The Initial Detection and Partial Characterization of Circulating Tumor Cells in Neuroendocrine Prostate Cancer

The yin and yang of chromosomal instability in prostate cancer

Metastatic prostate cancer remains an incurable lethal disease. Studies indicate that prostate cancer accumulates genomic changes during disease progression and displays the highest levels of chromosomal instability (CIN) across all types of metastatic tumours. CIN, which refers to ongoing chromosomal DNA gain or loss during mitosis, and derived aneuploidy, are known to be associated with increased tumour heterogeneity, metastasis and therapy resistance in many tumour types. Paradoxically, high CIN levels are also proposed to be detrimental to tumour cell survival, suggesting that cancer cells must develop adaptive mechanisms to ensure their survival. In the context of prostate cancer, studies indicate that CIN has a key role in disease progression and might also offer a therapeutic vulnerability that can be pharmacologically targeted. Thus, a comprehensive evaluation of the causes and consequences of CIN in prostate cancer, its contribution to aggressive advanced disease and a better understanding of the acquired CIN tolerance mechanisms can translate into new tumour classifications, biomarker development and therapeutic strategies.

Therapeutic biomarkers in metastatic castration-resistant prostate cancer: does the state matter?

The treatment of metastatic castration-resistant prostate cancer (mCRPC) has been fundamentally transformed by our greater understanding of its complex biological mechanisms and its entrance into the era of precision oncology. A broad aim is to use the extreme heterogeneity of mCRPC by matching already approved or new targeted therapies to the correct tumor genotype. To achieve this, tumor DNA must be obtained, sequenced, and correctly interpreted, with individual aberrations explored for their druggability, taking into account the hierarchy of driving molecular pathways. Although tumor tissue sequencing is the gold standard, tumor tissue can be challenging to obtain, and a biopsy from one metastatic site or primary tumor may not provide an accurate representation of the current genetic underpinning. Sequencing of circulating tumor DNA (ctDNA) might catalyze precision oncology in mCRPC, as it enables real-time observation of genomic changes in tumors and allows for monitoring of treatment response and identification of resistance mechanisms. Moreover, ctDNA can be used to identify mutations that may not be detected in solitary metastatic lesions and can provide a more in-depth understanding of inter- and intra-tumor heterogeneity. Finally, ctDNA abundance can serve as a prognostic biomarker in patients with mCRPC.The androgen receptor (AR)-axis is a well-established therapeutical target for prostate cancer, and through ctDNA sequencing, insights have been obtained in (temporal) resistance mechanisms that develop through castration resistance. New third-generation AR-axis inhibitors are being developed to overcome some of these resistance mechanisms. The druggability of defects in the DNA damage repair machinery has impacted the treatment landscape of mCRPC in recent years. For patients with deleterious gene aberrations in genes linked to homologous recombination, particularly BRCA1 or BRCA2, PARP inhibitors have shown efficacy compared to the standard of care armamentarium, but platinum-based chemotherapy may be equally effective. A hierarchy exists in genes associated with homologous recombination, where, besides the canonical genes in this pathway, not every other gene aberration predicts the same likelihood of response. Moreover, evidence is emerging on cross-resistance between therapies such as PARP inhibitors, platinum-based chemotherapy and even radioligand therapy that target this genotype. Mismatch repair-deficient patients can experience a beneficial response to immune checkpoint inhibitors. Activation of other cellular signaling pathways such as PI3K, cell cycle, and MAPK have shown limited success with monotherapy, but there is potential in co-targeting these pathways with combination therapy, either already witnessed or anticipated. This review outlines precision medicine in mCRPC, zooming in on the role of ctDNA, to identify genomic biomarkers that may be used to tailor molecularly targeted therapies. The most common druggable pathways and outcomes of therapies matched to these pathways are discussed.

Diagnosis and management of neuroendocrine prostate cancer

BACKGROUND

Although most patients with prostate cancer (PC) respond to initial androgen deprivation therapy (ADT), castration-resistant disease invariably develops. Progression to treatment-emergent neuroendocrine PC (t-NEPC) represents a unique mechanism of resistance to androgen receptor (AR)-targeted therapy in which lineage plasticity and neuroendocrine differentiation induce a phenotypic switch from an AR-driven adenocarcinoma to an AR-independent NEPC. t-NEPC is characterized by an aggressive clinical course, increased resistance to AR-targeted therapies, and a poor overall prognosis.

METHODS

This review provides an overview of our current knowledge of NEPC, with a focus on the unmet needs, diagnosis, and clinical management of t-NEPC.

RESULTS

Evidence extrapolated from the literature on small cell lung cancer or data from metastatic castration-resistant PC (mCRPC) cohorts enriched for t-NEPC suggests an increased sensitivity to platinum-based chemotherapy. However, optimal strategies for managing t-NEPC have not been established, and prospective clinical trial data are limited. Intertumoral heterogeneity within a given patient, as well as the lack of robust molecular or clinical biomarkers for early detection, often lead to delays in diagnosis and prolonged treatment with suboptimal strategies (i.e., conventional chemohormonal therapies for mCRPC), which may further contribute to poor outcomes.

CONCLUSIONS

Recent advances in genomic and molecular classification of NEPC and the development of novel biomarkers may facilitate an early diagnosis, help to identify promising therapeutic targets, and improve the selection of patients most likely to benefit from NEPC-targeted therapies.

Yin Yang 1 promotes the neuroendocrine differentiation of prostate cancer cells via the non-canonical WNT pathway (FYN/STAT3)

BACKGROUND

A growing number of studies have shown that Yin Yang 1 (YY1) promotes the development of multiple tumours. The purpose of the current study was to determine the mechanism by which YY1 mediates neuroendocrine differentiation of prostate cancer (NEPC) cells undergoing cellular plasticity.

METHODS

Using the Cancer Genome Atlas and Gene Expression Omnibus (GEO) databases, we bioinformatically analyzed YY1 expression in prostate cancer (PCa). Aberrant YY1 expression was validated in different PCa tissues and cell lines via quantitative reverse transcription polymerase chain reaction, western blotting, and immunohistochemistry. In vivo and in vitro functional assays verified the oncogenicity of YY1 in PCa. Further functional assays showed that ectopic expression of YY1 promoted cellular plasticity in PCa cells via epithelial-mesenchymal transition induction and neuroendocrine differentiation.

RESULTS

Androgen deprivation therapy induced a decrease in YY1 protein ubiquitination, enhanced its stability, and thus enhanced the transcriptional activity of FZD8. Castration enhanced FZD8 binding to Wnt9A and mediated cellular plasticity by activating the non-canonical Wnt (FZD8/FYN/STAT3) pathway.

CONCLUSIONS

We identified YY1 as a novel dysregulated transcription factor that plays an important role in NEPC progression in this study. We believe that an in-depth investigation of the mechanism underlying YY1-mediated disease may lead to improved NEPC therapies.

Targeting Key Players of Neuroendocrine Differentiation in Prostate Cancer

Neuroendocrine prostate cancer (NEPC) is a highly aggressive subtype of prostate cancer (PC) that commonly emerges through a transdifferentiation process from prostate adenocarcinoma and evades conventional therapies. Extensive molecular research has revealed factors that drive lineage plasticity, uncovering novel therapeutic targets to be explored. A diverse array of targeting agents is currently under evaluation in pre-clinical and clinical studies with promising results in suppressing or reversing the neuroendocrine phenotype and inhibiting tumor growth and metastasis. This new knowledge has the potential to contribute to the development of novel therapeutic approaches that may enhance the clinical management and prognosis of this lethal disease. In the present review, we discuss molecular players involved in the neuroendocrine phenotype, and we explore therapeutic strategies that are currently under investigation for NEPC.

Small-Cell Carcinoma of the Prostate - Challenges of Diagnosis and Treatment: A Next of Kin and Physician Perspective Piece

This article was co-authored by a patient's relative describing their experiences of receiving a diagnosis and subsequent clinical management of a rare form of prostate cancer, neuroendocrine prostate cancer (NEPC). The difficulty of receiving this diagnosis, particularly as this was terminal with no options for systemic treatment, and experiences throughout this process are detailed. The relative's questions regarding the care of her partner, NEPC and clinical management are answered. The treating physician's perspective regarding clinical management is enclosed. Prostate cancer remains one of the most common cancer diagnoses, with small-cell carcinoma (SCC) of the prostate representing 0.5-2% of these. Prostatic SCC frequently develops in patients previously treated for prostate adenocarcinoma, more rarely arising de novo. Diagnosis and management present clinical challenges owing to its rarity, frequently aggressive disease course, lack of specific diagnostic and monitoring biomarkers, and treatment limitations. Current pathophysiological understanding of prostatic SCC, genomics and contemporary and evolving treatment options in addition to current guidelines are discussed. Written principally from the patient's relatives and physician experience with discussion of current evidence, diagnostic and treatment options, we hope this piece is informative for both patients and healthcare professionals alike.

