Phenotypic evolution of therapeutic Salmonella enterica serovar Typhimurium after invasion of TRAMP mouse prostate tumor

The intricate dance of tumor evolution: Exploring immune escape, tumor migration, drug resistance, and treatment strategies

Recent research has unveiled fascinating insights into the intricate mechanisms governing tumor evolution. These studies have illuminated how tumors adapt and proliferate by exploiting various factors, including immune evasion, resistance to therapeutic drugs, genetic mutations, and their ability to adapt to different environments. Furthermore, investigations into tumor heterogeneity and chromosomal aberrations have revealed the profound complexity that underlies the evolution of cancer. Emerging findings have also underscored the role of viral influences in the development and progression of cancer, introducing an additional layer of complexity to the field of oncology. Tumor evolution is a dynamic and complex process influenced by various factors, including immune evasion, drug resistance, tumor heterogeneity, and viral influences. Understanding these elements is indispensable for developing more effective treatments and advancing cancer therapies. A holistic approach to studying and addressing tumor evolution is crucial in the ongoing battle against cancer. The main goal of this comprehensive review is to explore the intricate relationship between tumor evolution and critical aspects of cancer biology. By delving into this complex interplay, we aim to provide a profound understanding of how tumors evolve, adapt, and respond to treatment strategies. This review underscores the pivotal importance of comprehending tumor evolution in shaping effective approaches to cancer treatment.

<italic>Salmonella typhimurium</italic> may support cancer treatment: a review

<p indent="0mm">Antitumour treatments are evolving, including bacteria-mediated cancer therapy which is concurrently an ancient and cutting-edge approach. <italic>Salmonella typhimurium</italic> is a widely studied bacterial species that colonizes tumor tissues, showing oncolytic and immune system-regulating properties. It can be used as a delivery vector for genes and drugs, supporting conventional treatments that lack tumor-targeting abilities. This article summarizes recent evidence on the anticancer mechanisms of <italic>S</italic>. <italic>typhimurium</italic> alone and in combination with other anticancer treatments, suggesting that it may be a suitable approach to disease management. </p>.

A novel tumor-targeting strain of Xenorhabdus stockiae exhibits potent biological activities

Xenorhabdus are symbionts of soil entomopathogenic nematodes of the genus Steinernema presenting two distinct forms in their life cycle, and can produce a broad range of bioactive compounds. In this study, a novel Xenorhabdus stockiae strain HN_xs01 was isolated from a soil sample via an entrapment method using Galleria melonella nematodes. The supernatants of strain HN_xs01 exhibited antimicrobial properties against Gram-negative and Gram-positive bacteria, and insecticidal properties against Helicoverpa armigera larvae, and antitumor properties as well. Moreover, three linear rhabdopeptides (1, 2 and 3) were identified from strain HN_xs01 using nuclear magnetic resonance analysis, which exhibited significant cytotoxic activity against the human epithelial carcinoma cell line A431 and the human chronic myelogenous leukemia cell line K562. Some bacteria have been reported to colonize the tumor region, and we determined that HN_xs01 could grow in tumor xenografts in this study. HN_xs01 invaded and replicated in B16 melanoma cells grafted into C57BL/6 mice, resulting in tumor inhibition. Moreover, strain HN_xs01 not only merely aggregated in the tumor environment, but also prevented pulmonary metastasis. It caused fragmentation of vessels and cell apoptosis, which contributed to its antitumor effect. In conclusion, X. stockiae HN_xs01 is a novel tumor-targeting strain with potential applications in medicinal and agricultural fields.

Recombinant Attenuated Salmonella enterica as a Delivery System of Heterologous Molecules in Cancer Therapy

Simple Summary

Cancer is among the main causes of death of millions of individuals worldwide. Although survival has improved with conventional treatments, the appearance of resistant cancer cells leads to patient relapses. It is, therefore, necessary to find new antitumor therapies that can completely eradicate transformed cells. Bacteria-based tumor therapy represents a promising alternative treatment, particularly the use of live-attenuated Salmonella enterica, with its potential use as a delivery system of antitumor heterologous molecules such as tumor-associated antigens, cytotoxic molecules, immunomodulatory molecules, pro-apoptotic proteins, nucleic acids, and nanoparticles. In this review, we present the state of the art of current preclinical and clinical research on the use of Salmonella enterica as a potential therapeutic ally in the war against cancer.

