Characterizing cancer cells with cancer stem cell-like features in 293T human embryonic kidney cells

Profiling DNA Cargos in Single Extracellular Vesicles via Hydrogel-Based Droplet Digital Multiple Displacement Amplification

Due to the substantial heterogeneity among extracellular vesicle (EV) subpopulations, single-EV analysis has the potential to elucidate the mechanisms behind EV biogenesis and shed light on the myriad functions, leading to the development of novel diagnostics and therapeutics. While many studies have been devoted to reveal between-EV variations in surface proteins and RNAs, DNA cargos (EV-DNA) have received little attention. Here, we report a hydrogel-based droplet digital multiple displacement amplification approach for the comprehensive analysis of EV-DNA at the single-EV level. Single EVs are dispersed in thousands of hydrogel droplets and lysed for DNA amplification and identification. The droplet microfluidics strategy empowers the assay with single-molecule sensitivity and capability for absolute quantification of DNA-containing EVs. In particular, our findings indicate that 5-40% EVs are associated with DNA, depending on the cell of origin. Large EVs exhibit a higher proportion of DNA-containing EVs and a more substantial presence of intraluminal DNA, compared to small EVs. These DNA-containing EVs carry multiple DNA fragments on average. Furthermore, both double-stranded DNA and single-stranded DNA were able to be detected at the single-EV level. Utilizing this method, the abundance, distribution, and biophysical properties of EV-DNA in various EV populations are evaluated. The DNA level within EVs provides insight into the status of the originating cells and offers valuable information on the outcomes of anticancer treatments. The utilization of single-EV analysis for EV-DNA holds significant promise for early cancer detection and treatment response monitoring.

Where protein structure and cell diversity meet

Protein-protein interaction networks - interactomes - are charted with the hope to understand how phenotypes emerge and how they are altered in disease states. Early efforts to map interactomes have focused on the assembly of context agnostic, reference networks. However, recent studies have mapped interactomes across different cell lines and tissues, finding highly variable interactomes due to the rewiring of protein-protein interactions in different contexts. Increasing evidence points to significant links between protein structure and interactome diversity seen across cell types and tissues. We discuss how recent findings support the key role of alternative splicing and phosphorylation, two well-established regulators of protein structural and functional diversity, in defining cell type- and tissue-specific interactomes. Moreover, we show that intrinsically disordered protein regions are most favorably equipped to support interactome rewiring by acting as hubs of protein structure and function regulation.

Computer-Vision-Based Dielectrophoresis Mobility Tracking for Characterization of Single-Cell Biophysical Properties

Fast and precise measurements of live single-cell biophysical properties is significant in disease diagnosis, cytopathologic analysis, etc. Existing methods still suffer from unsatisfied measurement accuracy and low efficiency. We propose a computer vision method to track cell dielectrophoretic movements on a microchip, enabling efficient and accurate measurement of biophysical parameters of live single cells, including cell radius, cytoplasm conductivity, and cell-specific membrane capacitance, and in situ extraction of cell texture features. We propose a prediction-iteration method to optimize the cell parameter measurement, achieving high accuracy (less than 0.79% error) and high efficiency (less than 30 s). We further propose a hierarchical classifier based on a support vector machine and implement cell classification using acquired cell physical parameters and texture features, achieving high classification accuracies for identifying cell lines from different tissues, tumor and normal cells, different tumor cells, different leukemia cells, and tumor cells with different malignancies. The method is label-free and biocompatible, allowing further live cell studies on a chip, e.g., cell therapy, cell differentiation, etc.

Regional gain and global loss of 5-hydroxymethylcytosine coexist in genitourinary cancers and regulate different oncogenic pathways

BACKGROUND

DNA 5-hydroxymethylcytosine (5hmC) is produced by dynamic 5mC oxidation process contributing to tissue specification, and loss of 5hmC has been reported in multiple cancers including genitourinary cancers. However, 5hmC is also cell-type specific, and its variability may exist between differentiated tumor cells and cancer stem cells. Thus, cancer-associated changes in 5hmC may be contributed by distinct sets of tumor cells within the tumor tissues.

RESULTS

Here, we applied a sensitive immunoprecipitation-based method (hMeDIP-seq) to analyze 5hmC changes during genitourinary carcinogenesis (including prostate, urothelial and kidney). We confirmed the tissue-specific distribution of 5hmC in genitourinary tissues and identified regional gain and global loss of 5hmC coexisting in genitourinary cancers. The genes with gain of 5hmC during tumorigenesis were functionally enriched in regulating stemness and hypoxia, whereas were associated with poor clinical prognosis irrespective of their differences in tumor type. We identified that gain of 5hmC occurred in soft fibrin gel-induced 3D tumor spheres with a tumor-repopulating phenotype in two prostate cancer cell lines, 22RV1 and PC3, compared with conventional two-dimensional (2D) rigid dishes. Then, we defined a malignant signature derived from the differentially hydroxymethylated regions affected genes of cancer stem-like cells, which could predict a worse clinical outcome and identified phenotypically malignant populations of cells from prostate cancer tumors. Notably, an oxidation-resistant vitamin C derivative, ascorbyl phosphate magnesium, restored 5hmC and killed the cancer stem cell-like cells leading to apoptosis in prostate cancer cell lines.

CONCLUSIONS

Collectively, our study dissects the regional gain of 5hmC in maintaining cancer stem-like cells and related to poor prognosis, which provides proof of concept for an epigenetic differentiation therapy with vitamin C by 5hmC reprogramming.

Interactions between EGFR and EphA2 promote tumorigenesis through the action of Ephexin1

The cell signaling factors EGFR, EphA2, and Ephexin1 are associated with lung and colorectal cancer and play an important role in tumorigenesis. Although the respective functional roles of EGFR and EphA2 are well known, interactions between these proteins and a functional role for the complex is not understood. Here, we showed that Ephexin1, EphA2, and EGFR are each expressed at higher levels in lung and colorectal cancer patient tissues, and binding of EGFR to EphA2 was associated with both increased tumor grade and metastatic cases in both cancer types. Treatment with Epidermal Growth Factor (EGF) induced binding of the RR domain of EGFR to the kinase domain of EphA2, and this binding was promoted by Ephexin1. Additionally, the AKT-mediated phosphorylation of EphA2 (at Ser897) promoted interactions with EGFR, pointing to the importance of this pathway. Two mutations in EGFR, L858R and T790M, that are frequently observed in lung cancer patients, promoted binding to EphA2, and this binding was dependent on Ephexin1. Our results indicate that the formation of a complex between EGFR, EphA2, and Ephexin1 plays an important role in lung and colorectal cancers, and that inhibition of this complex may be an effective target for cancer therapy.

Spheroid culture models adequately imitate distinctive features of the renal cancer or melanoma microenvironment

Tumor development studies should adapt to cancer cells' specific mechanisms in connection with their microenvironment. Standard two-dimensional cultures and gas composition are not relevant to the real cancer environment. Existing three-dimensional models are often requiring sophisticated conditions. Here, we propose and characterize, in two cancer models, melanoma (B16F10) and kidney cancer (RenCa), a three-dimensional culture method, reporting the presence of hypoxia-related genes/proteins and aggressiveness mechanisms (epithelial mesenchymal transition and cancer stem cells). We validate the designed three-dimensional method by comparing it with in vivo growing tumors. The developed method brings simplicity and data reproducibility. Melanoma spheroid-growing cells reached a cell cycle arrest at the G0/G1 phase and showed induction of hypoxia. Spheroid-recovered RenCa cells were enriched in proliferating cells and displayed delayed hypoxia. Moreover, the responses to hypoxia observed in spheroids were validated by in vivo tumor studies for both lines. Three-dimensional shapes induced cancer stem cells in renal cancer, whereas epithelial to mesenchymal transition occurred in the melanoma model. Such distinction in the use of different aggressiveness-leading pathways was observed in in vivo melanoma vs kidney tumors. Thus, this 3D culture model approach is adequate to uncover crucial molecular pathways using distinct mechanisms to reach aggressiveness; i.e., B16F10 cells perform epithelial to mesenchymal transition while RenCa cells dedifferentiate into cancer stem cells. Such three-dimensional models help mimic the in vivo tumor features, i.e., hypoxia and aggressiveness mechanisms as validated here by next-generation sequencing analysis, and are proposed for further alternative methods to in vivo studies.

