Horizontal gene transfers with or without cell fusions in all categories of the living matter

Hybrid Formation and Fusion of Cancer Cells In Vitro and In Vivo

Simple Summary

Cell fusion as a fundamental biological process is required for various physiological processes, including fertilization, placentation, myogenesis, osteoclastogenesis, and wound healing/tissue regeneration. However, cell fusion is also observed during pathophysiological processes like tumor development. Mesenchymal stroma/stem-like cells (MSC) which play an important role within the tumor microenvironment like other cell types such as macrophages can closely interact and hybridize with cancer cells. The formation of cancer hybrid cells can involve various different mechanisms whereby the genomic parts of the hybrid cells require rearrangement to form a new functional hybrid cell. The fusion of cancer cells with neighboring cell types may represent an important mechanism during tumor development since cancer hybrid cells are detectable in various tumor tissues. During this rare event with resulting genomic instability the cancer hybrid cells undergo a post-hybrid selection process (PHSP) to reorganize chromosomes of the two parental nuclei whereby the majority of the hybrid population undergoes cell death. The remaining cancer hybrid cells survive by displaying altered properties within the tumor tissue.

Abstract

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.

What prevents mainstream evolutionists teaching the whole truth about how genomes evolve?

The common belief that the neo-Darwinian Modern Synthesis (MS) was buttressed by the discoveries of molecular biology is incorrect. On the contrary those discoveries have undermined the MS. This article discusses the many processes revealed by molecular studies and genome sequencing that contribute to evolution but nonetheless lie beyond the strict confines of the MS formulated in the 1940s. The core assumptions of the MS that molecular studies have discredited include the idea that DNA is intrinsically a faithful self-replicator, the one-way transfer of heritable information from nucleic acids to other cell molecules, the myth of "selfish DNA", and the existence of an impenetrable Weismann Barrier separating somatic and germ line cells. Processes fundamental to modern evolutionary theory include symbiogenesis, biosphere interactions between distant taxa (including viruses), horizontal DNA transfers, natural genetic engineering, organismal stress responses that activate intrinsic genome change operators, and macroevolution by genome restructuring (distinct from the gradual accumulation of local microevolutionary changes in the MS). These 21st Century concepts treat the evolving genome as a highly formatted and integrated Read-Write (RW) database rather than a Read-Only Memory (ROM) collection of independent gene units that change by random copying errors. Most of the discoverers of these macroevolutionary processes have been ignored in mainstream textbooks and popularizations of evolutionary biology, as we document in some detail. Ironically, we show that the active view of evolution that emerges from genomics and molecular biology is much closer to the 19th century ideas of both Darwin and Lamarck. The capacity of cells to activate evolutionary genome change under stress can account for some of the most negative clinical results in oncology, especially the sudden appearance of treatment-resistant and more aggressive tumors following therapies intended to eradicate all cancer cells. Knowing that extreme stress can be a trigger for punctuated macroevolutionary change suggests that less lethal therapies may result in longer survival times.

The cnidarian origin of the proto-oncogenes NF-κB/STAT and WNT-like oncogenic pathway drives the ctenophores (Review)

The cell survival pathways of the diploblastic early multicellular eukaryotic hosts contain and operate the molecular machinery resembling those of malignantly transformed individual cells of highly advanced multicellular hosts (including Homo). In the present review, the STAT/NF-κB pathway of the cnidarian Nematostella vectensis is compared with that of human tumors (malignant lymphomas, including Reed-Sternberg cells) pointing out similarities, including possible viral initiation in both cases. In the ctenophore genome and proteome, β-catenin gains intranuclear advantages due to a physiologically weak destructive complex in the cytoplasm, and lack of natural inhibitors (the dickkopfs). Thus, a scenario similar to what tumor cells initiate and achieve is presented through several constitutive loss-of-function type mutations in the destructive complex and in the elimination of inhibitors. Vice versa, malignantly transformed individual cells of advanced multicellular hosts assume pheno-genotypic resemblance to cells of unicellular or early multicellular hosts, and presumably to their ancient predecessors, by returning to the semblance of immortality and to the resumption of the state of high degree of resistance to physicochemical insults. Human leukemogenic and oncogenic pathways are presented for comparisons. The supreme bioengineers RNA/DNA complex encoded both the malignantly transformed immortal cell and the human cerebral cortex. The former generates molecules for the immortality of cellular life in the Universe. The latter invents the inhibitors of the process in order to gain control over it.

