Abstract

Cancer vaccines based on tumor cell components have shown promising results in animal and clinical studies. The vaccine system contains abundant tumor antigen components, which can activate the immune system by antigens. However, their efficacy has been limited by the inability of antigens delivery, which are the core components of vaccines, further fail to be presented and activation of effective cells. Nanotechnology offers a novel platform to enhance the immunogenicity of tumor-associated antigens and deliver them to antigen-presenting cells (APCs) more efficiently. In addition, nanotreatment of tumor cells derivate active ingredients could also help improve the effectiveness of cancer vaccines. In this review, we summarize recent advances in the development of cancer vaccines by the combination of nanotechnology and tumor-based ingredients, including liposomes, polymeric nanoparticles, metallic nanoparticles, virus-like particles and tumor cells membrane, tumor lysate, and specific tumor antigens. These nanovaccines have been designed to increase antigen uptake, prolong antigen presentation, and modulate immune responses through codelivery of immunostimulatory agents. We also further discuss challenges and opportunities in the clinical translation of these nanovaccines.

Introduction

Cancer immunotherapy has revolutionized cancer treatment by harnessing the immune system to recognize and attack cancer cells [1–3]. Among various immunotherapeutic approaches, cancer vaccines have attracted significant attention due to their potential to induce long-lasting and specific immune responses against tumor cells [4–7]. By comparison with surgery, it hardly produce large wounds, nor does it cause higher toxicity in normal tissues and drug tolerance like chemotherapy in the treatment of tumor. However, the clinical efficacy of cancer vaccines based on tumor cell components, such as peptides and proteins, is limited by their poor immunogenicity and inefficient delivery to antigen presentation cells (APCs). Although, many cancer vaccines were applied with the immune-stimulatory agents, such as the programmed cell death protein 1 (PD-1), CpG oligonucleotide, etc. The clinical response rates remain low, especially in the hypoimmunogenic tumors. As we all know, pancreatic cancer is a more difficult type for immunotherapy as a low immunogenic tumor. Therefore, there are few effective cancer vaccines that can actively promote the pancreatic cancer treatment. Meanwhile, limited by the specific tumor antigens, the development of cancer vaccines was extremely difficult.

The field of cancer vaccines has seen significant advancements in recent years, with numerous studies focusing on different aspects of vaccine development and application [8–12]. These advances have been facilitated by the exploration of various types of cancer vaccines, including those targeting viral antigens, neoantigens, and other tumor-specific antigens [13–16]. One approach in cancer vaccine research involves targeting shared antigens from viral infections linked to certain cancer types, such as Epstein–Barr virus and HPV. Studies have shown promising results with vaccines targeting viral antigens like Epstein–Barr nuclear antigen 1 and latent membrane proteins, as well as HPV-related antigens, demonstrating favorable antitumor efficacy and the potential to establish durable T cell memory in rapidly progressing HPV-positive tumors [17]. Another significant area of research is neoantigen cancer vaccines. Neoantigens, derived from nonsynonymous cell variants, are only expressed in tumor cells and can bypass thymus-negative selection, leading to robust neoantigen-specific T cell responses [14]. Advances in genomic and transcriptional profiling have made identifying putative neoantigens possible, although challenges remain in predicting which neoantigens can effectively induce neoantigen-specific T cell responses [18–20]. Cancer vaccines are being developed to stimulate antitumor immunity with tumor antigens delivered in various forms, such as cells, peptides, viruses, and nucleic acids [21–24]. These vaccines aim to overcome tumor heterogeneity and reverse the immunosuppressive microenvironment. Challenges in the field include single antigen targeting, weak immunogenicity, off-target effects, and impaired immune response [25–27]. Current research and reviews provide insights into the principle of action, components, classification, delivery methods, and progress of cancer vaccines, offering a broader perspective for future vaccine design.

