Quantitative characterization of androgen receptor protein expression and cellular localization in circulating tumor cells from patients with metastatic castration-resistant prostate cancer

MYB interacts with androgen receptor, sustains its ligand-independent activation and promotes castration resistance in prostate cancer

BACKGROUND

Aberrant activation of androgen receptor signalling following castration therapy is a common clinical observation in prostate cancer (PCa). Earlier, we demonstrated the role of MYB overexpression in androgen-depletion resistance and PCa aggressiveness. Here, we investigated MYB-androgen receptor (AR) crosstalk and its functional significance.

METHODS

Interaction and co-localization of MYB and AR were examined by co-immunoprecipitation and immunofluorescence analyses, respectively. Protein levels were measured by immunoblot analysis and enzyme-linked immunosorbent assay. The role of MYB in ligand-independent AR transcriptional activity and combinatorial gene regulation was studied by promoter-reporter and chromatin immunoprecipitation assays. The functional significance of MYB in castration resistance was determined using an orthotopic mouse model.

RESULTS

MYB and AR interact and co-localize in the PCa cells. MYB-overexpressing PCa cells retain AR in the nucleus even when cultured under androgen-deprived conditions. AR transcriptional activity is also sustained in MYB-overexpressing cells in the absence of androgens. MYB binds and promotes AR occupancy to the KLK3 promoter. MYB-overexpressing PCa cells exhibit greater tumorigenicity when implanted orthotopically and quickly regain growth following castration leading to shorter mice survival, compared to those carrying low-MYB-expressing prostate tumours.

CONCLUSIONS

Our findings reveal a novel MYB-AR crosstalk in PCa and establish its role in castration resistance.

Circulating tumor cell profiling for precision oncology

Analysis of circulating tumor cells (CTCs) collected from patient's blood offers a broad range of opportunities in the field of precision oncology. With new advances in profiling technology, it is now possible to demonstrate an association between the molecular profiles of CTCs and tumor response to therapy. In this Review, we discuss mechanisms of tumor resistance to therapy and their link to phenotypic and genotypic properties of CTCs. We summarize key technologies used to isolate and analyze CTCs and discuss recent clinical studies that examined CTCs for genomic and proteomic predictors of responsiveness to therapy. We also point out current limitations that still hamper the implementation of CTCs into clinical practice. We finally reflect on how these shortcomings can be addressed with the likely contribution of multiparametric approaches and advanced data analytics.

Preclinical and Clinical Status of PSMA-Targeted Alpha Therapy for Metastatic Castration-Resistant Prostate Cancer

Bone, lymph node, and visceral metastases are frequent in castrate-resistant prostate cancer patients. Since such patients have only a few months' survival benefit from standard therapies, there is an urgent need for new personalized therapies. The prostate-specific membrane antigen (PSMA) is overexpressed in prostate cancer and is a molecular target for imaging diagnostics and targeted radionuclide therapy (theragnostics). PSMA-targeted α therapies (PSMA-TAT) may deliver potent and local radiation more selectively to cancer cells than PSMA-targeted β- therapies. In this review, we summarize both the recent preclinical and clinical advances made in the development of PSMA-TAT, as well as the availability of therapeutic α-emitting radionuclides, the development of small molecules and antibodies targeting PSMA. Lastly, we discuss the potentials, limitations, and future perspectives of PSMA-TAT.

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.

Molecular tracing of prostate cancer lethality

Prostate cancer is diagnosed mostly in men over the age of 50 years, and has favorable 5-year survival rates due to early cancer detection and availability of curative surgical management. However, progression to metastasis and emergence of therapeutic resistance are responsible for the majority of prostate cancer mortalities. Recent advancement in sequencing technologies and computational capabilities have improved the ability to organize and analyze large data, thus enabling the identification of novel biomarkers for survival, metastatic progression and patient prognosis. Large-scale sequencing studies have also uncovered genetic and epigenetic signatures associated with prostate cancer molecular subtypes, supporting the development of personalized targeted-therapies. However, the current state of mainstream prostate cancer management does not take full advantage of the personalized diagnostic and treatment modalities available. This review focuses on interrogating biomarkers of prostate cancer progression, including gene signatures that correspond to the acquisition of tumor lethality and those of predictive and prognostic value in progression to advanced disease, and suggest how we can use our knowledge of biomarkers and molecular subtypes to improve patient treatment and survival outcomes.

Tracking the expression of therapeutic protein targets in rare cells by antibody-mediated nanoparticle labelling and magnetic sorting

Molecular-level features of tumours can be tracked using single-cell analyses of circulating tumour cells (CTCs). However, single-cell measurements of protein expression for rare CTCs are hampered by the presence of a large number of non-target cells. Here, we show that antibody-mediated labelling of intracellular proteins in the nucleus, mitochondria and cytoplasm of human cells with magnetic nanoparticles enables analysis of target proteins at the single-cell level by sorting the cells according to their nanoparticle content in a microfluidic device with cell-capture zones sandwiched between arrays of magnets. We used the magnetic labelling and cell-sorting approach to track the expression of therapeutic protein targets in CTCs isolated from blood samples of mice with orthotopic prostate xenografts and from patients with metastatic castration-resistant prostate cancer. We also show that mutated proteins that are drug targets or markers of therapeutic response can be directly identified in CTCs, analysed at the single-cell level and used to predict how mice with drug-susceptible and drug-resistant pancreatic tumour xenografts respond to therapy.