Genetic and epigenetic features of neuroendocrine prostate cancer and their emerging applications

Prostate cancer is the second most prevalent cancer in men globally. De novo neuroendocrine prostate cancer (NEPC) is uncommon at initial diagnosis, however, (treatment-induced) t-NEPC emerges in up to 25% of prostate adenocarcinoma (PRAD) cases treated with androgen deprivation, carrying a drastically poor prognosis. The transition from PRAD to t-NEPC is underpinned by several key genetic mutations; TP53, RB1, and MYCN are the main genes implicated, bearing similarities to other neuroendocrine tumours. A broad range of epigenetic alterations, such as aberrations in DNA methylation, histone post-translational modifications, and non-coding RNAs, may drive lineage plasticity from PRAD to t-NEPC. The clinical diagnosis of NEPC is hampered by a lack of accessible biomarkers; recent advances in liquid biopsy techniques assessing circulating tumour cells and ctDNA in NEPC suggest that the advent of non-invasive means of monitoring progression to NEPC is on the horizon. Such techniques are vital for NEPC management; diagnosis of t-NEPC is crucial for implementing effective treatment, and precision medicine will be integral to providing the best outcomes for patients.

Perioperative change of circulating tumor cells in cytoreductive radical prostatectomy for oligometastatic hormone-sensitive prostate cancer: the preliminary safety evidence from long-term oncologic outcomes

Surgical manipulation has a risk of triggering the shedding of circulating tumor cells (CTCs) in patients with malignancies, However, perioperative change of circulating tumor cells in cytoreductive radical prostatectomy (CRP) for patients with oligometastatic hormone-sensitive prostate cancer (omHSPC) has not yet been well documented. This study aimed to assess whether CRP is a safe procedure for patients with omHSPC by monitoring the perioperative change of CTCs and investigating its impact on long-term oncologic outcomes. We have observed a significant decrease between the median CTC counts before and after surgery (6 vs. 4, p = 0.026). Comparing preoperative and postoperative CTC levels, seven patients increased (CTC increase group), one did not change and nineteen decreased (CTC non-increase group). PSA response rates in CTC increase group were lower than those in CTC non-increase group (73.0% vs 99.8%, p = 0.162), and nadir PSA was higher in CTC increase group (0.043 vs 0.003, p = 0.072). The CTC increase was positively correlated with the nadir PSA (r = 0.386, p = 0.047). The median follow-up period was 71.6 months, we found that there was no significant difference in clinical-pathological, operative variables or long-term oncologic outcomes between perioperative CTC increase and non-increase groups. In the entire cohort, the CTC level significantly decreased after surgery. There was no significant differences in long-term oncologic outcomes between the CTC increase and non-increase groups, implying that CRP potentially represents a safe procedure for the treatment of patients with omHSPC. The results need to be confirmed in a prospective large-scale clinical trial.

Addressing the need for more therapeutic options in neuroendocrine prostate cancer

INTRODUCTION

Neuroendocrine prostate cancer (NEPC) is an aggressive form of prostate cancer frequently seen after prolonged treatment of castration resistant prostate cancer (CRPC). NEPC has become increasingly prevalent over the last 20 years, with a poor prognosis caused by a late diagnosis and limited treatment options. Recent advances in PET/CT imaging and targeted radioimmunotherapy are promising, but more research into additional treatment options is needed.

AREAS COVERED

The aim of this review is to analyze the current imaging and treatment options for NEPC, and to highlight future potential treatment strategies. A Pubmed search for 'Neuroendocrine Prostate Cancer' was performed and relevant articles were reviewed.

EXPERT OPINION

The recent FDA approval and success of 177 PSMA Lutetium in CRPC is promising, as 177 Lutetium could potentially be paired with a NEPC specific biomarker for targeted therapy. Recent laboratory studies pairing DLL3, which is overexpressed in NEPC, with 177 Lutetium and new PET agents have showed good efficacy in identifying and treating NEPC. The success of future development of NEPC therapies may depend on the availability of 177 Lutetium, as current supplies are limited. Further research into additional imaging and treatment options for NEPC is warranted.

A Theranostic Small-Molecule Prodrug Conjugate for Neuroendocrine Prostate Cancer

After androgen deprivation therapy, a significant number of prostate cancer cases progress with a therapy-resistant neuroendocrine phenotype (NEPC). This represents a challenge for diagnosis and treatment. Based on our previously reported design of theranostic small-molecule prodrug conjugates (T-SMPDCs), herein we report a T-SMPDC tailored for targeted positron emission tomography (PET) imaging and chemotherapy of NEPC. The T-SMPDC is built upon a triazine core (TZ) to present three functionalities: (1) a chelating moiety (DOTA: 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) for PET imaging when labeled with 68Ga (t1/2 = 68 min) or other relevant radiometals; (2) an octreotide (Octr) that targets the somatostatin receptor 2 (SSTR2), which is overexpressed in the innervated tumor microenvironment (TME); and (3) fingolimod, FTY720-an antagonist of sphingosine kinase 1 that is an intracellular enzyme upregulated in NEPC. Polyethylene glycol (PEG) chains were incorporated via conventional conjugation methods or a click chemistry reaction forming a 1,4-disubstituted 1,2,3-triazole (Trz) linkage for the optimization of in vivo kinetics as necessary. The T-SMPDC, DOTA-PEG3-TZ(PEG4-Octr)-PEG2-Trz-PEG3-Val-Cit-pABOC-FTY720 (PEGn: PEG with n repeating ethyleneoxy units (n = 2, 3, or 4); Val: valine; Cit: citrulline; pABOC: p-amino-benzyloxycarbonyl), showed selective SSTR2 binding and mediated internalization of the molecule in SSTR2 high cells. Release of FTY720 was observed when the T-SMPDC was exposed to cathepsin B, and the released FTY720 exerted cytotoxicity in cells. In vivo PET imaging showed significantly higher accumulation (2.1 ± 0.3 %ID/g; p = 0.02) of [68Ga]Ga-DOTA-PEG3-TZ(PEG4-Octr)-PEG2-Trz-PEG3-Val-Cit-pABOC-FTY720 in SSTR2high prostate cancer xenografts than in the SSTR2low xenografts (1.5 ± 0.4 %ID/g) at 13 min post-injection (p.i.) with a rapid excretion through the kidneys. Taken together, these proof-of-concept results validate the design concept of the T-SMPDC, which may hold a great potential for targeted diagnosis and therapy of NEPC.

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).

Liquid biopsy-based targeted gene screening highlights tumor cell subtypes in patients with advanced prostate cancer

Prostate cancer (PCa) clinical heterogeneity underscores tumor heterogeneity, which may be best defined by cell subtypes. To test if cell subtypes contributing to progression can be assessed noninvasively, we investigated whether 14 genes representing luminal, neuroendocrine, and stem cells are detectable in whole blood RNA of patients with advanced PCa. For each gene, reverse transcription quantitative polymerase chain reaction assays were first validated using RNA from PCa cell lines, and their traceability in blood was assessed in cell spiking experiments. These were next tested in blood RNA of 40 advanced PCa cases and 40 healthy controls. Expression in controls, which was low or negative, was used to define stringent thresholds for gene overexpression in patients to account for normal variation in white blood cells. Thirty-five of 40 patients overexpressed at least one gene. Patients with more genes overexpressed had a higher risk of death (hazard ratio 1.42, range 1.12-1.77). Progression on androgen receptor inhibitors was associated with overexpression of stem (odds ratio [OR] 7.74, range 1.68-35.61) and neuroendocrine (OR 13.10, range 1.24-142.34) genes, while luminal genes were associated with taxanes (OR 2.7, range 1.07-6.82). Analyses in PCa transcriptomic datasets revealed that this gene panel was most prominent in metastases of advanced disease, with diversity among patients. Collectively, these findings support the contribution of the prostate cell subtypes to disease progression. Cell-subtype specific genes are traceable in blood RNA of patients with advanced PCa and are associated with clinically relevant end points. This opens the door to minimally invasive liquid biopsies for better management of this deadly disease.

