RESUMEN
Cellular senescence of renal tubular cells is associated with chronic diseases and age-related kidney disorders. Therapies to antagonize senescence are, therefore, explored as novel approaches in nephropathy. Exosomes derived from human mesenchymal stroma-/stem-like cells (MSC) entail the transfer of multiple bioactive molecules, exhibiting profound regenerative potential in various tissues, including therapeutic effects in kidney diseases. Here, we first demonstrate that exosomes promote proliferation and reduce senescence in aged MSC cultures. For potential therapeutic perspectives in organ rejuvenation, we used MSC-derived exosomes to antagonize senescence in murine kidney primary tubular epithelial cells (PTEC). Exosome treatment efficiently reduced senescence while diminishing the transcription of senescence markers and senescence-associated secretory phenotype (SASP) factors. Concomitantly, we observed less DNA damage foci and more proliferating cells. These data provide new information regarding the therapeutic property of MSC exosomes in the development of renal senescence, suggesting a contribution to a new chapter of regenerative vehicles in senotherapy.
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Senescencia Celular , Células Epiteliales/citología , Exosomas/metabolismo , Riñón/citología , Células Madre Mesenquimatosas/citología , Animales , Células Cultivadas , Células Epiteliales/metabolismo , Exosomas/trasplante , Humanos , Riñón/metabolismo , Masculino , Células Madre Mesenquimatosas/metabolismo , Ratones Endogámicos C57BL , Fenotipo Secretor Asociado a la SenescenciaRESUMEN
BACKGROUND AIMS: Mesenchymal stroma/stem-like cells (MSCs) are a popular cell source and hold huge therapeutic promise for a broad range of possible clinical applications. However, to harness their full potential, current limitations in harvesting, expansion and characterization have to be overcome. These limitations are related to the heterogeneity of MSCs in general as well as to inconsistent experimental protocols. Here we aim to compare in vitro methods to facilitate comparison of MSCs generated from various tissues. METHODS: MSCs from 3 different tissues (bone marrow, dental pulp, adipose tissue), exemplified by cells from 3 randomly chosen donors per tissue, were systematically compared with respect to their in vitro properties after propagation in specific in-house standard media, as established in the individual laboratories, or in the same commercially available medium. RESULTS: Large differences were documented with respect to the expression of cell surface antigens, population doubling times, basal expression levels of 5 selected genes and osteogenic differentiation. The commercial medium reduced differences in these parameters with respect to individual human donors within tissue and between tissues. The extent, size and tetraspanin composition of extracellular vesicles were also affected. CONCLUSIONS: The results clearly demonstrate the extreme heterogeneity of MSCs, which confirms the problem of reproducibility of results, even when harmonizing experimental conditions, and questions the significance of common parameters for MSCs from different tissues in vitro.
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Medios de Cultivo/farmacología , Células Madre Mesenquimatosas/citología , Especificidad de Órganos , Tejido Adiposo/citología , Antígenos de Superficie/metabolismo , Biomarcadores/metabolismo , Células de la Médula Ósea/citología , Células de la Médula Ósea/efectos de los fármacos , Calcio/metabolismo , Técnicas de Cultivo de Célula , Diferenciación Celular/efectos de los fármacos , Proliferación Celular/efectos de los fármacos , Células Cultivadas , Pulpa Dental/citología , Vesículas Extracelulares/efectos de los fármacos , Vesículas Extracelulares/metabolismo , Regulación de la Expresión Génica/efectos de los fármacos , Humanos , Células Madre Mesenquimatosas/efectos de los fármacos , Especificidad de Órganos/efectos de los fármacos , Osteogénesis/efectos de los fármacos , Reproducibilidad de los Resultados , Tetraspaninas/metabolismo , Donantes de TejidosRESUMEN
Life cycle limitation hampers the production of high amounts of primary human mesenchymal stroma-/stem-like cells (MSC) and limits cell source reproducibility for clinical applications. The characterization of permanently growing MSC544 revealed some differentiation capacity and the simultaneous presence of known MSC markers CD73, CD90, and CD105 even after continuous long-term culture for more than one year and 32 passages. The expression of CD13, CD29, CD44, and CD166 were identified as further surface proteins, all of which were also simultaneously detectable in various other types of primary MSC populations derived from the umbilical cord, bone marrow, and placenta suggesting MSC-like properties in the cell line. Proliferating steady state MSC544 exhibited immune-modulatory activity similar to a subpopulation of long-term growth-inhibited MSC544 after 189d of continuous culture in confluency. This confluent connective cell layer with fibroblast-like morphology can spontaneously contract and the generated space is subsequently occupied by new cells with regained proliferative capacity. Accordingly, the confluent and senescence-associated beta-galactosidase-positive MSC544 culture with about 95% G0/G1 growth-arrest resumed re-entry into the proliferative cell cycle within 3d after sub-confluent culture. The MSC544 cells remained viable during confluency and throughout this transition which was accompanied by marked changes in the release of proteins. Thus, expression of proliferation-associated genes was down-modulated in confluent MSC544 and re-expressed following sub-confluent conditions whilst telomerase (hTERT) transcripts remained detectable at similar levels in both, confluent growth-arrested and proliferating MSC544. Together with the capability of connective cell layer formation for potential therapeutic approaches, MSC544 provide a long term reproducible human cell source with constant properties.