CD133 suppression increases the sensitivity of prostate cancer cells to paclitaxel

One of the major barriers in cancer therapy is the resistance to conventional therapies and cancer stem cells (CSCs) are among the main causes of this problem. CD133 as a CSC marker displays stem cell-like properties, tumorigenic capacity, and drug resistance in various cancers. However, the molecular mechanism behind CD133 function in prostate cancer (PC) still remains unclear. This research aimed to illustrate the probabilistic mechanism of CD133-siRNA and paclitaxel in the reduction of chemoresistance in PC cells. To measure the cell viability, migratory capacity, CSCs properties, invasive potential, apoptosis and cell cycle progression of the cells, the MTT, wound healing, spheroid assay, colony formation assay, DAPI staining and flow cytometry assays were applied in the LNCaP cell line, respectively. Also, quantitative real-time PCR (qRT-PCR) and western blot method were used for measuring the expression of CD133 and the effects of CD133 silencing on the AKT/mTOR/c-myc axis and pro-metastatic genes expression. We showed that the CD133-siRNA considerably decreased the CD133 expression. Moreover, CD133-siRNA and paclitaxel treatment significantly decreased cell proliferation and also inhibited the ability of cell migration and invasion and reduced pro-metastatic genes expression. Additionally, we found that the simultaneous use of CD133-siRNA and paclitaxel increased the paclitaxel-induced apoptosis. Our results confirmed that CD133 silencing combined with paclitaxel synergistically could suppress cell migration, invasion, and proliferation and enhance the chemosensitivity compared with mono treatment. Therefore, CD133 silencing therapy could be viewed as a promising and efficient strategy in PC targeted therapies.

The Prospect of Identifying Resistance Mechanisms for Castrate-Resistant Prostate Cancer Using Circulating Tumor Cells: Is Epithelial-to-Mesenchymal Transition a Key Player?

Prostate cancer (PCa) is initially driven by excessive androgen receptor (AR) signaling with androgen deprivation therapy (ADT) being a major therapeutic approach to its treatment. However, the development of drug resistance is a significant limitation on the effectiveness of both first-line and more recently developed second-line ADTs. There is a need then to study AR signaling within the context of other oncogenic signaling pathways that likely mediate this resistance. This review focuses on interactions between AR signaling, the well-known phosphatidylinositol-3-kinase/AKT pathway, and an emerging mediator of these pathways, the Hippo/YAP1 axis in metastatic castrate-resistant PCa, and their involvement in the regulation of epithelial-mesenchymal transition (EMT), a feature of disease progression and ADT resistance. Analysis of these pathways in circulating tumor cells (CTCs) may provide an opportunity to evaluate their utility as biomarkers and address their importance in the development of resistance to current ADT with potential to guide future therapies.

Determination of the androgen receptor status of circulating tumour cells in metastatic breast cancer patients

BACKGROUND

The prognostic relevance of circulating tumour cells (CTCs) in metastatic breast cancer (MBC) patients has been confirmed by several clinical trials. However, predictive blood-based biomarkers for stratification of patients for targeted therapy are still lacking. The DETECT studies explore the utility of CTC phenotype for treatment decisions in patients with HER2 negative MBC. Associated with this concept is a plethora of translational projects aiming to identify potential predictive biomarkers. The androgen receptor (AR) is expressed in over 70% of hormone receptor-positive and up-to 45% of triple-negative tumours. Studies has indicated the promising nature of AR as a new therapy target with a clinical benefit rate for anti-AR treatment in MBC patients up to 25% The aim of this analysis was the characterization of CTCs regarding the expression of the AR using immunofluorescence.

METHODS

MBC patients were screened for the HER2-status of CTCs in the DETECT studies. In a subset of CTC-positive patients (n = 67) an additional blood sample was used for immunomagnetic enrichment of CTCs using the CellSearch® Profile Kit prior to transfer of the cells onto cytospin slides. Establishment of immunofluorescence staining for the AR was performed using prostate cancer cell lines LNCaP and DU145 as positive and negative control, respectively. Staining of DAPI, pan-cytokeratin (CK) and CD45 was applied to identify nucleated epithelial cells as CTCs and to exclude leucocytes.

RESULTS

Co-staining of the AR, CK and CD45 according to the above mentioned workflow has been successfully established using cell lines with known AR expression spiked into the blood samples from healthy donors. For this translational project, samples were analysed from 67 patients participating in the DETECT studies. At least one CTC was detected in 37 out of 67 patients (56%). In 16 of these 37 patients (43%) AR-positive CTCs were detected. In eight out of 25 patients (32%) with more than one CTC, AR-positive and AR-negative CTCs were observed.

CONCLUSION

In 43% of the analysed CTC samples from patients with MBC the AR expression has been detected. The predictive value of AR expression in CTCs remains to be evaluated in further trials.

