Expression and prognostic significance of cancer stem cell markers CD24 and CD44 in urothelial bladder cancer xenografts and patients undergoing radical cystectomy

OBJECTIVES

To evaluate CD24/CD44/CD47 cancer stem cell marker expressions in bladder cancer (BCa) and provide data on their prognostic significance for clinical outcome in patients undergoing radical cystectomy (RC).

MATERIAL AND METHODS

Primary BCa tissue was used for xenograft studies. A tissue microarray was prepared using specimens from a cohort of 132 patients. All patients underwent RC for urothelial BCa between 2001 and 2010. Expression of CD24, CD44, and CD47 was examined in primary samples and xenografts by fluorescence-activated cell sorting. Populations of CD24(low)- and CD24(high)-expressing cells were sorted and evaluated for tumorigenicity in vivo. Tissue microarray was analyzed for CD24/CD44 staining intensity and tumor-specific vs. stromal cell staining. Associations with BCa survival, BCa stage, and lymph node status were evaluated by univariate and multivariate analyses.

RESULTS

CD24 and CD44/CD47 expressions mark distinct cell populations within the normal urothelium as well as in BCa. CD24(high/low) expression was not sufficient to characterize CD24 as a BCa-initiating marker in in vivo primary xenotransplants. CD24 and CD44 expressions correlated with lower cancer-specific survival in patients. However, multivariate analyses of CD24 or CD44 did not demonstrate significantly increased hazards for cancer-specific death if analyzed together with stage, grade, and nodal status of patients.

CONCLUSIONS

Cancer stem cell markers CD24/CD44/CD47 are differentially expressed in cells of urothelial BCa in patients undergoing RC and influence cancer-specific survival of patients. Further evaluation of CD24/CD44/CD47 protein expression could be of high therapeutic value in BCa. However, both CD24 and CD44 expressions cannot be regarded as independent prognostic parameters for patients undergoing RC.

Functional conservation of Nematostella Wnts in canonical and noncanonical Wnt-signaling

Cnidarians surprise by the completeness of Wnt gene subfamilies (11) expressed in an overlapping pattern along the anterior-posterior axis. While the functional conservation of canonical Wnt-signaling components in cnidarian gastrulation and organizer formation is evident, a role of Nematostella Wnts in noncanonical Wnt-signaling has not been shown so far. In Xenopus, noncanonical Wnt-5a/Ror2 and Wnt-11 (PCP) signaling are distinguishable by different morphant phenotypes. They differ in PAPC regulation, cell polarization, cell protrusion formation, and the so far not reported reorientation of the microtubules. Based on these readouts, we investigated the evolutionary conservation of Wnt-11 and Wnt-5a function in rescue experiments with Nematostella orthologs and Xenopus morphants. Our results revealed that NvWnt-5 and -11 exhibited distinct noncanonical Wnt activities by disturbing convergent extension movements. However, NvWnt-5 rescued XWnt-11 and NvWnt-11 specifically XWnt-5a depleted embryos. This unexpected 'inverse' activity suggests that specific structures in Wnt ligands are important for receptor complex recognition in Wnt-signaling. Although we can only speculate on the identity of the underlying recognition motifs, it is likely that these crucial structural features have already been established in the common ancestor of cnidarians and vertebrates and were conserved throughout metazoan evolution.

Development and characteristics of preclinical experimental models for the research of rare neuroendocrine bladder cancer

PURPOSE

For rare cancers such as neuroendocrine bladder cancer treatment options are limited due partly to the lack of preclinical models. Techniques to amplify rare primary neuroendocrine bladder cancer cells could provide novel tools for the discovery of drug and diagnostic targets. We developed preclinical experimental models for neuroendocrine bladder cancer.

MATERIALS AND METHODS

Fresh tumor tissue from 2 patients with neuroendocrine bladder cancer was used to establish in vitro and in vivo models. We analyzed additional archived tissues in the National Center of Tumor Diseases tissue bank from patients with neuroendocrine bladder cancer. Primary tumor samples were collected during radical cystectomy. PHA-665752 was used to inhibit MET in animal models and cell cultures. The expression of markers and drug targets in neuroendocrine bladder cancer was determined by flow cytometry. The growth of neuroendocrine bladder cancer in vitro was determined by counting live cells. Tumor growth in mice was assessed by measuring tumor volume. Groups were compared using the nonparametric Kruskal-Wallis test.

