Inhibition of Lewis lung carcinoma growth by Toxoplasma gondii through induction of Th1 immune responses and inhibition of angiogenesis

Toxoplasma gondii-Derived Exosomes: A Potential Immunostimulant and Delivery System for Tumor Immunotherapy Superior to Toxoplasma gondii

Immunotherapies such as immune checkpoint blockade (ICB) therapy and chimeric antigen receptor T-cell (CAR-T) therapy have ushered in a new era of tumor treatment. However, most patients do not benefit from immunotherapy due to limitations such as narrow indications, low response rates, and high rates of adverse effects. Toxoplasma gondii (T. gondii), a specialized intracellular protozoan, can modulate host immune responses by inhibiting or stimulating cytokines. The ability of T. gondii to enhance an organism's immune response was found to have a direct anti-tumor effect and enhance the sensitivity of patients with tumors to ICB therapy. However, the application of T. gondii for tumor therapy faces several challenges, such as biosafety concerns. Exosomes, a subtype of extracellular vesicle that contains active components such as proteins, nucleic acids, and lipids, have become effective therapeutic tools for various diseases, including tumors. Parasites, such as T. gondii, mediate the communication of pathogens with immune cells and modulate host cellular immune responses through exosomes. Growing evidence indicates that T. gondii-derived exosomes mediate communication between pathogens and immune cells, modulate host immune responses, and have great potential as new tools for tumor therapy. In this review, we highlight recent advances in isolation and identification techniques, profiling analysis, host immunomodulatory mechanisms, and the role of T. gondii-derived exosomes in tumor immunotherapy. Additionally, we emphasize the potential of T. gondii-derived exosomes as delivery platform to enhance anti-tumor efficacy in combination with other therapies. This review proposes that T. gondii-derived exosomes may serve as a novel tool for tumor immunotherapy owing to their ability to activate host immune function and properties such as high modifiability, stability, and low toxicity. This work will assist in promoting the application of parasite exosomes in tumor therapy.

Parasites revive hope for cancer therapy

Parasites have attained a life-long stigma of being detrimental organisms with deleterious outcomes. Yet, recently, a creditable twist was verified that can dramatically change our perception of those parasites from being a source of misery to millions of people to a useful anti-cancerous tool. Various parasites have shown promise to combat cancer in different experimental models, including colorectal, lung, and breast cancers, among others. Helminths and protozoan parasites, as well as their derivatives such as Echinococcus granulosus protein KI-1, Toxoplasma gondii GRA15II, and Trypanosoma cruzi calreticulin, have demonstrated the ability to inhibit tumor growth, angiogenesis, and metastasis. This article provides an overview of the literature on various cancer types that have shown promising responses to parasite therapy in both in vitro and in vivo animal studies. Parasites have shown anti-neoplastic activity through a variety of mechanisms that collectively contribute to their anti-cancer properties. These include immunomodulation, inhibition of angiogenesis, and molecular mimicry with cancer cells. This review article sheds light on this intriguing emerging field and emphasizes the value of collaborative multidisciplinary research projects with funding agencies and pharmaceutical companies. Thus, these strategies would secure continuous exploration of this new avenue and accelerate the advancement of cancer therapy research. Although experimental studies are heavily conducted by leaps and bounds, further steps are definitely lagging. Upgrading research from the experimental level to the clinical trial would be a wise progression toward efficient exploitation of the anti-neoplastic capabilities of parasites, ultimately saving countless lives.

Parasite-enhanced immunotherapy: transforming the "cold" tumors to "hot" battlefields

Immunotherapy has emerged as a highly effective treatment for various tumors. However, the variable response rates associated with current immunotherapies often restrict their beneficial impact on a subset of patients. Therefore, more effective treatment approaches that can broaden the scope of therapeutic benefits to a larger patient population are urgently needed. Studies have shown that some parasites and their products, for example, Plasmodium, Toxoplasma, Trypanosoma, and Echinococcus, can effectively transform "cold" tumors into "hot" battlefields and reshape the tumor microenvironment, thereby stimulating innate and adaptive antitumor immune responses. These parasitic infections not only achieve the functional reversal of innate immune cells, such as neutrophils, macrophages, myeloid-derived suppressor cells, regulatory T cells, and dendritic cells, in tumors but also successfully activate CD4+/CD8+ T cells and even B cells to produce antibodies, ultimately resulting in an antitumor-specific immune response and antibody-dependent cellular cytotoxicity. Animal studies have confirmed these findings. This review discusses the abovementioned content and the challenges faced in the future clinical application of antitumor treatment strategies based on parasitic infections. With the potential of these parasites and their byproducts to function as anticancer agents, we anticipate that further investigations in this field could yield significant advancements in cancer treatment.

Mining parasites for their potential as novel therapeutic agents against cancer

Despite recent advances in the management and therapeutic of cancer, the treatment of the disease is limited by its high cost and severe side effects. In this scenario, there is an unmet need to identify novel treatment alternatives for this dreaded disease. Recently there is growing evidence that parasites may cause anticancer effects because of a negative correlation between parasitic infections and tumour growth despite some parasites that are known to exhibit pro-carcinogenic effects. It has been observed that parasites exert an anticancer effect either by activating the host's immune response or by secreting certain molecules that exhibit anticancer potential. The activation of the immune response by these parasitic organisms results in the inhibition of some of the hallmarks of cancer such as tumour proliferation, angiogenesis, and metastasis. This review summarizes the current advances as well as the mechanisms underlying the possible implications of this diverse group of organisms as anticancer agents.

The opposing effect of acute and chronic Toxoplasma gondii infection on tumor development

BACKGROUND

The interplay between Toxoplasma gondii infection and tumor development is intriguing and not yet fully understood. Some studies showed that T. gondii reversed tumor immune suppression, while some reported the opposite, stating that T. gondii infection promoted tumor growth.

METHODS

We created three mouse models to investigate the interplay between T. gondii and tumor. Model I aimed to study the effect of tumor growth on T. gondii infection by measuring cyst number and size. Models II and III were used to investigate the effect of different stages of T. gondii infection on tumor development via flow cytometry and bioluminescent imaging. Mouse strains (Kunming, BALB/c, and C57BL/6J) with varying susceptibilities to tumors were used in the study.

RESULTS

The size and number of brain cysts in the tumor-infected group were significantly higher, indicating that tumor presence promotes T. gondii growth in the brain. Acute T. gondii infection, before or after tumor cell introduction, decreased tumor growth manifested by reduced bioluminescent signal and tumor size and weight. In the tumor microenvironment, CD4+ and CD8+ T cell number, including their subpopulations (cytotoxic CD8+ T cells and Th1 cells) had a time-dependent increase in the group with acute T. gondii infection compared with the group without infection. However, in the peripheral blood, the increase of T cells, including cytotoxic CD8+ T cells and Th1 cells, persisted 25 days after Lewis lung carcinoma (LLC) cell injection in the group with acute T. gondii. Chronic T. gondii infection enhanced tumor growth as reflected by increase in tumor size and weight. The LLC group with chronic T. gondii infection exhibited decreased percentages of cytotoxic CD8+ T cells and Th1 cells 25 days post-LLC injection as compared with the LLC group without T. gondii infection. At week 4 post-LLC injection, chronic T. gondii infection increased tumor formation rate [odds ratio (OR) 1.71] in both KM and BALB/c mice.

CONCLUSIONS

Our research elucidates the dynamics between T. gondii infection and tumorigenesis. Tumor-induced immune suppression promoted T. gondii replication in the brain. Acute and chronic T. gondii infection had opposing effects on tumor development.