Cytomorphological Characterization of Individual Metastatic Tumor Cells from Gastrointestinal Cancer Patient Lymph Nodes with Imaging Flow Cytometry

The presence or absence of tumor cells within patient lymph nodes is an important prognostic indicator in a number of cancer types and an essential element of the staging process. However, patients with the same pathological stage will not necessarily have the same outcome. Therefore, additional factors may aid in identifying patients at a greater risk of developing metastasis. In this proof of principle study, initially, spiked tumor cells in rat lymph nodes were used to mimic a node with a small cancer deposit. Next, human lymph nodes were obtained from cancer patients for morphological characterization. Nodes were dissociated with a manual tissue homogenizer and stained with fluorescent antibodies against CD45 and Pan-Cytokeratin and then imaging flow cytometry (AMNIS ImageStreamX Mark II) was performed. We show here that imaging flow cytometry can be used for the detection and characterization of small numbers of cancer cells in lymph nodes and we also demonstrate the phenotypical and morphological characterization of cancer cells in gastrointestinal cancer patient lymph nodes. When used in addition to conventional histological techniques, this high throughput detection of tumor cells in lymph nodes may offer additional information assisting in the staging process with therapeutic and prognostic applications.

iTRAQ-based Comparative Serum Proteomic Analysis of Prostate Cancer Patients with or without Bone Metastasis

Background: Once prostate cancer developed bone metastasis, the quality of life and prognosis of patients are seriously affected as no effective treatment is currently available. It is necessary to explore the mechanism of bone metastasis and new therapeutic targets. Purpose: To find out the differentially expressed serum proteins in prostate cancer patients with bone metastasis and analyze the expression of key proteins in prostate cancer tissues, serum and prostate cancer cell lines. So as to provide a basis for revealing the mechanism of bone metastasis and designing new therapeutic targets. Methods: iTRAQ-based proteomics method was used to compare serum differential proteins in prostate cancer patients with and without bone metastasis. Three key proteins (CD59, haptoglobin and tetranectin) which had significant fold changes were selected to validate the results of mass spectrometry. Immunohistochemistry and ELISA were applied to tissues and serum samples from prostate cancer patients, respectively, for validation. Finally, western blot, flow cytometry, and immunocytochemistry were used to analyze the expression of the three differentially expressed proteins in the prostate cancer cell lines PC3, LNCap, and Du145. Results: Thirty-two differentially expressed proteins related to bone metastasis of prostate cancer were identified, of which 11 were up-regulated and 21 were down-regulated. CD59 and haptoglobin were up-regulated in prostate cancer with bone metastasis while tetranectin was down-regulated. Tetranectin showed differential expression in epithelial and stromal cells of prostate cancer and hyperplasia tissues.The expression of CD59 was highest in PC3 and lowest in LNCap, while the expression of haptoglobin and tetranectin was the highest in DU145 and lowest in PC3. Conclusion: Mass spectrometry analysis showed that there were more differentially expressed proteins in the serum of patients with bone metastasis than those without metastasis. It has been verified that CD59, haptoglobin and tetranectin are prostate cancer bone metastasis related proteins.

Detecting predictive androgen receptor modifications in circulating prostate cancer cells

Molecular modifications of the androgen receptor (AR) can cause resistance to androgen deprivation therapy (ADT) in prostate cancer patients. Since lack of representative tumor samples hinders therapy adjustments according to emerging AR-modifications, we evaluated simultaneous detection of the two most common AR modifications (AR-V7 splice variant and AR point mutations) in circulating tumor cells (CTCs). We devised a single-tube assay to detect AR-V7 splice variants and AR point mutations in CTCs using immunomagnetic cell isolation, followed by quantitative real-time PCR and DNA pyrosequencing. We prospectively investigated 47 patients with PSA progression awaiting therapy switch. Comparison of response to newly administered therapy and CTC-AR-status allowed effect size estimation. Nineteen (51%) of 37 patients with detectable CTCs carried AR-modifications. Seventeen patients carried the AR-V7 splice variant, one harbored a p.T878A point mutation and one harbored both AR-V7 and a p.H875Y mutation. We estimated a positive predictive value for response and non-response to therapy by AR status in CTCs of ~94%. Based on a conservative calculation, we estimated the effect size for molecularly-informed therapy switches for prospective clinical trial planning to ~27%. In summary, the ability to determine key resistance-mediating AR modifications in CTCs has the potential to considerably improve prostate cancer treatment.

Pharmacodynamic study of radium-223 in men with bone metastatic castration resistant prostate cancer

BACKGROUND

Radium-223 is a targeted alpha-particle therapy that improves survival in men with metastatic castration resistant prostate cancer (mCRPC), particularly in men with elevated serum levels of bone alkaline phosphatase (B-ALP). We hypothesized that osteomimicry, a form of epithelial plasticity leading to an osteoblastic phenotype, may contribute to intralesional deposition of radium-223 and subsequent irradiation of the tumor microenvironment.

METHODS

We conducted a pharmacodynamic study (NCT02204943) of radium-223 in men with bone mCRPC. Prior to and three and six months after radium-223 treatment initiation, we collected CTCs and metastatic biopsies for phenotypic characterization and CTC genomic analysis. The primary objective was to describe the impact of radium-223 on the prevalence of CTC B-ALP over time. We measured radium-223 decay products in tumor and surrounding normal bone during treatment. We validated genomic findings in a separate independent study of men with bone metastatic mCRPC (n = 45) and publicly accessible data of metastatic CRPC tissues.