Abstract

Over a century ago, bacterial extracts were found to be useful in cancer therapy, but this treatment modality was obviated for decades. Currently, in spite of the development and advances in chemotherapies and radiotherapy, failure of these conventional treatments still represents a major issue in the complete eradication of tumor cells and has led to renewed approaches with bacteria-based tumor therapy as an alternative treatment. In this context, live-attenuated bacteria, particularly Salmonella enterica, have demonstrated tumor selectivity, intrinsic oncolytic activity, and the ability to induce innate or specific antitumor immune responses. Moreover, Salmonella enterica also has strong potential as a delivery system of tumor-associated antigens, cytotoxic molecules, immunomodulatory molecules, pro-apoptotic proteins, and nucleic acids into eukaryotic cells, in a process known as bactofection and antitumor nanoparticles. In this review, we present the state of the art of current preclinical and clinical research on the use of Salmonella enterica as a potential therapeutic ally in the war against cancer.

Targeting of pancreatic cancer cells and stromal cells using engineered oncolytic Salmonella typhimurium

Pancreatic cancer is resistant to conventional therapeutic interventions, mainly due to abundant cancer stromal cells and poor immune cell infiltration. Here, we used a targeted cancer therapy approach based on attenuated Salmonella typhimurium engineered to express cytolysin A (ClyA) to target cancer stromal cells and cancer cells and treat pancreatic cancer in mice. Nude mice bearing subcutaneous or orthotopic human pancreatic cancers were treated with engineered S. typhimurium expressing ClyA. The tumor microenvironment was monitored to analyze stromal cell numbers, stromal cell marker expression, and immune cell infiltration. The attenuated bacteria accumulated and proliferated specifically in tumor tissues after intravenous injection. The bacteria secreted ClyA into the tumor microenvironment. A single dose of ClyA-expressing Salmonella markedly inhibited growth of pancreatic cancer both in subcutaneous xenograft- and orthotopic tumor-bearing nude mice. Histological analysis revealed a marked decrease in expression of stromal cell markers and increased immune cell (neutrophils and macrophages) infiltration into tumors after colonization by ClyA-expressing bacteria. ClyA-expressing S. typhimurium destroyed cancer stromal cells and cancer cells in mouse models of human pancreatic cancer. This approach provides a novel strategy for combining anticancer and anti-stromal therapy to treat pancreatic cancer.

Integration of Salmonella into Combination Cancer Therapy

Simple Summary

Despite significant advances in the development of new treatments, cancer continues to be a major public health concern due to the high mortality associated with the disease. The introduction of immunotherapy as a new modality for cancer treatment has led to unprecedented clinical responses, even in terminal cancer patients. However, for reasons that remain largely unknown, the percentage of patients who respond to this treatment remains rather modest. In the present article, we highlight the potential of using attenuated Salmonella strains in cancer treatment, particularly as a means to enhance therapeutic efficacy of other cancer treatments, including immunotherapy, chemotherapy, and radiotherapy. The challenges associated with the clinical application of Salmonella in cancer therapy are discussed. An increased understanding of the potential of Salmonella bacteria in combination cancer therapy may usher in a major breakthrough in its clinical application, resulting in more favorable and durable outcomes.

Abstract

Current modalities of cancer treatment have limitations related to poor target selectivity, resistance to treatment, and low response rates in patients. Accumulating evidence over the past few decades has demonstrated the capacity of several strains of bacteria to exert anti-tumor activities. Salmonella is the most extensively studied entity in bacterial-mediated cancer therapy, and has a good potential to induce direct tumor cell killing and manipulate the immune components of the tumor microenvironment in favor of tumor inhibition. In addition, Salmonella possesses some advantages over other approaches of cancer therapy, including high tumor specificity, deep tissue penetration, and engineering plasticity. These aspects underscore the potential of utilizing Salmonella in combination with other cancer therapeutics to improve treatment effectiveness. Herein, we describe the advantages that make Salmonella a good candidate for combination cancer therapy and summarize the findings of representative studies that aimed to investigate the therapeutic outcome of combination therapies involving Salmonella. We also highlight issues associated with their application in clinical use.