MYCN Impact on High-Risk Neuroblastoma: From Diagnosis and Prognosis to Targeted Treatment

Simple Summary

Neuroblastoma is one of the most diffuse and the deadliest cancer in children. While many advances have been made in the last few decades to improve patients’ outcome, high-risk neuroblastoma (HR-NB) still shows a very aggressive pattern of development and poor prognosis, with only a 50% chance of 5-year survival. Moreover, while many factors contribute to defining the high-risk condition, MYCN status is well established as the major element in pathology disclosure. The aim of this review is to describe the current knowledge in the diagnosis, prognosis and therapeutic approaches of HR-NB, particularly in relation to MYCN. The review highlights how MYCN influences the HR-NB scenario and the new therapeutic approaches that are currently proposed to target it, in consideration of MYCN as a highly relevant target for HR-NB patient management.

Abstract

Among childhood cancers, neuroblastoma is the most diffuse solid tumor and the deadliest in children. While to date, the pathology has become progressively manageable with a significant increase in 5-year survival for its less aggressive form, high-risk neuroblastoma (HR-NB) remains a major issue with poor outcome and little survivability of patients. The staging system has also been improved to better fit patient needs and to administer therapies in a more focused manner in consideration of pathology features. New and improved therapies have been developed; nevertheless, low efficacy and high toxicity remain a staple feature of current high-risk neuroblastoma treatment. For this reason, more specific procedures are required, and new therapeutic targets are also needed for a precise medicine approach. In this scenario, MYCN is certainly one of the most interesting targets. Indeed, MYCN is one of the most relevant hallmarks of HR-NB, and many studies has been carried out in recent years to discover potent and specific inhibitors to block its activities and any related oncogenic function. N-Myc protein has been considered an undruggable target for a long time. Thus, many new indirect and direct approaches have been discovered and preclinically evaluated for the interaction with MYCN and its pathways; a few of the most promising approaches are nearing clinical application for the investigation in HR-NB.

A Systematic Review of Circulating Tumor Cells Clinical Application in Prostate Cancer Diagnosis

Simple Summary

Cell-dependent and cell-independent information drawn from the blood stream were merged into the attractive term “liquid biopsy” and tentatively applied to most segments of cancer management: detection, risk-stratification, personalization of care and follow-up. However, the robust science behind liquid biopsies has not been widely used, thereby remaining a latent and possibly undervalued instrument. Here, we conducted a systematic review of CTCs in prostate cancer management to summarize their use in clinical practice.

Abstract

The purpose of the review is to summarize the recent data on circulating tumor cells (CTC) use in clinical practice. We performed a systematic literature search using two databases (Medline and Scopus) over the past five years and the following terms: (CTC OR “circulating tumor cells” OR “liquid biopsy”) AND prostate. The primary outcome was CTC predictive value for prostate cancer (PC) progression and survival. The secondary outcomes were the CTC predictive value for therapy response and the results of CTC detection depending on the assessment method. In metastatic PC, the CTC count showed itself to be a prognostic marker in terms of clinically important features, namely survival rates and response to treatment. CTC concentration was significantly associated with the overall survival and progression-free survival rates. A strong association between the overall survival or progression-free survival rate and CTC concentration could be observed. Variant-7 androgen receptors-positive (AR-V7-positive) patients showed a poor response to androgen receptor signaling (ARS) inhibitors, but this did not compromise their response to taxanes. In localized PC, only positive Cluster of Differentiantion 82 protein (CD82+) correlated with a higher survival rate. CTC count and AR-V7 expression showed itself to be a valuable biomarker for survival in metastatic PC and response to ARS-inhibitors. CTC diagnostic performance for localized PC or for screening and early detection is not high enough to show additional value over the other biomarkers.

The Role of Epigenetic Change in Therapy-Induced Neuroendocrine Prostate Cancer Lineage Plasticity

The androgen receptor (AR) signaling pathway is critical for growth and differentiation of prostate cancer cells. For that reason, androgen deprivation therapy with medical or surgical castration is the principal treatment for metastatic prostate cancer. More recently, new potent AR signaling inhibitors (ARSIs) have been developed. These drugs improve survival for men with metastatic castration-resistant prostate cancer (CRPC), the lethal form of the disease. However, ARSI resistance is nearly universal. One recently appreciated resistance mechanism is lineage plasticity or switch from an AR-driven, luminal differentiation program to an alternate differentiation program. Importantly, lineage plasticity appears to be increasing in incidence in the era of new ARSIs, strongly implicating AR suppression in this process. Lineage plasticity and shift from AR-driven tumors occur on a continuum, ranging from AR-expressing tumors with low AR activity to AR-null tumors that have activation of alternate differentiation programs versus the canonical luminal program found in AR-driven tumors. In many cases, AR loss coincides with the activation of a neuronal program, most commonly exemplified as therapy-induced neuroendocrine prostate cancer (t-NEPC). While genetic events clearly contribute to prostate cancer lineage plasticity, it is also clear that epigenetic events-including chromatin modifications and DNA methylation-play a major role. Many epigenetic factors are now targetable with drugs, establishing the importance of clarifying critical epigenetic factors that promote lineage plasticity. Furthermore, epigenetic marks are readily measurable, demonstrating the importance of clarifying which measurements will help to identify tumors that have undergone or are at risk of undergoing lineage plasticity. In this review, we discuss the role of AR pathway loss and activation of a neuronal differentiation program as key contributors to t-NEPC lineage plasticity. We also discuss new epigenetic therapeutic strategies to reverse lineage plasticity, including those that have recently entered clinical trials.

Circulating tumor cells: A step toward precision medicine in hepatocellular carcinoma

Serum alpha-fetoprotein and radiologic imaging are the most commonly used tests for early diagnosis and dynamic monitoring of treatment response in hepatocellular carcinoma (HCC). However, the accuracy of these tests is limited, and they may not reflect the underlying biology of the tumor. Thus, developing highly accurate novel HCC biomarkers reflecting tumor biology is a clinically unmet need. Circulating tumor cells (CTCs) have long been proposed as a noninvasive biomarker in clinical oncology. Most CTC assays utilize immunoaffinity-based, size-based, and/or enrichment-free mechanisms followed by immunocytochemical staining to characterize CTCs. The prognostic value of HCC CTC enumeration has been extensively validated. Subsets of CTCs expressing mesenchymal markers are also reported to have clinical significance. In addition, researchers have been devoting their efforts to molecular characterizations of CTCs (e.g. genetics and transcriptomics) as molecular profiling can offer a more accurate readout and provide biological insights. As new molecular profiling techniques, such as digital polymerase chain reaction, are developed to detect minimal amounts of DNA/RNA, several research groups have established HCC CTC digital scoring systems to quantify clinically relevant gene panels. Given the versatility of CTCs to provide intact molecular and functional data that reflects the underlying tumor, CTCs have great potential as a noninvasive biomarker in HCC. Large-scale, prospective studies for HCC CTCs with a standardized protocol are necessary for successful clinical translation.

Blood-based liquid biopsies for prostate cancer: clinical opportunities and challenges

Liquid biopsy has been established as a powerful, minimally invasive, tool to detect clinically actionable aberrations across numerous cancer types in real-time. With the development of new therapeutic agents in prostate cancer (PC) including DNA repair targeted therapies, this is especially attractive. However, there is unclarity on how best to screen for PC, improve risk stratification and ultimately how to treat advanced disease. Therefore, there is an urgent need to develop better biomarkers to help guide oncologists' decisions in these settings. Circulating tumour cells (CTCs), exosomes and cell-free DNA/RNA (cfDNA/cfRNA) analysis, including epigenetic features such as methylation, have all shown potential in prognostication, treatment response assessment and detection of emerging mechanisms of resistance. However, there are still challenges to overcome prior to implementing liquid biopsies in routine clinical practice such as preanalytical considerations including blood collection and storage, the cost of CTC isolation and enrichment, low-circulating tumour content as a limitation for genomic analysis and how to better interpret the sequencing data generated. In this review, we describe an overview of the up-to-date clinical opportunities in the management of PC through blood-based liquid biopsies and the next steps for its implementation in personalised treatment guidance.

Circulating tumor cells in neuroblastoma: Current status and future perspectives

Neuroblastoma is the most common extracranial solid tumor in children, accounting for 10% to 20% of deaths of pediatric malignancies. Due to the poor prognosis and significant biological heterogeneity of neuroblastoma, it is essential to develop personalized therapeutics and monitor treatment response. Circulating tumor cells (CTCs), as one of the important analytes for liquid biopsy, could facilitate response assessment and outcome prediction for patients in a non-invasive way. Several methods and platforms have been used for the enrichment and detection of CTCs. The enumeration of CTCs counts and evaluation of tumor-specific mRNA transcript levels could provide prognostic information at diagnosis, during or after chemotherapy, and during the process of disease progression. So far, studies into neuroblastoma CTCs are only in the preliminary stages. The quality-controlled large prospective cohort studies are needed to evaluate the clinical significance and statistical rigor of CTC detection methods. Moreover, there remains a lot to be explored and investigated in genotyping characterization of neuroblastoma (NB) CTCs and construction of in-vitro or in-vivo functional models. CTCs and circulating tumor DNA (ctDNA) analysis will be complementary in understanding tumor heterogeneity and evolution over the course of therapy for patients with NB in the future.

