Human prostate side population cells demonstrate stem cell properties in recombination with urogenital sinus mesenchyme

Redox-Regulation in Cancer Stem Cells

Cancer stem cells (CSCs) represent a small subset of slowly dividing cells with tumor-initiating ability. They can self-renew and differentiate into all the distinct cell populations within a tumor. CSCs are naturally resistant to chemotherapy or radiotherapy. CSCs, thus, can repopulate a tumor after therapy and are responsible for recurrence of disease. Stemness manifests itself through, among other things, the expression of stem cell markers, the ability to induce sphere formation and tumor growth in vivo, and resistance to chemotherapeutics and irradiation. Stemness is maintained by keeping levels of reactive oxygen species (ROS) low, which is achieved by enhanced activity of antioxidant pathways. Here, cellular sources of ROS, antioxidant pathways employed by CSCs, and underlying mechanisms to overcome resistance are discussed.

Role of prostate stem cells and treatment strategies in benign prostate hyperplasia

Benign prostate hyperplasia (BPH) is a progressive disease with a direct correlation between incidence and age. Since the treatment and management of BPH involve harmful side effects and decreased quality of life for the patient, the primary focus of research should be to find better and longer-lasting therapeutic options. The mechanisms regulating prostate stem cells in development can be exploited to decrease prostate growth. BPH is defined as the overgrowth of the prostate, and BPH is often diagnosed when lower urinary tract symptoms (LUTS) of urine storage or voiding symptoms cause patients to seek treatment. While multiple factors are involved in the hyperplastic growth of the stromal and epithelial compartments of the prostate, the clonal proliferation of stem cells is considered one of the main reasons for BPH initiation and regrowth of the prostate after therapies for BPH fail. Several theories explain possible reasons for the involvement of stem cells in the development, progression, and pathogenesis of BPH. The aim of the current review is to discuss current literature on the fundamentals of prostate development and the role of stem cells in BPH. This review examines the rationale for the hypothesis that unregulated stem cell properties can lead to BPH and therapeutic targeting of stem cells may reduce treatment-related side effects and prevent the regrowth of the prostate.

Current experimental human tissue-derived models for prostate cancer research

Scientists engaged in prostate cancer research have been conducting experiments using two-dimensional cultures of prostate cancer cell lines for decades. However, these experiments fail to reproduce and reflect the clinical course of individual patients with prostate cancer, or the molecular and genetic characteristics of prostate cancer, the basic requirement for most of the preclinical studies on prostate cancer. The use of human prostate cancer tissues in experiments has enabled the collection and verification of clinically relevant data, including chemical reactions, changes in proteins, and specific gene expression. Tissue recombination models have been employed for studying prostate development, the initiation and progression of prostate cancer, and the tumor microenvironment. Notably, the epithelial-stromal interaction, which might play a critical role in prostate cancer pathogenesis, can be reproduced in this model. Patient-derived xenograft models have been developed as powerful avatars comprising patient-derived prostate cancer tissues implanted in immunocompromised mice and could serve as a precision medicine approach for each prostate cancer patient. Spheroid and organoid assays, representative of modern three-dimensional cultures, can replicate the conditions in human prostate tumors and the prostate organ itself as a miniature model. Although an intact immune system against the tumor is missing from the models aimed at investigating immuno-oncological reagents in various malignancies, all these experimental models can help researchers in developing new drugs and selecting appropriate treatment strategies for prostate cancer patients.

Cryoablation-activated enhanced nanodoxorubicin release for the therapy of chemoresistant mammary cancer stem-like cells

Anticancer nanodoxorubicin with targeting ability, thermal responsive and pH sensitive characteristic is fabricated. Nanodrug could realize controllable and enhanced drug release when cryoablation is applied at the target tumor site.

