Circulating tumor cells capture disease evolution in advanced prostate cancer

Clinical value of circulating tumour cells in evaluating the efficacy of continuous hepatic arterial infusion among colorectal cancer patients

Few studies have been conducted to evaluate the efficacy of HAIC using circulating tumour cells (CTCs). In this study, a total of 100 patients who received HAIC treatment and CTC detection were selected. The results showed that after HAIC treatment, the levels of CTC, carbohydrate antigen 19-9 (CA19-9) and carcinoembryonic antigen (CEA) decreased. Postoperative progression-free survival (PFS) rates between patients with positive and negative preoperative CTC results, and for CA19-9, CEA were significantly different. The positive rate of CTCs was 61% before chemotherapy and 23% after chemotherapy, and the correlation coefficient between the two was 0.385. Those whose CTC values increased after chemotherapy had shorter PFS rates. CTCs are an independent predictor of recurrence. Patients with CTC-positive results are more susceptible to recurrence. The CTC count in peripheral blood has a close bearing on the postoperative chemotherapy efficacy of patients with CRC and affects patients' PFS.

Prostate cancer: Molecular aspects, consequences, and opportunities of the multifocal nature

Prostate cancer is unique compared to other major cancers due to the presence of multiple primary malignant foci in the majority of patients at the time of diagnosis. Each malignant focus has distinct somatic mutations and gene expression patterns, which represents a challenge for the development of prognostic tests for localized prostate cancer. Additionally, the molecular heterogeneity of advanced prostate cancer has important implications for management, particularly for patients with metastatic and locally recurrent cancer. Studies have shown that prostate cancers with mutations in DNA damage response genes are more sensitive to drugs inhibiting the poly ADP-ribose polymerase (PARP) enzyme. However, testing for such mutations should consider both spatial and temporal heterogeneity. Here, we summarize studies where multiregional genomics and transcriptomics analyses have been performed for primary prostate cancer. We further discuss the vast interfocal heterogeneity and how prognostic biomarkers and a molecular definition of the index tumor should be developed. The concept of focal treatments in prostate cancer has been evolving as a demand from patients and clinicians and is one example where there is a need for defining an index tumor. Here, biomarkers must have proven value for individual malignant foci. The potential discovery and implementation of biomarkers that are agnostic to heterogeneity are also explored as an alternative to multisample testing. Thus, deciding upon whole-organ treatment, such as radical prostatectomy, should depend on information from biomarkers which are informative for the whole organ.

Liquid Biopsy: A Distinctive Approach to the Diagnosis and Prognosis of Cancer

Cancer is a leading cause of morbidity and mortality worldwide. Over the past decades, the concept of precision cancer medicine has emerged as a novel approach in the field of oncology that aims to tailor the most effective treatment options to each individual cancer patient based on the genetic profile of the tumor of each individual patient. Recently, tissue biopsy has become an essential part of cancer care and is widely used to characterize the tumor. However, tissue biopsy techniques face different challenges due to their invasiveness, cost, time, and adversity in potential sampling due to tissue heterogeneity. To overcome these issues, a non-invasive approach has developed, which is known as liquid biopsy. It is a simple, fast, and worthwhile technique based on the analysis of circulating tumor DNA (which is a fraction of cfDNA), circulating tumor cells (CTCs), and other tumor-derived material in blood plasma. This review provides an overview of the concept of liquid biopsy and briefly discusses the role of ctDNA and CTC analysis as tools for early diagnosis and prognosis of cancer. In this review, we also speculate on the advantages of liquid biopsy as opposed to tissue biopsy and postulate that liquid biopsy may be a comprehensive approach to overcome the current limitations associated with costly, invasive, and time-consuming tissue biopsy.