Quantification of cell fusion events human breast cancer cells and breast epithelial cells using a Cre-LoxP-based double fluorescence reporter system

The biological phenomenon of cell fusion plays an important role in several physiological processes, like fertilization, placentation, or wound healing/tissue regeneration, as well as pathophysiological processes, such as cancer. Despite this fact, considerably less is still known about the factors and conditions that will induce the merging of two plasma membranes. Inflammation and proliferation has been suggested as a positive trigger for cell fusion, but it remains unclear, which of the factor(s) of the inflamed microenvironment are being involved. To clarify this we developed a reliable assay to quantify the in vitro fusion frequency of cells using a fluorescence double reporter vector (pFDR) containing a LoxP-flanked HcRed/DsRed expression cassette followed by an EGFP expression cassette. Because cell fusion has been implicated in cancer progression four human breast cancer cell lines were stably transfected with a pFDR vector and were co-cultured with the stably Cre-expressing human breast epithelial cell line. Cell fusion is associated with a Cre-mediated recombination resulting in induction of EGFP expression in hybrid cells, which can be quantified by flow cytometry. By testing a panel of different cytokines, chemokines, growth factors and other compounds, including exosomes, under normoxic and hypoxic conditions our data indicate that the proinflammatory cytokine TNF-α together with hypoxia is a strong inducer of cell fusion in human MDA-MB-435 and MDA-MB-231 breast cancer cells.

The cell survival pathways of the primordial RNA-DNA complex remain conserved in the extant genomes and may function as proto-oncogenes

Malignantly transformed (cancer) cells of multicellular hosts, including human cells, operate activated biochemical pathways that recognizably derived from unicellular ancestors. The descendant heat shock proteins of thermophile archaea now chaperon oncoproteins. The ABC cassettes of toxin-producer zooxantella Symbiodinia algae pump out the cytoplasmic toxin molecules; malignantly transformed cells utilize the derivatives of these cassettes to get rid of chemotherapeuticals. High mobility group helix-loop-helix proteins, protein arginine methyltransferases, proliferating cell nuclear antigens, and Ki-67 nuclear proteins, that protect and repair DNA in unicellular life forms, support oncogenes in transformed cells. The cell survival pathways of Wnt-β-catenin, Hedgehog, PI3K, MAPK-ERK, STAT, Ets, JAK, Pak, Myb, achaete scute, circadian rhythms, Bruton kinase and others, which are physiological in uni- and early multicellular eukaryotic life forms, are constitutively encoded in complex oncogenic pathways in selected single cells of advanced multicellular eukaryotic hosts. Oncogenes and oncoproteins in advanced multicellular hosts recreate selected independently living and immortalized unicellular life forms, which are similar to extinct and extant protists. These unicellular life forms are recognized at the clinics as autologous "cancer cells".

Development of a lentivirus vector-based assay for non-destructive monitoring of cell fusion activity

Cell-to-cell fusion can be quantified by endowing acceptor and donor cells with latent reporter genes/proteins and activators of these genes/proteins, respectively. One way to accomplish this goal is by using a bipartite lentivirus vector (LV)-based cell fusion assay system in which the cellular fusion partners are transduced with a flippase-activatable Photinus pyralis luciferase (PpLuc) expression unit (acceptor cells) or with a recombinant gene encoding FLPe^NLS+, a nuclear-targeted and molecularly evolved version of flippase (donor cells). Fusion of both cell populations will lead to the FLPe-dependent generation of a functional PpLuc gene. PpLuc activity is typically measured in cell lysates, precluding consecutive analysis of one cell culture. Therefore, in this study the PpLuc-coding sequence was replaced by that of Gaussia princeps luciferase (GpLuc), a secretory protein allowing repeated analysis of the same cell culture. In myotubes the spread of FLPe^NLS+ may be limited due to its nuclear localization signal (NLS) causing low signal outputs. To test this hypothesis, myoblasts were transduced with LVs encoding either FLPe^NLS+ or an NLS-less version of FLPe (FLPe^NLS−) and subsequently co-cultured in different ratios with myoblasts containing the FLPe-activatable GpLuc expression cassette. At different times after induction of cell-to-cell fusion the GpLuc activity in the culture medium was determined. FLPe^NLS+ and FLPe^NLS− both activated the latent GpLuc gene but when the percentage of FLPe-expressing myoblasts was limiting, FLPe^NLS+ generally yielded slightly higher signals than FLPe^NLS− while at low acceptor-to-donor cell ratios FLPe^NLS− was usually superior. The ability of FLPe^NLS+ to spread through myofibers and to induce reporter gene expression is thus not limited by its NLS. However, at high FLPe concentrations the presence of the NLS negatively affected reporter gene expression. In summary, a rapid and simple chemiluminescence assay for quantifying cell-to-cell fusion progression based on GpLuc has been developed.