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Células Madre Mesenquimatosas/citología , Antígenos CD/metabolismo , Técnicas de Cultivo de Célula/métodos , Ciclo Celular , Diferenciación Celular , Línea Celular , Proliferación Celular , Expresión Génica , Humanos , Células Madre Mesenquimatosas/inmunología , Células Madre Mesenquimatosas/metabolismo , ProteómicaRESUMEN
Various direct and indirect cellular interactions between multi-functional mesenchymal stroma/stem-like cells (MSCs) and cancer cells contribute to increasing plasticity within the tumor tissue and its microenvironment. Direct and tight communication between MSC and cancer cells is based on membrane protein interactions and the exchange of large plasma membrane fragments also known as trogocytosis. An ultimate but rare direct interaction resumes in fusion of these two cellular partners resulting in the formation of new cancer hybrid cell populations. Alternatively, indirect interactions are displayed by the release of membranous vesicle-encapsulated microRNAs and proteins or soluble components such as molecular growth factors, hormones, chemo-/cytokines, and metabolites. Released single molecules as well as multivesicular bodies including exosomes and microvesicles can form local concentration gradients within the tumor microenvironment and are incorporated not only by adjacent neighboring cells but also affect distant target cells. The present Review will focus on vesicle-mediated indirect communication and on cancer cell fusion with direct contact between MSC and cancer cells. These different types of interaction are accompanied by functional interference and mutual acquisition of new cellular properties. Consequently, alterations in cancer cell functionalities paralleled by the capability to reorganize the tumor stroma can trigger changes in metastatic behavior and promote retrodifferentiation to develop new cancer stem-like cells. However, exosomes and microvesicles acting over long distances may also provide a tool with therapeutic potential when loaded with anti-tumor cargo. Stem Cells 2018;36:951-968.
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Células Madre Mesenquimatosas/metabolismo , Células Madre Neoplásicas/metabolismo , Línea Celular Tumoral , HumanosRESUMEN
Formation of hybrid cells by "accidental cell fusion" of normal and neoplastic breast epithelial cells with local tissue-associated mesenchymal stroma/stem-like cells (MSC) in an inflammatory microenvironment can generate new cancer cell populations whereby molecular signaling mechanisms of this process remain unclear. Fusions of lentiviral enhanced green fluorescent protein-labeled MSC with mcherry-labeled breast epithelial cells were quantified and effects of tumor necrosis factor alpha (TNF-α) and receptor downstream signaling were investigated. Cocultures of MSC with normal human mammary epithelial cells, with neoplastic MCF10A, or with MDA-MB-231 or MCF7 breast cancer cells demonstrated hybrid cell formation between 0.1% and about 2% of the populations within 72 hours, whereby the fusion process occurred in less than 5 minutes. Addition of the pro-inflammatory cytokine TNF-α significantly enhanced MCF10A-MSC cell fusion. Small-interfering RNA (siRNA) knockdown experiments revealed an involvement of tumor necrosis factor (TNF) receptor-1 and -2 in this process. This was also substantiated by siRNA knockdown of tumor necrosis factor receptor type 1-associated death domain which abolished TNF-α-stimulated fusion. While TNF receptor signaling can be relayed via the Mitogen-activated protein kinase 8 (MAPK8), NF-κB or cell death pathways, examination of further downstream signaling exhibited little if any effects of MAPK8 or RelA (p65) on TNF-α-mediated cell fusion, respectively. These data suggested that cell fusion between MSC and MCF10A breast epithelial cells can be stimulated by TNF-α involving TNF receptor-activated cell death pathways or additional NF-κB signaling. Stem Cells 2018;36:977-989.