Spheroid Culture Differentially Affects Cancer Cell Sensitivity to Drugs in Melanoma and RCC Models

2D culture as a model for drug testing often turns to be clinically futile. Therefore, 3D cultures (3Ds) show potential to better model responses to drugs observed in vivo. In preliminary studies, using melanoma (B16F10) and renal (RenCa) cancer, we confirmed that 3Ds better mimics the tumor microenvironment. Here, we evaluated how the proposed 3D mode of culture affects tumor cell susceptibility to anti-cancer drugs, which have distinct mechanisms of action (everolimus, doxorubicin, cisplatin). Melanoma spheroids showed higher resistance to all used drugs, as compared to 2D. In an RCC model, such modulation was only observed for doxorubicin treatment. As drug distribution was not affected by the 3D shape, we assessed the expression of MDR1 and mTor. Upregulation of MDR1 in RCC spheroids was observed, in contrast to melanoma. In both models, mTor expression was not affected by the 3D cultures. By NGS, 10 genes related with metabolism of xenobiotics by cytochrome p450 were deregulated in renal cancer spheroids; 9 of them were later confirmed in the melanoma model. The differences between 3D models and classical 2D cultures point to the potential to uncover new non-canonical mechanisms to explain drug resistance set by the tumor in its microenvironment.

Ovarian Cancer and Cancer Stem Cells-Cellular and Molecular Characteristics, Signaling Pathways, and Usefulness as a Diagnostic Tool in Medicine and Oncology

Simple Summary

Ovarian cancer is still a high-risk, metastatic disease, often diagnosed at a late stage. Difficulties in its treatment are associated with high resistance to chemotherapy and recurrence. Responsible for the malignant features of cancer are considered to be cancer stem cells (CSCs), which generate new cells by modifying various signaling pathways. Signaling pathways are crucial for the regulation of epithelial-mesenchymal transition, metastasis, and self-renewal of CSCs. New therapies based on the use of inhibitors that block CSC growth and proliferation signals are being investigated. The current histological classification of ovarian tumors, their epidemiology, and the recent knowledge of ovarian CSCs, with particular emphasis on their molecular basis, are important considerations.

Abstract

Despite the increasing development of medicine, ovarian cancer is still a high-risk, metastatic disease that is often diagnosed at a late stage. In addition, difficulties in its treatment are associated with high resistance to chemotherapy and frequent relapse. Cancer stem cells (CSCs), recently attracting significant scientific interest, are considered to be responsible for the malignant features of tumors. CSCs, as the driving force behind tumor development, generate new cells by modifying different signaling pathways. Moreover, investigations on different types of tumors have shown that signaling pathways are key to epithelial-mesenchymal transition (EMT) regulation, metastasis, and self-renewal of CSCs. Based on these established issues, new therapies are being investigated based on the use of inhibitors to block CSC growth and proliferation signals. Many reports indicate that CSC markers play a key role in cancer metastasis, with hopes placed in their targeting to block this process and eliminate relapses. Current histological classification of ovarian tumors, their epidemiology, and the most recent knowledge of ovarian CSCs, with particular emphasis on their molecular background, are important aspects for consideration. Furthermore, the importance of signaling pathways involved in tumor growth, development, and metastasis, is also presented.

Activation of CXCL12-CXCR4 signalling induces conversion of immortalised embryonic kidney cells into cancer stem-like cells

Cancer stem cells (CSCs) have been implicated in the growth and progression of several types of human cancer. The technology to derive and establish CSCs in vitro could be a critical tool for understanding cancer and developing new therapeutic targets. In this study, we derived expandable CD15⁺ induced CSCs (iCSCs) from immortalised 293FT human epithelial cells by co-culture with human bone marrow-derived mesenchymal stem cells (BM-MSCs) as feeder cells in vitro. The iCSCs converted through an epithelial-mesenchymal transition program acquired mesenchymal traits, the expression of stem cell markers, and epigenetic changes. Moreover, the iCSCs not only efficiently formed tumorspheres in vitro but also initiated tumours in immunocompromised mice injected with only 10 of the iCSCs. Furthermore, we showed that the expression of the chemokine CXCL12 and its receptor CXCR4 by the iCSCs resulted in the activation of the Fut4 gene through CXCR4/ERK/ELK-1-signalling pathways and the maintenance of the iCSCs in the undifferentiated state through CXCR4/AKT/STAT3-signalling. These findings suggest that immortalised 293FT cells may acquire potential oncogenicity through molecular and cellular alteration processes in microenvironments using BM-MSCs, and could represent a valuable in vitro model as a cancer stem cell surrogate for studying the pathophysiological properties of CSCs.

The role of FOSL1 in stem-like cell reprogramming processes

Cancer stem-like cells (CSCs) have self-renewal abilities responsible for cancer progression, therapy resistance, and metastatic growth. The glioblastoma stem-like cells are the most studied among CSC populations. A recent study identified four transcription factors (SOX2, SALL2, OLIG2, and POU3F2) as the minimal core sufficient to reprogram differentiated glioblastoma (GBM) cells into stem-like cells. Transcriptomic data of GBM tissues and cell lines from two different datasets were then analyzed by the SWItch Miner (SWIM), a network-based software, and FOSL1 was identified as a putative regulator of the previously identified minimal core. Herein, we selected NTERA-2 and HEK293T cells to perform an in vitro study to investigate the role of FOSL1 in the reprogramming mechanisms. We transfected the two cell lines with a constitutive FOSL1 cDNA plasmid. We demonstrated that FOSL1 directly regulates the four transcription factors binding their promoter regions, is involved in the deregulation of several stemness markers, and reduces the cells' ability to generate aggregates increasing the extracellular matrix component FN1. Although further experiments are necessary, our data suggest that FOSL1 reprograms the stemness by regulating the core of the four transcription factors.

The small Cajal body-specific RNA 15 (SCARNA15) directs p53 and redox homeostasis via selective splicing in cancer cells

Small Cajal body-specific RNAs (scaRNAs) guide post-transcriptional modification of spliceosomal RNA and, while commonly altered in cancer, have poorly defined roles in tumorigenesis. Here, we uncover that SCARNA15 directs alternative splicing (AS) and stress adaptation in cancer cells. Specifically, we find that SCARNA15 guides critical pseudouridylation (Ψ) of U2 spliceosomal RNA to fine-tune AS of distinct transcripts enriched for chromatin and transcriptional regulators in malignant cells. This critically impacts the expression and function of the key tumor suppressors ATRX and p53. Significantly, SCARNA15 loss impairs p53-mediated redox homeostasis and hampers cancer cell survival, motility and anchorage-independent growth. In sum, these findings highlight an unanticipated role for SCARNA15 and Ψ in directing cancer-associated splicing programs.

