Bone mimetic environments support engineering, propagation, and analysis of therapeutic response of patient-derived cells, ex vivo and in vivo

Bone metastases are the most common milestone in the lethal progression of prostate cancer and prominent in a substantial portion of renal malignancies. Interactions between cancer and bone host cells have emerged as drivers of both disease progression and therapeutic resistance. To best understand these central host-epithelial cell interactions, biologically relevant preclinical models are required. To achieve this goal, we here established and characterized tissue-engineered bone mimetic environments (BME) capable of supporting the growth of patient-derived xenograft (PDX) cells, ex vivo and in vivo. The BME consisted of a polycaprolactone (PCL) scaffold colonized by human mesenchymal stem cells (hMSCs) differentiated into osteoblasts. PDX-derived cells were isolated from bone metastatic prostate or renal tumors, engineered to express GFP or luciferase and seeded onto the BMEs. BMEs supported the growth and therapy response of PDX-derived cells, ex vivo. Additionally, BMEs survived after in vivo implantation and further sustained the growth of PDX-derived cells, their serial transplant, and their application to study the response to treatment. Taken together, this demonstrates the utility of BMEs in combination with patient-derived cells, both ex vivo and in vivo. STATEMENT OF SIGNIFICANCE: Our tissue-engineered BME supported the growth of patient-derived cells and proved useful to monitor the therapy response, both ex vivo and in vivo. This approach has the potential to enable co-clinical strategies to monitor bone metastatic tumor progression and therapy response, including identification and prioritization of new targets for patient treatment.

Integrative molecular analyses of the MD Anderson prostate cancer patient-derived xenograft (MDA PCa PDX) series

PURPOSE

Develop and deploy a robust discovery platform that encompasses heterogeneity, clinical annotation, and molecular characterization and overcomes the limited availability of prostate cancer (PCa) models. This initiative builds on the rich MD Anderson (MDA) PCa patient-derived xenograft (PDX) resource to complement existing publicly available databases by addressing gaps in clinically annotated models reflecting the heterogeneity of potentially lethal and lethal PCa.

EXPERIMENTAL DESIGN

We performed whole-genome, targeted, and RNA sequencing in representative samples of the same tumor from 44 PDXs derived from 38 patients linked to donor tumor metadata and corresponding organoids. The cohort includes models derived from different morphologic groups, disease states, and involved organ sites (including circulating tumor cells), as well as paired samples representing heterogeneity or stages before and after therapy.

RESULTS

The cohort recapitulates clinically reported alterations in PCa genes, providing a data resource for clinical and molecular interrogation of suitable experimental models. Paired samples displayed conserved molecular alteration profiles, suggesting the relevance of other regulatory mechanisms (e.g., epigenomic) influenced by the microenvironment and/or treatment. Transcriptomically, models were grouped based on morphological classification. DNA damage response-associated mechanisms emerged as differentially regulated between adenocarcinoma and neuroendocrine PCa in a cross-interrogation of PDX/patient datasets.

CONCLUSIONS

We addressed the gap in clinically relevant PCa models through comprehensive molecular characterization of MDA PCa PDXs, providing a discovery platform that integrates with patient data and benchmarked to therapeutically relevant consensus clinical groupings. This unique resource supports robust hypothesis generation and testing from basic, translational, and clinical perspectives.

Phase I Study of ORIC-101, a Glucocorticoid Receptor Antagonist, in Combination with Enzalutamide in Patients with Metastatic Castration-resistant Prostate Cancer Progressing on Enzalutamide

PURPOSE

Increased glucocorticoid receptor (GR) signaling is a proposed compensatory mechanism of resistance to androgen receptor (AR) inhibition in metastatic castration-resistant prostate cancer (mCRPC). ORIC-101 is a potent and selective orally-bioavailable GR antagonist.

PATIENTS AND METHODS

Safety, pharmacokinetic/pharmacodynamic, and antitumor activity of ORIC-101 in combination with enzalutamide were studied in patients with mCRPC progressing on enzalutamide. ORIC-101 doses ranging from 80 to 240 mg once daily were tested in combination with enzalutamide 160 mg once daily. Pharmacokinetics/pharmacodynamics was assessed after a single dose and at steady state. Disease control rate (DCR) at 12 weeks was evaluated at the recommended phase 2 dose (RP2D).

RESULTS

A total of 41 patients were enrolled. There were no dose-limiting toxicities and the RP2D was selected as 240 mg of ORIC-101 and 160 mg of enzalutamide daily. At the RP2D, the most common treatment-related adverse events were fatigue (38.7%), nausea (29.0%), decreased appetite (19.4%), and constipation (12.9%). Pharmacokinetic/pharmacodynamic data confirmed ORIC-101 achieved exposures necessary for GR target engagement. Overall, for 31 patients treated at the RP2D, there was insufficient clinical benefit based on DCR (25.8%; 80% confidence interval: 15.65-38.52) which did not meet the prespecified target rate, leading to termination of the study. Exploratory subgroup analyses based on baseline GR expression, presence of AR resistance variants, and molecular features of aggressive variant prostate cancer suggested possible benefit in patients with high GR expression and no other resistance markers, although this would require confirmation.

CONCLUSIONS

Although the combination of ORIC-101 and enzalutamide demonstrated an acceptable tolerability profile, GR target inhibition with ORIC-101 did not produce clinical benefit in men with metastatic prostate cancer resistant to enzalutamide.

Challenging the Prevailing Therapeutic Dogma for Prostate Cancer: The Case for an Overlap Syndrome

There is a need to understand what accounts for the modest impact of therapy on overall survival among men with potentially lethal prostate cancer. Given converging lines of evidence, we hypothesize that in a subset of men, prostate cancer is part of an "overlap syndrome" of age-related illnesses with shared biologic vulnerability.

Evaluation of the Aggressive-Variant Prostate Cancer Molecular Signature in Clinical Laboratory Improvement Amendments (CLIA) Environments

Aggressive-variant prostate cancers (AVPCs) are a subset of metastatic castrate-resistant prostate cancers (mCRPCs) characterized by defects in ≥ two of three of TP53, RB1, and PTEN (AVPCm), a profile linked to lineage plasticity, androgen indifference, and platinum sensitivity. Men with mCRPC undergoing biopsies for progression were assessed for AVPCm using immunohistochemistry (IHC), next-generation sequencing (NGS) of solid tumor DNA (stDNA), and NGS of circulating tumor DNA (ctDNA) assays in CLIA-certified labs. Biopsy characteristics, turnaround times, inter-reader concordance, and inter-assay concordance were assessed. AVPCm was detected in 13 (27%) patients via IHC, two (6%) based on stDNA, and seven (39%) based on ctDNA. The concordance of the IHC reads between pathologists was variable. IHC had a higher detection rate of AVPCm+ tumors with the shortest turnaround times. stDNA had challenges with copy number loss detection, limiting its detection rate. ctDNA detected the greatest proportion of AVPCm+ tumors but had a low tumor content in two thirds of patients. These data show the operational characteristics of AVPCm detection using various assays, and inform trial design using AVPCm as a criterion for patient selection or stratification.

Monitoring Glucocorticoid Receptor in Plasma-derived Extracellular Vesicles as a Marker of Resistance to Androgen Receptor Signaling Inhibition in Prostate Cancer

Disease progression following androgen ablation was shown to be associated with upregulation of the glucocorticoid receptor (GR). Longitudinal monitoring of GR expression in circulating extracellular vesicles (EV) may reflect changes in the tumor cell and facilitates detection of acquired resistance. We utilized LNCaP, LREX cells and a patient-derived xenograft, MDA PDX 322-2-6a, for in vitro and in vivo experiments. Plasma-derived EVs were isolated from patients with localized high-risk prostate cancer undergoing androgen ablation. The mRNA levels of GR in EVs and their responsive genes were detected by transcriptome analysis, qRT-PCR and the protein levels by Western blot analysis. We detected changes in GR expression at mRNA and protein levels in EVs derived from LNCaP and LREX cells in in vitro studies. In in vivo experiments, LNCaP and the PDX MDA 322-2-6a-bearing mice were treated with enzalutamide. GR levels in plasma-derived EVs were increased only in those tumors that did not respond to enzalutamide. Treatment of mice bearing enzalutamide-resistant tumors with a GR inhibitor in combination with enzalutamide led to a transient pause in tumor growth in a subset of tumors and decreased GR levels intracellular and in plasma-derived EVs. In a subgroup of patients with high-risk localized prostate cancer treated with androgen signaling inhibition, GR was found upregulated in matching tissue and plasma EVs. These analyses showed that GR levels in plasma-derived EVs may be used for monitoring the transition of GR expression allowing for early detection of resistance to androgen ablation treatment.

SIGNIFICANCE

Longitudinal monitoring of GR expression in plasma-derived EVs from patients with prostate cancer treated with androgen signaling inhibitors facilitates early detection of acquisition of resistance to androgen receptor signaling inhibition in individual patients.

Characterizing prostate cancer risk through multi-ancestry genome-wide discovery of 187 novel risk variants

The transferability and clinical value of genetic risk scores (GRSs) across populations remain limited due to an imbalance in genetic studies across ancestrally diverse populations. Here we conducted a multi-ancestry genome-wide association study of 156,319 prostate cancer cases and 788,443 controls of European, African, Asian and Hispanic men, reflecting a 57% increase in the number of non-European cases over previous prostate cancer genome-wide association studies. We identified 187 novel risk variants for prostate cancer, increasing the total number of risk variants to 451. An externally replicated multi-ancestry GRS was associated with risk that ranged from 1.8 (per standard deviation) in African ancestry men to 2.2 in European ancestry men. The GRS was associated with a greater risk of aggressive versus non-aggressive disease in men of African ancestry (P = 0.03). Our study presents novel prostate cancer susceptibility loci and a GRS with effective risk stratification across ancestry groups.

Characterization of prostate cancer adrenal metastases: dependence upon androgen receptor signaling and steroid hormones

BACKGROUND

Prostate cancer (PCa) typically spreads to the bone, and this distribution is attributed to the central role of the microenvironment in progression. However, metastasis to the adrenal glands, while not as common, does occur. The biology that accounts for adrenal metastases may be attributed to the unique local steroid metabolome and co-clinical characterization may elucidate the role steroid biosynthesis plays in PCa progression.

METHODS

Three patients with metastatic PCa who had archived tumor tissue from an adrenalectomy were retrospectively identified, and one adrenal metastasis was developed into a xenograft (MDA-PCa-250). The adrenal metastases were characterized by performing somatic DNA whole exome sequencing (WES), RNA-Seq, immunohistochemistry (IHC), and steroid metabolite quantitation. The influence of steroid metabolites on adrenal metastasis cells and tumor growth was tested in vitro and in vivo.