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Neoplasias de la Mama/genética , Células Epiteliales/metabolismo , Células Madre Mesenquimatosas/metabolismo , Receptores Tipo I de Factores de Necrosis Tumoral/metabolismo , Neoplasias de la Mama/metabolismo , Neoplasias de la Mama/patología , Femenino , Humanos , Receptores Tipo I de Factores de Necrosis Tumoral/genética , Transducción de Señal , Transfección , Microambiente TumoralRESUMEN
Cell fusion as a rare event was observed following the co-culture of human MDA-MB-231cherry breast cancer cells or benign neoplastic MCF10Acherry breast epithelial cells together with different mesenchymal stroma/stem-like cells (MSCGFP) cultures, respectively, resulting in the generation of double-fluorescing hybrid cells. Analysis of potential molecular mechanisms for the formation of cancer hybrid cells revealed cytoskeletal components, including F-actin. Thus, a sub-lethal concentration of cytochalasin D, which blocks elongation of actin filaments, was able to significantly reduce cancer hybrid cell formation. Simultaneously, cell cycle progression of the different co-cultures remained unaffected following treatment with cytochalasin D, indicating continued proliferation. Moreover, exposure to 50 nM cytochalasin D revealed little if any effect on the expression of various integrins and cell adhesion molecules in the different co-cultures. However, LC-MS proteome analysis of the different control co-cultures compared to corresponding cytochalasin-treated co-cultures demonstrated predominant differences in the expression of actin-associated cytoskeletal proteins. In addition, the requirement of structured actin to provide an appropriate cytoskeletal network for enabling subsequent fusion processes was also substantiated by the actin filament disrupting latrunculin B, which inhibits the fusion process between the breast cancer populations and mesenchymal stroma/stem-like cells (MSC). Together, these findings suggest an important role of distinct actin structures and associated cytoskeletal components during cell fusion and the formation of breast cancer hybrid cells.
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Citoesqueleto de Actina/metabolismo , Neoplasias de la Mama/patología , Células Madre Mesenquimatosas/patología , Citoesqueleto de Actina/efectos de los fármacos , Compuestos Bicíclicos Heterocíclicos con Puentes/farmacología , Ciclo Celular/efectos de los fármacos , Fusión Celular , Línea Celular Tumoral , Técnicas de Cocultivo , Citocalasina D/farmacología , Femenino , Humanos , Células Híbridas/efectos de los fármacos , Células Madre Mesenquimatosas/efectos de los fármacos , Polimerizacion , Tiazolidinas/farmacología , Tionas/farmacología , Uracilo/análogos & derivados , Uracilo/farmacologíaRESUMEN
The interactions of cancer cells with neighboring non-malignant cells in the microenvironment play an important role for progressive neoplastic development and metastasis. Long-term direct co-culture of human MDA-MB-231cherry breast cancer cells with benign human mesenchymal stroma/stem-like cells (MSC) MSC544GFP stably expressing mCherry and eGFP fluorescence proteins, respectively, was associated with the formation of three-dimensional (3D) tumor spheroids in vitro. The quantification of the breast tumor marker urokinase plasminogen activator (uPA) in mono-cultured MDA-MB-231 cells revealed an approximately 14-fold enhanced expression when compared to five different normal human MSC mono-cultures. Moreover, uPA levels in 3D tumor spheroids remained elevated 9.4-fold above the average of five different human MSC cultures. In contrast, the expression of the corresponding plasminogen activator inhibitor type-1 (PAI-1) declined by 2.6-fold in the breast cancer cells and was even further reduced by 3.2-fold in the MDA-MB-231cherry/MSC544GFP 3D co-culture spheroids when compared to the various MSC populations. The supportive data were obtained for the production of TGF-ß1, which is an important growth factor in the regulation of tumor growth and metastasis formation. Whereas, TGF-ß1 release in MDA-MB-231cherry/MSC544GFP co-cultures was elevated by 1.56-fold as compared to MSC544 mono-cultures after 24 h; this ratio further increased to 2.19-fold after 72 h. Quantitative PCR analyses in MSC544 and MDA-MB-231 cells revealed that MSC, rather than the breast cancer cells, are responsible for TGF-ß1 synthesis and that TGF-ß1 contributes to its own synthesis in these cells. These findings suggested potential synergistic effects in the expression/secretion of uPA, PAI-1, and TGF-ß during the co-culture of breast cancer cells with MSC.