EV Translational Horizons as Viewed Across the Complex Landscape of Liquid Biopsies

Extracellular Vesicle (EV)-based diagnostic and therapeutic tools are an area of intensive study and substantial promise, but EVs as liquid biopsies have advanced years ahead of EVs as therapeutic tools. EVs are emerging as a promising approach for detecting tumors, evaluating the molecular profiles of known disease, and monitoring treatment responses. Although correlative assays based on liquid biopsies are already having an impact on translational studies and clinical practice, much remains to be learned before these assays will be optimized for clinical correlations, functional biological studies, and therapeutic use. What follows is an overview of current evidence supporting the investigation and use of liquid biopsies, organized by specific liquid biopsy components available for analysis, along with a summary of what challenges must be overcome before these assays will provide functional biological insights into the pathogenesis and treatment of disease. The same challenges must also be overcome before it will be feasible to measure and monitor the dosing, distribution, pharmacokinetics, and delivery of EV therapeutics and their cargo in complex biofluids where EVs and circulate with and are co-isolated with a number of other nanoscale materials, including lipoproteins (LPPs), ribonucleoprotein complexes (RNPs), and cell free nucleic acids (cfNA).

The role of liquid biopsies in prostate cancer management

Liquid biopsy has emerged as a complement to invasive tissue biopsy to guide cancer diagnosis and treatment. The common liquid biopsy biomarkers are circulating tumor cells (CTCs), extracellular vesicles (EVs), and circulating tumor DNA (ctDNA). Each biomarker provides specific information based on its intrinsic characteristics. Prostate cancer is the second most common cancer in males worldwide. In men with low-grade localized prostate cancer, the disease can often be managed by active surveillance. For men who require treatment, the 5-year survival rate of localized prostate cancer is the highest among all cancer types, but the metastatic disease remains incurable. Metastatic prostate cancer invariably progresses to involve multiple bone sites and develops into a castration-resistant disease that leads to cancer death. The need to appropriately diagnose and guide the serial treatment of men with prostate cancer has led to the implementation of many studies to apply liquid biopsies to prostate cancer management. This review describes recent advancements in isolation and detection technology and the strength and weaknesses of the three circulating biomarkers. The clinical studies based on liquid biopsy results are summarized to depict the future perspective in the role of liquid biopsy on prostate cancer management.

Applicability of liquid biopsies to represent the mutational profile of tumor tissue from different cancer entities

Genetic investigation of tumor heterogeneity and clonal evolution in solid cancers could be assisted by the analysis of liquid biopsies. However, tumors of various entities might release different quantities of circulating tumor cells (CTCs) and cell-free DNA (cfDNA) into the bloodstream, potentially limiting the diagnostic potential of liquid biopsy in distinct tumor histologies. Patients with advanced colorectal cancer (CRC), head and neck squamous cell carcinoma (HNSCC), and melanoma (MEL) were enrolled in the study, representing tumors with different metastatic patterns. Mutation profiles of cfDNA, CTCs, and tumor tissue were assessed by panel sequencing, targeting 327 cancer-related genes. In total, 30 tissue, 18 cfDNA, and 7 CTC samples from 18 patients were sequenced. Best concordance between the mutation profile of tissue and cfDNA was achieved in CRC and MEL, possibly due to the remarkable heterogeneity of HNSCC (63%, 55% and 11%, respectively). Concordance especially depended on the amount of cfDNA used for library preparation. While 21 of 27 (78%) tissue mutations were retrieved in high-input cfDNA samples (30-100 ng, N = 8), only 4 of 65 (6%) could be detected in low-input samples (<30 ng, N = 10). CTCs were detected in 13 of 18 patients (72%). However, downstream analysis was limited by poor DNA quality, allowing targeted sequencing of only seven CTC samples isolated from four patients. Only one CTC sample reflected the mutation profile of the respective tumor. Private mutations, which were detected in CTCs but not in tissue, suggested the presence of rare subclones. Our pilot study demonstrated superiority of cfDNA- compared to CTC-based mutation profiling. It was further shown that CTCs may serve as additional means to detect rare subclones possibly involved in treatment resistance. Both findings require validation in a larger patient cohort.