A potential cure for tumor-associated immunosuppression by Toxoplasma gondii

BACKGROUND

Recently, immunotherapy has become very hopeful for cancer therapy. Cancer treatment through immunotherapy has excellent specificity and less toxicity than conventional chemoradiotherapy. Pathogens have been used in cancer immunotherapy for a long time. The current study aims to evaluate the possibility of Toxoplasma gondii (T. gondii) as a probable treatment for cancers such as melanoma, breast, ovarian, lung, and pancreatic cancer.

RECENT FINDINGS

Nonreplicating type I uracil auxotrophic mutants of T. gondii can stimulate immune responses against tumors by reverse immunosuppression at the cellular level. T. gondii can be utilized to research T helper 1 (Th1) cell immunity in intracellular infections. Avirulent T. gondii uracil auxotroph vaccine can change the tumor's immunosuppression and improve the production of type 1 helper cell cytokines, i.e., Interferon-gamma (IFN-γ) and Interleukin-12 (IL-12) and activate tumor-related Cluster of Differentiation 8 (CD8+) T cells to identify and destroy cancer cells. The T. gondii profilin protein, along with T. gondii secreted proteins, have been found to exhibit promising properties in the treatment of various cancers. These proteins are being studied for their potential to inhibit tumor growth and enhance the effectiveness of cancer therapies. Their unique mechanisms of action make them valuable candidates for targeted interventions in ovarian cancer, breast cancer, pancreatic cancer, melanoma, and lung cancer treatments.

CONCLUSION

In summary, the study underscores the significant potential of harnessing T. gondii, including its diverse array of proteins and antigens, particularly in its avirulent form, as a groundbreaking approach in cancer immunotherapy.

A novel enemy of cancer: recent investigations into protozoan anti-tumor properties

Cancer remains a significant global health issue, despite advances in screening and treatment. While existing tumor treatment protocols such as surgery, chemotherapy, radiotherapy, targeted therapy, and immunotherapy have proven effective in enhancing the prognosis for some patients, these treatments do not benefit all patients. Consequently, certain types of cancer continue to exhibit a relatively low 5-year survival rate. Therefore, the pursuit of novel tumor intervention strategies may help improve the current effectiveness of tumor treatment. Over the past few decades, numerous species of protozoa and their components have exhibited anti-tumor potential via immune and non-immune mechanisms. This discovery introduces a new research direction for the development of new and effective cancer treatments. Through in vitro experiments and studies involving tumor-bearing mice, the anti-tumor ability of Toxoplasma gondii, Plasmodium, Trypanosoma cruzi, and other protozoa have unveiled diverse mechanisms by which protozoa combat cancer, demonstrating encouraging prospects for their application. In this review, we summarize the anti-tumor ability and anti-tumor mechanisms of various protozoa and explore the potential for their clinical development and application.

Parasites as potential targets for cancer immunotherapy

Parasites and cancers have some common antigens. Much scientific evidence in the human population, animal models, and in vitro experiments exhibit that parasites have significant anti-cancer effects. The larval stage of the tapeworm Echinococcus granulosus, Toxoplasma gondii, Trypanosoma cruzy, Plasmodium's, and Trichinella spiralis are among the parasites that have been subjects of anti-cancer research in the last decades. Anti-tumor effects of parasites may be due to the direct impact of the parasites per se or indirectly due to the immune response raised against common antigens between malignant cells and parasites. This manuscript reviews the anti-cancer effects of parasites and possible mechanisms of these effects. Options for using parasites or their antigens for cancer treatment in the future have been discussed.

Toxoplasma gondii gra5 deletion mutant protects hosts against Toxoplasma gondii infection and breast tumors

Toxoplasma gondii is the causative agent of toxoplasmosis, a zoonotic disease that poses a threat to human health and a considerable loss to livestock farming. At present, clinical therapeutic drugs mainly target T. gondii tachyzoites and fail to eradicate bradyzoites. Developing a safe and effective vaccine against toxoplasmosis is urgent and important. Breast cancer has become a major public health problem and the therapeutic method needs to be further explored. Many similarities exist between the immune responses caused by T. gondii infection and the immunotherapy for cancers. T. gondii dense granule organelles secrete immunogenic dense granule proteins (GRAs). GRA5 is localized to the parasitophorous vacuole membrane in the tachyzoite stage and the cyst wall in the bradyzoite stage. We found that T. gondii ME49 gra5 knockout strain (ME49Δgra5) was avirulent and failed to form cysts but stimulated antibodies, inflammatory cytokines, and leukocytes infiltration in mice. We next investigated the protective efficacy of ME49Δgra5 vaccination against T. gondii infection and tumor development. All the immunized mice survived the challenge infection of either wild-type RH, ME49, VEG tachyzoites, or ME49 cysts. Moreover, ME49Δgra5 tachyzoite inoculation in situ attenuated the growth of murine breast tumor (4T1) in mice and prevented 4T1's lung metastasis. ME49Δgra5 inoculation upregulated the levels of Th1 cytokines and tumor-infiltrating T cells in the tumor microenvironment and triggered anti-tumor responses by increasing the number of natural killer, B, and T cells, macrophages, and dendritic cells in the spleen. Collectively, these results suggested that ME49Δgra5 was a potent live attenuated vaccine against T. gondii infection and breast cancer.

Shedding light on a mysterious link between Toxoplasma Gondii and cancer: A review

The ongoing conflict regarding the affiliation of Toxoplasma gondii to cancer; whether an inducer or a suppressor needs to be resolved. Human epidemiological studies oscillate without attaining a firm ground. Some studies confirmed the detection of high seroprevalence of anti-Toxoplasma antibodies in different cancer patients without further justification whether being causation, co-incidences, or part of opportunistic infections. Others reported a state of resistance to cancer accompanying low titer of anti-Toxoplasma antibody. Worthwhile, preclinical experimental work confirmed the antineoplastic potency of Toxoplasma. Thus, further investigational research is essential to validate the potential application of Toxoplasma as a promising cancer immunotherapeutic vaccine candidate. In this paper, we present a review of this issue by examining epidemiological and preclinical experimental studies that explored the linkage between Toxoplasma gondii and cancer<i.></i> We consider this review an important step towards shedding a light on this mysterious link and a stepping-stone for potential research work addressing Toxoplasma as a cancer suppressor rather than a cancer inducer.

Prophylactic antineoplastic activity of Toxoplasma gondii RH derived antigen against ehrlich solid carcinoma with evidence of shared antigens by comparative immunoblotting

BACKGROUND

With cancer cases escalation, an urgent request to develop novel combating strategies arise. Pathogen-based cancer-immunotherapy is getting more consideration. Autoclaved parasitic antigens seem promising candidates, taking steadily their first steps. Our aim was to examine the prophylactic antineoplastic activity of autoclaved Toxoplasma vaccine (ATV) and to test for the shared antigen theory between Toxoplasma gondii and cancer cells.

METHODS

Mice were immunized with ATV followed by Ehrlich solid carcinoma (ESC) inoculation. Tumor weight, volume, histopathology, and immunohistochemistry for CD8⁺ T cells, Treg cells and VEGF were assessed. In addition, the proposed shared antigen theory between parasites and cancer was also verified using SDS-PAGE and immunoblotting.