Prognostic role of chromogranin A in castration-resistant prostate cancer: A meta-analysis

We aimed to investigate the prognostic value of chromogranin A (CgA) in castration-resistant prostate cancer (CRPC). We conducted a systematic literature search of PubMed, Web of Science, and EMBASE for citations published prior to September 2017 that described CgA and CRPC and performed a standard meta-analysis on survival outcomes. Our meta-analysis included eight eligible studies with 686 patients. The results were as follows: progression-free survival (PFS) was associated with CgA level (hazard ratio [HR] = 2.47, 95% confidence interval [CI]: 1.47-4.14, P = 0.0006); PFS was relative to CgA change (HR = 9.22, 95% CI: 3.03-28.05, P < 0.0001); and overall survival (OS) was relative to CgA level (HR = 1.47, 95% CI: 1.15-1.87, P = 0.002). When we divided the patients into two groups according to therapy status, the result for OS relative to CgA level was an HR of 1.26 (95% CI: 1.09-1.45, P = 0.001) in the first-line hormonal therapy group, and an HR of 2.33 (95% CI: 1.40-3.89, P = 0.001) in the second-line hormonal therapy or chemotherapy group. This meta-analysis indicated that a high CgA level had a negative influence on OS and PFS in CRPC patients. In addition, CRPC patients with a rising CgA had a shorter PFS. Further studies are needed to verify the prognostic value of CgA in CRPC.

Neuroendocrine differentiation in castration resistant prostate cancer. Nuclear medicine radiopharmaceuticals and imaging techniques: A narrative review

BACKGROUND

Androgen Deprivation Therapy (ADT) is the primary treatment for patients suffering from relapsing or advanced prostate cancer (PC). Hormone therapy generally guarantees adequate clinical control of the disease for some years, even in those patients affected by widespread skeletal and soft tissue metastases. Despite ADT, however, most patients treated with hormones eventually progress to castration-resistant prostate cancer (CRPC), for which there are no effective treatments. This clinical reality is an open challenge to the oncologist because of those neoplasms which elaborate neuroendocrine differentiation (NED).

METHODS

An online search of current and past literature on NED in CRPC was performed. Relevant articles dealing with the biological and pathological basis of NED, with nuclear medicine imaging in CRPC and somatostatin treatment in NED were analyzed.

EVIDENCE FROM THE LITERATURE

NED may arise in prostate cancer patients in the late stages of ADT. The onset of NED offers prognostic insight because it reflects a dramatic increase in the aggressive nature of the neoplasm. Several genetic, molecular, cytological and immunohistochemical markers are associated with this transformation. Among these, overexpression of somatostatin receptors, seen through Nuclear Medicine testing, is one of the most studied.

CONCLUSIONS

Preliminary studies show that the overexpression of somatostatin receptors related to NED in CRPC may easily be studied in vivo with PET/CT. This finding offers a potentially useful objective for targeted therapy in CRPC. If the overexpression of SSTRs is shown to afflict a significant segment of patients with CRPC, this will open further study of possible therapeutic options based on this marker.

Prostate Luminal Progenitor Cells in Development and Cancer

Prostate cancer (PCa) has a predominantly luminal phenotype. Basal cells were previously identified as a cell of origin for PCa, but increasing evidence implicates luminal cells as a preferred cell of origin for PCa, as well as key drivers of tumor development and progression. Prostate luminal cells are understudied compared with basal cells. In this review, we describe the contribution of prostate luminal progenitor (LP) cells to luminal cell development and their role in prostate development, androgen-mediated regeneration of castrated prostate, and tumorigenesis. We also discuss the potential value of LP transcriptomics to identify new targets and therapies to treat aggressive PCa. Finally, we propose future research directions focusing on molecular mechanisms underlying LP cell biology and heterogeneity in normal and diseased prostate.

ATP Binding Cassette Sub-family Member 2 (ABCG2) and Xenobiotic Exposure During Early Mouse Embryonic Stem Cell Differentiation

BACKGROUND

ATP binding cassette sub-family member 2 (ABCG2) is a well-defined efflux transporter found in a variety of tissues. The role of ABCG2 during early embryonic development, however, is not established. Previous work which compared data from the ToxCast screening program with that from in-house studies suggested an association exists between exposure to xenobiotics that regulate Abcg2 transcription and differentiation of mouse embryonic stem cells (mESC), a relationship potentially related to redox homeostasis.