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Neoplasias de la Mama/metabolismo , Células Madre Mesenquimatosas/metabolismo , Inhibidor 1 de Activador Plasminogénico/metabolismo , Activadores Plasminogénicos/metabolismo , Factor de Crecimiento Transformador beta/metabolismo , Comunicación Celular , Línea Celular Tumoral , Femenino , Humanos , Inhibidor 1 de Activador Plasminogénico/genética , Activadores Plasminogénicos/genética , Esferoides Celulares/metabolismo , Células Tumorales CultivadasRESUMEN
The tumor microenvironment enables important cellular interactions between cancer cells and recruited adjacent populations including mesenchymal stroma/stem cells (MSC). In vivo cellular interactions of primary human MSC in co-culture with human SK-OV-3 ovarian cancer cells revealed an increased tumor growth as compared to mono-cultures of the ovarian cancer cells. Moreover, the presence of MSC stimulated formation of liver metastases. Further interactions of MSC with the ovarian cancer cells resulted in the formation of hybrid cells by cell fusion. Isolation and single cell cloning of these hybrid cells revealed two differentially fused ovarian cancer cell populations termed SK-hyb1 and SK-hyb2. RNA microarray analysis demonstrated expression profiles from both parental partners whereby SK-hyb1 were attributed with more SK-OV-3 like properties and SK-hyb2 cells displayed more similarities to MSC. Both ovarian cancer hybrid populations exhibited reduced proliferative capacity compared to the parental SK-OV-3 cells. Moreover, the fused populations failed to develop tumors in NODscid mice. Together, these data suggested certain stimulatory effects on ovarian tumor growth in the presence of MSC. Conversely, fusion of MSC with SK-OV-3 cells contributed to the generation of new cancer hybrid populations displaying a significantly reduced tumorigenicity.
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Carcinogénesis , Comunicación Celular , Células Madre Mesenquimatosas/citología , Neoplasias Ováricas/patología , Línea Celular Tumoral , Proliferación Celular , Técnicas de Cocultivo , Femenino , HumanosRESUMEN
BACKGROUND: Fusion of breast cancer cells with tumor-associated populations of the microenvironment including mesenchymal stroma/stem-like cells (MSC) represents a rare event in cell communication whereby the metastatic capacity of those hybrid cells remains unclear. METHODS: Functional changes were investigated in vitro and in vivo following spontaneous fusion and hybrid cell formation between primary human MSC and human MDA-MB-231 breast cancer cells. Thus, lentiviral eGFP-labeled MSC and breast cancer cells labeled with mcherry resulted in dual-fluorescing hybrid cells after co-culture. RESULTS: Double FACS sorting and single cell cloning revealed two different aneuploid male hybrid populations (MDA-hyb1 and MDA-hyb2) with different STR profiles, pronounced telomerase activities, and enhanced proliferative capacities as compared to the parental cells. Microarray-based mRNA profiling demonstrated marked regulation of genes involved in epithelial-mesenchymal transition and increased expression of metastasis-associated genes including S100A4. In vivo studies following subcutaneous injection of the breast cancer and the two hybrid populations substantiated the in vitro findings by a significantly elevated tumor growth of the hybrid cells. Moreover, both hybrid populations developed various distant organ metastases in a much shorter period of time than the parental breast cancer cells. CONCLUSION: Together, these data demonstrate spontaneous development of new tumor cell populations exhibiting different parental properties after close interaction and subsequent fusion of MSC with breast cancer cells. This formation of tumor hybrids contributes to continuously increasing tumor heterogeneity and elevated metastatic capacities.
