Intratumoral injection of Clostridium novyi-NT spores induces antitumor responses

The impact of tumor and gut microbiotas on cancer therapy: Beneficial or detrimental?

Cancer is a globally challenging health problem threatening mankind. Despite therapeutic advances in dealing with this malignancy, heterogeneous response and resistance to chemotherapeutic agents remain the hallmarks of cancer therapy. On the other hand, the involvement of the microbiota in affecting human health is well defined. An ever-growing body of evidence implicates the potential link between the microbiome and the efficacy of cancer therapies. Gut microbiota can modulate the metabolism of drugs in a number of ways. The presence of bacteria within the tumor environment can also impact the responses to cancer therapies; changing the chemical structure of chemotherapeutic drugs, affecting their activity, and local concentration. However, the underlying mechanisms by which gut and tumor microbial communities affect the response to cancer therapy are poorly understood and deciphering these mechanisms is of paramount importance. This review provides an overview of how gut and tumor microbiota might affect the efficacy of chemotherapy, radiotherapy, and immunotherapy and alleviate the adverse side effects of these therapies for the development of personalized and effective anticancer therapy.

Nontyphoidal Salmonella: a potential anticancer agent

Use of bacteria in cancer therapy, despite being considered as a potent strategy, has not really picked up the way other methods of cancer therapies have evolved. However, in recent years, the interest on use of bacteria to kill cancer cells has renewed considerably. The standard and widely followed strategies of cancer treatment often fail either due to the complexity of tumour biology or because of the accompanying side effects. In contrast, these limitations can be easily overcome in a bacteria-mediated approach. Salmonella is a bacterium, which is known for its ability to colonize solid or semisolid tumours more efficiently than any other bacteria. Among more than 2500 serovars of Salmonella, S. Typhimurium has been widely studied for its antagonistic effects on cancer cells. Here in, we review the current status of the preclinical and the clinical studies with a focus on the mechanisms that attribute the anticancer properties to nontyphoidal Salmonella.

The Dosage of the Derivative of Clostridium Ghonii (DCG) Spores Dictates Whether an IFNγ/IL-9 or a Strong IFNγ Response Is Elicited in TC-1 Tumour Bearing Mice

Background

Anaerobic Clostridial spores (CG) cause significant oncolysis in hypoxic tumour microenvironment and result in tumour regression in both animal models and clinical trials. The immune mediated response plays a critical role in the antitumour effect by the anaerobic spore treatment.

Method

Human papillomavirus 16 E6/E7 transformed TC-1 tumour bearing mice were intravenously administered with low (1 × 10⁸ CFU/kg) or high dosage (3 × 10⁸ CFU/kg) of Derivative Clostridial spore (DCG).

Results

Intravenous administration of the derivative of Clostridial ghonii (DCG) spores leads to both tumour and systemic inflammatory responses characterized by increased IFNγ/IL-9 secreting T cells in the spleen and the tumour. Low numbers of antigen specific T cells (<20/10⁶ spleen cells) in the spleen of the tumour bearing mice are also detected after intravenous DCG delivery. Interestingly, our results showed that a mixed IL-9/IFNγ secreting T cell response was induced when the tumour bearing mice received a low dose of DCG spore (1 × 10⁸ CFU/kg), while a strong IFNγ response was elicited with a high dosage of DCG spore (3 × 10⁸ CFU/kg).

Conclusion

The dosage of DCG spore will determine the types of the DCG induced immune responses.

Ascorbic acid induced HepG2 cells' apoptosis via intracellular reductive stress

Goals: Destruction of the redox balance in tumor cells is of great significance for triggering their apoptosis in clinical applications. We designed a pH sensitive multifunctional drug nanocarrier with controllable release of ascorbic acid under hypoxic environment to induce tumor cells' apoptosis via enhancing reductive stress, thereby dealing minimum damage to normal tissues. Methods: A core-shell nanostructure of CdTe quantum dots with mesoporous silica coating was developed and functionalized with poly(2-vinylpyridine)-polyethylene glycol-folic acid, which achieves cancer cells' targeting delivery and reversibly pH controlled release of ascorbic acid both in vitro and in vivo. Results: The result demonstrated that ascorbic acid can indeed lead liver cancer cells' death with the increase of nicotinamide adenine dinucleotide phosphate, while normal cells not being affected. The molecular mechanism of apoptosis induced by ascorbic acid was firstly elucidated at cellular levels, and further confirmed via in vivo investigations. Conclusion: For the first time we proposed the concept for applying reductive stress into cancer treatments, which brings great advantage of toxicity free and less damage to normal tissues. In general, this technique has taken an important step in the development of a targeted tumor treatment system, providing perspectives for the design of medicines via reductive stress, and offers new insights into future clinical mild-therapies.

Strategies for developing and optimizing cancer vaccines

With the spotlight on cancer immunotherapy and the expanding use of immune checkpoint inhibitors, strategies to improve the response rate and duration of current cancer immunotherapeutics are highly sought. In that sense, investigators around the globe have been putting spurs on the development of effective cancer vaccines in humans after decades of efforts that led to limited clinical success. In more than three decades of research in pursuit of targeted and personalized immunotherapy, several platforms have been incorporated into the list of cancer vaccines from live viral or bacterial agents harboring antigens to synthetic peptides with the hope of stronger and durable immune responses that will tackle cancers better. Unlike adoptive cell therapy, cancer vaccines can take advantage of using a patient's entire immune system that can include more than engineered receptors or ligands in developing antigen-specific responses. Advances in molecular technology also secured the use of genetically modified genes or proteins of interest to enhance the chance of stronger immune responses. The formulation of vaccines to increase chances of immune recognition such as nanoparticles for peptide delivery is another area of great interest. Studies indicate that cancer vaccines alone may elicit tumor-specific cellular or humoral responses in immunologic assays and even regression or shrinkage of the cancer in select trials, but novel strategies, especially in combination with other cancer therapies, are under study and are likely to be critical to achieve and optimize reliable objective responses and survival benefit. In this review, cancer vaccine platforms with different approaches to deliver tumor antigens and boost immunity are discussed with the intention of summarizing what we know and what we need to improve in the clinical trial setting.

Bacteria in Cancer Therapeutics: A Framework for Effective Therapeutic Bacterial Screening and Identification

By 2030, the global incidence of cancer is expected to increase by approximately 50%. However, most conventional therapies still lack cancer selectivity, which can have severe unintended side effects on healthy body tissue. Despite being an unconventional and contentious therapy, the last two decades have seen a significant renaissance of bacterium-mediated cancer therapy (BMCT). Although promising, most present-day therapeutic bacterial candidates have not shown satisfactory efficacy, effectiveness, or safety. Furthermore, therapeutic bacterial candidates are available to only a few of the approximately 200 existing cancer types. Excitingly, the recent surge in BMCT has piqued the interest of non-BMCT microbiologists. To help advance these interests, in this paper we reviewed important aspects of cancer, present-day cancer treatments, and historical aspects of BMCT. Here, we provided a four-step framework that can be used in screening and identifying bacteria with cancer therapeutic potential, including those that are uncultivable. Systematic methodologies such as the ones suggested here could prove valuable to new BMCT researchers, including experienced non-BMCT researchers in possession of extensive knowledge and resources of bacterial genomics. Lastly, our analyses highlight the need to establish and standardize quantitative methods that can be used to identify and compare bacteria with important cancer therapeutic traits.

