Coley's toxin revisited: immunotherapy or plasminogen activator therapy of cancer?

ThermomiR-377-3p-induced suppression of Cirbp expression is required for effective elimination of cancer cells and cancer stem-like cells by hyperthermia

BACKGROUND

In recent years, the development of adjunctive therapeutic hyperthermia for cancer therapy has received considerable attention. However, the mechanisms underlying hyperthermia resistance are still poorly understood. In this study, we investigated the roles of cold‑inducible RNA binding protein (Cirbp) in regulating hyperthermia resistance and underlying mechanisms in nasopharyngeal carcinoma (NPC).

METHODS

CCK-8 assay, colony formation assay, tumor sphere formation assay, qRT-PCR, Western blot were employed to examine the effects of hyperthermia (HT), HT + oridonin(Ori) or HT + radiotherapy (RT) on the proliferation and stemness of NPC cells. RNA sequencing was applied to gain differentially expressed genes upon hyperthermia. Gain-of-function and loss-of-function experiments were used to evaluate the effects of RNAi-mediated Cirbp silencing or Cirbp overexpression on the sensitivity or resistance of NPC cells and cancer stem-like cells to hyperthermia by CCK-8 assay, colony formation assay, tumorsphere formation assay and apoptosis assay, and in subcutaneous xenograft animal model. miRNA transient transfection and luciferase reporter assay were used to demonstrate that Cirbp is a direct target of miR-377-3p. The phosphorylation levels of key members in ATM-Chk2 and ATR-Chk1 pathways were detected by Western blot.

RESULTS

Our results firstly revealed that hyperthermia significantly attenuated the stemness of NPC cells, while combination treatment of hyperthermia and oridonin dramatically increased the killing effect on NPC cells and cancer stem cell (CSC)‑like population. Moreover, hyperthermia substantially improved the sensitivity of radiation‑resistant NPC cells and CSC‑like cells to radiotherapy. Hyperthermia noticeably suppressed Cirbp expression in NPC cells and xenograft tumor tissues. Furthermore, Cirbp inhibition remarkably boosted anti‑tumor‑killing activity of hyperthermia against NPC cells and CSC‑like cells, whereas ectopic expression of Cirbp compromised tumor‑killing effect of hyperthermia on these cells, indicating that Cirbp overexpression induces hyperthermia resistance. ThermomiR-377-3p improved the sensitivity of NPC cells and CSC‑like cells to hyperthermia in vitro by directly suppressing Cirbp expression. More importantly, our results displayed the significantly boosted sensitization of tumor xenografts to hyperthermia by Cirbp silencing in vivo, but ectopic expression of Cirbp almost completely counteracted hyperthermia-mediated tumor cell-killing effect against tumor xenografts in vivo. Mechanistically, Cirbp silencing-induced inhibition of DNA damage repair by inactivating ATM-Chk2 and ATR-Chk1 pathways, decrease in stemness and increase in cell death contributed to hyperthermic sensitization; conversely, Cirbp overexpression-induced promotion of DNA damage repair, increase in stemness and decrease in cell apoptosis contributed to hyperthermia resistance.

CONCLUSION

Taken together, these findings reveal a previously unrecognized role for Cirbp in positively regulating hyperthermia resistance and suggest that thermomiR-377-3p and its target gene Cirbp represent promising targets for therapeutic hyperthermia.

Recent advances in microbial toxin-related strategies to combat cancer

It is a major concern to treat cancer successfully, due to the distinctive pathophysiology of cancer cells and the gradual manifestation of resistance. Specific action, adverse effects and development of resistance has prompted the urgent requirement of exploring alternative anti-tumour treatment therapies. The naturally derived microbial toxins as a therapy against cancer cells are a promisingly new dimension. Various important microbial toxins such as Diphtheria toxin, Vibrio cholera toxin, Aflatoxin, Patulin, Cryptophycin-55, Chlorella are derived from several bacterial, fungal and algal species. These agents act on different biotargets such as inhibition of protein synthesis, reduction in cell growth, regulation of cell cycle and many cellular processes. Bacterial toxins produce actions primarily by targeting protein moieties and some immunomodulation and few acts through DNA. Fungal toxins appear to have more DNA damaging activity and affect the cell cycle. Algal toxins produce alteration in mitochondrial phosphorylation. In conclusion, microbial toxins and their metabolites appear to have a great potential to provide a promising option for the treatment and management to combat cancer.

