Renal Cancer Stem Cells: Characterization and Targeted Therapies

Insights into Personalized Care Strategies for Wilms Tumor: A Narrative Literature Review

Wilms tumor (WT), or nephroblastoma, is the predominant renal malignancy in the pediatric population. This narrative review explores the evolution of personalized care strategies for WT, synthesizing critical developments in molecular diagnostics and treatment approaches to enhance patient-specific outcomes. We surveyed recent literature from the last five years, focusing on high-impact research across major databases such as PubMed, Scopus, and Web of Science. Diagnostic advancements, including liquid biopsies and diffusion-weighted MRI, have improved early detection precision. The prognostic significance of genetic markers, particularly WT1 mutations and miRNA profiles, is discussed. Novel predictive tools integrating genetic and clinical data to anticipate disease trajectory and therapy response are explored. Progressive treatment strategies, particularly immunotherapy and targeted agents such as HIF-2α inhibitors and GD2-targeted immunotherapy, are highlighted for their role in personalized treatment protocols, especially for refractory or recurrent WT. This review underscores the necessity for personalized management supported by genetic insights, with improved survival rates for localized disease exceeding 90%. However, knowledge gaps persist in therapies for high-risk patients and strategies to reduce long-term treatment-related morbidity. In conclusion, this narrative review highlights the need for ongoing research, particularly on the long-term outcomes of emerging therapies and integrating multi-omic data to inform clinical decision-making, paving the way for more individualized treatment pathways.

Lysine-specific methyltransferase Set7/9 in stemness, differentiation, and development

The enzymes performing protein post-translational modifications (PTMs) form a critical post-translational regulatory circuitry that orchestrates literally all cellular processes in the organism. In particular, the balance between cellular stemness and differentiation is crucial for the development of multicellular organisms. Importantly, the fine-tuning of this balance on the genetic level is largely mediated by specific PTMs of histones including lysine methylation. Lysine methylation is carried out by special enzymes (lysine methyltransferases) that transfer the methyl group from S-adenosyl-L-methionine to the lysine residues of protein substrates. Set7/9 is one of the exemplary protein methyltransferases that however, has not been fully studied yet. It was originally discovered as histone H3 lysine 4-specific methyltransferase, which later was shown to methylate a number of non-histone proteins that are crucial regulators of stemness and differentiation, including p53, pRb, YAP, DNMT1, SOX2, FOXO3, and others. In this review we summarize the information available to date on the role of Set7/9 in cellular differentiation and tissue development during embryogenesis and in adult organisms. Finally, we highlight and discuss the role of Set7/9 in pathological processes associated with aberrant cellular differentiation and self-renewal, including the formation of cancer stem cells.

Sirtuins Affect Cancer Stem Cells via Epigenetic Regulation of Autophagy

Sirtuins (SIRTs) are stress-responsive proteins that regulate several post-translational modifications, partly by acetylation, deacetylation, and affecting DNA methylation. As a result, they significantly regulate several cellular processes. In essence, they prolong lifespan and control the occurrence of spontaneous tumor growth. Members of the SIRT family have the ability to govern embryonic, hematopoietic, and other adult stem cells in certain tissues and cell types in distinct ways. Likewise, they can have both pro-tumor and anti-tumor effects on cancer stem cells, contingent upon the specific tissue from which they originate. The impact of autophagy on cancer stem cells, which varies depending on the specific circumstances, is a very intricate phenomenon that has significant significance for clinical and therapeutic purposes. SIRTs exert an impact on the autophagy process, whereas autophagy reciprocally affects the activity of certain SIRTs. The mechanism behind this connection in cancer stem cells remains poorly understood. This review presents the latest findings that position SIRTs at the point where cancer cells and autophagy interact. Our objective is to highlight the various roles of distinct SIRTs in cancer stem cell-related functions through autophagy. This would demonstrate their significance in the genesis and recurrence of cancer and offer a more precise understanding of their treatment possibilities in relation to autophagy.

