Pseudomonas Exotoxin Immunotoxins and Anti-Tumor Immunity: From Observations at the Patient's Bedside to Evaluation in Preclinical Models

Cadherin 17 Nanobody-Mediated Near-Infrared-II Fluorescence Imaging-Guided Surgery and Immunotoxin Delivery for Colorectal Cancer

Surgery and targeted therapy are of equal importance for colorectal cancer (CRC) treatment. However, complete CRC tumor resection remains challenging, and new targeted agents are also needed for efficient CRC treatment. Cadherin 17 (CDH17) is a membrane protein that is highly expressed in CRC and, therefore, is an ideal target for imaging-guided surgery and therapeutics. This study utilizes CDH17 nanobody (E8-Nb) with the near-infrared (NIR) fluorescent dye IRDye800CW to construct a NIR-II fluorescent probe, E8-Nb-IR800CW, and a Pseudomonas exotoxin (PE)-based immunotoxin, E8-Nb-PE38, to evaluate their performance for CRC imaging, imaging-guided precise tumor excision, and antitumor effects. Our results show that E8-Nb-IR800CW efficiently recognizes CDH17 in CRC cells and tumor tissues, produces high-quality NIR-II images for CRC tumors, and enables precise tumor removal guided by NIR-II imaging. Additionally, fluorescent imaging confirms the targeting ability and specificity of the immunotoxin toward CDH17-positive tumors, providing the direct visible evidence for immunotoxin therapy. E8-Nb-PE38 immunotoxin markedly delays the growth of CRC through the induction of apoptosis and immunogenic cell death (ICD) in multiple CRC tumor models. Furthermore, E8-Nb-PE38 combined with 5-FU exerts synergistically antitumor effects and extends survival. This study highlights CDH17 as a promising target for CRC imaging, imaging-guided surgery, and drug delivery. Nanobodies targeting CDH17 hold great potential to construct NIR-II fluorescent probes for surgery navigation, and PE-based toxins fused with CDH17 nanobodies represent a novel therapeutic strategy for CRC treatment. Further investigation is warranted to validate these findings for potential clinical translation.

In vitro and in vivo anti-tumor effect of Trichobakin fused with urokinase-type plasminogen activator ATF-TBK

BACKGROUND

Trichobakin (TBK), a member of type I ribosome-inactivating proteins (RIPs), was first successfully cloned from Trichosanthes sp Bac Kan 8-98 in Vietnam. Previous study has shown that TBK acts as a potential protein synthesis inhibitor; however, the inhibition efficiency and specificity of TBK on cancer cells remain to be fully elucidated.

METHODS AND RESULTS

In this work, we employed TBK and TBK conjugated with a part of the amino-terminal fragment (ATF) of the urokinase-type plasminogen activator (uPA), which contains the Ω-loop that primarily interacts with urokinase-type plasminogen activator receptor, and can be a powerful carrier in the drug delivery to cancer cells. Four different human tumor cell lines and BALB/c mice bearing Lewis lung carcinoma cells (LLC) were used to evaluate the role of TBK and ATF-TBK in the inhibition of tumor growth. Here we showed that the obtained ligand fused RIP (ATF-TBK) reduced the growth of four human cancer cell lines in vitro in the uPA receptor level-dependent manner, including the breast adenocarcinoma MDA-MB 231 cells and MCF7 cells, the prostate carcinoma LNCaP cells and the hepatocellular carcinoma HepG2 cells. Furthermore, the conjugate showed anti-tumor activity and prolonged the survival time of tumor-bearing mice. The ATF-TBK also did not cause the death of mice with doses up to 48 mg/kg, and they were not significantly distinct on parameters of hematology and serum biochemistry between the control and experiment groups.

CONCLUSIONS

In conclusion, ATF-TBK reduced the growth of four different human tumor cell lines and inhibited lung tumor growth in a mouse model with little side effects. Hence, the ATF-TBK may be a target to consider as an anti-cancer agent for clinical trials.

The Role of Antibody-Based Therapies in Neuro-Oncology

This review explores the evolving landscape of antibody-based therapies in neuro-oncology, in particular, immune checkpoint inhibitors and immunomodulatory antibodies. We discuss their mechanisms of action, blood-brain barrier (BBB) penetration, and experience in neuro-oncological conditions. Evidence from recent trials indicates that while these therapies can modulate the tumor immune microenvironment, their clinical benefits remain uncertain, largely due to challenges with BBB penetration and tumor-derived immunosuppression. This review also examines emerging targets such as TIGIT and LAG3, the potential of antibodies in modulating the myeloid compartment, and tumor-specific targets for monoclonal antibody therapy. We further delve into advanced strategies such as antibody-drug conjugates and bispecific T cell engagers. Lastly, we explore innovative techniques being investigated to enhance antibody delivery, including CAR T cell therapy. Despite current limitations, these therapies hold significant therapeutic potential for neuro-oncology. Future research should focus on optimizing antibody delivery to the CNS, identifying novel biological targets, and discovering combination therapies to address the hostile tumor microenvironment.

Recombinant immunotoxin induces tumor intrinsic STING signaling against head and neck squamous cell carcinoma

The innate immune stimulator of interferon genes (STING) pathway is known to activate type I interferons (IFN-I) and participate in generating antitumor immunity. We previously produced hDT806, a recombinant diphtheria immunotoxin, and demonstrated its efficacy against head and neck squamous cell carcinoma (HNSCC). However, it's unknown whether the tumor-intrinsic STING plays a role in the anti-HNSCC effects of hDT806. In this study, we investigated the innate immune modulation of hDT806 on HNSCC. hDT806 significantly upregulated the level of STING and the ratio of p-TBK1/TBK1 in the HNSCC cells. Moreover, intratumoral hDT806 treatment increased the expression of STING-IFN-I signaling proteins including IFNA1, IFNB, CXCL10 and MX1, a marker of IFN-I receptor activity, in the HNSCC xenografts. Overexpression of STING mimicked the hDT806-induced upregulation of the STING-IFN-I signaling and induced apoptosis in the HNSCC cells. In the mouse xenograft models of HNSCC with STING overexpression, we observed a significant suppression of tumor growth and reduced tumor weight with increased apoptosis compared to their control xenograft counterparts without STING overexpression. Collectively, our data revealed that hDT806 may act as a stimulator of tumor-intrinsic STING-IFN-I signaling to inhibit tumor growth in HNSCC.