CRISPR/Cas9 uPAR Gene Knockout Results in Tumor Growth Inhibition, EGFR Downregulation and Induction of Stemness Markers in Melanoma and Colon Carcinoma Cell Lines

uPAR is a globular protein, tethered to the cell membrane by a GPI-anchor involved in several cancer-related properties and its overexpression commonly correlates with poor prognosis and metastasis. We investigated the consequences of uPAR irreversible loss in human melanoma and colon cancer cell lines, knocking out its expression by CRISPR/Cas9. We analyzed through flow cytometry, western blotting and qPCR, the modulation of the most known cancer stem cells-associated genes and the EGFR while we observed the proliferation rate exploiting 2D and 3D cellular models. We also generated uPAR “rescue” expression cell lines as well as we promoted the expression of only its 3’UTR to demonstrate the involvement of uPAR mRNA in tumor progression. Knocking out PLAUR, uPAR-encoding gene, we observed an inhibited growth ratio unexpectedly coupled with a significant percentage of cells acquiring a stem-like phenotype. In vivo experiments demonstrated that uPAR loss completely abrogates tumorigenesis despite the gained stem-like profile. Nonetheless, we proved that the reintroduction of the 3’UTR of PLAUR gene was sufficient to restore the wild-type status validating the hypothesis that such a region may act as a “molecular sponge”. In particular miR146a, by binding PLAUR 3’ UTR region might be responsible for uPAR-dependent inhibition of EGFR expression.

Targeting Strategies for Renal Cancer Stem Cell Therapy

Renal cell carcinoma (RCC) is an intractable genitourinary malignancy that accounts for approximately 4% of adult malignancies. Currently, there is no approved targeted therapy for RCC that has yielded durable remissions, and they remain palliative in intent. Emerging evidence has indicated that renal tumorigenesis and RCC treatment-resistance may originate from renal cancer stem cells (CSCs) with tumor-initiating capacity (CSC hypothesis). A better understanding of the mechanism underlying renal CSCs will help to dissect RCC heterogeneity and drug treatment efficiency, to promote more personalized and targeted therapies. In this review, we summarized the stem cell characteristics of renal CSCs. We outlined the targeting strategies and challenges associated with developing therapies that target renal CSCs angiogenesis, immunosuppression, signaling pathways, surface biomarkers, microRNAs and nanomedicine. In conclusion, CSCs are an important role in renal carcinogenesis and represent a valid target for treatment of RCC patients.

Role of Tissue Transglutaminase Catalytic and Guanosine Triphosphate-Binding Domains in Renal Cell Carcinoma Progression

Tissue transglutaminase (TG2) is a multifunctional protein that can act as a cross-linking enzyme, GTPase/ATPase, protein kinase, and protein disulfide isomerase. TG2 is involved in cell adhesion, migration, invasion, and growth, as well as epithelial-mesenchymal transition (EMT). Our previous findings indicate that the increased expression of TG2 in renal cell carcinoma (RCC) results in tumor metastasis with a significant decrease in disease- and cancer-specific survival outcome. Given the importance of the prometastatic activity of TG2 in RCC, in the present study, we aim to investigate the relative contribution of TG2's transamidase and guanosine triphosphate (GTP)-binding/GTPase activity in the cell migration, invasion, EMT, and cancer stemness of RCC. For this purpose, the mouse RCC cell line RenCa was transduced with wild-type-TG2 (wt-TG2), GTP-binding deficient-form TG2-R580A, transamidase-deficient form with low GTP-binding affinity TG2-C277S, and transamidase-inactive form TG2-W241A. Our results suggested that predominantly, GTP-binding activity of TG2 is responsible for cell migration and invasion. In addition, CD marker analysis and spheroid assay confirmed that GTP binding/GTPase activity of TG2 is important in the maintenance of mesenchymal character and the cancer stem cell profile. These findings support a prometastatic role for TG2 in RCC that is dependent on the GTP binding/GTPase activity of the enzyme.

Current updates and future perspectives on the management of renal cell carcinoma

Renal cell carcinoma (RCC) refers to renal-epithelial cancer, which represents over 90% of kidney cancer and is a cause for cancer related deaths in the world. Studies suggested somatic VHL mutations to be the cause for the occurrence of cancer, but with the time, more latest genomic and biological studies have detected variation in epigenetic regulatory genes and showed significant heterogeneity of the intratumor that may lead to strategies of diagnostic, predictive, and therapeutic importance. Immune dysfunction is responsible for almost all types of renal cancer, and angiogenesis and immunosuppression function together in the tumor microenvironment of renal cell carcinoma (RCC). Over the past few years, advancement in the management of the RCC has finally revolutionized with the arrival of the entrapped immune inhibitors which particularly concentrated on the receptor (programmed cell death-1) and focus on the new generation receptor i.e. TKRI (tyrosine-kinase receptor inhibitors). The present review deals with the comprehensive review of RCC and emphasizes on its types, pathogenesis and advancement in these diseases. This review also overviews the role of innate and adaptive immune response-related mechanism, the function of cancer stem cell in this diseases, therapeutic targeted drugs and hormonal signaling pathways as an emerging strategy in the management of the renal cancer.

Old Drugs with New Tricks: Efficacy of Fluoroquinolones to Suppress Replication of Flaviviruses

Repurposing FDA-approved compounds could provide the fastest route to alleviate the burden of disease caused by flaviviruses. In this study, three fluoroquinolones, enoxacin, difloxacin and ciprofloxacin, curtailed replication of flaviviruses Zika (ZIKV), dengue (DENV), Langat (LGTV) and Modoc (MODV) in HEK-293 cells at low micromolar concentrations. Time-of-addition assays suggested that enoxacin suppressed ZIKV replication at an intermediate step in the virus life cycle, whereas ciprofloxacin and difloxacin had a wider window of efficacy. A129 mice infected with 1 × 10⁵ plaque-forming units (pfu) ZIKV FSS13025 (n = 20) or phosphate buffered saline (PBS) (n = 11) on day 0 and treated with enoxacin at 10 mg/kg or 15 mg/kg or diluent orally twice daily on days 1–5 did not differ in weight change or virus titer in serum or brain. However, mice treated with enoxacin showed a significant, five-fold decrease in ZIKV titer in testes relative to controls. Mice infected with 1 × 10² pfu ZIKV (n = 13) or PBS (n = 13) on day 0 and treated with 15 mg/kg oral enoxacin or diluent twice daily pre-treatment and days 1–5 post-treatment also did not differ in weight and viral load in the serum, brain, and liver, but mice treated with enoxacin showed a significant, 2.5-fold decrease in ZIKV titer in testes relative to controls. ZIKV can be sexually transmitted, so reduction of titer in the testes by enoxacin should be further investigated.

Renal carcinoma CD105-/CD44- cells display stem-like properties in vitro and form aggressive tumors in vivo

Clear cell renal cell carcinoma (ccRCC) is the most common kidney cancer. Prognosis for ccRCC is generally poor since it is largely resistant to chemo- and radiotherapy. Many studies suggested that cancer stem cells/tumor initiating cells (CSCs/TICs) are responsible for development of tumor, disease progression, aggressiveness, metastasis and drug resistance. However, tumorigenic potential of CSCs/TICs isolated from established RCC cell lines - basic ccRCC research model - has never been investigated in vivo. CD105+, CD105-, CD44+ and CD44- as well as CD44-/CD105- CD44+/CD105+ and CD44-/CD105+ cells were isolated from Caki-1 RCC cell line, confirming coexistence of multiple subpopulations of stem-related phenotype in stable cell line. Sorted cells were injected subcutaneously into NOD SCID mice and tumor growth was monitored with MRI and PET/CT. Tumor growth was observed after implantation of CD105+, CD44+, CD44-, CD44-/CD105+ and CD44-/CD105- but not CD105- or CD44+/CD105+. Implantation of CD44-/CD105- cells induced tumors that were characterized by longer T1 and distinct metabolic pattern than other tumors. All the tumors were characterized by low uptake of [18F]FDG. CD105+ and CD44- tumors expresses Nanog and Oct-4, while CD44- tumors additionally expressed endothelial cell marker - CD31.