Metastatic Spread in Prostate Cancer Patients Influencing Radiotherapy Response

Radiotherapy and surgery are curative treatment options for localized prostate cancer (PCa) with a 5-year survival rate of nearly 100%. Once PCa cells spread into distant organs, such as bone, the overall survival rate of patients drops dramatically. The metastatic cascade and organotropism of PCa cells are regulated by different cellular subtypes, organ microenvironment, and their interactions. This cross-talk leads to pre-metastatic niche formation that releases chemo-attractive factors enforcing the formation of distant metastasis. Biological characteristics of PCa metastasis impacting on metastatic sites, burden, and latency is of clinical relevance. Therefore, the implementation of modern hybrid imaging technologies into clinical routine increased the sensitivity to detect metastases at earlier stages. This enlarged the number of PCa patients diagnosed with a limited number of metastases, summarized as oligometastatic disease. These patients can be treated with androgen deprivation in combination with local-ablative radiotherapy or radiopharmaceuticals directed to metastatic sites. Unfortunately, the number of patients with disease recurrence is high due to the enormous heterogeneity within the oligometastatic patient population and the lack of available biomarkers with predictive potential for metastasis-directed radiotherapy. Another, so far unmet clinical need is the diagnosis of minimal residual disease before onset of clinical manifestation and/or early relapse after initial therapy. Here, monitoring of circulating and disseminating tumor cells in PCa patients during the course of radiotherapy may give us novel insight into how metastatic spread is influenced by radiotherapy and vice versa. In summary, this review critically compares current clinical concepts for metastatic PCa patients and discuss the implementation of recent preclinical findings improving our understanding of metastatic dissemination and radiotherapy resistance into standard of care.

Epithelial-mesenchymal transition of circulating tumor cells in prostate cancer is promoted by survivin

Objective

Recent studies demonstrated that circulating tumor cells (CTCs) contribute to the metastasis of prostate cancer. Survivin knockout could inhibit epithelial-mesenchymal transition (EMT) and suppress several metastatic tumors. In this study, we examined the potential involvement of survivin in EMT in CTCs.

Methods

CTCs were isolated from the peripheral blood of 100 patients with prostate cancer as EpCAM⁺/CD45⁻ cells via FACS sorting and identified by immunofluorescence staining of prostate-specific antigen (PSA). CTCs and DU145 cells were transfected with survivin siRNA. Then, the levels of survivin, E-cadherin, and vimentin in CTCs and DU145 cells were detected via immunofluorescence staining, and the invasiveness of CTCs and DU145 cells was examined using a Transwell chamber.

Results

The results revealed the abundant expression of PSA in the cytoplasm of CTCs. Transfection of survivin siRNA significantly decreased the levels of survivin and vimentin in CTCs and DU145, whereas that of E-cadherin was significantly increased, suggesting survivin plays an important role in EMT of CTCs. In addition, survivin siRNA significantly inhibited the invasiveness of CTCs and DU145 cells.

Conclusions

Survivin plays an important role in EMT of CTCs in prostate cancer, which might mediate the metastasis and invasion of prostate cancer.

Recognition of Invasive Prostate Cancer Using a GHRL Polypeptide Probe Targeting GHSR in a Mouse Model In Vivo

BACKGROUND

Ghrelin (GHRL) is a polypeptide that can specifically bind to the growth hormone secretagogue receptor (GHSR). The expression of GHSR is significantly different in normal and prostate cancer (PC) tissues in humans. It is important to find an effective diagnostic method for the diagnosis and prognosis of invasive PC/neuroendocrine prostate cancer (NEPC).

METHODS

GHRL and GHSR mRNA levels were determined by a quantitative real-time polymerase chain reaction in PC tissues. The expression of GHRL and GHSR proteins was assessed by Western blot assay and immunohistochemistry. A GHRL polypeptide probe was synthesized by standard solid-phase polypeptide synthesis, and labeled with Alexa Fluor 660. Confocal microscopy was used to capture fluorescence images. Living imaging analysis showed tumor areas of different invasiveness in mice models.

RESULTS

The levels of GHRL and GHSR copy number amplification and mRNA expression were increased in invasive PC/NEPC, and the protein expression levels of GHRL and GHSR were similarly increased in NEPC. The GHRL polypeptide probe could effectively bind to GHSR. In PC3 cells, it was found that the GHRL probe specifically binds to GHSR on the cell membrane and accumulates in the cells through internalization after binding. Live imaging in mice models showed that there were different signal intensities in tumor areas with different invasiveness.

CONCLUSION

GHSR and GHRL might be used in molecular imaging diagnosis for invasive PC/NEPC in the future.