Dynamic expression of Schlafen 11 (SLFN11) in circulating tumour cells as a liquid biomarker in small cell lung cancer

INTRODUCTION

Small cell lung cancer (SCLC) is an aggressive malignancy with no established biomarkers. Schlafen 11(SLFN11), a DNA/RNA helicase that sensitises cancer cells to DNA-damaging agents, has emerged as a promising predictive biomarker for several drug classes including platinum and PARP inhibitors. Detection of SLFN11 in circulating tumour cells (CTCs) may provide a valuable alternative to tissue sampling.

METHODS

SLFN11 expression was evaluated in tumour samples and characterised in circulating tumour cells (CTC) longitudinally to determine its potential role as a biomarker of response.

RESULTS

Among 196 SCLC tumours, 51% expressed SLFN11 by IHC. In addition, 20/29 extra-thoracic high-grade neuroendocrine tumours expressed SLFN11 expression. In 64 blood samples from 42 SCLC patients, 83% (53/64) of samples had detectable CTCs, and SLFN11-positive CTCs were detected in 55% (29/53). Patients actively receiving platinum treatment had the lowest number of CTCs and a lower percentage of SLFN11-positive CTCs (p = 0.014). Analysis from patients with longitudinal samples suggest a decrease in CTC number and in SLFN11 expression that correlates with clinical response.

CONCLUSIONS

SLFN11 levels can be monitored in CTCs from SCLC patients using non-invasive liquid biopsies. The ability to detect SLFN11 in CTCs from SCLC patients adds a valuable tool for the detection and longitudinal monitoring of this promising biomarker.

Proteomic and Transcriptomic Profiling Reveals Mitochondrial Oxidative Phosphorylation as Therapeutic Vulnerability in Androgen Receptor Pathway Active Prostate Tumors

Simple Summary

Metastatic prostate cancer (PC) is the second leading cause of cancer deaths in males. The lack of preclinical models and molecular characterization for advanced stage PC is a key barrier in understanding the aggressive subsets androgen receptor (AR) pathway active or AR-null castration-resistant prostate cancers (CRPC). Our study aimed to assess the potential of patient-derived xenograft (PDX) models and an approach integrating proteomic and transcriptomic techniques to explore the underlying drivers of metastatic PC. Transcriptomic and proteomic profiling of 42 PDX prostate tumors uncovered both previously established and unexpected molecular features of aggressive PC subsets. Of these, we confirmed the functional role of mitochondrial metabolism in AR-positive CRPC.

Abstract

Metastatic prostate cancer (PC) is the second leading cause of cancer deaths in males and has limited therapeutic options. The lack of preclinical models for advanced stage PC represents one of the primary barriers in understanding the key genetic drivers of aggressive subsets, including androgen receptor (AR) pathway active and AR-null castration-resistant prostate cancers (CRPC). In our studies, we described a series of LuCaP patient-derived xenograft (PDX) models representing the major genomic and phenotypic features of human disease. To fully exploit the potential of these preclinical models, we carried out a comprehensive transcriptomic and proteomic profiling of 42 LuCaP PDX prostate tumors. The collected proteomic data (~6000 data points) based on 71 antibodies revealed many of the previously known molecular markers associated with AR-positive and AR-null CRPC. Genomic analysis indicated subtype-specific activation of pathways such as Wnt/beta-catenin signaling, mTOR, and oxidative phosphorylation for AR-positive CRPC and upregulation of carbohydrate metabolism and glucose metabolism for AR-null CRPC. Of these, we functionally confirmed the role of mitochondrial metabolism in AR-positive CRPC cell lines. Our data highlight how the integration of transcriptomic and proteomic approaches and PDX systems as preclinical models can potentially map the connectivity of poorly understood signaling pathways in metastatic prostate cancer.

Validation of SV2A-Targeted PET Imaging for Noninvasive Assessment of Neuroendocrine Differentiation in Prostate Cancer

Neuroendocrine prostate cancer (NEPC) is an aggressive and lethal variant of prostate cancer (PCa), and it remains a diagnostic challenge. Herein we report our findings of using synaptic vesicle glycoprotein 2 isoform A (SV2A) as a promising marker for positron emission tomography (PET) imaging of neuroendocrine differentiation (NED). The bioinformatic analyses revealed an amplified SV2A gene expression in clinical samples of NEPC versus castration-resistant PCa with adenocarcinoma characteristics (CRPC-Adeno). Importantly, significantly upregulated SV2A protein levels were found in both NEPC cell lines and tumor tissues. PET imaging studies were carried out in NEPC xenograft models with ¹⁸F-SynVesT-1. Although ¹⁸F-SynVesT-1 is not a cancer imaging agent, it showed a significant uptake level in the SV2A⁺ tumor (NCI-H660: 0.70 ± 0.14 %ID/g at 50–60 min p.i.). The SV2A blockade resulted in a significant reduction of tumor uptake (0.25 ± 0.03 %ID/g, p = 0.025), indicating the desired SV2A imaging specificity. Moreover, the comparative PET imaging study showed that the DU145 tumors could be clearly visualized by ¹⁸F-SynVesT-1 but not ⁶⁸Ga-PSMA-11 nor ⁶⁸Ga-DOTATATE, further validating the role of SV2A-targeted imaging for noninvasive assessment of NED in PCa. In conclusion, we demonstrated that SV2A, highly expressed in NEPC, can serve as a promising target for noninvasive imaging evaluation of NED.

Liquid biopsy in prostate cancer: current status and future challenges of clinical application

PURPOSE

Liquid biopsy refers to the detection and analysis of the components from biological fluids non-invasively, including circulating tumor cells, nucleic acids, and extracellular vesicles (EVs). It is necessary to review the clinical value of liquid biopsy assays in PC and explore its potential application.

MATERIALS AND METHODS

We systematically reviewed of PubMed was performed to identify relevant literature on potential clinical applications of circulating tumor cells, circulating nucleic acids, and EVs in prostate cancer (PC).

RESULTS

Liquid biopsy has emerged as a powerful tool to elucidate dynamic genomic, transcriptomic, and epigenomic tumor profiling in real-time. Here, the potential clinical applications of liquid biopsy include early detection, prognosis of survival, assessment of treatment response, and mechanisms of drug resistance in PC.

CONCLUSIONS

Liquid biopsy provides great value in diagnosis, prognosis, and treatment response in PC. Characterization of liquid biopsy components provides benefits both to unravel underlying resistance mechanisms and to exploit novel clinically actionable targets in PC. In addition, we suggest that analysis of multiparametric liquid biopsies should be analyzed comprehensively, assisting in monitoring tumor characteristics in real-time, guiding therapeutic selection, and early therapeutic switching during disease progression.

Imaging of Neuroendocrine Prostatic Carcinoma

Neuroendocrine prostate cancer (NEPC) is an aggressive subtype of prostate cancer that typically has a high metastatic potential and poor prognosis in comparison to the adenocarcinoma subtype. Although it can arise de novo, NEPC much more commonly occurs as a mechanism of treatment resistance during therapy for conventional prostatic adenocarcinoma, the latter is also termed as castration-resistant prostate cancer (CRPC). The incidence of NEPC increases after hormonal therapy and they represent a challenge, both in the radiological and pathological diagnosis, as well as in the clinical management. This article provides a comprehensive imaging review of prostatic neuroendocrine tumors.

Case Report: Systemic Treatment and Serial Genomic Sequencing of Metastatic Prostate Adenocarcinoma Progressing to Small Cell Carcinoma

Small cell carcinoma (SCC)/neuroendocrine prostate cancer (NEPC) is a rare and highly aggressive subtype of prostate cancer associated with an AR(androgen receptor)-null phenotype and visceral metastases. This study presents a 44-year-old man originally diagnosed with metastatic hormone-sensitive prostatic adenocarcinoma. After 6-month androgen deprivation therapy (ADT) combined with docetaxel, the patient developed paraplegia. Laminectomy was performed, and a thoracic vertebral biopsy revealed neuroendocrine differentiation and mixed adenocarcinoma. The patient developed liver metastases and experienced stable disease for 4 months following etoposide combined with cisplatin and pembrolizumab. Seminal vesicle biopsy after chemotherapy revealed small-cell cancer. The prostate biopsy specimen also indicated pure SCC. We witnessed the dynamic evolution from pure adenocarcinoma to fully differentiated SCC, leading to obstruction and death. In addition, whole-exome sequencing was performed on both biopsy specimens of the thoracic vertebra at the beginning of castration resistance and that of seminal vesicle after multiple lines of treatment failure. Utilizing phylogenetic reconstruction, we observed that both samples shared a common ancestor clone harboring aberrations in the TP53, RB1, and NF2 genes. We also discovered that driver events in the private subclones of both samples, such as alterations in CDC27 and RUNX1, might have played a significant role in tumor progression or even neuroendocrine differentiation. Tumor biopsy and IHC assessment must be repeated at different stages of progression, because of intrapatient spatial and temporal heterogeneity of adenocarcinoma versus SCC/NEPC. Although, typical treatments including ADT, docetaxel, etoposide, cisplatin, and pembrolizumab provided temporary response, the patient still had a poor prognosis.