Different morphologies of human embryonic kidney 293T cells in various types of culture dishes

Human embryonic kidney 293T (HEK293T) cells are used in various biological experiments and researches. In this study, we investigated the effect of cell culture environments on morphological and functional properties of HEK293T cells. We used several kinds of dishes made of polystyrene or glass for cell culture, including three types of polystyrene dishes provided from different manufacturers for suspension and adherent cell culture. In addition, we also investigated the effect of culturing on gelatin-coated surfaces on the cell morphology. We found that HEK293T cells aggregated and formed into three-dimensional (3-D) multicellular spheroids (MCS) when non-coated polystyrene dishes were used for suspension culture. In particular, the non-coated polystyrene dish from Sumitomo bakelite is the most remarkable characteristic for 3-D MCS among the polystyrene dishes. On the other hand, HEK293T cells hardly aggregated and formed 3-D MCS on gelatin-coated polystyrene dishes for suspension culture. HEK293T cells adhered on the non- or gelatin-coated polystyrene dish for adherent culture, but they did not form 3-D MCS. HEK293T cells also adhered to non- or gelatin-coated glass dishes and did not form 3-D MCS in serum-free medium. These results suggest that HEK293T cells cultured on non-coated polystyrene dish may be useful for the tool to analyze the characteristics of 3D-MCS.

PDE6D Inhibitors with a New Design Principle Selectively Block K-Ras Activity

The trafficking chaperone PDE6D (also referred to as PDEδ) has been nominated as a surrogate target for K-Ras4B (hereafter K-Ras). Arl2-assisted unloading of K-Ras from PDE6D in the perinuclear area is significant for correct K-Ras localization and therefore activity. However, the unloading mechanism also leads to the undesired ejection of PDE6D inhibitors. To counteract ejection, others have recently optimized inhibitors for picomolar affinities; however, cell penetration generally seems to remain an issue. To increase resilience against ejection, we engineered a "chemical spring" into prenyl-binding pocket inhibitors of PDE6D. Furthermore, cell penetration was improved by attaching a cell-penetration group, allowing us to arrive at micromolar in cellulo potencies in the first generation. Our model compounds, Deltaflexin-1 and -2, selectively disrupt K-Ras, but not H-Ras membrane organization. This selectivity profile is reflected in the antiproliferative activity on colorectal and breast cancer cells, as well as the ability to block stemness traits of lung and breast cancer cells. While our current model compounds still have a low in vitro potency, we expect that our modular and simple inhibitor redesign could significantly advance the development of pharmacologically more potent compounds against PDE6D and related targets, such as UNC119 in the future.

Knockout of the Placenta Specific 8 Gene Affects the Proliferation and Migration of Human Embryonic Kidney 293T Cell

Candidate oncogene placenta specific 8 (PLAC8) has been identified to participate in different cellular process and human diseases. However, the effects of PLAC8 on cell proliferation and migration in human kidney cancer (KC) remained unclear. In current study, physiological effects of PLAC8 in immortalized human embryonic kidney cell line (HEK293T) were investigated in vitro. Two PLAC8 knockout (KO) cell lines were established via CRISPR/Cas9-mediated methods combined with fluorescence activated single cell sorting. To classify the characteristic of PLAC8 during cell proliferation and migration in HEK293T, cellular proliferative activity was analyzed by cell counting and colony formation assay. Cell cycle distribution was analyzed by flow cytometry. Cellular motile activity was analyzed by wound-healing and migration assay. Further underlying molecular mechanism was explored via western blot. With the KO cell lines, it was found that PLAC8 KO could decrease cell proliferation. Moreover, the inhibitory effects of PLAC8 KO on cell proliferation were associated with a G2/M arrest in cell cycle progression concomitant with a remarkable inhibition of Cyclin B1 and elevation of Cyclin A. The alteration of cell cycle proteins and E-cadherin might further associate with the enhancement of cell motility. Our study revealed a novel role for PLAC8 in cell proliferation and migration of HEK293T cells, which might shed light on further study of PLAC8 on human KC.

A robust strategy for proteomic identification of biomarkers of invasive phenotype complexed with extracellular heat shock proteins

As an extension of their orchestration of intracellular pathways, secretion of extracellular heat shock proteins (HSPs) is an emerging paradigm of homeostasis imperative to multicellular organization. Extracellular HSP is axiomatic to the survival of cells during tumorigenesis; proportional representation of specific HSP family members is indicative of invasive potential and prognosis. Further significance has been added by the knowledge that all cancer-derived exosomes have surface-exposed HSPs that reflect the membrane topology of cells that secrete them. Extracellular HSPs are also characteristic of chronic inflammation and sepsis. Accordingly, interrogation of extracellular HSPs secreted from cell culture models may represent a facile means of identifying translational biomarker signatures for targeting in situ. In the current study, we evaluated a simple peptide-based multivalent HSP affinity approach using the Vn96 peptide for low speed pelleting of HSP complexes from bioreactor cultures of cell lines with varying invasive phenotype in xenotransplant models: U87 (glioblastoma multiforme; invasive); HELA (choriocarcinoma; minimally invasive); HEK293T (virally transformed immortalized; embryonic). Proteomic profiling by bottom-up mass spectrometry revealed a comprehensive range of candidate biomarkers including primary HSP ligands. HSP complexes were associated with additional chaperones of prognostic significance such as protein disulfide isomerases, as well as pleiotropic metabolic enzymes, established as proportionally reflective of invasive phenotype. Biomarkers of inflammatory and mechanotransductive phenotype were restricted to the most invasive cell model U87, including chitinase CHI3L1, lamin C, amyloid derivatives, and histone isoforms.

Differential Requirements for the RAD51 Paralogs in Genome Repair and Maintenance in Human Cells

Deficiency in several of the classical human RAD51 paralogs [RAD51B, RAD51C, RAD51D, XRCC2 and XRCC3] is associated with cancer predisposition and Fanconi anemia. To investigate their functions, isogenic disruption mutants for each were generated in non-transformed MCF10A mammary epithelial cells and in transformed U2OS and HEK293 cells. In U2OS and HEK293 cells, viable ablated clones were readily isolated for each RAD51 paralog; in contrast, with the exception of RAD51B, RAD51 paralogs are cell-essential in MCF10A cells. Underlining their importance for genomic stability, mutant cell lines display variable growth defects, impaired sister chromatid recombination, reduced levels of stable RAD51 nuclear foci, and hyper-sensitivity to mitomycin C and olaparib, with the weakest phenotypes observed in RAD51B-deficient cells. Altogether these observations underscore the contributions of RAD51 paralogs in diverse DNA repair processes, and demonstrate essential differences in different cell types. Finally, this study will provide useful reagents to analyze patient-derived mutations and to investigate mechanisms of chemotherapeutic resistance deployed by cancers.