RESULTS

Clinically, adrenalectomy was performed during castration-resistant oligometastatic disease, and two men experienced resensitization to leuprolide. Somatic DNA WES revealed heterogeneous alterations in tumor suppressor and DNA damage repair pathway genes. Adrenal metastases had active androgen receptor (AR) signaling by IHC, and RNA-Seq supported a potential role for adrenal androgen precursor metabolism in activating the AR. Steroid quantitation suggested the adrenal androgen precursors were converted into testosterone in these metastases, and stable isotope tracing of an organoid from MDA-PCa-250 confirmed the capability of adrenal metastases to biosynthesize testosterone from adrenal precursors. In vitro testing of a cell line derived from MDA-PCa-250 showed that testosterone and cortisol stimulated tumor cell growth. In vivo experiments demonstrated that MDA-PCa-250 grew in intact mice with circulating testosterone, but not in castrated mice.

CONCLUSIONS

PCa adrenal metastases depend upon AR signaling driven by androgen precursors, androstenedione and dehydroepiandrosterone, available in the microenvironment, despite the presence of heterogeneous somatic DNA alterations. Moreover, MDA-PCa-250 provides a preclinical model that can recapitulate the unique androgen-dependence of adrenal metastases.

CLINICAL TRIAL REGISTRATION

This study does not report the clinical results of a clinical trial, but it does use samples from a completed clinical trial that is registered with clinicaltrials.gov (NCT01254864).

Cardiometabolic healthcare for men with prostate cancer: an MD Anderson Cancer Center experience

BACKGROUND

Men diagnosed with prostate cancer are at risk for competing morbidity and mortality due to cardiometabolic disease given their advanced age at diagnosis, high prevalence of pre-existing risk factors, and receipt of systemic therapy that targets the androgen receptor (AR). Expert panels have stressed the importance of cardiometabolic risk assessment in the clinic and proposed evaluating key risks using consensus paradigms. Yet, there is a gap in real-world evidence for implementation of comprehensive cardiometabolic care for men with prostate cancer.

METHODS

This is a retrospective, descriptive study of patients with prostate cancer who were referred and evaluated in the Healthy Heart Program at MD Anderson Cancer Center, which was established to mitigate cardiometabolic risks in men with prostate cancer. Patients were seen by a cardiologist and exercise physiologist to evaluate and manage cardiometabolic risk factors, including blood pressure, cholesterol, blood glucose, tobacco use, and coronary artery disease, concurrent with management of their cancer by a medical oncologist.

RESULTS

From December 2018 through October 2021, the Healthy Heart Program enrolled 55 men with prostate cancer, out of which 35 had biochemical, locoregional recurrence or distant metastases, while all received at least a single dose of a luteinizing hormone-releasing hormone (LHRH) analog. Ninety-three percent of men were overweight or obese, and 51% had an intermediate or high risk of atherosclerotic cardiovascular disease at 10 years based on the pooled cohort equation. Most men had an overlap of two or more cardiometabolic diseases (84%), and 25% had an overlap of at least 4 cardiometabolic diseases. Although uncontrolled hypertension and hyperlipidemia were common among the cohort (45% and 26%, respectively), only 29% of men followed up with the clinic.

CONCLUSIONS

Men with prostate cancer have a high burden of concurrent cardiometabolic risk factors. At a tertiary cancer center, the Healthy Heart Program was implemented to address this need, yet the utility of the program was limited by poor follow-up possibly due to outside cardiometabolic care and inconvenient appointment logistics, a lack of cardiometabolic labs at the time of visits, and telemedicine visits.

A GATA2-CDC6 axis modulates androgen receptor blockade-induced senescence in prostate cancer

BACKGROUND

Prostate cancer is a major cause of cancer morbidity and mortality in men worldwide. Androgen deprivation therapy (ADT) has proven effective in early-stage androgen-sensitive disease, but prostate cancer gradually develops into an androgen-resistant metastatic state in the vast majority of patients. According to our oncogene-induced model for cancer development, senescence is a major tumor progression barrier. However, whether senescence is implicated in the progression of early-stage androgen-sensitive to highly aggressive castration-resistant prostate cancer (CRPC) remains poorly addressed.

METHODS

Androgen-dependent (LNCaP) and -independent (C4-2B and PC-3) cells were treated or not with enzalutamide, an Androgen Receptor (AR) inhibitor. RNA sequencing and pathway analyses were carried out in LNCaP cells to identify potential senescence regulators upon treatment. Assessment of the invasive potential of cells and senescence status following enzalutamide treatment and/or RNAi-mediated silencing of selected targets was performed in all cell lines, complemented by bioinformatics analyses on a wide range of in vitro and in vivo datasets. Key observations were validated in LNCaP and C4-2B mouse xenografts. Senescence induction was assessed by state-of-the-art GL13 staining by immunocytochemistry and confocal microscopy.

RESULTS

We demonstrate that enzalutamide treatment induces senescence in androgen-sensitive cells via reduction of the replication licensing factor CDC6. Mechanistically, we show that CDC6 downregulation is mediated through endogenous activation of the GATA2 transcription factor functioning as a CDC6 repressor. Intriguingly, GATA2 levels decrease in enzalutamide-resistant cells, leading to CDC6 stabilization accompanied by activation of Epithelial-To-Mesenchymal Transition (EMT) markers and absence of senescence. We show that CDC6 loss is sufficient to reverse oncogenic features and induce senescence regardless of treatment responsiveness, thereby identifying CDC6 as a critical determinant of prostate cancer progression.

CONCLUSIONS

We identify a key GATA2-CDC6 signaling axis which is reciprocally regulated in enzalutamide-sensitive and -resistant prostate cancer environments. Upon acquired resistance, GATA2 repression leads to CDC6 stabilization, with detrimental effects in disease progression through exacerbation of EMT and abrogation of senescence. However, bypassing the GATA2-CDC6 axis by direct inhibition of CDC6 reverses oncogenic features and establishes senescence, thereby offering a therapeutic window even after acquiring resistance to therapy.

Evaluating approaches for constructing polygenic risk scores for prostate cancer in men of African and European ancestry

Genome-wide polygenic risk scores (GW-PRSs) have been reported to have better predictive ability than PRSs based on genome-wide significance thresholds across numerous traits. We compared the predictive ability of several GW-PRS approaches to a recently developed PRS of 269 established prostate cancer-risk variants from multi-ancestry GWASs and fine-mapping studies (PRS269). GW-PRS models were trained with a large and diverse prostate cancer GWAS of 107,247 cases and 127,006 controls that we previously used to develop the multi-ancestry PRS269. Resulting models were independently tested in 1,586 cases and 1,047 controls of African ancestry from the California Uganda Study and 8,046 cases and 191,825 controls of European ancestry from the UK Biobank and further validated in 13,643 cases and 210,214 controls of European ancestry and 6,353 cases and 53,362 controls of African ancestry from the Million Veteran Program. In the testing data, the best performing GW-PRS approach had AUCs of 0.656 (95% CI = 0.635-0.677) in African and 0.844 (95% CI = 0.840-0.848) in European ancestry men and corresponding prostate cancer ORs of 1.83 (95% CI = 1.67-2.00) and 2.19 (95% CI = 2.14-2.25), respectively, for each SD unit increase in the GW-PRS. Compared to the GW-PRS, in African and European ancestry men, the PRS269 had larger or similar AUCs (AUC = 0.679, 95% CI = 0.659-0.700 and AUC = 0.845, 95% CI = 0.841-0.849, respectively) and comparable prostate cancer ORs (OR = 2.05, 95% CI = 1.87-2.26 and OR = 2.21, 95% CI = 2.16-2.26, respectively). Findings were similar in the validation studies. This investigation suggests that current GW-PRS approaches may not improve the ability to predict prostate cancer risk compared to the PRS269 developed from multi-ancestry GWASs and fine-mapping.

Evaluating Approaches for Constructing Polygenic Risk Scores for Prostate Cancer in Men of African and European Ancestry

Genome-wide polygenic risk scores (GW-PRS) have been reported to have better predictive ability than PRS based on genome-wide significance thresholds across numerous traits. We compared the predictive ability of several GW-PRS approaches to a recently developed PRS of 269 established prostate cancer risk variants from multi-ancestry GWAS and fine-mapping studies (PRS 269 ). GW-PRS models were trained using a large and diverse prostate cancer GWAS of 107,247 cases and 127,006 controls used to develop the multi-ancestry PRS 269 . Resulting models were independently tested in 1,586 cases and 1,047 controls of African ancestry from the California/Uganda Study and 8,046 cases and 191,825 controls of European ancestry from the UK Biobank and further validated in 13,643 cases and 210,214 controls of European ancestry and 6,353 cases and 53,362 controls of African ancestry from the Million Veteran Program. In the testing data, the best performing GW-PRS approach had AUCs of 0.656 (95% CI=0.635-0.677) in African and 0.844 (95% CI=0.840-0.848) in European ancestry men and corresponding prostate cancer OR of 1.83 (95% CI=1.67-2.00) and 2.19 (95% CI=2.14-2.25), respectively, for each SD unit increase in the GW-PRS. However, compared to the GW-PRS, in African and European ancestry men, the PRS 269 had larger or similar AUCs (AUC=0.679, 95% CI=0.659-0.700 and AUC=0.845, 95% CI=0.841-0.849, respectively) and comparable prostate cancer OR (OR=2.05, 95% CI=1.87-2.26 and OR=2.21, 95% CI=2.16-2.26, respectively). Findings were similar in the validation data. This investigation suggests that current GW-PRS approaches may not improve the ability to predict prostate cancer risk compared to the multi-ancestry PRS 269 constructed with fine-mapping.

Transcriptomic analysis of plasma exosomes provides molecular information of response to cabazitaxel treatment in men with metastatic castration-resistant prostate cancer

BACKGROUND

Prostate cancer is the second most common cancer type and the second most common cancer-related cause of death in men. Cabazitaxel, a next-generation taxane, shows favorable toxicity profile and is effective in docetaxel-resistant tumors. Despite initial responses, in most cases, prostate cancer patients acquire resistance to cabazitaxel. There is a need to identify molecular markers that can monitor and predict treatment response.

METHODS

We performed transcriptional exosome profiling (Human Transcriptome Array-HTA 2.0) from the plasma of 19 patients with castration-resistant prostate cancer at baseline and in patients after one cycle of cabazitaxel (C1). The patients were stratified in two groups (responders and nonresponders) according to their clinical response to cabazitaxel. Gene set enrichment analysis and ingenuity pathway analysis platforms were used for gene and pathway analysis.