Clinical considerations for the management of androgen indifferent prostate cancer

BACKGROUND

Many systemic therapies for advanced prostate cancer work by disrupting androgen receptor signaling. Androgen indifferent prostate cancer (AIPC) variants, including aggressive variant prostate cancer (AVPC), neuroendocrine prostate cancer (NEPC), and double-negative prostate cancer (DNPC), are increasingly common and often overlapping resistance phenotypes following treatment with androgen receptor signaling inhibitors in men with metastatic castration-resistant prostate cancer and are associated with poor outcomes. Understanding the underlying biology and identifying effective therapies for AIPC is paramount for improving survival for men with prostate cancer.

METHODS

In this review, we summarize the current knowledge on AIPC variants, including our current understanding of the clinical, morphologic, and molecular features as well as current therapeutic approaches. We also explore emerging therapies and biomarkers aimed at improving outcomes for men with AIPC.

RESULTS AND CONCLUSIONS

Establishing consensus definitions, developing novel biomarkers for early and accurate detection, further characterization of molecular drivers of each phenotype, and developing effective therapies will be critical to improving outcomes for men with AIPC. Significant progress has been made toward defining the clinical and molecular characteristics of AVPC, NEPC, and DNPC. Novel diagnostic approaches, including cell-free DNA, circulating tumor cells, and molecular imaging are promising tools for detecting AIPC in clinical practice. Building on previous treatment advances, several clinical trials are underway evaluating novel therapeutic approaches in patients with AIPC informed by an understanding of variant-specific biology. In this review, we discuss how these recent and ongoing studies will help to improve diagnosis, prognosis, and therapy for men with AIPC.

Blocking GRP/GRP-R signaling decreases expression of androgen receptor splice variants and inhibits tumor growth in castration-resistant prostate cancer

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The results of our study strongly indicate that blocking GRP/GRP-R signaling by targeting GRP-R is sufficient to inhibit ARVs expression. In addition, the combination of blocking GRP/GRP-R signaling (targeting ARVs) and anti-androgens (targeting AR-FL) is a potential new therapeutic approach for treatment of CRPC and therapy-induced tNEPC.

Clinical management of castration-resistant prostate cancer (CRPC) resulting from androgen deprivation therapy (ADT) remains challenging. Many studies indicate that androgen receptor splice variants (ARVs) play a critical role in the development of CRPC, including resistance to the new generation of inhibitors of androgen receptor (AR) action. ARVs are constitutively active and lack the ligand-binding domain (LBD), thereby allowing prostate cancer (PC) to maintain AR activity despite therapies that target the AR (full-length AR; AR-FL). Previously, we have reported that long-term ADT increases the neuroendocrine (NE) hormone – Gastrin Releasing Peptide (GRP) and its receptor (GRP-R) expression in PC cells. Further, we demonstrated that activation of GRP/GRP-R signaling increases ARVs expression by activating NF-κB signaling, thereby promoting cancer progression to CRPC. Most importantly, as a cell surface protein, GRP-R is easily targeted by drugs to block GRP/GRP-R signaling. In this study, we tested if blocking GRP/GRP-R signaling by targeting GRP-R using GRP-R antagonist is sufficient to control CRPC progression. Our studies show that blocking GRP/GRP-R signaling by targeting GRP-R using RC-3095, a selective GRP-R antagonist, efficiently inhibits NF-κB activity and ARVs (AR-V7) expression in CRPC and therapy-induced NEPC (tNEPC) cells. In addition, blocking of GRP/GRP-R signaling by targeting GRP-R can sensitize CRPC cells to anti-androgen treatment (such as MDV3100). Further, preclinical animal studies indicate combination of GRP-R antagonist (targeting ARVs) with anti-androgen (targeting AR-FL) is sufficient to inhibit CRPC and tNEPC tumor growth.

Circulating tumor cell heterogeneity in neuroendocrine prostate cancer by single cell copy number analysis

Neuroendocrine prostate cancer is an aggressive variant of prostate cancer that may arise de novo or develop from pre-existing prostate adenocarcinoma as a mechanism of treatment resistance. The combined loss of tumor suppressors RB1, TP53, and PTEN are frequent in NEPC but also present in a subset of prostate adenocarcinomas. Most clinical and preclinical studies support a trans-differentiation process, whereby NEPC arises clonally from a prostate adenocarcinoma precursor during the course of treatment resistance. Here we highlight a case of NEPC with significant intra-patient heterogeneity observed across metastases. We further demonstrate how single-cell genomic analysis of circulating tumor cells combined with a phenotypic evaluation of cellular diversity can be considered as a window into tumor heterogeneity in patients with advanced prostate cancer.

Therapy considerations in neuroendocrine prostate cancer: what next?

Lineage plasticity and histologic transformation to small cell neuroendocrine prostate cancer (NEPC) is an increasingly recognized mechanism of treatment resistance in advanced prostate cancer. This is associated with aggressive clinical features and poor prognosis. Recent work has identified genomic, epigenomic, and transcriptome changes that distinguish NEPC from prostate adenocarcinoma, pointing to new mechanisms and therapeutic targets. Treatment-related NEPC arises clonally from prostate adenocarcinoma during the course of disease progression, retaining early genomic events and acquiring new molecular features that lead to tumor proliferation independent of androgen receptor activity, and ultimately demonstrating a lineage switch from a luminal prostate cancer phenotype to a small cell neuroendocrine carcinoma. Identifying the subset of prostate tumors most vulnerable to lineage plasticity and developing strategies for earlier detection and intervention for patients with NEPC may ultimately improve prognosis. Clinical trials focused on drug targeting of the lineage plasticity process and/or NEPC will require careful patient selection. Here, we review emerging targets and discuss biomarker considerations that may be informative for the design of future clinical studies.

Prospective Evaluation of Clinical Outcomes Using a Multiplex Liquid Biopsy Targeting Diverse Resistance Mechanisms in Metastatic Prostate Cancer

Nearly all men with prostate cancer treated with androgen receptor (AR) signaling inhibitors (ARSIs) develop resistance via diverse mechanisms including constitutive activation of the AR pathway, driven by AR genomic structural alterations, expression of AR splice variants (AR-Vs), or loss of AR dependence and lineage plasticity termed neuroendocrine prostate cancer. Understanding these de novo acquired ARSI resistance mechanisms is critical for optimizing therapy.

A Potent, Selective CBX2 Chromodomain Ligand and Its Cellular Activity During Prostate Cancer Neuroendocrine Differentiation

Polycomb group (PcG) proteins are epigenetic regulators that facilitate both embryonic development and cancer progression. PcG proteins form Polycomb repressive complexes 1 and 2 (PRC1 and PRC2). PRC2 trimethylates histone H3 lysine 27 (H3K27me3), a histone mark recognized by the N-terminal chromodomain (ChD) of the CBX subunit of canonical PRC1. There are five PcG CBX paralogs in humans. CBX2 in particular is upregulated in a variety of cancers, particularly in advanced prostate cancers. Using CBX2 inhibitors to understand and target CBX2 in prostate cancer is highly desirable; however, high structural similarity among the CBX ChDs has been challenging for developing selective CBX ChD inhibitors. Here, we utilize selections of focused DNA encoded libraries (DELs) for the discovery of a selective CBX2 chromodomain probe, SW2_152F. SW2_152F binds to CBX2 ChD with a Kd of 80 nM and displays 24-1000-fold selectivity for CBX2 ChD over other CBX paralogs in vitro. SW2_152F is cell permeable, selectively inhibits CBX2 chromatin binding in cells, and blocks neuroendocrine differentiation of prostate cancer cell lines in response to androgen deprivation.

Circulating Tumor Cell Chromosomal Instability and Neuroendocrine Phenotype by Immunomorphology and Poor Outcomes in Men with mCRPC Treated with Abiraterone or Enzalutamide

PURPOSE

While the detection of AR-V7 in circulating tumor cells (CTC) is associated with resistance to abiraterone or enzalutamide in men with metastatic castration-resistant prostate cancer (mCRPC), it only accounts for a minority of this resistance. Neuroendocrine (NE) differentiation or chromosomal instability (CIN) may be additional mechanisms that mediate resistance.