RESULTS

Results revealed powerful prophylactic activity of ATV with 13.3% inhibition of ESC incidence, significant reduction in tumor weight and volume in ATV vaccinated mice. Immunologically, significantly higher CD8⁺T cells and lower FOXP3⁺ Treg cells surrounded and infiltrated ESC in ATV immunized mice with higher CD8⁺T/Treg cells ratio and significant antiangiogenic effect. Moreover, SDS-PAGE and immunoblotting showed four shared bands between Ehrlich carcinoma and ATV of approximate molecular weights 60, 26, 22 and 12.5 KDa.

CONCLUSION

Exclusively, we demonstrated a prophylactic antineoplastic activity of autoclaved Toxoplasma vaccine against ESC. Moreover, to the best of our knowledge this is the first report highlighting the existence of cross-reactive antigens between Toxoplasma gondi parasite and cancer cells of Ehrlich carcinoma.

Toxoplasma gondii-derived antigen modifies tumor microenvironment of Ehrlich solid carcinoma murine model and enhances immunotherapeutic activity of cyclophosphamide

Pathogen-based cancer vaccine is a promising immunotherapeutic weapon to stimulate cancer immunosuppressive state. Toxoplasma gondii is a potent immunostimulant, and low-dose infection was linked to cancer resistance. Our goal was to evaluate the therapeutic antineoplastic activity of autoclaved Toxoplasma vaccine (ATV) against Ehrlich solid carcinoma (ESC) in mice in reference to and in combination with low-dose cyclophosphamide (CP), a cancer immunomodulator. Mice inoculation with ESC was followed by applying different treatment modalities including ATV, CP, and CP/ATV. We evaluated the impact of the different treatments on liver enzymes and pathology, tumor weight, volume, and histopathological changes. Using immunohistochemistry, we evaluated CD8⁺ T cell, FOXP3⁺ Treg, CD8⁺/Treg outside and inside ESC, and angiogenesis. Results showed significant tumor weights and volumes reduction with all treatments with 13.3% inhibition of tumor development upon combined CP/ATV use. Significant necrosis and fibrosis were noted in ESC by all treatments with improved hepatic functions versus non-treated control. Although ATV was almost equivalent to CP in tumor gross and histopathology, it promoted an immunostimulatory activity with significant Treg cells depletion outside ESC and CD8⁺ T cells infiltration inside ESC with higher CD8⁺ T/Treg ratio inside ESC superior to CP. Combined with CP, ATV exhibited significant synergistic immunotherapeutic and antiangiogenic action compared to either treatment alone with significant Kupffer cells hyperplasia and hypertrophy. Exclusively, therapeutic antineoplastic and antiangiogenic activity of ATV against ESC was verified that boosted CP immunomodulatory action which highlights a novel biological cancer immunotherapeutic vaccine candidate.

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.

Beneficial Effect of Toxoplasma gondii Infection on the Prognosis of Breast Cancer Was Modified by Cytokines

Background

Animal experiments have shown the anticancer activity of Toxoplasma gondii (T. gondii), but its effect on the prognosis of cancer patients is unclear. Thus, the present study aimed to investigate the prognostic role of anti-T. gondii IgG in breast cancer patients and the modification effect of cytokines.

Methods

A total of 1121 breast cancer patients were recruited between 2008 and 2018 and followed up until December 31, 2021. Anti-T. gondii IgG and cytokines were measured using an enzyme-linked immunosorbent assay (ELISA) kit and a multiplex assay platform. Endpoints were overall survival (OS) and progression-free survival (PFS). Survival and multiplicative interaction analyses were performed using multivariate Cox regression models.

Results

According to the cutoff value of optical density (OD=0.111), 900 (80.29%) and 221 (19.71%) patients were divided into two groups: low or high anti-T. gondii IgG. Compared to patients with a low anti-T. gondii IgG level, the adjusted hazard ratios (HRs) of OS and PFS for patients with high anti-T. gondii IgG levels were 0.60 (95% confidence interval (CI): 0.37-0.99) and 0.67 (0.46-0.98), respectively. These associations were profound among patients with a high cytokine score (HR=0.29, 95% CI: 0.10-0.82 for OS; HR=0.30, 95% CI: 0.13-0.69 for PFS), accompanied by a significant interaction between the level of anti-T. gondii IgG and the cytokine score (P _interaction=0.019 for PFS); interleukin-17 (IL-17) and interleukin-9 (IL-9) were the main contributors to the interaction.

Conclusion

Anti-T. gondii IgG was found to be beneficial to breast cancer survival, especially in women with systematic inflammation and high IL-17 or IL-9 levels, suggesting the potential of T. gondii as a prognostic marker and a novel immunotherapy approach for cancer patients.

Neospora caninum inhibits tumor development by activating the immune response and destroying tumor cells in a B16F10 melanoma model

Background

Melanoma is a malignant tumor with a high mortality rate. Some microorganisms have been shown to activate the immune system and limit cancer progression. The objective of this study is to evaluate the anti-melanoma effect of Neospora caninum, a livestock pathogen with no pathogenic activity in humans.

Methods

Neospora caninum tachyzoites were inoculated into a C57BL/6 mouse melanoma model by intratumoral and distal subcutaneous injections. Tumor volumes were measured, and cell death areas were visualized by hematoxylin and eosin staining and quantified. Apoptosis in cell cultures and whole tumors was detected by propidium iodide (PI) and TUNEL staining, respectively. Cytokine and tumor-associated factor levels in tumors and spleens were detected by real-time quantitative polymerase chain reaction. Infiltration of macrophages and CD8⁺ T cells in the tumor microenvironment (TME) were detected by immunohistochemistry with anti-CD68 and anti-CD8 antibodies, respectively. Finally, 16S rRNA sequencing of mice cecal contents was performed to evaluate the effect of N. caninum on gut microbial diversity.

Results

Intratumoral and distal subcutaneous injections of N. caninum resulted in significant inhibition of tumor growth (P < 0.001), and more than 50% of tumor cells were dead without signs of apoptosis. Neospora caninum treatment significantly increased the mRNA expression levels of IL-12, IFN-γ, IL-2, IL-10, TNF-α, and PD-L1 in the TME, and IL-12 and IFN-γ in the spleen of tumor-bearing mice (P < 0.05). An increase in the infiltration of CD8⁺ T cells and macrophages in the TME was observed with these cytokine changes. Neospora caninum also restored the abundance of gut microbiota Lactobacillus, Lachnospiraceae, Adlercreutzia, and Prevotellaceae associated with tumor growth, but the changes were not significant.

Conclusion

Neospora caninum inhibits B16F10 melanoma by activating potent immune responses and directly destroying the cancer cells. The stable, non-toxic, and efficacious properties of N. caninum demonstrate the potential for its use as a cancer treatment.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-022-05456-8.

Toxoplasma gondii infection possibly reverses host immunosuppression to restrain tumor growth

Tumor cells can successfully escape the host immune attack by inducing the production of immunosuppressive cells and molecules, leading to an ineffective tumor treatment and poor prognosis. Although immunotherapies have improved the survival rate of cancer patients in recent years, more effective drugs and therapies still need to be developed. As an intracellular parasite, Toxoplasma gondii can trigger a strong Th1 immune response in host cells, including upregulating the expression of interleukin-12 (IL-12) and interferon-γ (IFN-γ). Non-replicating uracil auxotrophic strains of T. gondii were used to safely reverse the immunosuppression manipulated by the tumor microenvironment. In addition to the whole lysate antigens, T. gondii-secreted effectors, including Toxoplasma profilin, rhoptry proteins (ROPs), and dense granule antigens (GRAs), are involved in arousing the host’s antigen presentation system to suppress tumors. When T. gondii infection relieves immunosuppression, tumor-related myeloid cells, including macrophages and dendritic cells (DCs), are transformed into immunostimulatory phenotypes, showing a powerful Th1 immune response mediated by CD8⁺ T cells. Afterwards, they target and kill the tumor cells, and ultimately reduce the size and weight of tumor tissues. This article reviews the latest applications of T. gondii in tumor therapy, including the activation of cellular immunity and the related signal pathways, which will help us understand why T. gondii infection can restrain tumor growth.

