5-Hydroxyeicosatetraenoic Acid Controls Androgen Reduction in Diverse Types of Human Epithelial Cells

Androgens regulate broad physiologic and pathologic processes, including external genitalia development, prostate cancer progression, and anti-inflammatory effects in both cancer and asthma. In prostate cancer, several lines of evidence have implicated dietary and endogenous fatty acids in cell invasion, angiogenesis, and treatment resistance. However, the role of fatty acids in steroidogenesis and the mechanisms by which alterations in this pathway occur are not well understood. Here, we show that, of a panel of fatty acids tested, arachidonic acid and its specific metabolite 5-hydroxyeicosatetraenoic acid (5-HETE) regulate androgen metabolism. Arachidonic acid is metabolized to 5-HETE and reduces androgens by inducing aldo-keto reductase (AKR) family members AKR1C2 and AKR1C3 expression in human prostate, breast, and lung epithelial cells. Finally, we provide evidence that these effects require the expression of the antioxidant response sensor, nuclear factor erythroid 2-related factor 2 (Nrf2). Our findings identify an interconnection between conventional fatty acid metabolism and steroid metabolism that has broad relevance to androgen physiology and inflammatory regulation.

A clinical-grade liquid biomarker detects neuroendocrine differentiation in prostate cancer

BackgroundNeuroendocrine prostate cancer (NEPC) is an aggressive subtype, the presence of which changes the prognosis and management of metastatic prostate cancer.MethodsWe performed analytical validation of a Circulating Tumor Cell (CTC) multiplex RNA qPCR assay to identify the limit of quantification (LOQ) in cell lines, synthetic cDNA, and patient samples. We next profiled 116 longitudinal samples from a prospectively collected institutional cohort of 17 patients with metastatic prostate cancer (7 NEPC, 10 adenocarcinoma) as well as 265 samples from 139 patients enrolled in 3 adenocarcinoma phase II trials of androgen receptor signaling inhibitors (ARSIs). We assessed a NEPC liquid biomarker via the presence of neuroendocrine markers and the absence of androgen receptor (AR) target genes.ResultsUsing the analytical validation LOQ, liquid biomarker NEPC detection in the longitudinal cohort had a per-sample sensitivity of 51.35% and a specificity of 91.14%. However, when we incorporated the serial information from multiple liquid biopsies per patient, a unique aspect of this study, the per-patient predictions were 100% accurate, with a receiver-operating-curve (ROC) AUC of 1. In the adenocarcinoma ARSI trials, the presence of neuroendocrine markers, even while AR target gene expression was retained, was a strong negative prognostic factor.ConclusionOur analytically validated CTC biomarker can detect NEPC with high diagnostic accuracy when leveraging serial samples that are only feasible using liquid biopsies. Patients with expression of NE genes while retaining AR-target gene expression may indicate the transition to neuroendocrine differentiation, with clinical characteristics consistent with this phenotype.FundingNIH (DP2 OD030734, 1UH2CA260389, R01CA247479, and P30 CA014520), Department of Defense (PC190039 and PC200334), and Prostate Cancer Foundation (Movember Foundation - PCF Challenge Award).

Progression of prostate cancer reprograms MYC-mediated lipid metabolism via lysine methyltransferase 2A

BACKGROUND

The activities of MYC, the androgen receptor, and its associated pioneer factors demonstrate substantial reprogramming between early and advanced prostate cancer. Although previous studies have shown a shift in cellular metabolic requirements associated with prostate cancer progression, the epigenetic regulation of these processes is incompletely described. Here, we have integrated chromatin immunoprecipitation sequencing (ChIP-seq) and whole-transcriptome sequencing to identify novel regulators of metabolism in advanced prostate tumors characterized by elevated MYC activity.

RESULTS

Using ChIP-seq against MYC, HOXB13, and AR in LNCaP cells, we observed redistribution of co-bound sites suggestive of differential KMT2A activity as a function of MYC expression. In a cohort of 177 laser-capture microdissected foci of prostate tumors, KMT2A expression was positively correlated with MYC activity, AR activity, and HOXB13 expression, but decreased with tumor grade severity. However, KMT2A expression was negatively correlated with these factors in 25 LuCaP patient-derived xenograft models of advanced prostate cancer and 99 laser-capture microdissected foci of metastatic castration-resistant prostate cancer. Stratified by KMT2A expression, ChIP-seq against AR and HOXB13 in 15 LuCaP patient-derived xenografts showed an inverse association with sites involving genes implicated in lipid metabolism, including the arachidonic acid metabolic enzyme PLA2G4F. LuCaP patient-derived xenograft models grown as organoids recapitulated the inverse association between KMT2A expression and fluorine-18 labeled arachidonic acid uptake in vitro.

