Developmental tumourigenesis: NCAM as a putative marker for the malignant renal stem/progenitor cell population

Hallmark discoveries in the biology of Wilms tumour

The modern study of Wilms tumour was prompted nearly 50 years ago, when Alfred Knudson proposed the 'two-hit' model of tumour development. Since then, the efforts of researchers worldwide have substantially expanded our knowledge of Wilms tumour biology, including major advances in genetics - from cloning the first Wilms tumour gene to high-throughput studies that have revealed the genetic landscape of this tumour. These discoveries improve understanding of the embryonal origin of Wilms tumour, familial occurrences and associated syndromic conditions. Many efforts have been made to find and clinically apply prognostic biomarkers to Wilms tumour, for which outcomes are generally favourable, but treatment of some affected individuals remains challenging. Challenges are also posed by the intratumoural heterogeneity of biomarkers. Furthermore, preclinical models of Wilms tumour, from cell lines to organoid cultures, have evolved. Despite these many achievements, much still remains to be discovered: further molecular understanding of relapse in Wilms tumour and of the multiple origins of bilateral Wilms tumour are two examples of areas under active investigation. International collaboration, especially when large tumour series are required to obtain robust data, will help to answer some of the remaining unresolved questions.

Molecular subtyping and characterization of clear cell renal cell carcinoma by tumor differentiation trajectories

Previous bulk RNA sequencing or whole genome sequencing on clear cell renal cell carcinoma (ccRCC) subtyping mainly focused on ccRCC cell origin or the complex tumor microenvironment (TME). Based on the single-cell RNA sequencing (scRNA-seq) data of 11 primary ccRCC specimens, cancer stem-cell-like subsets could be differentiated into five trajectories, whereby we further classified ccRCC cells into three groups with diverse molecular features. These three ccRCC subgroups showed significantly different outcomes and potential targets to tyrosine kinase inhibitors (TKIs) or immune checkpoint inhibitors (ICIs). Tumor cells in three differentiation directions exhibited distinct interactions with other subsets in the ccRCC niches. The subtyping model was examined through immunohistochemistry staining in our ccRCC cohort and validated the same classification effect as the public patients. All these findings help gain a deeper understanding about the pathogenesis of ccRCC and provide useful clues for optimizing therapeutic schemes based on the molecular subtype analysis.

Altered binding affinity of SIX1-Q177R correlates with enhanced WNT5A and WNT pathway effector expression in Wilms tumor

Wilms tumors present as an amalgam of varying proportions of tissues located within the developing kidney, one being the nephrogenic blastema comprising multipotent nephron progenitor cells (NPCs). The recurring missense mutation Q177R in NPC transcription factors SIX1 and SIX2 is most correlated with tumors of blastemal histology and is significantly associated with relapse. Yet, the transcriptional regulatory consequences of SIX1/2-Q177R that might promote tumor progression and recurrence have not been investigated extensively. Utilizing multiple Wilms tumor transcriptomic datasets, we identified upregulation of the gene encoding non-canonical WNT ligand WNT5A in addition to other WNT pathway effectors in SIX1/2-Q177R mutant tumors. SIX1 ChIP-seq datasets from Wilms tumors revealed shared binding sites for SIX1/SIX1-Q177R within a promoter of WNT5A and at putative distal cis-regulatory elements (CREs). We demonstrate colocalization of SIX1 and WNT5A in Wilms tumor tissue and utilize in vitro assays that support SIX1 and SIX1-Q177R activation of expression from the WNT5A CREs, as well as enhanced binding affinity within the WNT5A promoter that may promote the differential expression of WNT5A and other WNT pathway effectors associated with SIX1-Q177R tumors.

Single-Cell Transcriptional Landscape Reveals the Regulatory Network and Its Heterogeneity of Renal Mitochondrial Damages in Diabetic Kidney Disease

Diabetic kidney disease (DKD) is one of the common chronic microvascular complications of diabetes in which mitochondrial disorder plays an important role in its pathogenesis. The current study delved into the single-cell level transcriptome heterogeneity of mitochondrial homeostasis in db/db mice, an animal model for study of type 2 diabetes and DKD, with single-cell RNA sequencing (scRNA-Seq) and bulk RNA-seq analyses. From the comprehensive dataset comprising 13 meticulously captured and authenticated renal cell types, an unsupervised cluster analysis of mitochondria-related genes within the descending loop of Henle, collecting duct principal cell, endothelial, B cells and macrophage, showed that they had two types of cell subsets, i.e., health-dominant and DKD-dominant clusters. Pseudotime analysis, cell communication and transcription factors forecast resulted in identification of the hub differentially expressed genes between these two clusters and unveiled that the hierarchical regulatory network of receptor-TF-target genes was triggered by mitochondrial degeneration. Furthermore, the collecting duct principal cells were found to be regulated by the decline of Fzd7, which contributed to the impaired cellular proliferation and development, apoptosis and inactive cell cycle, as well as diminished capacity for material transport. Thereby, both scRNA-Seq and bulk RNA-Seq data from the current study elucidate the heterogeneity of mitochondrial disorders among distinct cell types, particularly in the collecting duct principal cells and B cells during the DKD progression and drug administration, which provide novel insights for better understanding the pathogenesis of DKD.

Characterization of alternative mRNA splicing in cultured cell populations representing progressive stages of human fetal kidney development

Nephrons are the functional units of the kidney. During kidney development, cells from the cap mesenchyme-a transient kidney-specific progenitor state-undergo a mesenchymal to epithelial transition (MET) and subsequently differentiate into the various epithelial cell types that create the tubular structures of the nephron. Faults in this transition can lead to a pediatric malignancy of the kidney called Wilms' tumor that mimics normal kidney development. While human kidney development has been characterized at the gene expression level, a comprehensive characterization of alternative splicing is lacking. Therefore, in this study, we performed RNA sequencing on cell populations representing early, intermediate, and late developmental stages of the human fetal kidney, as well as three blastemal-predominant Wilms' tumor patient-derived xenografts. Using this newly generated RNAseq data, we identified a set of transcripts that are alternatively spliced between the different developmental stages. Moreover, we found that cells from the earliest developmental stage have a mesenchymal splice-isoform profile that is similar to that of blastemal-predominant Wilms' tumor xenografts. RNA binding motif enrichment analysis suggests that the mRNA binding proteins ESRP1, ESRP2, RBFOX2, and QKI regulate alternative mRNA splicing during human kidney development. These findings illuminate new molecular mechanisms involved in human kidney development and pediatric kidney cancer.

Ubiquitous Neural Cell Adhesion Molecule (NCAM): Potential Mechanism and Valorisation in Cancer Pathophysiology, Drug Targeting and Molecular Transductions

Neural cell adhesion molecule, an integrated molecule of immunoglobulin protein superfamily involved in cell-cell adhesion, undergoes various structural modifications through numerous temporal-spatial regulations that generously alter their expressions on cell surfaces. These varied expression patterns are mostly envisioned in the morphogenesis and innervations of different human organs and systems. The considerable role of NCAM in neurite growth, brain development and etc. and its altered expression of NCAM in proliferating tumour cells and metastasis of various human melanomas clearly substantiate its appropriateness as a cell surface marker for diagnosis and potential target for several therapeutic moieties. This characteristic behaviour of NCAM is confined to its novel biochemistry, structural properties, signalling interactions and polysialylation. In particular, the characteristic expressions of NCAM are mainly attributed by its polysialylation, a post-translational modification that attaches polysialyl groups to the NCAM. The altered expression of NCAM on cell surface develops curiosity amidst pharmaceutical scientists, which drives them to understand its role of such expressions in various human melanomas and to elucidate the promising therapeutic strategies that are currently available to target NCAM appositely. Therefore, this review article is articulated with an insight on the altered expressions of NCAM, the clinical significances and the consequences of such atypical expression patterns in various human organs and systems.