Anti-Tumor Effect of Parasitic Protozoans

The immune system may aberrantly silence when against “altered self”, which consequently may develop into malignancies. With the development of tumor immunology and molecular biology, the deepened understanding of the relationship between parasites and tumors shifts the attitude towards parasitic pathogens from elimination to utilization. In recent years, the antitumor impact implemented by protozoan parasites and the derived products has been confirmed. The immune system is activated and enhanced by some protozoan parasites, thereby inhibiting tumor growth, angiogenesis, and metastasis in many animal models. In this work, we reviewed the available information on the antitumor effect of parasitic infection or induced by parasitic antigen, as well as the involved immune mechanisms that modulate cancer progression. Despite the fact that clinical trials of the protozoan parasites against tumors are limited and the specific mechanisms of the effect on tumors are not totally clear, the use of genetically modified protozoan parasites and derived molecules combined with chemotherapy could be an important element for promoting antitumor treatment in the future.

Promising effects of parasite-derived compounds on tumor regression: a systematic review of in vitro and in vivo studies

The parasites are repeatedly confronting their host to take advantage of nutrients for multiplication and survival. In this sense, a wide spectrum of molecules is released from both sides, with immune-regulatory activity, accompanying this biological battle. Such parasites and their valuable molecules can be directed toward microbial-based cancer therapy. Herein, we contrived a systematic review to gather information on the antitumor activity of parasite-derived compounds. Following systematic search in Web of Science, ScienceDirect, Scopus, PubMed, ProQuest and Embase until 31 December 2019, a total number of 51 articles (54 datasets) were finally included in this review. Thirteen parasitic agents were found to possess possible antitumor activity, comprising protozoan species Toxoplasma gondii, Trypanosoma cruzi, Trichomonas vaginalis, Acanthamoeba castellanii, Besnoitia jellisoni, Leishmania major, Plasmodium yoelii, and Plasmodium lophurae, as well as parasitic helminths Toxocara canis, Echinococcus granulosus, Taenia crassiceps, Trichinella spiralis, and Schistosoma mansoni. Most experiments were done based on antigenic preparations from T. gondii (16 studies), E. granulosus (10 studies), T. spiralis (8 studies), and T. cruzi (6 studies). Possible antitumor properties of the selected parasites were revealed in this review. However, precise molecular basis of anticancer activity for each parasite remains to be elucidated in the future.

Anti-Tumoral Effect and Action Mechanism of Exosomes Derived From Toxoplasma gondii-Infected Dendritic Cells in Mice Colorectal Cancer

Toxoplasma gondii is an obligate intracellular protozoan with anti-tumor activity against a variety of cancers. However, the therapeutic effect of T. gondii on colorectal cancer is unclear, and using direct Toxoplasma infection in immunotherapy involves safety concerns. This study investigated the anti-tumoral effect and mechanism of exosomes derived from dendritic cells (DCs) infected with T. gondii (Me49-DC-Exo). We used differential ultracentrifugation to isolate exosomes from uninfected DCs (DC-Exo) and T. gondii Me49-infected DCs (Me49-DC-Exo). The isolated exosomes were identified by transmission electron microscopy, nanoparticle tracking analysis, and western blotting. Me49-DC-Exo significantly inhibited the tumor growth and reduced the proportion of M2 macrophages in the blood of tumor-bearing mice. In vitro, Me49-DC-Exo suppressed macrophage (RAW264.7) polarization to M2 phenotype. miRNA sequencing revealed that multiple miRNAs in Me49-DC-Exo were differentially expressed compared with DC-Exo, among which miR-182-5p, miR-155-5p, miR-125b-2-3p, and miR-155-3p were up-regulated, while miR-9-5p was significantly down-regulated. Transfecting mimics or inhibitors of these differential miRNAs into RAW264.7 cells showed that miR-155-5p promoted M1 macrophage polarization while inhibiting M2 macrophage polarization. Bioinformatics prediction and dual-luciferase reporter assay confirmed the suppressor of cytokine signaling 1 (SOCS1) as a direct target of miR-155-5p. Silencing SOCS1 gene expression in RAW264.7 cells increased CD86 + CD206 − M1 macrophage proportion, and inducible nitric oxide synthase and tumor necrosis factor-α mRNA levels. However, arginase-1 and transglutaminase 2 expression levels decreased. These results suggest that the exosomes inhibit macrophage polarization to M2 phenotype and regulate SOCS1 expression by delivering functional miR-155-5p. These findings provide new ideas for colorectal cancer immunotherapy.

Evaluation of cytotoxic activity of live toxoplasma gondii tachyzoites and toxoplasma antigen on MCF-7 human breast cancer cell line

The aim of this study was to investigate the cytotoxic potency of live Toxoplasma gondii tachyzoites as well as Toxoplasma antigen on MCF-7 human breast cancer cell line. Cancer cell lines are considered an essential preliminary step towards in-vitro investigation of the potential antineoplastic impact of novel chemotherapeutic agents. Pathogens, including viruses, bacteria, and parasites are noticeably under investigation, considering their potential antineoplastic activity. Some have attained a steady position in the clinical field as hepatitis B virus, human papilloma virus and BCG immunization. Toxoplasma gondii is an apicomplexan parasite with promising antineoplastic activity. In this study, live Toxoplasma tachyzoites provoked a direct cytotoxic effect on MCF-7 in a dose dependent manner, while Toxoplasma antigen didn’t induce such impact. Skipping the direct cytotoxic effect of Toxoplasma antigen doesn’t totally divert the possible antineoplastic activity of Toxoplasma antigen. Potential alternative immune mediated mechanisms could be an alternative. Further in-vivo studies in different cancer models are mandatory to investigate the underlying mechanisms of antineoplastic activity of Toxoplasma gondii

Bugs as drugs: neglected but a promising future therapeutic strategy in cancer

Effective cancer treatment is an urgent need due to the rising incidence of cancer. One of the most promising future strategies in cancer treatment is using microorganisms as cancer indicators, prophylactic agents, immune activators, vaccines or vectors in antitumor therapy. The success of bacteria-mediated chemotherapy will be dependent on the balance of therapeutic benefit and the control of bacterial infection in the body. Additionally, protozoans and viruses have the potential to be used in cancer therapy. This review summarizes how these microorganisms interact with tumor microenvironments and the challenges of a 'bugs as drugs' approach in cancer therapy. Several standpoints are discussed, such as bacteria as vectors for gene therapy that shuttle therapeutic compounds into tumor tissues, their intrinsic antitumor activities and their combination with chemotherapy or radiotherapy. Bug-based cancer therapy is a two-edged sword and we need to find the opportunities by overcoming the challenges.

Anti-Tumor Effect of Marshallagia marshalli Somatic Antigen on Inhibition Cell Growth of K562

BACKGROUND

Today, the inhibitory effect of helminths on tumor cell growth has been proven. We investigated the anti-tumor activity of Marshallagia marshalli somatic against K562 cells.