METHODS

mESC were grown for up to 9 days. Pharmacological inhibitors were used to assess transporter function with and without xenobiotic exposure. Proliferation and differentiation were evaluated using RedDot1 and quantiative reverse transcriptase-polymerase chain reaction, respectively. ABCG2 activity was assessed using a Pheophorbide a-based fluorescent assay. Protein expression was measured by capillary-based immunoassay.

RESULTS

ABCG2 activity increased in differentiating mESC. Treatment with K0143, an inhibitor of ABCG2, had no effect on proliferation or differentiation. As expected, mitoxantrone and topotecan, two chemotherapeutics, displayed increased toxicity in the presence of K0143. Exposure to K0143 in combination with chemicals predicted by ToxCast to regulate ABCG2 expression did not alter xenobiotic-induced toxicity. Moreover, inhibition of ABCG2 did not shift the toxicity of either tert-Butyl hydroperoxide or paraquat, two oxidative stressors.

CONCLUSION

As previously reported, ABCG2 serves a protective role in mESC. The role of ABCG2 in regulating redox status, however, was unclear. The hypothesis that ABCG2 plays a fundamental role during mESC differentiation or that regulation of the receptor by xenobiotics may be associated with altered mESC differentiation could not be supported. Birth Defects Research, 110:35-47, 2018. Published 2017. This article is a U.S. Government work and is in the public domain in the USA.

Characteristics of primary side population cervical cancer cells

The aim of the present study was to identify and characterize side population (SP) cells in primary cervical cancer. A primary culture was successfully established, and the SP cells were isolated via fluorescence-activated cell sorting. Subsequently, in vitro analysis of clonogenic capacity by soft agar assay and in vivo analysis of tumorigenicity were performed. The isolated SP cells accounted for ~4.73% of the total primary culture cells. The SP cells had a decreased proliferation rate and an increased distribution in G₀/G₁ compared with non-SP (NSP) cells. Following isolation, SP cells exhibited increased proliferative and self-renewal potency compared with NSP cells. Furthermore, significant ATP binding cassette subfamily G member 2 (ABCG2) expression was detected in SP cells but not in NSP cells. The tumor formation rate of SP cells was longer, and the tumor size and tumor formation rate of SP cells were increased in non-obese diabetic/severe combined immunodeficiency mice. In conclusion, the present study demonstrated that SP cells can be isolated from primary cervical cancer cell culture, and SP cells are enriched with stem cell-like cells that have a high capacity for colony formation and tumorigenesis.

The Efflux Transporter ABCG2 Maintains Prostate Stem Cells

Prostate stem cells (PSC) are characterized by their intrinsic resistance to androgen deprivation therapy (ADT), possibly due to the lack of androgen receptor (AR) expression. PSCs resistance to ADT and PSC expansion in castration resistant prostate cancer (CRPC) has sparked great interest in using differentiation therapy as an adjuvant to ADT. Understanding the mechanisms, by which PSCs maintain their undifferentiated phenotype, thus has important implications in differentiation therapy. In the prostate, the ATP binding cassette sub-family G member 2 (ABCG2) transporters, which enrich for AR-positive, ADT-resistant PSCs, play an important role in regulating the intracellular androgen levels by effluxing androgens. We hypothesized that the ABCG2-mediated androgen efflux is responsible for maintaining PSCs in an undifferentiated state. Using the HPr-1-AR (nontumorigenic) and CWR-R1 (tumorigenic) prostate cell lines, it was demonstrated that inhibiting the ABCG2-mediated androgen efflux, with Ko143 (ABCG2 inhibitor), increased the nuclear AR expression due to elevated intracellular androgen levels. Increased nuclear translocation of AR is followed by increased expression of AR regulated genes, a delayed cell growth response, and increased luminal differentiation. Furthermore, Ko143 reduced tumor growth rates in mice implanted with ABCG2-expressing CWR-R1 cells. In addition, Ko143-treated mice had more differentiated tumors as evidenced by an increased percentage of CK8⁺/AR⁺ luminal cells and decreased percentage of ABCG2-expressing cells. Thus, inhibiting ABCG2-mediated androgen efflux forces the PSCs to undergo an AR-modulated differentiation to an ADT-sensitive luminal phenotype.