Unlocking the Wnt pathway: Therapeutic potential of selective targeting FZD7 in cancer

The Wnt signaling is of paramount pathophysiological importance. Despite showing promising anticancer activities in pre-clinical studies, current Wnt pathway inhibitors face complications in clinical trials resulting from on-target toxicity. Hence, the targeting of pathway component(s) that are essential for cancer but dispensable for normal physiology is key to the development of a safe Wnt signaling inhibitor. Frizzled₇ (FZD₇) is a Wnt pathway receptor that is redundant in healthy tissues but crucial in various cancers. FZD₇ modulates diverse aspects of carcinogenesis, including cancer growth, metastasis, maintenance of cancer stem cells, and chemoresistance. In this review, we describe state-of-the-art knowledge of the functions of FZD₇ in carcinogenesis and adult tissue homeostasis. Next, we overview the development of small molecules and biomolecules that target FZD₇. Finally, we discuss challenges and possibilities in developing FZD₇-selective antagonists.

Wilms' Tumor Primary Cells Display Potent Immunoregulatory Properties on NK Cells and Macrophages

Simple Summary

Wilms’ tumor (WT) is the most common childhood renal tumor accounting for approximately 7% of childhood malignancies. The overall survival rate for patients with favorable histology is greater than 90% while the survival rate for patients with poor prognostic factors is around 50%. The current treatments consist in a combination of surgery and chemotherapy or radiotherapy in high risk patients. Such treatments are responsible for significant adverse effects requiring long-term monitoring. Thus, a main challenge in WT treatment is the development of novel therapeutic strategies to eliminate or minimize the adverse effects. The characterization of an immune environment could allow the identification of new therapeutic targets. Herein we studied the interaction between WT and innate immune cells, in particular NK cells and monocytes. Although WT are highly susceptible to NK-mediated lysis, the detection of immunoregulatory activity of WT tumor cells on NK cells and also on monocytes could offer novel cellular and molecular targets for an efficacious immunotherapy of WT.

Abstract

The immune response plays a crucial defensive role in cancer growth and metastasis and is a promising target in different tumors. The role of the immune system in Wilm’s Tumor (WT), a common pediatric renal malignancy, is still to be explored. The characterization of the immune environment in WT could allow the identification of new therapeutic strategies for targeting possible inhibitory mechanisms and/or lowering toxicity of the current treatments. In this study, we stabilized four WT primary cultures expressing either a blastematous (CD56⁺/CD133⁻) or an epithelial (CD56⁻/CD133⁺) phenotype and investigated their interactions with innate immune cells, namely NK cells and monocytes. We show that cytokine-activated NK cells efficiently kill WT cells. However, after co-culture with WT primary cells, NK cells displayed an impaired cytotoxic activity, decreased production of IFNγ and expression of CD107a, DNAM-1 and NKp30. Analysis of the effects of the interaction between WT cells and monocytes revealed their polarization towards alternatively activated macrophages (M2) that, in turn, further impaired NK cell functions. In conclusion, we show that both WT blastematous and epithelial components may contribute directly and indirectly to a tumor immunosuppressive microenvironment that is likely to play a role in tumor progression.

Human kidney clonal proliferation disclose lineage-restricted precursor characteristics

In-vivo single cell clonal analysis in the adult mouse kidney has previously shown lineage-restricted clonal proliferation within varying nephron segments as a mechanism responsible for cell replacement and local regeneration. To analyze ex-vivo clonal growth, we now preformed limiting dilution to generate genuine clonal cultures from one single human renal epithelial cell, which can give rise to up to 3.4 * 10⁶ cells, and analyzed their characteristics using transcriptomics. A comparison between clonal cultures revealed restriction to either proximal or distal kidney sub-lineages with distinct cellular and molecular characteristics; rapidly amplifying de-differentiated clones and a stably proliferating cuboidal epithelial-appearing clones, respectively. Furthermore, each showed distinct molecular features including cell-cycle, epithelial-mesenchymal transition, oxidative phosphorylation, BMP signaling pathway and cell surface markers. In addition, analysis of clonal versus bulk cultures show early clones to be more quiescent, with elevated expression of renal developmental genes and overall reduction in renal identity markers, but with an overlapping expression of nephron segment identifiers and multiple identity. Thus, ex-vivo clonal growth mimics the in-vivo situation displaying lineage-restricted precursor characteristics of mature renal cells. These data suggest that for reconstruction of varying renal lineages with human adult kidney based organoid technology and kidney regeneration ex-vivo, use of multiple heterogeneous precursors is warranted.

Isolation and characterisation of nasoseptal cartilage stem/progenitor cells and their role in the chondrogenic niche

BACKGROUND

Since cartilage-derived stem/progenitor cells (CSPCs) were first identified in articular cartilage using differential adhesion to fibronectin, their self-renewal capacity and niche-specific lineage preference for chondrogenesis have propelled their application for cartilage tissue engineering. In many adult tissues, stem/progenitor cells are recognised to be involved in tissue homeostasis. However, the role of nasoseptal CSPCs has not yet been elucidated. Our aim was to isolate and characterise nasoseptal CSPCs alongside nasoseptal chondrocyte populations and determine chondrogenic capacity.

METHODS

Here, we isolated nasoseptal CSPCs using differential adhesion to fibronectin and assessed their colony forming efficiency, proliferation kinetics, karyotype and trilineage potential. CSPCs were characterised alongside non-fibronectin-adherent nasoseptal chondrocytes (DNCs) and cartilage-derived cells (CDCs, a heterogenous combination of DNCs and CSPCs) by assessing differences in gene expression profiles using PCR Stem Cell Array, immunophenotype using flow cytometry and chondrogencity using RT-PCR and histology.

RESULTS

CSPCs were clonogenic with increased gene expression of the neuroectodermal markers NCAM1 and N-Cadherin, as well as Cyclins D1 and D2, compared to DNCs. All three cell populations expressed recognised mesenchymal stem cell surface markers (CD29, CD44, CD73, CD90), yet only CSPCs and CDCs showed multilineage differentiation potential. CDC populations expressed significantly higher levels of type 2 collagen and bone morphogenetic protein 2 genes, with greater cartilage extracellular matrix secretion. When DNCs were cultured in isolation, there was reduced chondrogenicity and higher expression of type 1 collagen, stromal cell-derived factor 1 (SDF-1), CD73 and CD90, recognised markers of a fibroblast-like phenotype.

CONCLUSIONS

Fibronectin-adherent CSPCs demonstrate a unique gene expression profile compared to non-fibronectin-adherent DNCs. DNCs cultured in isolation, without CSPCs, express fibroblastic phenotype with reduced chondrogenicity. Mixed populations of stem/progenitor cells and chondrocytes were required for optimal chondrogenesis, suggesting that CSPCs may be required to retain phenotypic stability and chondrogenic potential of DNCs. Crosstalk between DNCs and CSPCs is proposed based on SDF-1 signalling.

A cluster robustness score for identifying cell subpopulations in single cell gene expression datasets from heterogeneous tissues and tumors

MOTIVATION

A major aim of single cell biology is to identify important cell types such as stem cells in heterogeneous tissues and tumors. This is typically done by isolating hundreds of individual cells and measuring expression levels of multiple genes simultaneously from each cell. Then, clustering algorithms are used to group together similar single-cell expression profiles into clusters, each representing a distinct cell type. However, many of these clusters result from overfitting, meaning that rather than representing biologically meaningful cell types, they describe the intrinsic 'noise' in gene expression levels due to limitations in experimental precision or the intrinsic randomness of biochemical cellular processes. Consequentially, these non-meaningful clusters are most sensitive to noise: a slight shift in gene expression levels due to a repeated measurement will rearrange the grouping of data points such that these clusters break up.

RESULTS

To identify the biologically meaningful clusters we propose a 'cluster robustness score': We add increasing amounts of noise (zero mean and increasing variance) and check which clusters are most robust in the sense that they do not mix with their neighbors up to high levels of noise. We show that biologically meaningful cell clusters that were manually identified in previously published single cell expression datasets have high robustness scores. These scores are higher than what would be expected in corresponding randomized homogeneous datasets having the same expression level statistics. We believe that this scoring system provides a more automated way to identify cell types in heterogeneous tissues and tumors.

SUPPLEMENTARY INFORMATION

Supplementary data are available at Bioinformatics online.