Recent studies have shown that tumor antigens can be used for the design of cancer vaccines without the necessity to identify, parse, and reconstruct certain antigens [28–31]. A novel concept has been proposed that the whole antigen vaccine systems derived from tumor cells could be designed to conquer cancer treatments [32–34]. The tumor cells themselves are a huge antigen pool with countless tumor antigen epitopes, which can be used to activate antitumor immune response. Among them, more studies have focused on the application of tumor cell membrane as tumor antigens to stimulate APCs and further activate the antitumor immune response of T cells. In addition, the activation of T cells in immune response requires the involvement of costimulatory molecules. Some studies are based on this theoretical foundation, using genetic engineering to modify tumor cell membranes. By retaining antigen on the cell membrane and inducing the expression of costimulatory molecule CD80, T cells can be directly activated, thereby achieving antitumor immune response [35] (Figure 1). Of course, many studies combine tumor cell membranes that retain tumor antigens with other functional molecules to directly activate dendritic cells (DCs) for antigen presentation, leading to the activation of T cell immune response. These are two different approaches aimed at achieving the same goal [36–38]. A series of nanovaccines developed on this basis have been widely used in the treatment of different tumor cells and preclinical experiments.

Introduction

Tumor microenvironment (TME) is a complex network of cancer cells and various other cellular and noncellular components. Microorganisms such as bacteria, viruses, fungi, phages, and protozoa naturally occur in the TME, modulating the metabolic composition and promoting or inhibiting tumorigenesis. In the last decades, a growing interest has emerged in microorganisms in the TME and their potential applications for cancer therapy 1, 2.

Bacterial and viral infections have been long associated with cancer development and have been used in cancer therapy decades ago. Bacteria have various effects on cancer cells through different modes of action, for instance, depending on the strain, tissue, and environment 1, 2. Viruses also naturally occur in the TME, and some strains promote cancer growth, such as the human papillomavirus (HPV) [3], while others have oncolytic activity, such as the influenza A virus (IAV) [4]. The different mechanisms through which bacteria and viruses affect tumor proliferation and metastasis include altering immune responses 5, 6, 7•, secreting cytotoxic molecules such as formate or colibactine 8••, 9, and alterations of metabolic and signaling pathways 8••, 10. The natural abilities of microorganisms to colonize and alter the TME can also be used for cancer detection and therapy with the help of engineered bacteria and viruses 2, 11, 12. However, the metabolic interactions among viruses, bacteria, cancer cells, and TME are not well understood. Metabolites function as signaling molecules, and we are just beginning to understand the functional role of small molecules within the TME 13, 14, 15. For instance, the immunometabolite itaconate has antimicrobial properties but may also affect tumor progression by altering cancer cell metabolism or the composition of the TME 16, 17•, 18, 19. Thus, further research is needed to identify the key players within the TME that affect immune responses and tumor progression.

Approaches in virotherapy

Virotherapy aims to transform the ‘cold’ immunosuppressive TME, characterized by high levels of TAMs, T-regulatory cells (Tregs), MDSCs, and activated M2-like macrophages, into a ‘hot’ immunoreactive TME (Figure 3). This transformation involves the recruitment of, for instance, NKs, DCs, and M1-like macrophages (Figure 3). OV administration targets different approaches in cancer therapies, such as making the virus dependent on specific genes within the cancer host cell to enable selective replication in malignant cells, followed by direct lysis. Furthermore, it is applied to deliver specific antibodies to inhibit tumor growth [45]. For instance, the recombinant human type-5 adenovirus (Ad5) selectively replicates in tumor cells with p53-defective influencing cancer cell growth [46]. OVs may also indirectly affect the TME and tumor growth by inducing the release of cytokines, such as interferon (IFN), damage-associated molecular patterns (DAMPs), high mobility group box 1 protein (HMGB1), or pathogen-associated molecular patterns (PAMPs) 41, 47, leading to further recruiting and activation of the innate and adaptive immune system, including DCs (Figure 3). DCs play an elementary role in connecting both immune systems and are infrequently present in the cold TME. These findings highlight various targets that can be used to modulate the immune response in the TME through OVs, aiming to constrain tumor growth and increase patient outcomes.

Conclusion

Bacterial and viral infections play a vital role in altering the composition of the TME, thus influencing its potential as pro- or anti-tumorigenic. Many bacteria and viruses influence TME, for instance, by secreting signal molecules, altering specific immune responses, causing DNA damage, or inducing metabolic rewiring. While promising approaches utilizing bacteria and viruses for cancer detection and therapy exist, how infections influence metabolism to promote either pro- or antitumor properties is still not well understood. Engineered bacteria and viruses could be optimized to work effectively against cancer with potentially less off-target effects compared with conventional therapies. For example, altering levels of cytokines or metabolites such as itaconate or arginine in the TME may promote an anticancer immune response, either alone or in combination with existing treatments. Expanding our current knowledge of the complex interaction of microorganisms and cancer cells will provide us with effective ways to develop new treatment strategies.