IMPLICATIONS

This study identifies the mechanism by which the prostate stem cell marker, ABCG2, plays a role in prostate stem cell maintenance and provides a rationale for targeting ABCG2 for differentiation therapy in prostate cancer. Mol Cancer Res; 15(2); 128-40. ©2016 AACR.

Gene Expression in Single Cells Isolated from the CWR-R1 Prostate Cancer Cell Line and Human Prostate Tissue Based on the Side Population Phenotype

Defining biological signals at the single cell level can identify cancer initiating driver mutations. Techniques to isolate single cells such as microfluidics sorting and magnetic capturing systems have limitations such as: high cost, labor intense, and the requirement of a large number of cells. Therefore, the goal of our current study is to identify a cost and labor effective, reliable, and reproducible technique that allows single cell isolation for analysis to promote regular laboratory use, including standard reverse transcription PCR (RT-PCR).

In the current study, we utilized single prostate cells isolated from the CWR-R1 prostate cancer cell line and human prostate clinical specimens, based on the ATP binding cassette (ABC) transporter efflux of dye cycle violet (DCV), side population assay. Expression of four genes: ABCG2; Aldehyde dehydrogenase1A1 (ALDH1A1); androgen receptor (AR); and embryonic stem cell marker, Oct-4, were determined.

Results from the current study in the CWR-R1 cell line showed ABCG2 and ALDH1A1 gene expression in 67% of single side population cells and in 17% or 100% of non-side population cells respectively. Studies using single cells isolated from clinical specimens showed that the Oct-4 gene is detected in only 22% of single side population cells and in 78% of single non-side population cells. Whereas, AR gene expression is in 100% single side population and non-side population cells isolated from the same human prostate clinical specimen.

These studies show that performing RT-PCR on single cells isolated by FACS can be successfully conducted to determine gene expression in single cells from cell lines and enzymatically digested tissue. While these studies provide a simple yes/no expression readout, the more sensitive quantitative RT-PCR would be able to provide even more information if necessary.

Combined cancer therapy with hyaluronan-decorated fullerene-silica multifunctional nanoparticles to target cancer stem-like cells

Cancer stem-like cells (CSCs) are resistant to chemotherapy and highly tumorigenic, which contributes to tumor occurrence and post-treatment relapse. We developed a novel C60 fullerene-silica nanoparticle system surface-decorated with hyaluronan (HA) to target the variant CD44 overexpressed on breast CSCs. Furthermore, doxorubicin hydrochloride (DOX) and indocyanine green (ICG) can be encapsulated in the nanoparticles with ultrahigh encapsulation efficiency (>90%) and loading content (e.g., 48.5% at a drug-to-nanoparticle feeding ratio of 1:1, compared to the commonly used drug-to-nanoparticle feeding ratio of 1:20 with a drug loading content of less than 5%). As a result, the DOX and ICG-laden nanoparticles can be used as a single nanoplatform to achieve combined chemo, photodynamic, and photothermal therapy under near infrared laser irradiation for effective destruction of the breast CSCs both in vitro and in vivo, with no evident systemic toxicity. Moreover, we found the nanoparticles with a higher drug loading content (e.g., 48.5 versus 4.6%) also have significantly higher antitumor efficacy, given the same total drug dose. These results demonstrate the great potential of the multifunctional hybrid nanoparticle system for augmenting cancer therapy by eliminating the CSCs.