METHODS

Different concentrations of M. marshalli somatic antigen were incorporated in the culture medium of K652 cells, and the proliferation and apoptosis were measured after 24, 48, and 72 h, using MTT and Annexin V/PI staining assay.

RESULTS

Treatment of cells with 1-2 mg/ml antigen for 24-72 h could suppress cell proliferation and increase apoptosis. While treating cells with 0.1 mg/ml antigen for 72 h could inhibit cell growth. There was no meaningful effect on treated cells in comparison with the control group (P< 0.05) after incubating cells for 24- 48 h with 0.1 mg/ml antigen.

CONCLUSION

M. marshalli somatic antigen had an anti-cancer property, and its role in cancer treatment could be considered as an effective therapeutic method.

A uracil auxotroph Toxoplasma gondii exerting immunomodulation to inhibit breast cancer growth and metastasis

BACKGROUND

Breast cancer is the most common cause of cancer-related death among women, and prognosis is especially poor for patients with triple-negative breast cancer (TNBC); therefore, there is an urgent need for new effective therapies. Recent studies have demonstrated that the uracil auxotroph Toxoplasma gondii vaccine displays anti-tumor effects. Here, we examined the immunotherapy effects of an attenuated uracil auxotroph strain of T. gondii against 4T1 murine breast cancer.

METHODS

We constructed a uracil auxotroph T. gondii RH strain via orotidine 5'-monophosphate decarboxylase gene deletion (RH-Δompdc) with CRISPR/Cas9 technology. The strain's virulence in the T. gondii-infected mice was determined in vitro and in vivo by parasite replication assay, plaque assay, parasite burden detection in mice peritoneal fluids and survival analysis. The immunomodulation ability of the strain was evaluated by cytokine detection. Its anti-tumor effect was evaluated after its in situ inoculation into 4T1 tumors in a mouse model; the tumor volume was measured, and the 4T1 lung metastasis was detected by hematoxylin and eosin and Ki67 antibody staining, and the cytokine levels were measured by an enzyme-linked immunosorbent assay.

RESULTS

The RH-Δompdc strain proliferated normally when supplemented with uracil, but it was unable to propagate without the addition of uracil and in vivo, which suggested that it was avirulent to the hosts. This mutant showed vaccine characteristics that could induce intense immune responses both in vitro and in vivo by significantly boosting the expression of inflammatory cytokines. Inoculation of RH-Δompdc in situ into the 4T1 tumor inhibited tumor growth, reduced lung metastasis, promoted the survival of the tumor-bearing mice and increased the secretion of Th1 cytokines, including interleukin-12 (IL-12) and interferon-γ (INF-δ), in both the serum and tumor microenvironment (TME).

CONCLUSION

Inoculation of the uracil auxotroph RH-Δompdc directly into the 4T1 tumor stimulated anti-infection and anti-tumor immunity in mice, and resulted in inhibition of tumor growth and metastasis, promotion of the survival of the tumor-bearing mice and increased secretion of IL-12 and IFN-γ in both the serum and TME. Our findings suggest that the immunomodulation caused by RH-Δompdc could be a potential anti-tumor strategy.

Links between Infections, Lung Cancer, and the Immune System

Lung cancer is the leading disease of cancer-related deaths worldwide. Since the beginning of the 20th century, various infectious agents associated with lung cancer have been identified. The mechanisms that include systemic inflammatory pathways as effect of microbial persistence in the lung can secondarily promote the development of lung carcinogenesis. Chronic inflammation associated with lung-cancer infections is known to precede tumor development, and it has a strong effect on the response(s) to therapy. In fact, both viral and bacterial infections can activate inflammatory cells and inflammatory signaling pathways. In this review, an overview of critical findings of recent studies investigating associations between each of viral and bacterial pathogens and lung carcinoma is provided, with particular emphasis on how infectious organisms can interfere with oncogenic processes and all the way through immunity. Moreover, a discussion of the direct crosstalk between lung tumor development and inflammatory processes is also presented.

Anti-cancer immunoprotective effects of immunization with hydatid cyst wall antigens in a non-immunogenic and metastatic triple-negative murine mammary carcinoma model

Cancer vaccines have gained lots of attention as the future of cancer treatment. However, poor immunogenicity of tumor-associated antigens often fails to induce an efficient immune response against the tumor. Strange anti-tumor immune responses at the parasite-infected patients due to cross-reactivity have been reported in various studies. Therefore, parasite antigens with significant immunogenicity and high epitope homology with cancer antigens may activate a strong immune response against cancer cells. Herein, the sera of immunized rabbits with the hydatid cyst wall (HCW) antigens were incubated with 4 T1 mammary carcinoma cells to investigate cross-reactivity between the HCW antigens antisera and surface antigens of the breast cancer cells. Also, the SDS-PAGE profile of HCW antigens was prepared and incubated with the breast cancer patients' sera and considerable reactivity was observed between their sera and a specific band (~27/28 kDa) according to Western blotting analyzes. Then, the protein bands with cross-reactivity with breast cancer patients' sera were utilized for prophylactic immunizations of Balb/c mice. The immunoprotective effect of immunization with the HCW antigens caused significant inhibition of 4 T1 breast tumor growth, decrease of metastasis, and enlargement of the tumor-bearing mice survival time in comparison with PBS and pure immune adjuvant injected groups. Mass spectrometry analysis showed that the ~ 27/28 kDa band has numbers of proteins/polypeptides with a high degree of homology with cancer cells antigens which can be the reason for this cross-reactivity and anti-tumor immune response. Taking together, immunization with HCW antigens would be a promising approach in cancer immunotherapy after further investigations.

Gamma Radiation-Attenuated Toxoplasma gondii Provokes Apoptosis in Ehrlich Ascites Carcinoma-Bearing Mice Generating Long-Lasting Immunity

Purpose:

Pathological angiogenesis and apoptosis evasions are common hallmarks of cancer. A different approach to the antitumor effect of parasitic diseases caused by certain protozoans and helminthes had been adopted in recent years as they can affect many cancer characteristics. The present work is an attempt to assess the effect of gamma radiation-attenuated Toxoplasma gondii ME49 as an antiapoptotic and angiogenic regulator modifier on tumor growth aimed at improving cancer protective protocols.

Methods:

Attenuated Toxoplasma gondii ME49 was administered orally to mice 2 weeks before inoculation with Ehrlich ascites carcinoma to allow stimulation of the immune response. Hepatic histopathology and immune responses were determined for each group.

Results:

Marked suppression of the tumor proliferation with induction of long-lasting immunity by stimulating interferon γ and downregulating transforming growth factor β. The level of tumor promoting inflammatory markers (STAT-3 and tumor necrosis factor α), the angiogenic factors (vascular endothelial growth factor A, integrin, and matrix metallopeptidase 2 and matrix metallopeptidase 9), as well as nitric oxide concentration were significantly decreased. This was collimated with an improvement in apoptotic regulators (cytochrome-c, Bax, Bak, and caspase 3) in liver tissues of vaccinated mice group compared to Ehrlich ascites carcinoma-bearing one. Moreover, the histopathological investigations confirmed this improvement.

Conclusion:

Hence, there is an evidence of potency of radiation attenuated Toxoplasma vaccine in immune activation and targeting tumor cell that can be used as a prophylactic or an adjuvant in combination with chemotherapeutic drugs.