Abstract

Several microRNAs (miRNAs), including miR-23 and miR-27a have been reportedly involved in regulating myelination in the central nervous system. Although miR-23 and miR-27a form clusters in vivo and the clustered miRNAs are known to perform complementary functions, the role of these miRNA clusters in myelination has not been studied. To investigate the role of miR-23-27-24 clusters in myelination, we generated miR-23-27-24 cluster knockout mice and evaluated myelination in the brain and spinal cord. Our results showed that 10-week-old knockout mice had reduced motor function in the hanging wire test compared to the wild-type mice. At 4 weeks, 10 weeks, and 12 months of age, knockout mice showed reduced myelination compared to wild-type mice. The expression levels of myelin basic protein and myelin proteolipid protein were also significantly lower in the knockout mice compared to the wild-type mice. Although differentiation of oligodendrocyte progenitor cells to oligodendrocytes was not inhibited in the knockout mice, the percentage of oligodendrocytes expressing myelin basic protein was significantly lower in 4-week-old knockout mice than that in wild-type mice. Proteome analysis and western blotting showed increased expression of leucine-zipper-like transcription regulator 1 (LZTR1) and decreased expression of R-RAS and phosphorylated extracellular signal-regulated kinase 1/2 (pERK1/2) in the knockout mice. In summary, loss of miR-23-27-24 clusters reduces myelination and compromises motor functions in mice. Further, LZTR1, which regulates R-RAS upstream of the ERK1/2 pathway, a signal that promotes myelination, has been identified as a novel target of the miR-23-27-24 cluster in this study.

Introduction

In the central nervous system (CNS), myelin, produced by oligodendrocytes, supports axonal metabolism and allows for rapid transmission of action potentials along axons [1–3]. In demyelinating conditions such as multiple sclerosis or spinal cord injury, myelin is lost and axons degenerate, resulting in permanent loss of function. Remyelination in these demyelinating conditions remains a challenge. Developmental myelination and remyelination have the common goal of attaching myelin sheaths to axons [4]. In addition, there is a common mechanism underlying developmental myelination and remyelination, and remyelination is considered as “rerunning” of myelination [4]. Therefore, understanding the mechanism underlying myelination will help in developing novel strategies for remyelination in various disease conditions. Normal myelination is a multistep process in which oligodendrocyte differentiation and initiation of myelination are tightly regulated [5]. Previous studies have shown that several genes, transcription factors, and pathways are involved in oligodendrocyte progenitor cell (OPC) proliferation and oligodendrocyte differentiation, maturation, and myelination [6–8]. Furthermore, recent studies have shown that microribonucleic acids (miRNAs) play important roles in regulating myelination [9–15].

Results

3.1. Expression of the miR-23-27-24 Cluster in the CNS
KO mice were slightly smaller than wild-type mice but were born and grew without morphological abnormalities (Figure 1(a)). Compared to 10-week-old wild-type mice, the expression of all miRNAs in the miR-23-27-24 cluster was significantly lower in the KO mice, both in the spinal cord and brain () (Figures 1(b) and 1(c) and Table 1).

Next, we compared the expression of the miR-23-27-24 cluster in the spinal cord of mice at different ages (4 weeks, 10 weeks, and 12 months of age). For all miRNAs in the miR-23-27-24 cluster, the expression levels in 10- and 12- week-old wild-type mice were significantly higher than those in 4-week-old wild-type mice (p < 0:001) (Figure 2). The expression of miR-23a in 12-month-old wild-type mice was significantly lower than that in 10-week-old wild-type mice (p < 0:001) (Figure 2(a)), but there were no significant differences in the expression of other miRNAs (Figures 2(b)–2(e)). The expression of all miRNAs in KO mice was significantly lower than that in wild-type mice at all ages (Table 2).