Selective pks+ Escherichia coli strains induce cell cycle arrest and apoptosis in colon cancer cell line

pks+ Escherichia coli (E. coli) triggers genomic instability in normal colon cells which leads to colorectal cancer (CRC) tumorigenesis. Previously, we reported a significant presentation of pks+ E. coli strains in CRC patients' biopsies as compared to healthy cohorts. In this work, using an in vitro infection model, we further explored the ability of these strains in modulating cell cycle arrest and activation of apoptotic mediators in both primary colon epithelial cells (PCE) and CRC cells (HCT-116). Sixteen strains, of which eight tumours and the matching non-malignant tissues, respectively, from eight pks+ E. coli CRC patients were subjected to BrDU staining and cell cycle analysis via flow cytometry, while a subset of these strains underwent analysis of apoptotic mediators including caspase proteins, cellular reactive oxygen species (cROS) and mitochondrial membrane potential (MMP) via spectrophotometry as well as proinflammatory cytokines via flow cytometry. Data revealed that all strains exerted S-phase cell cycle blockade in both cells and G2/M phase in PCE cells only. Moreover, more significant upregulation of Caspase 9, cROS, proinflammatory cytokines and prominent downregulation of MMP were detected in HCT-116 cells indicating the potential role of pks related bacterial toxin as anticancer agent as compared to PCE cells which undergo cellular senescence leading to cell death without apparent upregulation of apoptotic mediators. These findings suggest the existence of discrepancies underlying the mechanism of action of pks+ E. coli on both cancer and normal cell lines. This work propounds the rationale to further understand the mechanism underlying pks+ E. coli-mediated CRC tumorigenesis and cancer killing.

Recent research and clinical progress of CTLA-4-based immunotherapy for breast cancer

Breast cancer is characterized by a high incidence rate and its treatment challenges, particularly in certain subtypes. Consequently, there is an urgent need for the development of novel therapeutic approaches. Immunotherapy utilizing immune checkpoint inhibitors (ICIs) is currently gaining momentum for the treatment of breast cancer. Substantial progress has been made in clinical studies employing cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) inhibitors for breast cancer, but the cure rates are relatively low. To improve the efficacy of CTLA-4-based therapy for breast cancer, further research is imperative to explore more effective immune-based treatment strategies. In addition to monotherapy, CTLA-4 inhibitors are also being investigated in combination with other ICIs or alternative medications. However, it should be noted that immune-based treatments may cause adverse events. This review focuses on the mechanisms of CTLA-4 inhibitor monotherapy or combination therapy in breast cancer. We systematically summarize the latest research and clinical advances in CTLA-4-based immunotherapy for breast cancer, providing new perspectives on the treatment of breast cancer. In addition, this review highlights the immune-related adverse events (irAEs) associated with CTLA-4 inhibitors, providing insights into the development of appropriate clinical tumor immunotherapy regimens and intervention strategies.

Manufacture and evaluation of a HER2-positive breast cancer immunotoxin 4D5Fv-PE25

BACKGROUND

Human epidermal growth factor receptor 2 (HER2) positive breast cancer is an aggressive subtype, accounting for around 20% of all breast cancers. The development of HER2-targeted therapy has substantially improved patient outcomes. Nevertheless, the increasing rate of side effects and resistance to targeted drugs limit their efficacy in clinical practice. In this study, we designed and synthesized a new immunotoxin, 4D5Fv-PE25, which targets HER2-positive breast cancer, and evaluated its effectiveness in vitro and in vivo.

RESULTS

The 4D5Fv-PE25 was expressed in high-density Escherichia coli (E. coli.) using the fermentor method and refined via hydrophobicity, ion exchange, and filtration chromatography, achieving a 56.06% recovery rate. Additionally, the semi-manufactured product with 96% purity was prepared into freeze-dried powder by the lyophilized process. Flow cytometry was used to detect the expression of HER2 in SK-BR-3, BT-474, MDA-MB-231, and MDA-MB-468 breast cancer cell lines. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) method was used for cytotoxicity assay, and the half-maximal inhibitory concentration (IC₅₀) of 4D5Fv-PE25 lyophilized products to HER2-positive cell line SK-BR-3 was 12.53 ng/mL. The 4D5Fv-PE25 was injected into xenograft tumor mice via the tail vein on the 1st, 4th, and 8th day, it indicated that the growth of tumor volume was effectively inhibited for 24 days, although the 4D5Fv-PE25 was metabolized within 60 min by measuring the release of 3 H-Thymidine radiation.

CONCLUSION

we succeeded in producing the 4D5Fv-PE25 freeze-dried powder using the prokaryotic expression method, and it could be employed as a potential drug for treating HER2-positive breast cancer.

Crotamine-based recombinant immunotoxin targeting HER2 for enhanced cancer cell specificity and cytotoxicity

Crotamine, one of the major toxins present in the venom of the South American rattlesnake Crotalus durissus terrificus, exhibits potent cytotoxic properties and has been suggested for cancer therapy applications. However, its selectivity for cancer cells needs to be improved. This study designed and produced a novel recombinant immunotoxin, HER2(scFv)-CRT, composed of crotamine and single-chain Fv (scFv) derived from trastuzumab targeting human epidermal growth factor receptor 2 (HER2). The recombinant immunotoxin was expressed in Escherichia coli and purified using various chromatographic techniques. The cytotoxicity of HER2(scFv)-CRT was assessed in three breast cancer cell lines, demonstrating enhanced specificity and toxicity in HER2-expressing cells. These findings suggest that the crotamine-based recombinant immunotoxin has the potential to expand the repertoire of recombinant immunotoxin applications in cancer therapy.