Exploring the dynamic interplay between cancer stem cells and the tumor microenvironment: implications for novel therapeutic strategies

Cancer stem cells (CSCs) have emerged as key contributors to tumor initiation, growth, and metastasis. In addition, CSCs play a significant role in inducing immune evasion, thereby compromising the effectiveness of cancer treatments. The reciprocal communication between CSCs and the tumor microenvironment (TME) is observed, with the TME providing a supportive niche for CSC survival and self-renewal, while CSCs, in turn, influence the polarization and persistence of the TME, promoting an immunosuppressive state. Consequently, these interactions hinder the efficacy of current cancer therapies, necessitating the exploration of novel therapeutic approaches to modulate the TME and target CSCs. In this review, we highlight the intricate strategies employed by CSCs to evade immune surveillance and develop resistance to therapies. Furthermore, we examine the dynamic interplay between CSCs and the TME, shedding light on how this interaction impacts cancer progression. Moreover, we provide an overview of advanced therapeutic strategies that specifically target CSCs and the TME, which hold promise for future clinical and translational studies in cancer treatment.

A phase I study of autologous mesenchymal stromal cells for severe steroid-dependent nephrotic syndrome

BACKGROUNDSevere forms of idiopathic nephrotic syndrome (INS) require prolonged immunosuppressive therapies and repeated courses of high-dose glucocorticoids. Mesenchymal stromal cells (MSCs) have promising immunomodulatory properties that may be employed therapeutically to reduce patient exposure to medications and their side effects.METHODSWe performed a phase I open-label trial assessing safety and feasibility of autologous bone marrow-derived MSCs (BM-MSCs) in children and young adults with severe forms of steroid-dependent nephrotic syndrome. Following autologous BM-MSC preparation and infusion, oral immunosuppression was tapered. Safety, efficacy, and immunomodulatory effects in vivo were monitored for 12 months.RESULTSSixteen patients (10 children, 6 adults) were treated. Adverse events were limited and not related to BM-MSC infusions. All patients relapsed during follow-up, but in the 10 treated children, time to first relapse was delayed (P = 0.02) and number of relapses was reduced (P = 0.002) after BM-MSC infusion, compared with the previous 12 months. Cumulative prednisone dose was also reduced at 12 months compared with baseline (P < 0.05). No treatment benefit was observed in adults.In children, despite tapering of immunosuppression, clinical benefit was mirrored by a significant reduction in total CD19+, mature, and memory B cells and an increase in regulatory T cells in vivo up to 3-6 months following BM-MSC infusionCONCLUSIONTreatment with autologous BM-MSCs is feasible and safely reduces relapses and immunosuppression at 12 months in children with severe steroid-dependent INS. Immunomodulatory studies suggest that repeating MSC infusions at 3-6 months may sustain benefit.TRIAL REGISTRATIONEudraCT 2016-004804-77.FUNDINGAIFA Ricerca Indipendente 2016-02364623.

Cancer Stem Cells in Renal Cell Carcinoma: Origins and Biomarkers

The term "cancer stem cell" (CSC) refers to a cancer cell with the following features: clonogenic ability, the expression of stem cell markers, differentiation into cells of different lineages, growth in nonadhesive spheroids, and the in vivo ability to generate serially transplantable tumors that reflect the heterogeneity of primary cancers (tumorigenicity). According to this model, CSCs may arise from normal stem cells, progenitor cells, and/or differentiated cells because of striking genetic/epigenetic mutations or from the fusion of tissue-specific stem cells with circulating bone marrow stem cells (BMSCs). CSCs use signaling pathways similar to those controlling cell fate during early embryogenesis (Notch, Wnt, Hedgehog, bone morphogenetic proteins (BMPs), fibroblast growth factors, leukemia inhibitory factor, and transforming growth factor-β). Recent studies identified a subpopulation of CD133+/CD24+ cells from ccRCC specimens that displayed self-renewal ability and clonogenic multipotency. The development of agents targeting CSC signaling-specific pathways and not only surface proteins may ultimately become of utmost importance for patients with RCC.