Metastatic renal cell carcinoma cells growing in 3D on poly‑D‑lysine or laminin present a stem‑like phenotype and drug resistance

3D spheroids are built by heterogeneous cell types in different proliferative and metabolic states and are enriched in cancer stem cells. The main aim of the study was to investigate the usefulness of a novel metastatic renal cell carcinoma (RCC) 3D spheroid culture for in vitro cancer stem cell physiology research and drug toxicity screening. RCC cell lines, Caki-1 (skin metastasis derived) and ACHN (pleural effusion derived), were efficiently cultured in growth-factor/serum deprived, defined, StemXvivo and Nutristem medium on laminin-coated or poly-D-lysine-coated plates. In optimal 3D culture conditions, ACHN cells (StemXVivo/poly-D-lysine) formed small spheroids with remaining adherent cells of an epithelial phenotype, while Caki-1 cells (StemXVivo/laminin) formed large dark spheroids with significantly reduced cell viability in the center. In the 3D structures, expression levels of genes encoding stem transcription factors (OCT4, SOX2, NES) and RCC stem cell markers (CD105, CD133) were deregulated in comparison to these expression levels in traditional 2D culture. Sunitinib, epirubicin and doxycycline were more toxic to cells cultured in monolayers than for cells in 3D spheroids. High numbers of cells arrested in the G0/G1 phase of the cell cycle were found in spheroids under sunitinib treatment. We showed that metastatic RCC 3D spheroids supported with ECM are a useful model to determine the cancer cell growth characteristics that are not found in adherent 2D cultures. Due to the more complex architecture, spheroids may mimic in vivo micrometastases and may be more appropriate to investigate novel drug candidate responses, including the direct effects of tyrosine kinase inhibitor activity against RCC cells.

Sonic hedgehog pathway mediates genistein inhibition of renal cancer stem cells

Cancer stem cells (CSCs) have been implicated in the genesis, progression and recurrence of renal cancer. The sonic hedgehog (Shh) pathway serves a critical role in maintaining the stemness of CSCs. Genistein, a major isoflavone component extracted from soybeans and soy products, has been demonstrated to possess anticancer activity. However, the effects of genistein on renal CSCs and its underlying mechanisms remain to be fully elucidated. The aim of the present study was to investigate the role of the Shh pathway in genistein inhibition of renal CSCs. The results of the present study demonstrated that expression levels of renal CSC markers were markedly upregulated in the sphere-forming cells, which were isolated and enriched from 786-O and ACHN cells in a tumor sphere formation assay, and more cells were arrested at the G₀/G₁ phase instead of the S₁ phase compared with the adherent cells. Furthermore, the present study demonstrated that genistein could effectively diminish the activity of renal CSCs by suppressing tumor sphere formation, decreasing renal CSCs markers, inhibiting proliferation and inducing apoptosis. Additionally, the downregulation of Shh pathway activity could inhibit renal CSCs. Genistein exhibited an inhibitory effect on renal CSCs by attenuating the activation of the Shh pathway. In conclusion, the results illustrated the role of the Shh pathway in regulating renal CSC traits and the intervention of renal CSCs by genistein, which could provide novel insights into the molecular mechanisms of renal CSC intervention.

Extracellular vesicles in onco-nephrology

Extracellular vesicles (EVs) are important mediators of intercellular communication in cancer and in normal tissues. EVs transfer biologically active molecules from the cell of origin to recipient cells. This review summarizes the studies on EVs derived from renal cell carcinoma and from a subpopulation of CD105-positive renal cancer stem cells. While EVs from renal cell carcinoma show mild biological activity, EVs from renal cancer stem cells enhance tumor angiogenesis and metastasis formation. The effect is probably due to the transfer of proangiogenic RNA cargo to endothelial cells, which acquire an activated angiogenic phenotype. In vivo, treatment with EVs favors the formation of a premetastatic niche in the lungs. Moreover, EVs derived from renal cancer stem cells modify gene expression in mesenchymal stromal cells, enhancing the expression of genes involved in matrix remodeling, cell migration, and tumor growth. Mesenchymal stromal cells preconditioned with tumor EVs and then coinjected in vivo with renal cancer cells support tumor growth and vessel formation. Finally, tumor EVs promote tumor immune escape by inhibiting the differentiation process of dendritic cells and the activation of T cells. Thus, tumor-derived EVs act on the microenvironment favoring tumor aggressiveness, may contribute to angiogenesis through both direct and indirect mechanisms and are involved in tumor immune escape.

Membrane-bound packages called extracellular vesicles (EVs) released by kidney cancer stem cells can make tumors more aggressive, promote the onset of cancer at other sites, and help tumors escape the anti-cancer immune response. Giovanni Camussi and colleagues at the University of Turin, Italy, review understanding of EVs from kidney cancer cells. EVs from cancer stem cells are especially effective in promoting cancer, unlike those from mature cancer cells. This is partly due to their ability to promote the formation of new blood vessels to sustain tumor growth. Some of the vesicles’ effects are mediated by transferring small molecules of ribonucleic acid (RNA) into other cells. These RNAs can regulate the activity of specific genes, promoting cancer. Studying patients’ EVs may assist cancer diagnosis and help predict the likely progression of the disease.

Error-Prone Replication through UV Lesions by DNA Polymerase θ Protects against Skin Cancers

Cancers from sun-exposed skin accumulate "driver" mutations, causally implicated in oncogenesis. Because errors incorporated during translesion synthesis (TLS) opposite UV lesions would generate these mutations, TLS mechanisms are presumed to underlie cancer development. To address the role of TLS in skin cancer formation, we determined which DNA polymerase is responsible for generating UV mutations, analyzed the relative contributions of error-free TLS by Polη and error-prone TLS by Polθ to the replication of UV-damaged DNA and to genome stability, and examined the incidence of UV-induced skin cancers in Polθ-/-, Polη-/-, and Polθ-/- Polη-/- mice. Our findings that the incidence of skin cancers rises in Polθ-/- mice and is further exacerbated in Polθ-/- Polη-/- mice compared with Polη-/- mice support the conclusion that error-prone TLS by Polθ provides a safeguard against tumorigenesis and suggest that cancer formation can ensue in the absence of somatic point mutations.

Study of Cathepsin B inhibition in VEGFR TKI treated human renal cell carcinoma xenografts

Several therapeutic options are available for metastatic RCC, but responses are almost never complete, and resistance to therapy develops in the vast majority of patients. Consequently, novel treatments are needed to combat resistance to current therapies and to improve patient outcomes. We have applied integrated transcriptome and proteome analyses to identify cathepsin B (CTSB), a cysteine proteinase of the papain family, as one of the most highly upregulated gene products in established human RCC xenograft models of resistance to vascular endothelial growth factor receptor (VEGFR) tyrosine kinase inhibitors (TKI). We used established RCC models to test the significance of CTSB in the progression of renal cancer. Our evaluation of CTSB showed that stable CTSB knockdown suppressed RCC growth in vitro and in vivo. Stable over-overexpression of wild-type CTSB (CTSB^wt/hi), but not of an CTSB active site mutant (CTSB^N298A), rescued cell growth in CTSB knockdown cells and abolished the efficacy of VEGFR TKI treatment. Genome-wide transcriptome profiling of CTSB knockdown cells demonstrated significant effects on multiple metabolic and stem cell-related pathways, with ALDHA1A (ALDH1) as one of the most significantly downregulated genes. Importantly, survival analysis across 16 major TCGA cancers revealed that CTSB overexpression is associated with low rates of three and five year patient survival rates (P = 2.5e-08, HR = 1.4). These data strongly support a contribution of CTSB activity to RCC cell growth and tumorigenicity. They further highlight the promise of CTSB inhibition in development of novel combination therapies designed to improve efficacy of current TKI treatments of metastatic RCC.