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Transformación Celular Neoplásica , Células Madre Mesenquimatosas/metabolismo , Animales , Antineoplásicos Fitogénicos/uso terapéutico , Neoplasias de la Mama/tratamiento farmacológico , Neoplasias de la Mama/metabolismo , Neoplasias de la Mama/patología , Línea Celular Tumoral , Técnicas de Cocultivo , Transición Epitelial-Mesenquimal/genética , Femenino , Humanos , Células Madre Mesenquimatosas/citología , Ratones , Ratones Endogámicos NOD , Ratones SCID , Invasividad Neoplásica/genética , Interferencia de ARN , ARN Interferente Pequeño/metabolismo , Proteína de Unión al Calcio S100A4/antagonistas & inhibidores , Proteína de Unión al Calcio S100A4/genética , Proteína de Unión al Calcio S100A4/metabolismo , Telomerasa/metabolismoRESUMEN
BACKGROUND: The initiation and progression of malignant tumors is driven by distinct subsets of tumor-initiating or cancer stem-like cells (CSCs) which develop therapy/apoptosis resistance and self-renewal capacity. In order to be able to eradicate these CSCs with novel classes of anti-cancer therapeutics, a better understanding of their biology and clinically-relevant traits is mandatory. MAIN BODY: Several requirements and functions of a CSC niche physiology are combined with current concepts for CSC generation such as development in a hierarchical tumor model, by stochastic processes, or via a retrodifferentiation program. Moreover, progressive adaptation of endothelial cells and recruited immune and stromal cells to the tumor site substantially contribute to generate a tumor growth-permissive environment resembling a CSC niche. Particular emphasis is put on the pivotal role of multipotent mesenchymal stroma/stem cells (MSCs) in supporting CSC development by various kinds of interaction and cell fusion to form hybrid tumor cells. CONCLUSION: A better knowledge of CSC niche physiology may increase the chances that cancer stemness-depleting interventions ultimately result in arrest of tumor growth and metastasis.
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Comunicación Celular , Células Madre Mesenquimatosas/metabolismo , Modelos Biológicos , Células Madre Neoplásicas/metabolismo , Nicho de Células Madre , Animales , Autofagia , Diferenciación Celular , Autorrenovación de las Células , Metabolismo Energético , Humanos , Hipoxia/metabolismo , Células Madre Mesenquimatosas/citologíaRESUMEN
This article focusses on the role of TGF-ß and its signaling crosstalk with the RHO family GTPases RAC1 and RAC1b in the progression of breast and pancreatic carcinoma. The aggressive nature of these tumor types is mainly due to metastatic dissemination. Metastasis is facilitated by desmoplasia, a peculiar tumor microenvironment and the ability of the tumor cells to undergo epithelial-mesenchymal transition (EMT) and to adopt a motile and invasive phenotype. These processes are controlled entirely or in part by TGF-ß and the small RHO GTPase RAC1 with both proteins acting as tumor promoters in late-stage cancers. Data from our and other studies point to signaling crosstalk between TGF-ß and RAC1 and the related isoform, RAC1b, in pancreatic and mammary carcinoma cells. Based on the exciting observation that RAC1b functions as an endogenous inhibitor of RAC1, we propose a model on how the relative abundance or activity of RAC1 and RAC1b in the tumor cells may determine their responses to TGF-ß and, ultimately, the metastatic capacity of the tumor.