RESULTS

We enrolled 20 men with symptomatic bone predominant mCRPC and treated with radium-223. We observed greater radium-223 radioactivity levels in metastatic bone tumor containing biopsies compared with adjacent normal bone. We found evidence of persistent Cellsearch CTCs and B-ALP (+) CTCs in the majority of men over time during radium-223 therapy despite serum B-ALP normalization. We identified genomic gains in osteoblast mimicry genes including gains of ALPL, osteopontin, SPARC, OB-cadherin and loss of RUNX2, and validated genomic alterations or increased expression at the DNA and RNA level in an independent cohort of 45 men with bone-metastatic CRPC and in 150 metastatic biopsies from men with mCRPC.

CONCLUSIONS

Osteomimicry may contribute in part to the uptake of radium-223 within bone metastases and may thereby enhance the therapeutic benefit of this bone targeting radiotherapy.

Androgen receptor nuclear localization correlates with AR-V7 mRNA expression in circulating tumor cells (CTCs) from metastatic castration resistance prostate cancer patients

Androgen receptor (AR) signaling drives prostate cancer (PC) progression and remains active upon transition to castration resistant prostate cancer (CRPC). Active AR signaling is achieved through the nuclear accumulation of AR following ligand binding and through expression of ligand-independent, constitutively active AR splice variants, such as AR-V7, which is the most commonly expressed variant in metastatic CRPC (mCRPC) patients. Most currently approved PC therapies aim to abrogate AR signaling and activity by inhibiting this ligand-mediated nuclear translocation. In a prospective multi-institutional clinical study, we recently showed that taxane based chemotherapy is also capable of impairing AR nuclear localization (ARNL) in circulating tumor cells (CTCs) from CRPC patients, whereas taxane induced decreases in ARNL were associated with response. Thus, quantitative assessment of ARNL in CTCs can be used to monitor therapeutic response in patients and help guide clinical decisions. Here, we describe the development and implementation of quantitative high throughput (QHT) image analysis algorithms to aid in CTC identification and quantitative assessment of percent ARNL (%ARNL). We applied this algorithm to fifteen CRPC patients at the start of taxane chemotherapy, quantified %ARNL in CTCs, and correlated with expression of AR-V7 mRNA (from CTCs enriched via negative, CD45⁺ depletion of peripheral blood) and with biochemical (prostate specific antigen; PSA) response to taxane chemotherapy. We found that CTCs from AR-V7 positive patients had higher baseline %ARNL compared to CTCs from AR-V7 negative patients, consistent with the constitutive nuclear localization of AR-V7. In addition, lower %ARNL in CTCs at baseline was associated with biochemical response to taxane chemotherapy. High inter- and intra-patient heterogeneity was also observed. As ARNL is required for active AR signaling, the QHT algorithms described herein can provide prognostic and/or predictive value in future clinical studies.

Influence of endocrine therapy on the ratio of androgen receptor (AR) to estrogen receptor (ER) positive circulating epithelial tumor cells (CETCs) in breast cancer

BACKGROUND

The androgen receptor (AR) is expressed in the majority of breast cancers and across the main breast cancer subtypes. Despite the high frequency of AR expression in breast cancer its appraisal remains controversial because its role is complex, dependent on the hormonal milieu. The aim of the current study was to investigate the frequency of AR and ER positive CETCs in breast cancer patients.

METHODS

The number of vital CETCs was determined from blood of 66 patients suffering from breast cancer and the expression of AR and ER on these cells was investigated using the maintrac method.

RESULTS

Numbers of CETCs/mL blood were significantly higher in patients with advanced disease as compared to patients with early stage disease. The fraction of AR positive CETCs was significantly higher than the fraction of ER positive CETCs (90% vs. 50%; P < 0.001). Patients with positive lymph nodes had less AR positive CETCs as compared to patients with negative lymph node status. The AR:ER ratio was higher in patients receiving tamoxifen therapy as compared to patients without tamoxifen therapy whereas treatment with aromatase inhibitor had no influence on AR:ER ratio.

CONCLUSIONS

The ratio of AR to ER positive CETCs, obviously, is influenced by endocrine therapy, more specifically therapy with tamoxifen. Since AR expression seems to be one of the possible mechanism of resistance to endocrine therapy this may provide a new biomarker to select patients who might benefit from combination treatment of ER and AR inhibitors.

Harnessing a Different Dependency: How to Identify and Target Androgen Receptor-Positive Versus Quadruple-Negative Breast Cancer

The androgen receptor (AR) is a promising therapeutic target for a subset of triple-negative breast cancers (TNBCs) in which AR is expressed. However, the mechanistic action of AR and the degree to which primary and metastatic tumors depend on AR, both before and after conventional treatment, remain to be defined. We discuss preclinical and clinical data for AR+ TNBC, the difficulties in monitoring AR protein levels, new methods for determining AR status, the influence of AR on "stemness" in the context of TNBC, the role of combined inhibition of sex steroid production and AR, and the role of AR in regulation of the immune system. Although the exact role of AR in subsets of TNBC is still being characterized, new therapies that target AR and the production of androgens may provide additional options for patients with TNBC for whom chemotherapy is currently the sole treatment option.