RESULTS

We detected molecular differences in the exosomes from two groups of patients (nonresponders vs. responders) at baseline in pathways related to prostate cancer, oncogenic signaling, cytoskeleton, and immune system. In nonresponders, we found enrichment of cytoskeleton related gene (Stathmin-1 and ITSN1) that have been associated with resistance to cabazitaxel. Monitoring of exosomal transcripts after the first cycle of treatment revealed changes in pathways associated with response to treatment.

CONCLUSIONS

Sequential transcriptional profiling of plasma-derived exosomes reveals differential expression of genes that may reflect resistance to cabazitaxel treatment and therapy response.

Abstract 4760: KDM4A promotes NEPC progression through regulation of MYC expression

Despite advancements in treatment, prostate cancer (PCa) remains the second leading cause of death among men. Neuroendocrine prostate cancer (NEPC) represents one of the most lethal forms of PCa and lacks life-prolonging treatment. Here we identified histone lysine demethylase KDM4A as a driver in NEPC progression and an effective therapeutic target. KDM4A mRNA and protein are overexpressed in human and mouse NEPC compared to adenocarcinoma. Knockdown or knockout of KDM4A in NEPC cell lines suppressed cancer cell growth in vitro and in vivo. Importantly, the inactivation of Kdm4a in a genetically engineered mouse model of prostate cancer reduces tumor burden, reduces the incidence of NEPC, and prolongs overall survival. Mechanistically, KDM4A directly regulates the transcription of MYC, which is hyper-activated in human and mouse NEPC. Furthermore, a potent pan-KDM4 inhibitor QC6352 significantly reduces NEPC cell growth in vitro and in vivo. Taken together, we demonstrate that KDM4A promotes NEPC progression through regulation of MYC expression and targeting KDM4A can be an effective therapeutic strategy for NEPC.

Citation Format: Celia Sze Ling Mak, Ming Zhu, Xin Liang, Feng Wang, Anh G. Hoang, Xinzhi Song, Peter Shepherd, Derek Liang, Jessica Suh, Jiwon Park, Miao Zhang, Eric Metzger, Roland Schule, Abhinav K. Jain, Ellen Karasik, Barbara A. Foster, Min Gyu Lee, Paul Corn, Christopher J. Logothetis, Ana Aparicio, Nora Navone, Patricia Troncoso, Jianhua Zhang, Sue-Hwa Lin, Guocan Wang. KDM4A promotes NEPC progression through regulation of MYC expression. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4760.

Integrative Clinical and Genomic Characterization of MTAP-deficient Metastatic Urothelial Cancer

Deficiency of MTAP (MTAPdef) mainly occurs because of homozygous loss of chromosome 9p21, which is the most common copy-number loss in metastatic urothelial cancer (mUC). We characterized the clinical and genomic features of MTAPdef mUC in 193 patients treated at MD Anderson Cancer Center (MDACC) and 298 patients from the phase 2 IMvigor210 trial, which investigated atezolizumab in cisplatin-ineligible and platinum-refractory disease. In the MDACC cohort, visceral metastases were significantly more common for MTAPdef (n = 48) than for MTAP-proficient (MTAPprof; n = 145) patients (75% vs 55.2%; p = 0.02). MTAPdef was associated with poor prognosis (median overall survival [mOS] 12.3 vs 20.2 mo; p = 0.007) with an adjusted hazard ratio of 1.93 (95% confidence interval 1.35-2.98). Similarly, IMvigor210 patients with MTAPlo (n = 29) had a higher incidence of visceral metastases than those with MTAPhi tumors (n = 269; 86.2% vs 72.5%; p = 0.021) and worse prognosis (mOS 8.0 vs 11.3 mo; p = 0.042). Hyperplasia-associated genes were more frequently mutated in MTAPdef tumors (FGFR3: 31% vs 8%; PI3KCA: 31% vs 19%), while alterations in dysplasia-associated genes were less common in MTAPdef tumors (TP53: 41% vs 67%; RB1: 0% vs 16%). Our findings support a distinct biology in MTAPdef mUC that is associated with early visceral disease and worse prognosis. PATIENT SUMMARY: We investigated the outcomes for patients with the most common gene loss (MTAP gene) in metastatic cancer of the urinary tract. We found that this loss correlates with worse prognosis and a higher risk of metastasis in internal organs. There seems to be distinct tumor biology for urinary tract cancer with MTAP gene loss and this could be a potential target for treatment.

Management of Patients with Advanced Prostate Cancer. Part I: Intermediate-/High-risk and Locally Advanced Disease, Biochemical Relapse, and Side Effects of Hormonal Treatment: Report of the Advanced Prostate Cancer Consensus Conference 2022

BACKGROUND

Innovations in imaging and molecular characterisation and the evolution of new therapies have improved outcomes in advanced prostate cancer. Nonetheless, we continue to lack high-level evidence on a variety of clinical topics that greatly impact daily practice. To supplement evidence-based guidelines, the 2022 Advanced Prostate Cancer Consensus Conference (APCCC 2022) surveyed experts about key dilemmas in clinical management.

OBJECTIVE

To present consensus voting results for select questions from APCCC 2022.

DESIGN, SETTING, AND PARTICIPANTS

Before the conference, a panel of 117 international prostate cancer experts used a modified Delphi process to develop 198 multiple-choice consensus questions on (1) intermediate- and high-risk and locally advanced prostate cancer, (2) biochemical recurrence after local treatment, (3) side effects from hormonal therapies, (4) metastatic hormone-sensitive prostate cancer, (5) nonmetastatic castration-resistant prostate cancer, (6) metastatic castration-resistant prostate cancer, and (7) oligometastatic and oligoprogressive prostate cancer. Before the conference, these questions were administered via a web-based survey to the 105 physician panel members ("panellists") who directly engage in prostate cancer treatment decision-making. Herein, we present results for the 82 questions on topics 1-3.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Consensus was defined as ≥75% agreement, with strong consensus defined as ≥90% agreement.

RESULTS AND LIMITATIONS

The voting results reveal varying degrees of consensus, as is discussed in this article and shown in the detailed results in the Supplementary material. The findings reflect the opinions of an international panel of experts and did not incorporate a formal literature review and meta-analysis.

CONCLUSIONS

These voting results by a panel of international experts in advanced prostate cancer can help physicians and patients navigate controversial areas of clinical management for which high-level evidence is scant or conflicting. The findings can also help funders and policymakers prioritise areas for future research. Diagnostic and treatment decisions should always be individualised based on patient and cancer characteristics (disease extent and location, treatment history, comorbidities, and patient preferences) and should incorporate current and emerging clinical evidence, therapeutic guidelines, and logistic and economic factors. Enrolment in clinical trials is always strongly encouraged. Importantly, APCCC 2022 once again identified important gaps (areas of nonconsensus) that merit evaluation in specifically designed trials.

PATIENT SUMMARY

The Advanced Prostate Cancer Consensus Conference (APCCC) provides a forum to discuss and debate current diagnostic and treatment options for patients with advanced prostate cancer. The conference aims to share the knowledge of international experts in prostate cancer with health care providers and patients worldwide. At each APCCC, a panel of physician experts vote in response to multiple-choice questions about their clinical opinions and approaches to managing advanced prostate cancer. This report presents voting results for the subset of questions pertaining to intermediate- and high-risk and locally advanced prostate cancer, biochemical relapse after definitive treatment, advanced (next-generation) imaging, and management of side effects caused by hormonal therapies. The results provide a practical guide to help clinicians and patients discuss treatment options as part of shared multidisciplinary decision-making. The findings may be especially useful when there is little or no high-level evidence to guide treatment decisions.

Immune and pathologic responses in patients with localized prostate cancer who received daratumumab (anti-CD38) or edicotinib (CSF-1R inhibitor)

BACKGROUND

The prostate tumor microenvironment (TME) is immunosuppressive, with few effector T cells and enrichment of inhibitory immune populations, leading to limited responses to treatments such as immune checkpoint therapies (ICTs). The immune composition of the prostate TME differs across soft tissue and bone, the most common site of treatment-refractory metastasis. Understanding immunosuppressive mechanisms specific to prostate TMEs will enable rational immunotherapy strategies to generate effective antitumor immune responses. Daratumumab (anti-CD38 antibody) and edicotinib (colony-stimulating factor-1 receptor (CSF-1R) inhibitor) may alter the balance within the prostate TME to promote antitumor immune responses.

HYPOTHESIS

Daratumumab or edicotinib will be safe and will alter the immune TME, leading to antitumor responses in localized prostate cancer.

PATIENTS AND METHODS

In this presurgical study, patients with localized prostate cancer received 4 weekly doses of daratumumab or 4 weeks of daily edicotinib prior to radical prostatectomy (RP). Treated and untreated control (Gleason score ≥8 in prostate biopsy) prostatectomy specimens and patient-matched pre- and post-treatment peripheral blood mononuclear cells (PBMCs) and bone marrow samples were evaluated. The primary endpoint was incidence of adverse events (AEs). The secondary endpoint was pathologic complete remission (pCR) rate.

RESULTS

Twenty-five patients were treated (daratumumab, n=15; edicotinib, n=10). All patients underwent RP without delays. Grade 3 treatment-related AEs with daratumumab occurred in 3 patients (12%), and no ≥grade 3 treatment-related AEs occurred with edicotinib. No changes in serum prostate-specific antigen (PSA) levels or pCRs were observed. Daratumumab led to a decreased frequency of CD38+ T cells, natural killer cells, and myeloid cells in prostate tumors, bone marrow, and PBMCs. There were no consistent changes in CSF-1R+ immune cells in prostate, bone marrow, or PBMCs with edicotinib. Neither treatment induced T cell infiltration into the prostate TME.

CONCLUSIONS

Daratumumab and edicotinib treatment was safe and well-tolerated in patients with localized prostate cancer but did not induce pCRs. Decreases in CD38+ immune cells were observed in prostate tumors, bone marrow, and PBMCs with daratumumab, but changes in CSF-1R+ immune cells were not consistently observed with edicotinib. Neither myeloid-targeted agent alone was sufficient to generate antitumor responses in prostate cancer; thus, combinations with agents to induce T cell infiltration (eg, ICTs) will be needed to overcome the immunosuppressive prostate TME.

Endothelial-to-osteoblast transition in normal mouse bone development

Metastatic prostate cancer (PCa) in bone induces bone-forming lesions. We have previously shown that PCa-induced bone originates from endothelial cells (ECs) that have undergone EC-to-osteoblast (OSB) transition. Here, we investigated whether EC-to-OSB transition also occurs during normal bone formation. We developed an EC and OSB dual-color reporter mouse (DRM) model that marks EC-OSB hybrid cells with red and green fluorescent proteins. We observed EC-to-OSB transition (RFP and GFP co-expression) in both endochondral and intramembranous bone formation during embryonic development and in adults. Co-expression was confirmed in cells isolated from DRM. Bone marrow- and lung-derived ECs underwent transition to OSBs and mineralization in osteogenic medium. RNA-sequencing revealed GATA family transcription factors were upregulated in EC-OSB hybrid cells and knockdown of GATA3 inhibited BMP4-induced mineralization. Our findings support that EC-to-OSB transition occurs during normal bone development and suggest a new paradigm regarding the endothelial origin of OSBs.