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Neoplasias de la Mama/patología , Neoplasias Pancreáticas/patología , Transducción de Señal , Factor de Crecimiento Transformador beta/metabolismo , Proteína de Unión al GTP rac1/metabolismo , Animales , Humanos , Neoplasias Pancreáticas/metabolismoRESUMEN
Despite improvements in diagnosis and treatment, breast cancer is still the most common cancer type among non-smoking females. TGF-ß can inhibit breast cancer development by inducing cell cycle arrest in both, cancer cells and, as part of a senescence program in normal human mammary epithelial cells (HMEC). Moreover, TGF-ß also drives cell migration and invasion, in part through the small GTPases Rac1 and Rac1b. Depletion of Rac1b or Rac1 and Rac1b in MDA-MB-231 or MDA-MB-435s breast cancer cells by RNA interference enhanced or suppressed, respectively, TGF-ß1-induced migration/invasion. Rac1b depletion in MDA-MB-231 cells also increased TGF-ß-induced p21WAF1 expression and ERK1/2 phosphorylation. Senescent HMEC (P15/P16), when compared to their non-senescent counterparts (P11/P12), presented with dramatically increased migratory activity. These effects were paralleled by elevated expression of genes associated with TGF-ß signaling and metastasis, downregulated Rac1b, and upregulated Rac1. Our data suggest that acquisition of a motile phenotype in HMEC resulted from enhanced autocrine TGF-ß signaling, invasion/metastasis-associated gene expression, and a shift in the ratio of antimigratory Rac1b to promigratory Rac1. We conclude that although enhanced TGF-ß signaling is considered antioncogenic in HMEC by suppressing oncogene-induced transformation, this occurs at the expense of a higher migration and invasion potential.
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Neoplasias de la Mama/metabolismo , Células Epiteliales/metabolismo , Factor de Crecimiento Transformador beta/metabolismo , Proteína de Unión al GTP rac1/metabolismo , Neoplasias de la Mama/genética , Neoplasias de la Mama/patología , Línea Celular Tumoral , Movimiento Celular/genética , Senescencia Celular/genética , Inhibidor p21 de las Quinasas Dependientes de la Ciclina/genética , Inhibidor p21 de las Quinasas Dependientes de la Ciclina/metabolismo , Células Epiteliales/patología , Femenino , Expresión Génica , Humanos , Proteína Quinasa 1 Activada por Mitógenos/metabolismo , Proteína Quinasa 3 Activada por Mitógenos/metabolismo , Metástasis de la Neoplasia , Fenotipo , Fosforilación , Unión Proteica , Proteína de Unión al GTP rac1/química , Proteína de Unión al GTP rac1/genéticaRESUMEN
In recent years, the neuroprotective potential of mesenchymal stroma-/stem-like cells (MSC) as well as of MSC-derived extracellular vesicles (EVs) like exosomes has been intensively explored. This included preclinical evaluation regarding treatment of neurodegenerative disorders such as the fatal motor neuron disease amyotrophic Lateral Sclerosis (ALS). Several studies have reported that MSC-derived exosomes can stimulate tissue regeneration and reduce inflammation. MSC release EVs and trophic factors and thereby modify cell-to-cell communication. These cell-free products may protect degenerating motor neurons (MNs) and represent a potential therapeutic approach for ALS. In the present study we investigated the effects of exosomes derived from a permanently growing MSC line on both, wild type and ALS (SOD1G93A transgenic) primary motor neurons. Following application in a normal and stressed environment we could demonstrate beneficial effects of MSC exosomes on neurite growth and morphology indicating the potential for further preclinical evaluation and clinical therapeutic development. Investigation of gene expression profiles detected transcripts of several antioxidant and anti-inflammatory genes in MSC exosomes. Characterization of their microRNA (miRNA) content revealed miRNAs capable of regulating antioxidant and anti-apoptotic pathways.
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Esclerosis Amiotrófica Lateral , Exosomas , Células Madre Mesenquimatosas , Ratones , Humanos , Animales , Esclerosis Amiotrófica Lateral/metabolismo , Exosomas/metabolismo , Antioxidantes/farmacología , Neuronas Motoras/metabolismo , Células Madre Mesenquimatosas/metabolismoRESUMEN
Fusion of cancer cells either with other cancer cells (homotypic fusion) in local vicinity of the tumor tissue or with other cell types (e.g., macrophages, cancer-associated fibroblasts (CAFs), mesenchymal stromal-/stem-like cells (MSC)) (heterotypic fusion) represents a rare event. Accordingly, the clinical relevance of cancer-cell fusion events appears questionable. However, enhanced tumor growth and/or development of certain metastases can originate from cancer-cell fusion. Formation of hybrid cells after cancer-cell fusion requires a post-hybrid selection process (PHSP) to cope with genomic instability of the parental nuclei and reorganize survival and metabolic functionality. The present review dissects mechanisms that contribute to a PHSP and resulting functional alterations of the cancer hybrids. Based upon new properties of cancer hybrid cells, the arising clinical consequences of the subsequent tumor heterogeneity after cancer-cell fusion represent a major therapeutic challenge. However, cellular partners during cancer-cell fusion such as MSC within the tumor microenvironment or MSC-derived exosomes may provide a suitable vehicle to specifically address and deliver anti-tumor cargo to cancer cells.