Hepatic gas gangrene caused by Clostridium novyi

We report the case of a patient with advanced gastric cancer and multiple liver metastases, who presented with bacteremia and hepatic gas gangrene caused by Clostridium novyi (C. novyi). The gas gangrene caused abscesses to form within metastatic lesions. This case highlights the antitumor effects of C. novyi in human.

Iron-Oxide Nanocluster Labeling of Clostridium novyi-NT Spores for MR Imaging-Monitored Locoregional Delivery to Liver Tumors in Rat and Rabbit Models

PURPOSE

To label Clostridium novyi-NT spores (C. novyi-NT) with iron oxide nanoclusters and track distribution of bacteria during magnetic resonance (MR) imaging-monitored locoregional delivery to liver tumors using intratumoral injection or intra-arterial transcatheter infusion.

MATERIALS AND METHODS

Vegetative state C. novyi-NT were labeled with iron oxide particles followed by induction of sporulation. Labeling was confirmed with fluorescence microscopy and transmission electron microscopy (TEM). T2 and T2* relaxation times for magnetic clusters and magnetic microspheres were determined using 7T and 1.5T MR imaging scanners. In vitro assays compared labeled bacteria viability and oncolytic potential to unlabeled controls. Labeled spores were either directly injected into N1-S1 rodent liver tumors (n = 24) or selectively infused via the hepatic artery in rabbits with VX2 liver tumors (n = 3). Hematoxylin-eosin, Prussian blue, and gram staining were performed. Statistical comparison methods included paired t-test and ANOVA.

RESULTS

Both fluorescence microscopy and TEM studies confirmed presence of iron oxide labels within the bacterial spores. Phantom studies demonstrated that the synthesized nanoclusters produce R2 relaxivities comparable to clinical agents. Labeling had no significant impact on overall growth or oncolytic properties (P >.05). Tumor signal-to-noise ratio (SNR) decreased significantly following intratumoral injection and intra-arterial infusion of labeled spores (P <.05). Prussian blue and gram staining confirmed spore delivery.

CONCLUSIONS

C. novyi-NT spores can be internally labeled with iron oxide nanoparticles to visualize distribution with MR imaging during locoregional bacteriolytic therapy involving direct injection or intra-arterial transcatheter infusion.

Phototrophic purple bacteria as optoacoustic in vivo reporters of macrophage activity

Τhe morphology, physiology and immunology, of solid tumors exhibit spatial heterogeneity which complicates our understanding of cancer progression and therapy response. Understanding spatial heterogeneity necessitates high resolution in vivo imaging of anatomical and pathophysiological tumor information. We introduce Rhodobacter as bacterial reporter for multispectral optoacoustic (photoacoustic) tomography (MSOT). We show that endogenous bacteriochlorophyll a in Rhodobacter gives rise to strong optoacoustic signals >800 nm away from interfering endogenous absorbers. Importantly, our results suggest that changes in the spectral signature of Rhodobacter which depend on macrophage activity inside the tumor can be used to reveal heterogeneity of the tumor microenvironment. Employing non-invasive high resolution MSOT in longitudinal studies we show spatiotemporal changes of Rhodobacter spectral profiles in mice bearing 4T1 and CT26.WT tumor models. Accessibility of Rhodobacter to genetic modification and thus to sensory and therapeutic functions suggests potential for a theranostic platform organism.

Current optoacoustic probes for cancer imaging have limitations including background noise, long-term toxicity and scarce imaging depth in living tissue. Here the authors use Rhodobacter, purple bacteria rich in bacteriochlorophyll a, as an optoacoustic reporter to image tumor-associated macrophages in mice in vivo.

Report on the NCI Microbial-Based Cancer Therapy Conference

The National Cancer Institute Inaugural Microbial-Based Cancer Therapy Conference was held in Bethesda, Maryland, on July 11-12, 2017. This interdisciplinary forum included industry leaders, academic investigators, and regulatory officers involved in the development of microbial-based therapies for the treatment of cancer. The aim of the meeting was to discuss the potential of virus- and bacteria-based therapies to halt tumorigenesis and induce immune responses in cancers where conventional therapy is inadequate. This summary highlights topics and viewpoints raised by the presenters and discussants and should not be viewed as the conclusions or recommendations of the workshop as a whole. Cancer Immunol Res; 6(2); 122-6. ©2017 AACR.

Oxygen Production of Modified Core-Shell CuO@ZrO2 Nanocomposites by Microwave Radiation to Alleviate Cancer Hypoxia for Enhanced Chemo-Microwave Thermal Therapy

There are acknowledged risks of metastasis of cancer cells and obstructing cancer treatment from hypoxia. In this work, we design a multifunctional nanocomposite for treating hypoxia based on the oxygen release capability of CuO triggered by microwave (MW). Core-shell CuO@ZrO₂ nanocomposites are prepared by confining CuO nanoparticles within the cavities of mesoporous ZrO₂ hollow nanospheres. 1-Butyl-3-methylimidazolium hexafluorophosphate (IL) is loaded to the CuO@ZrO₂ nanocomposites for improving microwave thermal therapy (MWTT). 1-Tetradecanol (PCM) is introduced to regulate the release of chemotherapeutic drugs of doxorubicin (DOX). Thus, the IL-DOX-PCM-CuO@ZrO₂ multifunctional (IDPC@Zr) nanocomposites are obtained. Finally, IDPC@Zr nanocomposites are modified by monomethoxy polyethylene glycol sulfhydryl (mPEG-SH, 5 kDa) (IDPC@Zr-PEG nanocomposites). IDPC@Zr-PEG nanocomposites can produce oxygen in the tumor microenvironment during the course of tumor treatment, thereby alleviating the hypoxic state and improving the therapeutic effect. In vivo antitumor experiments demonstrate a very high tumor inhibition rate of 92.14%. In addition, computed tomography (CT) imaging contrast of the nanocomposites can be enhanced due to the high atomic number of Zr. Therefore, IDPC@Zr-PEG nanocomposites can be applied for monitoring the tumor-treatment process in real time. This combined therapy offers many opportunities, such as the production of oxygen from CuO nanoparticles by MW to alleviate hypoxia, the enhancement of combined treatment of MWTT and chemotherapy, and the potential application of CT imaging to visualize the treatment process, which therefore provides a promising method for the clinical treatment of tumors in the future.

Yersinia Pseudotuberculosis Modulates Regulatory T Cell Stability via Injection of Yersinia Outer Proteins in a Type III Secretion System-Dependent Manner

Adaptive immunity is essentially required to control acute infection with enteropathogenic Yersinia pseudotuberculosis (Yptb). We have recently demonstrated that Yptb can directly modulate naïve CD4⁺ T cell differentiation. However, whether fully differentiated forkhead box protein P3 (Foxp3⁺) regulatory T cells (Tregs), fundamental key players to maintain immune homeostasis, are targeted by Yptb remains elusive. Here, we demonstrate that within the CD4⁺ T cell compartment Yptb preferentially targets Tregs and injects Yersinia outer proteins (Yops) in a process that depends on the type III secretion system and invasins. Remarkably, Yop-translocation into ex vivo isolated Foxp3⁺ Tregs resulted in a substantial downregulation of Foxp3 expression and a decreased capacity to express the immunosuppressive cytokine interleukin-10 (IL-10). Together, these findings highlight that invasins are critically required to mediate Yptb attachment to Foxp3⁺ Tregs, which allows efficient Yop-translocation and finally enables the modulation of the Foxp3⁺ Tregs' suppressive phenotype.