CONCLUSIONS

Our study demonstrates that the epigenetic activity of transcription factor oncogenes exhibits a shift during prostate cancer progression with distinctive phenotypic effects on metabolism. These epigenetically driven changes in lipid metabolism may serve as novel targets for the development of novel imaging agents and therapeutics.

Discovery of a Highly Potent and Selective Dual PROTAC Degrader of CDK12 and CDK13

Selective degradation of the cyclin-dependent kinases 12 and 13 (CDK12/13) presents a novel therapeutic opportunity for triple-negative breast cancer (TNBC), but there is still a lack of dual CDK12/13 degraders. Here, we report the discovery of the first series of highly potent and selective dual CDK12/13 degraders by employing the proteolysis-targeting chimera (PROTAC) technology. The optimal compound 7f effectively degraded CDK12 and CDK13 with DC50 values of 2.2 and 2.1 nM, respectively, in MDA-MB-231 breast cancer cells. Global proteomic profiling demonstrated the target selectivity of 7f. In vitro, 7f suppressed expression of core DNA damage response (DDR) genes in a time- and dose-dependent manner. Further, 7f markedly inhibited proliferation of multiple TNBC cell lines including MFM223, with an IC50 value of 47 nM. Importantly, 7f displayed a significantly improved antiproliferative activity compared to the structurally similar inhibitor 4, suggesting the potential advantage of a CDK12/13 degrader for TNBC targeted therapy.

Allele-informed copy number evaluation of plasma DNA samples from metastatic prostate cancer patients: the PCF_SELECT consortium assay

Sequencing of cell-free DNA (cfDNA) in cancer patients' plasma offers a minimally-invasive solution to detect tumor cell genomic alterations to aid real-time clinical decision-making. The reliability of copy number detection decreases at lower cfDNA tumor fractions, limiting utility at earlier stages of the disease. To test a novel strategy for detection of allelic imbalance, we developed a prostate cancer bespoke assay, PCF_SELECT, that includes an innovative sequencing panel covering ∼25 000 high minor allele frequency SNPs and tailored analytical solutions to enable allele-informed evaluation. First, we assessed it on plasma samples from 50 advanced prostate cancer patients. We then confirmed improved detection of genomic alterations in samples with <10% tumor fractions when compared against an independent assay. Finally, we applied PCF_SELECT to serial plasma samples intensively collected from three patients previously characterized as harboring alterations involving DNA repair genes and consequently offered PARP inhibition. We identified more extensive pan-genome allelic imbalance than previously recognized in prostate cancer. We confirmed high sensitivity detection of BRCA2 allelic imbalance with decreasing tumor fractions resultant from treatment and identified complex ATM genomic states that may be incongruent with protein losses. Overall, we present a framework for sensitive detection of allele-specific copy number changes in cfDNA.

PD-L1 blockade restores CAR T cell activity through IFN-γ-regulation of CD163+ M2 macrophages

BACKGROUND

The immune suppressive tumor microenvironment (TME) that inhibits T cell infiltration, survival, and antitumor activity has posed a major challenge for developing effective immunotherapies for solid tumors. Chimeric antigen receptor (CAR)-engineered T cell therapy has shown unprecedented clinical response in treating patients with hematological malignancies, and intense investigation is underway to achieve similar responses with solid tumors. Immunologically cold tumors, including prostate cancers, are often infiltrated with abundant tumor-associated macrophages (TAMs), and infiltration of CD163+ M2 macrophages correlates with tumor progression and poor responses to immunotherapy. However, the impact of TAMs on CAR T cell activity alone and in combination with TME immunomodulators is unclear.

METHODS

To model this in vitro, we utilized a novel co-culture system with tumor cells, CAR T cells, and polarized M1 or M2 macrophages from CD14+ peripheral blood mononuclear cells collected from healthy human donors. Tumor cell killing, T cell activation and proliferation, and macrophage phenotypes were evaluated by flow cytometry, cytokine production, RNA sequencing, and functional blockade of signaling pathways using antibodies and small molecule inhibitors. We also evaluated the TME in humanized mice following CAR T cell therapy for validation of our in vitro findings.

RESULTS

We observed inhibition of CAR T cell activity with the presence of M2 macrophages, but not M1 macrophages, coinciding with a robust induction of programmed death ligand-1 (PD-L1) in M2 macrophages. We observed similar PD-L1 expression in TAMs following CAR T cell therapy in the TME of humanized mice. PD-L1, but not programmed cell death protein-1, blockade in combination with CAR T cell therapy altered phenotypes to more M1-like subsets and led to loss of CD163+ M2 macrophages via interferon-γ signaling, resulting in improved antitumor activity of CAR T cells.

CONCLUSION

This study reveals an alternative mechanism by which the combination of CAR T cells and immune checkpoint blockade modulates the immune landscape of solid tumors to enhance therapeutic efficacy of CAR T cells.