Targeting DRD2 by the antipsychotic drug, penfluridol, retards growth of renal cell carcinoma via inducing stemness inhibition and autophagy-mediated apoptosis

Renal cell carcinoma (RCC) is one of the most lethal genitourinary malignancies with poor prognoses, since it is largely resistant to chemotherapy, radiotherapy, and targeted therapy. The persistence of cancer stem cells (CSCs) is the major cause of treatment failure with RCC. Recent evidence showed that dopamine receptor D2 (DRD2)-targeting antipsychotic drugs such as penfluridol exert oncostatic effects on several cancer types, but the effect of penfluridol on RCC remains unknown. Here, we uncovered penfluridol suppressed in vitro cell growth and in vivo tumorigenicity of various RCC cell lines (Caki-1, 786-O, A498, and ACHN) and enhanced the Sutent (sunitinib)-triggered growth inhibition on clear cell (cc)RCC cell lines. Mechanistically, upregulation of endoplasmic reticulum (ER) stress-induced unfolded protein response (UPR) was critical for autophagy-mediated apoptosis induced by penfluridol. Transcriptional inhibition of OCT4 and Nanog via inhibiting GLI1 was important for penfluridol-induced stemness and proliferation inhibition. The anticancer activities of penfluridol on ccRCC partially occurred through DRD2. In clinical ccRCC specimens, positive correlations of DRD2 with GLI1, OCT4, and Nanog were observed and their expressions were correlated with worse prognoses. Summarizing, DRD2 antagonists such as penfluridol induce UPR signaling and suppress the GLI1/OCT4/Nanog axis in ccRCC cells to reduce their growth through inducing autophagy-mediated apoptosis and stemness inhibition. These drugs can be repurposed as potential agents to treat ccRCC patients.

Synthetic lethality of cyclin-dependent kinase inhibitor Dinaciclib with VHL-deficiency allows for selective targeting of clear cell renal cell carcinoma

Clear cell renal cell carcinoma (CC-RCC) remains one of the most deadly forms of kidney cancer despite recent advancements in targeted therapeutics, including tyrosine kinase and immune checkpoint inhibitors. Unfortunately, these therapies have not been able to show better than a 16% complete response rate. In this study we evaluated a cyclin-dependent kinase inhibitor, Dinaciclib, as a potential new targeted therapeutic for CC-RCC. In vitro, Dinaciclib showed anti-proliferative and pro-apoptotic effects on CC-RCC cell lines in Cell Titer Glo, Crystal Violet, FACS-based cell cycle analysis, and TUNEL assays. Additionally, these responses were accompanied by a reduction in phospho-Rb and pro-survival MCL-1 cell signaling responses, as well as the induction of caspase 3 and PARP cleavage. In vivo, Dinaciclib efficiently inhibited primary tumor growth in an orthotopic, patient-derived xenograft-based CC-RCC mouse model. Importantly, Dinaciclib targeted both CD105⁺ cancer stem cells (CSCs) and CD105⁻ non-CSCs in vivo. Moreover, normal cell lines, as well as a CC-RCC cell line with re-expressed von-Hippel Lindau (VHL) tumor suppressor gene, were protected from Dinaciclib-induced cytotoxicity when not actively dividing, indicating an effective therapeutic window due to synthetic lethality of Dinaciclib treatment with VHL loss. Thus, Dinaciclib represents a novel potential therapeutic for CC-RCC.

Doxycycline sensitizes renal cell carcinoma to chemotherapy by preferentially inhibiting mitochondrial translation

Objectives

The anti-cancer activity of doxycycline has been reported in many cancers but not renal cell carcinoma (RCC). This study aimed to determine the efficacy of doxycycline alone and in combination with paclitaxel and analyze the underlying mechanism in RCC.

Methods

Proliferation, colony formation and apoptosis assays were performed in RCC cell lines after drug treatments. An RCC xenograft mouse model was generated, and tumor growth was monitored. Mechanistic studies focused on mitochondrial translation and functions.

Results

Doxycycline at clinically achievable concentrations inhibited proliferation and colony formation and induced apoptosis in RCC cell lines. In normal kidney cells, doxycycline at the same concentrations either had no effect or was less effective. The combination index value demonstrated that doxycycline and paclitaxel were synergistic in vitro. Consistently, this combination therapy was significantly more effective than the monotherapy in RCC xenograft mice without causing significant toxicity. Mechanistic studies revealed that doxycycline acts on RCC cells via preferentially inhibiting mitochondrial DNA translation, thereby disrupting multiple mitochondrial complexes and impairing mitochondrial respiration.