Abstract

Objective. Mesenchymal stem cell (MSC) therapy has been explored in Huntington disease (HD) as a potential therapeutic approach; however, a complete synthesis of these results is lacking. We conducted a meta-analysis to evaluate the effects of MSCs on HD. Method. Eligible studies published before November 2022 were screened from Embase, PubMed, Web of Science, Medline, and Cochrane in accordance with PRISMA guidelines. ClinicalTrial.gov and the World Health Organization International Clinical Trials Registry Platform were also searched for registered clinical trials. The outcomes in rodent studies evaluated included morphological changes (striatal volume and ventricular volume), motor function (rotarod test, wire hang test, grip strength test, limb-clasping test, apomorphine-induced rotation test, and neuromuscular electromyography activity), cognition (Morris water maze test), and body weight. Result. The initial search returned 362 records, of which 15 studies incorporating 346 HD rodents were eligible for meta-analysis. Larger striatal and smaller ventricular volumes were observed in MSC-treated animals compared to controls. MSCs transplanted before the occurrence of motor dysfunction rescued the motor incoordination of HD. Among different MSC sources, bone marrow mesenchymal stem cells were the most investigated cells and were effective in improving motor coordination. MSC therapy improved muscle strength, neuromuscular electromyography activity, cortex-related motor function, and striatum-related motor function, while cognition was not changed. The body weight of male HD rodents increased after MSC transplantation, while that of females was not affected. Conclusion. Meta-analysis showed a positive effect of MSCs on HD rodents overall, as reflected in morphological changes, motor coordination, muscle strength, neuromuscular electromyography activity, cortex-related motor function, and striatum-related motor function, while cognition was not changed by MSC therapy.

Introduction

Huntington disease (HD) is a neurodegenerative disorder of the central nervous system resulting from a dominantly inherited CAG trinucleotide repeat expansion in exon 1 of the huntingtin (HTT) gene that encodes the Huntingtin protein [1]. Pathological changes are characterized by a general shrinkage of the brain and distinct degeneration of the striatum (caudate nucleus and putamen) [2]. Although HD prevalence is only 4-10 individuals per 100,000, it seriously affects the life quality of the patients in many ways, including movement, cognition, and psychological condition, as well as other functional disabilities [3]. Motor defects typically include chorea and loss of coordination. Psychiatric symptoms, such as depression, psychosis, and obsessive-compulsive disorder, are common in HD [4]. Death typically occurs about 20 years after symptom onset [1].

Current therapies for HD are directed at symptom relief, as there are no any disease-modifying therapies. Therapeutic attempts based on pathogenic mechanisms including gene silencing [5], antiapoptosis/caspase inhibition [6], transglutaminase inhibition [7], antioxidative stress [8], upregulating autophagy [9], and physical exercise [10] have been investigated; unfortunately, none of these have met the criteria for clinical translation. For instance, silencing the expression of the mutant HTT gene is attractive; however, allele specificity and off-target effects are not fully resolved. Treatment of mouse models with antioxidants was considered to be beneficial [8], whereas trials of creatine for symptomatic patients were disappointing [11].

Conclusion

This meta-analysis reveals MSC therapy attenuates morphological changes and improves motor function in HD models, but cognition was not influenced. Furthermore, the weight of male, but not female, HD rodents may be benefited from MSC treatment. These results support MSC-based strategies becoming an alternative treatment for HD; however, before MSC therapies can be translated into clinical practice, their safety, efficacy, and mechanism must be established with more preclinical and clinical studies.

Summary

β-arrestin plays a key role in G protein-coupled receptor (GPCR) signaling and desensitization. Despite recent structural advances, the mechanisms that govern receptor-β-arrestin interactions at the plasma membrane of living cells remain elusive. Here, we combine single-molecule microscopy with molecular dynamics simulations to dissect the complex sequence of events involved in β-arrestin interactions with both receptors and the lipid bilayer. Unexpectedly, our results reveal that β-arrestin spontaneously inserts into the lipid bilayer and transiently interacts with receptors via lateral diffusion on the plasma membrane. Moreover, they indicate that, following receptor interaction, the plasma membrane stabilizes β-arrestin in a longer-lived, membrane-bound state, allowing it to diffuse to clathrin-coated pits separately from the activating receptor. These results expand our current understanding of β-arrestin function at the plasma membrane, revealing a critical role for β-arrestin preassociation with the lipid bilayer in facilitating its interactions with receptors and subsequent activation.