Forty-five patient-derived xenografts capture the clinical and biological heterogeneity of Wilms tumor

The lack of model systems has limited the preclinical discovery and testing of therapies for Wilms tumor (WT) patients who have poor outcomes. Herein, we establish 45 heterotopic WT patient-derived xenografts (WTPDX) in CB17 scid^-/- mice that capture the biological heterogeneity of Wilms tumor (WT). Among these 45 total WTPDX, 6 from patients with diffuse anaplastic tumors, 9 from patients who experienced disease relapse, and 13 from patients with bilateral disease are included. Early passage WTPDX show evidence of clonal selection, clonal evolution and enrichment of blastemal gene expression. Favorable histology WTPDX are sensitive, whereas unfavorable histology WTPDX are resistant to conventional chemotherapy with vincristine, actinomycin-D, and doxorubicin given singly or in combination. This WTPDX library is a unique scientific resource that retains the spectrum of biological heterogeneity present in WT and provides an essential tool to test targeted therapies for WT patient groups with poor outcomes.

The progress in pre-clinical drug discovery for Wilms tumor (WT) is limited by a lack of disease models. Here, the authors develop 45 heterotopic WT patient-derived xenografts including several anaplastic models that recapitulate the biological heterogeneity of WT, and propose this as a resource for evaluating future therapeutics for WT.

NCAM1/FGF module serves as a putative pleuropulmonary blastoma therapeutic target

Pleuropulmonary blastoma (PPB) is a rare pediatric lung neoplasm that recapitulates developmental pathways of early embryonic lungs. As lung development proceeds with highly regulated mesenchymal-epithelial interactions, a DICER1 mutation in PPB generates a faulty lung differentiation program with resultant biphasic tumors composed of a primitive epithelial and mesenchymal stroma with early progenitor blastomatous cells. Deciphering of PPB progression has been hampered by the difficulty of culturing PPB cells, and specifically progenitor blastomatous cells. Here, we show that in contrast with in-vitro culture, establishment of PPB patient-derived xenograft (PDX) in NOD-SCID mice selects for highly proliferating progenitor blastoma overexpressing critical regulators of lung development and multiple imprinted genes. These stem-like tumors were sequentially interrogated by gene profiling to show a FGF module that is activated alongside Neural cell adhesion molecule 1 (NCAM1). Targeting the progenitor blastoma and these transitions with an anti-NCAM1 immunoconjugate (Lorvotuzumab mertansine) inhibited tumor growth and progression providing new paradigms for PPB therapeutics. Altogether, our novel in-vivo PPB xenograft model allowed us to enrich for highly proliferating stem-like cells and to identify FGFR and NCAM1 as two key players that can serve as therapeutic targets in this poorly understood and aggressive disease.

Blastemal NCAM+ALDH1+ Wilms' tumor cancer stem cells correlate with disease progression and poor clinical outcome: A pilot study

BACKGROUND

Cancer Stem Cells (CSCs) have been suggested as the culprit responsible for tumor resistance to treatment and disease recurrence. Wilms' tumor (WT) is a paradigm for studying the relation between development and tumorigenesis, showing three main histological elements: undifferentiated blastema, epithelia and stroma, mimicking human kidney development. NCAM + ALDH1+ cells were previously found to contain the cancer stem like-cell population in WT. Thus far, the correlation between histologic characterization of this cell population, clinicopathologic parameters and prognostic outcome has yet been investigated in WT.

PROCEDURES

Paraffin-imbedded primary WT specimens from twenty-four patients were immunostained for NCAM and ALDH1. Positivity and histologic compartment localization were determined by two independent observers, blinded to the clinical outcome. Clinicopathologic parameters and prognostic outcomes were determined based on the patients' medical records. The association of NCAM and ALDH1 co-localization with clinicopathologic characteristics was analyzed byχ²-test. Survival analysis was carried out by the log-rank test using Kaplan-Meier method.

RESULTS

Blastemal co-localization of NCAM and ALDH1 was observed in 33% of WTs. Metastases, ICE chemotherapy protocol, blastemal predominance following preoperative chemotherapy, recurrence and patient demise were found to significantly correlate with blastemal NCAM + ALDH1+ cell staining (p < 0.05). A significant inverse correlation between blastemal double positive cells, disease-free survival and overall survival was also observed.

CONCLUSIONS

WT blastemal NCAM + ALDH1+ CSCs significantly correlate with adverse clinicopathologic parameters and poorer prognosis. These results underscore the role of CSCs in disease progression. Additionally, this pilot study supports the addition of these markers for risk stratification of WTs.

Molecular and epidemiologic characterization of Wilms tumor from Baghdad, Iraq

BACKGROUND

Wilms tumor (WT) is the most common childhood kidney cancer worldwide, yet its incidence and clinical behavior vary according to race and access to adequate healthcare resources. To guide and streamline therapy in the war-torn and resource-constrained city of Baghdad, Iraq, we conducted a first-ever molecular analysis of 20 WT specimens to characterize the biological features of this lethal disease within this challenged population.

METHODS

Next-generation sequencing of ten target genes associated with WT development and treatment resistance (WT1, CTNNB1, WTX, IGF2, CITED1, SIX2, p53, N-MYC, CRABP2, and TOP2A) was completed. Immunohistochemistry was performed for 6 marker proteins of WT (WT1, CTNNB1, NCAM, CITED1, SIX2, and p53). Patient outcomes were compiled.

RESULTS

Mutations were detected in previously described WT "hot spots" (e.g., WT1 and CTNNB1) as well as novel loci that may be unique to the Iraqi population. Immunohistochemistry showed expression domains most typical of blastemal-predominant WT. Remarkably, despite the challenges facing families and care providers, only one child, with combined WT1 and CTNNB1 mutations, was confirmed dead from disease. Median clinical follow-up was 40.5 months (range 6-78 months).

CONCLUSIONS

These data suggest that WT biology within a population of Iraqi children manifests features both similar to and unique from disease variants in other regions of the world. These observations will help to risk stratify WT patients living in this difficult environment to more or less intensive therapies and to focus treatment on cell-specific targets.

In Vivo Expansion of Cancer Stemness Affords Novel Cancer Stem Cell Targets: Malignant Rhabdoid Tumor as an Example

Cancer stem cell (CSC) identification relies on transplantation assays of cell subpopulations sorted from fresh tumor samples. Here, we attempt to bypass limitations of abundant tumor source and predetermined immune selection by in vivo propagating patient-derived xenografts (PDX) from human malignant rhabdoid tumor (MRT), a rare and lethal pediatric neoplasm, to an advanced state in which most cells behave as CSCs. Stemness is then probed by comparative transcriptomics of serial PDXs generating a gene signature of epithelial to mesenchymal transition, invasion/motility, metastasis, and self-renewal, pinpointing putative MRT CSC markers. The relevance of these putative CSC molecules is analyzed by sorting tumorigenic fractions from early-passaged PDX according to one such molecule, deciphering expression in archived primary tumors, and testing the effects of CSC molecule inhibition on MRT growth. Using this platform, we identify ALDH1 and lysyl oxidase (LOX) as relevant targets and provide a larger framework for target and drug discovery in rare pediatric cancers.

•

Human malignant rhabdoid tumor (MRT) can be propagated in vivo as tumor xenografts

•

Long-term propagated PDX enrich for CSC frequency with no need for immune selection

•

Distinct gene signature in stem-like MRT xenografts reveals putative CSC biomarkers

•

Screening of putative CSC biomarkers allows identification of therapeutic targets

Geometry of Gene Expression Space of Wilms' Tumors From Human Patients

Wilms' tumor is a pediatric malignancy that is thought to originate from faulty kidney development during the embryonic stage. However, there is a large variation between tumors from different patients in both histology and gene expression that is not well characterized. Here we use a meta-analysis of published microarray datasets to show that Favorable Histology Wilms' Tumors (FHWT's) fill a triangle-shaped continuum in gene expression space of which the vertices represent three idealized “archetypes”. We show that these archetypes have predominantly renal blastemal, stromal, and epithelial characteristics and that they correlate well with the three major lineages of the developing embryonic kidney. Moreover, we show that advanced stage tumors shift towards the renal blastemal archetype. These results illustrate the potential of this methodology for characterizing the cellular composition of Wilms' tumors and for assessing disease progression.

