Molecular assays for the detection of prostate tumor derived nucleic acids in peripheral blood

Monitoring circulating prostate cancer cells by in vivo flow cytometry assesses androgen deprivation therapy on metastasis

It remains controversial whether surgical castration prolongs survival rate and improves therapy prospects in patients suffering from prostate cancer. We used PC3 cell line to establish prostate tumor models. In vivo flow cytometry and ultrasonic imaging were used to monitor the process of prostate cancer growth, development and metastasis. We found out that the number of circulating tumor cells (CTCs) in orthotopic tumor model was higher than that in subcutaneous tumor model. The CTC number in orthotopic tumor model was due to burst growth, while CTC number in subcutaneous tumor model showed a gradual increase with tumor size. After androgen deprivation therapy (ADT) through testicular extraction, we constructed GFP-PC3 subcutaneous tumor models and orthotopic tumor models. We found dramatically decreased CTC number, relieved symptoms caused by the tumor, and significantly prolonged survival time after testicular extraction in orthotopically transplanted prostate tumor model, while the carcinogenesis process and metastases were little influenced by ADT in subcutaneous tumor model. ADT treatment can restrict tumor growth, decrease the CTC number significantly and inhibit distant invasion through inhibition of tumor proliferation and tumor angiogenesis in orthotopical prostate tumor model. © 2018 International Society for Advancement of Cytometry.

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.

KLK3, PCA3, and TMPRSS2-ERG expression in the peripheral blood mononuclear cell fraction from castration-resistant prostate cancer patients and response to docetaxel treatment

BACKGROUND

To monitor systemic disease activity, the potential of circulating tumor cells (CTCs) bears great promise. As surrogate for CTCs we measured KLK3, PCA3, and TMPRSS2-ERG messenger RNA (mRNA) in the peripheral blood mononuclear cell (PBMC) fraction from a castration-resistant prostate cancer (CRPC) patient cohort and three control groups. Moreover, biomarker response to docetaxel treatment was evaluated in the patient group.

METHODS

Blood samples from 20 CRPC patients were analyzed at four different time points (prior to docetaxel treatment, at 9 weeks, 27 weeks, and 2 months after treatment). Blood was drawn once from three control groups (10 age-matched men, 10 men under 35 years of age, 12 women). All samples were analyzed for KLK3, PCA3, and TMPRSS2-ERG mRNA by using a quantitative nucleic acid amplification assay with gene-specific primers in the complementary DNA synthesis.

RESULTS

At baseline, mRNA for KLK3 was detected in 17 (89%, 95% CI 76-100%), PCA3 in 10 (53%, 95% CI 30-75%), and TMPRSS2-ERG in seven of 19 evaluable patients (37%, 95% CI 15-59%). In contrast, the blood samples from all 32 healthy volunteers were reproducible negative for all markers. In response to docetaxel treatment, KLK3 levels decreased in 80% (95% CI 60-100%), PCA3 in 89% (95% CI 68-100%), and TMPRSS2-ERG in 86% (95% CI 60-100%) of patients.

CONCLUSIONS

The feasibility of a highly sensitive modified nucleic acid amplification assay to assess KLK3, PCA3, and TMPRSS2-ERG mRNA in the PBMC fraction from CRPC patients was demonstrated. Moreover, response of these markers to systemic treatment was shown.

Epithelial cell adhesion molecule (EpCAM) is associated with prostate cancer metastasis and chemo/radioresistance via the PI3K/Akt/mTOR signaling pathway