The evolution of chemotherapy for the treatment of prostate cancer

Chemotherapy has been explored as a treatment option for metastatic prostate cancer since the early 1980s. Docetaxel, a taxane chemotherapeutic, was approved for the treatment of men with metastatic castration-resistant prostate cancer in 2004, and is now standard of care for late stage disease. Recent clinical studies demonstrated that patients with metastatic castration-sensitive disease, and possibly those with high-risk localized prostate cancer also benefit from docetaxel administration, expanding the role of chemotherapy in the prostate cancer treatment landscape. Another taxane, cabazitaxel, is approved for post-docetaxel metastatic castration-resistant prostate cancer. Taxanes and other chemotherapeutics, such as carboplatin, are now being tested in combination regimens. This review presents an outline of recent and ongoing clinical studies assessing docetaxel and its derivative cabazitaxel at different stages of the disease, and in various combinations with other agents. We summarize current knowledge on biomarkers predictive of response to chemotherapy, which may in future be used to guide individualized treatment decisions.

Androgen receptor expression on circulating tumor cells in metastatic breast cancer

Purpose

Methods

Results

Conclusions

Using circulating tumor cells to advance precision medicine in prostate cancer

The field of CTC enrichment has seen many emerging technologies in recent years, which have resulted in the identification and monitoring of clinically relevant, CTC-based biomarkers that can be analyzed routinely without invasive procedures. Several molecular platforms have been used to investigate the molecular profile of the disease, from high throughput gene expression analyses down to single cell biological dissection. The established presence of CTC heterogeneity nevertheless constitutes a challenge for cell isolation as the several subpopulations can potentially display different molecular characteristics; in this scenario, careful consideration must be given to the isolation approach, whereas methods that discriminate against certain subpopulations may result in the exclusion of CTCs that carry biological relevance. In the context of prostate cancer (PC), CTC molecular interrogation can enable longitudinal monitoring of key biological features during treatment with substantial clinical impact, as several biomarkers could predict tumor response to AR signaling inhibitors (abiraterone, enzalutamide) or standard chemotherapy (taxanes). Thus, CTCs represent a valuable opportunity to personalize medicine in current clinical practice.

Circulating tumor cells in prostate cancer: Precision diagnosis and therapy

The primary cause of tumor-associated mortality in prostate cancer (PCa) remains distant metastasis. The dissemination of tumor cells from the primary tumor to distant sites through the bloodstream cannot be detected early by standard imaging methods. Circulating tumor cells (CTCs) represent an effective prognostic and predictive biomarker, which are able to monitor efficacy of adjuvant therapies, detect early development of metastases, and finally, assess therapeutic responses of advanced disease earlier than traditional diagnostic methods. In addition, since repeated tissue biopsies are invasive, costly and not always feasible, the assessment of tumor characteristics on CTCs, by a peripheral blood sample as a liquid biopsy, represents an attractive opportunity. The implementation of molecular and genomic characterization of CTCs may contribute to improve the treatment selection and thus, to move toward more precise diagnosis and therapy in PCa. The present study summarizes the current advances in CTC enrichment and detection strategies and reviews how CTCs may contribute to significant insights in the metastatic process, as well as how they may be utilized in clinical application in PCa. Although it is proposed that CTCs may offer insights into the prognosis and management of PCa, there are a number of challenges in the study of circulating tumor cells, and their clinical utility remains under investigation.

Circulating tumor cells capture disease evolution in advanced prostate cancer

Background

Genetic analysis of advanced cancer is limited by availability of representative tissue. Biopsies of prostate cancer metastasized to bone are invasive with low quantity of tumor tissue. The prostate cancer genome is dynamic, however, with temporal heterogeneity requiring repeated evaluation as the disease evolves. Circulating tumor cells (CTCs) offer an alternative, “liquid biopsy”, though single CTC sequencing efforts are laborious with high failure rates.

Methods

We performed exome sequencing of matched treatment-naïve tumor tissue, castrate resistant tumor tissue, and pooled CTC samples, and compared mutations identified in each.

Results

Thirty-seven percent of CTC mutations were private to CTCs, one mutation was shared with treatment-naïve disease alone, and 62% of mutations were shared with castrate-resistant disease, either alone or with treatment-naïve disease. An acquired nonsense mutation in the Retinoblastoma gene, which is associated with progression to small cell cancer, was identified in castrate resistant and CTC samples, but not treatment-naïve disease. This timecourse correlated with the tumor acquiring neuroendocrine features and a change to neuroendocrine-specific therapy.

Conclusions

These data support the use of pooled CTCs to facilitate the genetic analysis of late stage prostate cancer.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-017-1138-3) contains supplementary material, which is available to authorized users.

Circulating Tumor Cells in Genitourinary Malignancies: An Evolving Path to Precision Medicine

Precision medicine with molecularly directed therapeutics is rapidly expanding in all subspecialties of oncology. Molecular analysis and treatment monitoring require tumor tissue, but resections or biopsies are not always feasible due to tumor location, patient safety, and cost. Circulating tumor cells (CTCs) offer a safe, low-cost, and repeatable tissue source as an alternative to invasive biopsies. "Liquid biopsies" can be collected from a peripheral blood draw and analyzed to isolate, enumerate, and molecularly characterize CTCs. While there is deserved excitement surrounding new CTC technologies, studies are ongoing to determine whether these cells can provide reliable and accurate information about molecular drivers of cancer progression and inform treatment decisions. This review focuses on the current status of CTCs in genitourinary (GU) cancer. We will review currently used methodologies to isolate and detect CTCs, their use as predictive biomarkers, and highlight emerging research and applications of CTC analysis in GU malignancies.