Downregulation of HSP60 disrupts mitochondrial proteostasis to promote tumorigenesis and progression in clear cell renal cell carcinoma

In the present study, we demonstrate that HSP60 is unequivocally downregulated in clear cell renal cell carcinoma (ccRCC) tissues compared to pericarcinous tissues. Overexpression of HSP60 in ccRCC cancer cells suppresses cell growth. HSP60 knockdown increases cell growth and proliferation in both cell culture and nude mice xenografts, and drives cells to undergo epithelial to mesenchymal transition (EMT). Our results propose that HSP60 silencing disrupts the integrity of the respiratory complex I and triggers the excessive ROS production, which promotes tumor progression in the following aspects: (1) ROS activates the AMPK pathway that promotes acquisition of the Warburg phenotype in HSP60-KN cells; (2) ROS generated by HSP60 knockdown or by rotenone inhibition drives cells to undergo EMT; and (3) the high level of ROS may also fragment the Fe-S clusters that up regulates ADHFe1 expression and the 2-hydroxygluterate (2-HG) production leading to changes in DNA methylation. These results suggest that the high level of ROS is needed for tumorigenesis and progression in tumors with the low HSP60 expression and HSP60 is a potential diagnostic biomarker as well as a therapeutic target in ccRCC.

Three-Dimensional Cell Culture Model Utilization in Renal Carcinoma Cancer Stem Cell Research

Specific 3D conditions of cancer cell lines have been optimized over last years, with growing significance of serum-free and xeno-free culture variants. The choice of proper culture media enables cancer stem cells proliferation in primary and stable cell lines. To obtain renal cell cancer stem-like phenotype, we employed media dedicated for mesenchymal cells and adult stem cells. Developed RCC cell line 3D culture system enables effective drug testing, including tyrosine kinase inhibitor anti-cancer cell toxicity. To induce formation of 3D spheroids by RCC cell lines, StemXvivo and NutriStem media must be used. Usage of laminin- or poly-D-lysine coated plates enhances also the formation of spheroids in 3D-promoting media. Seeding is optimal with Caki-1 or ACHN cell lines as well as 786-O or HKCSC cells. Our bio-mimic 3D RCC cell culture model promotes cell viability and stem-related gene expression including E-cadherin, N-cadherin, HIF1, HIF2, VEGF, Sox2, Pax2, and Nestin. 3D spheroid formation ability and spheroid volume increase are disturbed upon drug treatment. Untreated 3D structures reach ~100 μm in diameter at the end of 14-day long experiment. Sorter-based cell cycle analysis and Ki-67 staining should be conducted to verify specific toxicity. We suggest that due to the more complex architecture 3D RCC culture is more relevant to investigate the in vivo-like tumor drug response.

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.

Increased expression of CD44 is associated with more aggressive behavior in clear cell renal cell carcinoma

AIM

Although CD44 has been suggested as a prognostic marker in renal cell carcinoma (RCC), the prognostic significance of this marker in three main subtypes of RCC is still unclear. Thus, the present study was conducted to evaluate the expression and prognostic significance of CD44 as a cancer stem cell marker in different histological subtypes of RCC. Methodology & results: CD44 expression was evaluated in 206 well-defined renal tumor samples using immunohistochemistry on tissue microarrays. Higher CD44 expression was associated with more aggressive behavior, tumor progression and worse prognosis in clear cell RCC (ccRCC) but not in papillary and chromophobe RCC subtypes.

DISCUSSION & CONCLUSION

Cancer stem cell marker CD44 may be a promising target for cancer treatment only in ccRCC.

CBFA2T2 is associated with a cancer stem cell state in renal cell carcinoma

Background

Renal cell carcinoma (RCC) is the most common kidney cancer, accounting for approximately 80–90% of all primary kidney cancer. Treatment for patients with advanced RCC remains unsatisfactory. Rare cancer stem cells (CSCs) are proposed to be responsible for failure of current treatment.

Methods

OncoLnc was used as a tool for interactively exploring survival correlations. Gene manipulation and expression analysis were carried out using siRNA, RT-PCR and Western blotting. Wound healing and invasion assays were used for phenotypical characterization. Aldefluor assay and FACS sorting Sphere culture were used to determine the “stemness” of CSCs. Co-Immunoprecipitation (Co-IP) was used to examine the interaction between OCT4 and CBFA2T2. Student’s t-test and Chi square test was used to analyze statistical significance.

Results

CBFA2T2 expression can significantly predict the survival of RCC patients. Knocking-down of CBFA2T2 can inhibit cell migration and invasion in RCC cells in vitro, and reduce ALDH^high CSCs populations. CBFA2T2 expression is necessary for sphere-forming ability and cancer stem cells marker expression in RCC cell lines.

Conclusions

Our data suggest that CBFA2T2 expression correlates with aggressive characteristics of RCC and CBFA2T2 is required for maintenance of “stemness” through regulation of stem cells factors, thereby highlighting CBFA2T2 as a potential therapeutic target for RCC treatment.

Electronic supplementary material

The online version of this article (10.1186/s12935-017-0473-z) contains supplementary material, which is available to authorized users.

Identification of the SOX2 Interactome by BioID Reveals EP300 as a Mediator of SOX2-dependent Squamous Differentiation and Lung Squamous Cell Carcinoma Growth

Lung cancer is the leading cause of cancer mortality worldwide, with squamous cell carcinoma (SQCC) being the second most common form. SQCCs are thought to originate in bronchial basal cells through an injury response to smoking, which results in this stem cell population committing to hyperplastic squamous rather than mucinous and ciliated fates. Copy number gains in SOX2 in the region of 3q26-28 occur in 94% of SQCCs, and appear to act both early and late in disease progression by stabilizing the initial squamous injury response in stem cells and promoting growth of invasive carcinoma. Thus, anti-SOX2 targeting strategies could help treat early and/or advanced disease. Because SOX2 itself is not readily druggable, we sought to characterize SOX2 binding partners, with the hope of identifying new strategies to indirectly interfere with SOX2 activity. We now report the first use of proximity-dependent biotin labeling (BioID) to characterize the SOX2 interactome in vivo We identified 82 high confidence SOX2-interacting partners. An interaction with the coactivator EP300 was subsequently validated in both basal cells and SQCCs, and we demonstrate that EP300 is necessary for SOX2 activity in basal cells, including for induction of the squamous fate. We also report that EP300 copy number gains are common in SQCCs and that growth of lung cancer cell lines with 3q gains, including SQCC cells, is dependent on EP300. Finally, we show that EP300 inhibitors can be combined with other targeted therapeutics to achieve more effective growth suppression. Our work supports the use of BioID to identify interacting protein partners of nondruggable oncoproteins such as SOX2, as an effective strategy to discover biologically relevant, druggable targets.

Opposite feedback from mTORC1 to H-ras and K-ras4B downstream of SREBP1

As a major growth factor transducer, Ras is an upstream activator of mTORC1, which further integrates nutrient and energy inputs. To ensure a contextual coupling of cell division via Ras/MAPK-signalling and growth via mTORC1-signalling, feedback loops from one pathway back to the other are required. Here we describe a novel feedback from mTORC1, which oppositely affects oncogenic H-ras- and K-ras-signalling output, and as a consequence stemness properties of tumourigenic cells. Amino acid stimulation of mTORC1 increases the processed form of SREBP1, a major lipidome regulator. We show that modulation of the SREBP1 levels downstream of S6K1 has opposite effects on oncogenic H-ras and K-ras nanoscale membrane organisation, ensuing signalling output and promotion of mammospheres expressing these oncogenes. Our data suggest that modulation of phosphatidic acid, a major target of SREBP1 controlled lipid metabolism, is sufficient to affect H-ras and K-ras oppositely in the membrane. Thus mTORC1 activation increases H-ras-, but decreases K-ras-signalling output in cells transformed with the respective oncogene. Given the different impact of these two Ras isoforms on stemness, our results could have implications for stem cell biology and inhibition of cancer stem cells.