Global Gene Expression Characterization of Circulating Tumor Cells in Metastasic Castration-Resistant Prostate Cancer Patients

Background: Current therapeutic options in the course of metastatic castration-resistant prostate cancers (mCRPC) reinforce the need for reliable tools to characterize the tumor in a dynamic way. Circulating tumor cells (CTCs) have emerged as a viable solution to the problem, whereby patients with a variety of solid tumors, including PC, often do not have recent tumor tissue available for analysis. The biomarker characterization in CTCs could provide insights into the current state of the disease and an overall picture of the intra-tumor heterogeneity. Methods: in the present study, we applied a global gene expression characterization of the CTC population from mCRPC (n = 9), with the goal to better understand the biology of these cells and identify the relevant molecules favoring this tumor progression. Results: This analysis allowed the identification of 50 genes specifically expressed in CTCs from patients. Six of these markers (HOXB13, QKI, MAOA, MOSPD1, SDK1, and FGD4), were validated in a cohort of 28 mCRPC, showing clinical interest for the management of these patients. Of note, the activity of this CTC signature was related to the regulation of MYC, a gene strongly implicated in the biology of mCRPC. Conclusions: Overall, our results represent new evidence on the great value of CTCs as a non-invasive biopsy to characterize PC.

Clinical significance of epithelial-mesenchymal transition typing of circulating tumour cells in colorectal cancer

AIM

The aim was to determine the diagnostic value of epithelial-mesenchymal transition typing of circulating tumour cells (CTCs) in colorectal cancer (CRC).

METHOD

Peripheral blood samples were collected from 51 CRC patients before anti-tumour treatment from April 2016 to June 2018 at the Peking University Shenzhen Hospital. The blood samples were analysed using the CanPatrol CTC typing technique (SurExam, Guangzhou, China), which combines nanomembrane enrichment with mRNA in situ hybridization. Based on the marker expression, the CTCs were classified into epithelial, epithelial mesenchymal and mesenchymal (M-CTC) types. The correlation between the CTC counts and clinicopathological characteristics such as gender, age, TNM stage, lymph node metastasis and distant metastasis were analysed by univariate and multivariate Cox regression models. The overall survival and progression-free survival (PFS) of patients demarcated by CTC typing were analysed using the Kaplan-Meier method and log-rank tests.

RESULT

M-CTCs were detected more frequently in patients with lymph node metastasis (N2 81.8%; N1 72.7%; N0 38.9%) as well as distant metastasis (M0 50%; M1a 81.25%; M1b 85.7%) compared to those without metastasis. In addition, the presence of M-CTCs was significantly correlated with distant metastasis (P < 0.01). Univariate analysis showed that lymph node metastasis (P = 0.035), distant metastasis (P < 0.001) and total CTC count ≥ 4 (P = 0.007) and M-CTC count ≥ 1 (P < 0.001) were significantly associated with unfavourable PFS, and lymph node metastasis (P = 0.04), distant metastasis (P = 0.01) and M-CTC count ≥ 1 (P < 0.001) were significantly associated with unfavourable overall survival. Multivariate analysis showed that the presence of M-CTCs was the only independent prognostic factor for poor PFS, and patients with M-CTCs had significantly shorter PFS than those without (P = 0.011).

CONCLUSION

M-CTCs are significantly associated with CRC severity and metastasis, and M-CTC count is an independent predictor of prognosis.

Perspectives of the Application of Liquid Biopsy in Colorectal Cancer

Colorectal cancer (CRC) is one of the most common gastrointestinal tumors and the second leading cause of cancer death worldwide. Since traditional biopsies are invasive and do not reflect tumor heterogeneity or monitor the dynamic progression of tumors, there is an urgent need for new noninvasive methods that can supplement and improve the current management strategies of CRC. Blood-based liquid biopsies are a promising noninvasive biomarker that can detect disease early, assist in staging, monitor treatment responses, and predict relapse and metastasis. Over time, an increasing number of experiments have indicated the clinical utility of liquid biopsies in CRC. In this review, we mainly focus on the development of circulating tumor cells and circulating tumor DNA as key components of liquid biopsies in CRC and introduce the potential of exosomal microRNAs as emerging liquid biopsy markers in clinical application for CRC.