Immunization with Hydatid Cyst Wall Antigens Can Inhibit Breast Cancer through Changes in Serum Levels of Th1/Th2 Cytokines

Background

Hydatid cysts are the larval stage of Echinococcus granulosus, which lead to humoral and cellular immune responses in hosts. Such immune responses play a key role in the inhibition of tumor growth and cancers. To test this hypothesis, it was attempted not only to examine the changes in serum level of some Th1 and Th2 cytokines but also to find relationships between the cytokines and cancer in 4T1 breast cancer-bearing mice immunized with hydatid cyst wall (HCW) antigens.

Methods

Six to eight-week-old Balb/c female mice were immunized with alum, PBS and HCW antigens, including crude extract of HCW (laminated layer) 28 and 27 kDa protein bands (upper and lower bands) and then challenged with 4T1 breast cancer cells. The amounts of IL2, TNF-α, IFN-γ (Th1 cytokines), and IL4 (Th2 cytokine) were estimated using ELISA. Correlations between these cytokines and cancer parameters (tumor growth, metastasis, and survival) were determined by Pearson's correlation coefficients.

Results

Overall, HCW antigens increased the amounts of IL2, TNF-α, IFN-γ, and IL4. Pearson's correlation coefficients indicated reverse relationships between changes in amounts of these cytokines and tumor growth/metastasis. However, except for IL-4, all cytokines had a direct relationship with mouse survival.

Conclusions

The results of this study indicated that the inhibition of breast tumor growth and metastasis and improvement of survival in 4T1 mice immunized with HCW antigens, especially laminated layer and 27 kDa protein band can occur through a rise in the levels of cytokines.

The Recombinant Protein Based on Trypanosoma cruzi P21 Interacts With CXCR4 Receptor and Abrogates the Invasive Phenotype of Human Breast Cancer Cells

Trypanosoma cruzi P21 is a protein secreted by the parasite that plays biological roles directly involved in the progression of Chagas disease. The recombinant protein (rP21) demonstrates biological properties, such as binding to CXCR4 receptors in macrophages, chemotactic activity of immune cells, and inhibiting angiogenesis. This study aimed to verify the effects of rP21 interaction with CXCR4 from non-tumoral cells (MCF-10A) and triple-negative breast cancer cells (MDA-MB-231). Our data showed that the MDA-MB-231 cells expressed higher levels of CXCR4 than did the non-tumor cell lines. Besides, cytotoxicity assays using different concentrations of rP21 showed that the recombinant protein was non-toxic and was able to bind to the cell membranes of both cell lineages. In addition, rP21 reduced the migration and invasion of MDA-MB-231 cells by the downregulation of MMP-9 gene expression. In addition, treatment with rP21 blocked the cell cycle, arresting it in the G1 phase, mainly in MDA-MB-231 cells. Finally, rP21 prevents the chemotaxis and proliferation induced by CXCL12. Our data showed that rP21 binds to the CXCR4 receptors in both cells, downregulates CXCR4 gene expression, and decreases the receptors in the cytoplasm of MDA-MB-231 cells, suggesting CXCR4 internalization. This internalization may explain the desensitization of the receptors in these cells. Thus, rP21 prevents migration, invasion, and progression in MDA-MB-231 cells.

[Characteristics of exosomes secreted by Toxoplasma gondii-infected mouse dendritic DC2.4 cells]

OBJECTIVE

To investigate the changes in the exosomes secreted by mouse dendritic cell line DC2.4 after infection with Toxoplasma gondii and to analyze the possible regulatory mechanisms underlying such changes.

METHODS

The exosomes were extracted by ultracentrifugation from DC2.4 cells at 28 h after infection with Toxoplasma gondii. The morphology of the exosomes was examined with transmission electron microscopy, and the exosome size and density were determined using a nanoparticle tracker. High-throughput sequencing was carried out to identify the differentially expressed small RNAs in the exosomes derived from the infected cells.

RESULTS

T. gondii infection resulted in a significantly increased density of exosomes secreted by DC2.4 cells. Small RNA sequencing revealed that Toxoplasma infection caused an increase in the number of miRNAs and piRNAs in the exosomes. The significantly up-regulated piRNAs after the infection included piR-mmu-159, piR-mmu-1526, piR-mmu-9082, piR-mmu-17405, and piR-mmu-25576.

CONCLUSIONS

Toxoplasma infection causes accumulation and enrichment of exosomes secreted by DC2.4 cells with increased miRNAs and piRNAs in the exosomes.

Vaccination with gamma radiation-attenuated Toxoplasma gondii protects against ovarian infiltration in mice-bearing Ehrlich ascites carcinoma

Purpose: Cancer is one of the most common causes of mortality and morbidity worldwide. Vaccines have been emerged as an attractive approach for their capacity of eliciting long-term immune response targeting cancer cells. Attenuated avirulent Toxoplasma gondii stimulate immunity and activate antitumor cells thereby eliciting rejection of some established cancer. The purpose of this study was to evaluate the antitumor-protective capacity of vaccination with gamma radiation-attenuated T. gondii against ovarian penetration in Ehrlich ascites carcinoma (EAC)-bearing mice.Materials and methods: Forty-five mice were randomly divided into three groups as follows: nontumor-bearing (normal control); EAC-bearing group (EAC); and mice vaccinated orally with gamma radiation-attenuated T. gondii then inoculated 2 weeks later with EAC (TG + EAC). Survival rate, serum interleukin-12 (IL-12), and levels of IFN-γ mRNA, CD4, and CD8 in ovarian tissues homogenate were assessed. Also, ovarian histopathology and immunohistochemical expressions of metalloproteinase-2, CD34, and vimentin were determined.Results: The group vaccinated with attenuated T. gondii showed significantly increased survival rates, serum IL-12, and levels of IFN-γ, CD4, and CD8 in ovarian tissue homogenates as well as an enhancement of histopathological and immunohistochemical changes compared to EAC-bearing group.Conclusion: Vaccination with gamma radiation-attenuated T. gondii has the capacity to supply immunoprotective impact against ovarian invasion in EAC-bearing mice.

In vivo tumor-suppressing and anti-angiogenic activities of a recombinant anti-CD3ε nanobody in breast cancer mice model

Aim: Achievements in cancer immunotherapy require augmentation of a host's anti-tumor immune response for anti-cancer modality. Materials & methods: Different concentrations of recombinant anti-CD3 nanobody were administered at predetermined time intervals during a 24-day treatment period and then expression of angiogenic biomarkers including VEGFR2, MMP9 and CD31, as well as tumor cell proliferation marker ki67, was determined in tumor sections by immunohistochemistry. Furthermore, expression of cytokines was examined in peripheral blood of mice. Results: Based on our results, administration of nanobody could reduce biomarker expression in tumor sections. Tumor growth was also delayed and survival rate was increased in response to nanobody treatment. Moreover, expression of pro-inflammatory cytokines was reduced. Conclusion: In conclusion, we demonstrated that administration of nanobody could effectively suppress angiogenesis as well as tumor growth.