Strategies for Isolation and Molecular Profiling of Circulating Tumor Cells

Cancer is the leading cause of death by disease worldwide, and metastasis is responsible for more than 90% of the mortality of cancer patients. Metastasis occurs when tumor cells leave the primary tumor, travel through the blood stream as circulating tumor cells (CTCs), and then colonize secondary tumors at sites distant from the primary tumor. The capture, identification, and analysis of CTCs offer both scientific and clinical benefits. On the scientific side, the analysis of CTCs could help elucidate possible genetic alterations and signaling pathway aberrations during cancer progression, which could then be used to find new methods to stop cancer progression. On the clinical side, non-invasive testing of a patient's blood for CTCs can be used for patient diagnosis and prognosis, as well as subsequent monitoring of treatment efficacy in routine clinical practice. Additionally, investigation of CTCs early in the progression of cancer may reveal targets for initial cancer detection and for anti-cancer treatment. This chapter will evaluate strategies and devices used for the isolation and identification of CTCs directly from clinical samples of blood. Recent progress in the understanding of the significance of both single CTCs and circulating tumor microemboli will be discussed. Also, advancements in the use of CTC-based liquid biopsy in clinical diagnosis and the potential of CTC-based molecular characterization for use in clinical applications will be summarized.

Multi-Phenotypic subtyping of circulating tumor cells using sequential fluorescent quenching and restaining

In tissue biopsies formalin fixed paraffin embedded cancer blocks are micro-sectioned producing multiple semi-identical specimens which are analyzed and subtyped proteomically, and genomically, with numerous biomarkers. In blood based biopsies (BBBs), blood is purified for circulating tumor cells (CTCs) and clinical utility is typically limited to cell enumeration, as only 2–3 positive fluorescent markers and 1 negative marker can be used. As such, increasing the number of subtyping biomarkers on each individual CTC could dramatically enhance the clinical utility of BBBs, allowing in depth interrogation of clinically relevant CTCs. We describe a simple and inexpensive method for quenching the specific fluors of fluorescently stained CTCs followed by sequential restaining with additional biomarkers. As proof of principle a CTC panel, immunosuppression panel and stem cell panel were used to sequentially subtype individual fluorescently stained patient CTCs, suggesting a simple and universal technique to analyze multiple clinically applicable immunomarkers from BBBs.

Integrated Analysis of Multiple Biomarkers from Circulating Tumor Cells Enabled by Exclusion-Based Analyte Isolation

PURPOSE

There is a critical clinical need for new predictive and pharmacodynamic biomarkers that evaluate pathway activity in patients treated with targeted therapies. A microscale platform known as VERSA (versatile exclusion-based rare sample analysis) was developed to integrate readouts across protein, mRNA, and DNA in circulating tumor cells (CTC) for a comprehensive analysis of the androgen receptor (AR) signaling pathway.

EXPERIMENTAL DESIGN

Utilizing exclusion-based sample preparation principles, a handheld chip was developed to perform CTC capture, enumeration, quantification, and subcellular localization of proteins and extraction of mRNA and DNA. This technology was validated across integrated endpoints in cell lines and a cohort of patients with castrate-resistant prostate cancer (CRPC) treated with AR-targeted therapies and chemotherapies.

RESULTS

The VERSA was validated in cell lines to analyze AR protein expression, nuclear localization, and gene expression targets. When applied to a cohort of patients, radiographic progression was predicted by the presence of multiple AR splice variants and activity in the canonical AR signaling pathway. AR protein expression and nuclear localization identified phenotypic heterogeneity. Next-generation sequencing with the FoundationOne panel detected copy number changes and point mutations. Longitudinal analysis of CTCs identified acquisition of multiple AR variants during targeted treatments and chemotherapy.

CONCLUSIONS

Complex mechanisms of resistance to AR-targeted therapies, across RNA, DNA, and protein endpoints, exist in patients with CRPC and can be quantified in CTCs. Interrogation of the AR signaling pathway revealed distinct patterns relevant to tumor progression and can serve as pharmacodynamic biomarkers for targeted therapies. Clin Cancer Res; 1-11. ©2016 AACR.

A cell transportation solution that preserves live circulating tumor cells in patient blood samples

Background

Circulating tumor cells (CTCs) are typically collected into CellSave fixative tubes, which kills the cells, but preserves their morphology. Currently, the clinical utility of CTCs is mostly limited to their enumeration. More detailed investigation of CTC biology can be performed on live cells, but obtaining live CTCs is technically challenging, requiring blood collection into biocompatible solutions and rapid isolation which limits transportation options. To overcome the instability of CTCs, we formulated a sugar based cell transportation solution (SBTS) that stabilizes cell viability at ambient temperature. In this study we examined the long term viability of human cancer cell lines, primary cells and CTCs in human blood samples in the SBTS for transportation purposes.