Triggering of the immune response to MCF7 cell line using conjugated antibody with bacterial antigens: In-vitro and in-vivo study

The current study intended to trigger the immune response to cancer cells by using antibodies conjugated with bacterial antigens. The protein membrane of the MCF7 cell line was extracted and specific antibodies against cell membrane antigens was produced in rabbits. The specific antibodies were purified using chromatography methods and linked to E. coli antigens or doxorubicin using Diethylenetriamine pentaacetate (DTPA) linker. After confirmation of the conjugation process using SDS-PAGE and ATR-FTIR methods, the MCF7 and HUVEC cells were treated with various concentrations of the prepared conjugated antibodies along with human serum. The toxicity of each treatment against MCF7 and HUVEC cells was evaluated using the MTT assay. Also, polylactic acid scaffolds that contain 10×10⁴ MCF7 cells were surgically placed in the peritoneal cavity of the rats. After treatment of each group, induction of the inflammatory responses was evaluated on stained histological sections of the scaffolds. The lowest cytotoxic doses of the antigen conjugated-antibody, doxorubicin-conjugated-antibody was 4 and 1 μg/mL, respectively. Doxorubicin conjugated antibodies displayed greater toxicity on both MCF7 and HUVEC cells. The in vivo finding revealed that the inflammatory cells were significantly higher in treating animals with antigen conjugated-antibody. The current synthetic agent stimulated the serum toxicity and induced an inflammatory response to MCF7 cell lines. Targeting of the bacterial antigens on tumor sites by immune system elements, could limit the growth of the tumor cells.

Bacterially Synthesized Tellurium Nanorods for Elimination of Advanced Malignant Tumor by Photothermal Immunotherapy

Probiotic Escherichia coli Nissle 1917 (EcN) are employed as a bioreactor for intracellularly synthesizing tellurium nanorods (TeNRs) providing a biohybrid therapeutic platform (Te@EcN) for the elimination of advanced malignant tumor by photothermal immunotherapy. Te@EcN is found to possess superior photothermal property upon near-infrared irradiation, and can efficiently accumulate and retain in tumors, although EcN loses proliferation ability after the synthesis of TeNRs, thus inducing considerable immunogenic tumor cell death. Under co-stimulation by EcN acting as immunoadjuvants, maturation of dendritic cells and priming of cytotoxic T cells are largely promoted. In addition, Te@EcN can reprogram tumor-associated macrophages to ameliorate the immunosuppressive tumor microenvironment. Thus, tumor metastasis and recurrence can be efficiently suppressed. Most importantly, owing to the non-pathogenicity of probiotic EcN and their non-proliferative characteristics after TeNRs synthesis, Te@EcN is found to be rapidly metabolized and cleared from the normal tissues, showing very slight acute side effects in healthy mice even at a relatively high administration dose. Therefore, the proposed combined therapeutic strategy based on bacteria-synthesized TeNRs may find great potential in improving bacteria-mediated tumor therapy with increased antitumor efficacy and reduced toxicity.

Bibliometric analysis of toll-like receptor agonists associated with cancer therapy

BACKGROUND

Toll-like receptors (TLRs), a family of innate pattern-recognition receptors, have been exploited as a target for antitumor strategy. An increasing number of TLR agonists, serving as immunotherapeutics or vaccine adjuvants, were developed. This study aimed at exploring the status and trend of current researches on TLR agonists through bibliometric analysis.

METHODS

Original publications on TLR agonists were collected from the Web of Science Core Collection. Data were analyzed in terms of publication outputs, journals, countries, institutions, authors, co-authorship, co-citation, research hotspots, and evolution trends through VOSviewer and CiteSpace.

RESULTS

A total of 1914 TLR agonists-related articles, published in 612 academic journals between 2000 and 2019, were enrolled in the study. The Journal of Immunology published the most publications, followed by PLoS One and Blood. The USA that is in possession of the largest number of articles and the most extensive cooperators was the most leading country in this field. University of Minnesota ranked the first in terms of paper totality, but its average citations ranking was lower than University of Pennsylvania. Gudkov AV was the most productive author, whose team reported a TLR5 agonist that had radioprotective activity in mouse and primate models in 2008. The paper of Akira Shizuo, professor of Osaka University, was widely cited by international peers. The research trend of TLR agonists has undergone 3 periods: mechanisms of TLR signalings in immunotherapy (2000-2010), discovery of TLR agonists (2011-2014), application, therapeutic evaluation, and drug design of TLR agonists (2015-2019).

CONCLUSION

This study provides investigators a landscape of TLR agonists research from the perspective of bibliometrics.

The Role of Bacterial Superantigens in the Immune Response: From Biology to Cancer Treatment

Aims:

Encouraging results have been indicated preclinically and in patients using the bacterial superantigen. This review article intends to summarize the role of the superantigens that have been recently used in the treatment of cancer. In addition, the vector systems, including lentiviral vectors, adeno-associated vector systems and retroviral vectors that are increasingly being used in basic and applied research, were discussed. Most importantly, the new CRISPR technique has also been discussed in this literature review.

Discussion:

More successful therapies can be achieved by manipulating bacterial vector systems through incorporating genes related to the superantigens and cytokines. The products of SAg and cytokine genes contribute to the strong stimulation of the immune system against tumor cells. They bind to MHC II molecules as well as the V beta regions of TCR and lead to the production of IL2 and other cytokines, the activation of antigen-presenting cells and T lymphocytes. Additionally, superantigens can be used to eradicate tumor cells. Better results in cancer treatment can be achieved by transferring superantigen genes and subsequent strong immune stimulation along with other cancer immunotherapy agents.

Conclusion:

Superantigens induce the proliferation of T lymphocytes and antigen-presenting cells by binding to MHCII molecules and V beta regions in T cell receptors. Therefore, the presentation of tumor cell antigens is increased. Additionally, the production of important cytokines by T cells and APCs contributes to the stimulation of immune response against tumor cells. The manipulation of bacterial vector systems through incorporating genesrelated to SAgs and other immune response factors is a good strategy for the immune system stimulating and eradicating tumor cells along with other immunotherapy agents.