Targeting the Inside of Cells with Biologicals: Toxin Routes in a Therapeutic Context

Numerous toxins translocate to the cytosol in order to fulfil their function. This demonstrates the existence of routes for proteins from the extracellular space to the cytosol. Understanding these routes is relevant to multiple aspects related to therapeutic applications. These include the development of anti-toxin treatments, the potential use of toxins as shuttles for delivering macromolecular cargo to the cytosol or the use of drugs based on toxins. Compared with other strategies for delivery, such as chemicals as carriers for macromolecular delivery or physical methods like electroporation, toxin routes present paths into the cell that potentially cause less damage and can be specifically targeted. The efficiency of delivery via toxin routes is limited. However, low-delivery efficiencies can be entirely sufficient, if delivered cargoes possess an amplification effect or if very few molecules are sufficient for inducing the desired effects. This is known for example from RNA-based vaccines that have been developed during the coronavirus disease 2019 pandemic as well as for other approved RNA-based drugs, which elicited the desired effect despite their typically low delivery efficiencies. The different mechanisms by which toxins enter cells may have implications for their technological utility. We review the mechanistic principles of the translocation pathway of toxins from the extracellular space to the cytosol, the delivery efficiencies, and therapeutic strategies or applications that exploit toxin routes for intracellular delivery.

Gamma radiation coupled ADP-ribosyl transferase activity of Pseudomonas aeruginosa PE24 moiety

The ADP-ribosyl transferase activity of P. aeruginosa PE24 moiety expressed by E. coli BL21 (DE3) was assessed on nitrobenzylidene aminoguanidine (NBAG) and in vitro cultured cancer cell lines. Gene encoding PE24 was isolated from P. aeruginosa isolates, cloned into pET22b( +) plasmid, and expressed in E. coli BL21 (DE3) under IPTG induction. Genetic recombination was confirmed by colony PCR, the appearance of insert post digestion of engineered construct, and protein electrophoresis using sodium dodecyl-sulfate polyacrylamide gel (SDS-PAGE). The chemical compound NBAG has been used to confirm PE24 extract ADP-ribosyl transferase action through UV spectroscopy, FTIR, c¹³-NMR, and HPLC before and after low-dose gamma irradiation (5, 10, 15, 24 Gy). The cytotoxicity of PE24 extract alone and in combination with paclitaxel and low-dose gamma radiation (both 5 Gy and one shot 24 Gy) was assessed on adherent cell lines HEPG2, MCF-7, A375, OEC, and Kasumi-1 cell suspension. Expressed PE24 moiety ADP-ribosylated NBAG as revealed by structural changes depicted by FTIR and NMR, and the surge of new peaks at different retention times from NBAG in HPLC chromatograms. Irradiating recombinant PE24 moiety was associated with a reduction in ADP-ribosylating activity. The PE24 extract IC50 values were < 10 μg/ml with an acceptable R² value on cancer cell lines and acceptable cell viability at 10 μg/ml on normal OEC. Overall, the synergistic effects were observed upon combining PE24 extract with low-dose paclitaxel demonstrated by the reduction in IC50 whereas antagonistic effects and a rise in IC50 values were recorded after irradiation by low-dose gamma rays. KEY POINTS: • Recombinant PE24 moiety was successfully expressed and biochemically analyzed. • Low-dose gamma radiation and metal ions decreased the recombinant PE24 cytotoxic activity. • Synergism was observed upon combining recombinant PE24 with low-dose paclitaxel.

Fundamentals of utilizing microbes in advanced cancer therapeutics: Current understanding and potential applications

One of the biggest health related issues in the twenty-first century is cancer. The current therapeutic platforms have not advanced enough to keep up with the number of rising cases. The traditional therapeutic approaches frequently fail to produce the desired outcomes. Therefore, developing new and more potent remedies is crucial. Recently, investigating microorganisms as potential anti-cancer treatments have garnered a lot of attention. Tumor-targeting microorganisms are more versatile at inhibiting cancer than the majority of standard therapies. Bacteria preferentially gather and thrive inside tumors, where they can trigger anti-cancer immune responses. They can be further trained to generate and distribute anticancer drugs based on clinical requirements using straightforward genetic engineering approaches. To improve clinical outcomes, therapeutic strategies utilizing live tumor-targeting bacteria can be used either alone or in combination with existing anticancer treatments. On the other hand, oncolytic viruses that target cancer cells, gene therapy via viral vectors, and viral immunotherapy are other popular areas of biotechnological investigation. Therefore, viruses serve as a unique candidate for anti-tumor therapy. This chapter describes the role of microbes, primarily bacteria and viruses in anti-cancer therapeutics. The various approaches to utilizing microbes in cancer therapy are discussed and examples of microorganisms that are now in use or that are undergoing experimental research are briefly discussed. We further point out the hurdles and the prospects of microbes-based remedies for cancer treatment.

A recombinant Der p 1-specific allergen-toxin demonstrates superior killing of allergen-reactive IgG+ hybridomas in comparison to its recombinant allergen-drug conjugate

Introduction

Current treatments for asthma help to alleviate clinical symptoms but do not cure the disease. In this study, we explored a novel therapeutic approach for the treatment of house dust mite allergen Der p 1induced asthma by aiming to eliminate specific population of B-cells involved in memory IgE response to Der p 1.

Materials and Methods

To achieve this aim, we developed and evaluated two different proDer p 1-based fusion proteins; an allergen-toxin (proDer p 1-ETA) and an allergen-drug conjugate (ADC) (proDer p 1-SNAP-AURIF) against Der p 1 reactive hybridomas as an in vitro model for Der p 1 reactive human B-cells. The strategy involved the use of proDer p 1 allergen as a cell-specific ligand to selectively deliver the bacterial protein toxin Pseudomonas exotoxin A (ETA) or the synthetic small molecule toxin Auristatin F (AURIF) into the cytosol of Der p 1 reactive cells for highly efficient cell killing.