Analysis of the Differential Exosomal miRNAs of DC2.4 Dendritic Cells Induced by Toxoplasma gondii Infection

Toxoplasma gondii is an intracellular parasite that infects humans and other warm-blooded animals. Exosomes are endocytic-derived vesicles released by cells, representing an important mode of intercellular communication. In exosomes, specific molecules of proteins, lipids, and mRNAs or miRNAs have been detected, some of which are capable of transferring biologically active molecules to recipient cells. Dendritic cells (DCs) are the only antigen-presenting cells (APCs) that activate the initial immune response. In this study, high-throughput sequencing was used to analyze the exosomal miRNA profile of DC2.4 cells infected with Toxoplasma gondii for 28 h, compared with those of uninfected DC2.4 cells. Differential exosomal miRNAs (DEmiRs) from these two cell groups were analyzed. Through high-throughput sequencing, 3434 DEmiRs were obtained, and 12 stably enriched DEmiRNAs were verified by Reverse Transcription-quantitative Polymerase Chain Reaction (RT-qPCR) and selected for further analysis. The target genes of these 12 miRNAs were predicted with online analysis software and subjected to bioinformatics analyses including protein-protein interaction (PPI) network analysis, key driver analysis (KDA), gene ontology (GO) enrichment, and Kyoto encyclopedia of genes and genomes (KEGG) pathway analysis. These DEmiRs were found to be associated with a variety of biological processes and signaling pathways involved in host ubiquitin system, innate immunity, biosynthesis, and transferase activity and could be potential biomarkers for T. gondii infection.

Anti-Toxoplasma gondii antibodies attach to mouse cancer cell lines but not normal mouse lymphocytes

Toxoplasma gondii (T. gondii) is prevalent intracellular parasite and a cause of worldwide infection in the human population. An inhibitory effect of this parasite on cancer growth has been demonstrated in cell culture and animal models. To determine whether the anticancer activities of T. gondii are associated with host immune response, in the current study the reactivity of anti-T. gondii antiserum with the surface of cancer cell lines was investigated. Anti-T. gondii antibodies were raised in rabbit and the reaction of this antiserum in comparison with other anti-parasite antisera (anti-T. vaginalis, anti-hydatid cyst fluid, anti-protoscolices antigens) with mouse melanoma or breast cancer cells lines was investigated using flow cytometry. Anti-T. gondii antiserum reacted markedly with the surface of mouse melanoma and breast cancer cells, and less so with the normal mouse spleen lymphocytes. Meanwhile, the other anti-parasite antisera did not react strongly with the surface of cancer cells compared with normal mouse spleen lymphocytes. In summary, it has been demonstrated herein that anti-T. gondii antiserum may selectively react with the surface of mouse cancer cells but not with normal mouse spleen lymphocytes. Therefore, further study on anti-Toxoplasma antibodies may be useful for directing the application of selective drug delivery in cancer treatment.

Parasites as negative regulators of cancer

Several environmental factors (chemical, physical, and biological) can cause the initiation, promotion, and progression of cancer. Regarding the biological factors, several studies have found that infections caused by some bacteria, viruses and protozoan, and helminth parasites are related to carcinogenesis. However, in recent years a different approach has been implemented on the antitumor impact of parasitic diseases caused by some protozoan and helminths, mainly because such infections may affect several hallmarks of cancer, but the involved mechanisms still remain unknown. The beneficial effects reported for some parasitic diseases on tumorigenesis range from the induction of apoptosis, activation of the immune response, avoiding metastasis and angiogenesis, inhibition of proliferative signals, to the regulation of inflammatory responses that promote cancer. In this work, we reviewed the available information regarding how parasitic infections may modulate cancer progression. Despite the fact that specific mechanisms of action on tumors are not yet totally clear, we consider that detailed studies of the antitumor action of these organisms and their products could lead to the discovery and use of new molecules from these biological agents that may work as adjuvant therapy in the treatment of various types of cancer.

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

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

Microorganisms in the Treatment of Cancer: Advantages and Limitations

Cancer remains one of the major challenges of the 21st century. The increasing numbers of cases are not accompanied by adequate progress in therapy. The standard methods of treatment often do not lead to the expected effects. Therefore, it is extremely important to find new, more effective treatments. One of the most promising research directions is immunotherapy, including the use of specific types of microorganisms. This type of treatment is expected to stimulate the immune system for the selective elimination of cancer cells. The research results seem to be promising and show the intensive activation of the immune response as a result of bacterial stimulation. In addition, it is possible to use microorganisms in many different ways, based on their specific properties, that is, toxin production, anaerobic lifestyle, or binding substances that can be delivered to a specific location (vectors). This paper provides an overview of selected microorganisms which are already in use or that are in the experimental phase. Just like any other therapy, the use of microbes for cancer treatment also has some disadvantages. Nevertheless, this kind of treatment can supplement conventional anticancer therapy, giving cancer patients a chance and hope of recovery.

Concomitant Mycobacterium tuberculosis infection promotes lung tumor growth through enhancing Treg development

Lung cancer is the most common malignancy in humans. An increased population of CD4⁺Foxp3⁺ regulatory T cells (Tregs) in the tumor-associated microenvironment plays an important role in cancer immune evasion. The exact role and the involved mechanisms of concomitant H37Rv infection in non-small cell lung cancer (NSCLC) development are still not clear. Here, we showed that H37Rv infection promoted NSCLC cell growth with a higher percentage of Tregs found in draining lymph nodes. We also determined in vitro that H37Rv infection induced macrophage maturation and PD-L1 expression, which promoted Treg proportion, with enhanced proliferation suppression function. Mechanism analysis revealed that AKT-mTORC1 signal was important for PD-L1 expression induced by H37Rv infection. Suppressing of AKT-mTORC1 signal by rapamycin or raptor deficiency showed decreased PD-L1 levels which further reduced Treg proportion in a co-culture system. Finally, tumor-bearing mice injected with H37Rv plus rapamycin enhance the immune response of lung cancer compared with injected with H37Rv alone. This study demonstrated that concomitant H37Rv infection promote NSCLC tumor immune eacape through enhancing Treg proportion.

Macrophages Polarized by Expression of ToxoGRA15II Inhibit Growth of Hepatic Carcinoma

A growing body of evidence suggests that tumor-associated macrophages are deeply involved in the hepatocellular carcinoma proliferation and account for the large proportion of infiltrated cells in tumor tissues and play a major role in promotion of tumor growth. On the other hand, studies have demonstrated that Toxoplasma gondii virulence-associated molecule of dense granule protein (ToxoGRA15_II) tends to induce classically activated macrophages (M1) differentiation. Thus, we explored the M1 induced by ToxoGRA15_IIin vitro and its inhibitory impact on the proliferation, invasion, and metastasis of hepatic carcinoma in murine model. Here, we constructed recombinant plasmid of pegfp-gra15_II and subsequently ligate it to lentivirus (Lv) vector, with which RAW264.7 was transfected. The results showed that the transfected macrophages were polarized to M1. Coculture of the M1 with Hepa1-6 cells showed a remarkable inhibition of migration and invasion of the tumor cells and decreased expressions of matrix metalloproteinase (MMP)-9 and MMP-2 without notable apoptosis of Hepa1-6 cells. Subsequently, ToxoGRA15_II-polarized macrophages inoculated to tumor-bearing C57BL/6 mice were seen in both spleen and tumor tissues, and tumor growth was sharply restricted. Particularly, interleukin-6 (IL-6) expression, which is closely associated with the cancer malignant behaviors, was significantly dampened in tumor tissues. In addition, expression of TNF-α and IL-12 mRNAs was increased, whereas IL-6 and interleukin-10 mRNAs were downregulated in splenocytes. Our results indicate that the effector molecule of ToxoGRA15_II may induce macrophage polarization to M1 that has a restrictive effect on tumor growth via its related cytokines profile in tumor and spleen tissues. Besides, ToxoGRA15_II, due to its early activation of specified cell population and non-toxicity to mammalians, has a potential value for a novel therapeutic strategy of enhancing host innate immunity against tumor development.