Association between pathogenic germline mutations in BRCA2 and ATM and tumor-infiltrating lymphocytes in primary prostate cancer

Pathogenic mutations in homologous recombination (HR) DNA repair genes may be associated with increased tumor mutational burden and numbers of tumor-infiltrating lymphocytes (TIL). Though HR-deficient prostate tumors have been anecdotally associated with improved responses to immunotherapy, it is unclear whether HR mutations or HR deficiency (HRD) scores predict for increased T-cell densities in this cancer. We evaluated 17 primary prostate tumors from patients with pathogenic germline BRCA2 mutations (gBRCA2) and 21 primary prostate tumors from patients with pathogenic germline ATM (gATM) mutations, which were compared to 19 control tumors lacking HR gene mutations, as well as the TCGA prostate cancer cohort. HRD score was estimated by targeted sequencing (gBRCA2 and gATM) or by SNP microarray (TCGA). Tumor-associated T-cell densities were assessed using validated automated digital image analysis of CD8 and FOXP3 immunostaining (gBRCA2 or gATM) or by methylCIBERSORT (TCGA). CD8 + and FOXP3 + T-cell densities were significantly correlated with each other in gBRCA2 and gATM cases. There was no significant difference between CD8 + or FOXP3 + TIL densities in gBRCA2 or gATM cases compared to controls. In the TCGA cohort, HRD score was associated with predicted CD8 + and FOXP3 + TILs. Associations were also seen for HRD score and TIL density among the germline-mutated cases. In contrast to mismatch repair-deficient primary prostate tumors, cancers from germline BRCA2 or ATM mutation carriers do not appear to be associated with elevated TIL density. However, measures of genomic scarring, such as HRD score, may be associated with increased tumor-infiltrating T-cells.

A non-coding RNA balancing act: miR-346-induced DNA damage is limited by the long non-coding RNA NORAD in prostate cancer

BACKGROUND

miR-346 was identified as an activator of Androgen Receptor (AR) signalling that associates with DNA damage response (DDR)-linked transcripts in prostate cancer (PC). We sought to delineate the impact of miR-346 on DNA damage, and its potential as a therapeutic agent.

METHODS

RNA-IP, RNA-seq, RNA-ISH, DNA fibre assays, in vivo xenograft studies and bioinformatics approaches were used alongside a novel method for amplification-free, single nucleotide-resolution genome-wide mapping of DNA breaks (INDUCE-seq).

RESULTS

miR-346 induces rapid and extensive DNA damage in PC cells - the first report of microRNA-induced DNA damage. Mechanistically, this is achieved through transcriptional hyperactivation, R-loop formation and replication stress, leading to checkpoint activation and cell cycle arrest. miR-346 also interacts with genome-protective lncRNA NORAD to disrupt its interaction with PUM2, leading to PUM2 stabilisation and its increased turnover of DNA damage response (DDR) transcripts. Confirming clinical relevance, NORAD expression and activity strongly correlate with poor PC clinical outcomes and increased DDR in biopsy RNA-seq studies. In contrast, miR-346 is associated with improved PC survival. INDUCE-seq reveals that miR-346-induced DSBs occur preferentially at binding sites of the most highly-transcriptionally active transcription factors in PC cells, including c-Myc, FOXA1, HOXB13, NKX3.1, and importantly, AR, resulting in target transcript downregulation. Further, RNA-seq reveals widespread miR-346 and shNORAD dysregulation of DNA damage, replication and cell cycle processes. NORAD drives target-directed miR decay (TDMD) of miR-346 as a novel genome protection mechanism: NORAD silencing increases mature miR-346 levels by several thousand-fold, and WT but not TDMD-mutant NORAD rescues miR-346-induced DNA damage. Importantly, miR-346 sensitises PC cells to DNA-damaging drugs including PARP inhibitor and chemotherapy, and induces tumour regression as a monotherapy in vivo, indicating that targeting miR-346:NORAD balance is a valid therapeutic strategy.

CONCLUSIONS

A balancing act between miR-346 and NORAD regulates DNA damage and repair in PC. miR-346 may be particularly effective as a therapeutic in the context of decreased NORAD observed in advanced PC, and in transcriptionally-hyperactive cancer cells.

Phase 2 trial of T-cell activation using MVI-816 and pembrolizumab in patients with metastatic, castration-resistant prostate cancer (mCRPC)

Background

We previously reported a trial using a DNA vaccine encoding prostatic acid phosphatase (MVI-816, pTVG-HP), given over 12 weeks concurrently or sequentially with pembrolizumab, in patients with mCRPC. We report the final analysis of this trial following two additional treatment arms in which patients with mCRPC continued concurrent treatment until progression.

Materials and methods

Patients with mCRPC were treated with MVI-816 and pembrolizumab every 3 weeks (arm 3, n=20) or MVI-816 every 2 weeks and pembrolizumab every 4 weeks (arm 4, n=20). The primary objectives were safety, 6-month progression-free survival (PFS), median time to radiographic progression, and objective response rates. Secondary objectives included immunological evaluations.