Results

As such, we demonstrated recombinant proDer p 1 fusion proteins were selectively bound by Der p 1 reactive hybridomas as well as primary IgG1⁺ B-cells from HDM-sensitized mice. The therapeutic potential of proDer p 1-ETA' and proDer p 1-SNAP-AURIF was confirmed by their selective cytotoxic activities on Der p 1 reactive hybridoma cells. The allergen-toxin demonstrated superior cytotoxic activity, with IC₅₀ values in the single digit nanomolar value, compared to the ADC.

Discussions

Altogether, the proof-of-concept experiments in this study provide a promising approach for the treatment of patients with house dust mite-driven allergic asthma.

Anti-mesothelin immunotoxin induces mesothelioma eradication, anti-tumor immunity, and the development of tertiary lymphoid structures

LMB-100 is a recombinant immunotoxin composed of a Fab linked to a toxin. It kills cells expressing human mesothelin (hMSLN), which is highly expressed on the surface of mesothelioma and many other cancer cells. Clinically, we observed some patients had delayed responses to an anti-hMSLN immunotoxin treatment, suggesting the induction of anti-tumor immunity. We aimed to develop a mouse model to investigate whether immunotoxin alone can induce anti-tumor immunity and to study the mechanism of this immunity. An immunocompetent transgenic mouse was used to grow mouse mesothelioma AB1 cells expressing hMSLN in the peritoneal cavity. Mice were treated with LMB-100, and mice with complete responses (CRs) were rechallenged with tumor cells to determine whether anti-tumor immunity developed. Changes in gene expression profiles were evaluated by Nanostring, and changes in cytokines and chemokines were checked by protein arrays. The distribution of various immune cells was assessed by immunohistochemistry. Our results show that the mice with tumor reached CRs and developed anti-tumor immunity after LMB-100 treatment alone. The primary response requires CD8⁺ T cells, CD4⁺ T cells, and B cells. Transcriptional profiling shows that LMB-100 treatment reshapes the tumor immune microenvironment by upregulating chemotaxis signals. LMB-100 treatment upregulates genes associated with tertiary lymphoid structures (TLS) development and induces TLS formation in tumors. In sum, immunotoxin-mediated cell death induces anti-tumor immunity and the development of TLS, which provides insights into how immunotoxins cause tumor regressions.

Microbial cancer therapeutics: A promising approach

The success of conventional cancer therapeutics is hindered by associated dreadful side-effects of antibiotic resistance and the dearth of antitumor drugs' selectivity and specificity. Hence, the conceptual evolution of anti-cancerous therapeutic agents that selectively target cancer cells without impacting the healthy cells or tissues, has led to a new wave of scientific interest in microbial-derived bioactive molecules. Such strategic solutions may pave the way to surmount the shortcomings of conventional therapies and raise the potential and hope for the cure of wide range of cancer in a selective manner. This review aims to provide a comprehensive summary of anti-carcinogenic properties and underlying mechanisms of bioactive molecules of microbial origin, and discuss the current challenges and effective therapeutic application of combinatorial strategies to attain minimal systemic side-effects.

EGFRvⅢ-targeted immunotoxin combined with temozolomide and bispecific antibody for the eradication of established glioblastoma

EGFRvⅢ is an established target for immunotherapy of glioblastoma (GBM). Current study aims to explore the efficacy of EGFRvⅢ-targeted immunotoxin combined with temozolomide (TMZ) or T cell-engaged bispecific antibody for the treatment of GBM. We generated three rabbit monoclonal antibodies (R1, R2, and R6) that specifically bound to EGFRvⅢ, but not EGFR, with high affinity. Immunotoxins were made by fusing the scFv of these antibodies with engineered Pseudomonas exotoxin PE24. The in vitro cytotoxicity and specificity of the immunotoxins was rigorously validated by EGFRvⅢ and EGFR-expressed cell lines. The in vivo efficacy of immunotoxin monotherapy and in combination with TMZ or EGFRvⅢ-targeted bispecific antibody was evaluated in orthotopic and subcutaneous xenograft mouse models. EGFRvⅢ immunotoxins potently killed U87, U251 and GL261 cells that were forcefully expressing EGFRvⅢ, with IC₅₀ values bellow 1.2 ng/ml. In a subcutaneous model, multiple intratumoral injections of immunotoxin at a dose of 2 mg/kg resulted in complete tumor regression in 3/5 of mice. In a C57BL/6 orthotopic glioblastoma model transplanted with GL261 cells that expressed a mouse version of EGFRvⅢ, two injections of 10 micrograms of immunotoxin in the lateral ventricles significantly improved the survival, with 2/5 mice being completely cured. Furthermore, in a subcutaneous xenograft model transplanted with EGFRvⅢ-expressed U87 cells, a single intratumoral injection of immuntoxin followed by i.v. injections of TMZ or EGFRvⅢ-targeted bispecific antibody achieved complete regression in mice. Taken together, EGFRvⅢ immunotoxin combined with TMZ or T cell-engaged bispecific antibody offers promise for curative treatment of GBM.

Bacteria-derived chimeric toxins as potential anticancer agents

Cancer is one of the major causes of death globally, requiring everlasting efforts to develop novel, specific, effective, and safe treatment strategies. Despite advances in recent years, chemotherapy, as the primary treatment for cancer, still faces limitations such as the lack of specificity, drug resistance, and treatment failure. Bacterial toxins have great potential to be used as anticancer agents and can boost the effectiveness of cancer chemotherapeutics. Bacterial toxins exert anticancer effects by affecting the cell cycle and apoptotic pathways and regulating tumorigenesis. Chimeric toxins, which are recombinant derivatives of bacterial toxins, have been developed to address the low specificity of their conventional peers. Through their targeting moieties, chimeric toxins can specifically and effectively detect and kill cancer cells. This review takes a comprehensive look at the anticancer properties of bacteria-derived toxins and discusses their potential applications as therapeutic options for integrative cancer treatment.