Nontyphoidal Salmonella: a potential anticancer agent

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

Cancer Immunotherapy: Priming the Host Immune Response with Live Attenuated Salmonella enterica

In recent years, cancer immunotherapy has undergone great advances because of our understanding of the immune response and the mechanisms through which tumor cells evade it. A century after the first immunotherapy attempt based on bacterial products described by William Coley, the use of live attenuated bacterial vectors has become a promising alternative in the fight against cancer. This review describes the role of live attenuated Salmonella enterica as an oncolytic and immunotherapeutic agent, due to its high affinity for tumor tissue and its ability to activate innate and adaptive antitumor immune response. Furthermore, its potential use as delivery system of tumor antigens and immunomodulatory molecules that induce tumor regression is also reviewed.

Salmonella Bacterial Monotherapy Reduces Autochthonous Prostate Tumor Burden in the TRAMP Mouse Model

Attenuated Salmonella typhimurium injected in the circulatory system of mammals selectively targets tumors. Using weekly intraperitoneal injections of attenuated Salmonella strain CRC2631, we tested for regression and/or inhibition of tumor development in the TRAMP prostate tumor mouse model, which utilizes SV40 early region expression for autochthonous formation of prostate tumors that progress into metastatic, poorly differentiated prostatic carcinomas in an immunocompetent murine model. Thirteen weekly intraperitoneal administrations of 10⁵–10⁷ CFU CRC2631 into 10 week old mice were well tolerated by the TRAMP model. Sacrifice and histological analysis of TRAMP prostates at 22 weeks indicated that Salmonella monotherapy at administrated levels decrease visible tumor size (>29%) but did not significantly inhibit previously described SV40 expression-driven TRAMP tumor progression to undifferentiated carcinomas when histologically examined. In conclusion, this work demonstrates baseline results for CRC2631 Salmonella monotherapy using the immunocompetent TRAMP prostate tumor model in preparation for study of combination therapies that resolve autochthonously generated TRAMP prostate tumors, further reduce tumor size, or inhibit prostate tumor progression.

Antimelanoma effect of Salmonella Typhimurium integration host factor mutant in murine model

AIM

This study aimed to evaluate an attenuated Salmonella ihfA-null mutant strain as therapeutic agent to control tumor growth.

MATERIALS & METHODS

After bacterial toxicity evaluation, C57BL/6JUnib mice were inoculated with B16F10 cells and treated with two Salmonella strains (LGBM 1.1 and LGBM 1.41).

RESULTS

LGBM 1.1 can reduce tumor mass, but it exerts some toxic effects. Although LGBM 1.41 is less toxic than LGBM 1.1, it does not reduce tumor mass significantly. Indeed, animals treated with LGBM 1.41 present only slightly initial delay in tumor progression and increased survival rate as compared with the control.

CONCLUSION

The null-mutants of ihfA gene of Salmonella Typhimurium could be a promising candidate for melanoma treatment.

Strains, Mechanism, and Perspective: Salmonella-Based Cancer Therapy

Recently, investigation of bacterial-based tumor therapy has regained focus due to progress in molecular, cellular, and microbial biology. Many bacteria such as Salmonella, Listeria, Escherichia, and Clostridium have proved to have tumor targeting and in some cases even tumor-destroying phenotypes. Furthermore, bacterial clinical treatments for cancer have been improved by combination with other therapeutic methods such as chemotherapeutic drugs and radioactive agents. Synthetic biology techniques have also driven the development of new bacterial-based cancer therapies. However, basic questions about the mechanisms of bacterial-mediated tumor targeting and destruction are still being elucidated. In this review, we focus on three tumor-therapeutic Salmonella models, the most intensively studied bacterial genus in this field. One of these Salmonella models is our Salmonella enterica serovar Typhimurium LT2 derived strain CRC2631, engineered to minimize toxicity but maximize tumor-targeting and destruction effects. The other two are VNP20009 and A1-R. We compare the means by which these therapeutic candidate strain models were selected for study, their tumor targeting and tumor destruction phenotypes in vitro and in vivo, and what is currently known about the mechanisms by which they target and destroy tumors.