PEGylated dendritic polyglycerol conjugate targeting NCAM-expressing neuroblastoma: Limitations and challenges

Neural cell adhesion molecule (NCAM) is found to be a stem-cell marker in several tumor types and its overexpression is known to correlate with increased metastatic capacity. To combine extravasation- and ligand-dependent targeting to NCAM overexpressing-cells in the tumor microenvironment, we developed a PEGylated NCAM-targeted dendritic polyglycerol (PG) conjugate. Here, we describe the synthesis, physico-chemical characterization and biological evaluation of a PG conjugate bearing the mitotic inhibitor paclitaxel (PTX) and an NCAM-targeting peptide (NTP). PG-NTP-PTX-PEG was evaluated for its ability to inhibit neuroblastoma progression in vitro and in vivo as compared to non-targeted derivatives and free drug. NCAM-targeted conjugate inhibited the migration of proliferating endothelial cells, suggesting it would be able to inhibit tumor angiogenesis. The targeting conjugate provided an improved binding and uptake on IMR-32 cells compared to non-targeted control. However, these results did not translate to our in vivo model on orthotopic neuroblastoma bearing mice.

Biomarker discovery for renal cancer stem cells

Characterised by high intra- and inter-tumor heterogeneity, metastatic renal cell carcinoma (RCC) is resistant to chemo- and radiotherapy. Therefore, the development of new prognostic and diagnostic markers for RCC patients is needed. Cancer stem cells (CSCs) are a small population of neoplastic cells within a tumor which present characteristics reminiscent of normal stem cells. CSCs are characterised by unlimited cell division, maintenance of the stem cell pool (self-renewal), and capability to give rise to all cell types within a tumor; and contribute to metastasis in vivo (tumourigenicity), treatment resistance and recurrence. So far, many studies have tried to establish unique biomarkers to identify CSC populations in RCC. At the same time, different approaches have been developed with the aim to isolate CSCs. Consequently, several markers were found to be specifically expressed in CSCs and cancer stem-like cells derived from RCC such as CD105, ALDH1, OCT4, CD133, and CXCR4. However, the contribution of genetic and epigenetic mechanisms, and tumor microenvironment, to cellular plasticity have made the discovery of unique biomarkers a very difficult task. In fact, contrasting results regarding the applicability of such markers to the isolation of renal CSCs have been reported in the literature. Therefore, a better understanding of the mechanism underlying CSC may help dissecting tumor heterogeneity and drug treatment efficiency.

Identification of new genes associated to senescent and tumorigenic phenotypes in mesenchymal stem cells

Although human mesenchymal stem cells (hMSCs) are a powerful tool for cell therapy, prolonged culture times result in replicative senescence or acquisition of tumorigenic features. To identify a molecular signature for senescence, we compared the transcriptome of senescent and young hMSCs with normal karyotype (hMSCs/n) and with a constitutional inversion of chromosome 3 (hMSC/inv). Senescent and young cells from both lineages showed differentially expressed genes (DEGs), with higher levels in senescent hMSCs/inv. Among the 30 DEGs in senescent hMSC/inv, 11 are new candidates for biomarkers of cellular senescence. The functional categories most represented in senescent hMSCs were related to cellular development, cell growth/proliferation, cell death, cell signaling/interaction, and cell movement. Mapping of DEGs onto biological networks revealed matrix metalloproteinase-1, thrombospondin 1, and epidermal growth factor acting as topological bottlenecks. In the comparison between senescent hMSCs/n and senescent hMSCs/inv, other functional annotations such as segregation of chromosomes, mitotic spindle formation, and mitosis and proliferation of tumor lines were most represented. We found that many genes categorized into functional annotations related to tumors in both comparisons, with relation to tumors being highest in senescent hMSCs/inv. The data presented here improves our understanding of the molecular mechanisms underlying the onset of cellular senescence as well as tumorigenesis.

Frizzled 8 promotes the cell proliferation and metastasis of renal cell carcinoma

Recent reports have shown a rapid rise in the incidence of renal cell carcinoma (RCC), and Wnt (Wingless-related integration site) signaling pathway is important in RCC. Frizzled 8 (FZD8) is a member of Frizzled (FZD) receptor family which could activate canonical or non-canonical Wnt/β-catenin pathways. Nevertheless, the role of FZD8 in RCC is poorly investigated. The immunohistochemical analysis showed high expression of FZD8 in RCC tissues compared with peri-tumor tissues. FZD8 knockdown decreased the ability of proliferation and metastasis of RCC cells. Research revealed that the FZD8 regulated the transcription of Cyclin D1, c-Myc, and could promote the epithelial to mesenchymal transition (EMT) by mediating Vimentin and Snail through the Wnt/β-catenin signaling pathway. In addition, the results of our experiment revealed that FZD8 is involved in the regulation of non-canonical Wnt signaling pathway. These data suggested that the expression of FZD8 may play an important role in the proliferation and metastasis of RCC, and serve as a putative promising drug target for human RCC therapy.

Peroxisome proliferator-activated receptor gamma (PPARγ) is central to the initiation and propagation of human angiomyolipoma, suggesting its potential as a therapeutic target

Angiomyolipoma (AML), the most common benign renal tumor, can result in severe morbidity from hemorrhage and renal failure. While mTORC1 activation is involved in its growth, mTORC1 inhibitors fail to eradicate AML, highlighting the need for new therapies. Moreover, the identity of the AML cell of origin is obscure. AML research, however, is hampered by the lack of in vivo models. Here, we establish a human AML‐xenograft (Xn) model in mice, recapitulating AML at the histological and molecular levels. Microarray analysis demonstrated tumor growth in vivo to involve robust PPARG‐pathway activation. Similarly, immunostaining revealed strong PPARG expression in human AML specimens. Accordingly, we demonstrate that while PPARG agonism accelerates AML growth, PPARG antagonism is inhibitory, strongly suppressing AML proliferation and tumor‐initiating capacity, via a TGFB‐mediated inhibition of PDGFB and CTGF. Finally, we show striking similarity between AML cell lines and mesenchymal stem cells (MSCs) in terms of antigen and gene expression and differentiation potential. Altogether, we establish the first in vivo human AML model, which provides evidence that AML may originate in a PPARG‐activated renal MSC lineage that is skewed toward adipocytes and smooth muscle and away from osteoblasts, and uncover PPARG as a regulator of AML growth, which could serve as an attractive therapeutic target.

Rapid deterioration of preexisting renal insufficiency after autologous mesenchymal stem cell therapy

Administration of autologous mesenchymal stem cells (MSCs) has been shown to improve renal function and histological findings in acute kidney injury (AKI) models. However, its effects in chronic kidney disease (CKD) are unclear, particularly in the clinical setting. Here, we report our experience with a CKD patient who was treated by intravenous infusion of autologous MSCs derived from adipose tissue in an unknown clinic outside of Korea. The renal function of the patient had been stable for several years before MSC administration. One week after the autologous MSC infusion, the preexisting renal insufficiency was rapidly aggravated without any other evidence of AKI. Hemodialysis was started 3 months after MSC administration. Renal biopsy findings at dialysis showed severe interstitial fibrosis and inflammatory cell infiltration, with a few cells expressing CD34 and CD117, 2 surface markers of stem cells. This case highlights the potential nephrotoxicity of autologous MSC therapy in CKD patients.

Evidence of In Vitro Preservation of Human Nephrogenesis at the Single-Cell Level

During nephrogenesis, stem/progenitor cells differentiate and give rise to early nephron structures that segment to proximal and distal nephron cell types. Previously, we prospectively isolated progenitors from human fetal kidney (hFK) utilizing a combination of surface markers. However, upon culture nephron progenitors differentiated and could not be robustly maintained in vitro. Here, by culturing hFK in a modified medium used for in vitro growth of mouse nephron progenitors, and by dissection of NCAM⁺/CD133⁻ progenitor cells according to EpCAM expression (NCAM⁺/CD133⁻/EpCAM⁻, NCAM⁺/CD133⁻/EpCAM^dim, NCAM⁺/CD133⁻/EpCAM^bright), we show at single-cell resolution a preservation of uninduced and induced cap mesenchyme as well as a transitioning mesenchymal-epithelial state. Concomitantly, differentiating and differentiated epithelial lineages are also maintained. In vitro expansion of discrete stages of early human nephrogenesis in nephron stem cell cultures may be used for drug screening on a full repertoire of developing kidney cells and for prospective isolation of mesenchymal or epithelial renal lineages for regenerative medicine.