Genetically modified bacteria for targeted phototherapy of tumor

Live attenuated bacteria have been used as target vehicles for genetic therapy of malignant carcinoma because they can be reprogrammed by following simple genetic rules and have the ability to target tumor hypoxic region. In this research, noninvasive Escherichia coli (E. Coli) is genetically modified through the plasmid transfection to afford E. Coli(p) with overexpressed human catalase for catalyzing H₂O₂ into O₂ in the tumor site. The produced O₂ is consequently converted to cytotoxic ¹O₂ under near-infrared (NIR) light irradiation for photodynamic therapy. Chlorin e6 (Ce6) is chosen as the photosensitizer for its excellent photodynamic ability, and polydopamine (pDA) is employed to encapsulate Ce6 for its good biosafety, photothermal ability, and adhesion capacity with bacteria. Dopamine polymerizes in the presence of Ce6 to form pDA/Ce6, and then E. Coli(p) is coated with pDA/Ce6 to afford the final E. Coli(p)/pDA/Ce6. The obtained system is intravenously administrated for selective accumulation and replication in the hypoxic tumor. NIR light irradiation is introduced to enable photothermal and O₂-enhanced photodynamic therapy. On account of complementary combination, the system exhibits efficient antitumor effect in vitro and in vivo. Thus, the integration of genetically modified bacteria with pDA/Ce6 presents a promising application potential for precise tumor inhibition.

Nanomaterials-Mediated Immunomodulation for Cancer Therapeutics

Immunotherapy holds great promise in overcoming the limitations of conventional regimens for cancer therapeutics. There is growing interest among researchers and clinicians to develop novel immune-strategies for cancer diagnosis and treatment with better specificity and lesser adversity. Immunomodulation-based cancer therapies are rapidly emerging as an alternative approach that employs the host’s own defense mechanisms to recognize and selectively eliminate cancerous cells. Recent advances in nanotechnology have pioneered a revolution in the field of cancer therapy. Several nanomaterials (NMs) have been utilized to surmount the challenges of conventional anti-cancer treatments like cytotoxic chemotherapy, radiation, and surgery. NMs offer a plethora of exceptional features such as a large surface area to volume ratio, effective loading, and controlled release of active drugs, tunable dimensions, and high stability. Moreover, they also possess the inherent property of interacting with living cells and altering the immune responses. However, the interaction between NMs and the immune system can give rise to unanticipated adverse reactions such as inflammation, necrosis, and hypersensitivity. Therefore, to ensure a successful and safe clinical application of immunomodulatory nanomaterials, it is imperative to acquire in-depth knowledge and a clear understanding of the complex nature of the interactions between NMs and the immune system. This review is aimed at providing an overview of the recent developments, achievements, and challenges in the application of immunomodulatory nanomaterials (iNMs) for cancer therapeutics with a focus on elucidating the mechanisms involved in the interplay between NMs and the host’s immune system.

Developments in anticancer vaccination: budding new adjuvants

The immune system has a limited capacity to recognize and fight cells that become cancerous and in cancer patients, the immune system has to seek the right balance between cancer rejection and host-immunosupression. The tumor milieu builds a protective shell and tumor cells rapidly accumulate mutations that promote antigen variability and immune-escape. Therapeutic vaccination of cancer is a promising strategy the success of which depends on a powerful activation of the cells of the adaptive immune system specific for tumor-cell detection and killing (e.g. CD4+and CD8+T-cells). In the last decades, the search for novel adjuvants that enhance dendritic cell (DC) function and their ability to prime T-cells has flourished and some Toll-like receptor (TLR) agonists have long been known to be valid immune adjuvants. The implementation of TLR-synthetic agonists in clinical studies of cancer vaccination is replacing the initial use of microbial-derived products with some encouraging results. The purpose of this review is to summarize the latest discoveries of TLR-synthetic agonists with adjuvant potential in anti-cancer vaccination.

The role of bacterial toxins and spores in cancer therapy

Cancer is one of the leading causes of human death worldwide. Conventional anticancer therapies are ineffective in treating cancer patients due to various reasons. Thus, more effective and accessible alternative anticancer strategies have been evolved with time with high specificity towards tumor cells and with less or no adverse effects to normal cells. One such promising therapy is the use of bacterial toxins and spores to treat advanced solid tumors. Initially, Coley paved the way towards the bacterial anticancer therapy several decades ago and now it has emerged as a potential tool to eliminate tumor cells. Bacterial spores of obligate anaerobes exclusively germinate in the hypoxic/necrotic areas and not in the well-oxygenated areas of the body. This unique phenomenon has been exploited in using bacterial spores as a remedy for cancer. Bacterial toxins also play a significant role in either directly killing tumor cells or altering the cellular processes of the tumor cells which ultimately leads to the inhibition and regression of the solid tumor. With the advancement of molecular techniques, a number of genetically-modified non-pathogenic bacteria have been developed to use in bacterial anticancer strategies. Although promising results have shown so far, further investigations are required to ensure the efficacy and the safety of the bacterial spores and toxins in treating cancer.