Advances in prostate cancer research models: From transgenic mice to tumor xenografting models

The identification of the origin and molecular characteristics of prostate cancer (PCa) has crucial implications for personalized treatment. The development of effective treatments for PCa has been limited; however, the recent establishment of several transgenic mouse lines and/or xenografting models is better reflecting the disease in vivo. With appropriate models, valuable tools for elucidating the functions of specific genes have gone deep into prostate development and carcinogenesis. In the present review, we summarize a number of important PCa research models established in our laboratories (PSA-Cre-ER^T2/PTEN transgenic mouse models, AP-OX model, tissue recombination-xenografting models and PDX models), which represent advances of translational models from transgenic mouse lines to human tumor xenografting. Better understanding of the developments of these models will offer new insights into tumor progression and may help explain the functional significance of genetic variations in PCa. Additionally, this understanding could lead to new modes for curing PCa based on their particular biological phenotypes.

Impact of devascularization and tissue procurement on cell number and RNA integrity in prostatectomy tissue

BACKGROUND

Minimizing the time between tissue devascularization in robot-assisted laparoscopic radical prostatectomy (RALP) and tissue procurement should produce the highest quality tissue for research study. This study examines the relationship between intra-operative time and two indicators of tissue integrity: number of epithelial cells per gram of tissue and RNA integrity numbers (RINs). The study also compares the RIN values of tissue obtained intra-operatively by biopsy, before and after devascularization, to those from RALP specimen tissue, obtained through the routine research tissue procurement process.

METHODS

Prostate tissues from two series of patients were analyzed. In the first, tissue from 18 patients undergoing RALP was analyzed for number of epithelial cells per gram of tissue. In the second, RIN values of tissue from 46 patients involved in a clinical study were analyzed. RIN values were assessed from RALP specimen tissue as well as tissue removed intra-operatively by biopsy, before and after devascularization.

RESULTS

Time from RALP to tissue procurement was not significantly associated with number of epithelial cells per gram of tissue or with RIN values. RINs of biopsy tissue obtained intra-operatively before and after devascularization were similar. However, the RIN values of tissue from RALP specimens were significantly higher than those of biopsy tissue obtained either before or after devascularization.

CONCLUSIONS

Tissue quality, defined by number of epithelial cells or RIN values, was not affected by time between devascularization and procurement. Obtaining tissue from intra-operative biopsies, either before or after devascularization, is not necessary and actually produced lower RINs than found in tissue from RALP specimens, obtained through the routine research tissue procurement process.

PIM1 kinase as a promise of targeted therapy in prostate cancer stem cells

Since the last decade, the PIM family serine/threonine kinases have become a focus in cancer research. Numerous clinical data supports that overexpression of PIM1 is associated with tumor formation in various tissues. However, little is known regarding the function of PIM1 in cancer stem cells. In cancer cells, PIM1 has essential roles in the regulation of the cell cycle, cell proliferation, cell survival and multiple drug resistance. In stem cells, PIM1 kinase exhibits a significant function in stem cell proliferation, self-renewal and expansion. Thus, PIM1 shows a great promise in cancer therapy by targeting stem cells. Furthermore, it is imperative to investigate Pim-1 targeting in cancer stem cells by applicable inhibitors for improving future outcomes. The present review investigated the potential of PIM1 as a therapy target in prostate cancer stem cells.

Metformin and prostate cancer stem cells: a novel therapeutic target

Prostate cancer is the second most frequently diagnosed cancer in the world. Localized disease can be effectively treated with radiation therapy or radical prostatectomy. However, advanced prostate cancer is more difficult to treat and if metastatic, is incurable. There is a need for more effective therapy for advanced prostate cancer. One potential target is the cancer stem cell (CSC). CSCs have been described in several solid tumors, including prostate cancer, and contribute to therapeutic resistance and tumor recurrence. Metformin, a common oral biguanide used to treat type 2 diabetes, has been demonstrated to have anti-neoplastic effects. Specifically, metformin targets CSCs in breast cancer, pancreatic cancer, glioblastoma and colon cancer. Metformin acts directly on the mitochondria to inhibit oxidative phosphorylation and reduce mitochondrial ATP production. This forces tumor cells to compensate by increasing the rate of glycolysis. CSCs rely heavily on mitochondrial oxidative phosphorylation for energy production. The glycolytic switch results in an energy crisis in these cells. Metformin could be used to exploit this metabolic weakness in CSCs. This would increase CSC sensitivity to conventional cancer therapies, circumventing treatment resistance and enhancing treatment efficacy. This review will explore the characteristics of prostate CSCs, their role in tumor propagation and therapeutic resistance and the role of metformin as a potential prostate CSC sensitizer to current anticancer therapies.