Results

In 25 patients with measurable disease, there were no complete response and one confirmed partial response in a patient who subsequently found to have an MSI^hi tumor. 4/40 patients (10%) had a prostate-specific antigen decline >50%. The estimated overall radiographic PFS rate at 6 months was 47.2% (44.4% arm 3, 61.5% arm 4). Accounting for all off-study events, overall median time on treatment was 5.6 months (95% CI: 5.4 to 10.8 months), 5.6 months for arm 3 and 8.1 months for arm 4 (p=0.64). Thirty-two per cent of patients remained on trial beyond 6 months without progression. Median overall survival was 22.9 (95% CI: 16.2 to 25.6) months. One grade 4 event (hyperglycemia) was observed. Immune-related adverse events (irAEs) >grade 1 were observed in 42% of patients overall. Interferon-γ and/or granzyme B immune response to prostatic acid phosphatase was detected in 2/20 patients in arm 3 and 6/20 patients in arm 4. Plasma cytokines associated with immune activation and CD8+ T-cell recruitment were augmented at weeks 6 and 12. The development of irAE was significantly associated with a prolonged time on treatment (HR=0.42, p=0.003). Baseline DNA homologous recombination repair mutations were not associated with longer time to progression.

Conclusions

Findings here demonstrate that combining programmed cell death 1 blockade with MVI-816 is safe, can augment tumor-specific T cells, and can result in a favorable 6-month disease control rate. Correlative studies suggest T-cell activation by vaccination is critical to the mechanism of action of this combination. Future randomized clinical trials are needed to validate these findings.

Trial registration number

NCT02499835.

Novel Redirected T-Cell Immunotherapies for Advanced Prostate Cancer

Immunotherapy has failed to achieve durable remissions in advanced prostate cancer patients. More potent T-cell-redirecting strategies may be needed to overcome the immunologically exclusive and suppressive tumor microenvironment. Clinical trials are underway, seeking to define the optimal target for T-cell redirection, such as PSMA, PSCA, or STEAP-1, as well as the optimal strategy, with CAR or bispecific antibodies. As results continue to emerge from these trials, understanding differential toxicity and efficacy of these therapies based on their targets and functional modifications will be key to advancing these promising therapies toward clinical practice. This review provides a unique depth and breadth of perspective regarding the diverse immunotherapy strategies currently under clinical investigation for men with advanced prostate cancer.

Cellular specificity of androgen receptor, coregulators, and pioneer factors in prostate cancer

Androgen signalling, through the transcription factor androgen receptor (AR), is vital to all stages of prostate development and most prostate cancer progression. AR signalling controls differentiation, morphogenesis, and function of the prostate. It also drives proliferation and survival in prostate cancer cells as the tumour progresses; given this importance, it is the main therapeutic target for disseminated disease. AR is also essential in the surrounding stroma, for the embryonic development of the prostate and controlling epithelial glandular development. Stromal AR is also important in cancer initiation, regulating paracrine factors that excite cancer cell proliferation, but lower stromal AR expression correlates with shorter time to progression/worse outcomes. The profile of AR target genes is different between benign and cancerous epithelial cells, between castrate-resistant prostate cancer cells and treatment-naïve cancer cells, between metastatic and primary cancer cells, and between epithelial cells and fibroblasts. This is also true of AR DNA-binding profiles. Potentially regulating the cellular specificity of AR binding and action are pioneer factors and coregulators, which control and influence the ability of AR to bind to chromatin and regulate gene expression. The expression of these factors differs between benign and cancerous cells, as well as throughout disease progression. The expression profile is also different between fibroblast and mesenchymal cell types. The functional importance of coregulators and pioneer factors in androgen signalling makes them attractive therapeutic targets, but given the contextual expression of these factors, it is essential to understand their roles in different cancerous and cell-lineage states.

Chemically Tuning the Antigen Release Kinetics from Spherical Nucleic Acids Maximizes Immune Stimulation

Cancer vaccine structure is emerging as an important design factor that offers tunable parameters to enhance the targeted immune response. We report the impact of altering the antigen release rate from spherical nucleic acid (SNA) vaccines-nanoparticles with a liposomal core and surface-anchored adjuvant DNA-on immune stimulation. Peptide antigens were incorporated into SNAs using either a nonreducible linker or one of a series of reduction-triggered traceless linkers that release the native peptide at rates controlled by their substitution pattern. Compared with a nonreducible linkage, the traceless attachment of antigens resulted in lower EC50 of T cell proliferation in vitro and greater dendritic cell (DC) activation and higher T cell killing ability in vivo. Traceless linker fragmentation rates affected the rates of antigen presentation by DCs and were correlated with the in vitro potencies of SNAs. Antigen release was correlated with the ex vivo -log(EC50), and more rapid antigen release resulted in an order of magnitude improvement in the EC50 and earlier and greater antigen presentation over the same time-period. In vivo, increasing the rate of antigen release resulted in higher T cell activation and target killing. These findings provide fundamental insights into and underscore the importance of vaccine structure.