Tumour-targeting bacteria engineered to fight cancer

Recent advances in targeted therapy and immunotherapy have once again raised the hope that a cure might be within reach for many cancer types. Yet, most late-stage cancers are either insensitive to the therapies to begin with or develop resistance later. Therapy with live tumour-targeting bacteria provides a unique option to meet these challenges. Compared with most other therapeutics, the effectiveness of tumour-targeting bacteria is not directly affected by the 'genetic makeup' of a tumour. Bacteria initiate their direct antitumour effects from deep within the tumour, followed by innate and adaptive antitumour immune responses. As microscopic 'robotic factories', bacterial vectors can be reprogrammed following simple genetic rules or sophisticated synthetic bioengineering principles to produce and deliver anticancer agents on the basis of clinical needs. Therapeutic approaches using live tumour-targeting bacteria can either be applied as a monotherapy or complement other anticancer therapies to achieve better clinical outcomes. In this Review, we summarize the potential benefits and challenges of this approach. We discuss how live bacteria selectively induce tumour regression and provide examples to illustrate different ways to engineer bacteria for improved safety and efficacy. Finally, we share our experience and insights on oncology clinical trials with tumour-targeting bacteria, including a discussion of the regulatory issues.

Bacterial spores, from ecology to biotechnology

The production of a highly specialized cell structure called a spore is a remarkable example of a survival strategy displayed by bacteria in response to challenging environmental conditions. The detailed analysis and description of the process of sporulation in selected model organisms have generated a solid background to understand the cellular processes leading to the formation of this specialized cell. However, much less is known regarding the ecology of spore-formers. This research gap needs to be filled as the feature of resistance has important implications not only on the survival of spore-formers and their ecology, but also on the use of spores for environmental prospection and biotechnological applications.

Bacterial microbots for acid-labile release of hybrid micelles to promote the synergistic antitumor efficacy

Bacteria have inherent properties of self-propelled navigation and specific infiltration into solid tumors. In the current study, we investigate a novel type of bacterial microbots for delivery of hybrid micelles to promote the synergistic antitumor efficacy. Escherichia coli Nissle 1917 (EcN) is used as a bacterial carrier to immobilize amphiphilic copolymers through acid-labile 2-propionic-3-methylmaleic anhydride (CDM) linkers. Doxorubicin (DOX) and α-tocopheryl succinate (TOS) are conjugated with poly(ethylene glycol) through disulfide linkers to obtain amphiphilic promicelle polymers (PM_TOS and PM_DOX). Tetrazine and norbornene terminals are grafted on EcN and PM_TOS/PM_DOX copolymers, respectively, and the mild and site-specific bioorthogonal reaction between them maintains the viability, motion ability, and tumor accumulation capability of the conjugated EcN. The PM_TOS/PM_DOX copolymers are released from bacterial microbots in response to the slightly acidic tumor microenvironment, followed by in situ formation of these copolymers as hybrid micelles (M_D/T). The self-assembled micelles from PM_TOS/PM_DOX with a ratio of 1:2 demonstrate the most significant synergistic efficacy, and the released M_D/T hybrid micelles exhibit cellular uptake efficiency, glutathione (GSH)-sensitive drug release, and cytotoxicities similar to those exhibited by micelles prepared by solvent evaporation. Because of the consecutive process of the self-propelling nature of bacteria and preferential accumulation of EcN in tumors, in situ formation of M_D/T hybrid micelles, and intracellular drug release, bacterial microbots have shown remarkable antitumor efficacy with regard to animal survival, tumor growth, and apoptosis induction in tumor cells. Therefore, we demonstrate a feasible strategy for the construction of bacterial microbots to achieve tumor accumulation and on-demand release of multiple therapeutic agents for synergistic antitumor efficacy.

STATEMENT OF SIGNIFICANCE

Challenges remain in the targeted delivery of nanoparticles to solid tumors and the realization of synergistic efficacy in cancer chemotherapy. In the current study, we explore a novel class of bacterial microbots to load, deliver, and release hybrid micelles. Escherichia coli Nissle 1917 (EcN) is used as a bacterial carrier to immobilize amphiphilic copolymers through acid-labile linkers, and the released copolymers are self-assembled into micelles. The resulting bacterial microbots integrate self-propelling bacteria and self-assembling amphiphilic polymers into micelles and realize pH-responsive release of promicelle polymers from bacterial microbots and glutathione-responsive intracellular release of drugs. A synergistic antitumor efficacy is achieved using hybrid micelles, which release both doxorubicin and α-tocopheryl succinate to display toxicities in the nucleus and mitochondria, respectively.

Addressing the Adult Soft Tissue Sarcoma Microenvironment with Intratumoral Immunotherapy

Sarcoma is comprised of a heterogeneous group of tumors originating from the mesenchyme. Sarcoma is also the first tumor that responded to immunotherapeutic agents often termed as “Coley's toxins.” However, immunotherapy is yet to establish its presence in sarcomas. Complex interactions between tumor and immune cells in the tumor microenvironment play a crucial role in response to immunotherapy. There is a dynamic equilibrium created by the immune cells infiltrating the tumor, and this forms the basis of tumor evasion. Manipulating the intratumoral microenvironment will help overcome tumor evasion.

White paper on microbial anti-cancer therapy and prevention

In this White Paper, we discuss the current state of microbial cancer therapy. This paper resulted from a meeting ('Microbial Based Cancer Therapy') at the US National Cancer Institute in the summer of 2017. Here, we define 'Microbial Therapy' to include both oncolytic viral therapy and bacterial anticancer therapy. Both of these fields exploit tumor-specific infectious microbes to treat cancer, have similar mechanisms of action, and are facing similar challenges to commercialization. We designed this paper to nucleate this growing field of microbial therapeutics and increase interactions between researchers in it and related fields. The authors of this paper include many primary researchers in this field. In this paper, we discuss the potential, status and opportunities for microbial therapy as well as strategies attempted to date and important questions that need to be addressed. The main areas that we think will have the greatest impact are immune stimulation, control of efficacy, control of delivery, and safety. There is much excitement about the potential of this field to treat currently intractable cancer. Much of the potential exists because these therapies utilize unique mechanisms of action, difficult to achieve with other biological or small molecule drugs. By better understanding and controlling these mechanisms, we will create new therapies that will become integral components of cancer care.