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The generation of cancer hybrid cells by intra-tumoral cell fusion opens new avenues for tumor plasticity to develop cancer stem cells with altered properties, to escape from immune surveillance, to change metastatic behavior, and to broaden drug responsiveness/resistance. Genomic instability and chromosomal rearrangements in bi- or multinucleated aneuploid cancer hybrid cells contribute to these new functions. However, the significance of cell fusion in tumorigenesis is controversial with respect to the low frequency of cancer cell fusion events and a clonal advantage of surviving cancer hybrid cells following a post-hybrid selection process. This review highlights alternative processes of cancer hybrid cell development such as entosis, emperipolesis, cannibalism, therapy-induced polyploidization/endoreduplication, horizontal or lateral gene transfer, and focusses on the predominant mechanisms of cell fusion. Based upon new properties of cancer hybrid cells the arising clinical consequences of the subsequent tumor heterogeneity after cancer cell fusion represent a major therapeutic challenge.
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Exosomes derived from mesenchymal stroma-/stem-like cells (MSCs) as part of extracellular vesicles are considered cell-free biocompatible nanovesicles that promote repair activities of damaged tissues or organs by exhibiting low immunogenic and cytotoxic effects. Contributions to regenerative activities include wound healing, maintenance of stem cell niches, beneficial regenerative effects in various diseases, and reduction of senescence. However, the mode of action in MSC-derived exosomes strongly depends on the biological content like different regulatory microRNAs that are determined by the tissue origin of MSCs. In tumors, MSCs use indirect and direct pathways in a communication network to interact with cancer cells. This leads to mutual functional changes with the acquisition of an aberrant tumor-associated MSC phenotype accompanied by altered cargo in the exosomes. Consequently, MSC-derived exosomes either from normal tissue-originating MSCs or from aberrant tumor-associated MSCs can confer different actions on tumor development. These processes exhibiting tumor-inhibitory and tumor-supportive effects with a focus on exosome microRNA content will be discriminated and discussed within this review.
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Breast cancer is the most prevalent malignancy amongst women worldwide while ovarian cancer represents the leading cause of death among gynecological malignancies. Women suffering from these cancers displayed heightened rates of major depressive disorder, and antidepressant treatment with selective serotonin reuptake inhibitors (SSRIs) is frequently recommended. Recently, narrative reviews and meta-analyses showed increased recurrence risks and mortality rates in SSRI-treated women with breast and ovarian cancer. We therefore examined whether three commonly prescribed SSRIs, fluoxetine, sertraline and citalopram, affect proliferation or glucose uptake of human breast and ovarian cancer cell lines characterized by different malignancies and metastatic potential. SSRI treatment or serotonin stimulation with therapeutically relevant concentrations over various time periods revealed no consistent dose- or time-dependent effect on proliferation rates. A marginal, but significant increase in glucose uptake was observed in SK-OV-3 ovarian cancer cells upon fluoxetine or sertraline, but not citalopram treatment. In three breast cancer cell lines and in two additional ovarian cancer cell lines no significant effect of SSRIs on glucose uptake was observed. Our data suggest that the observed increase in recurrence- and mortality rates in SSRI-treated cancer patients is unlikely to be linked to antidepressant therapies.