Methods

Four cell lines, 5 primary human cells and purified human PBMCs were tested to determine the viability of cells stored in the transportation solution at ambient temperature for up to 7 days. We then demonstrated viability of MCF-7 cells spiked into normal blood with SBTS and stored for up to 7 days. A pilot study was then run on blood samples from 3 patients with metastatic malignancies stored with or without SBTS for 6 days. CTCs were then purified by Ficoll separation/microfilter isolation and identified using CTC markers. Cell viability was assessed using trypan blue or CellTracker™ live cell stain.

Results

Our results suggest that primary/immortalized cell lines stored in SBTS remain ~90 % viable for > 72 h. Further, MCF-7 cells spiked into whole blood remain viable when stored with SBTS for up to 7 days. Finally, live CTCs were isolated from cancer patient blood samples kept in SBTS at ambient temperature for 6 days. No CTCs were isolated from blood samples stored without SBTS.

Conclusions

In this proof of principle pilot study we show that viability of cell lines is preserved for days using SBTS. Further, this solution can be used to store patient derived blood samples for eventual isolation of viable CTCs after days of storage. Therefore, we suggest an effective and economical transportation of cancer patient blood samples containing live CTCs can be achieved.

The use of circulating tumor cells in guiding treatment decisions for patients with metastatic castration-resistant prostate cancer

The therapeutic landscape of metastatic castration-resistant prostate cancer (mCRPC) has drastically changed over the past decade with the advent of several new anti-tumor agents. Oncologists increasingly face dilemmas concerning the best treatment sequence for individual patients since most of the novel compounds have been investigated and subsequently positioned either pre- or post-docetaxel. A currently unmet need exists for biomarkers able to guide treatment decisions and to capture treatment resistance at an early stage thereby allowing for an early change to an alternative strategy. Circulating tumor cells (CTCs) have in this context intensively been investigated over the last years. The CTC count, as determined by the CellSearch System (Janssen Diagnostics LLC, Raritan, NJ), is a strong, independent prognostic factor for overall survival in patients with mCRPC at various time points during treatment and, as an early response marker, outperforms traditional response evaluations using serum prostate specific antigen (PSA) levels, scintigraphy as well as radiography. The focus of research is now shifting toward the predictive value of CTCs and the use of the characterization of CTCs to guide the selection of treatments with the highest chance of success for individual patients. Recently, the presence of the androgen receptor splice variant 7 (AR-V7) has been shown to be a promising predictive factor. In this review, we have explored the clinical value of the enumeration and characterization of CTCs for the treatment of mCRPC and have put the results obtained from recent studies investigating the prognostic and predictive value of CTCs into clinical perspective.

Toward Intraoperative Detection of Disseminated Tumor Cells in Lymph Nodes with Silicon Nanowire Field Effect Transistors

Within an hour, as little as one disseminated tumor cell (DTC) per lymph node can be quantitatively detected using an intraoperative biosensing platform based on silicon nanowire field-effect transistors (SiNW FET). It is also demonstrated that the integrated biosensing platform is able to detect the presence of circulating tumor cells (CTCs) in the blood of colorectal cancer patients. The presence of DTCs in lymph nodes and CTCs in peripheral blood is highly significant as it is strongly associated with poor patient prognosis. The SiNW FET sensing platform out-performed in both sensitivity and rapidity not only the current standard method based on pathological examination of tissue sections but also the emerging clinical gold standard based on molecular assays. The possibility to achieve accurate and highly sensitive analysis of the presence of DTCs in the lymphatics within the surgery time frame has the potential to spare cancer patients from an unnecessary secondary surgery, leading to reduced patient morbidity, improving their psychological wellbeing and reducing time spent in hospital. This study demonstrates the potential of nanoscale field-effect technology in clinical cancer diagnostics.

Acquisition of Portal Venous Circulating Tumor Cells From Patients With Pancreaticobiliary Cancers by Endoscopic Ultrasound

BACKGROUND & AIMS

Tumor cells circulate in low numbers in peripheral blood; their detection is used predominantly in metastatic disease. We evaluated the feasibility and safety of sampling portal venous blood via endoscopic ultrasound (EUS) to count portal venous circulating tumor cells (CTCs), compared with paired peripheral CTCs, in patients with pancreaticobiliary cancers (PBCs).

METHODS

In a single-center cohort study, we evaluated 18 patients with suspected PBCs. Under EUS guidance, a 19-gauge EUS fine needle was advanced transhepatically into the portal vein and as many as four 7.5-mL aliquots of blood were aspirated. Paired peripheral blood samples were obtained. Epithelial-derived CTCs were sorted magnetically based on expression of epithelial cell adhesion molecules; only those with a proper morphology and found to be CD45 negative and positive for cytokeratins 8, 18, and/or 19 and 4',6-diamidino-2-phenylindole were considered to be CTCs. For 5 samples, CTCs also were isolated by flow cytometry and based on CD45 depletion. ImageStream was used to determine the relative protein levels of P16, SMAD4, and P53. DNA was extracted from CTCs for sequencing of select KRAS codons.

RESULTS

There were no complications from portal vein blood acquisition. We detected CTCs in portal vein samples from all 18 patients (100%) vs peripheral blood samples from only 4 patients (22.2%). Patients with confirmed PBCs had a mean of 118.4 ± 36.8 CTCs/7.5 mL portal vein blood, compared with a mean of 0.8 ± 0.4 CTCs/7.5 mL peripheral blood (P < .01). The 9 patients with nonmetastatic, resectable, or borderline-resectable PBCs had a mean of 83.2 CTCs/7.5 mL portal vein blood (median, 62.0 CTCs/7.5 mL portal vein blood). In a selected patient, portal vein CTCs were found to carry the same mutations as those detected in a metastatic lymph node and expressed similar levels of P16, SMAD4, and P53 proteins.