•

mNPEM enables in vitro preservation of human renal embryonic CM and epithelia

•

EpCAM allows further dissection of expanded NCAM⁺CD133⁻ early nephric population

•

Single-cell analysis unveils a continuous lineage hierarchy in nephrogenesis and WT

•

Splice isoform switching confirms a unified MET hierarchy in nephrogenesis and WT

Role of CD56 in Normal Kidney Development and Wilms Tumorigenesis

The cell-surface glycoprotein CD56 has three major isoforms that play important roles in cell adhesion and signaling, which may promote cell proliferation, differentiation, survival, or migration. It is an important molecule in normal kidney development and acts as a key marker in Wilms tumor stem and progenitor cells. Here, we review the structural and genetic features of the CD56 glycoprotein, and summarize its roles in the normal versus diseased metanephric blastema. We discuss areas of CD56-related research that may complement or improve existing Wilms tumor treatment strategies, including the antibody-drug conjugate lorvotuzumab mertansine that binds to CD56.

Dissecting Stages of Human Kidney Development and Tumorigenesis with Surface Markers Affords Simple Prospective Purification of Nephron Stem Cells

When assembling a nephron during development a multipotent stem cell pool becomes restricted as differentiation ensues. A faulty differentiation arrest in this process leads to transformation and initiation of a Wilms’ tumor. Mapping these transitions with respective surface markers affords accessibility to specific cell subpopulations. NCAM1 and CD133 have been previously suggested to mark human renal progenitor populations. Herein, using cell sorting, RNA sequencing, in vitro studies with serum-free media and in vivo xenotransplantation we demonstrate a sequential map that links human kidney development and tumorigenesis; In nephrogenesis, NCAM1⁺CD133⁻ marks SIX2⁺ multipotent renal stem cells transiting to NCAM1⁺CD133⁺ differentiating segment-specific SIX2⁻ epithelial progenitors and NCAM1⁻CD133⁺ differentiated nephron cells. In tumorigenesis, NCAM1⁺CD133⁻ marks SIX2⁺ blastema that includes the ALDH1⁺ WT cancer stem/initiating cells, while NCAM1⁺CD133⁺ and NCAM1⁻CD133⁺ specifying early and late epithelial differentiation, are severely restricted in tumor initiation capacity and tumor self-renewal. Thus, negative selection for CD133 is required for defining NCAM1⁺ nephron stem cells in normal and malignant nephrogenesis.

The high expressed serum soluble neural cell adhesion molecule, a high risk factor indicating hepatic encephalopathy in hepatocelular carcinoma patients

OBJECTIVE

To investigate whether the expression of serum soluble neural cell adhesion molecule (sNCAM) is associated with hepatic encephalopathy (HE) in hepatocelular carcinoma (HCC) patients.

MATERIALS AND METHODS

The Oncomine Cancer Microarray database was used to determine the clinical relevance of NCAM expression in different kinds of human cancers. Sera from 75 HCC cases enrolled in this study were assessed for expression of sNCAM by enzyme linked immunosorbent assay (ELISA).

RESULTS

Dependent on the Oncomine Cancer Microarray database analysis, NCAM was down regulated in 10 different kinds of cancer, like bladder cancer, brain and central nervous system cancer, while up-regulated in lung cancer, uterine corpus leiomyoma and sarcoma, compared to normal groups. Puzzlingly, NCAM expression demonstrated no significant difference between normal and HCC groups. However, we found by quantitative ELISA that the level of sNCAM in sera from HCC patients with HE (347.4±151.9 ng/ml) was significantly more up-regulated than that in HCC patients without HE (260.3±104.2 ng/ml), the p-value being 0.008. sNCAM may be an important risk factor of HE in HCC patients, the correlation coefficients was 0.278 (P< 0.05) on rank correlation analysis.

CONCLUSIONS

This study highlights that up-regulated level of serum sNCAM is associated with HE in HCC patients and suggests that the high expression can be used as an indicator.

The microRNA regulatory network: a far-reaching approach to the regulate the Wnt signaling pathway in number of diseases

Wnt signaling pathway plays an important role in cell renewal, tumorigenesis, organogenesis, bone formation and bone resorption. Wnt signaling pathway is divided into two outlets: Wnt-β-catenin pathway (canonical pathway) and Wnt-calcium pathway (non-canonical pathway). miRNAs play a key role in the regulation of Wnt signaling pathway. In this review, we highlight the basic indulgent of miRNAs-mediated regulation of Wnt signaling pathway. We focus on the role of miRNAs at different levels of Wnt signaling: signaling molecules, their associated signaling proteins, regulatory proteins, transcription factors and related cytokines. Finally, we concluded that these multiple levels of targeting may have diagnostic potential as well as therapeutic prospective in future treatment.

Construction and Deciphering of Human Phosphorylation-Mediated Signaling Transduction Networks

Protein phosphorylation is the most abundant reversible covalent modification. Human protein kinases participate in almost all biological pathways, and approximately half of the kinases are associated with disease. PhoSigNet was designed to store and display human phosphorylation-mediated signal transduction networks, with additional information related to cancer. It contains 11 976 experimentally validated directed edges and 216 871 phosphorylation sites. Moreover, 3491 differentially expressed proteins in human cancer from dbDEPC, 18 907 human cancer variation sites from CanProVar, and 388 hyperphosphorylation sites from PhosphoSitePlus were collected as annotation information. Compared with other phosphorylation-related databases, PhoSigNet not only takes the kinase-substrate regulatory relationship pairs into account, but also extends regulatory relationships up- and downstream (e.g., from ligand to receptor, from G protein to kinase, and from transcription factor to targets). Furthermore, PhoSigNet allows the user to investigate the impact of phosphorylation modifications on cancer. By using one set of in-house time series phosphoproteomics data, the reconstruction of a conditional and dynamic phosphorylation-mediated signaling network was exemplified. We expect PhoSigNet to be a useful database and analysis platform benefiting both proteomics and cancer studies.

Clinicopathological significance of CD133 and CD44 expression in infiltrating ductal carcinoma and their relationship to angiogenesis

BACKGROUND

Breast cancer is the leading cause of cancer death in females worldwide, and the majority type is infiltrating ductal carcinoma (IDC). Most of IDC patients died of metastasis and recurrence. Cancer stem cells (CSCs) are defined with the ability to be self-renewal and potentially promote proliferation and formation of tumors. CSCs are related to angiogenesis and are important targets in new cancer treatment strategies. In this study, we purposed to investigate on expression and clinical significances of CSCs marked by CD133 and CD44 in IDC and their relationship to angiogenesis.

METHODS

The specimens of IDC from 325 Chinese patients with follow-up were analyzed for CD133, CD44, CD82, and CD34 protein expression by immunohistochemical staining. The Pearson chi-square test and t test were used to assess the associations among the positive staining of these markers and clinicopathological characteristics. Postoperative overall survival time in these patients with IDC was analyzed by univariate and multivariate analyses.

RESULTS

In IDC tissues, positive rates of 48.6%, 53.8%, and 42.2% were obtained for CD133, CD44, and CD82 protein, respectively; the mean score of microvessel density (MVD) was 20.5 ± 7.0 in IDC group. And there was a significant difference between the two groups. There was a positive relationship between the expression of CD133, CD44, and the score of MVD and the grades of tumor, lymph node metastasis, tumor-node-metastasis (TNM) stages (all P < 0.05); and the expression of CD82 was negatively related to grades of tumor, lymph node metastasis, and TNM stages (all P < 0.05). The overall mean survival time of the patients with CD133, CD44, and the score of MVD (≥21) positive expression was lower than that of patients with negative expression. The overall mean survival time of patients of CD82-positive expression was longer than that of patients of the negative expression group. The positive expression of CD133 and CD82, and TNM stages were independent prognostic factors of IDC (P < 0.05).