Prostate cancer (CaP) is the second leading malignancy in men. The role of epithelial cell adhesion molecule (EpCAM), also known as CD326, in CaP progression and therapeutic resistance is still uncertain. Here, we aimed to investigate the roles of EpCAM in CaP metastasis and chemo/radioresistance. Expression of EpCAM in CaP cell lines and human CaP tissues was assessed using immunofluorescence and immunohistochemistry, respectively. EpCAM was knocked down (KD) in PC-3, DU145 and LNCaP-C4-2B cells using small interfering RNA (siRNA), and KD results were confirmed by confocal microscope, Western blotting and quantitative real time polymerase chain reaction (qRT-PCR). Cell growth was evaluated by proliferation and colony formation assays. The invasive potential was assessed using a matrigel chamber assay. Tumorigenesis potential was measured by a sphere formation assay. Chemo-/radiosensitivity were measured using a colony formation assay. Over-expression of EpCAM was found in primary CaP tissues and lymph node metastases including cancer cells and surrounding stromal cells. KD of EpCAM suppressed CaP proliferation and invasive ability, reduced sphere formation, enhanced chemo-/radiosensitivity, and down-regulated E-cadherin, p-Akt, p-mTOR, p-4EBP1 and p-S6K expression in CaP cells. Our findings suggest that EpCAM plays an important role in CaP proliferation, invasion, metastasis and chemo-/radioresistance associated with the activation of the PI3K/Akt/mTOR signaling pathway and is a novel therapeutic target to sensitize CaP cells to chemo-/radiotherapy.

Prostate cancer antigen 3 (PCA3) RNA detection in blood and tissue samples for prostate cancer diagnosis

BACKGROUND

The non-coding prostate cancer antigen 3 (PCA3) RNA is currently the most specific biomarker for prostate cancer (PCa) diagnosis. Although its clinical value has been validated in a urine assay after intensive prostatic massage, few studies have been conducted to establish its diagnostic value in the peripheral blood (PBL). The aim of the present study was to examine the PCA3 expression in blood as a diagnostic tool, and to provide an additional strategy to improve PCa diagnosis.

METHODS

PCA3 transcripts were detected by RT-PCR in PBL and prostatic tissues from patients. PBL sampling also included a group of young healthy volunteers. The relationship between the PCA3 RNA detection and clinical characteristics was analyzed.

RESULTS

PCA3 detection in blood presented 94% specificity and 32% sensitivity, and its combined detection in tissues significantly improved diagnostic parameters. However, PCA3 RNA detection in blood was also associated with PSA levels ≥10 ng/mL, and their combination provided a sensitivity of 60% and specificity of 93%.

CONCLUSIONS

Detection of the PCA3 RNA in patients' blood is an efficient tool for PCa diagnosis because it allows a routine collection procedure, which is also supported by the ongoing screening marker, prostate-specific antigen (PSA). We propose its combined use with PSA levels ≥10 ng/mL, which improves accuracy, and prevents overdiagnosis and overtreatment.

Role of the EpCAM (CD326) in prostate cancer metastasis and progression

Despite significant advances in surgery, radiotherapy and chemotherapy to treat prostate cancer (CaP), many patients die of secondary disease (metastases). Current therapeutic approaches are limited, and there is no cure for metastatic castration-resistant prostate cancer (CRPC). Epithelial cell adhesion molecule (EpCAM, also known as CD326) is a transmembrane glycoprotein that is highly expressed in rapidly proliferating carcinomas and plays an important role in the prevention of cell-cell adhesion, cell signalling, migration, proliferation and differentiation. Stably and highly expressed EpCAM has been found in primary CaP tissues, effusions and CaP metastases, making it an ideal candidate of tumour-associated antigen to detect metastasis of CaP cells in the circulation as well as a promising therapeutic target to control metastatic CRPC disease. In this review, we discuss the implications of the newly identified roles of EpCAM in terms of its diagnostic and metastatic relevance to CaP. We also summarize EpCAM expression in human CaP and EpCAM-mediated signalling pathways in cancer metastasis. Finally, emerging and innovative approaches to the management of the disease and expanding potential therapeutic applications of EpCAM for targeted strategies in future CaP therapy will be explored.