Multi-Drug Resistance ABC Transporter Inhibition Enhances Murine Ventral Prostate Stem/Progenitor Cell Differentiation

Multi-drug resistance (MDR)-ATP binding cassette (ABC) transporters, ABCB1, ABCC1, and ABCG2 participate in the efflux of steroid hormones, estrogens, and androgens, which regulate prostate development and differentiation. The role of MDR-ABC efflux transporters in prostate epithelial proliferation and differentiation remains unclear. We hypothesized that MDR-ABC transporters regulate prostate differentiation and epithelium regeneration. Prostate epithelial differentiation was studied using histology, sphere formation assay, and prostate regeneration induced by cycles of repeated androgen withdrawal and replacement. Embryonic deletion of Abcg2 resulted in a decreased number of luminal cells in the prostate and increased sphere formation efficiency, indicating an imbalance in the prostate epithelial differentiation pattern. Decreased luminal cell number in the Abcg2 null prostate implies reduced differentiation. Enhanced sphere formation efficiency in Abcg2 null prostate cells implies activation of the stem/progenitor cells. Prostate regeneration was associated with profound activation of the stem/progenitor cells, indicating the role of Abcg2 in maintaining stem/progenitor cell pool. Since embryonic deletion of Abcg2 may result in compensation by other ABC transporters, pharmacological inhibition of MDR-ABC efflux was performed. Pharmacological inhibition of MDR-ABC efflux enhanced prostate epithelial differentiation in sphere culture and during prostate regeneration. In conclusion, Abcg2 deletion leads to activation of the stem/progenitor cells and enhances differentiating divisions; and pharmacological inhibition of MDR-ABC efflux leads to epithelial differentiation. Our study demonstrates for the first time that MDR-ABC efflux transporter inhibition results in enhanced prostate epithelial cell differentiation.

Enrichment of Human Stem-Like Prostate Cells with s-SHIP Promoter Activity Uncovers a Role in Stemness for the Long Noncoding RNA H19

Understanding normal and cancer stem cells should provide insights into the origin of prostate cancer and their mechanisms of resistance to current treatment strategies. In this study, we isolated and characterized stem-like cells present in the immortalized human prostate cell line, RWPE-1. We used a reporter system with green fluorescent protein (GFP) driven by the promoter of s-SHIP (for stem-SH2-domain-containing 5'-inositol phosphatase) whose stem cell-specific expression has been previously shown. We observed that s-SHIP-GFP-expressing RWPE-1 cells showed stem cell characteristics such as increased expression of stem cell surface markers (CD44, CD166, TROP2) and pluripotency transcription factors (Oct4, Sox2), and enhanced sphere-forming capacity and resistance to arsenite-induced cell death. Concomitant increased expression of the long noncoding RNA H19 was observed, which prompted us to investigate a putative role in stemness for this oncofetal gene. Targeted suppression of H19 with siRNA decreased Oct4 and Sox2 gene expression and colony-forming potential in RWPE-1 cells. Conversely, overexpression of H19 significantly increased gene expression of these two transcription factors and the sphere-forming capacity of RWPE-1 cells. Analysis of H19 expression in various prostate and mammary human cell lines revealed similarities with Sox2 expression, suggesting that a functional relationship may exist between H19 and Sox2. Collectively, we provide the first evidence that s-SHIP-GFP promoter reporter offers a unique marker for the enrichment of human stem-like cell populations and highlight a role in stemness for the long noncoding RNA H19.

Chromogranin A is a potential prognostic marker in prostate cancer patients treated with enzalutamide

BACKGROUND

In this retrospective study, we assessed chromogranin A (CgA) baseline value as a possible factor associated with poor prognosis in metastatic castration-resistant prostate cancer (CRPC).