Global and cell-type specific properties of lincRNAs with ribosome occupancy

Advances in transcriptomics have led to the discovery of a large number of long intergenic non-coding RNAs (lincRNAs), which are now recognized as important regulators of diverse cellular processes. Although originally thought to be non-coding, recent studies have revealed that many lincRNAs are bound by ribosomes, with a few lincRNAs even having ability to generate micropeptides. The question arises: how widespread the translation of lincRNAs may be and whether such translation is likely to be functional. To better understand biological relevance of lincRNA translation, we systematically characterized lincRNAs with ribosome occupancy by the expression, structural, sequence, evolutionary and functional features for eight human cell lines, revealed that lincRNAs with ribosome occupancy have remarkably distinctive properties compared with those without ribosome occupancy, indicating that translation has important biological implication in categorizing and annotating lincRNAs. Further analysis revealed lincRNAs exhibit remarkable cell-type specificity with differential translational repertoires and substantial discordance in functionality. Collectively, our analyses provide the first attempt to characterize global and cell-type specific properties of translation of lincRNAs in human cells, highlighting that translation of lincRNAs has clear molecular, evolutionary and functional implications. This study will facilitate better understanding of the diverse functions of lincRNAs.

Rapalogs can promote cancer cell stemness in vitro in a Galectin-1 and H-ras-dependent manner

Currently several combination treatments of mTor- and Ras-pathway inhibitors are being tested in cancer therapy. While multiple feedback loops render these central signaling pathways robust, they complicate drug targeting.Here, we describe a novel H-ras specific feedback, which leads to an inadvertent rapalog induced activation of tumorigenicity in Ras transformed cells. We find that rapalogs specifically increase nanoscale clustering (nanoclustering) of oncogenic H-ras but not K-ras on the plasma membrane. This increases H-ras signaling output, promotes mammosphere numbers in a H-ras-dependent manner and tumor growth in ovo. Surprisingly, also other FKBP12 binders, but not mTor-inhibitors, robustly decrease FKBP12 levels after prolonged (>2 days) exposure. This leads to an upregulation of the nanocluster scaffold galectin-1 (Gal-1), which is responsible for the rapamycin-induced increase in H-ras nanoclustering and signaling output. We provide evidence that Gal-1 promotes stemness features in tumorigenic cells. Therefore, it may be necessary to block inadvertent induction of stemness traits in H-ras transformed cells by specific Gal-1 inhibitors that abrogate its effect on H-ras nanocluster. On a more general level, our findings may add an important mechanistic explanation to the pleiotropic physiological effects that are observed with rapalogs.

The network of DAB2IP-miR-138 in regulating drug resistance of renal cell carcinoma associated with stem-like phenotypes

Targeted therapy is a standard of care for metastatic renal cell carcinoma (RCC) but the response rate is not overwhelmed, which only prolongs a short survival of patients due to the onset of therapeutic resistance. Although the mechanisms are not fully understood, the presence of cancer initiating cells (CIC) may underlie the drug resistance. Nevertheless, identifying CIC phenotypes with its biomarkers in RCC appear to be diverse and controversial from many reports. In this study, we took a different approach to focus on the regulatory mechanism in RCC-CIC and unveil DAB2IP-mediated miR-138 expression that plays a critical role in modulating stem-like phenotypes in RCC via targeting the ABC transporter (ABCA13) as well as oncogenic histone methyltransferase EZH2 while down regulation of miR-138 gene expression in RCC is due to epigenetic gene silencing by DNA methyltransferase 1 (DNMT1). We also characterize the individual mechanism by which ABCA13 in RCC-CIC contributes to its drug resistance and. EZH2 maintain stem-like phenotypes. Noticeably, elevated expression of ABCA13 and EZH2 is correlated with overall survival of RCC patients, which can be used as potential prognostic markers. Taken together, this study demonstrates a potent and unique pathway of DAB2IP-mediated miR-138 in modulating CIC phenotypes during RCC progression and also offers a new therapeutic strategy of targeting drug resistant RCC.

Contributions of 3D Cell Cultures for Cancer Research

Cancer cell lines have contributed immensely in understanding the complex physiology of cancers. They are excellent material for studies as they offer homogenous samples without individual variations and can be utilised with ease and flexibility. Also, the number of assays and end-points one can study is almost limitless; with the advantage of improvising, modifying or altering several variables and methods. Literally, a new dimension to cancer research has been achieved by the advent of 3Dimensional (3D) cell culture techniques. This approach increased many folds the ways in which cancer cell lines can be utilised for understanding complex cancer biology. 3D cell culture techniques are now the preferred way of using cancer cell lines to bridge the gap between the 'absolute in vitro' and 'true in vivo'. The aspects of cancer biology that 3D cell culture systems have contributed include morphology, microenvironment, gene and protein expression, invasion/migration/metastasis, angiogenesis, tumour metabolism and drug discovery, testing chemotherapeutic agents, adaptive responses and cancer stem cells. We present here, a comprehensive review on the applications of 3D cell culture systems for these aspects of cancers. J. Cell. Physiol. 232: 2679-2697, 2017. © 2016 Wiley Periodicals, Inc.

Colony, hanging drop, and methylcellulose three dimensional hypoxic growth optimization of renal cell carcinoma cell lines

Renal cell carcinoma (RCC) is the most lethal of the common urologic malignancies, comprising 3% of all human neoplasms, and the incidence of kidney cancer is rising annually. We need new approaches to target tumor cells that are resistant to current therapies and that give rise to recurrence and treatment failure. In this study, we focused on low oxygen tension and three-dimensional (3D) cell culture incorporation to develop a new RCC growth model. We used the hanging drop and colony formation methods, which are common in 3D culture, as well as a unique methylcellulose (MC) method. For the experiments, we used human primary RCC cell lines, metastatic RCC cell lines, human kidney cancer stem cells, and human healthy epithelial cells. In the hanging drop assay, we verified the potential of various cell lines to create solid aggregates in hypoxic and normoxic conditions. With the semi-soft agar method, we also determined the ability of various cell lines to create colonies under different oxygen conditions. Different cell behavior observed in the MC method versus the hanging drop and colony formation assays suggests that these three assays may be useful to test various cell properties. However, MC seems to be a particularly valuable alternative for 3D cell culture, as its higher efficiency of aggregate formation and serum independency are of interest in different areas of cancer biology.

Targeting Strategies for Renal Cell Carcinoma: From Renal Cancer Cells to Renal Cancer Stem Cells

Renal cell carcinoma (RCC) is a common form of urologic tumor that originates from the highly heterogeneous epithelium of renal tubules. Over the last decade, targeting therapies to renal cancer cells have transformed clinical care for RCC. Recently, it was proposed that renal cancer stem cells (CSCs) isolated from renal carcinomas were responsible for driving tumor growth and resistance to conventional chemotherapy and radiotherapy, according to the theory of CSCs; this has provided the rationale for therapies targeting this aggressive cell population. Precise identification of renal CSC populations and the complete cell hierarchy will accurately inform characterization of disease subtypes. This will ultimately contribute to more personalized and targeted therapies. Here, we summarize potential targeting strategies for renal cancer cells and renal CSCs, including tyrosine kinase inhibitors, mammalian target of rapamycin inhibitors (mTOR), interleukins, CSC marker inhibitors, bone morphogenetic protein-2, antibody drug conjugates, and nanomedicine. In conclusion, targeting therapies for RCC represent new directions for exploration and clinical investigation and they plant a seed of hope for advanced clinical care.

