thomas Ahlering, Michael Lilly, Xiaolin Zi. Overexpression of phosphoserine phosphatase (PSPH) in prostate cancer and in tumor microenvironment promotes tumor cell proliferation [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 773.

PurposeAnalysis of circulating tumor DNA (ctDNA) in patients with metastatic prostate cancer (mPC) provides an opportunity to identify and monitor genomic alterations during a patient’s treatment course. We evaluated whether the presence of specific gene amplifications (GAs) and plasma copy number (PCN) alterations are associated with disease features.MethodsThis is a single-institution retrospective study of patients with mPC who underwent ctDNA profiling using Guardant360® (Guardant Health Inc.). This test identifies single nucleotide variants (SNVs) and GAs of select genes by next-generation sequencing. A total of 155 men with mPC were studied. Patients were stratified by GA status. The Kaplan-Meier method and multivariate cox regression models were used to estimate overall survival (OS) or failure-free survival (FFS) from either the date of GA detection or the initiation of systemic therapy. The chi-square test was used to evaluate associations between clinical factors and GAs. ResultsThe presence of liver and/or lung metastases was associated with GAs of BRAF, CDK6, PI3KCA, and FGFR1. Survival analyses were completed on a subset of 83 patients with metastatic castration-resistant prostate cancer (mCRPC). Median OS was improved in patients with 1 GA compared to patients with ≥2 GAs, whether determined from the date of initial GA(s) detection (14.9 mo vs. 8.9 mo) or date of therapy initiation nearest to GA detection (16.7 mo vs. 9.0 mo). Patients without GAs had not reached median OS. Patients with androgen receptor (AR) GA only were also found to have better median OS compared to patients with AR GA plus at least one other additional GA (19.3 mo vs. 8.9 mo). Patients with PIK3CA GA had significantly lower median OS compared to patients with GAs that did not have a PIK3CA GA (5.9 mo vs. 16.0 mo). In patients with AR and/or MYC GA(s), median OS improved in those with reduced AR or MYC PCN during therapy compared to those without such a reduction (25.1 mo vs. 15.9 mo). ConclusionsThe association of select GAs with survival provides an additional tool for assessing mCRPC prognosis and informing management. Serial monitoring of ctDNA GAs is also useful to guide prognosis and therapeutic response.

AbstractPurposeOur preclinical studies showed that lycopene enhanced the anti‐prostate cancer efficacy of docetaxel in animal models. A phase I trial (NCT0149519) was conducted to identify an optimum dose of synthetic lycopene in combination with docetaxel (and androgen blockade [androgen deprivation therapy, ADT]), and to evaluate its effect on the safety and pharmacokinetics of docetaxel in men with metastatic prostate cancer.MethodsSubjects were treated with 21‐day cycles of 75 mg/m2 docetaxel (and ADT), plus lycopene at 30, 90 or 150 mg/day. A Bayesian model averaging continual reassessment method was used to guide dose escalation. Pharmacokinetics of docetaxel and multiple correlative studies were carried out.ResultsTwenty‐four participants were enrolled, 18 in a dose escalation cohort to define the maximum tolerated dose (MTD), and six in a pharmacokinetic cohort. Docetaxel/ADT plus 150 mg/day synthetic lycopene resulted in dose‐limiting toxicity (pulmonary embolus) in one out of 12 participants with an estimated probability of .106 and thus was chosen as the MTD. Lycopene increased the AUCinf and Cmax of plasma docetaxel by 9.5% and 15.1%, respectively. Correlative studies showed dose‐related changes in circulating endothelial cells and vascular endothelial growth factor A, and reduction in insulin‐like growth factor 1R phosphorylation, associated with lycopene therapy.ConclusionsThe combination of docetaxel/ADT and synthetic lycopene has low toxicity and favourable pharmacokinetics. The effects of lycopene on biomarkers provide additional support for the toxicity‐dependent MTD definition.Highlights The maximum tolerated dose was identified as 150 mg/day of lycopene in combination with docetaxel/ADT for the treatment of metastatic prostate cancer patients. Small increases in plasma exposure to docetaxel were observed with lycopene co‐administration. Mechanistically significant effects were seen on angiogenesis and insulin‐like growth factor 1 signalling by lycopene co‐administration with docetaxel/ADT.

Mediator kinases CDK19 and CDK8, pleiotropic regulators of transcriptional reprogramming, are differentially regulated by androgen signaling, but both kinases are upregulated in castration -resistant prostate cancer (CRPC). Genetic or pharmacological inhibition of CDK8 and CDK19 reverses the castration -resistant phenotype and restores the sensitivity of CRPC xenografts to androgen deprivation in vivo. Prolonged CDK8/19 inhibitor treatment combined with castration not only suppressed the growth of CRPC xenografts but also induced tumor regression and cures. Transcriptomic analysis revealed that Mediator kinase inhibition amplified and modulated the effects of castration on gene expression, disrupting CRPC adaptation to androgen deprivation. Mediator kinase inactivation in tumor cells also affected stromal gene expression, indicating that Mediator kinase activity in CRPC molded the tumor microenvironment. The combination of castration and Mediator kinase inhibition downregulated the MYC pathway, and Mediator kinase inhibition suppressed a MYC-driven CRPC tumor model even without castration. CDK8/19 inhibitors showed efficacy in patient -derived xenograft models of CRPC, and a gene signature of Mediator kinase activity correlated with tumor progression and overall survival in clinical samples of metastatic CRPC. These results indicate that Mediator kinases mediated androgen -independent in vivo growth of CRPC, supporting the development of CDK8/19 inhibitors for the treatment of this presently incurable disease.