Canine sarcomas as a surrogate for the human disease

Pet dogs are becoming increasingly recognized as a population with the potential to inform medical research through their treatment for a variety of maladies by veterinary health professionals. This is the basis of the One Health initiative, supporting the idea of collaboration between human and animal health researchers and clinicians to study spontaneous disease processes and treatment in animals to inform human health. Cancer is a major health burden in pet dogs, accounting for approximately 30% of deaths across breeds. As such, pet dogs with cancer are becoming increasingly recognized as a resource for studying the pharmacology and therapeutic potential of anticancer drugs and therapies under development. This was recently highlighted by a National Academy of Medicine Workshop on Comparative Oncology that took place in mid-2015 (http://www.nap.edu/21830). One component of cancer burden in dogs is their significantly higher incidence of sarcomas as compared to humans. This increased incidence led to canine osteosarcoma being an important component in the development of surgical approaches for osteosarcoma in children. Included in this review of sarcomas in dogs is a description of the incidence, pathology, molecular characteristics and previous translational therapeutic studies associated with these tumors. An understanding of the patho-physiological and molecular characteristics of these naturally occurring canine sarcomas holds great promise for effective incorporation into drug development schemas, for evaluation of target modulation or other pharmacodynamic measures associated with therapeutic response. These data could serve to supplement other preclinical data and bolster clinical investigations in tumor types for which there is a paucity of human patients for clinical trials.

Bacterial components as naturally inspired nano-carriers for drug/gene delivery and immunization: Set the bugs to work?

Drug delivery is a rapidly growing area of research motivated by the nanotechnology revolution, the ideal of personalized medicine, and the desire to reduce the side effects of toxic anti-cancer drugs. Amongst a bewildering array of different nanostructures and nanocarriers, those examples that are fundamentally bio-inspired and derived from natural sources are particularly preferred. Delivery of vaccines is also an active area of research in this field. Bacterial cells and their components that have been used for drug delivery, include the crystalline cell-surface layer known as "S-layer", bacterial ghosts, bacterial outer membrane vesicles, and bacterial products or derivatives (e.g. spores, polymers, and magnetic nanoparticles). Considering the origin of these components from potentially pathogenic microorganisms, it is not surprising that they have been applied for vaccines and immunization. The present review critically summarizes their applications focusing on their advantages for delivery of drugs, genes, and vaccines.

Attenuated Bacteria as Immunotherapeutic Tools for Cancer Treatment

The use of attenuated bacteria as cancer therapeutic tools has garnered increasing scientific interest over the past 10 years. This is largely due to the development of bacterial strains that maintain good anti-tumor efficacy, but with reduced potential to cause toxicities to the host. Because of its ability to replicate in viable as well as necrotic tissue, cancer therapy using attenuated strains of facultative anaerobic bacteria, such as Salmonella, has several advantages over standard treatment modalities, including chemotherapy and radiotherapy. Despite some findings suggesting that it may operate through a direct cytotoxic effect against cancer cells, there is accumulating evidence demonstrating that bacterial therapy acts by modulating cells of the immune system to counter the growth of the tumor. Herein, we review the experimental evidence underlying the success of bacterial immunotherapy against cancer and highlight the cellular and molecular alterations in the peripheral immune system and within the tumor microenvironment that have been reported following different forms of bacterial therapy. Our improved understanding of these mechanisms should greatly aid in the translational application of bacterial therapy to cancer patients.

The microbiome in cancer immunotherapy: Diagnostic tools and therapeutic strategies

The fine line between human health and disease can be driven by the interplay between host and microbial factors. This "metagenome" regulates cancer initiation, progression, and response to therapies. Besides the capacity of distinct microbial species to modulate the pharmacodynamics of chemotherapeutic drugs, symbiosis between epithelial barriers and their microbial ecosystems has a major impact on the local and distant immune system, markedly influencing clinical outcome in cancer patients. Efficacy of cancer immunotherapy with immune checkpoint antibodies can be diminished with administration of antibiotics, and superior efficacy is observed with the presence of specific gut microbes. Future strategies of precision medicine will likely rely on novel diagnostic and therapeutic tools with which to identify and correct defects in the microbiome that compromise therapeutic efficacy.

Immune response to C. novyi-NT immunotherapy

Clostridium novyi-NT (CVN-NT) spores germinate in hypoxic regions of tumors and have successfully cured induced neoplasia in mouse models and resulted in objective tumor responses in naturally developing neoplasia in the dog. The objective of this pilot, descriptive, prospective, clinical investigation, was to evaluate and describe the immune response to CNV-NT spores to better understand which immune pathways might play a role in the response to this bacteriolytic immunotherapy. Intratumoral injection of CNV-NT spores result in increased phagocytosis and NK cell-like function after treatment. Intravenous injection of CNV-NT spores resulted in increased LPS-induced TNF-α production, LTA-induced IL-10 production and NK cell-like function post-treatment. Increased NK cell-like function was sustained to 28 (intratumoral) or 56 (intravenous) days post-treatment, and increased phagocytic function was sustained to 28 days post-treatment suggesting that CNV-NT spores induce longer-term immune cell function changes. Future investigations evaluating long-term immune system changes and associations between immune function and tumor remission rates should include evaluation of these pathways.

Local application of bacteria improves safety of Salmonella -mediated tumor therapy and retains advantages of systemic infection

Cancer is a devastating disease and a large socio-economic burden. Novel therapeutic solutions are on the rise, although a cure remains elusive. Application of microorganisms represents an ancient therapeutic strategy, lately revoked and refined via simultaneous attenuation and amelioration of pathogenic properties. Salmonella Typhimurium has prevailed in preclinical development. Yet, using virulent strains for systemic treatment might cause severe side effects. In the present study, we highlight a modified strain based on Salmonella Typhimurium UK-1 expressing hexa-acylated Lipid A. We corroborate improved anti-tumor properties of this strain and investigate to which extent an intra-tumoral (i.t.) route of infection could help improve safety and retain advantages of systemic intravenous (i.v.) application. Our results show that i.t. infection exhibits therapeutic efficacy against CT26 and F1.A11 tumors similar to a systemic route of inoculation. Moreover, i.t. application allows extensive dose titration without compromising tumor colonization. Adverse colonization of healthy organs was generally reduced via i.t. infection and accompanied by less body weight loss of the murine host. Despite local application, adjuvanticity remained, and a CT26-specific CD8⁺ T cell response was effectively stimulated. Most interestingly, also secondary tumors could be targeted with this strategy, thereby extending the unique tumor targeting ability of Salmonella. The i.t. route of inoculation may reap the benefits of systemic infection and aid in safety assurance while directing potency of an oncolytic vector to where it is most needed, namely the primary tumor.

Plasmodium parasite as an effective hepatocellular carcinoma antigen glypican-3 delivery vector

We have previously demonstrated that malaria parasite infection has an anti-tumor effect in a mouse model. This research aimed to investigate the possibility of using Plasmodium parasite as a novel vaccine vector for hepatocellular carcinoma (HCC) immunotherapy. We constructed a Plasmodium yoelii 17XNL strain (P.y) expressing murine glypican-3 (GPC3) protein (P.y-GPC3), and examined its therapeutic potency in a murine Hepa1-6-induced hepatoma model that highly expressed GPC3 protein. The prerequisites for invoking a CD8+ T cell response were assessed after P.y-based immunization, which included obviously increased concentrations of T helper cell type 1 (Th1)-associated cytokines, such as IL-2, IFN-γ and TNF-α, in serum and preferential expansion of the CD8α+ dendritic cell (DC) subset with higher expression of CD80 and CD86 molecules. Compared with uninfected and wild-type P.y-infected mice, a significant GPC3-specific cytotoxic T lymphocyte (CTL) response was detected in P.y-GPC3 vaccinated mice. Furthermore, P.y-GPC3-based vaccination dramatically inhibited Hepa1-6-induced tumor growth in the implanted HCC and prolonged the survival of tumor-bearing mice. We concluded that a Plasmodium-based vector is highly efficient in inducing tumor antigen-specific T cell-mediated immunity and protection against tumor cells. More broadly, this strategy supported our hypothesis that Plasmodium parasites, as novel therapeutic antigen vectors, may be applicable to tumor immunotherapy for patients with HCC.