Factors that influence clinicians' decisions to decrease active surveillance monitoring frequency or transition to watchful waiting for localised prostate cancer: a qualitative study

OBJECTIVE

Little is known about clinicians' decision-making about decreasing active surveillance (AS) testing/converting patients to watchful waiting (WW), nor are there any guidelines. The objective of this study was to identify factors that clinicians consider when decreasing AS testing/converting to WW for men with prostate cancer.

DESIGN

Exploratory qualitative study.

SETTING

All participants practiced in various institutions in the USA.

PARTICIPANTS

Eligible clinicians had to provide clinical care for patients with prostate cancer in the USA and speak English. Clinicians could be either urologists or radiation oncologists. Of the 24 clinicians, 83% were urologists representing 11 states, 92% were men and 62% were white.

METHODS

This qualitative study used data from semi-structured interviews. Purposive sampling was used to ensure geographical variation in the USA. Data collection continued until thematic saturation was achieved. Framework analysis guided coding and identification of themes. Two researchers coded all transcripts independently, met to discuss and reached consensus.

RESULTS

Interviews with clinicians demonstrated that testing or monitoring for AS or transitioning to WW is happening in practice, whether intentionally or unintentionally. Decisions to decrease AS were personalised and tailored to patients' health status. Life expectancy was the dominant factor that influenced decision, but clinicians were generally hesitant to specify an age when they would decrease AS or transition to WW. Fear that poor adherence could lead to missed progression and concerns about the medico-legal issue of not doing enough were cited as barriers to decreasing AS.

CONCLUSIONS

These findings suggest that in certain situations, AS frequency is reduced or transitioned to WW, yet decisions appear to be inconsistent and there are no significant barriers. These findings could inform further areas to explore when drafting recommendations that consider patients' values and preferences when making decisions about decreasing AS/converting to WW.

Protocol: A multi-modal, physician-centered intervention to improve guideline-concordant prostate cancer imaging

BACKGROUND

Almost half of Veterans with localized prostate cancer receive inappropriate, wasteful staging imaging. Our team has explored the barriers and facilitators of guideline-concordant prostate cancer imaging and found that (1) patients with newly diagnosed prostate cancer have little concern for radiographic staging but rather focus on treatment and (2) physicians trust imaging guidelines but are apt to follow their own intuition, fear medico-legal consequences, and succumb to influence from imaging-avid colleagues. We used a theory-based approach to design a multi-level intervention strategy to promote guideline-concordant imaging to stage incident prostate cancer.

METHODS

We designed the Prostate Cancer Imaging Stewardship (PCIS) intervention: a multi-site, stepped wedge, cluster-randomized trial to determine the effect of a physician-focused behavioral intervention on Veterans Health Administration (VHA) prostate cancer imaging use. The multi-level intervention, developed according to the Theoretical Domains Framework (TDF) and Behavior Change Wheel, combines traditional physician behavior change methods with novel methods of communication and data collection. The intervention consists of three components: (1) a system of audit and feedback to clinicians informing individual clinicians and their sites about how their behavior compares to their peers' and to published guidelines, (2) a program of academic detailing with the goal to educate providers about prostate cancer imaging, and (3) a CPRS Clinical Order Check for potentially guideline-discordant imaging orders. The intervention will be introduced to 10 participating geographically distributed study sites.

DISCUSSION

This study is a significant contribution to implementation science, providing VHA an opportunity to ensure delivery of high-quality care at the lowest cost using a theory-based approach. The study is ongoing. Preliminary data collection and recruitment have started; analysis has yet to be performed.

TRIAL REGISTRATION

CliniclTrials.gov NCT03445559. Prospectively registered on February 26, 2018.

Wnt and β-Catenin Signaling in the Bone Metastasis of Prostate Cancer

Wnt family proteins and β-catenin are critical for the regulation of many developmental and oncogenic processes. Wnts are secreted protein ligands which signal using a canonical pathway, and involve the transcriptional co-activator β-catenin or non-canonical pathways that are independent of β-catenin. Bone metastasis is unfortunately a common occurrence in prostate cancer and can be conceptualized as a series of related steps or processes, most of which are regulated by Wnt ligands and/or β-catenin. At the primary tumor site, cancer cells often take on mesenchymal properties, termed epithelial mesenchymal transition (EMT), which are regulated in part by the Wnt receptor FZD4. Then, Wnt signaling, especially Wnt5A, is of importance as the cells circulate in the blood stream. Upon arriving in the bones, cancer cells migrate and take on stem-like or tumorigenic properties, as aided through Wnt or β-catenin signaling involving CHD11, CD24, and Wnt5A. Additionally, cancer cells can become dormant and evade therapy, in part due to regulation by Wnt5A. In the bones, E-selectin can aid in the reversal of EMT, a process termed mesenchymal epithelial transition (MET), as a part of metastatic tumorigenesis. Once bone tumors are established, Wnt/β-catenin signaling is involved in the suppression of osteoblast function largely through DKK1.