Introduction

G protein-coupled receptors (GPCRs) are implicated in virtually every physiological process and are major drug targets.1,2 Following agonist-mediated GPCR activation and phosphorylation by G protein-coupled-receptor kinases (GRKs), β-arrestins translocate from the cytosol to bind agonist-occupied, phosphorylated receptors on the plasma membrane. There are four arrestins—two visual arrestins (also known as arrestin 1 and 4), β-arrestin 1 (βArr1) (arrestin 2), and β-arrestin 2 (βArr2) (arrestin 3).

By interacting with the receptor core, β-arrestins mediate rapid signal desensitization.3 In addition, β-arrestins trigger receptor internalization via interaction with the adaptor protein 2 (AP2) and clathrin heavy chain.4 Moreover, β-arrestins have been proposed to mediate “non-classical” G protein-independent effects,5 providing a mechanism for “biased” signaling.6 This diversity of functions has been linked to multiple conformations in receptor-arrestin complexes revealed by structural and biophysical studies with purified proteins.7,8,9,10,11,12,13,14,15,16,17 Furthermore, recent findings of prolonged β-arrestin activation18,19,20 suggest that β-arrestin signaling might be more complex than previously thought. However, how this complexity operates on the plasma membrane of living cells remains largely unknown.

Here, we combined an innovative multicolor single-molecule microscopy approach21,22 with molecular dynamics (MD) simulations to dissect the sequence of events in receptor-β-arrestin interactions at the plasma membrane of living cells with ∼20 nm spatial and 30 ms temporal resolution.21,22 Our results reveal that β-arrestin binds directly to the lipid bilayer, allowing it to transiently interact with receptors via lateral diffusion, and reaches clathrin-coated pits (CCPs) separately from the activating receptor.

Results

Single-molecule imaging reveals spontaneous membrane translocation and lateral diffusion of βArr2
As a main model, we chose βArr2 and the β2-adrenergic receptor (β2AR), a prototypical family-A GPCR that regulates numerous physiological processes.23,24 To investigate the behavior of individual βArr2 and β2AR molecules on the plasma membrane of living cells, we labeled them with two distinct organic fluorophores via fusion of Halo25 and SNAP26 tags to their C and N termini, respectively (Figure 1A). Both constructs were transiently expressed at low physiological levels in Chinese hamster ovary (CHO) cells, which have no detectable β1AR/β2AR.27 Both βArr2-Halo and SNAP-β2AR constructs are functional; βArr2-Halo binds receptors and mediates receptor internalization to a similar extent as wild-type (WT) βArr2, and co-localizes with internalized receptors in endosomes (Figures S1A–S1D; see STAR Methods for details). CHO cells were then labeled with saturating concentrations of both organic fluorophores (Figure S1E) and were simultaneously imaged by fast multicolor total internal reflection fluorescence (TIRF) microscopy combined with single-particle tracking22 (Figure 1B; Videos S1 and S2); unspecific labeling was <1% (Figure S1F). We additionally visualized CCPs by co-transfection of GFP-labeled clathrin light chain. Data were acquired both under basal conditions and after early (2–7 min) and late (8–15 min) stimulation with the β-adrenergic full agonist isoproterenol (Iso). An excess of 5.8 million individual molecular trajectories were acquired and analyzed in this study. Numbers of trajectories and particle densities in the analyzed groups are given in Table S1.

Highlights

Abstract

Graphical abstract

Abbreviations

Keywords

1. Introduction

2. De novo identification of mitochondrial proteins

2.1. In silico strategies

2.2. Experimental strategies

2.3. Integrative biology strategies

3. From proteins to functions: deorphanizing the unknown

3.1. In silico strategies

3.2. Experimental strategies

4. Perspectives

CRediT authorship contribution statement

Declaration of Competing Interest

Acknowledgments

References

Abstract

Human mitochondria are complex and highly dynamic biological systems, comprised of over a thousand parts and evolved to fully integrate into the specialized intracellular signaling networks and metabolic requirements of each cell and organ. Over the last two decades, several complementary, top-down computational and experimental approaches have been developed to identify, characterize and modulate the human mitochondrial system, demonstrating the power of integrating classical reductionist and discovery-driven analyses in order to de-orphanize hitherto unknown molecular components of mitochondrial machineries and pathways. To this goal, systematic, multiomics-based surveys of proteome composition, protein networks, and phenotype-to-pathway associations at the tissue, cell and organellar level have been largely exploited to predict the full complement of mitochondrial proteins and their functional interactions, therefore catalyzing data-driven hypotheses. Collectively, these multidisciplinary and integrative research approaches hold the potential to propel our understanding of mitochondrial biology and provide a systems-level framework to unraveling mitochondria-mediated and disease-spanning pathomechanisms.