CONCLUSIONS

CSCs, angiogenesis, and aberrant expression of CD82 may be involved in the initiation, development, metastasis, and recurrence. It is suggested that CSCs, angiogenesis, and CD82 be possible as a therapeutic marker for anti-tumor therapy.

CITED1 confers stemness to Wilms tumor and enhances tumorigenic responses when enriched in the nucleus

Wilms tumor (WT) is the most common childhood kidney cancer and retains gene expression profiles reminiscent of the embryonic kidney. We have shown previously that CITED1, a transcriptional regulator that labels the self-renewing, multipotent nephron progenitor population of the developing kidney, is robustly expressed across all major WT disease and patient characteristics. In this malignant context, CITED1 becomes enriched in the nucleus, which deviates from its cytosolic predominance in embryonic nephron progenitors. We designed the current studies to test the functional and mechanistic effects of differential CITED1 subcellular localization on WT behavior. To mimic its subcellular distribution observed in clinical WT specimens, CITED1 was misexpressed ectopically in the human WT cell line, WiT49, as either a wild-type (predominantly cytosolic) or a mutant, but transcriptionally active, protein (two point mutations in its nuclear export signal, CITED1ΔNES; nuclear-enriched). In vitro analyses showed that CITED1ΔNES enhanced WiT49 proliferation and colony formation in soft agar relative to wild-type CITED1 and empty vector controls. The nuclear-enriched CITED1ΔNES cell line showed the greatest tumor volumes after xenotransplantation into immunodeficient mice (n=15 animals per cell line). To elucidate CITED1 gene targets in this model, microarray profiling showed that wildtype CITED1 foremost upregulated LGR5 (stem cell marker), repressed CDH6 (early marker of epithelial commitment of nephron progenitors), and altered expression of specific WNT pathway participants. In summary, forced nuclear enrichment of CITED1 in a human WT cell line appears to enhance tumorigenicity, whereas ectopic cytosolic expression confers stem-like properties and an embryonic phenotype, analogous to the developmental context.

SIX2 Effects on Wilms Tumor Biology

Wilms tumor (WT) blastema retains gene expression profiles characteristic of the multipotent nephron progenitor pool, or cap mesenchyme (CM), in the developing kidney. As a result, WT blastema and the CM are believed to represent contextual analogues of one another. Sine oculis homeobox 2 (SIX2) is a transcription factor expressed specifically in the CM, provides a critical mechanism for CM self-renewal, and remains persistently active in WT blastema, although its purpose in this childhood malignancy remains unclear. We hypothesized that SIX2, analogous to its function in development, confers a survival pathway to blastema, the putative WT stem cell. To test its functional significance in WT biology, wild-type SIX2 was overexpressed in the human WT cell line, WiT49. After validating this model, SIX2 effects on anchorage-independent growth, proliferation, invasiveness, canonical WNT pathway signaling, and gene expression of specific WNT pathway participants were evaluated. Relative to controls, WiT49 cells overexpressing SIX2 showed significantly enhanced anchorage-independent growth and early-passage proliferation representing surrogates of cell survival. Interestingly, overexpression of SIX2 generally repressed TCF/LEF-dependent canonical WNT signaling, which activates and coordinates both differentiation and stem pathways, but significantly heightened canonical WNT signaling through the survivin promoter, a mechanism that exclusively maintains the stem state. In summary, when overexpressed in a human WT cell line, SIX2 enhances cell survival and appears to shift the balance in WNT/β-catenin signaling away from a differentiation path and toward a stem cell survival path.

The glomerular parietal epithelial cell's responses are influenced by SM22 alpha levels

Background

Studies have shown in several diseases initially affecting podocytes, that the neighboring glomerular parietal epithelial cells (PECs) are secondarily involved. The PEC response might be reparative under certain circumstances, yet injurious under others. The factors governing these are not well understood. We have shown that SM22α, an actin-binding protein considered a marker of smooth muscle differentiation, is upregulated in podocytes and PECs in several models of podocyte disease. However, the impact of SM22α levels on PECs is not known.

Methods

Experimental glomerular disease, characterized by primary podocyte injury, was induced in aged-matched SM22α +/+ and SM22α -/- mice by intraperitoneal injection of sheep anti-rabbit glomeruli antibody. Immunostaining methods were employed on days 7 and 14 of disease.

Results

The number of PEC transition cells, defined as cells co-expressing a PEC protein (PAX2) and podocyte protein (Synaptopodin) was higher in diseased SM22α -/- mice compared with SM22α +/+ mice. WT1 staining along Bowman’s capsule is higher in diseased SM22α -/- mice. This was accompanied by increased PEC proliferation (measured by ki-67 staining), and an increase in immunostaining for the progenitor marker NCAM, in a subpopulation of PECs in diseased SM22α -/- mice. In addition, immunostaining for vimentin and alpha smooth muscle actin, markers of epithelial-to-mesenchymal transition (EMT), was lower in diseased SM22α -/- mice compared to diseased SM22α+/+ mice.

Conclusion

SM22α levels may impact how PECs respond following a primary podocyte injury in experimental glomerular disease. Absent/lower levels favor an increase in PEC transition cells and PECs expressing a progenitor marker, and a lower EMT rate compared to SM22α +/+ mice, where SM22 levels are markedly increased in PECs.

Kidney stem cells in development, regeneration and cancer

The generation of nephrons during development depends on differentiation via a mesenchymal to epithelial transition (MET) of self-renewing, tissue-specific stem cells confined to a specific anatomic niche of the nephrogenic cortex. These cells may transform to generate oncogenic stem cells and drive pediatric renal cancer. Once nephron epithelia are formed the view of post-MET tissue renal growth and maintenance by adult tissue-specific epithelial stem cells becomes controversial. Recently, genetic lineage tracing that followed clonal evolution of single kidney cells showed that the need for new cells is constantly driven by fate-restricted unipotent clonal expansions in varying kidney segments arguing against a multipotent adult stem cell model. Lineage-restriction was similarly maintained in kidney organoids grown in culture. Importantly, kidney cells in which Wnt was activated were traced to give significant clonal progeny indicating a clonogenic hierarchy. In vivo nephron epithelia may be endowed with the capacity akin to that of unipotent epithelial stem/progenitor such that under specific stimuli can clonally expand/self renew by local proliferation of mature differentiated cells. Finding ways to ex vivo preserve and expand the observed in vivo kidney-forming capacity inherent to both the fetal and adult kidneys is crucial for taking renal regenerative medicine forward. Some of the strategies used to achieve this are sorting human fetal nephron stem/progenitor cells, growing adult nephrospheres or reprogramming differentiated kidney cells toward expandable renal progenitors.

Targeted therapy aimed at cancer stem cells: Wilms' tumor as an example

Wilms' tumor (WT), a common renal pediatric solid tumor, serves as a model for a malignancy formed by renal precursor cells that have failed to differentiate properly. Here we review recent evidence showing that the tumors' heterogeneous cell population contains a small fraction of cancer stem cells (CSC) identified by two markers: Neural Cell Adhesion Molecule 1 (NCAM1) expression and Aldehyde dehydrogenase 1 (ALDH1) enzymatic activity. In vivo studies show these CSCs to both self-renew and differentiate to give rise to all tumor components. Similar to other malignancies, the identification of a specific CSC fraction has allowed the examination of a novel targeted therapy, aimed at eradicating the CSC population. The loss of CSCs abolishes the tumor's ability to sustain and propagate, hence, causing tumor degradation with minimal damage to normal tissue.

Race disparities in peptide profiles of North American and Kenyan Wilms tumor specimens

BACKGROUND

Wilms tumor (WT) is the most common childhood kidney cancer worldwide and arises in children of black African ancestry with greater frequency and severity than other race groups. A biologic basis for this pediatric cancer disparity has not been previously determined. We hypothesized that unique molecular fingerprints might underlie the variable incidence and distinct disease characteristics of WT observed between race groups.