Subtype and Site Specific-Induced Metabolic Vulnerabilities in Prostate Cancer

Aberrant metabolic functions play a crucial role in prostate cancer progression and lethality. Currently, limited knowledge is available on subtype-specific metabolic features and their implications for treatment. We therefore investigated the metabolic determinants of the two major subtypes of castration-resistant prostate cancer [androgen receptor-expressing prostate cancer (ARPC) and aggressive variant prostate cancer (AVPC)]. Transcriptomic analyses revealed enrichment of gene sets involved in oxidative phosphorylation (OXPHOS) in ARPC tumor samples compared with AVPC. Unbiased screening of metabolic signaling pathways in patient-derived xenograft models by proteomic analyses further supported an enrichment of OXPHOS in ARPC compared with AVPC, and a skewing toward glycolysis by AVPC. In vitro, ARPC C4-2B cells depended on aerobic respiration, while AVPC PC3 cells relied more heavily on glycolysis, as further confirmed by pharmacologic interference using IACS-10759, a clinical-grade inhibitor of OXPHOS. In vivo studies confirmed IACS-10759's inhibitory effects in subcutaneous and bone-localized C4-2B tumors, and no effect in subcutaneous PC3 tumors. Unexpectedly, IACS-10759 inhibited PC3 tumor growth in bone, indicating microenvironment-induced metabolic reprogramming. These results suggest that castration-resistant ARPC and AVPC exhibit different metabolic dependencies, which can further undergo metabolic reprogramming in bone.

IMPLICATIONS

These vulnerabilities may be exploited with mechanistically novel treatments, such as those targeting OXPHOS alone or possibly in combination with existing therapies. In addition, our findings underscore the impact of the tumor microenvironment in reprogramming prostate cancer metabolism.

Retinoic Acid Receptor Activation Reduces Metastatic Prostate Cancer Bone Lesions by Blocking the Endothelial-to-Osteoblast Transition

Metastatic prostate cancer in the bone induces bone-forming lesions that contribute to progression and therapy resistance. Prostate cancer-induced bone formation originates from endothelial cells (EC) that have undergone endothelial-to-osteoblast (EC-to-OSB) transition in response to tumor-secreted BMP4. Current strategies targeting prostate cancer-induced bone formation are lacking. Here, we show that activation of retinoic acid receptor (RAR) inhibits EC-to-OSB transition and reduces prostate cancer-induced bone formation. Treatment with palovarotene, an RARγ agonist being tested for heterotopic ossification in fibrodysplasia ossificans progressiva, inhibited EC-to-OSB transition and osteoblast mineralization in vitro and decreased tumor-induced bone formation and tumor growth in several osteogenic prostate cancer models, and similar effects were observed with the pan-RAR agonist all-trans-retinoic acid (ATRA). Knockdown of RARα, β, or γ isoforms in ECs blocked BMP4-induced EC-to-OSB transition and osteoblast mineralization, indicating a role for all three isoforms in prostate cancer-induced bone formation. Furthermore, treatment with palovarotene or ATRA reduced plasma Tenascin C, a factor secreted from EC-OSB cells, which may be used to monitor treatment response. Mechanistically, BMP4-activated pSmad1 formed a complex with RAR in the nucleus of ECs to activate EC-to-OSB transition. RAR activation by palovarotene or ATRA caused pSmad1 degradation by recruiting the E3-ubiquitin ligase Smad ubiquitination regulatory factor1 (Smurf1) to the nuclear pSmad1/RARγ complex, thus blocking EC-to-OSB transition. Collectively, these findings suggest that palovarotene can be repurposed to target prostate cancer-induced bone formation to improve clinical outcomes for patients with bone metastasis.

SIGNIFICANCE

This study provides mechanistic insights into how RAR agonists suppress prostate cancer-induced bone formation and offers a rationale for developing RAR agonists for prostate cancer bone metastasis therapy. See related commentary by Bhowmick and Bhowmick, p. 2975.

Enhancing 223Ra Treatment Efficacy by Anti-1 Integrin Targeting

223Ra is an α-emitter approved for the treatment of bone metastatic prostate cancer (PCa), which exerts direct cytotoxicity toward PCa cells near the bone interface, whereas cells positioned in the core respond poorly because of short α-particle penetrance. β1 integrin (β1I) interference has been shown to increase radiosensitivity and significantly enhance external-beam radiation efficiency. We hypothesized that targeting β1I would improve 223Ra outcome. Methods: We tested the effect of combining 223Ra and anti-β1I antibody treatment in PC3 and C4-2B PCa cell models expressing high and low β1I levels, respectively. In vivo tumor growth was evaluated through bioluminescence. Cellular and molecular determinants of response were analyzed by ex vivo 3-dimensional imaging of bone lesions and by proteomic analysis and were further confirmed by computational modeling and in vitro functional analysis in tissue-engineered bone mimetic systems. Results: Interference with β1I combined with 223Ra reduced PC3 cell growth in bone and significantly improved overall mouse survival, whereas no change was achieved in C4-2B tumors. Anti-β1I treatment decreased the PC3 tumor cell mitosis index and spatially expanded 223Ra lethal effects 2-fold, in vivo and in silico. Regression was paralleled by decreased expression of radioresistance mediators. Conclusion: Targeting β1I significantly improves 223Ra outcome and points toward combinatorial application in PCa tumors with high β1I expression.

Abstract 3791: Investigating longitudinal therapeutic resistance in serially treated metastatic castration resistant prostate cancer by liquid biopsy genome sequencing

Prostate cancer is the most commonly diagnosed cancer among men and a major cause of cancer-related deaths in the modern world. Metastatic castration-resistant prostate cancer (mCRPC) is the most lethal form and has complex and heterogeneous genomic patterns. Despite the recent development of life-prolonging therapies, mCRPC remains incurable since most patients develop resistance over time. A better understanding of the evolution of resistance to therapy in mCRPC is urgently needed. A major logistical challenge is that collecting serial tissue biopsies from the prostate and metastatic sites such as bone is not feasible. To overcome this issue, we developed a minimally invasive liquid biopsy approach to study the genomic basis of resistance through circulating tumor DNA (ctDNA) from longitudinally collected plasma samples. To best account for interpatient tumor heterogeneity and treatment history, we selected 60 mCRPC patients who were serially treated with life-prolonging second generation androgen signaling inhibitors (abiraterone, enzalutamide, or the combination) and taxane-based chemotherapy, and prospectively collected longitudinal blood samples (2 to 10 per patient). ctDNA was isolated from each blood plasma sample for sparse whole-genome sequencing and exome sequencing at 200x coverage depth. Somatic copy number alterations (CNA) and exome mutations were profiled and the resulting data was used to reconstruct the clonal substructure and infer clonal evolutionary dynamics across the treatment timepoints. The mutation signatures and the CNA signatures were also characterized. One of the CNA signatures identified the patients who carry CDK12 mutations through genome-wide focal tandem duplications in ctDNA. The subclones resistant to second-generation androgen signaling inhibitors and taxane-based chemotherapy were also identified, along with their associated genomic aberrations affecting AR, RB1, and PTEN. Furthermore, by analyzing the evolutionary dynamics patterns, we identified three distinct genomic responses to therapy: intrinsic resistance, clonal progression, and clonal responders, which correlated with overall survival outcomes. In summary, our data show that clonal evolutionary dynamics in mCRPC can be tracked over time and in response to treatment with minimally invasive liquid biopsy methods. Our results provide insights into the genomic evolution of life-prolonging therapy resistance in mCRPC and identified candidate resistance biomarkers for subsequent validation.

Citation Format: Yuehui Zhao, Naveen Ramesh, Emi Sei, Min Hu, Shanshan Bai, Patricia Troncoso, Paul Corn, Ana Aparicio, Christopher J. Logothetis, Nicholas E. Navin, Amado J. Zurita. Investigating longitudinal therapeutic resistance in serially treated metastatic castration resistant prostate cancer by liquid biopsy genome sequencing [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3791.

MTAP deficiency creates an exploitable target for antifolate therapy in 9p21-loss cancers

Methylthioadenosine phosphorylase, an essential enzyme for the adenine salvage pathway, is often deficient (MTAPdef) in tumors with 9p21 loss and hypothetically renders tumors susceptible to synthetic lethality by antifolates targeting de novo purine synthesis. Here we report our single arm phase II trial (NCT02693717) that assesses pemetrexed in MTAPdef urothelial carcinoma (UC) with the primary endpoint of overall response rate (ORR). Three of 7 enrolled MTAPdef patients show response to pemetrexed (ORR 43%). Furthermore, a historic cohort shows 4 of 4 MTAPdef patients respond to pemetrexed as compared to 1 of 10 MTAP-proficient patients. In vitro and in vivo preclinical data using UC cell lines demonstrate increased sensitivity to pemetrexed by inducing DNA damage, and distorting nucleotide pools. In addition, MTAP-knockdown increases sensitivity to pemetrexed. Furthermore, in a lung adenocarcinoma retrospective cohort (N = 72) from the published BATTLE2 clinical trial (NCT01248247), MTAPdef associates with an improved response rate to pemetrexed. Our data demonstrate a synthetic lethal interaction between MTAPdef and de novo purine inhibition, which represents a promising therapeutic strategy for larger prospective trials.

Prostate cancer risk stratification improvement across multiple ancestries with new polygenic hazard score

BACKGROUND

Prostate cancer risk stratification using single-nucleotide polymorphisms (SNPs) demonstrates considerable promise in men of European, Asian, and African genetic ancestries, but there is still need for increased accuracy. We evaluated whether including additional SNPs in a prostate cancer polygenic hazard score (PHS) would improve associations with clinically significant prostate cancer in multi-ancestry datasets.

METHODS

In total, 299 SNPs previously associated with prostate cancer were evaluated for inclusion in a new PHS, using a LASSO-regularized Cox proportional hazards model in a training dataset of 72,181 men from the PRACTICAL Consortium. The PHS model was evaluated in four testing datasets: African ancestry, Asian ancestry, and two of European Ancestry-the Cohort of Swedish Men (COSM) and the ProtecT study. Hazard ratios (HRs) were estimated to compare men with high versus low PHS for association with clinically significant, with any, and with fatal prostate cancer. The impact of genetic risk stratification on the positive predictive value (PPV) of PSA testing for clinically significant prostate cancer was also measured.

