Horizontal transmission of malignancy by cell-cell fusion

Regulation of cancer stem cells and immunotherapy of glioblastoma (Review)

Glioblastoma (GB) is one of the most adverse diagnoses in oncology. Complex current treatment results in a median survival of 15 months. Resistance to treatment is associated with the presence of cancer stem cells (CSCs). The present review aimed to analyze the mechanisms of CSC plasticity, showing the particular role of β-catenin in regulating vital functions of CSCs, and to describe the molecular mechanisms of Wnt-independent increase of β-catenin levels, which is influenced by the local microenvironment of CSCs. The present review also analyzed the reasons for the low effectiveness of using medication in the regulation of CSCs, and proposed the development of immunotherapy scenarios with tumor cell vaccines, containing heterogenous cancer cells able of producing a multidirectional antineoplastic immune response. Additionally, the possibility of managing lymphopenia by transplanting hematopoietic stem cells from a healthy sibling and using clofazimine or other repurposed drugs that reduce β-catenin concentration in CSCs was discussed in the present study.

Synthetic circuits based on split Cas9 to detect cellular events

Synthetic biology involves the engineering of logic circuit gates that process different inputs to produce specific outputs, enabling the creation or control of biological functions. While CRISPR has become the tool of choice in molecular biology due to its RNA-guided targetability to other nucleic acids, it has not been frequently applied to logic gates beyond those controlling the guide RNA (gRNA). In this study, we present an adaptation of split Cas9 to generate logic gates capable of sensing biological events, leveraging a Cas9 reporter (EGxxFP) to detect occurrences such as cancer cell origin, epithelial to mesenchymal transition (EMT), and cell-cell fusion. First, we positioned the complementing halves of split Cas9 under different promoters-one specific to cancer cells of epithelial origin (phCEA) and the other a universal promoter. The use of self-assembling inteins facilitated the reconstitution of the Cas9 halves. Consequently, only cancer cells with an epithelial origin activated the reporter, exhibiting green fluorescence. Subsequently, we explored whether this system could detect biological processes such as epithelial to mesenchymal transition (EMT). To achieve this, we designed a logic gate where one half of Cas9 is expressed under the phCEA, while the other is activated by TWIST1. The results showed that cells undergoing EMT effectively activated the reporter. Next, we combined the two inputs (epithelial origin and EMT) to create a new logic gate, where only cancer epithelial cells undergoing EMT activated the reporter. Lastly, we applied the split-Cas9 logic gate as a sensor of cell-cell fusion, both in induced and naturally occurring scenarios. Each cell type expressed one half of split Cas9, and the induction of fusion resulted in the appearance of multinucleated syncytia and the fluorescent reporter. The simplicity of the split Cas9 system presented here allows for its integration into various cellular processes, not only as a sensor but also as an actuator.

Challenges and Prospects of Patient-Derived Xenografts for Cancer Research

We discuss the importance of the in vivo models in elucidating cancer biology, focusing on the patient-derived xenograft (PDX) models, which are classic and standard functional in vivo platforms for preclinical evaluation. We provide an overview of the most representative models, including cell-derived xenografts (CDX), tumor and metastatic cell-derived xenografts, and PDX models utilizing humanized mice (HM). The orthotopic models, which could reproduce the cancer environment and its progression, similar to human tumors, are particularly common. The standard procedures and rationales of gastric adenocarcinoma (GAC) orthotopic models are addressed. Despite the significant advantages of the PDX models, such as recapitulating key features of human tumors and enabling drug testing in the in vivo context, some challenges must be acknowledged, including loss of heterogeneity, selection bias, clonal evolution, stroma replacement, tumor micro-environment (TME) changes, host cell carryover and contaminations, human-to-host cell oncogenic transformation, human and host viral infections, as well as limitations for immunologic research. To compensate for these limitations, other mouse models, such as syngeneic and humanized mouse models, are currently utilized. Overall, the PDX models represent a powerful tool in cancer research, providing critical insights into tumor biology and potential therapeutic targets, but their limitations and challenges must be carefully considered for their effective use. Lastly, we present an intronic quantitative PCR (qPCR) method to authenticate, detect, and quantify human/murine cells in cell lines and PDX samples.