Identification of immunologic and clinical characteristics that predict inflammatory response to C. Novyi-NT bacteriolytic immunotherapy

BACKGROUND

Clostridium novyi-NT (CNV-NT), has shown promise as a bacterolytic therapy for solid tumors in mouse models and in dogs with naturally developing neoplasia. Factors that impact the immunologic response to therapy are largely unknown. The goal of this pilot study was to determine if plasma immune biomarkers, immune cell function, peripheral blood cytological composition and tumor characteristics including evaluation of a PET imaging surrogate of tumor tissue hypoxia could predict which dogs with naturally developing naïve neoplasia would develop an inflammatory response to CNV-NT.

RESULTS

Dogs that developed an inflammatory response to CNV-NT had a higher heart rate, larger gross tumor volume, greater tumor [⁶⁴Cu]ATSM SUV_Max, increased constitutive leukocyte IL-10 production, more robust NK cell-like function and greater peripheral blood lymphocyte counts compared to dogs that did not develop an inflammatory response to CNV-NT. Of these, unstimulated leukocyte IL-10 production, heart rate, and gross tumor volume appeared to be the best predictors of which dogs will develop an inflammatory response to CNV-NT.

CONCLUSIONS

Development of inflammation in response to CNV-NT is best predicted by pretreatment unstimulated leukocyte IL-10 production, heart rate, and gross tumor volume.

Comparison of the common bacteria in human and mouse tumours using high-throughput sequencing

Evidence has indicated that gut bacteria may serve an important role in cancer development and therapy, while little work has been done to explore the microbial diversity inside tumours. In the present study, high‑throughput sequencing was first used to identify and compare the microbial diversity in human and mouse tumours. Principal component analysis (PCA) and β-diversity indicated a low microbial similarity among mouse artificial tumours (M.AT group), mouse spontaneous tumours (M.T group) and human tumours (H.T group), and Serratia (35.85 vs. 32.64 vs. 73.32%), Pseudomonas (24.10 vs. 16.62 vs. 1.72%) and Ochrobactrum (6.28 vs. 11.08 vs. 11.90%) were identified as dominant bacteria at the genus level. In addition, Venn results indicated 103 common operational taxonomic units (OTUs) in the M.AT, M.T and H.T groups, and only 2 and 1 OTUs belonged to Lactobacillus and Escherichia, respectively, while no OTUs belonging to Salmonella, Bifidobacteria or Clostridium were identified. In the present study, the common bacteria between human and mouse tumours were identified, which may serve as potential strains for bacteriotherapy of cancers.

Tumor-targeting Salmonella typhimurium A1-R regresses an osteosarcoma in a patient-derived xenograft model resistant to a molecular-targeting drug

Osteosarcoma occurs mostly in children and young adults, who are treated with multiple agents in combination with limb-salvage surgery. However, the overall 5-year survival rate for patients with recurrent or metastatic osteosarcoma is 20-30% which has not improved significantly over 30 years. Refractory patients would benefit from precise individualized therapy. We report here that a patient-derived osteosarcoma growing in a subcutaneous nude-mouse model was regressed by tumor-targeting Salmonella typhimurium A1-R (S. typhimurium A1-R, p<0.001 compared to untreated control). The osteosarcoma was only partially sensitive to the molecular-targeting drug sorafenib, which did not arrest its growth. S. typhimurium A1-R was significantly more effective than sorafenib (P <0.001). S. typhimurium grew in the treated tumors and caused extensive necrosis of the tumor tissue. These data show that S. typhimurium A1-R is powerful therapy for an osteosarcoma patient-derived xenograft model.

Tumor-targeting Salmonella typhimurium A1-R is a highly effective general therapeutic for undifferentiated soft tissue sarcoma patient-derived orthotopic xenograft nude-mouse models

Undifferentiated soft tissue sarcoma (USTS) is a recalcitrant and heterogeneous subgroup of soft tissue sarcoma with high risk of metastasis and recurrence. Due to heterogeneity of USTS, there is no reliably effective first-line therapy. We have generated tumor-targeting Salmonella typhimurium A1-R (S. typhimurium A1-R), which previously showed strong efficacy on single patient-derived orthotopic xenograft (PDOX) models of Ewing's sarcoma and follicular dendritic cell sarcoma. In the present study, tumor resected from 4 patients with a biopsy-proven USTS (2 undifferentiated pleomorphic sarcoma [UPS], 1 undifferentiated sarcoma not otherwise specified [NOS] and 1 undifferentiated spindle cell sarcoma [USS]) were grown orthotopically in the biceps femoris muscle of mice to establish PDOX models. One USS model and one UPS model were doxorubicin (DOX) resistant. One UPS and the NOS model were partially sensitive to DOX. DOX is first-line therapy for these diseases. S. typhimurium A1-R arrested tumor growth all 4 models. In addition to arresting tumor growth in each case, S. typhimurium A1-R was significantly more efficacious than DOX in each case, thereby surpassing first-line therapy. These results suggest that S. typhimurium A1-R can be a general therapeutic for USTS and possibly sarcoma in general.

Mitochondria-based aircraft carrier enhances in vivo imaging of carbon quantum dots and delivery of anticancer drug

The application of engineered bacteria-based drug delivery vehicles to treat cancer has been practiced for more than a century. Mitochondria, evolutionarily originated from bacteria, are ubiquitous, semi-autonomous cellular organelles. In this study, we present the first exploration of using mitochondria as a delivery system of carbon quantum dots (CQDs) for in vivo imaging and administration of the anticancer drug doxorubicin (DOX). The results show that mitochondria as carriers are compatible with CQD loading and preserve the optical properties of CQDs. Moreover, the mitochondria delivery system can improve the CQD bio-distribution in organs and prolong the retention time of CQDs after intravenous injection. Furthermore, mitochondria loaded with doxorubicin hydrochloride (Mito-DOX) show an enhanced therapeutic effect compared to free DOX. The mitochondria-based "aircraft" system may be a promising novel therapeutic platform with high potential for biological imaging and drug delivery to fight cancer and other diseases.