Intratumoral Microbiome of Human Primary Liver Cancer

Primary liver tumors (PLCs) and liver metastasis currently represent the leading cause of cancer-related deaths worldwide due to poor outcomes, high incidence, and postsurgical recurrence. Hence, novel diagnostic markers and therapeutic strategies for PLCs are urgently needed. The human microbiome can directly or indirectly impact cancer initiation, progression, and response to therapy, including cancer immunotherapy; however, the roles of the microbiota in the tumor microenvironment are not clear and require more investigation. Here, we investigated intratumoral microbial community profiling on formalin-fixed paraffin-embedded tissue samples of patients with PLC by 16S ribosomal RNA using the MiSeq platform. We characterized the microbial communities in different histopathological subtypes and in the different prognoses of patients with PLC. The study revealed microbial population differences not only in carcinoma tissue and the matched adjacent nontumor tissue but in different histopathological subtypes, even in patients with PLC with different prognoses. Interestingly, the abundance of certain bacteria that have antitumor effects at family and genus level, such as Pseudomonadaceae, decreased in tumor tissue and was linearly associated with prognosis of patients with PLC. Conclusion: We provide a potential novel diagnostic biomarker and therapeutic strategy for early clinical diagnosis and treatment of PLC.

Bacteria-based nanodrug for anticancer therapy

Bacteria-based immunotherapy has become a promising strategy to induce innate and adaptive responses for fighting cancer. The advantages of bacteriolytic tumor therapy mainly lie in stimulation of innate immunity and colonization of some bacteria targeting the tumor microenvironment (TME). These bacteria have cytotoxic proteins and immune modulating factors that can effectively restrain tumor growth. However, cancer is a multifactorial disease and single therapy is typically unable to eradicate tumors. Rapid progress has been made in combining bacteria with nanotechnology. Using the nanomolecular properties of bacterial products for tumor treatment preserves many features from the original bacteria while providing some unique advantages. Nano-bacterial therapy can enhance permeability and retention of drugs, increase the tolerability of the targeted drugs, promote the release of immune cell mediators, and induce immunogenic cell death pathways. In addition, combining nano-bacterial mediated antitumor therapeutic systems with modern therapy is an effective strategy for overcoming existing barriers in antitumor treatment and can achieve satisfactory therapeutic efficacy. Overall, exploring the immune antitumor characteristics of adjuvant clinical treatment with bacteria can provide potential efficacious treatment strategies for combatting cancer.

Bacteria therapeutics for cancer oncology: a crossroads for new paradigms

A promising treatment for cancer remains challenging owing to insufficient tumor targeting and predictable resistance. Current therapies have their drawbacks and there is a need for innovative treatment that can overcome all the limitations with the traditional approaches. One of the novel treatments is bacteria-mediated cancer therapy, which has shown a beneficial impact on tumor regression and metastasis inhibition. It can selectively target cancer cells and potentially serve as a therapeutic-gene-drug delivery approach. In their original form, genetically or chemically modified, or combined with conventional therapeutic approaches, bacteria produce safe and effective cancer with minimized cytotoxicity. This review discusses the key benefits, applicability and further implementations in the clinical translation of bacteriotherapy for cancer treatments.

Bacterial-Based Cancer Therapy (BBCT): Recent Advances, Current Challenges, and Future Prospects for Cancer Immunotherapy

Currently approximately 10 million people die each year due to cancer, and cancer is the cause of every sixth death worldwide. Tremendous efforts and progress have been made towards finding a cure for cancer. However, numerous challenges have been faced due to adverse effects of chemotherapy, radiotherapy, and alternative cancer therapies, including toxicity to non-cancerous cells, the inability of drugs to reach deep tumor tissue, and the persistent problem of increasing drug resistance in tumor cells. These challenges have increased the demand for the development of alternative approaches with greater selectivity and effectiveness against tumor cells. Cancer immunotherapy has made significant advancements towards eliminating cancer. Our understanding of cancer-directed immune responses and the mechanisms through which immune cells invade tumors have extensively helped us in the development of new therapies. Among immunotherapies, the application of bacteria and bacterial-based products has promising potential to be used as treatments that combat cancer. Bacterial targeting of tumors has been developed as a unique therapeutic option that meets the ongoing challenges of cancer treatment. In comparison with other cancer therapeutics, bacterial-based therapies have capabilities for suppressing cancer. Bacteria are known to accumulate and proliferate in the tumor microenvironment and initiate antitumor immune responses. We are currently well-informed regarding various methods by which bacteria can be manipulated by simple genetic engineering or synthetic bioengineering to induce the production of anti-cancer drugs. Further, bacterial-based cancer therapy (BBCT) can be either used as a monotherapy or in combination with other anticancer therapies for better clinical outcomes. Here, we review recent advances, current challenges, and prospects of bacteria and bacterial products in the development of BBCTs.

Pseudomonas Exotoxin-Based Immunotoxins: Over Three Decades of Efforts on Targeting Cancer Cells With the Toxin

Cancer is one of the prominent causes of death worldwide. Despite the existence of various modalities for cancer treatment, many types of cancer remain uncured or develop resistance to therapeutic strategies. Furthermore, almost all chemotherapeutics cause a range of side effects because they affect normal cells in addition to malignant cells. Therefore, the development of novel therapeutic agents that are targeted specifically toward cancer cells is indispensable. Immunotoxins (ITs) are a class of tumor cell-targeted fusion proteins consisting of both a targeting moiety and a toxic moiety. The targeting moiety is usually an antibody/antibody fragment or a ligand of the immune system that can bind an antigen or receptor that is only expressed or overexpressed by cancer cells but not normal cells. The toxic moiety is usually a protein toxin (or derivative) of animal, plant, insect, or bacterial origin. To date, three ITs have gained Food and Drug Administration (FDA) approval for human use, including denileukin diftitox (FDA approval: 1999), tagraxofusp (FDA approval: 2018), and moxetumomab pasudotox (FDA approval: 2018). All of these ITs take advantage of bacterial protein toxins. The toxic moiety of the first two ITs is a truncated form of diphtheria toxin, and the third is a derivative of Pseudomonas exotoxin (PE). There is a growing list of ITs using PE, or its derivatives, being evaluated preclinically or clinically. Here, we will review these ITs to highlight the advances in PE-based anticancer strategies, as well as review the targeting moieties that are used to reduce the non-specific destruction of non-cancerous cells. Although we tried to be as comprehensive as possible, we have limited our review to those ITs that have proceeded to clinical trials and are still under active clinical evaluation.