Tumor malignancy by genetic transfer between cells forming cell-in-cell structures

Cell-in-cell structures (CICs) refer to a type of unique structure with one or more cells within another one, whose biological outcomes are poorly understood. The present study aims to investigate the effects of CICs formation on tumor progression. Using genetically marked hepatocellular cancer cell lines, we explored the possibility that tumor cells might acquire genetic information and malignant phenotypes from parental cells undergoing CICs formation. The present study showed that the derivatives, isolated from CICs formed between two subpopulations by flow cytometry sorting, were found to inherit aggressive features from the parental cells, manifested with increased abilities in both proliferation and invasiveness. Consistently, the CICs clones expressed a lower level of E-cadherin and a higher level of Vimentin, ZEB-1, Fibronectin, MMP9, MMP2 and Snail as compared with the parental cells, indicating epithelial-mesenchymal transition. Remarkably, the new derivatives exhibited significantly enhanced tumorigenicity in the xenograft mouse models. Moreover, whole exome sequencing analysis identified a group of potential genes which were involved in CIC-mediated genetic transfer. These results are consistent with a role of genetic transfer by CICs formation in genomic instability and malignancy of tumor cells, which suggest that the formation of CICs may promote genetic transfer and gain of malignancy during tumor progression.

A new intronic quantitative PCR method led to the discovery of transformation from human ascites to murine malignancy in a mouse model

Purpose

To establish a fast and accurate detection method for interspecies contaminations in the patient-derived xenograft (PDX) models and cell lines, and to elucidate possible mechanisms if interspecies oncogenic transformation is detected.

Methods

A fast and highly sensitive intronic qPCR method detecting Gapdh intronic genomic copies was developed to quantify if cells were human or murine or a mixture. By this method, we documented that murine stromal cells were abundant in the PDXs; we also authenticated our cell lines to be human or murine.

Results

In one mouse model, GA0825-PDX transformed murine stromal cells into a malignant tumorigenic murine P0825 cell line. We traced the timeline of this transformation and discovered three subpopulations descended from the same GA0825-PDX model: epithelium-like human H0825, fibroblast-like murine M0825, and main passaged murine P0825 displayed differences in tumorigenic capability in vivo. P0825 was the most aggressive and H0825 was weakly tumorigenic. Immunofluorescence (IF) staining revealed that P0825 cells highly expressed several oncogenic and cancer stem cell markers. Whole exosome sequencing (WES) analysis revealed that TP53 mutation in the human ascites IP116-generated GA0825-PDX may have played a role in the human-to-murine oncogenic transformation.

Conclusion

This intronic qPCR is able to quantify human/mouse genomic copies with high sensitivity and within a time frame of a few hours. We are the first to use intronic genomic qPCR for authentication and quantification of biosamples. Human ascites transformed murine stroma into malignancy in a PDX model.

Stress-Induced Polyploid Giant Cancer Cells: Unique Way of Formation and Non-Negligible Characteristics

Polyploidy is a conserved mechanism in cell development and stress responses. Multiple stresses of treatment, including radiation and chemotherapy drugs, can induce the polyploidization of tumor cells. Through endoreplication or cell fusion, diploid tumor cells convert into giant tumor cells with single large nuclei or multiple small nucleuses. Some of the stress-induced colossal cells, which were previously thought to be senescent and have no ability to proliferate, can escape the fate of death by a special way. They can remain alive at least before producing progeny cells through asymmetric cell division, a depolyploidization way named neosis. Those large and danger cells are recognized as polyploid giant cancer cells (PGCCs). Such cells are under suspicion of being highly related to tumor recurrence and metastasis after treatment and can bring new targets for cancer therapy. However, differences in formation mechanisms between PGCCs and well-accepted polyploid cancer cells are largely unknown. In this review, the methods used in different studies to induce polyploid cells are summarized, and several mechanisms of polyploidization are demonstrated. Besides, we discuss some characteristics related to the poor prognosis caused by PGCCs in order to provide readers with a more comprehensive understanding of these huge cells.