The Discordance of Gene Mutations between Circulating Tumor Cells and Primary/Metastatic Tumor

Circulating tumor cells (CTCs) are an important part in the field of "liquid biopsy." However, major questions remain to be answered whether the mutations in the CTCs represent the mutations in primary tumor tissue and metastatic tumors. We compared the genetic mutations between CTCs and their matched tumors, and extracted data on the heterogeneity of the mutational status in CTCs and the change in mutations of CTCs before and during treatment. For mutations detected in single genes, we calculated the concordance of the mutations between the CTCs and primary tumor tissue. For mutations detected in multiple genes, we calculated the concordance of the mutations between the CTCs and primary/metastatic tumor tissue. The heterogeneity of the mutational status is clearly present in CTCs. For mutations detected in a single gene, the overall concordance of mutations is 53.05%. For mutations detected in multiple genes, the concordance of mutations is extremely different. The heterogeneity of the mutational status existed in single CTCs, and the mutational status of CTCs was discordant with that of tumor tissue.

Whole Genome Sequencing of Single Circulating Tumor Cells Isolated by Applying a Pulsed Laser to Cell-Capturing Microstructures

Single cell analysis of heterogeneous circulating tumor cells (CTCs), by which the genomic profiles of rare single CTCs are connected to the clinical status of cancer patients, is crucial for understanding cancer metastasis and the clinical impact on patients. However, the heterogeneity in genotypes and phenotypes and rarity of CTCs have limited extensive single CTC genome research, further hindering clinical investigation. Despite recent efforts to build platforms that separate CTCs, the investigation on CTCs is difficult due to the lack of a retrieval process at the single cell level. In this study, laser-induced isolation of microstructures on an optomechanically-transferrable-chip and sequencing (LIMO-seq) is applied for whole genome sequencing of single CTCs. Also, the whole genome sequences and the molecular profiles of the isolated single cells from the whole blood of a breast cancer patient are analyzed.

Circulating Tumor Cells as a Tool for Assessing Tumor Heterogeneity

Tumor heterogeneity is the major cause of failure in cancer prognosis and prediction. Accurately detecting heterogeneity for the development of biomarkers and the detection of the clones resistant to therapy is one of the main goals of contemporary medicine. Metastases belong to the natural history of cancer. The present review gives an overview on the origin of tumor heterogeneity. Recent progress has made it possible to isolate and characterize circulating tumor cells (CTCs), which are the drivers of the disease between the primary sites and metastatic foci. The most recent methods for characterizing CTCs are summarized and we discuss the power of CTC profiling for analyzing tumor heterogeneity in early and advanced diseases.

Circulating tumor cells as an independent prognostic factor in advanced colorectal cancer: a retrospective study in 121 patients

PURPOSE

This study aimed to evaluate the prognostic value of circulating tumor cells (CTCs) in advanced colorectal cancer (CRC) patients during chemotherapy course.

METHODS

From January 2016 to September 2017, the clinicopathological variables, such as gender, age, tumor location, tumor de-differentiation, depth of invasion, lymphatic invasion, distant metastasis, TNM stage, CTCs enumeration during 2-6 cycles of chemotherapy, and serum carcinoembryonic antigen (CEA) level during the same period, of 121 newly acquired and histopathologically confirmed CRC patients were collected from the Shanghai Ninth People's Hospital affiliated to Shanghai Jiao Tong University School of Medicine. All patients were followed up for survival until the end of November 2018. Statistical analysis focused on the associations between CTCs counts and clinicopathological variables. Overall survival (OS) and progression-free survival (PFS) among different prognostic factors were calculated using the Kaplan-Meier method, and the differences between the survival curves were compared by using the log-rank test. Factors of prognostic significance were investigated with the multivariate Cox regression analysis.