Conclusions

Doxycycline is a useful addition to the treatment strategy for RCC. Our work also highlights the therapeutic value of mitochondrial translation inhibition in sensitizing RCC to chemotherapy.

From kidney injury to kidney cancer

Epidemiologic studies document strong associations between acute or chronic kidney injury and kidney tumors. However, whether these associations are linked by causation, and in which direction, is unclear. Accumulating data from basic and clinical research now shed light on this issue and prompt us to propose a new pathophysiological concept with immanent implications in the management of patients with kidney disease and patients with kidney tumors. As a central paradigm, this review proposes the mechanisms of kidney damage and repair that are active during acute kidney injury but also during persistent injuries in chronic kidney disease as triggers of DNA damage, promoting the expansion of (pre-)malignant cell clones. As renal progenitors have been identified by different studies as the cell of origin for several benign and malignant kidney tumors, we discuss how the different types of kidney tumors relate to renal progenitors at specific sites of injury and to germline or somatic mutations in distinct signaling pathways. We explain how known risk factors for kidney cancer rather represent risk factors for kidney injury as an upstream cause of cancer. Finally, we propose a new role for nephrologists in kidney cancer (i.e., the primary and secondary prevention and treatment of kidney injury to reduce incidence, prevalence, and recurrence of kidney cancer).

Current understanding of epigenetics mechanism as a novel target in reducing cancer stem cells resistance

At present, after extensive studies in the field of cancer, cancer stem cells (CSCs) have been proposed as a major factor in tumor initiation, progression, metastasis, and recurrence. CSCs are a subpopulation of bulk tumors, with stem cell-like properties and tumorigenic capabilities, having the abilities of self-renewal and differentiation, thereby being able to generate heterogeneous lineages of cancer cells and lead to resistance toward anti-tumor treatments. Highly resistant to conventional chemo- and radiotherapy, CSCs have heterogeneity and can migrate to different organs and metastasize. Recent studies have demonstrated that the population of CSCs and the progression of cancer are increased by the deregulation of different epigenetic pathways having effects on gene expression patterns and key pathways connected with cell proliferation and survival. Further, epigenetic modifications (DNA methylation, histone modifications, and RNA methylations) have been revealed to be key drivers in the formation and maintenance of CSCs. Hence, identifying CSCs and targeting epigenetic pathways therein can offer new insights into the treatment of cancer. In the present review, recent studies are addressed in terms of the characteristics of CSCs, the resistance thereof, and the factors influencing the development thereof, with an emphasis on different types of epigenetic changes in genes and main signaling pathways involved therein. Finally, targeted therapy for CSCs by epigenetic drugs is referred to, which is a new approach in overcoming resistance and recurrence of cancer.

Expression of Components of the Renin-Angiotensin System by Cancer Stem Cells in Renal Clear Cell Carcinoma

This study investigated the expression of components of the renin-angiotensin system (RAS) by cancer stem cells (CSCs) we have recently demonstrated in renal clear cell carcinoma (RCCC). Fifteen RCCC tissue samples underwent immunohistochemical staining for components of the RAS: renin, pro-renin receptor (PRR), angiotensin-converting enzyme (ACE), angiotensin-converting enzyme 2 (ACE2), and angiotensin II receptor 2 (AT2R). Immunofluorescence co-staining or double immunohistochemical staining of these components of the RAS with stemness-associated markers OCT4 or KLF4 was performed on two of the samples. Protein and transcript expression of these components of the RAS in six RCCC tissue samples was investigated using western blotting and reverse transcription quantitative polymerase chain reaction (RT-qPCR), respectively. In addition, angiotensin II receptor 1 (AT1R) was investigated using RT-qPCR only. Immunohistochemical staining demonstrated expression of renin, PRR, and ACE2 in 11, 13, and 13 out of 15 RCCC samples, respectively, while AT2R was expressed in all 15 samples. ACE was detected in the endothelium of normal vasculature only. Double immunohistochemical staining demonstrated localization of ACE2, but not renin, to the KLF4+ CSCs. Immunofluorescence staining showed localization of PRR and AT2R to the OCT4+ CSCs. Western blotting confirmed protein expression of all components of the RAS except renin. RT-qPCR demonstrated transcript expression of all components of the RAS including AT1R, but not AT2R, in all six RCCC tissue samples. This study demonstrated expression of PRR, ACE2, and AT2R by the CSCs within RCCC. Further studies may lead to novel therapeutic targeting of CSCs by manipulation of the RAS in the treatment of this aggressive cancer.