Human cell polyploidization: The good and the evil

Therapeutic resistance represents a major cause of death for most lethal cancers. However, the underlying mechanisms of such resistance have remained unclear. The polyploid cells are due to an increase in DNA content, commonly associated with cell enlargement. In human, they play a variety of roles in physiology and pathologic conditions and perform the specialized functions during development, inflammation, and cancer. Recent work shows that cancer cells can be induced into polyploid giant cancer cells (PGCCs) that leads to reprogramming of surviving cancer cells to acquire resistance. In this article, we will review the polyploidy involved in development and inflammation, and the process of PGCCs formation and propagation that benefits to cell survival. We will discuss the potential opportunities in fighting resistant cancers. The increased knowledge of PGCCs will offer a completely new paradigm to explore the therapeutic intervention for lethal cancers.

Downregulation of miRNA-146a-5p promotes malignant transformation of mesenchymal stromal/stem cells by glioma stem-like cells

Mesenchymal stromal/stem cells (MSCs) are promising carriers in cell-based therapies against central nervous system diseases, and have been evaluated in various clinical trials in recent years. However, bone marrow-derived MSCs (BMSCs) are reportedly involved in tumorigenesis initiated by glioma stem-like cells (GSCs). We therefore established three different orthotopic models of GSC-MSC interactions in vivo using dual-color fluorescence tracing. Cell sorting and micropipetting techniques were used to obtain highly proliferative MSC monoclones from each model, and these cells were identified as transformed MSC lines 1, 2 and 3. Nineteen miRNAs were upregulated and 24 miRNAs were downregulated in all three transformed MSC lines compared to normal BMSCs. Reduced miR-146a-5p expression in the transformed MSCs was associated with their proliferation, malignant transformation and overexpression of heterogeneous nuclear ribonucleoprotein D. These findings suggest that downregulation of miR-146a-5p leads to overexpression of its target gene, heterogeneous nuclear ribonucleoprotein D, thereby promoting malignant transformation of MSCs during interactions with GSCs. Given the risk that MSCs will undergo malignant transformation in the glioma microenvironment, targeted glioma therapies employing MSCs as therapeutic carriers should be considered cautiously.

Genome remodeling upon mesenchymal tumor cell fusion contributes to tumor progression and metastatic spread

Cell fusion in tumor progression mostly refers to the merging of a cancer cell with a cell that has migration and immune escape capabilities such as macrophages. Here we show that spontaneous hybrids made from the fusion of transformed mesenchymal cells with partners from the same lineage undergo nonrecurrent large-scale genomic rearrangements, leading to the creation of highly aneuploid cells with novel phenotypic traits, including metastatic spreading capabilities. Moreover, in contrast to their parents, hybrids were the only cells able to recapitulate in vivo all features of human pleomorphic sarcomas, a rare and genetically complex mesenchymal tumor. Hybrid tumors not only displayed specific mesenchymal markers, but also combined a complex genetic profile with a highly metastatic behavior, like their human counterparts. Finally, we provide evidence that patient-derived pleomorphic sarcoma cells are inclined to spontaneous cell fusion. The resulting hybrids also gain in aggressiveness, exhibiting superior growth capacity in mouse models. Altogether, these results indicate that cell fusion has the potential to promote cancer progression by increasing growth and/or metastatic capacities, regardless of the nature of the companion cell. Moreover, such events likely occur upon sarcoma development, paving the way for better understanding of the biology, and aggressiveness of these tumors.