1. Introduction

Mitochondria are essential organelles for cellular and organismal life in virtually all eukaryotes (Fig. 1). Present-day human mitochondria originated from the integration of an endosymbiotic α-proteobacterium into a host cell, therefore exchanging their independence for a semi-autonomous life [1,2]. By the late 1990s, comparative genomics analyses of α-proteobacteria genomes and quantitative two-dimensional gels of highly purified mitochondria suggested that the mammalian mitochondrial proteome consists of ∼1,000–1,500 distinct proteins [3,4]. The majority of those proteins derive from the eukaryotic genome, whereas the prokaryotic genome was significantly reduced during the transition from endosymbiotic bacterium to organelle [2] (Fig. 2A). To date, only a handful of protein-coding genes – thirteen in mammals – are still retained in the mitochondrial DNA (mt-DNA) of almost all eukaryotes. Therefore, most of the mitochondrial proteome is encoded from the nuclear genome, translated in the cytosol, and then targeted and imported into the organelle.

Strikingly, only 1% of mammalian mitochondrial proteins are allocated to ATP synthesis, highlighting that the organelle’s functions reach far beyond energy production (Fig. 1). Indeed, mitochondria are at the core of multiple cellular pathways, including the biosynthesis of precursors for cholesterol, estrogen, testosterone and hemoglobin; the regulation of redox and ion homeostasis; the activation of antiviral responses and cell death. Adding an additional layer of complexity, mitochondrial functions are tied to the specialized tasks and physiology of different cell types, tissues, and organisms [5]. For instance, only between 40–70 % of the human mitochondrial proteome is conserved in commonly used model systems such as unicellular eukaryotes (e.g. S. cerevisiae) and invertebrates (e.g. C. elegans, D. melanogaster) (Fig. 2B). Furthermore, over 15 % of the mitochondrial system shows tissue-specificity [6] and profound differences even among cell types of the same tissue [6,7].

Abstract

Keywords

1. Introduction

2. What is life?

3. What is a virus?

4. Do any virus-like systems achieve closure to efficient causation?

5. Conclusion

Declaration of Competing Interest

Acknowledgements

Appendix A. Supplementary data

References

Abstract

Whether or not viruses are alive remains unsettled. Discoveries of giant viruses with translational genes and large genomes have kept the debate active. Here, a fresh approach is introduced, based on the organisational definition of life from within systems biology. It views living as a circular process of self-organisation and self-construction which is ‘closed to efficient causation’. How information combines with force to fabricate and organise environmentally obtained materials, given an energy source, is here explained as a physical embodiment of informational constraint. Comparing a general virus replication cycle with Rosen’s -system shows it to be linear, rather than closed. Some viruses contribute considerable organisational information, but so far none is known to supply all required, nor the material nor energy necessary to complete their replication cycle. As a result, no known virus replication cycle is closed to efficient causation: unlike cellular obligate parasites, viruses do not match the causal structure of an -system. Analysis based in identifying a Markov blanket in causal structure proved inconclusive, but using Integrated Information Theory on a Boolean representation, it was possible to show that the causal structure of a virocell is not different from that of the host cell.

Introduction

The first half of 2020 has seen one particular virus (SARS-Cov2) dominate world news, so much that viruses appear to be at the forefront of public interest in biological research and in this context an old debate has reemerged: “Are viruses alive?”. According to an informal survey (Racaniello, 2014), expert opinion remains divided roughly a third each between yes, no and don’t know. This is not surprising given that the debate seems still to be resolved. Eleven years ago, an emphatic statement was made against including viruses among the living (Moreira and Lopez-Garcia, 2009), quickly countered by (sometimes indignant) responses of matching boldness (Claverie and Ogata (2009); Hegde et al. (2009)) and more nuanced responses (e.g. Forterre (2010b)). The discovery of giant viruses(Raoult and Forterre, 2008; Abergel et al., 2015; Claverie and Abergel, 2018), especially the Pandoraviruses, having genome sizes reaching that of parasitic eukaryotes (Nad`ege et al., 2013) and Tupanviruses with their batteries of translational genes (Abrah˜ao and et al., 2018; Rodrigues et al., 2020) has further stirred the debate (e.g. Claverie and Abergel (2010); Abergel et al. (2015); Brandes and Linial (2019)). It also attracted philosophers of science who having analysed the debate, concluded that it is misguided (van Regenmortel, 2016; Koonin and Starokadomskyy, 2016). Whether or not viruses belong within the category of living has again become highly topical and contentious.

