Inhibition of tumor formation and redirected differentiation of glioblastoma cells in a xenotypic embryonic environment

Life Entrapped in a Network of Atavistic Attractors: How to Find a Rescue

In view of unified cell bioenergetics, cell bioenergetic problems related to cell overenergization can cause excessive disturbances in current cell fate and, as a result, lead to a change of cell-fate. At the onset of the problem, cell overenergization of multicellular organisms (especially overenergization of mitochondria) is solved inter alia by activation and then stimulation of the reversible Crabtree effect by cells. Unfortunately, this apparently good solution can also lead to a much bigger problem when, despite the activation of the Crabtree effect, cell overenergization persists for a long time. In such a case, cancer transformation, along with the Warburg effect, may occur to further reduce or stop the charging of mitochondria by high-energy molecules. Understanding the phenomena of cancer transformation and cancer development has become a real challenge for humanity. To date, many models have been developed to understand cancer-related mechanisms. Nowadays, combining all these models into one coherent universal model of cancer transformation and development can be considered a new challenge. In this light, the aim of this article is to present such a potentially universal model supported by a proposed new model of cellular functionality evolution. The methods of fighting cancer resulting from unified cell bioenergetics and the two presented models are also considered.

Active Fraction from Embryo Fish Extracts Induces Reversion of the Malignant Invasive Phenotype in Breast Cancer through Down-regulation of TCTP and Modulation of E-cadherin/β-catenin Pathway

Some yet unidentified factors released by both oocyte and embryonic microenvironments demonstrated to be non-permissive for tumor development and display the remarkable ability to foster cell/tissue reprogramming, thus ultimately reversing the malignant phenotype. In the present study we observed how molecular factors extracted from Zebrafish embryos during specific developmental phases (20 somites) significantly antagonize proliferation of breast cancer cells, while reversing a number of prominent aspects of malignancy. Embryo extracts reduce cell proliferation, enhance apoptosis, and dramatically inhibit both invasiveness and migrating capabilities of cancer cells. Counteracting the invasive phenotype is a relevant issue in controlling tumor spreading and metastasis. Moreover, such effect is not limited to cancerous cells as embryo extracts were also effective in inhibiting migration and invasiveness displayed by normal breast cells undergoing epithelial-mesenchymal transition upon TGF-β1 stimulation. The reversion program involves the modulation of E-cadherin/β-catenin pathway, cytoskeleton remodeling with dramatic reduction in vinculin, as well as downregulation of TCTP and the concomitant increase in p53 levels. Our findings highlight that-contrary to the prevailing current "dogma", which posits that neoplastic cells are irreversibly "committed"-the malignant phenotype can ultimately be "reversed", at least partially, in response to environmental morphogenetic influences.

Patterns of Invasive Growth in Malignant Gliomas-The Hippocampus Emerges as an Invasion-Spared Brain Region

BACKGROUND: Widespread infiltration of tumor cells into surrounding brain parenchyma is a hallmark of malignant gliomas, but little data exist on the overall invasion pattern of tumor cells throughout the brain. METHODS: We have studied the invasive phenotype of malignant gliomas in two invasive mouse models and patients. Tumor invasion patterns were characterized in a patient-derived xenograft mouse model using brain-wide histological analysis and magnetic resonance (MR) imaging. Findings were histologically validated in a cdkn2a−/− PDGF-β lentivirus-induced mouse glioblastoma model. Clinical verification of the results was obtained by analysis of MR images of malignant gliomas. RESULTS: Histological analysis using human-specific cellular markers revealed invasive tumors with a non-radial invasion pattern. Tumors cells accumulated in structures located far from the transplant site, such as the optic white matter and pons, whereas certain adjacent regions were spared. As such, the hippocampus was remarkably free of infiltrating tumor cells despite the extensive invasion of surrounding regions. Similarly, MR images of xenografted mouse brains displayed tumors with bihemispheric pathology, while the hippocampi appeared relatively normal. In patients, most malignant temporal lobe gliomas were located lateral to the collateral sulcus. Despite widespread pathological fluid-attenuated inversion recovery signal in the temporal lobe, 74% of the “lateral tumors” did not show signs of involvement of the amygdalo-hippocampal complex. CONCLUSIONS: Our data provide clear evidence for a compartmental pattern of invasive growth in malignant gliomas. The observed invasion patterns suggest the presence of preferred migratory paths, as well as intra-parenchymal boundaries that may be difficult for glioma cells to traverse supporting the notion of compartmental growth. In both mice and human patients, the hippocampus appears to be a brain region that is less prone to tumor invasion.