Recent trends and advances in microbe-based drug delivery systems

Since more than a decade, pharmaceutical researchers endeavor to develop an effective, safe and target-specific drug delivery system to potentiate the therapeutic actions and reduce the side effects. The conventional drug delivery systems (DDSs) show the improvement in the lifestyle of the patients suffering from non-communicable diseases, autoimmune diseases but sometimes, drug resistance developed during the treatment is a major concern for clinicians to find an alternative and more advanced transport systems. Advancements in drug delivery facilitate the development of active carrier for targeted action with improved pharmacokinetic behavior. This review article focuses on microbe-based drug delivery systems to provide safe, non-toxic, site-specific targeted action with lesser side effects. Pharmaceutical researchers play a vital part in microbe-based drug delivery systems as a therapeutic agent and carrier. The properties of microorganisms like self-propulsion, in-situ production of therapeutics, penetration into the tumor cells, increase in immunity, etc. are of interest for development of highly effective delivery carrier. Lactococcus lactis is therapeutically helpful in Inflammatory Bowel Disease (IBD) and is under investigation of phase I clinical trial. Moreover, bacteria, anti-cancer oncolytic viruses, viral vectors (gene therapy) and viral immunotherapy are the attractive areas of biotechnological research. Virus acts as a distinctive candidate for imaging of tumor and accumulation of active in tumor. Graphical abstract Classification of microbe-based drug delivery system.

Bacteria-Driven Hypoxia Targeting for Combined Biotherapy and Photothermal Therapy

The facultative anaerobe Salmonella strain VNP20009 selectively colonizes into tumors following systemic injection due to its preference for the hypoxia in the tumor cores. However, the phase 1 clinical trial of VNP20009 has been terminated mainly due to its weak antitumor effects and exhibition of dose-dependent toxicity. Here, we leveraged the advantages of VNP20009 biotherapy together with polydopamine-mediated photothermal therapy in order to enhance the antitumor efficacy toward malignant melanoma. VNP20009 was coated with polydopamine via oxidation and self-polymerization, which was then injected into tumor-bearing mice via the tail vein. Polydopamine-coated VNP20009 targeted hypoxic areas of the solid tumors, and near-infrared laser irradiation of the tumors induced heating due to polydopamine. This combined approach eliminated the tumors without relapse or metastasis with only one injection and laser irradiation. More importantly, we found both VNP and pDA potentiate the therapeutic ability of each other, resulting in a superior anticancer effect.

Bioengineered and biohybrid bacteria-based systems for drug delivery

The use of bacterial cells as agents of medical therapy has a long history. Research that was ignited over a century ago with the accidental infection of cancer patients has matured into a platform technology that offers the promise of opening up new potential frontiers in medical treatment. Bacterial cells exhibit unique characteristics that make them well-suited as smart drug delivery agents. Our ability to genetically manipulate the molecular machinery of these cells enables the customization of their therapeutic action as well as its precise tuning and spatio-temporal control, allowing for the design of unique, complex therapeutic functions, unmatched by current drug delivery systems. Early results have been promising, but there are still many important challenges that must be addressed. We present a review of promises and challenges of employing bioengineered bacteria in drug delivery systems and introduce the biohybrid design concept as a new additional paradigm in bacteria-based drug delivery.

Acute Lymphoblastic Leukemia Presenting With Pancytopenia Followed by a 14-Month-Long Period of Transient Remission Possibly Supporting the Adrenal Hypothesis of Leukemogenesis

A small group of children with acute lymphoblastic leukemia (ALL) have a preleukemic phase of pancytopenia followed by a period of spontaneous remission before the diagnosis (pre-ALL). A 6-year-old girl presented with pancytopenia, fever, and myelodysplasia. Following transient remission pre-B ALL was diagnosed 14 months later. Clonal B-lineage blasts at the period of pancytopenia were identified retrospectively. The interval between pre-ALL and ALL-diagnosis was longer than previously reported. The infection was clinically severe and might have induced a significant endogenous corticosteroids production resulting in the long-lasting remission. The case supports the adrenal and the Coley's toxin hypothesis in leukemogenesis.

Suppositional area for the search of bacterial products for anticancer therapy

It is well-known that bacteria can produce compounds which show anticancer effects. In present time, it is impossible to check all bacterial species on their possible production of anticancer compounds (AC) under different conditions. Thus, it is necessary to limit the area for search of bacterial products for the anticancer therapy. We propose that production of AC by bacteria is a part of microbial biological strategy under natural conditions. We propose that bacteria in soils, in water and on plants do not meet human tumors and their AC serve for the competition with eukaryotic organisms. Most probably, an epiphytic growth of bacilli is accompanied with production of compounds inhibiting eukaryotes. According to awaited profit for the AC-producing bacteria, the epiphytic groups of bacilli show inhibition of mycelial fungi which are a natural model of eukaryotic cells. An example of strain isolation and a primary test is presented.