EXPERIMENTAL DESIGN

PROPHECY was a multicenter prospective study of men with high-risk mCRPC starting abiraterone or enzalutamide. A secondary objective was to assess Epic CTC CIN and NE phenotypes before abiraterone or enzalutamide and at progression. The proportional hazards (PH) model was used to investigate the prognostic importance of CIN and NE in predicting progression-free survival and overall survival (OS) adjusting for CTC number (CellSearch), AR-V7, prior therapy, and clinical risk score. The PH model was utilized to validate this association of NE with OS in an external dataset of patients treated similarly at Memorial Sloan Kettering Cancer Center (MSKCC; New York, NY).

RESULTS

We enrolled 118 men with mCRPC starting on abiraterone or enzalutamide; 107 were evaluable on the Epic platform. Of these, 36.4% and 8.4% were CIN positive and NE positive, respectively. CIN and NE were independently associated with worse OS [HR, 2.2; 95% confidence interval (CI), 1.2-4.0 and HR 3.8; 95% CI, 1.2-12.3, respectively] when treated with abiraterone/enzalutamide. The prognostic significance of NE positivity for worse OS was confirmed in the MSKCC dataset (n = 173; HR, 5.7; 95% CI, 2.6-12.7).

CONCLUSIONS

A high CIN and NE CTC phenotype is independently associated with worse survival in men with mCRPC treated with abiraterone/enzalutamide, warranting further prospective controlled predictive studies to inform treatment decisions.

Androgen Receptor Signaling and the Emergence of Lethal Neuroendocrine Prostate Cancer With the Treatment-Induced Suppression of the Androgen Receptor: A Literature Review

Androgen receptor signaling primarily influences both the normal growth and proliferation of the prostate gland and the development of prostatic carcinoma. While localized prostate cancers are typically managed with definitive therapies like surgery and radiotherapy, many patients have recurrences in the form of metastatic disease. Androgen deprivation therapy, by way of castration via orchiectomy or with drugs like luteinizing hormone-releasing hormone (commonly called gonadotropin-releasing hormone) agonists and luteinizing hormone-releasing hormone antagonists, is the primary mode of therapy for advanced castration-sensitive prostate cancer. Castration resistance invariably develops in these patients. Further treatment has shifted to newer anti-androgen drugs like enzalutamide or abiraterone and taxane-based chemotherapy. Prolonged inhibition of the androgen receptor signaling pathway causes androgen receptor-independent clonal evolution which leads to the development of treatment-emergent neuroendocrine prostate cancer. All prostate cancers at the initial presentation should undergo evaluation for the markers of neuroendocrine differentiation. Detection of serum biomarkers of neuroendocrine differentiation and circulating tumor cells is a prospective non-invasive method of detecting neuroendocrine transdifferentiation in patients undergoing treatment with androgen receptor pathway inhibitors. It is essential to perform a biopsy in the presence of red flags of neuroendocrine differentiation. Alisertib, an Aurora kinase inhibitor, showed promising clinical benefit in a subgroup of patients with certain molecular alterations. A thorough understanding of the molecular and clinical programming of treatment-emergent neuroendocrine prostate cancer can potentially lead to the development of drugs to prevent the development of this lethal variant of prostate cancer.

Quantitative and Qualitative Analysis of Blood-based Liquid Biopsies to Inform Clinical Decision-making in Prostate Cancer

CONTEXT

Genomic stratification can impact prostate cancer (PC) care through diagnostic, prognostic, and predictive biomarkers that aid in clinical decision-making. The temporal and spatial genomic heterogeneity of PC together with the challenges of acquiring metastatic tissue biopsies hinder implementation of tissue-based molecular profiling in routine clinical practice. Blood-based liquid biopsies are an attractive, minimally invasive alternative.

OBJECTIVE

To review the clinical value of blood-based liquid biopsy assays in PC and identify potential applications to accelerate the development of precision medicine.

EVIDENCE ACQUISITION

A systematic review of PubMed/MEDLINE was performed to identify relevant literature on blood-based circulating tumor cells (CTCs), circulating tumor DNA (ctDNA), and extracellular vesicles (EVs) in PC.

EVIDENCE SYNTHESIS

Liquid biopsy has emerged as a practical tool to profile tumor dynamics over time, elucidating features that evolve (genome, epigenome, transcriptome, and proteome) with tumor progression. Liquid biopsy tests encompass analysis of DNA, RNA, and proteins that can be detected in CTCs, ctDNA, or EVs. Blood-based liquid biopsies have demonstrated promise in the context of localized tumors (diagnostic signatures, risk stratification, and disease monitoring) and advanced disease (response/resistance biomarkers and prognostic markers).

CONCLUSIONS

Liquid biopsies have value as a source of prognostic, predictive, and response biomarkers in PC. Most clinical applications have been developed in the advanced metastatic setting, where CTC and ctDNA yields are significantly higher. However, standardization of assays and analytical/clinical validation is necessary prior to clinical implementation.

PATIENT SUMMARY

Traces of tumors can be isolated from blood samples from patients with prostate cancer either as whole cells or as DNA fragments. These traces provide information on tumor features. These minimally invasive tests can guide diagnosis and treatment selection.

Neuroendocrine Carcinoma as an Independent Prognostic Factor for Patients With Prostate Cancer: A Population-Based Study

BACKGROUND

Neuroendocrine carcinoma (NEC) is a rare and highly malignant variation of prostate adenocarcinoma. We aimed to investigate the prognostic value of NEC in prostate cancer.

METHODS

A total of 530440 patients of prostate cancer, including neuroendocrine prostate cancer (NEPC) and adenocarcinoma from 2004 to 2018 were obtained from the national Surveillance, Epidemiology, and End Results (SEER) database. Propensity score matching (PSM), multivariable Cox proportional hazard model, Kaplan-Meier method and subgroup analysis were performed in our study.

RESULTS

NEPC patients were inclined to be older at diagnosis (Median age, 69(61-77) vs. 65(59-72), P< 0.001) and had higher rates of muscle invasive disease (30.9% vs. 9.2%, P < 0.001), lymph node metastasis (32.2% vs. 2.2%, P < 0.001), and distal metastasis (45.7% vs. 3.6%, P < 0.001) compared with prostate adenocarcinoma patients. However, the proportion of NEPC patients with PSA levels higher than 4.0 ng/mL was significantly less than adenocarcinoma patients (47.3% vs. 72.9%, P<0.001). NEPC patients had a lower rate of receiving surgery treatment (28.8% vs. 43.9%, P<0.001), but they had an obviously higher rate of receiving chemotherapy (57.9% vs. 1.0%, P<0.001). A Cox regression analysis demonstrated that the NEPC patients faced a remarkably worse OS (HR = 2.78, 95% CI = 2.34-3.31, P < 0.001) and CSS (HR = 3.07, 95% CI = 2.55-3.71, P < 0.001) compared with adenocarcinoma patients after PSM. Subgroup analyses further suggested that NEPC patients obtained significantly poorer prognosis across nearly all subgroups.

CONCLUSION

The prognosis of NEPC was worse than that of adenocarcinoma among patients with prostate cancer. The histological subtype of NEC is an independent prognostic factor for patients with prostate cancer.

Neuroendocrine and Aggressive-Variant Prostate Cancer

In prostate cancer, neuroendocrine (NE) differentiation may rarely present de novo or more frequently arises following hormonal therapy in patients with castration-resistant prostate cancer (CRPC). Its distinct phenotype is characterized by an aggressive clinical course, lack of responsiveness to hormonal therapies and poor prognosis. Importantly, a subset of CRPC patients exhibits an aggressive-variant disease with very similar clinical and molecular characteristics to small-cell prostate cancer (SCPC) even though tumors do not have NE differentiation. This aggressive-variant prostate cancer (AVPC) also shares the sensitivity of SCPC to platinum-based chemotherapy albeit with short-lived clinical benefit. As optimal treatment strategies for AVPC remain elusive, currently ongoing research efforts aim to enhance our understanding of the biology of this disease entity and improve treatment outcomes for our patients. This review is an overview of our current knowledge on prostate cancer with NE differentiation and AVPC, with a focus on their clinical characteristics and management, including available as well as experimental therapeutic strategies.