RESULTS

The final model (PHS290) had 290 SNPs with non-zero coefficients. Comparing, for example, the highest and lowest quintiles of PHS290, the hazard ratios (HRs) for clinically significant prostate cancer were 13.73 [95% CI: 12.43-15.16] in ProtecT, 7.07 [6.58-7.60] in African ancestry, 10.31 [9.58-11.11] in Asian ancestry, and 11.18 [10.34-12.09] in COSM. Similar results were seen for association with any and fatal prostate cancer. Without PHS stratification, the PPV of PSA testing for clinically significant prostate cancer in ProtecT was 0.12 (0.11-0.14). For the top 20% and top 5% of PHS290, the PPV of PSA testing was 0.19 (0.15-0.22) and 0.26 (0.19-0.33), respectively.

CONCLUSIONS

We demonstrate better genetic risk stratification for clinically significant prostate cancer than prior versions of PHS in multi-ancestry datasets. This is promising for implementing precision-medicine approaches to prostate cancer screening decisions in diverse populations.

Prostate tumor-induced stromal reprogramming generates Tenascin C that promotes prostate cancer metastasis through YAP/TAZ inhibition

Metastatic prostate cancer (PCa) in bone induces bone-forming lesions that enhance PCa progression. How tumor-induced bone formation enhances PCa progression is not known. We have previously shown that PCa-induced bone originates from endothelial cells (ECs) that have undergone endothelial-to-osteoblast (EC-to-OSB) transition by tumor-secreted bone morphogenetic protein 4 (BMP4). Here, we show that EC-to-OSB transition leads to changes in the tumor microenvironment that increases the metastatic potential of PCa cells. We found that conditioned medium (CM) from EC-OSB hybrid cells increases the migration, invasion, and survival of PC3-mm2 and C4-2B4 PCa cells. Quantitative mass spectrometry (Isobaric Tags for Relative and Absolute Quantitation) identified Tenascin C (TNC) as one of the major proteins secreted from EC-OSB hybrid cells. TNC expression in tumor-induced OSBs was confirmed by immunohistochemistry of MDA PCa-118b xenograft and human bone metastasis specimens. Mechanistically, BMP4 increases TNC expression in EC-OSB cells through the Smad1-Notch/Hey1 pathway. How TNC promotes PCa metastasis was next interrogated by in vitro and in vivo studies. In vitro studies showed that a TNC-neutralizing antibody inhibits EC-OSB-CM-mediated PCa cell migration and survival. TNC knockdown decreased, while the addition of recombinant TNC or TNC overexpression increased migration and anchorage-independent growth of PC3 or C4-2b cells. When injected orthotopically, PC3-mm2-shTNC clones decreased metastasis to bone, while C4-2b-TNC-overexpressing cells increased metastasis to lymph nodes. TNC enhances PCa cell migration through α5β1 integrin-mediated YAP/TAZ inhibition. These studies elucidate that tumor-induced stromal reprogramming generates TNC that enhances PCa metastasis and suggest that TNC may be a target for PCa therapy.

Genetic Factors Associated with Prostate Cancer Conversion from Active Surveillance to Treatment

Men diagnosed with low-risk prostate cancer (PC) are increasingly electing active surveillance (AS) as their initial management strategy. While this may reduce the side effects of treatment for prostate cancer, many men on AS eventually convert to active treatment. PC is one of the most heritable cancers, and genetic factors that predispose to aggressive tumors may help distinguish men who are more likely to discontinue AS. To investigate this, we undertook a multi-institutional genome-wide association study (GWAS) of 5,222 PC patients and 1,139 other patients from replication cohorts, all of whom initially elected AS and were followed over time for the potential outcome of conversion from AS to active treatment. In the GWAS we detected 18 variants associated with conversion, 15 of which were not previously associated with PC risk. With a transcriptome-wide association study (TWAS), we found two genes associated with conversion (MAST3, p = 6.9×10-7 and GAB2, p = 2.0×10-6). Moreover, increasing values of a previously validated 269-variant genetic risk score (GRS) for PC was positively associated with conversion (e.g., comparing the highest to the two middle deciles gave a hazard ratio [HR] = 1.13; 95% Confidence Interval [CI]= 0.94-1.36); whereas, decreasing values of a 36-variant GRS for prostate-specific antigen (PSA) levels were positively associated with conversion (e.g., comparing the lowest to the two middle deciles gave a HR = 1.25; 95% CI, 1.04-1.50). These results suggest that germline genetics may help inform and individualize the decision of AS-or the intensity of monitoring on AS-versus treatment for the initial management of patients with low-risk PC.

Combined CTLA-4 and PD-L1 blockade in patients with chemotherapy-naïve metastatic castration-resistant prostate cancer is associated with increased myeloid and neutrophil immune subsets in the bone microenvironment

BACKGROUND

Immune checkpoint therapy (ICT) has low response rates in patients with metastatic castration-resistant prostate cancer (mCRPC), in part due to few T cells in the tumor microenvironment (TME). Anti-cytotoxic T lymphocyte-associated protein 4 (CTLA-4) promotes intratumoral T cell infiltration but induces upregulation of PD-1 and programmed death ligand-1 (PD-L1) within the prostate TME. Combined anti-CTLA-4 plus anti-PD-1 can partly overcome this adaptive resistance and was recently shown to augment responses in patients with mCRPC with measurable disease. Although bone is the most common site of metastasis in prostate cancer, patients with bone-predominant disease are frequently excluded from trials because they lack measurable disease, which limits assessment of disease progression and tissue sampling. We therefore designed this study to investigate combined ICT in mCRPC to bone.

HYPOTHESIS

Combined anti-CTLA-4 (tremelimumab) plus anti-PD-L1 (durvalumab) is safe and well tolerated in patients with chemotherapy-naïve mCRPC to bone.

PATIENTS AND METHODS

In this single-arm pilot study, men with chemotherapy-naïve mCRPC to bone received tremelimumab (75 mg intravenous) plus durvalumab (1500 mg intravenous) every 4 weeks (up to four doses), followed by durvalumab (1500 mg intravenous) maintenance every 4 weeks (up to nine doses). The primary endpoint was incidence of adverse events. Secondary endpoints included serum prostate-specific antigen (PSA), progression-free survival (PFS), radiographic PFS (rPFS), and maximal PSA decline.

RESULTS

Twenty-six patients were treated between August 8, 2017 and March 28, 2019. Grade ≥3 treatment-related adverse events (TRAEs) occurred in 11 patients (42%), with no grade 4 or 5 events. TRAEs leading to discontinuation occurred in three patients (12%). PSA decline ≥50% occurred in three patients (12%). Six patients (24%) achieved stable disease for >6 months. At a median follow-up of 43.6 months, median rPFS was 3.7 months (95% CI: 1.9 to 5.7), and median overall survival was 28.1 months (95% CI: 14.5 to 37.3). Post-treatment evaluation of the bone microenvironment revealed transcriptional upregulation in myeloid and neutrophil immune subset signatures and increased expression of inhibitory immune checkpoints.

CONCLUSIONS

Tremelimumab plus durvalumab was safe and well tolerated in patients with chemotherapy-naïve mCRPC to bone, with potential activity in a small number of patients as measured by rPFS. Combination of CTLA-4 and PD-L1 blockade with therapies targeting the myeloid compartment or other inhibitory immune receptors may be necessary to overcome mechanisms of resistance within prostate bone microenvironment.

TRIAL REGISTRATION NUMBER

NCT03204812.

Measuring the Metabolic Evolution of Glioblastoma throughout Tumor Development, Regression, and Recurrence with Hyperpolarized Magnetic Resonance

Rapid diagnosis and therapeutic monitoring of aggressive diseases such as glioblastoma can improve patient survival by providing physicians the time to optimally deliver treatment. This research tested whether metabolic imaging with hyperpolarized MRI could detect changes in tumor progression faster than conventional anatomic MRI in patient-derived glioblastoma murine models. To capture the dynamic nature of cancer metabolism, hyperpolarized MRI, NMR spectroscopy, and immunohistochemistry were performed at several time-points during tumor development, regression, and recurrence. Hyperpolarized MRI detected significant changes of metabolism throughout tumor progression whereas conventional MRI was less sensitive. This was accompanied by aberrations in amino acid and phospholipid lipid metabolism and MCT1 expression. Hyperpolarized MRI can help address clinical challenges such as identifying malignant disease prior to aggressive growth, differentiating pseudoprogression from true progression, and predicting relapse. The individual evolution of these metabolic assays as well as their correlations with one another provides context for further academic research.

P4HA2-induced prolyl hydroxylation suppresses YAP1-mediated prostate cancer cell migration, invasion, and metastasis

Yes-associated protein 1 (YAP1), a key player in the Hippo pathway, has been shown to play a critical role in tumor progression. However, the role of YAP1 in prostate cancer cell invasion, migration, and metastasis is not well defined. Through functional, transcriptomic, epigenomic, and proteomic analyses, we showed that prolyl hydroxylation of YAP1 plays a critical role in the suppression of cell migration, invasion, and metastasis in prostate cancer. Knockdown (KD) or knockout (KO) of YAP1 led to an increase in cell migration, invasion, and metastasis in prostate cancer cells. Microarray analysis showed that the EMT pathway was activated in Yap1-KD cells. ChIP-seq analysis showed that YAP1 target genes are enriched in pathways regulating cell migration. Mass spectrometry analysis identified P4H prolyl hydroxylase in the YAP1 complex and YAP1 was hydroxylated at multiple proline residues. Proline-to-alanine mutations of YAP1 isoform 3 identified proline 174 as a critical residue, and its hydroxylation suppressed cell migration, invasion, and metastasis. KO of P4ha2 led to an increase in cell migration and invasion, which was reversed upon Yap1 KD. Our study identified a novel regulatory mechanism of YAP1 by which P4HA2-dependent prolyl hydroxylation of YAP1 determines its transcriptional activities and its function in prostate cancer metastasis.

Abiraterone acetate plus prednisone in non-metastatic biochemically recurrent castration-naïve prostate cancer

BACKGROUND

Intermittent androgen deprivation therapy (ADT) in biochemically recurrent castration-naïve prostate cancer is non-inferior to continuous therapy. We hypothesised that finite-duration abiraterone acetate plus prednisone (Abi +P) added to ADT will further reduce the duration of treatment exposure by prolonging time to prostate-specific antigen (PSA) recurrence without impacting eugonad state recovery.

METHODS

This phase II, randomised, open-label trial enrolled patients with rising PSA ≥ 0.2 ng/ml after radical prostatectomy and/or a PSA ≥ 1 following radiotherapy. Patients were randomised 1:1 to receive Abi (1 g PO daily) + P (5 mg PO daily) + ADT or ADT alone for 8 months. The primary end-point was PSA-free survival difference at 1 year following completion of therapy.