1- Introduction

2- In vitro studies

3- In vivo studies

4- Conclusion(s)

References

Abstract

Stem cell, one of the most exciting research areas of 21st century, is considered to have broaden the horizons of the field of biology, in general and medicine, in particular. Stem cells, owing to their unique characteristics like self-renewal, multiplication and differentiation are considered to provide an ‘all-in-one-solution’ for diverse clinical problems. Among various stem cell types, mesenchymal stem cells (MSCs) are being made the subject of the most of the studies on their therapeutic applications. It is attributable to their readily available sources, ability to immunemodulate and differentiate into mesodermal and extra-mesodermal tissues. MSCs in contrast to pluripotent stem cells carry minimal risk of teratoma formation and are free from any ethical concern. MSCs have been evaluated under innumerable studies but the definitive applications of these cells are slow, plausibly due to the incomplete understanding of their cellular physiology. Goat MSCs (gMSCs) have been isolated, culture expanded, characterized from various tissue sources and studied for their potential in vivo applications mostly in relation to human translational models. The current review throws some light on gMSC sources, characterization and potential therapeutic applications.

Introduction

The stem cells constitute an important element in the discipline of regenerative medicine that aims to address numerous incurable diseases through tissue regeneration (Gugjoo and Amarpal, 2018; Gugjoo et al. 2019). The specialized properties of selfrenewal, multiplication and differentiation of stem cells make them potential candidates for an all-in-one therapeutic solution to diverse clinical ailments. Among various stem cell types, mesenchymal stem cells (MSCs) make subject of most of the therapeutic applications (Gugjoo et al. 2019). MSCs are available in almost all the tissue types and have easy isolation and culture processes. The cells are plastic in nature, and have immunomodulatory and/ anti-inflammatory properties with minimal risk of teratogenicity and associated ethical issues unlike that of embryonic stem cells (Song et al. 2013; Gugjoo et al. 2019).

Introduction

Materials and Methods

Results and Discussion

Conclusions

References

ABSTRACT

RNA molecules perform a variety of biological functions for which the correct three-dimensional structure is essential, including as ribozymes where they catalyze chemical reactions. Metal ions, especially Mg2þ, neutralize these negatively charged nucleic acids and specifically stabilize RNA tertiary structures as well as impact the folding landscape of RNAs as they assume their tertiary structures. Specific binding sites of Mg2þ in folded conformations of RNA have been studied extensively; however, the full range of interactions of the ion with compact intermediates and unfolded states of RNA is challenging to investigate, and the atomic details of the mechanism by which the ion facilitates tertiary structure formation is not fully known. Here, umbrella sampling combined with oscillating chemical potential Grand Canonical Monte Carlo/molecular dynamics simulations are used to capture the energetics and atomic-level details of Mg2þ-RNA interactions that occur along an unfolding pathway of the Twister ribozyme. The free energy profiles reveal stabilization of partially unfolded states by Mg2þ, as observed in unfolding experiments, with this stabilization being due to increased sampling of simultaneous interactions of Mg2þ with two or more nonsequential phosphate groups. Notably, these results indicate a push-pull mechanism in which the Mg2þ-RNA interactions actually lead to destabilization of specific nonsequential phosphate-phosphate interactions (i.e., pushed apart), whereas other interactions are stabilized (i.e., pulled together), a balance that stabilizes unfolded states and facilitates the folding of Twister, including the formation of hydrogen bonds associated with the tertiary structure. This study establishes a better understanding of how Mg2þ-ion interactions contribute to RNA structural properties and stability.