Multigene model for predicting metastatic prostate cancer using circulating tumor cells by microfluidic magnetophoresis

We aimed to isolate circulating tumor cells (CTCs) using a microfluidic technique with a novel lateral magnetophoretic microseparator. Prostate cancer–specific gene expressions were evaluated using mRNA from the isolated CTCs. A CTC‐based multigene model was then developed for identifying advanced prostate cancer. Peripheral blood samples were obtained from five healthy donors and patients with localized prostate cancer (26 cases), metastatic hormone‐sensitive prostate cancer (mHSPC, 10 cases), and metastatic castration‐resistant prostate cancer (mCRPC, 28 cases). CTC recovery rate and purity (enriched CTCs/total cells) were evaluated according to cancer stage. The areas under the curves of the six gene expressions were used to evaluate whether multigene models could identify mHSPC or mCRPC. The number of CTCs and their purity increased at more advanced cancer stages. In mHSPC/mCRPC cases, the specimens had an average of 27.5 CTCs/mL blood, which was 4.2 × higher than the isolation rate for localized disease. The CTC purity increased from 2.1% for localized disease to 3.8% for mHSPC and 6.7% for mCRPC, with increased CTC expression of the genes encoding prostate‐specific antigen (PSA), prostate‐specific membrane antigen (PSMA), and cytokeratin 19 (KRT19). All disease stages exhibited expression of the genes encoding androgen receptor (AR) and epithelial cell adhesion molecule (EpCAM), although expression of the AR‐V7 variant was relatively rare. Relative to each gene alone, the multigene model had better accuracy for predicting advanced prostate cancer. Our lateral magnetophoretic microseparator can be used for identifying prostate cancer biomarkers. In addition, CTC‐based genetic signatures may guide the early diagnosis of advanced prostate cancer.

Circulating Tumor Cell Subtypes and T-cell Populations as Prognostic Biomarkers to Combination Immunotherapy in Patients with Metastatic Genitourinary Cancer

PURPOSE

Circulating tumor cells (CTC) are under investigation as a minimally invasive liquid biopsy that may improve risk stratification and treatment selection. CTCs uniquely allow for digital pathology of individual malignant cell morphology and marker expression. We compared CTC features and T-cell counts with survival endpoints in a cohort of patients with metastatic genitourinary cancer treated with combination immunotherapy.

EXPERIMENTAL DESIGN

Markers evaluated included pan-CK/CD45/PD-L1/DAPI for CTCs and CD4/CD8/Ki-67/DAPI for T cells. ANOVA was used to compare CTC burden and T-cell populations across timepoints. Differences in survival and disease progression were evaluated using the maximum log-rank test.

RESULTS

From December 2016 to January 2019, 183 samples from 81 patients were tested. CTCs were found in 75% of patients at baseline. CTC burden was associated with shorter overall survival (OS) at baseline (P = 0.022), but not on-therapy. Five morphologic subtypes were detected, and the presence of two specific subtypes with unique cellular features at baseline and on-therapy was associated with worse OS (0.9-2.3 vs. 28.2 months; P < 0.0001-0.013). Increasing CTC heterogeneity on-therapy had a trend toward worse OS (P = 0.045). PD-L1⁺ CTCs on-therapy were associated with worse OS (P < 0.01, cycle 2). Low baseline and on-therapy CD4/CD8 counts were also associated with poor OS and response category.

CONCLUSIONS

Shorter survival may be associated with high CTC counts at baseline, presence of specific CTC morphologic subtypes, PD-L1⁺ CTCs, and low %CD4/8 T cells in patients with metastatic genitourinary cancer. A future study is warranted to validate the prognostic utility of CTC heterogeneity and detection of specific CTC morphologies.

Automated enumeration and phenotypic characterization of CTCs and tdEVs in patients with metastatic castration resistant prostate cancer

Background

Although most patients with metastatic castration-resistant prostate cancer (mCRPC) initially benefit from treatment with androgen receptor signaling inhibitors (ARSi), resistance inevitably occurs. Hence, we investigated the prognostic value of automated circulating tumor cell (CTC) and tumor-derived extracellular vesicle (tdEV) enumeration and their dynamics, in patients with mCRPC in the context of the initiation of treatment with ARSi. Furthermore, we hypothesize that CTC phenotypic heterogeneity might serve as a measurable biomarker under these circumstances.

Methods

Using an image analysis tool, we reanalyzed all CellSearch images previously acquired in the context of a prospective, multicenter clinical study for patients with mCRPC (n = 170) starting a new line of ARSi, for CTC and tdEV detection and enumeration. CTC (n = 19 129) phenotypic diversity was quantified by the Shannon index (SI). Progression-free survival (PFS) and overall survival (OS) were compared between groups of patients stratified according to CTC, tdEV, and SI levels.

Results

Automated CTC enumeration provided similar clinical prognostication compared with operator-based counts. Patients demonstrating high CTC phenotypic heterogeneity before therapy had a shorter median PFS (4.82 vs. 8.49 months, HR 1.79; P = 0.03) and OS (12.6 months vs. not reached, HR 2.32; P = 0.03), compared to patients with low diversity, irrespective of CTC level. Multivariable analysis showed how the prognostic value of the baseline SI was lost by pretreatment chemotherapy status, CTC counts, and PSA levels.

Conclusions

Automated CTC counts are a reliable substitute for reviewer-based enumeration, as they are equally informative for prognosis assessment in patients with mCRPC. Beyond enumeration, we demonstrated the added value of studying CTC phenotypic diversity for patient prognostication, warranting future investigation.

Accelerating precision medicine in metastatic prostate cancer

Despite advances in prostate cancer screening and treatment, available therapy options, particularly in later stages of the disease, remain limited and the treatment-resistant setting represents a serious unmet medical need. Moreover, disease heterogeneity and disparities in patient access to medical advances result in significant variability in outcomes across patients. Disease classification based on genomic sequencing is a promising approach to identify patients whose tumors exhibit actionable targets and make more informed treatment decisions. Here we discuss how we can accelerate precision oncology to inform broader genomically-driven clinical decisions for men with advanced prostate cancer, drug development and ultimately contribute to new treatment paradigms.

Omics Derived Biomarkers and Novel Drug Targets for Improved Intervention in Advanced Prostate Cancer

Prostate cancer (PCa) is one of the most frequently diagnosed malignancies, and the fifth leading cause of cancer related mortality in men. For advanced PCa, radical prostatectomy, radiotherapy, and/or long-term androgen deprivation therapy are the recommended treatment options. However, subsequent progression to metastatic disease after initial therapy results in low 5-year survival rates (29%). Omics technologies enable the acquisition of high-resolution large datasets that can provide insights into molecular mechanisms underlying PCa pathology. For the purpose of this article, a systematic literature search was conducted through the Web of Science Database to critically evaluate recent omics-driven studies that were performed towards: (a) Biomarker development and (b) characterization of novel molecular-based therapeutic targets. The results indicate that multiple omics-based biomarkers with prognostic and predictive value have been validated in the context of PCa, with several of those being also available for commercial use. At the same time, omics-driven potential drug targets have been investigated in pre-clinical settings and even in clinical trials, holding the promise for improved clinical management of advanced PCa, as part of personalized medicine pipelines.

Chelerythrine suppresses proliferation and metastasis of human prostate cancer cells via modulating MMP/TIMP/NF-κB system

Chelerythrine is a natural benzo[c]phenanthridine alkaloid found in many herbs and displays a wide range of antitumor activities. Here, the present study tested their effects on prostate cancer cells. The addition of chelerythrine can significantly inhibit the proliferation of androgen-independent prostate cancer DU145 and PC-3 cells at the concentration of 5 and 10 μM, but not on androgen-dependent prostate cancer LNCaP cells as well as normal prostate epithelial cell line PrEC cells. Wound migration and transwell invasion assay showed the similar inhibitory effect of chelerythrine on the migration and invasion of DU145 and PC-3 cells in the same condition. Western blot analysis further confirmed that chelerythrine not only dramatically decreased MMP-2, MMP-9, and uPA protein expression, but also augmented the expression of their endogenous inhibitors (TIMP-1 and TIMP-2) and plasminogen activator inhibitors (PAI-1 and PAI-2) in both cancer cells. Meanwhile, NF-κB and AP-1 transcription factors were all suppressed as evidenced by the decline of p-p65, c-Fos, and c-Jun protein expression in both cells. Taken together, these findings suggested that chelerythrine could reduce the metastasis of androgen-independent prostate cancer cells via modulation of MMP/TIMP system and inactivation of NF-κB pathway.

Single-Cell Circulating Tumor Cell Analysis Reveals Genomic Instability as a Distinctive Feature of Aggressive Prostate Cancer

PURPOSE

Aggressive variant prostate cancer (AVPC) represents a clinical subset distinguished by therapy resistance and poor prognosis, linked to combined losses of the tumor suppressor genes (TSG) PTEN, RB1, and TP53. Circulating tumor cells (CTC) provide a minimally invasive opportunity for identification and molecular characterization of AVPC. We aimed to evaluate the incidence and clinical significance of compound (2+)TSG losses and genomic instability in prostate cancer CTC, and to expand the set genomic biomarkers relevant to AVPC.