Tumor Microenvironment and Cell Fusion

Cell fusion is a highly regulated biological process that occurs under both physiological and pathological conditions. The cellular and extracellular environment is critical for the induction of the cell-cell fusion. Aberrant cell fusion is initiated during tumor progression. Tumor microenvironment is a complex dynamic system formed by the interaction between tumor cells and their surrounding cells. Cell-cell fusion mediates direct interaction between tumor cells and their surrounding cells and is associated with tumor initiation and progression. Various microenvironmental factors affect cell fusion in tumor microenvironment and generate hybrids that acquire genomes of both parental cells and exhibit novel characteristics, such as tumor stem cell-like properties, radioresistance, drug resistance, immune evasion, and enhanced migration and invasion abilities, which are closely related to the initiation, invasion, and metastasis of tumor. The phenotypic characteristics of hybrids are based on the phenotypes of parental cells, and the fusion of tumor cells with diverse types of microenvironmental fusogenic cells is concomitant with phenotypic heterogeneity. This review highlights the types of fusogenic cells in tumor microenvironment that can fuse with tumor cells and their specific significance and summarizes the various microenvironmental factors affecting tumor cell fusion. This review may be used as a reference to develop strategies for future research on tumor cell fusion and the exploration of cell fusion-based antitumor therapies.

Induction and characterization of anti-tumor endothelium immunity elicited by ValloVax therapeutic cancer vaccine

ValloVax is a placental endothelium derived vaccine which induces tissue-nonspecific antitumor immunity by blocking tumor angiogesis. To elucidate mechanisms of action, we showed that production of ValloVax, which involves treating placental endothelial cells with IFN-gamma, results in upregulation of HLA and costimulatory molecules. It was shown that in mixed lymphocyte reaction, ValloVax induces Type I cytokines and allo-proliferative responses. Plasma from ValloVax immunized mice was capable of killing in vitro tumor-like endothelium but not control endothelium. Using defined antigens associated with tumor endothelial cells, specific molecular entities were identified as being targeted by ValloVax induced antibodies. Binding of predominantly IgG antibodies to ValloVax cells was confirmed by flow cytometry. Further suggesting direct killing of tumor endothelial cells was expression of TUNEL positive cells, as well as, reduction in tumor oxygenation. Supporting a role for antibody mediated responses, cell depletion experiments suggested a predominant role of B cells in maintaining an intact anti-tumor endothelial response. Adoptive transfer experiments suggested that infusion of CD3+ T cells from immunized mice was sufficient to transfer tumor protection. Generation of memory T cells selective to tumor endothelial specific markers was observed. Functional confirmation of memory responses was observed in tumor rechallenge experiments. Furthermore, we observed that both PD-1 or CTLA-4 blockade augmented antitumor effects of ValloVax. These data suggest a T cell induced B cell mediated anti-tumor endothelial response and set the framework clinical trials through elucidation of mechanism of action.

Invadosomes are coming: new insights into function and disease relevance

Invadopodia and podosomes are discrete, actin-based molecular protrusions that form in cancer cells and normal cells, respectively, in response to diverse signaling pathways and extracellular matrix cues. Although they participate in a host of different cellular processes, they share a common functional theme of controlling pericellular proteolytic activity, which sets them apart from other structures that function in migration and adhesion, including focal adhesions, lamellipodia, and filopodia. In this review, we highlight research that explores the function of these complex structures, including roles for podosomes in embryonic and postnatal development, in angiogenesis and remodeling of the vasculature, in maturation of the postsynaptic membrane, in antigen sampling and recognition, and in cell-cell fusion mechanisms, as well as the involvement of invadopodia at multiple steps of the metastatic cascade, and how all of this may apply in the treatment of human disease states. Finally, we explore recent research that implicates a novel role for exosomes and microvesicles in invadopodia-dependent and invadopodia-independent mechanisms of invasion, respectively.