The comparison of microbial communities in thyroid tissues from thyroid carcinoma patients

Thyroid carcinoma is a common endocrine organ cancer associated with abnormal hormone secretion, leading to the disorder of metabolism. The intestinal microbiota is vital to maintain digestive and immunologic homeostasis. The relevant information of the microbial community in the gut and thyroid, including composition, structure, and relationship, is unclear in thyroid carcinoma patients. A total of 93 samples from 25 patients were included in this study. The results showed that microbial communities existed in thyroid tissue; gut and thyroid had high abundance of facultative anaerobes from the Proteobacteria phyla. The microbial metabolism from the thyroid and gut may be affected by the thyroid carcinoma cells. The cooccurrence network showed that the margins of different thyroid tissues were unique areas with more competition; the stabilization of microcommunities from tissue and stool may be maintained by several clusters of species that may execute different vital metabolism processes dominantly that are attributed to the microenvironment of cancer.

Recombinant immunotoxins development for HER2-based targeted cancer therapies

Understanding the molecular mechanisms of cancer biology introduces targeted therapy as a complementary method along with other conventional therapies. Recombinant immunotoxins are tumor specific antibodies that their recognizing fragment is utilized for delivering modified toxins into tumor cells. These molecules have been considered as a targeted strategy in the treatment of human cancers. HER2 tumor biomarker is a transmembrane tyrosine kinase receptor that can be used for targeted therapies in the forms of anti-HER2 monoclonal antibodies, antibody-drug conjugates and immunotoxins. There have been many studies on HER2-based immunotoxins in recent years, however, little progress has been made in the clinical field which demanded more improvements. Here, we summarized the HER2 signaling and it's targeting using immunotherapeutic agents in human cancers. Then, we specifically reviewed anti-HER2 immunotoxins, and their strengths and drawbacks to highlight their promising clinical impact.

Immunotoxins and nanobody-based immunotoxins: review and update

Immunotoxins (ITs) are protein-based drugs that compose of targeting and cytotoxic moieties. After binding the IT to the specific cell-surface antigen, the IT internalises into the target cell and kills it. Targeting and cytotoxic moieties usually include monoclonal antibodies and protein toxins with bacterial or plant origin, respectively. ITs have been successful in haematologic malignancies treatment. However, ITs penetrate poorly into solid tumours because of their large size. Use of camelid antibody fragments known as nanobodies (Nbs) as a targeting moiety may overcome this problem. Nbs are the smallest fragment of antibodies with excellent tumour tissue penetration. The ability to recognise cryptic (immuno-evasive) target antigens, low immunogenicity, and high-affinity are other fundamental characteristics of Nbs that make them suitable candidates in targeted therapy. Here, we reviewed and discussed the structure and function of ITs, Nbs, and nanobody-based ITs. To gain sound insight into the issue at hand, we focussed on nanobody-based ITs.

Modified RANO, Immunotherapy RANO, and Standard RANO Response to Convection-Enhanced Delivery of IL4R-Targeted Immunotoxin MDNA55 in Recurrent Glioblastoma

PURPOSE

The current study compared the standard response assessment in neuro-oncology (RANO), immunotherapy RANO (iRANO), and modified RANO (mRANO) criteria as well as quantified the association between progression-free (PFS) and overall survival (OS) in an immunotherapy trial in recurrent glioblastoma (rGBM).

PATIENTS AND METHODS

A total of 47 patients with rGBM were enrolled in a prospective phase II convection-enhanced delivery of an IL4R-targeted immunotoxin (MDNA55-05, NCT02858895). Bidirectional tumor measurements were created by local sites and centrally by an independent radiologic faculty, then standard RANO, iRANO, and mRANO criteria were applied.

RESULTS

A total of 41 of 47 patients (mean age 56 ± 11.7) were evaluable for response. PFS was significantly shorter using standard RANO compared with iRANO (log-rank, P < 0.0001; HR = 0.3) and mRANO (P < 0.0001; HR = 0.3). In patients who died and had confirmed progression on standard RANO, no correlation was observed between PFS and OS (local, P = 0.47; central, P = 0.34). Using iRANO, a weak association was observed between confirmed PFS and OS via local site measurements (P = 0.017), but not central measurements (P = 0.18). A total of 24 of 41 patients (59%) were censored using iRANO and because they lacked confirmation of progression 3 months after initial progression. A strong correlation was observed between mRANO PFS and OS for both local (R2 = 0.66, P < 0.0001) and centrally determined reads (R2 = 0.57, P = 0.0007).

CONCLUSIONS

No correlation between radiographic PFS and OS was observed for standard RANO or iRANO, but a correlation was observed between PFS and OS using the mRANO criteria. Also, the iRANO criteria was difficult to implement due to need to confirm progression 3 months after initial progression, censoring more than half the patients.