Targeted Delivery of Therapeutics to Urological Cancer Stem Cells

Urological cancer refers to cancer in organs of the urinary system and the male reproductive system. It mainly includes prostate cancer, bladder cancer, renal cancer, etc., seriously threatening patients' survival. Although there are many advances in the treatment of urological cancer, approved targeted therapies often result in tumor recurrence and therapy failure. An increasing amount of evidence indicated that cancer stem cells (CSCs) with tumor-initiating ability were the source of treatment failure in urological cancer. The development of CSCstargeted strategy can provide a possibility for the complete elimination of urological cancer. This review is based on a search of PubMed, Google scholar and NIH database (http://ClinicalTrials.gov/) for English language articles containing the terms: "biomarkers", "cancer stem cells", "targeting/targeted therapy", "prostate cancer", bladder cancer" and "kidney cancer". We summarized the biomarkers and stem cell features of the prostate, bladder and renal CSCs, outlined the targeted strategies for urological CSCs from signaling pathways, cytokines, angiogenesis, surface markers, elimination therapy, differentiation therapy, immunotherapy, microRNA, nanomedicine, etc., and highlighted the prospects and future challenges in this research field.

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.

Advances in Therapeutic Targeting of Cancer Stem Cells within the Tumor Microenvironment: An Updated Review

Despite great strides being achieved in improving cancer patients' outcomes through better therapies and combinatorial treatment, several hurdles still remain due to therapy resistance, cancer recurrence and metastasis. Drug resistance culminating in relapse continues to be associated with fatal disease. The cancer stem cell theory posits that tumors are driven by specialized cancer cells called cancer stem cells (CSCs). CSCs are a subpopulation of cancer cells known to be resistant to therapy and cause metastasis. Whilst the debate on whether CSCs are the origins of the primary tumor rages on, CSCs have been further characterized in many cancers with data illustrating that CSCs display great abilities to self-renew, resist therapies due to enhanced epithelial to mesenchymal (EMT) properties, enhanced expression of ATP-binding cassette (ABC) membrane transporters, activation of several survival signaling pathways and increased immune evasion as well as DNA repair mechanisms. CSCs also display great heterogeneity with the consequential lack of specific CSC markers presenting a great challenge to their targeting. In this updated review we revisit CSCs within the tumor microenvironment (TME) and present novel treatment strategies targeting CSCs. These promising strategies include targeting CSCs-specific properties using small molecule inhibitors, immunotherapy, microRNA mediated inhibitors, epigenetic methods as well as targeting CSC niche-microenvironmental factors and differentiation. Lastly, we present recent clinical trials undertaken to try to turn the tide against cancer by targeting CSC-associated drug resistance and metastasis.

Cancer Stem Cell Plasticity - A Deadly Deal

Intratumoral heterogeneity is a major ongoing challenge in the effective therapeutic targeting of cancer. Accumulating evidence suggests that a fraction of cells within a tumor termed Cancer Stem Cells (CSCs) are primarily responsible for this diversity resulting in therapeutic resistance and metastasis. Adding to this complexity, recent studies have shown that there can be different subpopulations of CSCs with varying biochemical and biophysical traits resulting in varied dissemination and drug-resistance potential. Moreover, cancer cells can exhibit a high level of plasticity or the ability to dynamically switch between CSC and non-CSC states or among different subsets of CSCs. In addition, CSCs also display extensive metabolic plasticity. The molecular mechanisms underlying these different interconnected axes of plasticity has been under extensive investigation and the trans-differentiation process of Epithelial to Mesenchymal transition (EMT) has been identified as a major contributing factor. Besides genetic and epigenetic factors, CSC plasticity is also shaped by non-cell-autonomous effects such as the tumor microenvironment (TME). In this review, we discuss the latest developments in decoding mechanisms and implications of CSC plasticity in tumor progression at biochemical and biophysical levels, and the latest in silico approaches being taken for characterizing cancer cell plasticity. These efforts can help improve existing therapeutic approaches by taking into consideration the contribution of cellular plasticity/heterogeneity in enabling drug resistance.