RESULTS

Between February 2013 and July 2016, 200 patients were enrolled. Of 100 patients randomised to each arm, 99 in the Abi +P arm and 98 in the ADT arm were evaluable. Median follow-up was 64.4 months. Median PSA-free survival was 27.0 months for the Abi +P-treated group versus 19.9 months for the ADT-treated group (hazard ratio [HR] 0.64, 95% confidence interval [CI] 0.47-0.87). The PSA-free survival at 1 year post-treatment completion was 98% for the Abi +P group and 88% for the ADT group. Median time to eugonad state was 13.1 months for the abiraterone-treated group and 12.8 months for the ADT-treated group. Median eugonad PSA-free survival was 12.5 months for the abiraterone-treated group versus 9.0 for the ADT-treated group (HR 0.72, 95% CI 0.53-0.98). There were no significant between-group differences in androgen deprivation-related adverse events.

CONCLUSIONS

In men with biochemically recurrent prostate cancer following definitive treatment of the primary, finite duration treatment with ADT and Abi +P results in a significantly longer PSA relapse-free interval than treatment with ADT alone.

Genetic variants in epithelial-mesenchymal transition genes as predictors of clinical outcomes in localized prostate cancer

BACKGROUND

Epithelial-mesenchymal transition (EMT) plays a pivotal role in the progression of prostate cancer (PCa). However, little is known about genetic variants in the EMT pathway as predictors of aggressiveness, biochemical recurrence (BCR) and disease reclassification in localized PCa.

PATIENTS AND METHODS

In this multistage study, we evaluated 5186 single nucleotide polymorphisms (SNPs) from 264 genes related to EMT pathway to identify SNPs associated with PCa aggressiveness and BCR in the MD Anderson PCa (MDA-PCa) patient cohort (N = 1762), followed by assessment of the identified SNPs with disease reclassification in the active surveillance (AS) cohort (N = 392).

RESULTS

In the MDA-PCa cohort, 312 SNPs were associated with high D'Amico risk (P < 0.05), among which, 14 SNPs in 10 genes were linked to BCR risk. In the AS cohort, 2 of 14 identified SNPs (rs76779889 and rs7083961) in C-terminal Binding Proteins 2 gene were associated with reclassification risk. The associations of rs76779889 with different endpoints were: D'Amico high versus low, odds ratio [95% confidence interval (CI)] = 2.89 (1.32-6.34), P = 0.008; BCR, hazard ratio (HR) (95% CI) = 2.88 (1.42-5.85), P = 0.003; and reclassification, HR (95% CI) = 2.83 (1.40-5.74), P = 0.004. For rs7083961, the corresponding risk estimates were: D'Amico high versus low, odds ratio (95% CI) = 1.69 (1.12-2.57), P = 0.013; BCR, HR (95% CI) = 1.87 (1.15-3.02), P = 0.011 and reclassification, HR (95% CI) = 1.72 (1.09-2.72), P = 0.020. There were cumulative effects of these two SNPs on modulating these endpoints.

CONCLUSION

Genetic variants in EMT pathway may influence the risks of localized PCa's aggressiveness, BCR and disease reclassification, suggesting their potential role in the assessment and management of localized PCa.

Additional SNPs improve risk stratification of a polygenic hazard score for prostate cancer

BACKGROUND

Polygenic hazard scores (PHS) can identify individuals with increased risk of prostate cancer. We estimated the benefit of additional SNPs on performance of a previously validated PHS (PHS46).

MATERIALS AND METHOD

180 SNPs, shown to be previously associated with prostate cancer, were used to develop a PHS model in men with European ancestry. A machine-learning approach, LASSO-regularized Cox regression, was used to select SNPs and to estimate their coefficients in the training set (75,596 men). Performance of the resulting model was evaluated in the testing/validation set (6,411 men) with two metrics: (1) hazard ratios (HRs) and (2) positive predictive value (PPV) of prostate-specific antigen (PSA) testing. HRs were estimated between individuals with PHS in the top 5% to those in the middle 40% (HR95/50), top 20% to bottom 20% (HR80/20), and bottom 20% to middle 40% (HR20/50). PPV was calculated for the top 20% (PPV80) and top 5% (PPV95) of PHS as the fraction of individuals with elevated PSA that were diagnosed with clinically significant prostate cancer on biopsy.

RESULTS

166 SNPs had non-zero coefficients in the Cox model (PHS166). All HR metrics showed significant improvements for PHS166 compared to PHS46: HR95/50 increased from 3.72 to 5.09, HR80/20 increased from 6.12 to 9.45, and HR20/50 decreased from 0.41 to 0.34. By contrast, no significant differences were observed in PPV of PSA testing for clinically significant prostate cancer.

CONCLUSIONS

Incorporating 120 additional SNPs (PHS166 vs PHS46) significantly improved HRs for prostate cancer, while PPV of PSA testing remained the same.

Multiple pathways coordinating reprogramming of endothelial cells into osteoblasts by BMP4

Cell type transition occurs during normal development and under pathological conditions. In prostate cancer bone metastasis, prostate cancer-secreted BMP4 induces endothelial cell-to-osteoblast (EC-to-OSB) transition. Such tumor-induced stromal reprogramming supports prostate cancer progression. We delineate signaling pathways mediating EC-to-OSB transition using EC lines 2H11 and SVR. We found that BMP4-activated pSmad1-Notch-Hey1 pathway inhibits EC migration and tube formation. BMP4-activated GSK3β-βcatenin-Slug pathway stimulates Osx expression. In addition, pSmad1-regulated Dlx2 converges with the Smad1 and β-catenin pathways to stimulate osteocalcin expression. By co-expressing Osx, Dlx2, Slug and Hey1, we were able to achieve EC-to-OSB transition, leading to bone matrix mineralization in the absence of BMP4. In human prostate cancer bone metastasis specimens and MDA-PCa-118b and C4-2b-BMP4 osteogenic xenografts, immunohistochemical analysis showed that β-catenin and pSmad1 are detected in activated osteoblasts rimming the tumor-induced bone. Our results elucidated the pathways and key molecules coordinating prostate cancer-induced stromal programming and provide potential targets for therapeutic intervention.

Radium-223 Treatment Increases Immune Checkpoint Expression in Extracellular Vesicles from the Metastatic Prostate Cancer Bone Microenvironment

PURPOSE

Radium-223 prolongs survival in a fraction of men with bone metastatic prostate cancer (PCa). However, there are no markers for monitoring response and resistance to Radium-223 treatment. Exosomes are mediators of intercellular communication and may reflect response of the bone microenvironment to Radium-223 treatment. We performed molecular profiling of exosomes and compared the molecular profile in patients with favorable and unfavorable overall survival.

EXPERIMENTAL DESIGN

We performed exosomal transcriptome analysis in plasma derived from our preclinical models (MDA-PCa 118b tumors, TRAMP-C2/BMP4 PCa) and from the plasma of 25 patients (paired baseline and end of treatment) treated with Radium-223. All samples were run in duplicate, and array data analyzed with fold changes +2 to -2 and P < 0.05.

RESULTS

We utilized the preclinical models to establish that genes derived from the tumor and the tumor-associated bone microenvironment (bTME) are differentially enriched in plasma exosomes upon Radium-223 treatment. The mouse transcriptome analysis revealed changes in bone-related and DNA damage repair-related pathways. Similar findings were observed in plasma-derived exosomes from patients treated with Radium-223 detected changes. In addition, exosomal transcripts detected immune-suppressors (e.g., PD-L1) that were associated with shorter survival to Radium-223. Treatment of the Myc-CaP mouse model with a combination of Radium-223 and immune checkpoint therapy (ICT) resulted in greater efficacy than monotherapy.

CONCLUSIONS

These clinical and coclinical analyses showed that RNA profiling of plasma exosomes may be used for monitoring the bTME in response to treatment and that ICT may be used to increase the efficacy of Radium-223.

Genome-wide DNA methylation profiling of leukocytes identifies CpG methylation signatures of aggressive prostate cancer

Most of screening-detected prostate cancer (PCa) are indolent and not lethal. Biomarkers that can predict aggressive diseases independently of clinical features are needed to improve risk stratification of localized PCa patients and reduce overtreatment. We aimed to identify leukocyte DNA methylation differences between clinically defined aggressive and non-aggressive PCa. We performed whole genome DNA methylation profiling in leukocyte DNA from 287 PCa patients with Gleason Score (GS) 6 and ≥8 using Illumina 450k methylation arrays. We observed a global hypomethylation in GS≥8 patients compared to GS=6 PCa patients; in contrast, the methylation level in core promoter and exon 1 region was significantly higher in GS≥8 patients than GS=6 PCa. We then performed 5-fold cross validated random forest model training on 1,459 differentially methylated CpG Probes (DMPs) with false discovery rate (FDR) <0.01 between GS=6 and GS≥8 groups. The power of the predictive model was further reinforced by ranking the DMPs with Decreased Gini and re-train the model with the top 97 DMPs (Testing AUC=0.920, predict accuracy =0.847). In conclusion, we identified a CpG methylation signature in leukocyte DNA that is associated with aggressive clinical features of PCa at diagnosis.

Polygenic hazard score is associated with prostate cancer in multi-ethnic populations

Genetic models for cancer have been evaluated using almost exclusively European data, which could exacerbate health disparities. A polygenic hazard score (PHS1) is associated with age at prostate cancer diagnosis and improves screening accuracy in Europeans. Here, we evaluate performance of PHS2 (PHS1, adapted for OncoArray) in a multi-ethnic dataset of 80,491 men (49,916 cases, 30,575 controls). PHS2 is associated with age at diagnosis of any and aggressive (Gleason score ≥ 7, stage T3-T4, PSA ≥ 10 ng/mL, or nodal/distant metastasis) cancer and prostate-cancer-specific death. Associations with cancer are significant within European (n = 71,856), Asian (n = 2,382), and African (n = 6,253) genetic ancestries (p < 10-180). Comparing the 80th/20th PHS2 percentiles, hazard ratios for prostate cancer, aggressive cancer, and prostate-cancer-specific death are 5.32, 5.88, and 5.68, respectively. Within European, Asian, and African ancestries, hazard ratios for prostate cancer are: 5.54, 4.49, and 2.54, respectively. PHS2 risk-stratifies men for any, aggressive, and fatal prostate cancer in a multi-ethnic dataset.