State of the art in cell-cell fusion

Mammalian life begins with a cell-cell fusion event, i.e. the fusion of the spermatozoid with the oocyte and needs further cell-cell fusion processes for the development, growth, and maintenance of tissues and organs over the whole life span. Furthermore, cellular fusion plays a role in infection, cancer, and stem cell-dependent regeneration as well as including an expanded meaning of partial cellular fusion, nanotube formation, and microparticle-cell fusion. The cellular fusion process is highly regulated by proteins which carry the information to organize and regulate membranes allowing the merge of two separate lipid bilayers into one. The regulation of this genetically and epigenetically controlled process is achieved by different kinds of signals leading to communication of fusing cells. The local cellular and extracellular environment additionally initiates specific cell signaling necessary for the induction of the cell-cell fusion process. Common motifs exist in distinct cell-cell fusion processes and their regulation. However, there is specific regulation of different cell-cell fusion processes, e.g. myoblast, placental, osteoclast, and stem cell fusion. Hence, specialized fusion events vary between cell types and species. Molecular mechanisms remain largely unknown, especially limited knowledge is present for cancer and stem cell fusion mechanisms and regulation. More research is necessary for the understanding of cellular fusion processes which can lead to development of new therapeutic strategies grounding on cellular fusion regulation.

Learning about the Importance of Mutation Prevention from Curable Cancers and Benign Tumors

Some cancers can be cured by chemotherapy or radiotherapy, presumably because they are derived from those cell types that not only can die easily but also have already been equipped with mobility and adaptability, which would later allow the cancers to metastasize without the acquisition of additional mutations. From a viewpoint of biological dispersal, invasive and metastatic cells may, among other possibilities, have been initial losers in the competition for resources with other cancer cells in the same primary tumor and thus have had to look for new habitats in order to survive. If this is really the case, manipulation of their ecosystems, such as by slightly ameliorating their hardship, may prevent metastasis. Since new mutations may occur, especially during and after therapy, to drive progression of cancer cells to metastasis and therapy-resistance, preventing new mutations from occurring should be a key principle for the development of new anticancer drugs. Such new drugs should be able to kill cancer cells very quickly without leaving the surviving cells enough time to develop new mutations and select resistant or metastatic clones. This principle questions the traditional use and the future development of genotoxic drugs for cancer therapy.

Advantages of a dual-color fluorescence-tracing glioma orthotopic implantation model: Detecting tumor location, angiogenesis, cellular fusion and the tumor microenvironment

Various organs of the body have distinct microenvironments with diverse biological characteristics that can influence the growth of tumors within them. However, the mechanisms underlying the interactions between tumor and host cells are currently not well understood. In the present study, a dual-color fluorescence-tracing glioma orthotopic implantation model was developed, in which C6 rat glioma cells labeled with the red fluorescent dye CM-Dil, and SU3 human glioma cells stably expressing red fluorescence protein, were inoculated into the right caudate nucleus of transgenic female C57BL/6 nude mice expressing enhanced green fluorescent protein. The dual-color tracing with whole-body in vivo fluorescence imaging of xenografts was performed using a live imaging system. Frozen sections of the transplanted tumor were prepared for histological analyses, in order to detect the presence of invading tumor cells, blood vessels and cellular fusion. Dual-color images were able to distinguish between red tumor cells and green host cells. The results of the present study suggested that a dual-color fluorescence-tracing glioma orthotopic implantation model may be convenient for detecting tumor location, angiogenesis, cellular fusion, and the tumor microenvironment.