Prostate cancer patients' self-reported participation in research: an examination of racial/ethnic disparities

PURPOSE

We examined prostate cancer patients' participation in research and associated factors by race/ethnicity in a multiethnic sample.

METHODS

Men with a new diagnosis of prostate cancer were identified through the California Cancer Registry. Patients completed a cross-sectional telephone interview in English, Spanish, Cantonese or Mandarin. Multivariable logistic regression models, stratified by race/ethnicity, estimated the associations of patient demographic and health characteristics with participation in (1) any research, (2) behavioral research, and (3) biological/clinical research.

RESULTS

We included 855 prostate cancer patients: African American (19%), Asian American (15%), Latino (24%), and White (42%). In the overall model of participation in any research, African American men (Odds Ratio (OR) = 2.54, 95% CI 1.63-3.94), and those with two or more comorbidities (OR = 2.20, 95% CI 1.27-3.80) were more likely to report participation. Men 65 years old and older (OR = 0.65, 95% CI 0.47-0.91), those who were married or living with a partner (OR = 0.67, 95% CI 0.45-0.98), and those who completed the interview in Spanish (OR = 0.36, 95% CI 0.15-0.85) were less likely to report participating in any research. Stratified analyses identified racial/ethnic-specific sociodemographic characteristics associated with lower research participation, including Spanish or Chinese language, older age, and lower education.

CONCLUSION

African American prostate cancer patients reported higher research participation than all other groups. However, recruitment efforts are still needed to overcome barriers to participation for Spanish and Chinese speakers, and barriers among older adults and those with lower education levels.

Integrated evaluation of telomerase activation and telomere maintenance across cancer cell lines

In cancer, telomere maintenance is critical for the development of replicative immortality. Using genome sequences from the Cancer Cell Line Encyclopedia and Genomics of Drug Sensitivity in Cancer Project, we calculated telomere content across 1299 cancer cell lines. We find that telomerase reverse transcriptase (TERT) expression correlates with telomere content in lung, central nervous system, and leukemia cell lines. Using CRISPR/Cas9 screening data, we show that lower telomeric content is associated with dependency of CST telomere maintenance genes. Increased dependencies of shelterin members are associated with wild-type TP53 status. Investigating the epigenetic regulation of TERT, we find widespread allele-specific expression in promoter-wildtype contexts. TERT promoter-mutant cell lines exhibit hypomethylation at PRC2-repressed regions, suggesting a cooperative global epigenetic state in the reactivation of telomerase. By incorporating telomere content with genomic features across comprehensively characterized cell lines, we provide further insights into the role of telomere regulation in cancer immortality.

Targeting Glucocorticoid Metabolism in Prostate Cancer

In the treatment of metastatic prostate cancer, resistance to hormonal therapy is a major obstacle. With antiandrogen therapies that suppress androgen signaling through the androgen receptor (AR), the primary driver of prostate cancer, some malignancies are able take advantage of the closely related glucocorticoid receptor (GR). Escape from AR dependency often involves a simple functional switch from 1 steroid receptor to another. Recent research efforts have outlined the mechanism enabling this switch, which involves alterations in glucocorticoid metabolism that occur with antiandrogen therapy to increase tumor tissue glucocorticoids and enable GR signaling. Targeting this mechanism pharmacologically by blocking hexose-6-phosphate dehydrogenase shows promise in normalizing glucocorticoid metabolism and restoring responsiveness to antiandrogen therapy. This perspective reviews what we have learned about this resistance mechanism, examines potential implications, and considers how this knowledge might be harnessed for therapeutic benefit.

The development of Nanosota-1 as anti-SARS-CoV-2 nanobody drug candidates

Combating the COVID-19 pandemic requires potent and low-cost therapeutics. We identified a series of single-domain antibodies (i.e., nanobody), Nanosota-1, from a camelid nanobody phage display library. Structural data showed that Nanosota-1 bound to the oft-hidden receptor-binding domain (RBD) of SARS-CoV-2 spike protein, blocking viral receptor angiotensin-converting enzyme 2 (ACE2). The lead drug candidate possessing an Fc tag (Nanosota-1C-Fc) bound to SARS-CoV-2 RBD ~3000 times more tightly than ACE2 did and inhibited SARS-CoV-2 pseudovirus ~160 times more efficiently than ACE2 did. Administered at a single dose, Nanosota-1C-Fc demonstrated preventive and therapeutic efficacy against live SARS-CoV-2 infection in both hamster and mouse models. Unlike conventional antibodies, Nanosota-1C-Fc was produced at high yields in bacteria and had exceptional thermostability. Pharmacokinetic analysis of Nanosota-1C-Fc documented an excellent in vivo stability and a high tissue bioavailability. As effective and inexpensive drug candidates, Nanosota-1 may contribute to the battle against COVID-19.