RESULTS

Xenograft models and serum-free cultures of neuroendocrine bladder cancer cells allowed screening for cell surface markers and drug targets. We found expression of the HGF receptor MET in neuroendocrine bladder cancer cultures, xenograft models and primary patient sections. The growth of neuroendocrine bladder cancer spheroids in vitro depended critically on HGF. Treatment of neuroendocrine bladder cancer bearing mice with a MET inhibitor significantly decreased tumor growth compared to that in control treated mice.

CONCLUSIONS

Neuroendocrine bladder cancer xenografts and serum-free cultures provided suitable models in which to identify diagnostic markers and therapeutic targets. Using the models, we noted HGF dependent growth of human neuroendocrine bladder cancer and identified MET as a new treatment target for neuroendocrine bladder cancer.

Protein profile of basal prostate epithelial progenitor cells--stage-specific embryonal antigen 4 expressing cells have enhanced regenerative potential in vivo

The long‐term propagation of basal prostate progenitor cells ex vivo has been very difficult in the past. The development of novel methods to expand prostate progenitor cells in vitro allows determining their cell surface phenotype in greater detail. Mouse (Lin⁻Sca‐1⁺CD49f⁺ Trop2^high‐phenotype) and human (Lin⁻CD49f⁺TROP2^high) basal prostate progenitor cells were expanded in vitro. Human and mouse cells were screened using 242 anti‐human or 176 antimouse monoclonal antibodies recognizing the cell surface protein profile. Quantitative expression was evaluated at the single‐cell level using flow cytometry. Differentially expressed cell surface proteins were evaluated in conjunction with the known CD49f⁺/TROP2^high phenotype of basal prostate progenitor cells and characterized by in vivo sandwich‐transplantation experiments using nude mice. The phenotype of basal prostate progenitor cells was determined as CD9⁺/CD24⁺/CD29⁺/CD44⁺/CD47⁺/CD49f⁺/CD104⁺/CD147⁺/CD326⁺/Trop2^high of mouse as well as human origin. Our analysis revealed several proteins, such as CD13, Syndecan‐1 and stage‐specific embryonal antigens (SSEAs), as being differentially expressed on murine and human CD49f⁺TROP2⁺ basal prostate progenitor cells. Transplantation experiments suggest that CD49f⁺TROP2^highSSEA‐4^high human prostate basal progenitor cells to be more potent to regenerate prostate tubules in vivo as compared with CD49f⁺TROP2^high or CD49f⁺TROP2^highSSEA‐4^low cells. Determination of the cell surface protein profile of functionally defined murine and human basal prostate progenitor cells reveals differentially expressed proteins that may change the potency and regenerative function of epithelial progenitor cells within the prostate. SSEA‐4 is a candidate cell surface marker that putatively enables a more accurate identification of the basal PESC lineage.

The influence of prostatic anatomy and neurotrophins on basal prostate epithelial progenitor cells

BACKGROUND

Based on findings of surface marker, protein screens as well as the postulated near-urethral location of the prostate stem cell niche, we were interested whether androgen ablation, distinct anatomic regions within the prostate or neurotrophins have an influence on basal prostate epithelial progenitor cells (PESCs).

METHODS

Microdissection of the prostate, enzymatic digestion, and preparation of single cells was performed from murine and human prostates. Adult PESC marker expressions were compared between a group of C57BL/6 mice and a separate group of castrated C57BL/6 mice. Surface markers CD13/CD271 on human prostate epithelial progenitor cells were evaluated by FACS analyses in cells cultured under novel stem cell conditions. The effect of neurotrophins NGF, NT3, and BDNF were evaluated with respect to their influence on proliferation and activation of human basal PESCs in vitro.