RESULTS

Here, 71 of 121 patients were CTC-positive, in which CTC-positive rate was positively correlated with the depth of invasion, lymphatic invasion, distant metastasis, TNM stage, and serum CEA level (P < 0.05 for all). However, no significant difference was found between CTC-positive and other clinicopathological variables (P > 0.05 for all), such as gender, age, tumor location, and tumor de-differentiation. CTCs counts gradually increased with the advancement of depth of invasion (P = 0.002), lymphatic invasion (P = 0.004), distant metastasis (P = 0.007), TNM stage (P = 0.001), serum CEA level (P = 0.001), and decreased tumor de-differentiation (P = 0.011). Furthermore, the Kaplan-Meier survival curves showed that patients with CTC-positive had a significantly unfavorable PFS (14 vs. 23 months, P = 0.001) and OS (18 vs. 25 months, P = 0.003). The multivariate Cox regression analyses revealed that the presence of CTCs during chemotherapy was an independent factor for unfavorable PFS (hazard ratio (HR) 2.682, P = 0.017, 95% confidence interval (CI) 1.193-6.029) and OS (HR 2.790, P = 0.048, 95% CI 1.010-7.705) in advanced CRC patients.

CONCLUSIONS

This study provided an evidence that the presence of CTCs may be valuable for predicting survival outcome, and CTCs was associated with unfavorable survival in advanced CRC patients during chemotherapy.

Single-Cell Genomics

BACKGROUND

Single-cell genomics is an approach to investigate cell heterogeneity and to identify new molecular features correlated with clinical outcomes. This approach allows identification of the complexity of cell diversity in a sample without the loss of information that occurs when multicellular or bulk tissue samples are analyzed.

CONTENT

The first single-cell RNA-sequencing study was published in 2009, and since then many more studies and single-cell sequencing methods have been published. These studies have had a major impact on several fields, including microbiology, neurobiology, cancer, and developmental biology. Recently, improvements in reliability and the development of commercial single-cell isolation platforms are opening the potential of this technology to the clinical laboratory.

SUMMARY

In this review we provide an overview of the current state of single-cell genomics. We describe opportunities in clinical research and medical applications.

The Role of RB in Prostate Cancer Progression

The RB tumor suppressor is one of the most commonly deleted/mutated genes in human cancers. In prostate cancer specifically, mutation of RB is most frequently observed in aggressive, metastatic disease. As one of the earliest tumor suppressors to be identified, the molecular functions of RB that are lost in tumor development have been studied for decades. Earlier work focused on the canonical RB pathway connecting mitogenic signaling to the cell cycle via Cyclin/CDK inactivation of RB, thereby releasing the E2F transcription factors. More in-depth analysis revealed that RB-E2F complexes regulate cellular processes beyond proliferation. Most recently, "non-canonical" roles for RB function have been expanded beyond its E2F interactions, which may play a particular role in advanced prostate cancer. For example, in mouse models of prostate cancer, loss of RB has been shown to induce lineage plasticity, which enables resistance to androgen deprivation therapy. This increased understanding of the potential downstream functions of RB in prostate cancer may lead the way to identifying therapeutic vulnerabilities in cells following RB loss.

Liquid biopsy approach in the management of prostate cancer

Liquid biopsies examine tumor cells or tumor genomic content in circulating fluids. In advanced prostate cancer which metastasizes frequently to the bone, it is difficult to evaluate underlying and evolving genomic heterogeneity of skeletal metastases for effecting clinical care for which reason liquid biopsies offer an alternate approach. In this review, we will summarize the current state of a wide variety of liquid biopsy-based biomarker assays currently being investigated and developed for managing prostate cancer. We will also highlight technical and clinical challenges and opportunities for translating liquid biopsies into clinical applications.

Concise Review: Prostate Cancer Stem Cells: Current Understanding

Prostate cancer (PCa) is heterogeneous, harboring phenotypically diverse cancer cell types. PCa cell heterogeneity is caused by genomic instability that leads to the clonal competition and evolution of the cancer genome and by epigenetic mechanisms that result in subclonal cellular differentiation. The process of tumor cell differentiation is initiated from a population of prostate cancer stem cells (PCSCs) that possess many phenotypic and functional properties of normal stem cells. Since the initial reports on PCSCs in 2005, there has been much effort to elucidate their biological properties, including unique metabolic characteristics. In this Review, we discuss the current methods for PCSC enrichment and analysis, the hallmarks of PCSC metabolism, and the role of PCSCs in tumor progression. Stem Cells 2018;36:1457-1474.