Toxoplasmosis and Polygenic Disease Susceptibility Genes: Extensive Toxoplasma gondii Host/Pathogen Interactome Enrichment in Nine Psychiatric or Neurological Disorders

Toxoplasma gondii is not only implicated in schizophrenia and related disorders, but also in Alzheimer's or Parkinson's disease, cancer, cardiac myopathies, and autoimmune disorders. During its life cycle, the pathogen interacts with ~3000 host genes or proteins. Susceptibility genes for multiple sclerosis, Alzheimer's disease, schizophrenia, bipolar disorder, depression, childhood obesity, Parkinson's disease, attention deficit hyperactivity disorder (P  from  8.01E - 05  (ADHD)  to  1.22E - 71) (multiple sclerosis), and autism (P = 0.013), but not anorexia or chronic fatigue are highly enriched in the human arm of this interactome and 18 (ADHD) to 33% (MS) of the susceptibility genes relate to it. The signalling pathways involved in the susceptibility gene/interactome overlaps are relatively specific and relevant to each disease suggesting a means whereby susceptibility genes could orient the attentions of a single pathogen towards disruption of the specific pathways that together contribute (positively or negatively) to the endophenotypes of different diseases. Conditional protein knockdown, orchestrated by T. gondii proteins or antibodies binding to those of the host (pathogen derived autoimmunity) and metabolite exchange, may contribute to this disruption. Susceptibility genes may thus be related to the causes and influencers of disease, rather than (and as well as) to the disease itself.

Smelt was the likely beneficiary of an antifreeze gene laterally transferred between fishes

Background

Type II antifreeze protein (AFP) from the rainbow smelt, Osmerus mordax, is a calcium-dependent C-type lectin homolog, similar to the AFPs from herring and sea raven. While C-type lectins are ubiquitous, type II AFPs are only found in a few species in three widely separated branches of teleost fishes. Furthermore, several other non-homologous AFPs are found in intervening species. We have previously postulated that this sporadic distribution has resulted from lateral gene transfer. The alternative hypothesis, that the AFP evolved from a lectin present in a shared ancestor and that this gene was lost in most species, is not favored because both the exon and intron sequences are highly conserved.

Results

Here we have sequenced and annotated a 160 kb smelt BAC clone containing a centrally-located AFP gene along with 14 other genes. Quantitative PCR indicates that there is but a single copy of this gene within the smelt genome, which is atypical for fish AFP genes. The corresponding syntenic region has been identified and searched in a number of other species and found to be devoid of lectin or AFP sequences. Unlike the introns of the AFP gene, the intronic sequences of the flanking genes are not conserved between species. As well, the rate and pattern of mutation in the AFP gene are radically different from those seen in other smelt and herring genes.

Conclusions

These results provide stand-alone support for an example of lateral gene transfer between vertebrate species. They should further inform the debate about genetically modified organisms by showing that gene transfer between ‘higher’ eukaryotes can occur naturally. Analysis of the syntenic regions from several fishes strongly suggests that the smelt acquired the AFP gene from the herring.

Oncogenic extracellular vesicles in brain tumor progression

The brain is a frequent site of neoplastic growth, including both primary and metastatic tumors. The clinical intractability of many brain tumors and their distinct biology are implicitly linked to the unique microenvironment of the central nervous system (CNS) and cellular interactions within. Among the most intriguing forms of cellular interactions is that mediated by membrane-derived extracellular vesicles (EVs). Their biogenesis (vesiculation) and uptake by recipient cells serves as a unique mechanism of intercellular trafficking of complex biological messages including the exchange of molecules that cannot be released through classical secretory pathways, or that are prone to extracellular degradation. Tumor cells produce EVs containing molecular effectors of several cancer-related processes such as growth, invasion, drug resistance, angiogenesis, and coagulopathy. Notably, tumor-derived EVs (oncosomes) also contain oncogenic proteins, transcripts, DNA, and microRNA (miR). Uptake of this material may change properties of the recipient cells and impact the tumor microenvironment. Examples of transformation-related molecules found in the cargo of tumor-derived EVs include the oncogenic epidermal growth factor receptor (EGFRvIII), tumor suppressors (PTEN), and oncomirs (miR-520g). It is postulated that EVs circulating in blood or cerebrospinal fluid (CSF) of brain tumor patients may be used to decipher molecular features (mutations) of the underlying malignancy, reflect responses to therapy, or molecular subtypes of primary brain tumors [e.g., glioma or medulloblastoma (MB)]. It is possible that metastases to the brain may also emit EVs with clinically relevant oncogenic signatures. Thus, EVs emerge as a novel and functionally important vehicle of intercellular communication that can mediate multiple biological effects. In addition, they provide a unique platform to develop molecular biomarkers in brain malignancies.