A Phase 2 Trial of Abiraterone Followed by Randomization to Addition of Dasatinib or Sunitinib in Men With Metastatic Castration-Resistant Prostate Cancer

BACKGROUND

Resistance to novel androgen signaling inhibition and metastatic castration-resistant prostate cancer (mCRPC) progression is likely dependent on tumor microenvironment interactions. The Src pathway and neoangiogenesis have been implicated in prostate cancer progression. We studied the effect of adding the targeted agents dasatinib and sunitinib to abiraterone acetate (AA) in men with mCRPC.

PATIENTS AND METHODS

In this open-label randomized phase 2 study, mCRPC patients received AA. At resistance to AA, they were randomized 1:1 to combination with dasatinib or sunitinib. At second progression, patients crossed over. The primary end point was time to treatment failure (TTF), defined as time to progression or death. Secondary end points included overall survival and safety.

RESULTS

From March 2011 to February 2015, a total of 179 patients were enrolled and 132 subsequently randomized. Median TTF was 5.7 months in the dasatinib group and 5.5 months in the sunitinib group. There was no difference between the two groups in terms of TTF (hazard ratio, 0.85; 95% confidence interval, 0.59-1.22). Median overall survival from study entry was 26.3 months in the dasatinib group and 27.7 months in the sunitinib group (hazard ratio, 1.02; 95% confidence interval, 0.71-1.47). Grade 3 or higher adverse events related to study medication were more frequent with sunitinib (n = 44, 46%) compared to dasatinib (n = 26, 24%). At data cutoff, 7 patients were experiencing a continuous response to AA, with a median duration of treatment of 5.7 years.

CONCLUSION

There is no difference in overall survival and TTF between dasatinib and sunitinib combined with abiraterone in the treatment of patients with bone mCRPC.

Trans-ancestry genome-wide association meta-analysis of prostate cancer identifies new susceptibility loci and informs genetic risk prediction

Prostate cancer is a highly heritable disease with large disparities in incidence rates across ancestry populations. We conducted a multiancestry meta-analysis of prostate cancer genome-wide association studies (107,247 cases and 127,006 controls) and identified 86 new genetic risk variants independently associated with prostate cancer risk, bringing the total to 269 known risk variants. The top genetic risk score (GRS) decile was associated with odds ratios that ranged from 5.06 (95% confidence interval (CI), 4.84-5.29) for men of European ancestry to 3.74 (95% CI, 3.36-4.17) for men of African ancestry. Men of African ancestry were estimated to have a mean GRS that was 2.18-times higher (95% CI, 2.14-2.22), and men of East Asian ancestry 0.73-times lower (95% CI, 0.71-0.76), than men of European ancestry. These findings support the role of germline variation contributing to population differences in prostate cancer risk, with the GRS offering an approach for personalized risk prediction.

Application of a Successful Germ Cell Tumor Paradigm to the Challenges of Common Adult Solid Cancers

When we aspire to cure cancer, we may need to search no further than a curable cancer, such as Germ Cell Tumor of the Testis (TGCT). After all, a germ cell is a primordial stem cell. Importantly, TGCT provides a classic stem cell model of cancer that teaches us some invaluable lessons about curing other intractable solid tumors. The intrinsic intratumoral heterogeneity of TGCT alludes to its stem-ness origin and nature. Which implicates the existence of putative lethal TGCT subtypes-the identification and detection of which may further enhance the cure rate and improve the therapeutic ratio of TGCT. In this Mini review, we discuss about the role of biologic insights, clinical lessons, and therapeutic strategies in drug and therapy development. We illustrate some clinical pearls and perils when it concerns drug versus therapy development in the cure and care of patients with TGCT. In many respects, we have cured more TGCT patients when we apply multimodal therapy rather than targeted therapy and integrated medicine rather than precision medicine. In principle and in practice, this is the implication of therapy versus drug development in improving the overall outcome and cure rate of patients with cancer.

The CHEK2 Variant C.349A>G Is Associated with Prostate Cancer Risk and Carriers Share a Common Ancestor

The identification of recurrent founder variants in cancer predisposing genes may have important implications for implementing cost-effective targeted genetic screening strategies. In this study, we evaluated the prevalence and relative risk of the CHEK2 recurrent variant c.349A>G in a series of 462 Portuguese patients with early-onset and/or familial/hereditary prostate cancer (PrCa), as well as in the large multicentre PRACTICAL case-control study comprising 55,162 prostate cancer cases and 36,147 controls. Additionally, we investigated the potential shared ancestry of the carriers by performing identity-by-descent, haplotype and age estimation analyses using high-density SNP data from 70 variant carriers belonging to 11 different populations included in the PRACTICAL consortium. The CHEK2 missense variant c.349A>G was found significantly associated with an increased risk for PrCa (OR 1.9; 95% CI: 1.1-3.2). A shared haplotype flanking the variant in all carriers was identified, strongly suggesting a common founder of European origin. Additionally, using two independent statistical algorithms, implemented by DMLE+2.3 and ESTIAGE, we were able to estimate the age of the variant between 2300 and 3125 years. By extending the haplotype analysis to 14 additional carrier families, a shared core haplotype was revealed among all carriers matching the conserved region previously identified in the high-density SNP analysis. These findings are consistent with CHEK2 c.349A>G being a founder variant associated with increased PrCa risk, suggesting its potential usefulness for cost-effective targeted genetic screening in PrCa families.

Mitochondrial DNA copy number in peripheral blood leukocytes is associated with biochemical recurrence in prostate cancer patients in African Americans

Mitochondria play multiple important cellular functions. The purpose of this study was to evaluate whether leukocyte mitochondrial DNA copy number (mtDNAcn) is associated with aggressive prostate cancer (PCa) in African American (AA) men. We measured the mtDNAcn in peripheral blood leukocytes from 317 localized AA PCa patients and evaluated its associations with aggressive disease features at diagnosis and biochemical recurrence (BCR) after treatments. There was no significant difference in mtDNAcn among the clinical features at diagnosis, including age, prostate-specific antigen level, Gleason score and clinical stage under analysis of variance test. However, mtDNAcn was significantly associated with BCR in multivariate Cox analysis. Dichotomized into low and high mtDNAcn groups by the median value of mtDNAcn, patients with low mtDNAcn exhibited a significantly lower risk of BCR (hazard ratio = 0.32, 95% confidence interval: 0.13-0.79) compared to those with high mtDNAcn. There was a significant dose-response in tertile and quartile analyses (P for trend = 0.012 and 0.002, respectively). In Kaplan-Meier survival analyses, patients with higher mtDNAcn exhibited significantly shorter BCR-free survival time than those with lower mtDNAcn in dichotomous, tertile and quartile analyses, with long-rank P values of 0.017, 0.024 and 0.019, respectively. Our results showed for the first time that high leukocyte mtDNAcn was associated with worse prognosis in AA PCa patients.

Fibroblast growth factors signaling in bone metastasis

Many solid tumors metastasize to bone, but only prostate cancer has bone as a single, dominant metastatic site. Recently, the FGF axis has been implicated in cancer progression in some tumors and mounting evidence indicate that it mediates prostate cancer bone metastases. The FGF axis has an important role in bone biology and mediates cell-to-cell communication. Therefore, we discuss here basic concepts of bone biology, FGF signaling axis, and FGF axis function in adult bone, to integrate these concepts in our current understanding of the role of FGF axis in bone metastases.

The MD Anderson Prostate Cancer Patient-derived Xenograft Series (MDA PCa PDX) Captures the Molecular Landscape of Prostate Cancer and Facilitates Marker-driven Therapy Development

PURPOSE

Advances in prostate cancer lag behind other tumor types partly due to the paucity of models reflecting key milestones in prostate cancer progression. Therefore, we develop clinically relevant prostate cancer models.

EXPERIMENTAL DESIGN

Since 1996, we have generated clinically annotated patient-derived xenografts (PDXs; the MDA PCa PDX series) linked to specific phenotypes reflecting all aspects of clinical prostate cancer.

RESULTS

We studied two cell line-derived xenografts and the first 80 PDXs derived from 47 human prostate cancer donors. Of these, 47 PDXs derived from 22 donors are working models and can be expanded either as cell lines (MDA PCa 2a and 2b) or PDXs. The histopathologic, genomic, and molecular characteristics (androgen receptor, ERG, and PTEN loss) maintain fidelity with the human tumor and correlate with published findings. PDX growth response to mouse castration and targeted therapy illustrate their clinical utility. Comparative genomic hybridization and sequencing show significant differences in oncogenic pathways in pairs of PDXs derived from different areas of the same tumor. We also identified a recurrent focal deletion in an area that includes the speckle-type POZ protein-like (SPOPL) gene in PDXs derived from seven human donors of 28 studied (25%). SPOPL is a SPOP paralog, and SPOP mutations define a molecular subclass of prostate cancer. SPOPL deletions are found in 7% of The Cancer Genome Atlas prostate cancers, which suggests that our cohort is a reliable platform for targeted drug development.

CONCLUSIONS

The MDA PCa PDX series is a dynamic resource that captures the molecular landscape of prostate cancers progressing under novel treatments and enables optimization of prostate cancer-specific, marker-driven therapy.

Radium 223-Mediated Zonal Cytotoxicity of Prostate Cancer in Bone

BACKGROUND

Bone-targeting radiotherapy with Radium-223 (Rad-223), a radioisotope emitting genotoxic alpha-radiation with limited tissue penetrance (∼100 µm), prolongs the survival of patients with metastatic prostate cancer (PCa). Confoundingly, the clinical response to Rad-223 is often followed by detrimental relapse and progression, and whether Rad-223 causes tumor-cell directed cytotoxicity in vivo remains unclear. We hypothesized that limited radiation penetrance in situ defines outcome.

METHODS

We tested Rad-223 overall response by PC3 and C4-2B human PCa cell lines in mouse bones (n = 5-18 tibiae per group). Rad-223 efficacy at subcellular resolution was determined by intravital microscopy analysis of dual-color fluorescent PC3 cells (n = 3-4 mice per group) in tissue-engineered bone constructs. In vivo data were fed into an in silico model to predict Rad-223 effectiveness in lesions of different sizes (1-27, 306 initial cells; n = 10-100 simulations) and the predictions validated in vivo by treating PCa tumors of varying sizes in bones (n = 10-14 tibiae per group). Statistical tests were performed by two-sided Student t test or by one-way ANOVA followed by Tukey's post-hoc test.

RESULTS

Rad-223 (385 kBq/kg) delayed the growth (means [SD]; comparison with control-treated mice) of PC3 (6.7 × 105[4.2 × 105] vs 2.8 × 106 [2.2 × 106], P = .01) and C4-2B tumors in bone (7.7 × 105 [4.0 × 105] vs 3.5 × 106 [1.3 × 106], P < .001). Cancer cell lethality in response to Rad-223 (385 kBq/kg) was profound but zonally confined along the bone interface compared with the more distant tumor core, which remained unperturbed (day 4; 13.1 [2.3%] apoptotic cells, 0-100 µm distance from bone vs 3.6 [0.2%], >300 µm distance; P = .01).In silico simulations predicted greater efficacy of Rad-223 on single-cell lesions (eradication rate: 88.0%) and minimal effects on larger tumors (no eradication, 16.2% growth reduction in tumors of 27 306 cells), as further confirmed in vivo for PC3 and C4-2B tumors.