Bacteria in Cancer Therapy: Renaissance of an Old Concept

The rising incidence of cancer cases worldwide generates an urgent need of novel treatment options. Applying bacteria may represent a valuable therapeutic variant that is intensively investigated nowadays. Interestingly, the idea to apply bacteria wittingly or unwittingly dates back to ancient times and was revived in the 19th century mainly by the pioneer William Coley. This review summarizes and compares the results of the past 150 years in bacteria mediated tumor therapy from preclinical to clinical studies. Lessons we have learned from the past provide a solid foundation on which to base future efforts. In this regard, several perspectives are discussed by which bacteria in addition to their intrinsic antitumor effect can be used as vector systems that shuttle therapeutic compounds into the tumor. Strategic solutions like these provide a sound and more apt exploitation of bacteria that may overcome limitations of conventional therapies.

Staphylococcus aureus Enterotoxin B Down-Regulates the Expression of Transforming Growth Factor-Beta (TGF-β) Signaling Transducers in Human Glioblastoma

Background

It has been revealed that Staphylococcus aureus enterotoxin B (SEB) may feature anti-cancer and anti-metastatic advantages due to its ability to modify cell immunity processes and signaling pathways. Glioblastoma is one of the most aggressive human cancers; it has a high mortality nature, which makes it an attractive area for the development of novel therapies.

Objectives

We examined whether the SEB could exert its growth inhibitory effects on glioblastoma cells partially through the manipulation of a key tumor growth factor termed transforming growth factor-beta (TGF-β).

Materials and Methods

A human primary glioblastoma cell line, U87, was treated with different concentrations of SEB. The cell quantity was measured by the MTT assay at different exposure times. For molecular assessments, total ribonucleic acid (RNA) was extracted from either non-treated or SEB-treated cells. Subsequently, the gene expression of TGF-β transducers, smad2/3, at the messenger RNA (mRNA) level, was analyzed via a quantitative real-time polymerase chain reaction (qPCR) using the SYBR Green method. Significant differences between cell viability and gene expression levels were determined (Prism 5.0 software) using one-way analyses of variance (ANOVA) test.

Results

We reported that SEB could effectively down-regulate smad2/3 expression in glioblastoma cells at concentrations as quantity as 1 μg/mL and 2 μg/mL (P < 0.05 and P < 0.01, respectively). The SEB concentrations effective at regulating smad2/3 expression were correlated with those used to inhibit the proliferation of glioblastoma cells. Our results also showed that SEB was able to decrease smad2/3 expression at the mRNA level in a concentration- and time-dependent manner.

Conclusions

We suggested that SEB could represent an agent that can significantly decrease smad2/3 expression in glioblastoma cells, leading to moderate TGF-β growth signaling and the reduction of tumor cell proliferation.

Modulation of transforming growth factor‑β signaling transducers in colon adenocarcinoma cells induced by staphylococcal enterotoxin B

Colorectal cancer (CRC) is a notable cause of cancer‑associated mortality worldwide, making it a pertinent topic for the study of cancer and its treatment. Staphylococcal enterotoxin B (SEB), an enterotoxin produced by Staphylococcus aureus, has been demonstrated to exert anticancer and antimetastatic effects due to its ability to modify cell immunity and cellular signaling pathways. In the current study, SEB was investigated, including whether it exerts its growth inhibitory effects on colon adenocarcinoma cells. This may occur through the manipulation of a key tumor growth factor, termed transforming growth factor‑β (TGF‑β), and its signaling pathway transducer, Smad2/3. The human colon adenocarcinoma HCT116 cell line was treated with different concentrations of SEB, and cell number was measured using MTT assay at different treatment times. Smad2/3 RNA expression level was analyzed in untreated or SEB‑treated cells using quantitative polymerase chain reaction, which indicated significant differences between cell viability and Smad2/3 expression levels. SEB effectively downregulated Smad2/3 expression in the HCT116 cells at concentrations of 1 and 2 µg/ml (P=0.0021 and P=0.0017, respectively). SEB concentrations that were effective at inhibiting Smad2/3 expression were correlated with those able to inhibit the proliferation of the cancer cells. SEB inhibited Smad2/3 expression at the mRNA level in a concentration‑ and time‑dependent manner. The present study thus proposed SEB as an agent able to significantly reduce Smad2/3 expression in colon cancer cells, provoking moderate TGF‑β growth signaling and the reduction of tumor cell proliferation.

Injectable cryogel-based whole-cell cancer vaccines

A biomaterial-based vaccination system that uses minimal extracorporeal manipulation could provide in situ enhancement of dendritic cell (DC) numbers, a physical space where DCs interface with transplanted tumour cells, and an immunogenic context. Here we encapsulate GM-CSF, serving as a DC enhancement factor, and CpG ODN, serving as a DC activating factor, into sponge-like macroporous cryogels. These cryogels are injected subcutaneously into mice to localize transplanted tumour cells and deliver immunomodulatory factors in a controlled spatio-temporal manner. These vaccines elicit local infiltrates composed of conventional and plasmacytoid DCs, with the subsequent induction of potent, durable and specific anti-tumour T-cell responses in a melanoma model. These cryogels can be delivered in a minimally invasive manner, bypass the need for genetic modification of transplanted cancer cells and provide sustained release of immunomodulators. Altogether, these findings indicate the potential for cryogels to serve as a platform for cancer cell vaccinations.