Recent development and optimization of pseudomonas aeruginosa exotoxin immunotoxins in cancer therapeutic applications

Recombinant immunotoxins are fusion proteins composed of a peptide toxin and a specific targeting domain through genetic recombination. They are engineered to recognize disease-specific target receptors and kill the cell upon internalization. Full-sized monoclonal antibodies, smaller antibody fragments and ligands, such as a cytokine or a growth factor, have been commonly used as the targeting domain, while bacterial Pseudomonas aeruginosa exotoxin (PE) is the usual toxin fusion partner, due to its natural cytotoxicity and other unique advantages. PE-based recombinant immunotoxins have shown remarkable efficacy in the treatment of tumors and autoimmune diseases. At the same time, efforts are underway to address major challenges, including immunogenicity, nonspecific cytotoxicity and poor penetration, which limit their clinical applications. Recent strategies for structural optimization of PE-based immunotoxins, combined with mutagenesis approaches, have reduced the immunogenicity and non-specific cytotoxicity, thus increasing both their safety and efficacy. This review highlights novel insights and design concepts that were used to advance immunotoxins for the treatment of hematological and solid tumors and also presents future development prospect of PE-based recombinant immunotoxins that are expected to play an important role in cancer therapy.

Nanobody: a promising toolkit for molecular imaging and disease therapy

Nanobodies are the recombinant variable domains of heavy-chain-only antibodies, with many unique properties such as small size, excellent solubility, superior stability, quick clearance from blood, and deep tissue penetration. As a result, nanobodies have become a promising tool for the diagnosis and therapy of diseases. As imaging tracers, nanobodies allow an early acquisition of high-quality images, provide a comprehensive evaluation of the disease, and subsequently enable a personalized precision therapy. As therapeutic agents, nanobodies enable a targeted therapy by lesion-specific delivery of drugs and effector domains, thereby improving the specificity and efficacy of the therapy. Up to date, a wide variety of nanobodies have been developed for a broad range of molecular targets and have played a significant role in patients with a broad spectrum of diseases. In this review, we aim to outline the current state-of-the-art research on the nanobodies for medical applications and then discuss the challenges and strategies for their further clinical translation.

Obligate and facultative anaerobic bacteria in targeted cancer therapy: Current strategies and clinical applications

Traditional methods for cancer therapy, including radiotherapy, chemotherapy, and immunotherapy are characterized by inherent limitations. Bacteria-mediated tumor therapy is becoming a promising approach in cancer treatment due to the ability of obligate or facultative anaerobic microorganisms to penetrate and proliferate in hypoxic regions of tumors. It is widely known that anaerobic bacteria cause the regression of tumors and inhibition of metastasis through a variety of mechanisms, including toxin production, anaerobic lifestyle and synergy with anti-cancer drugs. These features have the potential to be used as a supplement to conventional cancer treatment. To the best of our knowledge, no reports have been published regarding the most common tumor-targeting bacterial agents with special consideration of obligate anaerobes (such as Clostridium sp., Bifidobacterium sp.) and facultative anaerobes (including Salmonella sp., Listeria monocytogenes, Lactobacillus sp., Escherichia coli, Corynebacterium diphtheriae and Pseudomonas sp). In this review, we summarize the latest literature on the role of these bacteria in cancer treatment.

Targeted Therapy With Immunoconjugates for Multiple Myeloma

The introduction of proteasome inhibitors (PI) and immunomodulatory drugs (IMiD) has markedly increased the survival of multiple myeloma (MM) patients. Also, the unconjugated monoclonal antibodies (mAb) daratumumab (anti-CD38) and elotuzumab (anti-SLAMF7) have revolutionized MM treatment given their clinical efficacy and safety, illustrating the potential of targeted immunotherapy as a powerful treatment strategy for MM. Nonetheless, most patients eventually develop PI-, IMiD-, and mAb-refractory disease because of the selection of resistant MM clones, which associates with a poor prognosis. Accordingly, these patients remain in urgent need of new therapies with novel mechanisms of action. In this respect, mAbs or mAb fragments can also be utilized as carriers of potent effector moieties to specifically target surface antigens on cells of interest. Such immunoconjugates have the potential to exert anti-MM activity in heavily pretreated patients due to their distinct and pleiotropic mechanisms of action. In addition, the fusion of highly cytotoxic compounds to mAbs decreases the off-target toxicity, thereby improving the therapeutic window. According to the effector moiety, immunoconjugates are classified into antibody-drug conjugates, immunotoxins, immunocytokines, or radioimmunoconjugates. This review will focus on the mechanisms of action, safety and efficacy of several promising immunoconjugates that are under investigation in preclinical and/or clinical MM studies. We will also include a discussion on combination therapy with immunoconjugates, resistance mechanisms, and future developments.

Development of ImmTOR Tolerogenic Nanoparticles for the Mitigation of Anti-drug Antibodies

The development of anti-drug antibodies (ADAs) is a common cause for treatment failure and hypersensitivity reactions for many biologics. The focus of this review is the development of ImmTOR, a platform technology designed to prevent the formation of ADAs that can be applied broadly across a wide variety of biologics by inducing immunological tolerance with ImmTOR nanoparticles encapsulating rapamycin. The induction of tolerance is antigen-specific and dependent on the incorporation of rapamycin in nanoparticles and the presence of the antigen at the time of administration of ImmTOR. Evidence for the induction of specific immune tolerance vs. general immune suppression is supported by the findings that: (1) ImmTOR induces regulatory T cells specific to the co-administered antigen; (2) tolerance can be transferred by adoptive transfer of splenocytes from treated animals to naïve recipients; (3) the tolerance is durable to subsequent challenge with antigen alone; and (4) animals tolerized to a specific antigen are capable of responding to an unrelated antigen. ImmTOR nanoparticles can be added to new or existing biologics without the need to modify or reformulate the biologic drug. The ability of ImmTOR to mitigate the formation of ADAs has been demonstrated for coagulation factor VIII in a mouse model of hemophilia A, an anti-TNFα monoclonal antibody in a mouse model of inflammatory arthritis, pegylated uricase in hyperuricemic mice and in non-human primates, acid alpha-glucosidase in a mouse model of Pompe disease, recombinant immunotoxin in a mouse model of mesothelioma, and adeno-associated vectors in a model of repeat dosing of gene therapy vectors in mice and in non-human primates. Human proof-of concept for the mitigation of ADAs has been demonstrated with SEL-212, a combination product consisting of ImmTOR + pegadricase, a highly immunogenic enzyme therapy for the treatment of gout. ImmTOR represents a promising approach to preventing the formation of ADAs to a broad range of biologic drugs.