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Neoplasias de la Mama/metabolismo , Proliferación Celular/efectos de los fármacos , Glucosa/metabolismo , Neoplasias Ováricas/metabolismo , Inhibidores Selectivos de la Recaptación de Serotonina/farmacología , Neoplasias de la Mama/mortalidad , Neoplasias de la Mama/patología , Femenino , Humanos , Células MCF-7 , Neoplasias Ováricas/mortalidad , Neoplasias Ováricas/patologíaRESUMEN
Tumor heterogeneity is considered the major cause of treatment failure in current cancer therapies. This feature of solid tumors is not only the result of clonal outgrowth of cells with genetic mutations, but also of epigenetic alterations induced by physical and chemical signals from the tumor microenvironment (TME). Besides fibroblasts, endothelial and immune cells, mesenchymal stroma/stem-like cells (MSCs) and tumor-associated macrophages (TAMs) intimately crosstalk with cancer cells and can exhibit both anti- and pro-tumorigenic effects. MSCs can alter cancer cellular phenotypes to increase cancer cell plasticity, eventually resulting in the generation of cancer stem cells (CSCs). The shift between different phenotypic states (phenotype switching) of CSCs is controlled via both genetic programs, such as epithelial-mesenchymal transdifferentiation or retrodifferentiation, and epigenetic alterations triggered by signals from the TME, like hypoxia, spatial heterogeneity or stromal cell-derived chemokines. Finally, we highlight the role of spontaneous cancer cell fusion with various types of stromal cells. i.e., MSCs in shaping CSC plasticity. A better understanding of cell plasticity and phenotype shifting in CSCs is a prerequisite for exploiting this phenomenon to reduce tumor heterogeneity, thereby improving the chance for therapy success.
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Intratumoral heterogeneity is considered the major cause of drug unresponsiveness in cancer and accumulating evidence implicates non-mutational resistance mechanisms rather than genetic mutations in its development. These non-mutational processes are largely driven by phenotypic plasticity, which is defined as the ability of a cell to reprogram and change its identity (phenotype switching). Tumor cell plasticity is characterized by the reactivation of developmental programs that are closely correlated with the acquisition of cancer stem cell properties and an enhanced potential for retrodifferentiation or transdifferentiation. A well-studied mechanism of phenotypic plasticity is the epithelial-mesenchymal transition (EMT). Current evidence suggests a complex interplay between EMT, genetic and epigenetic alterations, and clues from the tumor microenvironment in cell reprogramming. A deeper understanding of the connections between stem cell, epithelial-mesenchymal, and tumor-associated reprogramming events is crucial to develop novel therapies that mitigate cell plasticity and minimize the evolution of tumor heterogeneity, and hence drug resistance. Alternatively, vulnerabilities exposed by tumor cells when residing in a plastic or stem-like state may be exploited therapeutically, i.e., by converting them into less aggressive or even postmitotic cells. Tumor cell plasticity thus presents a new paradigm for understanding a cancer's resistance to therapy and deciphering its underlying mechanisms.
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Cellular communication within the tumor microenvironment enables important interactions between cancer cells and recruited adjacent populations including mesenchymal stroma/stem-like cells (MSC). These interactions were monitored in vivo following co-injection of GFP-labeled human MSC together with mcherry-labeled MDA-MB-231 breast cancer cells in NODscid mice. Within 14 days of tumor development the number of initially co-injected MSC had significantly declined and spontaneous formation of breast cancer/MSC hybrid cells was observed by the appearance of double fluorescing cells. This in vivo fusion displayed a rare event and occurred in less than 0.5% of the tumor cell population. Similar findings were observed in a parallel in vitro co-culture. Characterization of the new cell fusion products obtained after two consecutive flow cytometry cell sorting and single cell cloning revealed two populations, termed MDA-hyb3 and MDA-hyb4. The breast cancer fusion cells expressed both, GFP and mcherry and displayed more characteristics of the MDA-MB-231 cells than of the parental MSC. While little if any differences were determined in the proliferative capacity, a significant delay of MDA-hyb3 cells in tumor formation was observed when compared to the parental MDA-MB-231 cells. Moreover, MDA-hyb3 cells developed an altered pattern of distant organ metastases. These findings demonstrated dynamic tumor changes by in vivo and in vitro fusion with the development of new breast cancer hybrid cells carrying altered tumorigenic properties. Consequently, cancer cell fusion contributes to progressively increasing tumor heterogeneity which complicates a therapeutic regimen.