The Tumor Suppressor Roles of MYBBP1A, a Major Contributor to Metabolism Plasticity and Stemness

The MYB binding protein 1A (MYBBP1A, also known as p160) acts as a co-repressor of multiple transcription factors involved in many physiological processes. Therefore, MYBBP1A acts as a tumor suppressor in multiple aspects related to cell physiology, most of them very relevant for tumorigenesis. We explored the different roles of MYBBP1A in different aspects of cancer, such as mitosis, cellular senescence, epigenetic regulation, cell cycle, metabolism plasticity and stemness. We especially reviewed the relationships between MYBBP1A, the inhibitory role it plays by binding and inactivating c-MYB and its regulation of PGC-1α, leading to an increase in the stemness and the tumor stem cell population. In addition, MYBBP1A causes the activation of PGC-1α directly and indirectly through c-MYB, inducing the metabolic change from glycolysis to oxidative phosphorylation (OXPHOS). Therefore, the combination of these two effects caused by the decreased expression of MYBBP1A provides a selective advantage to tumor cells. Interestingly, this only occurs in cells lacking pVHL. Finally, the loss of MYBBP1A occurs in 8%–9% of renal tumors. tumors, and this subpopulation could be studied as a possible target of therapies using inhibitors of mitochondrial respiration.

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.

Loss of MYBBP1A Induces Cancer Stem Cell Activity in Renal Cancer

Tumors are cellular ecosystems where different populations and subpopulations of cells coexist. Among these cells, cancer stem cells (CSCs) are considered to be the origin of the tumor mass, being involved in metastasis and in the resistance to conventional therapies. Furthermore, tumor cells have an enormous plasticity and a phenomenon of de-differentiation of mature tumor cells to CSCs may occur. Therefore, it is essential to identify genetic alterations that cause the de-differentiation of mature tumor cells to CSCs for the future design of therapeutic strategies. In this study, we characterized the role of MYBBP1A by experiments in cell lines, xenografts and human tumor samples. We have found that MYBBP1A downregulation increases c-MYB (Avian myeloblastosis viral oncogene homolog) activity, leading to a rise in the stem-like cell population. We identified that the downregulation of MYBBP1A increases tumorigenic properties, in vitro and in vivo, in renal carcinoma cell lines that express high levels of c-MYB exclusively. Moreover, in a cohort of renal tumors, MYBBP1A is downregulated or lost in a significant percentage of tumors correlating with poor patient prognosis and a metastatic tendency. Our data support the role of MYBBP1A as a tumor suppressor by repressing c-MYB, acting as an important regulator of the plasticity of tumor cells.

Effect of Everolimus on Heterogenous Renal Cancer Cells Populations Including Renal Cancer Stem Cells

The aim of this study was to compare effect of everolimus on growth of different renal cell carcinoma (RCC) populations and develop experimental design to measure the early response of everolimus in clear cell RCC (ccRCC) cell lines including renal cancer stem cells. Effect of everolimus on RCC cell lines which include primary (786-0) and metastatic (ACHN) RCC cell lines as well as heterogenous populations of tumor cells of different histological RCC subtypes (clear cell RCC and papillary RCC) was measured when treated with everolimus in the range of 1-9 µM. Gene expression profiling using microarray was performed to determine the early response to everolimus in ccRCC cell lines after optimizing concentration of drug. Gene Set Enrichment Analysis (GSEA) was done which mainly focused on basic genes related to mTOR, hormonal and metabolic pathways. Everolimus acts on RCC cells in a dose-dependent manner. In all examined cell lines IC50 dose was possible to calculate after the third day of treatment. In ccRCC lines (parental and stem cell) everolimus changes expression of mTOR complexes elements and elements of related pathways when treated with optimized doses of drug. Characteristic expression profile for ccRCC cells at an early exposure time to everolimus is to elucidate. Wevarie include some basic observations derived from data analysis in the context of mechanism of action of drug with a view to better understand biology of renal cancer cells.