Necrosis, and then stress induced necrosis-like cell death, but not apoptosis, should be the preferred cell death mode for chemotherapy: clearance of a few misconceptions

Cell death overarches carcinogenesis and is a center of cancer researches, especially therapy studies. There have been many nomenclatures on cell death, but only three cell death modes are genuine, i.e. apoptosis, necrosis and stress-induced cell death (SICD). Like apoptosis, SICD is programmed. Like necrosis, SICD is a pathological event and may trigger regeneration and scar formation. Therefore, SICD has subtypes of stress-induced apoptosis-like cell death (SIaLCD) and stress-induced necrosis-like cell death (SInLCD). Whereas apoptosis removes redundant but healthy cells, SICD removes useful but ill or damaged cells. Many studies on cell death involve cancer tissues that resemble parasites in the host patients, which is a complicated system as it involves immune clearance of the alien cancer cells by the host. Cancer resembles an evolutionarily lower-level organism having a weaker apoptosis potential and poorer DNA repair mechanisms. Hence, targeting apoptosis for cancer therapy, i.e. killing via SIaLCD, will be less efficacious and more toxic. On the other hand, necrosis of cancer cells releases cellular debris and components to stimulate immune function, thus counteracting therapy-caused immune suppression and making necrosis better than SIaLCD for chemo drug development.

Toll-like receptor agonists: a patent review (2011 - 2013)

INTRODUCTION

Toll-like receptors (TLRs) are a crucial part of the innate immunity and present the first line of defense against pathogens. In humans, there are ten TLRs, with TLR3, 7, 8 and 9 located in intracellular vesicles and the remaining expressed on the cell surface. These transmembrane protein receptors recognize a wide range of pathogen components. A large number of TLR agonists, either derived from pathogen components or modified synthetic molecules, were developed and investigated for their ability to stimulate an immune response.

AREAS COVERED

This review includes an updated summary (2011 - 2013) of TLR agonists that have been published in patent applications and/or progressed to clinical studies, with an emphasis on their chemical structure, immune response, prophylactic and therapeutic outcomes.

EXPERT OPINION

A number of factors have contributed to the design and development of TLR agonists such as solving the crystal structures of TLR bound to their ligands, improvements in our understanding of the signaling pathway activated after TLR stimulation and the identification of the native ligands of all human TLRs. Some of the TLR agonists have been approved for human use by the FDA while others have reached clinical studies in Phases I, II and III. Generally, immunotherapy based on TLR agonists is very promising for the prevention and/or treatment of several disorders including cancer, allergy and microbial infections. However, many TLR agonists were withdrawn from further studies as they either lacked efficacy or caused serious side effects.

Hyperthermia as adjunct to intravesical chemotherapy for bladder cancer

Nonmuscle invasive bladder cancer remains a very costly cancer to manage because of high recurrence rates requiring long-term surveillance and treatment. Emerging evidence suggests that adjunct and concurrent use of hyperthermia with intravesical chemotherapy after transurethral resection of bladder tumor further reduces recurrence risk and progression to advanced disease. Hyperthermia has both direct and immune-mediated cytotoxic effect on tumor cells including tumor growth arrest and activation of antitumor immune system cells and pathways. Concurrent heat application also acts as a sensitizer to intravesical chemotherapy agents. As such the ability to deliver hyperthermia to the focus of tumor while minimizing damage to surrounding benign tissue is of utmost importance to optimize the benefit of hyperthermia treatment. Existing chemohyperthermia devices that allow for more localized heat delivery continue to pave the way in this effort. Current investigational methods involving heat-activated drug delivery selectively to tumor cells using temperature-sensitive liposomes also offer promising ways to improve chemohyperthermia efficacy in bladder cancer while minimizing toxicity to benign tissue. This will hopefully allow more widespread use of chemohyperthermia to all bladder cancer patients, including metastatic bladder cancer.

Reevaluating the concept of treating experimental tumors with a mixed bacterial vaccine: Coley's Toxin

Several decades after Coley's initial work, we here systematically analyzed tumoricidal as well as immunostimulatory effects of the historical preparation Coley's Toxin (CT), a safe vaccine made of heat-inactivated S. pyogenes and S. marcescens. First, by performing in vitro analysis, established human pancreatic carcinoma cell lines responded with dose- and time-dependent growth inhibition. Effects were attributed to necrotic as well as apoptotic cell death as determined by increased Caspase 3/7 levels, raised numbers of cells with sub-G1-DNA, and induced p21^waf expression, indicative for cell cycle arrest. Besides, CT effectively stimulated human peripheral blood leukocytes (huPBL) from healthy volunteers. Quantitative gene expression analysis revealed upregulated mRNA levels of selected Toll-like receptors. Flow cytometric phenotyping of CT-stimulated huPBLs identified raised numbers of CD25⁺-activated leukocytes. In vivo, repetitive, local CT application was well tolerated by animals and induced considerable delay of Panc02 tumors. However, systemic treatment failed to affect tumor growth. Antitumoral effects following local therapy were primarily accompanied by stimulation of innate immune mechanisms. Data presented herein prove that the historical approach of using killed bacteria as active immunotherapeutic agents still holds promise, and further careful preclinical analyses may pave the way back into clinical applications.