INTRODUCTION

RNA molecules have highly diverse structures ranging from simple helices to highly heterogeneous folded conformations that are essential for their wide range of cellular functions (1–3). Specifically, ribozymes, a distinct class of enzymes, exhibit complex tertiary structures and catalyze self-cleavage or the cleavage of phosphodiester bonds of substrate RNA, with metal ions typically playing a central role in the catalytic activity (4–6). To assume their tertiary structures, RNAs must overcome large unfavorable electrostatic interactions associated with their polyanionic phosphodiester backbone (7). To facilitate this, positively charged ions screen the highly negative potential, allowing the RNA secondary structures to collapse into compact tertiary conformations (8–11). Typically divalent ions, most often Mg2þ, facilitate the formation of tertiary interactions required for the full folding of RNA (12–14). However, the inability to visualize the ions during folding represents a key barrier to understanding the role of divalent ions in folding of RNA (15). Studies have used classical molecular dynamics (MD) or other theoretical approaches to investigate Mg2þ-RNA binding, but they were limited to native conformations because of their inability to overcome the issues associated with the Mg2þ exchange rates (16–22). The exchange rate of water complexed to Mg2þ is on the ms timescale (6.7 105 s 1 ), and the exchange rate of Mg2þ with phosphate is on the ms timescale (0.5–2.5 103 s 1 ) (23), which is beyond the timescale of typical atomistic MD simulations (20,24) such that only limited insights into Mg2þ-RNA interactions are accessible (25). Alternatively, simulations using coarse-grained models of nucleic acids provided insights into how Mg2þ can serve to nucleate the folding of key tertiary interactions with the Mg2þ-RNA interactions being dominated by specific interactions even in unfolded states (19,26).

1- Introduction

2- Mesenchymal stem cells: an overview

3- Engineered MSCs

4- Engineered oncolytic viruses

5- Immune checkpoint inhibitors and oncolytic therapy

6- Non-systemic anticancer therapy with oncolytic virus-loaded MSCs

7- Systemic anticancer therapy with oncolytic virus-loaded MSCs

8- Limitations of MSC use in systemic therapy

9- MSC-mediated oncolytic virotherapy – clinical studies

10- Future directions

References

Abstract 

Progress in genetic engineering led to the emergence of some viruses as potent anticancer therapeutics. These oncolytic viruses combine self-amplification with dual antitumor action: oncolytic (destruction of cancer cells) and immunostimulatory (eliciting acquired antitumor response against cancer epitopes). As any other viruses, they trigger antiviral response upon systemic administration. Mesenchymal stem cells are immature cells capable of self-renewing and differentiating into many cell types that belong to three germinal layers. Due to their inherent tumor tropism mesenchymal stem cells loaded with oncolytic virus can improve delivery of the therapeutic cargo to cancer sites. Shielding of oncolytic viral construct from antiviral host immune response makes these cells prospective delivery vehicles to even hard-to-reach metastatic neoplastic foci. Use of mesenchymal stem cells has been criticized by some investigators as limiting proliferative abilities of primary cells and increasing the risk of malignant transformation, as well as attenuating therapeutic responses. However, majority of preclinical studies indicate safety and efficacy of mesenchymal stem cells used as carriers of oncolytic viruses. In view of contradictory postulates, the debate continues. The review discusses mesenchymal stem cells as carriers for delivery of genetically engineered oncolytic constructs and focuses on systemic approach to oncoviral treatment of some deadly neoplasms.

Introduction

Despite unquestionable progress in cancer treatment, several malignancies still tend to elude successful cure or medically-induced remission. Continued rise in morbidity in the last twenty years for gliomas, melanoma or pancreatic cancer makes them a major public health concern and a research challenge. Although radically improved outcomes might be unattainable yet, stepwise progress is likely with novel or improved treatments involving immunotherapy, cell-based therapeutics, oncolytic virotherapy and hybrid approaches. Intriguing recoveries from cancer following natural viral infection (e.g. measles) have been known to medicine since early 20th century but this early lead based on use of wild-type adenovirus, poliovirus or Coxsackie virus was marred by virus-associated morbidity and complications and was later abandoned (Kelly et al., 2007). Clinical utility of oncolytic viruses has been steadily regaining ground since the latter part of the 20th century with advances in genetic engineering. Current generation of many oncolytic viral constructs allows targeting and destroying cancer cells while toxicities to surrounding normal tissues are minimized. A concurrent development in cell-based anticancer therapies has led to the concept of oncoviral viruses’ delivery to tumors via cellular carriers. It assumes that certain types of cells pre-loaded ex vivo with some curative cargo can be administered systemically, delivered to and released in target tissues.