Reprogramming Malignant Cancer Cells toward a Benign Phenotype following Exposure to Human Embryonic Stem Cell Microenvironment

The embryonic microenvironment is well known to be non-permissive for tumor development because early developmental signals naturally suppress the expression of proto-oncogenes. In an analogous manner, mimicking an early embryonic environment during embryonic stem cell culture has been shown to suppress oncogenic phenotypes of cancer cells. Exosomes derived from human embryonic stem cells harbor substances that mirror the content of the cells of origin and have been reported to reprogram hematopoietic stem/progenitor cells via horizontal transfer of mRNA and proteins. However, the possibility that these embryonic stem cells-derived exosomes might be the main effectors of the anti-tumor effect mediated by the embryonic stem cells has not been explored yet. The present study aims to investigate whether exosomes derived from human embryonic stem cells can reprogram malignant cancer cells to a benign stage and reduce their tumorigenicity. We show that the embryonic stem cell-conditioned medium contains factors that inhibit cancer cell growth and tumorigenicity in vitro and in vivo. Moreover, we demonstrate that exosomes derived from human embryonic stem cells display anti-proliferation and pro-apoptotic effects, and decrease tumor size in a xenograft model. These exosomes are also able to transfer their cargo into target cancer cells, inducing a dose-dependent increase in SOX2, OCT4 and Nanog proteins, leading to a dose-dependent decrease of cancer cell growth and tumorigenicity. This study shows for the first time that human embryonic stem cell-derived exosomes play an important role in the tumor suppressive activity displayed by human embryonic stem cells.

Time-lapse phenotyping of invasive glioma cells ex vivo reveals subtype-specific movement patterns guided by tumor core signaling

The biology of glioblastoma invasion and its mechanisms are poorly understood. We demonstrate using time-lapse microscopy that grafting of glioblastoma (GBM) tumorspheres into rodent brain slices results in experimental ex vivo tumors with invasive properties that recapitulate the invasion observed after orthotopic transplantation into the rodent brain. The migratory movements and mitotic patterns were clearly modified by signals extrinsic to the invading cells. The cells migrated away from the tumorspheres, and removal of the spheres reduced the directed invasive movement. The cell cultures contained different populations of invasive cells that had distinct morphology and invasive behavior patterns. Grafts of the most invasive GBM culture contained 91±8% cells with an invasive phenotype, characterized by small soma with a distinct leading process. Conversely, the majority of cells in less invasive GBM grafts were phenotypically heterogeneous: only 6.3±4.1% of the cells had the invasive phenotype. Grafts of highly and moderately invasive cultures had different proportions of cells that advanced into the brain slice parenchyma during the observation period: 89.2±2.2% and 23.1±6.8%, respectively. In grafts with moderately invasive properties, most of the cells (76.8±6.8%) invading the surrounding brain tissue returned to the tumor bulk or stopped centrifugal migration. Our data suggest that the invasion of individual GBM tumors can be conditioned by the prevalence of a cell fraction with particular invasive morphology and by signaling between the tumor core and invasive cells. These findings can be important for the development of new therapeutic strategies that target the invasive GBM cells.

Developmental Stage-Specific Embryonic Induction of HepG2 Cell Differentiation

BACKGROUND

Although hepatocellular carcinoma cells can sometimes undergo differentiation in an embryonic microenvironment, the mechanism is poorly understood.

AIM

The developmental stage-specific embryonic induction of tumor cell differentiation was investigated.

METHODS

Both chick and mouse liver extracts and hepatoblast-enriched cells at different developmental stages were used to treat human hepatoma HepG2 cells, and the effects on the induction of differentiation were evaluated. The nuclear factors controlling differentiation, hepatocyte nuclear factor (HNF)-4α, HNF-1α, HNF-6 and upstream stimulatory factor-1 (USF-1), and the oncogene Myc and alpha-fetoprotein (AFP) were measured. HNF-4α RNA interference was used to verify the role of HNF-4α. Embryonic induction effects were further tested in vivo by injecting HepG2 tumor cells into immunodeficient nude mice.

RESULTS

The 9-11-days chick liver extracts and 13.5-14.5-days mouse hepatoblast-enriched cells could inhibit proliferation and induce differentiation of HepG2 cells, leading to either death or maturation to hepatocytes. The maturation of surviving HepG2 cells was confirmed by increases in the expressions of HNF-4α, HNF-1α, HNF-6, and USF-1, and decreases in Myc and AFP. The embryonic induction of HepG2 cell maturation could be attenuated by HNF-4α RNA interference. Furthermore, the 13.5-days mouse hepatoblast culture completely eliminated HepG2 tumors with inhibited Myc and induced HNF-4α, confirming this embryonic induction effect in vivo.