Isolation and characterization of circulating tumor cells in prostate cancer

Circulating tumor cells (CTCs) are tumor cells found in the peripheral blood that putatively originate from established sites of malignancy and likely have metastatic potential. Analysis of CTCs has demonstrated promise as a prognostic marker as well as a source of identifying potential targets for novel therapeutics. Isolation and characterization of these cells for study, however, remain challenging owing to their rarity in comparison with other cellular components of the peripheral blood. Several techniques that exploit the unique biochemical properties of CTCs have been developed to facilitate their isolation. Positive selection of CTCs has been achieved using microfluidic surfaces coated with antibodies against epithelial cell markers or tumor-specific antigens such as EpCAM or prostate-specific membrane antigen (PSMA). Following isolation, characterization of CTCs may help guide clinical decision making. For instance, molecular and genetic characterization may shed light on the development of chemotherapy resistance and mechanisms of metastasis without the need for a tissue biopsy. This paper will review novel isolation techniques to capture CTCs from patients with advanced prostate cancer, as well as efforts to characterize the CTCs. We will also review how these analyzes can assist in clinical decision making.

CONCLUSION

The study of CTCs provides insight into the molecular biology of tumors of prostate origin that will eventually guide the development of tailored therapeutics. These advances are predicated on high yield and accurate isolation techniques that exploit the unique biochemical features of these cells.

Phase II study of cytarabine in men with docetaxel-refractory, castration-resistant prostate cancer with evaluation of TMPRSS2-ERG and SPINK1 as serum biomarkers

What's known on the subject? and What does the study add? To date, there has been limited impetus to examine the use of cytarabine in prostate cancer. We presented preliminary laboratory data to suggest its utility in the castration refractory prostate cancer (CRPC) population which, combined with a previous case report, suggested it may have hitherto unrecognized utility in this setting. Embedded in this study was peripheral blood sampling for TMPRSS2-ERG and SPINK1, two genes that are believed to define prostate cancer genotypes, to assess their utility as biomarkers This study suggests that at the delivered doses, cytarabine has limited efficacy and significant myelotoxicity suggesting, it does not have a role in the treatment of docetaxel-refractory CRPC. The presence of serum TMPRSS2-ERG and SPINK1 mRNA biomarkers recovered from blood suggest that their analysis is worthy of further study.

OBJECTIVES

To run a phase II clinical trial of cytarabine in men with docetaxel-refractory, castration-resistant prostate cancer (CRPC), based on evidence that cytarabine might be effective in men with abnormalities of ERG oncogenes. To measure mRNA levels of prostate cancer-related genes in blood as biomarkers.

PATIENTS AND METHODS

Ten of a planned maximum of 30 men received i.v. cytarabine at doses of 0.25-1g/m(2) at 21-day intervals. The primary endpoint was prostate-specific antigen (PSA) response. Archival tumour samples were assessed by fluorescence in-situ hybridization for TMPRSS2:ERG translocation, and by immunohistochemistry for serine peptidase inhibitor Kazal type 1 (SPINK1). Blood was processed for mRNA quantification of TMPRSS2:ERG (exon1:exon4), SPINK1 and PSA.

RESULTS

A PSA response was not observed in any patient. The trial was stopped at the end of stage 1 of a modified Flemming design. The median number of cycles administered was 3. Grade 3-4 haematological toxicity was common. Five patients were subsequently excluded from the study for toxicity, and five for disease progression. Analysis of whole blood mRNA for T1:E4 translocation in TMPRSS2:ERG was consistent with that in the tumour in 8/9 evaluable cases (one was concordantly positive, seven were concordantly negative), SPINK1 results were concordant in 9/10 cases (two were concordantly positive, seven were concordantly negative [P = 0.047 for the predictive value]). There was no correlation between PSA or SPINK protein and their respective mRNA copy levels in blood.

CONCLUSIONS

Cytarabine at the doses used is ineffective for men with CRPC. Blood mRNA levels of prostate cancer genes may represent a novel aspect of monitoring prostate cancer and have implications for the understanding of tumour-derived mRNA.