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.

Rescuing chemotaxis of the anticancer agent Salmonella enterica serovar Typhimurium VNP20009

The role of chemotaxis and motility in Salmonella enterica serovar Typhimurium tumor colonization remains unclear. We determined through swim plate assays that the well-established anticancer agent S. Typhimurium VNP20009 is deficient in chemotaxis, and that this phenotype is suppressible. Through genome sequencing, we revealed that VNP20009 and four selected suppressor mutants had a single nucleotide polymorphism (SNP) in cheY causing a mutation in the conserved proline residue at position 110. CheY is the response regulator that interacts with the flagellar motor-switch complex and modulates rotational bias. The four suppressor mutants additionally carried non-synonymous SNPs in fliM encoding a flagellar switch protein. The CheY-P110S mutation in VNP20009 likely rendered the protein unable to interact with FliM, a phenotype that could be suppressed by mutations in FliM. We replaced the mutated cheY in VNP20009 with the wild-type copy and chemotaxis was partially restored. The swim ring of the rescued strain, VNP20009 cheY(+), was 46% the size of the parental strain 14028 swim ring. When tested in capillary assays, VNP20009 cheY(+) was 69% efficient in chemotaxis towards the attractant aspartate as compared to 14028. Potential reasons for the lack of complete restoration and implications for bacterial tumor colonization will be discussed.

[Salmonella enterica: an ally in the therapy of cancer]

Salmonella enterica, a species of facultative anaerobic bacteria, has demonstrated success as a live-attenuated bacterial vector for vaccination. S. enterica has also demonstrated promise as a therapeutic agent against cancer. Pre-clinical and clinical trials have shown that S. enterica is localized in both solid and semi-solid tumors as well as in metastatic tumors. Moreover, S. enterica reduces resistance to treatment with other agents. In this review we present the novel therapeutic anti-cancer approaches that use S. enterica both for its ability as a delivery system for heterologous moieties against cancer and for its direct anti-cancer properties.

Efficiency of conditionally attenuated Salmonella enterica serovar Typhimurium in bacterium-mediated tumor therapy

Increasing numbers of cancer cases generate a great urge for new treatment options. Applying bacteria like Salmonella enterica serovar Typhimurium for cancer therapy represents an intensively explored option. These bacteria have been shown not only to colonize solid tumors but also to exhibit an intrinsic antitumor effect. In addition, they could serve as tumor-targeting vectors for therapeutic molecules. However, the pathogenic S. Typhimurium strains used for tumor therapy need to be attenuated for safe application. Here, lipopolysaccharide (LPS) deletion mutants (ΔrfaL, ΔrfaG, ΔrfaH, ΔrfaD, ΔrfaP, and ΔmsbB mutants) of Salmonella were investigated for efficiency in tumor therapy. Of such variants, the ΔrfaD and ΔrfaG deep rough mutants exhibited the best tumor specificity and lowest pathogenicity. However, the intrinsic antitumor effect was found to be weak. To overcome this limitation, conditional attenuation was tested by complementing the mutants with an inducible arabinose promoter. The chromosomal integration of the respective LPS biosynthesis genes into the araBAD locus exhibited the best balance of attenuation and therapeutic benefit. Thus, the present study establishes a basis for the development of an applicably cancer therapeutic bacterium.

IMPORTANCE

Cancer has become the second most frequent cause of death in industrialized countries. This and the drawbacks of routine therapies generate an urgent need for novel treatment options. Applying appropriately modified S. Typhimurium for therapy represents the major challenge of bacterium-mediated tumor therapy. In the present study, we demonstrated that Salmonella bacteria conditionally modified in their LPS phenotype exhibit a safe tumor-targeting phenotype. Moreover, they could represent a suitable vehicle to shuttle therapeutic compounds directly into cancerous tissue without harming the host.