Examining reporting and representation of patients with cancer in COVID-19 clinical trials

BACKGROUND

Patients with cancer are particularly vulnerable in the current COVID-19 pandemic. Emerging evidence suggests that patients with a cancer diagnosis are three times more likely to die from COVID-19 compared to non-cancer patients. Due to these observed risks, it is critical that emerging COVID-19 therapies demonstrate safety and efficacy among patients with cancer.

AIM

This study sought to examine reporting and representation of patients with cancer among published COVID-19 treatment-related research studies.

METHODS AND RESULTS

All published COVID-19 treatment-related clinical research studies published from March 1 to August 20, 2020 recruiting from North America and Europe were identified. The date published, study design, therapeutics studied, and study population were evaluated. Of the 343 studies identified through initial search and researcher knowledge, 55 (16%) reported on COVID-19 treatments. Twenty-one COVID-19 therapeutic studies (n = 15, prospective; n = 6, retrospective) that recruited from the United States and Europe were identified. Among these studies, eight (38%) reported on the number of trial participants with a cancer diagnosis in the publication and two (10%) specified tumor type. Four of the studies (19%) did not collect cancer history. Among studies where cancer history was available, patients with a cancer diagnosis participated at a proportion higher than overall cancer prevalence and greater than the known proportion of COVID-19 patients with cancer.

CONCLUSION

This study observed that cancer history was not uniformly collected or reported among published COVID-19 therapeutic studies. Among reported publications, we observed that patients with a cancer diagnosis were generally overrepresented. However, patients with a cancer diagnosis were notably underrepresented in outpatient COVID-19 therapeutic studies.

Distinct skeletal stem cell types orchestrate long bone skeletogenesis

Skeletal stem and progenitor cell populations are crucial for bone physiology. Characterization of these cell types remains restricted to heterogenous bulk populations with limited information on whether they are unique or overlap with previously characterized cell types. Here we show, through comprehensive functional and single-cell transcriptomic analyses, that postnatal long bones of mice contain at least two types of bone progenitors with bona fide skeletal stem cell (SSC) characteristics. An early osteochondral SSC (ocSSC) facilitates long bone growth and repair, while a second type, a perivascular SSC (pvSSC), co-emerges with long bone marrow and contributes to shape the hematopoietic stem cell niche and regenerative demand. We establish that pvSSCs, but not ocSSCs, are the origin of bone marrow adipose tissue. Lastly, we also provide insight into residual SSC heterogeneity as well as potential crosstalk between the two spatially distinct cell populations. These findings comprehensively address previously unappreciated shortcomings of SSC research.

Intersection of Two Checkpoints: Could Inhibiting the DNA Damage Response Checkpoint Rescue Immune Checkpoint-Refractory Cancer?

Metastatic cancers resistant to immunotherapy require novel management strategies. DNA damage response (DDR) proteins, including ATR (ataxia telangiectasia and Rad3-related), ATM (ataxia telangiectasia mutated) and DNA-PK (DNA-dependent protein kinase), have been promising therapeutic targets for decades. Specific, potent DDR inhibitors (DDRi) recently entered clinical trials. Surprisingly, preclinical studies have now indicated that DDRi may stimulate anti-tumor immunity to augment immunotherapy. The mechanisms governing how DDRi could promote anti-tumor immunity are not well understood; however, early evidence suggests that they can potentiate immunogenic cell death to recruit and activate antigen-presenting cells to prime an adaptive immune response. Merkel cell carcinoma (MCC) is well suited to test these concepts. It is inherently immunogenic as ~50% of patients with advanced MCC persistently benefit from immunotherapy, making MCC one of the most responsive solid tumors. As is typical of neuroendocrine cancers, dysfunction of p53 and Rb with upregulation of Myc leads to the very rapid growth of MCC. This suggests high replication stress and susceptibility to DDRi and DNA-damaging agents. Indeed, MCC tumors are particularly radiosensitive. Given its inherent immunogenicity, cell cycle checkpoint deficiencies and sensitivity to DNA damage, MCC may be ideal for testing whether targeting the intersection of the DDR checkpoint and the immune checkpoint could help patients with immunotherapy-refractory cancers.

Factors influencing treatment of veterans with advanced prostate cancer

BACKGROUND

Treatments for metastatic castration-resistant prostate cancer (CRPC) differ in toxicity, administration, and evidence. In this study, clinical and nonclinical factors associated with the first-line treatment for CRPC in a national delivery system were evaluated.