STUDY DESIGN

To evaluate molecular disparities between WTs of different race groups, the Children's Oncology Group provided 80 favorable histology specimens divided evenly between black and white patients and matched for disease characteristics. As a surrogate of black sub-Saharan African patients, we also analyzed 18 Kenyan WT specimens. Tissues were probed for peptide profiles using matrix-assisted laser desorption ionization time of flight imaging mass spectrometry. To control for histologic variability within and between specimens, cellular regions were analyzed separately as triphasic (containing blastema, epithelia, and stroma), blastema only, and stroma only. Data were queried using ClinProTools and statistically analyzed.

RESULTS

Peptide profiles, detected in triphasic WT regions, recognized race with good accuracy, which increased for blastema- or stroma-only regions. Peptide profiles from North American WTs differed between black and white race groups but were far more similar in composition than Kenyan specimens. Individual peptides were identified that also associated with WT patient and disease characteristics (eg, treatment failure and stage). Statistically significant peptide fragments were used to sequence proteins, revealing specific cellular signaling pathways and candidate drug targets.

CONCLUSIONS

Wilms tumor specimens arising among different race groups show unique molecular fingerprints that could explain disparate incidences and biologic behavior and that could reveal novel therapeutic targets.

Metastasis-Initiating Cells in Renal Cancer

Metastasis is a complex process that propagates cells from the primary or initial site of the cancer occurrence to distant parts of the body. Cancer cells break from the cancer site and circulate through the bloodstream or lymph vessels, allowing them to reach nearly all parts of the body. These circulating tumour cells (CTCs) contain specialized metastasis-initiating cells (MICs) that reside in the biological heterogeneous primary tumour. Researchers have hypothesized that metastasis of renal cell carcinoma is initiated by circulation of MICs in patients’ blood and bone marrow. Based on the cancer stem/progenitor cell concept of carcinogenesis, understanding the molecular phenotypes of metastasis-initiating cells (MICs) in renal cancer could play a vital role in developing strategies for therapeutic interventions in renal cancer. Existence of MICs among CTCs in renal carcinoma has not been proven in large scale. However, some studies have reported that specialized markers are found on the surface of circulating cells from the primary tumour. In mice, MICs have been isolated from CTCs using such markers, which have then been transplanted into xenograft model to show whether they give rise to metastasis in different organs. Considering these findings, in this review we have attempted to summarize the studies connected with MICs and their gene expression profiles that are responsible for metastasis in renal cancer.

Reactivation of NCAM1 defines a subpopulation of human adult kidney epithelial cells with clonogenic and stem/progenitor properties

The nephron is composed of a monolayer of epithelial cells that make up its various compartments. In development, these cells begin as mesenchyme. NCAM1, abundant in the mesenchyme and early nephron lineage, ceases to express in mature kidney epithelia. We show that, once placed in culture and released from quiescence, adult human kidney epithelial cells (hKEpCs), uniformly positive for CD24/CD133, re-express NCAM1 in a specific cell subset that attains a stem/progenitor state. Immunosorted NCAM1(+) cells overexpressed early nephron progenitor markers (PAX2, SALL1, SIX2, WT1) and acquired a mesenchymal fate, indicated by high vimentim and reduced E-cadherin levels. Gene expression and microarray analysis disclosed both a proximal tubular origin of these cells and molecules regulating epithelial-mesenchymal transition. NCAM1(+) cells generated clonal progeny when cultured in the presence of fetal kidney conditioned medium, differentiated along mesenchymal lineages but retained the unique propensity to generate epithelial kidney spheres and produce epithelial renal tissue on single-cell grafting in chick CAM and mouse. Depletion of NCAM1(+) cells from hKEpCs abrogated stemness traits in vitro. Eliminating these cells during the regenerative response that follows glycerol-induced acute tubular necrosis worsened peak renal injury in vivo. Thus, higher clone-forming and developmental capacities characterize a distinct subset of adult kidney-derived cells. The ability to influence an endogenous regenerative response via NCAM1 targeting may lead to novel therapeutics for renal diseases.

Chromatin-modifying agents reactivate embryonic renal stem/progenitor genes in human adult kidney epithelial cells but abrogate dedifferentiation and stemness

Recent studies have suggested that epigenetic modulation with chromatin-modifying agents can induce stemness and dedifferentiation and increase developmental plasticity. For instance, valproic acid (VPA), a histone deacetylase (HDAC) inhibitor, has been shown to promote self-renewal/expansion of hematopoietic stem cells and facilitate the generation of induced pluripotent stem cells (iPSCs). Previously, we observed that downregulation of embryonic renal stem/progenitor genes in the adult kidney was associated, at least in part, with epigenetic silencing. Therefore, we hypothesized that VPA may alter the expression of these genes and reprogram mature human adult kidney epithelial cells (hKEpCs) to a stem/progenitor-like state. Here, using quantitative RT-PCR and flow cytometry [fluorescence-activated cell sorting (FACS)] analysis, we show in VPA-treated primary cultures of human adult and fetal kidney significant reinduction of the renal stem/progenitor markers SIX2, OSR1, SALL1, NCAM, and PSA-NCAM. Robust SIX2 mRNA re-expression was confirmed at the protein level by western blot and was associated with epigenetic changes of the histones at multiple sites of the SIX2 promoter leading to gene activation, significantly increased acetylation of histones H4, and methylation of lysine 4 on H3. Furthermore, we could demonstrate synergistic effects of VPA and Wnt antagonists on SIX2 and also OSR1 reinduction. Nevertheless, VPA resulted in upregulation of E-CADHERIN and reduction in VIMENTIN, preventing the skewing of hKEpCs towards a more replicative mesenchymal state required for clonogenic expansion and acquisition of stem cell characters, altogether inducing cell senescence at early passages. These results demonstrating that chromatin-modifying agents prevent dedifferentiation of hKEpCs have important clinical implications as they may limit ex-vivo self-renewal/expansion and possibly the in vivo renal regenerative capacity initiated by dedifferentiation.

Differential expression of STAT1 and IFN-γ in primary and invasive or metastatic wilms tumors

BACKGROUND AND OBJECTIVES

IFN/STAT1 signaling has been found to be not only associated with an aggressive tumor phenotype but also activated and functional during metanephric development. This study was undertaken to evaluate STAT1 and IFN-γ expression and its relation to histopathological features of primary and invasive/metastatic Wilms tumors.

METHODS

Immunohistochemistry was used to determine the expression and cellular distribution of STAT1 and IFN-γ in 18 pairs of primary and corresponding invasive/metastatic Wilms tumors and 40 primary tumors without invasion or metastasis.

RESULTS

Positive rate of STAT1/IFN-γ expression was 66.7%/61.1% and 72.2%/77.8% in 18 pairs of primary and associated invasive/metastatic Wilms tumor tissues, while 35.0%/27.5% in 40 primary tumors without invasion or metastasis. The expression of STAT1 and IFN-γ was significantly associated with invasion/metastasis (P = 0.025; P = 0.015). There was a positive correlation between STAT1 and IFN-γ expression in all Wilms tumor tissues (χ(2)  = 23.408, P = 0.05, r = 0.555). The expression of STAT1 and IFN-γ between primary and matched invasive/metastatic tissues was concordance, respectively (P = 0.710 and P = 0.375).

CONCLUSIONS

These results suggest that IFN-γ/STAT1 signaling might have clinical potential as a promising predictor to identify individuals with poor prognostic potential and as a possible novel target molecule of therapy for Wilms tumor.

Expression of stem cell markers, CD133 and CD44, in pediatric solid tumors: a study using tissue microarray

Based on the cancer stem cell (CSC) concept model, a small population of cells with unique self-renewal properties and malignant potential exists in tumors. Immunohistochemistry was performed to detect the expression of CSC markers, CD133 and CD44, in a series of pediatric tumors. The association between expression of these markers and tumor characteristics was then analyzed. In Wilms tumors (WT), a significant positive correlation was found between expression of CD133 and the National Wilms Tumor Stage (NWTS) (p = 0.047). In neuroblastomas (NB), expression of CD133 was positively correlated with the International Neuroblastoma Staging System (INSS) (p-value = 0.012), indicating that the rate of CD133 positivity increased with the stage of these tumors. CD133, as a putative stem cell marker, is associated with more advanced stages of Wilms and NB tumors; therefore, this molecule can be a potential clinical prognostic marker in children suffering from NB or Wilms tumor.