Immunomagnetic separation technologies

The largest difficulty one faces in the development of technology for detection of circulating tumor cells (CTCs) is whether or not tumor cells are present in the blood and at what frequency. Although the introduction of the validated CellSearch system for CTC enumeration has facilitated CTC research the question remains whether CTC are missed or whether the CTC that are reported are indeed clinically relevant. To fulfill the promise of CTC as a real-time liquid biopsy they will need to be present in the blood volume tested and need to be isolated without losing the ability to test the presence of treatment targets. To characterize a sufficiently large number of CTCs in the majority of cancer patients the volume of blood needed is simply too large to process without enrichment prior to detection. Here, we review the detection of CTCs by flow cytometry and fluorescence microscopy with and without immunomagnetic enrichment.

Nanoresonator chip-based RNA sensor strategy for detection of circulating tumor cells: response using PCA3 as a prostate cancer marker

There is widespread interest in circulating tumor cells (CTCs) in blood. Direct detection of CTCs (often < 1/mL) is complicated by a number of factors, but the presence of ∼10(3) to 10(4) copies of target RNA per CTC, coupled with simple enrichments, can greatly increase detection capability. In this study we used resonance frequency shifts induced by mass-amplifying gold nanoparticles to detect a hybridization sandwich bound to functionalized nanowires. We selected PCA3 RNA as a marker for prostate cancer, optimized antisense binding sites, and defined conditions allowing single nucleotide mismatch discrimination, and used a hybrid resonator integration scheme, which combines elements of top-down fabrication with strengths of bottom-up fabrication, with a view to enable multiplexed sensing. Bound mass calculated from frequency shifts matched mass estimated by counting gold nanoparticles. This represents the first demonstration of use of such nanoresonators, which show promise of both excellent specificity and quantitative sensitivity.

Contemporary role of prostate cancer antigen 3 in the management of prostate cancer

CONTEXT

Newly discovered biomarkers ideally should prove clinical usefulness, provide additional detection, staging, and prognosis information to improve individual risk assessment, and potentially permit targeted cancer therapy.

OBJECTIVE

To review, display, and evaluate the current evidence regarding the biologic and analytic approach of urinary prostate cancer gene 3 (PCA3) in prostate cancer (PCa) detection, staging, and prognosis, and its therapeutic potential.

EVIDENCE ACQUISITION

A systematic and comprehensive Medline search was performed using the Medical Subject Headings search terms PCA3, DD3, UPM3, prostate cancer, cell-lines, prostate tissue, prostate biopsy, detection, diagnosis, radical prostatectomy, staging, grading, progression, and gene therapy. Results were restricted to English-language papers published within the period 1999-2011.

EVIDENCE SYNTHESIS

The PCA3 gene is highly overexpressed in specific PCa cell lines and prostatic tumours. In 2006, a simple and robust urine test (Progensa) became commercially available. Despite its costs, prostate cancer antigen 3 (PCA3) is superior to prostate-specific antigen (PSA) and percent free PSA in the early detection of PCa. PCA3 improves the diagnostic accuracy of externally validated nomograms among men with an elevated PSA undergoing biopsy. PCA3 independently predicts low-volume disease and pathologically insignificant PCa but is not associated with locally advanced disease and is limited in the prediction of aggressive cancer. Preliminary data demonstrate that combining PCA3 with other new biomarkers further improves diagnostic and prognostic accuracy. Finally, findings of the first PCA3-Gene-ViroTherapy study suggest therapeutic potential by exploiting PCA3 overexpression.

CONCLUSIONS

PCA3, integrated in novel biopsy nomograms or risk stratification tools, can be used to counsel or confirm biopsy indications. If confirmed in further studies, using PCA3 together with established staging risk factors could assist clinicians in specific pretreatment decision making. So far no evidence for the usefulness of PCA3 in active surveillance programs has been presented.