RESULTS

We demonstrate the highest percentage of CD49f+ and Trop2+ expressing cells in the urethra near prostatic regions of WT mice (Trop2+ proximal: 10% vs. distal to the urethra: 3%, P < 0.001). While a marked increase of Trop2 expressing cells can be measured both in the proximal and distal prostatic regions after castration, the most prominent increase in Trop2+ cells can be measured in the prostatic tissue distant to the urethra. Furthermore, we demonstrate that the proportion of syndecan-1 expressing cells greatly increases in the regions proximal to the urethra after castration (WT: 5% vs. castrated: 40%). We identified heterogeneous CD13 and nerve growth factor receptor (p75(NGFR), CD271) expression on CD49f(+)/TROP2(high) human basal PESCs. Addition of the neurotrophins NT3, BDNF, and NGF to the stem cell media led to a marked temporary increase in the proliferation of human basal PESCs.

CONCLUSIONS

Our results in mice support the model, in which the proximal urethral region contains the prostate stem cell niche while a stronger androgen-dependent regulation of adult prostate stem cells can be found in the peripheral prostatic tissue. Neutrophin signaling via nerve growth factor receptor is possibly involved in human prostate stem cell homeostasis.

Abstract B50: A patient-derived renal cell carcinoma model as a platform for the identification of novel diagnostic markers and therapeutic targets

Clear-cell renal cell carcinoma (ccRCC) is highly resistant to conventional therapies and to date effective treatment is restricted to surgical resection. Pre-clinical in vitro and in vivo models, which accurately mimic this disease, are critical for the development of novel effective therapies. Previous attempts to culture ccRCC cells have been proven difficult and thus, only few ccRCC cell lines are currently available. In addition long-term culturing often causes loss of primary tumor characteristics including tumor heterogeneity. This might explain why in contrast to other tumor entities, tumor-initiating cell (TIC) subpopulations have so far not been reported for ccRCC. TICs have been associated with tumor progression, metastasis and drug-resistance. Consequently these cells have also been named cancer stem cells (CSCs). Furthermore, distinct combinations of genetic and epigenetic alterations result in profound inter-patient heterogeneity and can in part promote TIC activity. Therefore, the development and characterization of clinically relevant patient derived ccRCC-models would provide an experimental basis to study the complex mechanisms leading to and maintaining ccRCCs.

Hence, we established a patient-derived serum-free spheroid culture system that can be used to propagate primary ccRCC cells. These ccRCC cells retain their tumor-initiating potential and mimic the human malignancy upon orthotopic injection into immunodeficient mice. They not only mirror the histological properties but also the molecular features of the parental tumor. Moreover, these cells show the capacity to form de novo metastasis in lungs, which is the most common metastatic site for ccRCC in patients. The established ccRCC cultures were then used as a screening platform for the identification of surface proteins, which are heterogeneously expressed among tumor cells. Functional in vitro and in vivo assays showed that subpopulations defined by expression of these markers also displayed distinct functional characteristics including TIC activity. Gene Set Enrichment Analysis (GSEA) revealed differences in the signaling networks active in these sub-populations. In addition, molecular and cellular assays addressed the significance of these pathways for the maintenance of ccRCC malignancy. Currently the identified surface markers and underlying pathways are validated as potential novel diagnostic and therapeutic targets.

Therefore, our novel patient-derived serum-free spheroid culture system serves as a platform to expand patient derived ccRCCs. It further allows the analysis and characterization of different subpopulations, which may ultimately contribute to the understanding of the molecular basis underlying progression, therapy-resistance and metastasis of this disease.

Citation Format: Teresa Rigo-Watermeier, Corinna Klein, Vanessa Vogel, Christian Eisen, Thomas Hoefner, Wilko Weichert, Sascha Pahernik, Markus Hohenfellner, Martin R. Sprick, Andreas Trumpp. A patient-derived renal cell carcinoma model as a platform for the identification of novel diagnostic markers and therapeutic targets. [abstract]. In: Proceedings of the Third AACR International Conference on Frontiers in Basic Cancer Research; Sep 18-22, 2013; National Harbor, MD. Philadelphia (PA): AACR; Cancer Res 2013;73(19 Suppl):Abstract nr B50.