Vaccinia and other viruses with available vaccines show marked homology with the HIV-1 envelope glycoprotein: the prospect of using existing vaccines to stem the AIDS pandemic

Cross-reactive immunity occurs when infection with or vaccination against one virus protects against another related family member. A search for homologues of the HIV-1 envelope glycoprotein revealed that it is composed of thousands of intercalating and overlapping viral matches of pentapeptide or longer gapped consensi, belonging to over 70% of the currently sequenced virome, infecting all kingdoms from bacteria to man. It was also highly homologous to proteins from the Visna/Maedi and other ovine viruses, while other proteins (nef/tat/gag/pol) were homologous to proteins from the equine infectious anaemia virus and HTLV-2/HTLV-3 viruses. This phenomenon suggests that horizontal gene transfer from coinfecting RNA and DNA viruses to retroviruses is extensive, providing a route for the subsequent insertion of non-retroviral genes into human and other genomes via retroviral integration. This homology includes all viruses for which vaccines already exist. Cross-reactive immunity may be operative in AIDS, as Vaccinia vaccination decreases viral replication in HIV-1 infected patients' cells, for the CCR5 tropic form. Measles, Dengue virus, or GB virus C infections also decrease the HIV-1 viral load. A resumption of Vaccinia/smallpox vaccination might be expected to have a significant effect on the AIDS pandemic, and a careful study of the potential uses of other existing viral and bacterial vaccines merits close attention. This phenomenon may also be relevant to other recalcitrant viruses, bacteria, and parasites for which no vaccine exists and the armory of existing vaccines may have a role to play in diseases other than those for which they were designed.

Co-cultivation of murine BMDCs with 67NR mouse mammary carcinoma cells give rise to highly drug resistant cells

Background

Tumor tissue resembles chronically inflamed tissue. Since chronic inflammatory conditions are a strong stimulus for bone marrow-derived cells (BMDCs) it can be assumed that recruitment of BMDCs into cancer tissue should be a common phenomenon. Several data have outlined that BMDC can influence tumor growth and metastasis, e.g., by inducing a paracrine acting feedback loop in tumor cells. Likewise, cell fusion and horizontal gene transfer are further mechanisms how BMDCs can trigger tumor progression.

Results

Hygromycin resistant murine 67NR-Hyg mammary carcinoma cells were co-cultivated with puromycin resistant murine BMDCs from Tg(GFPU)5Nagy/J mice. Isolation of hygromycin/puromycin resistant mBMDC/67NR-Hyg cell clones was performed by a dual drug selection procedure. PCR analysis revealed an overlap of parental markers in mBMDC/67NR-Hyg cell clones, suggesting that dual resistant cells originated by cell fusion. By contrast, both STR and SNP data analysis indicated that only parental 67NR-Hyg alleles were found in mBMDC/67NR-Hyg cell clones favoring horizontal gene transfer as the mode of origin. RealTime-PCR-array analysis showed a marked up-regulation of Abcb1a and Abcb1b ABC multidrug transporters in mBMDC/67NR-Hyg clones, which was verified by Western Blot analysis. Moreover, the markedly increased Abcb1a/Abcb1b expression was correlated to an efficient Rhodamine 123 efflux, which was completely inhibited by verapamil, a well-known Abcb1a/Abcb1b inhibitor. Likewise, mBMDCs/67NR-Hyg clones revealed a marked resistance towards chemotherapeutic drugs including 17-DMAG, doxorubicin, etoposide and paclitaxel. In accordance to Rhodamine 123 efflux data, chemotherapeutic drug resistance of mBMDC/67NR-Hyg cells was impaired by verapamil mediated blockage of Abc1a/Abcb1b multidrug transporter function.

Conclusion

Co-cultivation of mBMDCs and mouse 67NR-Hyg mammary carcinoma cells gave rise to highly drug resistant cells. Even though it remains unknown whether mBMDC/67NR-Hyg clones originated by cell fusion or horizontal gene transfer, our data indicate that the exchange of genetic information between two cellular entities is crucial for the origin of highly drug resistant cancer (hybrid) cells, which might be capable to survive chemotherapy.