EXPERIMENTAL DESIGN

Genomic analysis of chromosomal copy-number alterations (CNA) at single-cell resolution was performed in CTC from patients with and without AVPC before initiating chemotherapy with cabazitaxel or cabazitaxel and carboplatin. We evaluated associations between single-CTC genomics and clinical features, progression-free survival, and overall survival.

RESULTS

A total of 257 individual CTC were sequenced from 47 patients (1-22 CTC/patient). Twenty patients (42.6%) had concurrent 2+TSG losses in at least one CTC in association with poor survival and increased genomic instability, inferred by high large-scale transitions scores. Higher LST in CTC were independent of CTC enumerated, clinically more indicative of aggressive behavior than co-occurring TSG losses, and molecularly associated with gains in chromosomal regions including PTK2, Myc, and NCOA2; increased androgen receptor expression; and BRCA2 loss. In 57 patients with matched cell-free tumor DNA data, CTC were more frequently detectable and evaluable for CNA analysis (in 73.7% vs. 42.1%, respectively).

CONCLUSIONS

Our findings suggest that genomic instability in CTC is a hallmark of advanced prostate cancer aggressiveness, and support single-CTC sequencing as a compelling tool to noninvasively characterize cancer heterogeneity.

Delta-like protein 3 expression and therapeutic targeting in neuroendocrine prostate cancer

Histologic transformation to small cell neuroendocrine prostate cancer occurs in a subset of patients with advanced prostate cancer as a mechanism of treatment resistance. Rovalpituzumab tesirine (SC16LD6.5) is an antibody-drug conjugate that targets delta-like protein 3 (DLL3) and was initially developed for small cell lung cancer. We found that DLL3 is expressed in most of the castration-resistant neuroendocrine prostate cancer (CRPC-NE) (36 of 47, 76.6%) and in a subset of castration-resistant prostate adenocarcinomas (7 of 56, 12.5%). It shows minimal to no expression in localized prostate cancer (1 of 194) and benign prostate (0 of 103). DLL3 expression correlates with neuroendocrine marker expression, RB1 loss, and aggressive clinical features. DLL3 in circulating tumor cells was concordant with matched metastatic biopsy (87%). Treatment of DLL3-expressing prostate cancer xenografts with a single dose of SC16LD6.5 resulted in complete and durable responses, whereas DLL3-negative models were insensitive. We highlight a patient with neuroendocrine prostate cancer with a meaningful clinical and radiologic response to SC16LD6.5 when treated on a phase 1 trial. Overall, our findings indicate that DLL3 is preferentially expressed in CRPC-NE and provide rationale for targeting DLL3 in patients with DLL3-positive metastatic prostate cancer.

Genomic Analysis of Circulating Tumor Cells at the Single-Cell Level

Circulating tumor cells (CTCs) have a great potential for noninvasive diagnosis and real-time monitoring of cancer. A comprehensive evaluation of four whole genome amplification (WGA)/next-generation sequencing workflows for genomic analysis of single CTCs, including PCR-based (GenomePlex and Ampli1), multiple displacement amplification (Repli-g), and hybrid PCR- and multiple displacement amplification–based [multiple annealing and loop-based amplification cycling (MALBAC)] is reported herein. To demonstrate clinical utilities, copy number variations (CNVs) in single CTCs isolated from four patients with squamous non–small-cell lung cancer were profiled. Results indicate that MALBAC and Repli-g WGA have significantly broader genomic coverage compared with GenomePlex and Ampli1. Furthermore, MALBAC coupled with low-pass whole genome sequencing has better coverage breadth, uniformity, and reproducibility and is superior to Repli-g for genome-wide CNV profiling and detecting focal oncogenic amplifications. For mutation analysis, none of the WGA methods were found to achieve sufficient sensitivity and specificity by whole exome sequencing. Finally, profiling of single CTCs from patients with non–small-cell lung cancer revealed potentially clinically relevant CNVs. In conclusion, MALBAC WGA coupled with low-pass whole genome sequencing is a robust workflow for genome-wide CNV profiling at single-cell level and has great potential to be applied in clinical investigations. Nevertheless, data suggest that none of the evaluated single-cell sequencing workflows can reach sufficient sensitivity or specificity for mutation detection required for clinical applications.

Lineage plasticity in cancer: a shared pathway of therapeutic resistance

Lineage plasticity, the ability of cells to transition from one committed developmental pathway to another, has been proposed as a source of intratumoural heterogeneity and of tumour adaptation to an adverse tumour microenvironment including exposure to targeted anticancer treatments. Tumour cell conversion into a different histological subtype has been associated with a loss of dependency on the original oncogenic driver, leading to therapeutic resistance. A well-known pathway of lineage plasticity in cancer - the histological transformation of adenocarcinomas to aggressive neuroendocrine derivatives - was initially described in lung cancers harbouring an EGFR mutation, and was subsequently reported in multiple other adenocarcinomas, including prostate cancer in the presence of antiandrogens. Squamous transformation is a subsequently identified and less well-characterized pathway of adenocarcinoma escape from suppressive anticancer therapy. The increased practice of tumour re-biopsy upon disease progression has increased the recognition of these mechanisms of resistance and has improved our understanding of the underlying biology. In this Review, we provide an overview of the impact of lineage plasticity on cancer progression and therapy resistance, with a focus on neuroendocrine transformation in lung and prostate tumours. We discuss the current understanding of the molecular drivers of this phenomenon, emerging management strategies and open questions in the field.

SLFN11 Expression in Advanced Prostate Cancer and Response to Platinum-based Chemotherapy

Expression of the DNA/RNA helicase schlafen family member 11 (SLFN11) has been identified as a sensitizer of tumor cells to DNA-damaging agents including platinum chemotherapy. We assessed the impact of SLFN11 expression on response to platinum chemotherapy and outcomes in patients with metastatic castration-resistant prostate cancer (CRPC). Tumor expression of SLFN11 was assessed in 41 patients with CRPC treated with platinum chemotherapy by RNA sequencing (RNA-seq) of metastatic biopsy tissue (n = 27) and/or immunofluorescence in circulating tumor cells (CTC; n = 20). Cox regression and Kaplan-Meier methods were used to evaluate the association of SLFN11 expression with radiographic progression-free survival (rPFS) and overall survival (OS). Multivariate analysis included tumor histology (i.e., adenocarcinoma or neuroendocrine) and the presence or absence of DNA repair aberrations. Patient-derived organoids with SLFN11 expression and after knockout by CRISPR-Cas9 were treated with platinum and assessed for changes in dose response. Patients were treated with platinum combination (N = 38) or platinum monotherapy (N = 3). Median lines of prior therapy for CRPC was two. Median OS was 8.7 months. Overexpression of SLFN11 in metastatic tumors by RNA-seq was associated with longer rPFS compared with those without overexpression (6.9 vs. 2.8 months, HR = 3.72; 95% confidence interval (CI), 1.56-8.87; P < 0.001); similar results were observed for patients with SLFN11-positive versus SLFN11-negative CTCs (rPFS 6.0 vs. 2.2 months, HR = 4.02; 95% CI, 0.77-20.86; P = 0.002). A prostate-specific antigen (PSA) decline of ≥50% was observed in all patients with SLFN11 overexpression. No association was observed between SLFN11 expression and OS. On multivariable analysis, SLFN11 was an independent factor associated with rPFS on platinum therapy. Platinum response of organoids expressing SLFN11 was reduced after SLFN11 knockout. Our data suggest that SLFN11 expression might identify patients with CRPC with a better response to platinum chemotherapy independent of histology or other genomic alterations. Additional studies, also in the context of PARP inhibitors, are warranted.

The emerging role of circulating tumor cells in cancer management

Circulating tumor cells (CTCs) are cells that are shed from the primary tumor and circulate in the blood, and their metastasis and formation of a secondary tumor are closely associated with cancer-related death. Therefore, regulating tumor metastasis through CTCs can be a novel strategy to fight cancer. It has been demonstrated that CTCs can reflect the profile of the primary tumor and provide valuable information about intratumoral heterogeneity and their evolution over time. Moreover, the revelation of the relationship between metastasis and CTCs suggests that CTC regulation represents a promising novel anticancer strategy. Above all, at the molecular level, genetic analysis might be vital in the new era of gene-targeted cancer therapies and contribute to personalized anti-metastasis tumor treatments. In this review, we will focus on the biological significance of CTCs in the peripheral blood and discuss their potential clinical implications in cancer management.