Dissecting LncRNA Roles in Renal Cell Carcinoma Metastasis and Characterizing Genomic Heterogeneity by Single-Cell RNA-seq

Long noncoding RNAs (lncRNA) have recently emerged as important regulators in cancer cell proliferation and metastasis. However, the role of lncRNAs in metastatic clear cell renal cell carcinoma (ccRCC) remains unclear. Here, single-cell RNA sequencing data were analyzed from primary renal cell carcinoma and paired metastatic renal cell carcinoma specimens, and characterized the expression profiles of over 10,000 genes, including 1,874 lncRNAs. Further analysis revealed that lncRNAs exhibit cancer type- and tissue-specific expression across ccRCC cells. Interestingly, a number of lncRNAs (n = 173) associated with ccRCC metastasis, termed ccRCC metastasis-associated lncRNAs (CMAL). Moreover, functional analysis based on a CMAL-PCG coexpression network revealed that CMALs contribute to cell adhesion, immune response, and cell proliferation. In combination with survival analysis, 12 CMALs were identified that participate in TNF and hypoxia-inducible factor 1 signaling to promote ccRCC metastasis. Further investigation on intratumoral heterogeneity showed that some CMALs are selectively expressed in different subpopulations. IMPLICATIONS: To explore ccRCC metastasis, the current study performed a global dissection of lncRNAs and a complex genomic analysis of ccRCC tumor heterogeneity. The data shed light on the discovery of potential lncRNA biomarkers and lncRNA therapeutic targets.

Ecto-5'-nucleotidase (CD73) is a biomarker for clear cell renal carcinoma stem-like cells

Identification of a specific biomarker for cancer stem cells (CSCs) is of potential applications in the development of effective therapeutic strategies for renal cell carcinoma (RCC). In this study, both the RCC cell line 786-O and surgically removed clear cell RCC (ccRCC) tissues were implemented to grew as spheroids in serum-free medium supplemented with mitogens. This subpopulation possessed key characteristics defining CSCs. We also identified that surgically removed ccRCC tissues were heterogenic and there was a subpopulation of cells that was highly stained with rhodamine-123. Based on membrane-proteomic analyses, CD73 was identified as a candidate biomarker. We further found that CD73high cells were highly tumorigenic. As few as 100 CD73high cells were capable of forming xenograft tumors in non obese diabetic/severe combined immunodeficiency disease mice, whereas 1 × 105 CD73low cells did not initiate tumor formation. During successive culture, the CD73high population regenerated both CD73high and CD73low cells, whereas the CD73low population remained low expression level of CD73. Furthermore, the CD73high cells were more resistant to radiation and DNA-damaging agents than the CD73low cells, and expressed a panel of 'stemness' genes at a higher level than the CD73low cells. These findings suggest that a high level of CD73 expression is a bona fide biomarker of ccRCC stem-like cells. Future research will aim at the elucidation of the underlying mechanisms of CD73 in RCC development and the distinct aspects of ccRCC stem-like cells from other tumor types.

Pharmacological targets of breast cancer stem cells: a review

Breast cancers contain small population of tumor-initiating cells called breast cancer stem cells (BCSCs), which are spared even after chemotherapy. Recently, BCSCs are implicated to be a cause of metastasis, tumor relapse, and therapy resistance in breast cancer. BCSCs have unique molecular mechanisms, which can be targeted to eliminate them. These include surface biomarkers, proteins involved in self-renewal pathways, drug efflux transporters, apoptotic/antiapoptotic proteins, autophagy, metabolism, and microenvironment regulation. The complex molecular mechanisms behind the survival of BCSCs and pharmacological targets for elimination of BCSCs are described in this review.