Cytotoxicity of bacterial metabolic products, including listeriolysin O, on leukocyte targets

Bacterial toxins can exhibit anticancer activities. Here we investigated the anticancer effects of the listeriolysin O toxin produced by Listeria monocytogenes. We found that supernatants of Listeria monocytogenes strains (wild type, 1189, and 1190) were cytotoxic to the Jurkat cell line and human peripheral blood mononuclear cells (PBMC) in a concentration-dependent manner. The supernatant of strain 1044, not producing listeriolysin O, was inactive. The supernatants of Listeria strains were also cytotoxic toward B cells of chronic leukemia patients, with no significant differences in activities between strains. We also tested supernatants of Bacillus subtilis strains BR1-90, BR1-S, and BR1-89 producing listeriolysin O. BR1-S and BR1-89 were cytotoxic to PBMC and to Jurkat cells, the latter being more sensitive to the supernatants. BR1-90 was not hemolytic or cytotoxic to PBMC, but was cytotoxic to Jurkat cells in the concentration range of 10–30%, suggesting that listeriolysin O is selectively effective against T cells. Overall, the response of human peripheral blood mononuclear and human leukemia cell lines to bacteria supernatants containing listeriolysin O depended on the bacteria strain, target cell type, and supernatant concentration.

Fever in Cancer Treatment: Coley's Therapy and Epidemiologic Observations

In the fall of 1890, an athletic, self-possessed, and thoughtful 17-year-old girl, who had just returned from an adventurous trip to Alaska where she had hurt her hand in a trivial accident, went to see a young, innovative surgeon in his new practice in New York City. Barely out of Harvard Medical School, he was a rising star in New York surgical circles, and the young woman asked him for help with her poorly healing, swollen, and naggingly painful injury. This visit had a far-reaching effect on cancer research, American philanthropy, and the career of the young man, William Coley, MD (1862-1936, Figure 1). The patient, Elisabeth Dashiell, confidant and close friend of John D. Rockefeller, Jr, was diagnosed by Coley with a highly aggressive round cell sarcoma, and despite radical surgery and in spite of Coley's undoubtedly fine surgical skills and intensive care, a rapid progression of the cancer, immense suffering, and Elisabeth's death a few months later could not be prevented.

Bacterial immunotherapy of gastrointestinal tumors

Background

Cancer immunotherapy using bacteria dates back over 150 years. The deeper understanding on how the immune system interferes with the tumor microenvironment has led to the re-emergence of bacteria or their related products in immunotherapeutic concepts. In this review, we discuss recent approaches on experimental bacteriolytic therapy, emphasizing the specific interplay between bacteria, immune cells and tumor cells to break the tumor-induced tolerance.

Results

Experimental research during the last decades demonstrated beneficial but also adverse influence of bacteria on tumor growth. There is a strong correlation between chronic infections and tumor incidence. However, acute bacterial infections have favourable effects on tumor growth often contributing to complete remission. Tumor regression is usually attributable to both direct tumor cell killing (via apoptosis and/or necrosis, depending on the applied bacteria) and indirect immune stimulation. This includes (I) elimination of immunosuppressive immune cells (i.e. tumor-associated macrophages, myeloid-derived suppressor, and regulatory T cells), (II) suppression of Th2-directed cytokine secretion (TGFα, IL10), (III) providing a pro-inflammatory micro-milieu (tumor infiltrating neutrophils) and (IV) supporting the influx of cytotoxic T cells into tumors. This finally forces the development of an immunological memory and may provide long-term protection against cancer.

Conclusion

Immunotherapy using bacteria is still a double-edged sword. Experiences from the last years have substantially contributed to when bacteria and defined components thereof might be integrated into immunotherapeutic concepts. Attempts in transferring this approach into the clinics are on their way.

Avitalized bacteria mediate tumor growth control via activation of innate immunity

Acute bacterial infections have beneficial effects on tumor patients. To eliminate side effects evoked by viable microbes, we here assessed the immunotherapeutic potential of inactivated bacteria on colorectal carcinomas. Our In vitro results indicate a cell-specific direct cytotoxicity towards tumor cells presented by G1-arrest. Antitumoral activity was boosted in the presence of leukocytes. Long time stimulations revealed massive activation of NK cells even in complete autologous settings. In vivo, repetitive local treatment mediated tumor growth control. Evaluation of residual tumors identified increased infiltrates, with NK cells (CD49b(+), NKG2D(+)) being the main responding cell population. Substantial NK cell-mediated delay of tumor growth was also achieved in T-cell deficient mice xenografted with human colorectal carcinomas. Of note, local as well as systemic therapy mediated tumor growth control. These data highlight the potential of avitalized bacteria to especially activate the immune system's innate arm and they should be considered for future integrated immunotherapy.