CONCLUSIONS

This study demonstrated that developmental stage-specific embryonic induction of HepG2 cell differentiation might help in understanding embryonic differentiation and oncogenesis.

Multifunctional properties of chicken embryonic prenatal mesenchymal stem cells- pluripotency, plasticity, and tumor suppression

The chick embryo represents an accessible and economical in vivo model, which has long been used in developmental biology, gene expression analysis, and loss/gain of function experiments. In the present study, we assessed and characterized bone marrow derived mesenchymal stem cells from prenatal day 13 chicken embryos (chBMMSCs) and determined some novel properties. After assessing the mesenchymal stem cell (MSC) properties of these cells by the presence of their signature markers (CD 44, CD 73, CD 90, CD 105, and vimentin), we ascertained a very broad spectrum of multipotentiality as these MSCs not only differentiated into the classic tri-lineages of MSCs but also into ectodermal, endodermal, and mesodermal lineages such as neuron, hepatocyte, islet cell, and cardiac. In addition to wide plasticity, we detected the presence of several pluripotent markers such as Oct4, Sox2, and Nanog. This is the first study characterizing prenatal chBMMSCs and their ability to not only differentiate into mesenchymal lineages but also into all the germ cell layer lineages. Furthermore, our studies indicate that prenatal chBMMSCs derived from the chick provide an excellent model for multi-lineage development studies because of their broad plasticity and faithful reproduction of MSC traits as seen in the human. Here, we also present evidence for the first time that media derived from prenatal chBMMSC cultures have an anti-tumorigenic, anti-migratory, and pro-apoptotic effect on human tumors cells acting through the Wnt-ß-catenin pathway. These data confirm that chBMMSCs are enriched with factors in their secretome that are able to destroy tumor cells. This suggests a commonality of properties of MSCs across species between human and chicken.

Embryonic Chicken Transplantation is a Promising Model for Studying the Invasive Behavior of Melanoma Cells

Epithelial-to-mesenchymal transition is a hallmark event in the metastatic cascade conferring invasive ability to tumor cells. There are ongoing efforts to replicate the physiological events occurring during mobilization of tumor cells in model systems. However, few systems are able to capture these complex in vivo events. The embryonic chicken transplantation model has emerged as a useful system to assess melanoma cells including functions that are relevant to the metastatic process, namely invasion and plasticity. The chicken embryo represents an accessible and economical 3-dimensional in vivo model for investigating melanoma cell invasion as it exploits the ancestral relationship between melanoma and its precursor neural crest cells. We describe a methodology that enables the interrogation of melanoma cell motility within the developing avian embryo. This model involves the injection of melanoma cells into the neural tube of chicken embryos. Melanoma cells are labeled using fluorescent tracker dye, Vybrant DiO, then cultured as hanging drops for 24 h to aggregate the cells. Groups of approximately 700 cells are placed into the neural tube of chicken embryos prior to the onset of neural crest migration at the hindbrain level (embryonic day 1.5) or trunk level (embryonic day 2.5). Chick embryos are reincubated and analyzed after 48 h for the location of melanoma cells using fluorescent microscopy on whole mounts and cross-sections of the embryos. Using this system, we compared the in vivo invasive behavior of epithelial-like and mesenchymal-like melanoma cells. We report that the developing embryonic microenvironment confers motile abilities to both types of melanoma cells. Hence, the embryonic chicken transplantation model has the potential to become a valuable tool for in vivo melanoma invasion studies. Importantly, it may provide novel insights into and reveal previously unknown mediators of the metastatic steps of invasion and dissemination in melanoma.

Reprogramming of mesenchymal stem cells by oncogenes

Mesenchymal stem cells (MSCs) originate from embryonic mesoderm and give rise to the multiple lineages of connective tissues. Transformed MSCs develop into aggressive sarcomas, some of which are initiated by specific chromosomal translocations that generate fusion proteins with potent oncogenic properties. The sarcoma oncogenes typically prime MSCs through aberrant reprogramming. They dictate commitment to a specific lineage but prevent mature differentiation, thus locking the cells in a state of proliferative precursors. Deregulated expression of lineage-specific transcription factors and controllers of chromatin structure play a central role in MSC reprogramming and sarcoma pathogenesis. This suggests that reversing the epigenetic aberrancies created by the sarcoma oncogenes with differentiation-related reagents holds great promise as a beneficial addition to sarcoma therapies.