METHODS

Thirty-five patients with metastatic CRPC progressing after docetaxel chemotherapy treated with enzalutamide are subdivided into three groups: serum CgA level was normal when <120 ng/ml (group A, n = 10), within three times the upper normal value (UNV) when between 120 and 360 (group B, n = 17), more than three times the UNV when ≥360 ng/ml (group C, n = 8).

RESULTS

No correlation was observed in three groups among CgA baseline values and PSA response rates (RR) (P = 0.4648), whereas a significative difference was associated with median progression-free survival (PFS) and overall survival (OS) among three CgA groups (P = 0.0301 and P = 0.0011, respectively). In the multivariate analysis, PSA RR (nonresponsive vs. responsive) and CgA levels (group 3 vs. groups 1 + 2) were predictors of OS (P = 0.0029 and P = 0.0025, respectively), whereas they only were not significantly correlated with PFS, even had a borderline significance (P = 0.0628 and P = 0.0772, respectively).

CONCLUSIONS

In CRPC patients treated with enzalutamide, the evaluation of serum CgA levels could be an useful prognostic factor because of the strong association between CgA value more than three times the UNV and clinical outcome, independently from PSA response.

Berberis libanotica Ehrenb extract shows anti-neoplastic effects on prostate cancer stem/progenitor cells

Cancer stem cells (CSCs), including those of advanced prostate cancer, are a suggested reason for tumor resistance toward conventional tumor therapy. Therefore, new therapeutic agents are urgently needed for targeting CSCs. Despite the minimal understanding of their modes of action, natural products and herbal therapies have been commonly used in the prevention and treatment of many cancers. Berberis libanotica Ehrenb (BLE) is a plant rich in alkaloids which may possess anti-cancer activity and a high potential for eliminating CSCs. We tested the effect of BLE on prostate cancer cells and our data indicated that this extract induced significant reduction in cell viability and inhibited the proliferation of human prostate cancer cell lines (DU145, PC3 and 22Rv1) in a dose- and time-dependent manner. BLE extract induced a perturbation of the cell cycle, leading to a G0-G1 arrest. Furthermore, we noted 50% cell death, characterized by the production of high levels of reactive oxidative species (ROS). Inhibition of cellular migration and invasion was also achieved upon treatment with BLE extract, suggesting a role in inhibiting metastasis. Interestingly, BLE extract had a major effect on CSCs. Cells were grown in a 3D sphere-formation assay to enrich for a population of cancer stem/progenitor cells. Our results showed a significant reduction in sphere formation ability. Three rounds of treatment with BLE extract were sufficient to eradicate the self-renewal ability of highly resistant CSCs. In conclusion, our results suggest a high therapeutic potential of BLE extract in targeting prostate cancer and its CSCs.

Prostate epithelial stem and progenitor cells

The classic androgen ablation and replacement experiment demonstrates that prostate epithelia possess extensive regenerative capacities and implies the existence of the prostate stem/progenitor cells. These cells may serve as the cells of origin for prostate cancer and their intrinsic property may dictate the clinical behaviors of the resulting diseases. Therefore, detailed characterization of these cells will potentially benefit disease prevention, diagnosis and prognosis. In this review, we describe several major in vitro and in vivo approaches that have been employed in the studies of the prostate stem cell activities, summarize the major progress that has been made during the last two decades regarding the identity of prostate stem/progenitor cells and their niches, and discuss some remaining outstanding questions in the field.