METHODS

National electronic laboratory and clinical data from the Veterans Health Administration were used to identify patients with CRPC (ie, rising prostate-specific antigen [PSA] on androgen deprivation) who received abiraterone, enzalutamide, docetaxel, or ketoconazole from 2010 through 2017. It was determined whether clinical (eg, PSA) and nonclinical factors (eg, race, facility) were associated with the first-line treatment selection using multilevel, multinomial logistic regression. The average marginal effects (AMEs) were calculated of patient, disease, and facility characteristics on ketoconazole versus more appropriate CRPC therapy.

RESULTS

There were 4998 patients identified with CRPC who received first-line ketoconazole, docetaxel, abiraterone, or enzalutamide. After adjustment, increasing age was associated with receipt of abiraterone (adjusted odds ratio [aOR], 1.07; 95% credible interval [CrI], 1.06-1.09) or enzalutamide (aOR, 1.10; 95% CrI, 1.08-1.11) versus docetaxel. Greater preexisting comorbidity was associated with enzalutamide versus abiraterone (aOR, 1.53; 95% CrI, 1.23-1.91). Patients with higher PSA values at the start of treatment were more likely to receive docetaxel than oral agents and less likely to receive ketoconazole than other oral agents. African American men were more likely to receive ketoconazole than abiraterone, enzalutamide, or docetaxel (AME, 2.8%; 95% CI, 0.7%-4.9%). This effect was attenuated when adjusting for facility characteristics (AME, 1.9%; 95% CI, -0.4% to 4.1%).

CONCLUSIONS

Clinical factors had an expected effect on the first-line treatment selection. Race may be associated with the receipt of a guideline-discordant first-line treatment.

Mapping of m6A and Its Regulatory Targets in Prostate Cancer Reveals a METTL3-Low Induction of Therapy Resistance

Recent evidence has highlighted the role of N ⁶-methyladenosine (m⁶A) in the regulation of mRNA expression, stability, and translation, supporting a potential role for posttranscriptional regulation mediated by m⁶A in cancer. Here, we explore prostate cancer as an exemplar and demonstrate that low levels of N ⁶-adenosine-methyltransferase (METTL3) is associated with advanced metastatic disease. To investigate this relationship, we generated the first prostate m⁶A maps, and further examined how METTL3 regulates expression at the level of transcription, translation, and protein. Significantly, transcripts encoding extracellular matrix proteins are consistently upregulated with METTL3 knockdown. We also examined the relationship between METTL3 and androgen signaling and discovered the upregulation of a hepatocyte nuclear factor-driven gene signature that is associated with therapy resistance in prostate cancer. Significantly, METTL3 knockdown rendered the cells resistant to androgen receptor antagonists via an androgen receptor-independent mechanism driven by the upregulation of nuclear receptor NR5A2/LRH-1. IMPLICATIONS: These findings implicate changes in m⁶A as a mechanism for therapy resistance in metastatic prostate cancer.

Deep immune profiling reveals targetable mechanisms of immune evasion in immune checkpoint inhibitor-refractory glioblastoma

BACKGROUND

Glioblastoma (GBM) is refractory to immune checkpoint inhibitor (ICI) therapy. We sought to determine to what extent this immune evasion is due to intrinsic properties of the tumor cells versus the specialized immune context of the brain, and if it can be reversed.

METHODS

We used CyTOF mass cytometry to compare the tumor immune microenvironments (TIME) of human tumors that are generally ICI-refractory (GBM and sarcoma) or ICI-responsive (renal cell carcinoma), as well as mouse models of GBM that are ICI-responsive (GL261) or ICI-refractory (SB28). We further compared SB28 tumors grown intracerebrally versus subcutaneously to determine how tumor site affects TIME and responsiveness to dual CTLA-4/PD-1 blockade. Informed by these data, we explored rational immunotherapeutic combinations.

RESULTS

ICI-sensitivity in human and mouse tumors was associated with increased T cells and dendritic cells (DCs), and fewer myeloid cells, in particular PD-L1+ tumor-associated macrophages. The SB28 mouse model of GBM responded to ICI when grown subcutaneously but not intracerebrally, providing a system to explore mechanisms underlying ICI resistance in GBM. The response to ICI in the subcutaneous SB28 model required CD4 T cells and NK cells, but not CD8 T cells. Recombinant FLT3L expanded DCs, improved antigen-specific T cell priming, and prolonged survival of mice with intracerebral SB28 tumors, but at the cost of increased Tregs. Targeting PD-L1 also prolonged survival, especially when combined with stereotactic radiation.

CONCLUSIONS

Our data suggest that a major obstacle for effective immunotherapy of GBM is poor antigen presentation in the brain, rather than intrinsic immunosuppressive properties of GBM tumor cells. Deep immune profiling identified DCs and PD-L1+ tumor-associated macrophages as promising targetable cell populations, which was confirmed using therapeutic interventions in vivo.