Cellular stress induces cancer stem-like cells through expression of DNAJB8 by activation of heat shock factor 1

In a previous study, we found that DNAJB8, a heat shock protein (HSP) 40 family member is expressed in kidney cancer stem‐like cells (CSC)/cancer‐initiating cells (CIC) and that it has a role in the maintenance of kidney CSC/CIC. Heat shock factor (HSF) 1 is a key transcription factor for responses to stress including heat shock, and it induces HSP family expression through activation by phosphorylation. In the present study, we therefore examined whether heat shock (HS) induces CSC/CIC. We treated the human kidney cancer cell line ACHN with HS, and found that HS increased side population (SP) cells. Western blot analysis and qRT‐PCR showed that HS increased the expression of DNAJB8 and SOX2. Gene knockdown experiments using siRNAs showed that the increase in SOX2 expression and SP cell ratio depends on DNAJB8 and that the increase in DNAJB8 and SOX2 depend on HSF1. Furthermore, treatment with a mammalian target of rapamycin (mTOR) inhibitor, temsirolimus, decreased the expression of DNAJB8 and SOX2 and the ratio of SP cells. Taken together, the results indicate that heat shock induces DNAJB8 by activation of HSF1 and induces cancer stem‐like cells.

Decreased TGFBR3/betaglycan expression enhances the metastatic abilities of renal cell carcinoma cells through TGF-β-dependent and -independent mechanisms

TGF-β regulates both the tumor-forming and migratory abilities of various types of cancer cells. However, it is unclear how the loss of TGF-β signaling components affects these abilities in clear-cell renal cell carcinoma (ccRCC). In this study, we investigated the role of TGFBR3 (TGF-β type III receptor, also known as betaglycan) in ccRCC. Database analysis revealed decreased expression of TGFBR3 in ccRCC tissues, which correlated with poor prognosis in patients. Orthotopic inoculation experiments using immunocompromised mice indicated that low TGFBR3 expression in ccRCC cells enhanced primary tumor formation and lung metastasis. In the presence of TGFBR3, TGF-β2 decreased the aldehyde dehydrogenase (ALDH)-positive ccRCC cell population, in which renal cancer-initiating cells are enriched. Loss of TGFBR3 also enhanced cell migration in cell culture and induced expression of several mesenchymal markers in a TGF-β-independent manner. Increased lamellipodium formation by FAK-PI3K signaling was observed with TGFBR3 downregulation, and this contributed to TGF-β-independent cell migration in ccRCC cells. Taken together, our findings reveal that loss of TGFBR3 endows ccRCC cells with multiple metastatic abilities through TGF-β-dependent and independent pathways.

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.

LncRNAs and their role in cancer stem cells

Cancer stem cells (CSCs) play a vital role in the formation of tumors and have been studied as a target of anticancer therapy. Long non-coding RNAs (lncRNAs) are important in the genesis and progression of cancer. Various lncRNAs, such as ROR, HOTAIR, H19, UCA1, and ARSR, are involved in cancer stemness. These lncRNAs could regulate the expression of CSC-related transcriptional factors, such as SOX2, OCT4, and NANOG, in colorectal, prostate, bladder, breast, liver, and other cancer types. In this work, we review the progress of lncRNAs and cancer stem cells and discuss the potential signal pathways of lncRNAs in cancer stemness.

Mechanistic Insight and Management of Diabetic Nephropathy: Recent Progress and Future Perspective

Diabetic nephropathy (DN) is the most serious microvascular complication of diabetes and the largest single cause of end-stage renal disease (ESRD) in many developed countries. DN is also associated with an increased cardiovascular mortality. It occurs as a result of interaction between both genetic and environmental factors. Hyperglycemia, hypertension, and genetic predisposition are the major risk factors. However, the exact mechanisms of DN are unclear. Despite the benefits derived from strict control of glucose and blood pressure, as well as inhibition of renin-angiotensin-aldosterone system, many patients continue to enter into ESRD. Thus, there is urgent need for improving mechanistic understanding of DN and then developing new and effective therapeutic approaches to delay the progression of DN. This review focuses on recent progress and future perspective about mechanistic insight and management of DN. Some preclinical relevant studies are highlighted and new perspectives of traditional Chinese medicine (TCM) for delaying DN progression are discussed in detail. These findings strengthen the therapeutic rationale for TCM in the treatment of DN and also provide new insights into the development of novel drugs for the prevention of DN. However, feasibility and safety of these therapeutic approaches and the clinical applicability of TCM in human DN need to be further investigated.