The Role of Hypoxia and Cancer Stem Cells in Renal Cell Carcinoma Pathogenesis

The cancer stem cell (CSC) model has recently been approached also in renal cell carcinoma (RCC). A few populations of putative renal tumor-initiating cells (TICs) were identified, but they are indifferently understood; however, the first and most thoroughly investigated are CD105-positive CSCs. The article presents a detailed comparison of all renal CSC-like populations identified by now as well as their presumable origin. Hypoxic activation of hypoxia-inducible factors (HIFs) contributes to tumor aggressiveness by multiple molecular pathways, including the governance of immature stem cell-like phenotype and related epithelial-to-mesenchymal transition (EMT)/de-differentiation, and, as a result, poor prognosis. Due to intrinsic von Hippel-Lindau protein (pVHL) loss of function, clear-cell RCC (ccRCC) develops unique pathological intra-cellular pseudo-hypoxic phenotype with a constant HIF activation, regardless of oxygen level. Despite satisfactory evidence concerning pseudo-hypoxia importance in RCC biology, its influence on putative renal CSC-like largely remains unknown. Thus, the article discusses a current knowledge of HIF-1α/2α signaling pathways in the promotion of undifferentiated tumor phenotype in general, including some experimental findings specific for pseudo-hypoxic ccRCC, mostly dependent from HIF-2α oncogenic functions. Existing gaps in understanding both putative renal CSCs and their potential connection with hypoxia need to be filled in order to propose breakthrough strategies for RCC treatment.

Micro-vesicles derived from bone marrow stem cells protect the kidney both in vivo and in vitro by microRNA-dependent repairing

AIMS

Micro-vesicles (MVs) from bone mesenchymal stem cells (MSCs) have been shown to contribute to the recovery of damaged kidney. The aims of the present study are to investigate the biological effects and repair mechanisms of MVs.

METHODS

Micro-vesicles were obtained from MSC supernatants. In vitro, the proximal tubular epithelial cells (HK-2) were treated with transforming growth factor (TGF-β1). The expressions of E-cadherin and α-smooth muscle actin (α-SMA) were evaluated. In vitro, the mice were divided into: control, unilateral ureteral obstruction (UUO), UUO+MSC, and UUO+MV group. MVs and MSCs were injected after surgery. The mice were killed 7/14 days after surgery and handled for further tests. The micro-RNA expressions were labeled using the miRCURY Hy3/Hy5 Power labeling kit and hybridized on the miRCURY LNA Array.

RESULTS

In vitro, MV reversed transforming growth factor-β1 (TGF-β1)-induced morphological changes, and firmed the expression of E-cadherin and reduced the secretion of α-SMA in HK2 cells. In vivo, the level of blood urea nitrogen (BUN) in the MV and MSC group was lower than the UUO (P < 0.01). The Scr level decreased after 7 days of MV treatment (P < 0.05). Administration of MSC and MV reduced Scr level at day 14 (P < 0.05). The level of serum UA decreased with MV administration (day 7,14, P < 0.01). Herein, a total of 503 expressed miRNAs were detected, of which, 266 were in MSC, including 237 in MVs.

CONCLUSION

Micro-vesicles (MVs) protect kidneys both in vivo and vitro, and MVs are superior to MSCs in some respects. MVs can be a potential therapy in treatment of kidney diseases.

Renal Cancer Stem Cells: Characterization and Targeted Therapies

Renal cell carcinoma (RCC) is a major neoplasm with high incidence in western countries. Tumors are heterogeneous and are composed of differentiated cancer cells, stromal cells, and cancer stem cells (CSCs). CSCs possess two main properties: self-renewal and proliferation. Additionally, they can generate new tumors once transplanted into immunodeficient mice. Several approaches have been described to identify them, through the expression of cell markers, functional assays, or a combination of both. As CSCs are involved in the resistance mechanisms to radio- and chemotherapies, several new strategies have been proposed to directly target CSCs in RCC. One approach drives CSCs to differentiate into cancer cells sensitive to conventional treatments, while the other proposes to eradicate them selectively. A series of innovative therapies aiming at eliminating CSCs have been designed to treat other types of cancer and have not been experimented with on RCC yet, but they reveal themselves to be promising. In conclusion, CSCs are an important player in carcinogenesis and represent a valid target for therapy in RCC patients.

miR-17 inhibition enhances the formation of kidney cancer spheres with stem cell/ tumor initiating cell properties

Renal cell carcinoma (RCC) is an aggressive disease, with 35% chance of metastasis. The 'cancer stem cell' hypothesis suggests that a subset of cancer cells possess stem cell properties and is crucial in tumor initiation, metastasis and treatment resistance. We isolated RCC spheres and showed that they exhibit cancer stem cell/ tumor initiating cell-like properties including the formation of self-renewing spheres, high tumorigenicity and the ability to differentiate to cell types of the original tumor. Spheres showed increased expression of stem cell-related transcription factors and mesenchymal markers. miRNAs were differentially expressed between RCC spheres and their parental cells. Inhibition of miR-17 accelerated the formation of RCC spheres which shared molecular characteristics with the spontaneous RCC spheres. Target prediction pointed out TGFβ pathway activation as a possible mechanism to drive RCC sphere formation. We demonstrate that miR-17 overexpression interferes with the TGFβ-EMT axis and hinders RCC sphere formation; and validated TGFBR2 as a direct and biologically relevant target during this process. Thus, a single miRNA may have an impact on the formation of highly tumorigenic cancer spheres of kidney cancer.

Low concentrations of 5-aza-2'-deoxycytidine induce breast cancer stem cell differentiation by triggering tumor suppressor gene expression

Background

Breast cancer stem cells (BCSCs) are considered the cause of tumor growth, multidrug resistance, metastasis, and recurrence. Therefore, differentiation therapy to reduce self-renewal of BCSCs is a promising approach. We have examined the effects of 5-aza-2′-deoxycytidine (DAC) on BCSC differentiation.

Materials and methods

BCSCs were treated with a range of DAC concentrations from 0.625 to 100 µM. The differentiation status of DAC-treated BCSCs was graded by changes in cell proliferation, CD44⁺CD24⁻ phenotype, expression of tumor suppressor genes, including BRCA1, BRCA2, p15, p16, p53, and PTEN, and antitumor drug resistance.

Results

DAC treatment caused significant BCSC differentiation. BCSCs showed a 15%–23% reduction in proliferation capacity, 3.0%–21.3% decrease in the expression of BCSC marker CD44⁺/CD24⁻, activation of p53 expression, and increased p15, p16, BRCA1, and BRCA2 expression. Concentrations of DAC ranging from 0.625 to 40 µM efficiently induce cell cycle arrest in S-phase. ABCG2, highly expressed in BCSCs, also decreased with DAC exposure. Of particular note, drug-sensitivity of BCSCs to doxorubicin, verapamil, and tamoxifen also increased 1.5-, 2.0-, and 3.7-fold, respectively, after pretreatment with DAC.

Conclusion

DAC reduced breast cancer cell survival and induced differentiation through reexpression of tumor suppressor genes. These results indicate the potential of DAC in targeting specific chemotherapy-resistant cells within a tumor.

Current approaches in identification and isolation of human renal cell carcinoma cancer stem cells

In recent years, cancer stem cells (CSCs)/tumor initiating cells (TICs) have been identified inside different tumors. However, currently used anti-cancer therapies are mostly directed against somatic tumor cells without targeting CSCs/TICs. CSCs/TICs also gain resistance to chemotherapies/radiotherapies. For the development of efficient treatment strategies, choosing the best method for isolation and characterization of CSCs/TICs is still debated among the scientific community. In this review, we summarize recent data concerning isolation techniques for CSCs using magnetic cell sorting and flow cytometry. The review focuses on the strategies for sample preparation during flow cytometric analysis, elaborating biomarkers such as CXCR4, CD105, and CD133. In addition, functional properties characteristic of CSCs/TICs using side population selection through Hoechst 33342 dye, aldehyde dehydrogenase 1, dye-cycle violet, and rhodamine 123 are also discussed. We also include a special focus on enriching CSCs/TICs using three-dimensional cell culture models such as agarose–agarose microbeads and sphere formation.