Enhanced enrichment of prostate cancer stem-like cells with miniaturized 3D culture in liquid core-hydrogel shell microcapsules

Cancer stem-like cells (CSCs) are rare subpopulations of cancer cells that are reported to be responsible for cancer resistance and metastasis associated with conventional cancer therapies. Therefore, effective enrichment/culture of CSCs is of importance to both the understanding and treatment of cancer. However, it usually takes approximately 10 days for the widely used conventional approach to enrich CSCs through the formation of CSC-containing aggregates. Here we report the time can be shortened to 2 days while obtaining prostate CSC-containing aggregates with better quality based on the expression of surface receptor markers, dye exclusion, gene and protein expression, and in vivo tumorigenicity. This is achieved by encapsulating and culturing human prostate cancer cells in the miniaturized 3D liquid core of microcapsules with an alginate hydrogel shell. The miniaturized 3D culture in core-shell microcapsules is an effective strategy for enriching/culturing CSCs in vitro to facilitate cancer research and therapy development.

Searching for prostate cancer stem cells: markers and methods

The cancer stem cell hypothesis postulates that a single stem-like cancer cell is able to produce all cancer cell types found in a tumor. These cells are also thought to be the causative agents of relapse following therapy. In order to confirm the importance of cancer stem cells in tumor formation and patient prognosis, their role in prostate cancer must be comprehensively studied. This review describes current methods and markers for isolating and characterizing prostate cancer stem cells, including assays for self-renewal, multipotency and resistance to therapy. In particular the advantages and limitations of these approaches are analyzed. The review will also examine novel methods for studying the lineage of cancer stem cells in vivo using transgenic mouse models. These lineage tracing approaches have significant advantages and, if a number of challenges can be addressed, offer great potential for understanding the significance of cancer stem cells in human prostate cancer.

Aldehyde dehydrogenase and ATP binding cassette transporter G2 (ABCG2) functional assays isolate different populations of prostate stem cells where ABCG2 function selects for cells with increased stem cell activity

INTRODUCTION

High expression of aldehyde dehydrogenase1A1 (ALDH1A1) is observed in many organs and tumors and may identify benign and cancer stem cell populations.

METHODS

In the current study, the stem cell characteristics were determined in cells isolated from human prostate cell lines and clinical prostate specimens based upon the ALDEFLUOR™ assay. Cells isolated based on the ALDEFLUOR™ assay were compared to cells isolated based on ATP binding cassette transporter G2 (ABCG2) activity using the side population assay. To test for stem cell characteristics of self-renewal and multipotency, cells with high and low ALDH1A1 activity, based on the ALDEFLUOR™ assay (ALDHHi and ALDH Low), were isolated from prostate clinical specimens and were recombined with rat urogenital sinus mesenchyme to induce prostate gland formation.

RESULTS

The percentage of ALDH Hi cells in prostate cell lines (RWPE-1, RWPE-2, CWR-R1, and DU-145) was 0.5 to 6%, similarly in non-tumor and tumor clinical specimens the percentage of ALDH Hi cells was 0.6 to 4%. Recombinants using ALDH Hi cells serially generated prostate tissue up to three generations with as few as 250 starting cells. Immunohistochemical analysis of the recombinants using ALDHHi cells contained prostatic glands frequently expressing androgen receptor (AR), p63, chromogranin A, ALDH1A1, ABCG2, and prostate specific antigen (PSA), compared to their ALDH Low counterparts. Inhibition of ALDH resulted in the reduction of sphere formation capabilities in the CWR-R1, but not in the RWPE-2 and DU-145, prostate cell lines. ABCG2 inhibition resulted in a more robust decrease of sphere formation in androgen sensitive cell lines, CWR-R1 and RWPE-2, but not androgen insensitive DU-145. ALDH1A1 expression was enriched in ALDH Hi cells and non-side population cells. ABCG2 expression was only enriched in side population cells.

CONCLUSIONS

The percentage of ALDHHi cells in prostate cell lines and prostate tissue was consistently higher compared to cells with high ABCG2 activity, identified with the side population assay. The expression of the stem and differentiation markers indicates the ALDH Hi recombinants contained cells with self-renewal and multipotency activity. When the two assays were directly compared, cells with the side population phenotype demonstrated more stem cell potential in the tissue recombination assay compared to ALDH Hi cells. The increased stem cell potential of side population cells in the tissue recombination assay and the decrease in sphere formation when ABCG2 is inhibited indicates that the side population enriches for prostate stem cells.