CONCLUSIONS

It is feasible and safe to collect portal venous blood from patients undergoing EUS. We identified CTCs in all portal vein blood samples from patients with PBCs, but less than 25% of peripheral blood samples. Portal vein CTCs can be used for molecular characterization of PBCs and share features of metastatic tissue. This technique might be used to study the pathogenesis and progression of PBCs, as well as a diagnostic or prognostic tool to stratify risk of cancer recurrence or developing metastases.

Detection and Clinical Significance of Circulating Tumor Cells in Colorectal Cancer--20 Years of Progress

Circulating tumor cells (CTC) may be defined as tumor- or metastasis-derived cells that are present in the bloodstream. The CTC pool in colorectal cancer (CRC) patients may include not only epithelial tumor cells, but also tumor cells undergoing epithelial-mesenchymal transition (EMT) and tumor stem cells. A significant number of patients diagnosed with early stage CRC subsequently relapse with recurrent or metastatic disease despite undergoing "curative" resection of their primary tumor. This suggests that an occult metastatic disease process was already underway, with viable tumor cells being shed from the primary tumor site, at least some of which have proliferative and metastatic potential and the ability to survive in the bloodstream. Such tumor cells are considered to be responsible for disease relapse in these patients. Their detection in peripheral blood at the time of diagnosis or after resection of the primary tumor may identify those early-stage patients who are at risk of developing recurrent or metastatic disease and who would benefit from adjuvant therapy. CTC may also be a useful adjunct to radiological assessment of tumor response to therapy. Over the last 20 years many approaches have been developed for the isolation and characterization of CTC. However, none of these methods can be considered the gold standard for detection of the entire pool of CTC. Recently our group has developed novel unbiased inertial microfluidics to enrich for CTC, followed by identification of CTC by imaging flow cytometry. Here, we provide a review of progress on CTC detection and clinical significance over the last 20 years.

Targeting the glucocorticoid receptor in breast and prostate cancers

Steroid receptors for androgens and estrogens have essential roles in prostate and breast cancers. Recently, glucocorticoid receptor (GR) activity has also been proposed as having an important role in these cancers. Underscoring the cooperative nature of nuclear receptor activity, data now suggest that GR function in prostate and breast cancers is dependent on the tumor's concomitant androgen or estrogen receptor activity.

Molecular analysis of CD133-positive circulating tumor cells from patients with metastatic castration-resistant prostate cancer

The function and clinical utility of stem cell markers in metastatic castration-resistant prostate cancer (mCRPC) remains unresolved, and their expression may confer important therapeutic opportunities for staging and therapy. In the adult human prostate, CD133 (PROM1) expression identifies infrequent prostate epithelial progenitor cells and putative cancer stem cells. Previous work demonstrated an association with CD133 and cancer cell proliferation using in vitro model systems. The primary objective here was to investigate the expression of CD133 in circulating tumor cells (CTCs) from patients with mCRPC and to test the hypothesis that patients with mCRPC had CD133-positive CTCs associated with increased cell proliferation, changes in the androgen receptor (AR) protein expression, or AR nuclear co-localization. We utilized ImageStreamX technology, which combines flow cytometry and fluorescence microscopy, to capture and analyze CD45-negative/EpCAM-positive CTCs for CD133, Ki-67, and AR. All patient samples (20/20) contained CD133-positive populations of CTCs, and on average 50.9 ± 28.2% (range of 18.2% to 100%) of CTCs were CD133-positive. CD133-positive CTCs have increased Ki-67 protein expression compared to CD133-negative CTCs, implying that CD133-positive CTCs may have greater proliferative potential when compared to their CD133-negative counterparts. CD133-positive and CD133-negative CTCs have similar levels of AR protein expression and cellular co-localization with nuclear markers, implying that CD133 expression is independent of AR pathway activity and an AR-independent marker of mCRPC proliferation. These studies demonstrate the presence of CD133-positive populations in CTCs from mCRPC with increased proliferative potential.

PLCε knockdown inhibits prostate cancer cell proliferation via suppression of Notch signalling and nuclear translocation of the androgen receptor

Phospholipase Cε (PLCε), a key regulator of diverse cellular functions, has been implicated in various malignancies. Indeed, PLCε functions include cell proliferation, apoptosis and malignant transformation. Here, we show that PLCε expression is elevated in prostate cancer (PCa) tissues compared to benign prostate tissues. Furthermore, PLCε depletion using an adenovirally delivered shRNA significantly decreased cell growth and colony formation, arresting the PC3 and LNCaP cell lines in the S phase of the cell cycle. We also observed that PLCε was significantly correlated with Notch1 and androgen receptor (AR). Additionally, we demonstrate that the activation of both the Notch and AR signalling pathways is involved in PLCε-mediated oncogenic effects in PCa. Our findings suggest that PLCε is a putative oncogene and prognostic marker, potentially representing a novel therapeutic target for PCa.