High efficacy of tumor-targeting Salmonella typhimurium A1-R on a doxorubicin- and dactolisib-resistant follicular dendritic-cell sarcoma in a patient-derived orthotopic xenograft PDOX nude mouse model

Follicular dendritic-cell sarcoma (FDCS) is a rare and recalcitrant disease. In the present study, a patient-derived orthotopic xenograft (PDOX) mouse model of FDCS was established in the biceps muscle of nude mice. The FDCS PDOX was resistant to both doxorubicin (DOX) and NVP-BEZ235, dactolisib (BEZ) an experimental agent which is a dual pan-phosphoinositide 3-kinase-mammalian target of rapamycin inhibitor. However, in contrast to DOX and BEZ, the FDCS PDOX was sensitive to the tumor-targeting bacterial strain, Salmonella typhimurium A1-R (S. typhimurium A1-R). The combination of S. typhimurium A1-R and either DOX or BEZ did not increase the antitumor efficacy of S. typhimurium A1-R, indicating that DOX and BEZ were not active in this PDOX model. The efficacy of S. typhimurium A1-R in this recalcitrant FDCS gives strong impetus to move bacterial therapy to clinical trials for this disease. The findings of the present study are of particular importance since it demonstrates that S. typhimurium A1-R is effective in a PDOX model of FDCS established from a patient who failed DOX therapy.

The FDA-approved anti-cancer drugs, streptozotocin and floxuridine, reduce the virulence of Staphylococcus aureus

In Staphylococcus aureus, an important Gram-positive human pathogen, the SaeRS two-component system is essential for the virulence and a good target for the development of anti-virulence drugs. In this study, we screened 12,200 small molecules for Sae inhibitors and identified two anti-cancer drugs, streptozotocin (STZ) and floxuridine (FU), as lead candidates for anti-virulence drug development against staphylococcal infections. As compared with STZ, FU was more efficient in repressing Sae-regulated promoters and protecting human neutrophils from S. aureus-mediated killing. FU inhibited S. aureus growth effectively whereas STZ did not. Intriguingly, RNA-seq analysis suggests that both compounds inhibit other virulence-regulatory systems such as Agr, ArlRS, and SarA more efficiently than they inhibit the Sae system. Both compounds induced prophages from S. aureus, indicating that they cause DNA damages. Surprisingly, a single administration of the drugs was sufficient to protect mice from staphylococcal intraperitoneal infection. Both compounds showed in vivo efficacy in a murine model of blood infection too. Finally, at the experimental dosage, neither compound showed any noticeable side effects on blood glucose level or blood cell counts. Based on these results, we concluded that STZ and FU are promising candidates for anti-virulence drug development against S. aureus infection.

Bacterial Therapy of Cancer: Promises, Limitations, and Insights for Future Directions

Spontaneous tumors regression has been associated with microbial infection for 100s of years and inspired the use of bacteria for anticancer therapy. Dr. William B. Coley (1862-1936), a bone- sarcoma surgeon, was a pioneer in treating his patients with both live bacterial-based and mixture of heat-killed bacteria known as "Coley's toxins." Unfortunately, Coley was forced to stop his work which interrupted this field for about half a century. Currently, several species of bacteria are being developed against cancer. The bacterial species, their genetic background and their infectious behavior within the tumor microenvironment are thought to be relevant factors in determining their anti-tumor effectiveness in vivo. In this perspective article we will update the most promising results achieved using bacterial therapy (alone or combined with other strategies) in clinically-relevant animal models of cancer and critically discuss the impact of the bacterial variants, route of administration and mechanisms of bacteria-cancer-cell interaction. We will also discuss strategies to apply this information using modern mouse models, molecular biology, genetics and imaging for future bacterial therapy of cancer patients.

Two-step enhanced cancer immunotherapy with engineered Salmonella typhimurium secreting heterologous flagellin

We report a method of cancer immunotherapy using an attenuated Salmonella typhimurium strain engineered to secrete Vibrio vulnificus flagellin B (FlaB) in tumor tissues. Engineered FlaB-secreting bacteria effectively suppressed tumor growth and metastasis in mouse models and prolonged survival. By using Toll-like receptor 5 (TLR5)-negative colon cancer cell lines, we provided evidence that the FlaB-mediated tumor suppression upon bacterial colonization is associated with TLR5-mediated host reactions in the tumor microenvironment. These therapeutic effects were completely abrogated in TLR4 and MyD88 knockout mice, and partly in TLR5 knockout mice, indicating that TLR4 signaling is a requisite for tumor suppression mediated by FlaB-secreting bacteria, whereas TLR5 signaling augmented tumor-suppressive host reactions. Tumor microenvironment colonization by engineered Salmonella appeared to induce the infiltration of abundant immune cells such as monocytes/macrophages and neutrophils via TLR4 signaling. Subsequent secretion of FlaB from colonizing Salmonella resulted in phenotypic and functional activation of intratumoral macrophages with M1 phenotypes and a reciprocal reduction in M2-like suppressive activities. Together, these findings provide evidence that nonvirulent tumor-targeting bacteria releasing multiple TLR ligands can be used as cancer immunotherapeutics.

Proteus mirabilis inhibits cancer growth and pulmonary metastasis in a mouse breast cancer model

A variety of bacteria have been used as agents and vectors for antineoplastic therapy. A series of mechanisms, including native bacterial toxicity, sensitization of the immune system and competition for nutrients, may contribute to antitumor effects. However, the antitumor effects of Proteus species have been minimally studied, and it is not clear if bacteria can alter tumor hypoxia as a component of their antineoplastic effect. In the present study, Proteus mirabilis bacteria were evaluated for the ability to proliferate and accumulate in murine tumors after intravenous injection. To further investigate the efficacy and safety of bacterial injection, mice bearing 4T1 tumors were treated with an intravenous dose of 5×107 CFU Proteus mirabilis bacteria via the tail vein weekly for three treatments. Histopathology, immunohistochemistry (IHC) and western analysis were then performed on excised tumors. The results suggested Proteus mirabilis localized preferentially to tumor tissues and remarkably suppressed the growth of primary breast cancer and pulmonary metastasis in murine 4T1 models. Results showed that the expression of NKp46 and CD11c was significantly increased after bacteria treatment. Furthermore, tumor expression of carbonic anhydrase IX (CA IX) and hypoxia inducible factor-1a (HIF-1a), surrogates for hypoxia, was significantly lower in the treated group than the control group mice as assessed by IHC and western analysis. These findings demonstrated that Proteus mirabilis may a promising bacterial strain for used against primary tumor growth and pulmonary metastasis, and the immune system and reduction of tumor hypoxia may contribute to the antineoplastic and antimetastatic effects observed.

Tumor-targeting Salmonella typhimurium A1-R in combination with doxorubicin eradicate soft tissue sarcoma in a patient-derived orthotopic xenograft (PDOX) model

A patient with high grade undifferentiated pleomorphic soft-tissue sarcoma from a striated muscle was grown orthotopically in the right biceps femoris muscle of mice to establish a patient-derived orthotopic xenograft (PDOX) model. Twenty PDOX mice were divided into 4 groups: G1, control without treatment; G2, Salmonella typhimurium (S. typhimurium)A1-R administered by intratumoral (i.t.) injection once a week for 4 weeks; G3, doxorubicin (DOX) administered by intraperitoneal (i.p.) injection once a week for 4 weeks; G4, S. typhimurium A1-R (i.t.) administered once a week for 2 weeks followed by i.p. doxorubicin once a week for 2 weeks. On day 25 from the initiation of treatment, tumor volume in G2, G3, and G4 was significantly lower than G1. Mice found without gross tumor included one mouse (20%) in G2; one mouse (20%) in G3; and 3 mice (60%) in G4. Body weight loss did not significantly differ between the 3 treated groups or from the untreated control. Histological examination revealed eradication of tumor only in G4 where mice were treated with S. typhimurium A1-R followed by DOX. Our present study indicates future clinical potential of combining S. typhimurium A1-R with chemotherapy such as DOX for soft tissue sarcoma patients.