CONCLUSIONS

Micro-tumors showed severe growth delay or eradication in response to Rad-223, whereas macro-tumors persisted and expanded. The relative inefficacy in controlling large tumors points to application of Rad-223 in secondary prevention of early bone-metastatic disease and regimens co-targeting the tumor core.

A candidate androgen signalling signature predictive of response to abiraterone acetate in men with metastatic castration-resistant prostate cancer

BACKGROUND

The unmet need for predictive biomarkers emerged from the unpredictable pattern of response to androgen signalling inhibition in metastatic castration-resistant prostate cancer (mCRPC). Here, we report on the testing of a previously identified candidate androgen signalling signature associated with response to androgen signalling inhibition.

PATIENTS AND METHODS

We report on the outcome of the first module of a phase II trial on abiraterone acetate (AA) followed by combination with dasatinib or sunitinib. Bone marrow biopsies (BMBs) with matched bone marrow aspirate and blood samples were collected at baseline and upon progression. End-points included assessment of a prespecified molecular signature consisting of nuclear androgen receptor (AR) overexpression, cytochrome P450, family 17, subfamily A, polypeptide 1 (CYP17) expression, and AR-C-/N terminal expression ratio of ≥0.8 by immunohistochemistry (IHC) in patients with benefit versus primary resistance to AA (i.e. progression within 4 months). Tumour markers also included v-ets avian erythroblastosis virus E26 oncogene homologue (ERG), androgen receptor splice variant (ARV7) by IHC and steroids by liquid chromatography-tandem mass spectrometry.

RESULTS

Of 170 patients accrued from 03/2011 to 02/2015, 44 (26%) were primary resistant to AA. Forty-eight patients had tumour infiltrated BMB at baseline. Pretreatment androgen signalling signature was linked to benefit from AA (p < 0.001). Presence of ERG was associated with benefit (p = 0.05), whereas nuclear ARV7 presence and 20 or more bone lesions at baseline with primary resistance (p = 0.04 and p = 0.0006, respectively).

CONCLUSION

Testing of a prespecified androgen signalling signature was highly supportive of its predictive value in maximal androgen deprivation strategies in mCRPC. Further validation is under way.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01254864.

Leukocyte telomere length is associated with aggressive prostate cancer in localized prostate cancer patients

BACKGROUND

Telomeres play important roles in cancer initiation and progression. The aim of this study is to investigate whether leukocyte telomere length (LTL) is associated with aggressive prostate cancer (PCa).

METHODS

We measured relative LTL in a cohort of 1,889 white PCa patients who were treated and followed up at the University of Texas MD Anderson Cancer Center and assessed its associations with aggressive disease characteristics at diagnosis and biochemical recurrence (BCR) after active treatments (radical prostatectomy and radiotherapy). We further used a Mendelian randomization (MR) approach to compute a weighted genetic risk score (GRS) predictive of LTL using 10 established LTL-associated genetic variants and determined whether this GRS is associated with aggressive PCa.

FINDINGS

LTL was significantly shorter in patients with higher Gleason scores at diagnosis. Dichotomized at the median value of LTL, patients with short LTL exhibited a 2.74-fold (95% confidence interval, 1.79-4.18, P = 3.11 × 10^-6) increased risk of presenting with GS≥8 disease than those with long LTL in multivariate logistic regression analysis. Moreover, shorter LTL was significantly associated with an increased risk of BCR (hazard ratio = 1.53, 95% confidence interval, 1.01-2.34) compared to longer LTL in localized patients receiving prostatectomy or radiotherapy with a significant dose-response association (P for trend = 0.017) in multivariate Cox proportional hazards regression analysis. In MR analysis, genetically predicted short LTL was also associated with an increased risk of BCR (HR=1.73, 95% CI, 1.08-2.78).

INTERPRETATION

Our results showed for the first time that LTL was shorter in PCa patients with high Gleason scores and that short LTL and genetically predicted short LTL are associated with worse prognosis in PCa patients receiving prostatectomy or radiotherapy.

FUNDING

Cancer Prevention and Research Institute of Texas (CPRIT) grant (RP140556), National Cancer Institute Specialized Program of Research Excellence (SPORE) grant (CA140388), and MD Anderson Cancer Center start-up fund.

Intravital microscopy of osteolytic progression and therapy response of cancer lesions in the bone

Intravital multiphoton microscopy (iMPM) in mice provides access to cellular and molecular mechanisms of metastatic progression of cancers and the underlying interactions with the tumor stroma. Whereas iMPM of malignant disease has been performed for soft tissues, noninvasive iMPM of solid tumor in the bone is lacking. We combined miniaturized tissue-engineered bone constructs in nude mice with a skin window to noninvasively and repetitively monitor prostate cancer lesions by three-dimensional iMPM. In vivo ossicles developed large central cavities containing mature bone marrow surrounded by a thin cortex and enabled tumor implantation and longitudinal iMPM over weeks. Tumors grew inside the bone cavity and along the cortical bone interface and induced niches of osteoclast activation (focal osteolysis). Interventional bisphosphonate therapy reduced osteoclast kinetics and osteolysis without perturbing tumor growth, indicating dissociation of the tumor-stroma axis. The ossicle window, with its high cavity-to-cortex ratio and long-term functionality, thus allows for the mechanistic dissection of reciprocal epithelial tumor-bone interactions and therapy response.

Cabazitaxel plus carboplatin for the treatment of men with metastatic castration-resistant prostate cancers: a randomised, open-label, phase 1-2 trial

BACKGROUND

Taxane-platinum combinations have shown promising activity in metastatic castration-resistant prostate cancers in single-group clinical studies but not in randomised trials. Distinct biological subsets of the disease might derive the greatest benefit from the addition of platinum. We aimed to determine whether adding carboplatin to cabazitaxel would improve the outcomes of men with metastatic castration-resistant prostate cancer.

METHODS

We did a phase 1-2, open label, randomised study at two centres in men with progressive metastatic castration-resistant prostate cancer. In phase 1, patients received intravenous cabazitaxel 20-25 mg/m² and intravenous carboplatin area under the curve (AUC) 3-4 mg/mL per min every 21 days. The maximum tolerated dose was defined as the highest dose cohort studied in which one of six or fewer patients experienced a dose-limiting toxicity. In phase 2, patients were randomly assigned (1:1) centrally by a computerised algorithm to intravenous cabazitaxel 25 mg/m² with or without intravenous carboplatin AUC 4 mg/mL per min. All patients received growth factor support and oral prednisone 10 mg daily. The primary endpoints were the maximum tolerated dose of the combination in phase 1 and investigator-assessed progression-free survival in phase 2. This trial is registered at ClinicalTrials.gov, number NCT01505868.

FINDINGS

Between Aug 17, 2012, and May 11, 2015, nine patients completed phase 1 as planned, and 160 were randomly assigned to cabazitaxel (n=79) or cabazitaxel plus carboplatin (n=81) in phase 2. During phase I, grade 3 adverse events were anaemia (n=2), fatigue (n=1), thrombocytopenia (n=1), hypomagnesaemia (n=1), diarrhoea (n=1), hypokalaemia (n=1), anorexia (n=1), and dehydration (n=1), and no grade 4 adverse events occurred. No dose-limiting toxicities were observed, therefore, a maximum tolerated dose of cabazitaxel of 25 mg/m² and carboplatin of AUC 4 mg/mL per min was selected for phase 2. At a median follow-up of 31·0 months (IQR 20·5-37·1), the combination improved the median progression-free survival from 4·5 months (95% CI 3·5-5·7) to 7·3 months (95% CI 5·5-8·2; hazard ratio 0·69, 95% CI 0·50-0·95, p=0·018). In the phase 2 study, the most common grade 3-5 adverse events were fatigue (7 [9%] of 79 in the cabazitaxel group vs 16 [20%] of 81 in the combination group), anaemia (3 [4%] vs 19 [23%]), neutropenia (3 [4%] vs 13 [16%]), and thrombocytopenia (1 [1%] vs 11 [14%]). There were no treatment-related deaths.

INTERPRETATION

Carboplatin added to cabazitaxel showed improved clinical efficacy compared with cabazitaxel alone for men with metastatic castration-resistant prostate cancer. Although adverse events were more common with the combination, the treatment was safe and generally well tolerated. Our data suggest that taxane-platinum combinations have a clinically beneficial role in advanced prostate cancer and a randomised phase 3 study is planned.

FUNDING

Sanofi Genzyme, University of Texas MD Anderson Cancer Center Prostate Cancer Moon Shot Program, and Solon Scott III Prostate Cancer Research Fund.

Androgen Receptor Signaling in Castration-Resistant Prostate Cancer Alters Hyperpolarized Pyruvate to Lactate Conversion and Lactate Levels In Vivo

PURPOSE

Androgen receptor (AR) signaling affects prostate cancer (PCa) growth, metabolism, and progression. Often, PCa progresses from androgen-sensitive to castration-resistant prostate cancer (CRPC) following androgen-deprivation therapy. Clinicopathologic and genomic characterizations of CRPC tumors lead to subdividing CRPC into two subtypes: (1) AR-dependent CRPC containing dysregulation of AR signaling alterations in AR such as amplification, point mutations, and/or generation of splice variants in the AR gene; and (2) an aggressive variant PCa (AVPC) subtype that is phenotypically similar to small cell prostate cancer and is defined by chemotherapy sensitivity, gain of neuroendocrine or pro-neural marker expression, loss of AR expression, and combined alterations of PTEN, TP53, and RB1 tumor suppressors. Previously, we reported patient-derived xenograft (PDX) animal models that contain characteristics of these CRPC subtypes. In this study, we have employed the PDX models to test metabolic alterations in the CRPC subtypes.

PROCEDURES

Mass spectrometry and nuclear magnetic resonance analysis along with in vivo hyperpolarized 1-[¹³C]pyruvate spectroscopy experiments were performed on prostate PDX animal models.

RESULTS

Using hyperpolarized 1-[¹³C]pyruvate conversion to 1-[¹³C]lactate in vivo as well as lactate measurements ex vivo, we have found increased lactate production in AR-dependent CRPC PDX models even under low-hormone levels (castrated mouse) compared to AR-negative AVPC PDX models.

CONCLUSIONS

Our analysis underscores the potential of hyperpolarized metabolic imaging in determining the underlying biology and in vivo phenotyping of CRPC.