AR-v7 liquid biopsy for treatment stratification in prostate cancer: how close are we?

PURPOSE OF REVIEW

Recent clinical introduction of the novel antiandrogen, Enzalutamide (Enza), CYP17 inhibitor, Abiraterone (Abi), and the second-generation chemotherapeutic, Cabazitaxel, has increased survival of patients with advanced, metastatic castration-resistant prostate cancer (mCRPC). However, de novo and acquired resistance rates are high. A liquid biopsy that can rapidly, sensitively and robustly identify which patients will respond to treatment in a minimally invasive manner is urgently required to permit switch to a potentially more efficacious drug regimen, thus increasing survival whilst avoiding debilitating side effects associated with unnecessary treatment. This review will highlight recent developments in detection of AR-v7 in circulating mRNA/whole blood and circulating tumour cells (CTCs) as a liquid biopsy for patient-stratification in mCRPC.

RECENT FINDINGS

Continued androgen receptor (AR) activity in mCRPC has been linked to the expression of a number of truncated but constitutively active AR isoforms. One such variant, AR-v7, can drive drug resistance in preclinical models and is correlated with disease progression whilst showing dynamic response to AR-targeting treatments when assessed in blood. It has thus been proposed as an Abi/Enza treatment-response biomarker.

SUMMARY

AR-v7 liquid biopsy has the potential to transform clinical management of mCRPC and increase patient survival. This review will explore recent efforts to validate AR-v7 as a robust, clinically informative biomarker. I will also address potential limitations of detection and quantification that could frustrate its adoption into routine clinical practise.

Epigenetic reprogramming: A key mechanism driving therapeutic resistance

Prostate cancer initiation, development and progression is driven by androgen receptor (AR) signaling. Androgen deprivation therapy is the primary treatment for patients that present with locally advanced or metastatic disease. However, androgen deprivation therapy is not curative, and patients will progress to castrate-resistant disease (CRPC). Although most patient's progress to CRPC via restoration of AR signaling (CRPC-Ad), approximately a quarter of patients will progress via mechanisms independent of AR signaling. This highly lethal phenotype is termed aggressive variant prostate cancer (AVPC). Data from clinical and preclinical studies demonstrate that AVPC involves combinatorial loss-of-function mutations in key tumor suppressor genes, low to absent AR levels, and re-expression of reprogramming, stem, and neuroendocrine related gene signatures. Further, AVPC is shown to evolve from a CRPC-Ad phenotype. Overall, lineage plasticity underlying progression to AVPC is thought to be provoked by genome-wide chromatin remodeling. Here, we will discuss an emerging focus on key drivers of chromatin remodeling in AVPC, and how their identification could provide noninvasive biomarkers to predict or detect AVPC emergence, and therapeutic targets to prevent or reverse progression to AVPC.

Nanotechnology-Based Strategies for Early Cancer Diagnosis Using Circulating Tumor Cells as a Liquid Biopsy

Circulating tumor cells (CTCs) are cancer cells that shed from a primary tumor and circulate in the bloodstream. As a form of “tumor liquid biopsy”, CTCs provide important information for the mechanistic investigation of cancer metastasis and the measurement of tumor genotype evolution during treatment and disease progression. However, the extremely low abundance of CTCs in the peripheral blood and the heterogeneity of CTCs make their isolation and characterization major technological challenges. Recently, nanotechnologies have been developed for sensitive CTC detection; such technologies will enable better cell and molecular characterization and open up a wide range of clinical applications, including early disease detection and evaluation of treatment response and disease progression. In this review, we summarize the nanotechnology-based strategies for CTC isolation, including representative nanomaterials (such as magnetic nanoparticles, gold nanoparticles, silicon nanopillars, nanowires, nanopillars, carbon nanotubes, dendrimers, quantum dots, and graphene oxide) and microfluidic chip technologies that incorporate nanoroughened surfaces and discuss their key challenges and perspectives in CTC downstream analyses, such as protein expression and genetic mutations that may reflect tumor aggressiveness and patient outcome.