Engineered Salmonella enterica serovar Typhimurium overcomes limitations of anti-bacterial immunity in bacteria-mediated tumor therapy

Cancer is one of the leading causes of death in the industrialized world and represents a tremendous social and economic burden. As conventional therapies fail to provide a sustainable cure for most cancer patients, the emerging unique immune therapeutic approach of bacteria-mediated tumor therapy (BMTT) is marching towards a feasible solution. Although promising results have been obtained with BMTT using various preclinical tumor models, for advancement a major concern is immunity against the bacterial vector itself. Pre-exposure to the therapeutic agent under field conditions is a reasonable expectation and may limit the therapeutic efficacy of BMTT. In the present study, we investigated the therapeutic potential of Salmonella and E. coli vector strains in naïve and immunized tumor bearing mice. Pre-exposure to the therapeutic agent caused a significant aberrant phenotype of the microenvironment of colonized tumors and limited the in vivo efficacy of established BMTT vector strains Salmonella SL7207 and E. coli Symbioflor-2. Using targeted genetic engineering, we generated the optimized auxotrophic Salmonella vector strain SF200 (ΔlpxR9 ΔpagL7 ΔpagP8 ΔaroA ΔydiV ΔfliF) harboring modifications in Lipid A and flagella synthesis. This combination of mutations resulted in an increased immune-stimulatory capacity and as such the strain was able to overcome the efficacy-limiting effects of pre-exposure. Thus, we conclude that any limitations of BMTT concerning anti-bacterial immunity may be countered by strategies that optimize the immune-stimulatory capacity of the attenuated vector strains.

Combining anaerobic bacterial oncolysis with vaccination that blocks interleukin-10 signaling may achieve better outcomes for late stage cancer management

Late stage solid tumors cause significant cancer mortality rates worldwide and effective therapy remains a big challenge. Cancer therapeutic vaccines elicit tumor specific T cells that kill tumor cells yet often fail to result in tumor destruction because of the limited T cell response and the local immune-suppressive environment. Blocking interleukin 10 (IL-10) signaling at the time of therapeutic vaccination elicits much stronger T cell responses than vaccination without IL-10 blocking. Anaerobic oncolytic bacteria target hypoxic regions of the late stage tumor tissues which not only stops tumor growth but also provides a pro-inflammatory environment that may increase the effectiveness of a therapeutic vaccine by recruiting more effector T cells to tumor site. In this review, we argue that combining both bacterial and vaccine therapies may improve the efficiency of late stage cancer management.

Advances in bacterial cancer therapies using synthetic biology

Synthetic biology aims to apply engineering principles to biology by modulating the behavior of living organisms. An emerging application of this field is the engineering of bacteria as a cancer therapy by the programming of therapeutic, safety, and specificity features through genetic modification. Here, we review progress in this engineering including the targeting of bacteria to tumors, specific sensing and response to tumor microenvironments, remote induction methods, and controllable release of therapeutics. We discuss the most prominent bacteria strains used and their specific properties and the types of therapeutics tested thus far. Finally, we note current challenges, such as genetic stability, that researchers must address for successful clinical implementation of this novel therapy in humans.

High-efficacy targeting of colon-cancer liver metastasis with Salmonella typhimurium A1-R via intra-portal-vein injection in orthotopic nude-mouse models

Liver metastasis is the main cause of colon cancer-related death and is a recalcitrant disease. We report here the efficacy and safety of intra-portal-vein (iPV) targeting of Salmonella typhimurium A1-R on colon cancer liver metastasis in a nude-mouse orthotopic model. Nude mice with HT29 human colon cancer cells, expressing red fluorescent protein (RFP) (HT29-RFP), growing in the liver were administered S. typhimurium A1-R by either iPV (1×10⁴ colony forming units (CFU)/100 μl) or, for comparison, intra-venous injection (iv; 5×10⁷ CFU/100 μl). Similar amounts of bacteria were delivered to the liver with the two doses, indicating that iPV delivery is 5×10³ times more efficient than iv delivery. Treatment efficacy was evaluated by tumor fluorescent area (mm²) and total fluorescence intensity. Tumor fluorescent area and fluorescence intensity highly correlated (p<0.0001). iPV treatment was more effective compared to both untreated control and iv treatment (p<0.01 and p<0.05, respectively with iPV treatment with S. typhimurium arresting metastatic growth). There were no significant differences in body weight between all groups. The results of this study suggest that S. typhimurium A1-R administered iPV has potential for peri-operative adjuvant treatment of colon cancer liver metastasis.

Designer bacteria as intratumoural enzyme biofactories

Bacterial-directed enzyme prodrug therapy (BDEPT) is an emerging form of treatment for cancer. It is a biphasic variant of gene therapy in which a bacterium, armed with an enzyme that can convert an inert prodrug into a cytotoxic compound, induces tumour cell death following tumour-specific prodrug activation. BDEPT combines the innate ability of bacteria to selectively proliferate in tumours, with the capacity of prodrugs to undergo contained, compartmentalised conversion into active metabolites in vivo. Although BDEPT has undergone clinical testing, it has received limited clinical exposure, and has yet to achieve regulatory approval. In this article, we review BDEPT from the system designer's perspective, and provide detailed commentary on how the designer should strategize its development de novo. We report on contemporary advancements in this field which aim to enhance BDEPT in terms of safety and efficacy. Finally, we discuss clinical and regulatory barriers facing BDEPT, and propose promising approaches through which these hurdles may best be tackled.

New Combination Strategies Using Programmed Cell Death 1/Programmed Cell Death Ligand 1 Checkpoint Inhibitors as a Backbone

The discovery of immune checkpoints and subsequent clinical development of checkpoint inhibitors have revolutionized the field of oncology. The durability of the antitumor immune responses has raised the hope for long-term patient survival and potential cure; however, currently, only a minority of patients respond. Combination strategies to help increase antigen release and T-cell priming, promote T-cell activation and homing, and improve the tumor immune microenvironment, all guided by predictive biomarkers, can help overcome the tumor immune-evasive mechanisms and maximize efficacy to ultimately benefit the majority of patients. Great challenges remain because of the complex underlying biology, unpredictable toxicity, and accurate assessment of response. Carefully designed clinical trials guided by translational studies of paired biopsies will be key to develop reliable predictive biomarkers to choose which patients would most likely benefit from each strategy.