Biological characteristics of Rh123high stem-like cells in a side population of 786-O renal carcinoma cells

The aim of the present study was to investigate the differences in biological characteristics between the rhodamine 123 (Rh123)^high and Rh123^low subpopulations of the renal cancer cell line 786-O and to identify evidence for the existence of cancer stem cells in renal cell carcinoma (RCC) cells. In vitro cultured RCC 786-O cells were stained with Rh123, analyzed and sorted with flow cytometry. The differences in proliferative activity, long-term differentiation and radiation sensitivity between the two subpopulations were measured and the oncogenicity of each subpopulation was evaluated according to their neoplastic growth ability in soft agar and tumor-forming ability in NOD/SCID immunodeficient mice. There were two subpopulations in the cultured 786-O cells, Rh123^high and Rh123^low cells. Rh123^low cells were the majority among 786-O renal carcinoma cells and barely formed solid tumors in NOD/SCID mice and colonies in soft agar. By contrast, the Rh123^high cells were the minority, exhibited high proliferative activity, differentiation ability and resistance to radiation and showed high tumorigenesis potential and colony forming efficiency. The Rh123^high cells had stem-like characteristics in cultured RCC 786-O cells in vitro.

Chronic exposure of renal stem cells to inorganic arsenic induces a cancer phenotype

Inorganic arsenic in the drinking water is a multisite human carcinogen that potentially targets the kidney. Recent evidence also indicates that developmental arsenic exposure impacts renal carcinogenesis in humans and mice. Emerging theory indicates that cancer may be a disease of stem cells (SCs) and that there are abundant active SCs during early life. Therefore, we hypothesized that inorganic arsenic targets SCs, or partially differentiated progenitor cells (PCs), for oncogenic transformation. Thus, a rat kidney SC/PC cell line, RIMM-18, was chronically exposed to low-level arsenite (500 nM) for up to 28 weeks. Multiple markers of acquired cancer phenotype were assessed biweekly during arsenic exposure, including secreted matrix metalloproteinase (MMP) activity, proliferation rate, colony formation in soft agar, and cellular invasiveness. Arsenic exposure by 10 weeks and after also induced marked and sustained increases in colony formation, indicative of the loss of contact inhibition, and increased invasiveness, both cancer cell characteristics. Compared to the passage-matched control, chronic arsenic exposure caused exposure-duration dependent increases in secreted MMP-2 and MMP-9 activity, Cox-2 expression, and more rapid proliferation (all >2-fold), characteristics typical of cancer cells. Dysregulation of SC maintenance genes and signaling pathways are common during oncogenesis. During arsenite exposure, expression of several genes associated with normal kidney development and SC regulation and differentiation (i.e., Wt-1, Wnt-4, Bmp-7, etc.) were aberrantly altered. Arsenic-exposed renal SCs produced more nonadherent spheroid bodies that grew much more aggressively in Matrigel, typical of cancer SCs (CSCs). The transformed cells also showed gene overexpression typical of renal SCs/CSCs (CD24, Osr1, Ncam) and arsenic adaptation such as overexpression of Mt-1, Mt2, Sod-1, and Abcc2. These data suggest that inorganic arsenic induced an acquired cancer phenotype in vitro in these rat kidney SCs potentially forming CSCs and, consistent with data in vivo, indicate that these multipotent SCs may be targets of arsenic during renal carcinogenesis.

CD133 marks a myogenically primitive subpopulation in rhabdomyosarcoma cell lines that are relatively chemoresistant but sensitive to mutant HSV

BACKGROUND

Rhabdomyosarcoma (RMS) is characterized by features of skeletal muscle and is comprised of two major histological subtypes, embryonal (E-RMS), and alveolar (A-RMS). Subsets of each RMS subtype demonstrate resistance to multimodal therapy leading to treatment failure. Cancer stem cells or cancer-initiating cells (CIC) represent a theorized population of cells that give rise to tumors and are responsible for treatment resistance.

PROCEDURE

We investigated the ability of CD133, a putative CIC marker, to distinguish a chemoresistant, myogenically primitive population in alveolar (RH30), and embryonal (RD) RMS cell lines. We tested CD133+/- cells for sensitivity to engineered herpes simplex virus (oHSV).

RESULTS

Relative to CD133- cells, CD133+ A-RMS, and E-RMS cells demonstrate an enhanced colony-forming ability, are less differentiated myogenically, and are more resistant to cytotoxic chemotherapy but equally sensitive to oHSV oncolysis. Compared to CD133- RD cells, CD133+ cells express relatively high levels of genes typically expressed in skeletal muscle progenitor satellite cells including PAX7, c-MET, and the GLI effectors of the hedgehog signaling pathway. In contrast, CD133+ RH30 cells were not associated with enhanced expression of satellite cell markers or Hh targets.

CONCLUSIONS

Our findings demonstrate that CD133+ cells from A-RMS and E-RMS cell lines are characterized by a myogenically primitive phenotype. These cells have the capacity to form colonies in vitro and are more resistant to chemotherapy than CD133- cells. CD133 expression may denote a subset of RMS cells with an important role in tumorigenesis and treatment failure. These resistant cells may be effectively targeted by oHSV therapy.

Hedgehog signaling pathway regulates human pancreatic cancer cell proliferation and metastasis

Pancreatic cancer is one of the most aggressive and devastating malignancies. The Hedgehog (Hh) pathway has been reported to play an important role in pancreatic cancer development and progression. The aim of this study was to examine the activation of the Hh pathway in human pancreatic cancer tissue samples and pancreatic cancer cell lines, and the molecular mechanisms involved in the Hh pathway mediated effects on pancreatic cancer cell proliferation and invasion. The expression levels of Hh molecules in human pancreatic cancer tissue samples and pancreatic cancer cell lines were evaluated using RT-PCR. The role of the Hh pathway in cell proliferation and invasion was evaluated using flow cytometry, MTT, colony formation assays and transwell invasion assays, and the expression of cancer stem cell markers and epithelial-mesenchymal transition (EMT) were evaluated using flow cytometry and RT-PCR. Tumorigenicity assays were used to further investigate the role of the Hh pathway in vivo. Hh molecules were highly expressed in human pancreatic cancer tissue samples and pancreatic cancer cell lines. Inhibition of the Hh pathway notably decreased cell proliferation and induced apoptosis through inhibition of the PI3K/AKT pathway and cancer stem cells. Furthermore, inhibition of the Hh signaling pathway significantly inhibited EMT by suppressing the activation of transcription factors Snail and Slug, which are correlated with significantly reduced pancreatic cancer cell invasion, suggesting that the Hh signaling pathway is involved in early metastasis. These results indicate that activation of the Hh pathway is a common event. Inhibition of the Hh pathway may be a potential molecular target of new therapeutic strategies for pancreatic cancer.

The isolation and characterization of renal cancer initiating cells from human Wilms' tumour xenografts unveils new therapeutic targets

There are considerable differences in tumour biology between adult and paediatric cancers. The existence of cancer initiating cells/cancer stem cells (CIC/CSC) in paediatric solid tumours is currently unclear. Here, we show the successful propagation of primary human Wilms' tumour (WT), a common paediatric renal malignancy, in immunodeficient mice, demonstrating the presence of a population of highly proliferative CIC/CSCs capable of serial xenograft initiation. Cell sorting and limiting dilution transplantation analysis of xenograft cells identified WT CSCs that harbour a primitive undifferentiated – NCAM1 expressing – “blastema” phenotype, including a capacity to expand and differentiate into the mature renal-like cell types observed in the primary tumour. WT CSCs, which can be further enriched by aldehyde dehydrogenase activity, overexpressed renal stemness and genes linked to poor patient prognosis, showed preferential protein expression of phosphorylated PKB/Akt and strong reduction of the miR-200 family. Complete eradication of WT in multiple xenograft models was achieved with a human NCAM antibody drug conjugate. The existence of CIC/CSCs in WT provides new therapeutic targets.