Pseudomonas aeruginosa exotoxin A reduces chemoresistance of oral squamous carcinoma cell via inhibition of heat shock proteins 70 (HSP70)

PURPOSE

Oral squamous carcinoma (OSCC) cells exhibit resistance to chemotherapeutic agent-mediated apoptosis in the late stage of malignancy. Increased levels of heat shock proteins 70 (HSP70) in cancer cells are known to confer resistance to apoptosis. Since recent advances in the understanding of bacterial toxins have produced new strategies for the treatment of cancers, we investigated the effect of Pseudomonas aeruginosa exotoxin A (PEA) on HSP70 expression and induction of apoptosis in chemoresistant OSCC cell line (YD-9).

MATERIALS AND METHODS

The apoptotic effect of PEA on chemoresistant YD-9 cells was confirmed by MTT, Hoechst and TUNEL stains, DNA electrophoresis, and Western blot analysis.

RESULTS

While YD-9 cells showed high resistance to chemotherapeutic agents such as etoposide and 5-fluorouraci (5-FU), HSP70 antisense oligonucelotides sensitized chemoresistant YD-9 cells to etoposide and 5-FU. On the other hand, PEA significantly decreased the viability of YD-9 cells by deteriorating the HSP70-relating protecting system through inhibition of HSP70 expression and inducing apoptosis in YD-9 cells. Apoptotic manifestations were evidenced by changes in nuclear morphology, generation of DNA fragmentation, and activation of caspases. While p53, p21, and E2F-1 were upregulated, cdk2 and cyclin B were downregulated by PEA treatment, suggesting that PEA caused cell cycle arrest at the G2/M checkpoint.

CONCLUSION

Therefore, these results indicate that PEA reduced the chemoresistance through inhibition of HSP70 expression and also induced apoptosis in chemoresistant YD-9 cells.

Bacteria in cancer therapy: a novel experimental strategy

Resistance to conventional anticancer therapies in patients with advanced solid tumors has prompted the need of alternative cancer therapies. Moreover, the success of novel cancer therapies depends on their selectivity for cancer cells with limited toxicity to normal tissues. Several decades after Coley's work a variety of natural and genetically modified non-pathogenic bacterial species are being explored as potential antitumor agents, either to provide direct tumoricidal effects or to deliver tumoricidal molecules. Live, attenuated or genetically modified non-pathogenic bacterial species are capable of multiplying selectively in tumors and inhibiting their growth. Due to their selectivity for tumor tissues, these bacteria and their spores also serve as ideal vectors for delivering therapeutic proteins to tumors. Bacterial toxins too have emerged as promising cancer treatment strategy. The most potential and promising strategy is bacteria based gene-directed enzyme prodrug therapy. Although it has shown successful results in vivo yet further investigation about the targeting mechanisms of the bacteria are required to make it a complete therapeutic approach in cancer treatment.

Nosocomial infection of Serratia marcescens may induce a protective effect in monkeys exposed to Bacillus anthracis

This study was originally designed to collect data on the natural history of inhalational anthrax in a new nonhuman primate model. An uncontrollable event created a new experimental condition which allowed us to retrospectively evaluate the power of the innate immune system to protect from an aerosol exposure of B. anthracis. Five African green monkeys (AGMs) had intravenous catheters implanted. One catheter was accidentally pulled out, leaving four AGMs with catheters and one without. All were exposed, to multiple lethal doses of B. anthracis Ames strain. Blood was collected twice daily to evaluate bacteremia. The AGM with no catheter had blood drawn from a femoral vein and became bacteremic on Day 9; succumbed to inhalational anthrax on Day 10. The other four AGMs had S. marcescens contamination in the catheter; indicated by pure colonies grown from the blood. None of these AGMs showed clinical signs of illness, had B. anthracis or a detectable level of protective antigen in the bloodstream. It appears that the presence of S. marcescens may have induced a "Coley's toxin" effect in this experiment. The innate immune response may have protected the AGMs from a lethal inhalational dose of B. anthracis spores.

Bacteria and cancer: cause, coincidence or cure? A review

Research has found that certain bacteria are associated with human cancers. Their role, however, is still unclear. Convincing evidence links some species to carcinogenesis while others appear promising in the diagnosis, prevention or treatment of cancers. The complex relationship between bacteria and humans is demonstrated by Helicobacter pylori and Salmonella typhi infections. Research has shown that H. pylori can cause gastric cancer or MALT lymphoma in some individuals. In contrast, exposure to H. pylori appears to reduce the risk of esophageal cancer in others. Salmonella typhi infection has been associated with the development of gallbladder cancer; however S. typhi is a promising carrier of therapeutic agents for melanoma, colon and bladder cancers. Thus bacterial species and their roles in particular cancers appear to differ among different individuals. Many species, however, share an important characteristic: highly site-specific colonization. This critical factor may lead to the development of non-invasive diagnostic tests, innovative treatments and cancer vaccines.

Clostridium spores as anti-tumour agents

The successful treatment of cancer remains a huge challenge. Consequently, efforts are being made to develop alternative methods of tumour therapy. One of these is the use of live Clostridium species, based on the observation that obligatory anaerobic bacteria specifically colonize the hypoxic and necrotic regions that are present in solid tumours but normally absent in other parts of the body. Although past results have fuelled scepticism about its clinical use, recent promising findings emphasize the potential of Clostridium-directed tumour therapy. These recent developments are reviewed and the reintroduction of this tumour-targeting protein delivery system into clinical settings is discussed.