Aberrant cytokinesis and cell fusion result in multinucleation in HepG2 cells exposed to silica nanoparticles

The multinucleation effect of silica nanoparticles (SiNPs) had been determined in our previous studies, but the relative mechanisms of multinucleation and how the multinucleated cells are generated were still not clear. This extensional study was conducted to investigate the mechanisms underlying the formation of multinucleated cells after SiNPs exposure. We first investigated cellular multinucleation, then performed time-lapse confocal imaging to certify whether the multinucleated cells resulted from cell fusion or abnormal cell division. Our results confirmed for the first time that there are three patterns contributing to the SiNPs-induced multinucleation in HepG2 cells: cell fusion, karyokinesis without cytokinesis, and cytokinesis followed by fusion. The chromosomal passenger complex (CPC) deficiency and cell cycle arrest in G1/S and G2/M checkpoints may be responsible for the cell aberrant cytokinesis. The activated MAPK/ERK1/2 signaling and decreased mitosis related proteins might be the underlying mechanism of cell cycle arrest and thus multinucleation. In summary, we confirmed the hypothesis that aberrant cytokinesis and cell fusion resulted in multinucleation in HepG2 cells after SiNPs exposure. Since cell fusion and multinucleation were involved in genetic instability and tumor development, this study suggests the potential ability of SiNPs to induce cellular genetic instability. These findings raise concerns with regard to human health hazards and environmental risks with SiNPs exposure.

Experimental research of host macrophage canceration induced by glioma stem progenitor cells

The involvement of tumor-associated macrophages in tumor progression is an indisputable fact. However, whether the growth-promotion effects of macrophages towards tumors in the aggressive stage affect their own canceration remains unknown. In the present study, human glioma stem/progenitor cells transfected with red fluorescent protein gene (SU3-RFP) were seeded inside the abdominal cavity of transgenic nude mice, of which all nucleated cells could express green fluorescent protein (GFP), forming a tumor model with a double-color RFP/GFP fluorescent tracer. Ascites and tumor nodules from tumor-bearing mice were cultured, then the GFP⁺ cells were separated for clonal culture and further related phenotypic characterization and tumorigenicity tests. It was observed that the GFP⁺ cells isolated from ascites and solid tumors exhibited unlimited proliferative potential; the monoclonal cells were mouse-original, had a cancer cell phenotype and expressed the macrophage marker protein CD68. Thus, in the abdominal tumor model with double-color fluorescent tracer, macrophages recruited by tumor cells not only promoted tumor cell growth, but also exhibited their own canceration. This discovery is significant for the further study of tumor tissue remodeling and the tumor microenvironment.

In-vivo fusion of human cancer and hamster stromal cells permanently transduces and transcribes human DNA

After demonstrating, with karyotyping, polymerase chain reaction (PCR) and fluorescence in-situ hybridization, the retention of certain human chromosomes and genes following the spontaneous fusion of human tumor and hamster cells in-vivo, it was postulated that cell fusion causes the horizontal transmission of malignancy and donor genes. Here, we analyzed gene expression profiles of 3 different hybrid tumors first generated in the hamster cheek pouch after human tumor grafting, and then propagated in hamsters and in cell cultures for years: two Hodgkin lymphomas (GW-532, GW-584) and a glioblastoma multiforme (GB-749). Based on the criteria of MAS 5.0 detection P-values ≤0.065 and at least a 2-fold greater signal expression value than a hamster melanoma control, we identified 3,759 probe sets (ranging from 1,040 to 1,303 in each transplant) from formalin-fixed, paraffin-embedded sections of the 3 hybrid tumors, which unambiguously mapped to 3,107 unique Entrez Gene IDs, representative of all human chromosomes; however, by karyology, one of the hybrid tumors (GB-749) had a total of 15 human chromosomes in its cells. Among the genes mapped, 39 probe sets, representing 33 unique Entrez Gene IDs, complied with the detection criteria in all hybrid tumor samples. Five of these 33 genes encode transcription factors that are known to regulate cell growth and differentiation; five encode cell adhesion- and transmigration-associated proteins that participate in oncogenesis and/or metastasis and invasion; and additional genes encode proteins involved in signaling pathways, regulation of apoptosis, DNA repair, and multidrug resistance. These findings were corroborated by PCR and reverse transcription PCR, showing the presence of human alphoid (α)-satellite DNA and the F11R transcripts in additional tumor transplant generations. We posit that in-vivo fusion discloses genes implicated in tumor progression, and gene families coding for the organoid phenotype. Thus, cancer cells can transduce adjacent stromal cells, with the resulting progeny having permanently transcribed genes with malignant and other gene functions of the donor DNA. Using heterospecific in-vivo cell fusion, genes encoding oncogenic and organogenic traits may be identified.