Actinoporins: From the Structure and Function to the Generation of Biotechnological and Therapeutic Tools

Actinoporins (APs) are a family of pore-forming toxins (PFTs) from sea anemones. These biomolecules exhibit the ability to exist as soluble monomers within an aqueous medium or as constitutively open oligomers in biological membranes. Through their conformational plasticity, actinoporins are considered good candidate molecules to be included for the rational design of molecular tools, such as immunotoxins directed against tumor cells and stochastic biosensors based on nanopores to analyze unique DNA or protein molecules. Additionally, the ability of these proteins to bind to sphingomyelin (SM) facilitates their use for the design of molecular probes to identify SM in the cells. The immunomodulatory activity of actinoporins in liposomal formulations for vaccine development has also been evaluated. In this review, we describe the potential of actinoporins for use in the development of molecular tools that could be used for possible medical and biotechnological applications.

Near-Infrared Light-Enhanced Protease-Conjugated Gold Nanorods As A Photothermal Antimicrobial Agent For Elimination Of Exotoxin And Biofilms

Purpose

Treatment strategies to eliminate bacterial infections have long emphasized bacterial killing as a goal. However, bacteria secrete toxins that sustain chronic disease and dead cells release DNA that can promote the spread of antibiotic resistance even when viable cells are eradicated. Meanwhile, biofilms regulated by quorum-sensing system, protect bacteria and promote the development of antibiotic resistance. Thus, all of these factors underscore the need for novel antimicrobial therapeutic treatments as alternatives to traditional antibiotics. Here, a smart material was developed that incorporated gold nanorods and an adsorbed protease (protease-conjugated gold nanorods, PGs). When illuminated with near-infrared (NIR) light, PGs functioned to physically damage bacteria, prevent biofilm and exotoxin production, eliminate pre-existing biofilm and exotoxin, and inhibit bacterial quorum-sensing systems.

Methods

PGs were incubated with suspensions of Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria followed by exposure to 808-nm NIR laser irradiation. Bacterial viability was determined using a colony-forming unit assay followed by an exploration of cell-damage mechanisms using transmission electron microscopy, scanning electron microscopy, agarose gel electrophoresis, and SDS-PAGE. Quantification of biofilm mass was performed using crystal violet staining. A commercial enterotoxin ELISA kit was used to test inhibitory and degradative effects of PGs on secreted exotoxin.

Results

Use of the remote-controlled antibacterial system reduced surviving bacterial populations to 3.2% and 2.1% of untreated control numbers for E. coli and S. aureus, respectively, and inhibited biofilm formation and exotoxin secretion even in the absence of NIR radiation. However, enhanced degradation of existing biofilm and exotoxin was observed when PGs were used with NIR laser irradiation.

Conclusion

This promising new strategy achieved both the reduction of viable microorganisms and elimination of biofilm and exotoxin. Thus, this strategy addresses the long-ignored issue of persistence of bacterial residues that perpetuate chronic illness in patients even after viable bacteria have been eradicated.

Bacterial Proteinaceous Compounds With Multiple Activities Toward Cancers and Microbial Infection

In recent decades, cancer and multidrug resistance have become a worldwide problem, resulting in high morbidity and mortality. Some infectious agents like Streptococcus pneumoniae, Stomatococcus mucilaginous, Staphylococcus spp., E. coli. Klebsiella spp., Pseudomonas aeruginosa, Candida spp., Helicobacter pylori, hepatitis B and C, and human papillomaviruses (HPV) have been associated with the development of cancer. Chemotherapy, radiotherapy and antibiotics are the conventional treatment for cancer and infectious disease. This treatment causes damage in healthy cells and tissues, and usually triggers systemic side-effects, as well as drug resistance. Therefore, the search for new treatments is urgent, in order to improve efficacy and also reduce side-effects. Proteins and peptides originating from bacteria can thus be a promising alternative to conventional treatments used nowadays against cancer and infectious disease. These molecules have demonstrated specific activity against cancer cells and bacterial infection; indeed, proteins and peptides can be considered as future antimicrobial and anticancer drugs. In this context, this review will focus on the desirable characteristics of proteins and peptides from bacterial sources that demonstrated activity against microbial infections and cancer, as well as their efficacy in vitro and in vivo.

Evaluating the influence of common antibiotics on the efficacy of a recombinant immunotoxin in tissue culture

OBJECTIVE

Recombinant immunotoxins (RITs) are antibody-toxin fusion proteins that can selectively eliminate populations of cells expressing specific surface receptors. They are in evaluation as therapeutic agents for cancer. RITs based on Pseudomonas exotoxin A (PE) are in use clinically for the treatment of hairy cell leukemia, and under trial for the treatment of other cancers. In an effort to improve the efficacy of PE-based RITs, we evaluated the potential of combination therapy with several common antibiotics (tetracycline, chloramphenicol, streptomycin, linezolid, fusidic acid, and kanamycin) on human cell lines HEK293, OVCAR8, and CA46. Antibiotics were selected based on their potential to inhibit mitochondrial protein synthesis and disrupt energy metabolism in cancer cells.

RESULTS

Tetracycline, chloramphenicol, linezolid, and fusidic acid alone killed cultured human cells at high concentrations. At high but nontoxic concentrations of each antibiotic, only chloramphenicol treatment of the Burkitt's lymphoma cell line CA46 showed enhanced cytotoxicity when paired with an anti-transferrin receptor/PE RIT. This result, however, could not be replicated in additional Burkitt's lymphoma cell lines Ramos and Raji. Although the six antibiotics we tested are not promising candidates for RIT combination therapy, we suggest that fusidic acid could be considered independently as a potential cancer therapeutic.