The HPV E6/E7 Oncogenes: Key Factors for Viral Carcinogenesis and Therapeutic Targets

Human papillomavirus (HPV)-induced cancers are expected to remain a major health problem worldwide for decades. The growth of HPV-positive cancer cells depends on the sustained expression of the viral E6 and E7 oncogenes which act in concert with still poorly defined cellular alterations. E6/E7 constitute attractive therapeutic targets since E6/E7 inhibition rapidly induces senescence in HPV-positive cancer cells. This cellular response is linked to the reconstitution of the antiproliferative p53 and pRb pathways, and to prosenescent mTOR signaling. Hypoxic HPV-positive cancer cells could be a major obstacle for treatment strategies targeting E6/E7 since they downregulate E6/E7 but evade senescence through hypoxia-induced mTOR impairment. Prospective E6/E7 inhibitors may therefore benefit from a combination with treatment strategies directed against hypoxic tumor cells.

d-Retroenantiomer of Quorum-Sensing Peptide-Modified Polymeric Micelles for Brain Tumor-Targeted Drug Delivery

Compared to that of other tumors, various barriers, such as the blood-brain barrier (BBB), enzymatic barriers, and the blood-brain tumor barrier, severely impede the successful treatment of gliomas. Peptide ligands were frequently used as targeting moieties to mediate brain tumor-targeted drug delivery. ^LWSW (SYPGWSW) is a recently reported quorum-sensing (QS) peptide that is able to efficiently cross the BBB. Even though linear ^LWSW traverses the BBB in vitro, its in vivo targeting ability has been greatly impaired due to proteolysis. Here, we developed a stable peptide, ^DWSW (^DW^DS^DW^DG^DP^DY^DS), using the retro-inverso isomerization technique to achieve an enhanced antiglioma effect. In vitro studies have demonstrated that both the ^LWSW and ^DWSW peptides possessed excellent tumor-homing properties and barrier-penetration abilities, whereas ^DWSW exhibited exceptional stability in serum and maintained its targeting ability after serum preincubation. In vivo, ^DWSW-modified probes and micelles accumulated more efficiently in the glioma region in comparison with ^LWSW-modified probes and micelles because of full resistance to proteolysis in blood circulation. As expected, ^DWSW-modified paclitaxel (PTX)-loaded micelles (^DWSW Micelle/PTX) exhibited the longest median survival time among glioma-bearing nude mice. Our results suggested that the QS peptide appears to be a promising targeting moiety, with potential applications in glioma-targeted drug delivery.

Tumour-targeting bacteria-based cancer therapies for increased specificity and improved outcome

‘You have cancer’ – a devastating diagnosis that still strikes patients hard. Despite substantial improvements of standard therapies over the years, there is still no general cure available. Here, we review the revival of an old concept – the use of bacteria as cancer therapeutics. Bacteria‐mediated tumor therapy has great potential to evolve into a powerful tool against malignant solid tumors.

Protein Secretion in Gram-Positive Bacteria: From Multiple Pathways to Biotechnology

A number of Gram-positive bacteria are important players in industry as producers of a diverse array of economically interesting metabolites and proteins. As discussed in this overview, several Gram-positive bacteria are valuable hosts for the production of heterologous proteins. In contrast to Gram-negative bacteria, proteins secreted by Gram-positive bacteria are released into the culture medium where conditions for correct folding are more appropriate, thus facilitating the isolation and purification of active proteins. Although seven different protein secretion pathways have been identified in Gram-positive bacteria, the majority of heterologous proteins are produced via the general secretion or Sec pathway. Not all proteins are equally well secreted, because heterologous protein production often faces bottlenecks including hampered secretion, susceptibility to proteases, secretion stress, and metabolic burden. These bottlenecks are associated with reduced yields leading to non-marketable products. In this chapter, besides a general overview of the different protein secretion pathways, possible hurdles that may hinder efficient protein secretion are described and attempts to improve yield are discussed including modification of components of the Sec pathway. Attention is also paid to omics-based approaches that may offer a more rational approach to optimize production of heterologous proteins.

Virus/Host Cell Crosstalk in Hypoxic HPV-Positive Cancer Cells

Oncogenic types of human papillomaviruses (HPVs) are major human carcinogens. The expression of the viral E6/E7 oncogenes plays a key role for HPV-linked oncogenesis. It recently has been found that low oxygen concentrations (“hypoxia”), as present in sub-regions of HPV-positive cancers, strongly affect the interplay between the HPV oncogenes and their transformed host cell. As a result, a state of dormancy is induced in hypoxic HPV-positive cancer cells, which is characterized by a shutdown of viral oncogene expression and a proliferative arrest that can be reversed by reoxygenation. In this review, these findings are put into the context of the current concepts of both HPV-linked carcinogenesis and of the effects of hypoxia on tumor biology. Moreover, we discuss the consequences for the phenotype of HPV-positive cancer cells as well as for their clinical behavior and response towards established and prospective therapeutic strategies.

Exosomes from Plasmodium-infected hosts inhibit tumor angiogenesis in a murine Lewis lung cancer model

Previous research to investigate the interaction between malaria infection and tumor progression has revealed that malaria infection can potentiate host immune response against tumor in tumor-bearing mice. Exosomes may play key roles in disseminating pathogenic host-derived molecules during infection because several studies have shown the involvement and roles of extracellular vesicles in cell–cell communication. However, the role of exosomes generated during Plasmodium infection in tumor growth, progression and angiogenesis has not been studied either in animals or in the clinics. To test this hypothesis, we designed an animal model to generate and isolate exosomes from mice which were subsequently used to treat the tumor. Intra-tumor injection of exosomes derived from the plasma of Plasmodium-infected mice provided significantly reduced Lewis lung cancer growth in mice. We further co-cultured the isolated exosomes with endothelial cells and observed significantly reduced expression of VEGFR2 and migration in the endothelial cells. Interestingly, high level of micro-RNA (miRNA) 16/322/497/17 was detected in the exosomes derived from the plasma of mice infected with Plasmodium compared with those from control mice. We observed that overexpression of the miRNA 16/322/497/17 in endothelial cell corresponded with decreased expression of VEGFR2, inhibition of angiogenesis and inhibition of the miRNA 16/322/497/17 significantly alleviated these effects. These data provide novel scientific evidence of the interaction between Plasmodium infection and lung cancer growth and angiogenesis.

Anti-tumor activity of an immunotoxin (TGFα-PE38) delivered by attenuated Salmonella typhimurium

The anticancer strategy underlying the use of immunotoxins is as follows: the cancer-binding domain delivers the toxin to a cancer cell, after which the toxin enters and kills the cell. TGFα-PE38 is an immunotoxin comprising transforming growth factor alpha (TGFα), a natural ligand of epidermal growth factor receptor (EGFR), and a modified Pseudomonas exotoxin A (PE38) lacking N terminal cell-binding domain, a highly potent cytotoxic protein moiety. Tumor cells with high level of EGFR undergo apoptosis upon treatment with TGFα-PE38. However, clinical trials demonstrated that this immunotoxin delivered by an intracerebral infusion technique has only a limited inhibitory effect on intracranial tumors mainly due to inconsistent drug delivery. To circumvent this problem, we turned to tumor-seeking bacterial system. Here, we engineered Salmonella typhimurium to selectively express and release TGFα-PE38. Engineered bacteria were administered to mice implanted with mouse colon or breast tumor cells expressing high level of EGFR. We observed that controlled expression and release of TGFα-PE38 from intra-tumoral Salmonellae by either an engineered phage lysis system or by a bacterial membrane transport signal led to significant inhibition of solid tumor growth. These results demonstrated that delivery by tumor-seeking bacteria would greatly augment efficacy of immunotoxin in cancer therapeutics.