Just like the rest of evolution in Mother Nature, the evolution of cancers may be driven by natural selection, and not by haphazard mutations

Sporadic carcinogenesis starts from immortalization of a differentiated somatic cell or an organ-specific stem cell. The immortalized cell incepts a new or quasinew organism that lives like a parasite in the patient and usually proceeds to progressive simplification, constantly engendering intermediate organisms that are simpler than normal cells. Like organismal evolution in Mother Nature, this cellular simplification is a process of Darwinian selection of those mutations with growth- or survival-advantages, from numerous ones that occur randomly and stochastically. Therefore, functional gain of growth- or survival-sustaining oncogenes and functional loss of differentiation-sustaining tumor suppressor genes, which are hallmarks of cancer cells and contribute to phenotypes of greater malignancy, are not drivers of carcinogenesis but are results from natural selection of advantageous mutations. Besides this mutation-load dependent survival mechanism that is evolutionarily low and of an asexual nature, cancer cells may also use cell fusion for survival, which is an evolutionarily-higher mechanism and is of a sexual nature. Assigning oncogenes or tumor suppressor genes or their mutants as drivers to induce cancer in animals may somewhat coerce them to create man-made oncogenic pathways that may not really be a course of sporadic cancer formations in the human.

Horizontal transmission of malignancy: in-vivo fusion of human lymphomas with hamster stroma produces tumors retaining human genes and lymphoid pathology

We report the in-vivo fusion of two Hodgkin lymphomas with golden hamster cheek pouch cells, resulting in serially-transplanted (over 5-6 years) GW-532 and GW-584 heterosynkaryon tumor cells displaying both human and hamster DNA (by FISH), lymphoma-like morphology, aggressive metastasis, and retention of 7 human genes (CD74, CXCR4, CD19, CD20, CD71, CD79b, and VIM) out of 24 tested by PCR. The prevalence of B-cell restricted genes (CD19, CD20, and CD79b) suggests that this uniform population may be the clonal initiating (malignant) cells of Hodgkin lymphoma, despite their not showing translation to their respective proteins by immunohistochemical analysis. This is believed to be the first report of in-vivo cell-cell fusion of human lymphoma and rodent host cells, and may be a method to disclose genes regulating both organoid and metastasis signatures, suggesting that the horizontal transfer of tumor DNA to adjacent stromal cells may be implicated in tumor heterogeneity and progression. The B-cell gene signature of the hybrid xenografts suggests that Hodgkin lymphoma, or its initiating cells, is a B-cell malignancy.

On the origin of cancer metastasis

Metastasis involves the spread of cancer cells from the primary tumor to surrounding tissues and to distant organs and is the primary cause of cancer morbidity and mortality. In order to complete the metastatic cascade, cancer cells must detach from the primary tumor, intravasate into the circulatory and lymphatic systems, evade immune attack, extravasate at distant capillary beds, and invade and proliferate in distant organs. Currently, several hypotheses have been advanced to explain the origin of cancer metastasis. These involve an epithelial mesenchymal transition, an accumulation of mutations in stem cells, a macrophage facilitation process, and a macrophage origin involving either transformation or fusion hybridization with neoplastic cells. Many of the properties of metastatic cancer cells are also seen in normal macrophages. A macrophage origin of metastasis can also explain the long-standing "seed and soil" hypothesis and the absence of metastasis in plant cancers. The view of metastasis as a macrophage metabolic disease can provide novel insight for therapeutic management.