Study on the mitochondrial apoptosis pathways of small cell lung cancer H446 cells induced by Trichinella spiralis muscle larvae ESPs

Trichinella spiralis (T.spiralis) muscle-larva (ML) excretory-secretory proteins (ESPs) contain antitumour-active substances. ESPs have been shown to inhibit tumour growth. To explore the effects of these proteins on small cell lung cancer cells and the possible mechanisms of their antineoplastic action, H446 SCLC cells were co-cultured with different concentrations of T. spiralis ML ESPs for 12, 24 and 48 h. Our results showed that T. spiralis ML ESPs significantly inhibited H446 cell proliferation, which was dose-and time-dependent. The results of flow cytometry testing indicate a clear apoptosis trend in H446 cells co-cultured with ESPs for 24 h. Reverse transcription polymerase chain reaction and Western blotting results showed increased expression of pro-apoptosis genes Bax, Cyt-C, Apaf-1, caspase-9 and caspase-3, compared with the negative control group, and decreased the expression of anti-apoptosis genes Bcl-2 and Livin. Our results suggest that T. spiralis ML ESPs can induce apoptosis in H446 cells through a mitochondrial pathway, which may be a mechanism of antineoplastic action in T. spiralis ML ESPs.

Ginkgo biloba exocarp extracts inhibits angiogenesis and its effects on Wnt/β-catenin-VEGF signaling pathway in Lewis lung cancer

ETHNOPHARMACOLOGICAL RELEVANCE

A fruit of Ginkgo biloba L. also known as Ginkgo biloba, can be used for the treatment of cancer in Chinese traditional medicine. The scientific name of succulent skin, which is the episperm of Ginkgo nuts, is exocarp. Experiment shows that Ginkgo biloba exocarp extracts (GBEE) has the effects of immune promotion, cancer inhibition and etc.

AIM OF STUDY

Study on the activity of GBEE against Lewis lung cancer (LLC) angiogenesis and its partial molecular mechanism.

MATERIALS AND METHODS

The effect of GBEE on proliferation of LLC cells was detected by MTT method in vitro. The metastasis model of LLC was set up. The C57BL/6J mice were randomly separated into normal control, model control, positive control and GBEE (50, 100, 200mg/kg) treatment groups, n=10. The mice in normal group and model group were both intragastric gavage (i.g.) normal saline (NS) in a volume of 0.1mL/10g (b.w.), positive group were intraperitoneal (i.p.) injection cyclophosphamide (CPA) at a dose of 20mg/kg (b.w.) , the GBEE treatment groups were respectively i.g. GBEE 50, 100, and 200mg/kg (b.w.), once a day for 20d. After treatment, we calculated the tumor inhibition rate and anti-metastasis rate. The microvessel density (MVD) was measured by immunohistochemistry method in transplanted tumor. The expression levels of vascular en-dothelial growth factor (VEGF) and VEGFR2 mRNA or Wnt3a, β-catenin, VEGF, VEGFR2 and p-Akt/Akt protein expression were respectively tested by Quantitative Reverse transcription Polymerase chain reaction (qRT-PCR) or western blot in vitro and vivo.

RESULTS

GBEE suppressed the growth of LLC cells in a dose-dependent way at the dose of 5, 10, 20, 40, 80 and 160µg/mL in vitro. It can suppressed Wnt3a and β-catenin protein expression and the content of mRNA of VEGF and VEGFR2 in LLC cells significantly. In vivo, we discovered GBEE can retard the growth of LLC transplanted tumor in a dose-dependent way at the dose of 50, 100, 200mg/kg, suppressing tumor lung metastasis. The expression of CD34 was reduced, which means MVD was inhibited and so do β-catenin, VEGF, VEGFR2 and p-AKT/AKT protein expression and VEGF and VEGFR2 mRNA expression levels in LLC transplanted tumor of C57BL/6 mice.

CONCLUSIONS

GBEE played the effects of anti-tumor and anti-metastatic depending upon the inhibition of tumor angiogenesis, which may be closely relevant to its effect in blockage of Wnt /β-catenin-VEGF signaling pathway in LLC.

Puzzling and ambivalent roles of malarial infections in cancer development and progression

Scientific evidence strongly suggests that parasites are directly or indirectly associated with carcinogenesis in humans. However, studies have also indicated that parasites or their products might confer resistance to tumour growth.Plasmodiumprotozoa, the causative agents of malaria, exemplify the ambivalent link between parasites and cancer. Positive relationships between malaria and virus-associated cancers are relatively well-documented; for example, malaria can reactivate the Epstein-Barr Virus, which is the known cause of endemic Burkitt lymphoma. Nevertheless, possible anti-tumour properties of malaria have also been reported and, interestingly, this disease has long been thought to be beneficial to patients suffering from cancers. Current knowledge of the potential pro- and anti-cancer roles of malaria suggests that, contrary to other eukaryotic parasites affecting humans,Plasmodium-related cancers are principally lymphoproliferative disorders and attributable to virus reactivation, whereas, similar to other eukaryotic parasites, the anti-tumour effects of malaria are primarily associated with carcinomas and certain sarcomas. Moreover, malarial infection significantly suppresses murine cancer growth by inducing both innate and specific adaptive anti-tumour responses. This review aims to present an update regarding the ambivalent association between malaria and cancer, and further studies may open future pathways to develop novel strategies for anti-cancer therapies.

Common antigens between hydatid cyst and cancers

Background:

Different research groups reported a negative correlation between cancers and parasitical infections. As an example, the prevalence of a hydatid cyst among patients with cancer was significantly lower than its prevalence among normal population. Tn antigens exist both in cancer and hydatid cyst. This common antigen may be involved in the effect of parasite on cancer growth. So in this work, common antigens between hydatid cyst and cancers have been investigated.

Materials and Methods:

Different hydatid cyst antigens including hydatid fluid, laminated and germinal layer antigens, and excretory secretory antigens of protoscolices were run in SDS PAGE and transferred to NCP paper. In western immunoblotting, those antigens were probed with sera of patients with different cancer and also sera of non-cancer patients. Also, cross reaction among excretory secretory products of cancer cells and antisera raised against different hydatid cyst antigen was investigated.

Results:

In western immunoblotting, antisera raised against laminated and germinal layers of hydatid cyst reacted with excretory secretory products of cancer cells. Also, a reaction was detected between hydatid cyst antigens and sera of patients with some cancers.

Conclusion:

Results of this work emphasize existence of common antigens between hydatid cyst and cancers. More investigation about these common antigens is recommended.

Influence of Toxoplasma gondii on in vitro proliferation and apoptosis of hepatoma carcinoma H7402 cell

OBJECTIVE

To discuss the influence of tachyzoite of Toxoplasma gondii (T. gondii) RH strain on proliferation and apoptosis of hepatoma carcinoma (HCC) H7402 cell.

METHODS

The HCC H7402 cell in logarithmic phase and tachyzoite of T. gondii RH strain in different concentrations (1 × 10(7)/mL, 2 × 10(7)/mL, 4 × 10(7)/mL, 8 × 10(7)/mL and 16 × 10(7)/mL) were co-cultured. CCK-8 was utilized to determine the inhibition rate of T. gondii tachyzoite on H7402 cell growth. Flow cytometry was used to detect the change of cell cycle. RT-PCR method was used to detect the expression of cyclinB1 and cdc2-two genes related to cell cycle. Western blot method was used to detect the expression of apoptosis-related proteins Caspase-3 and Bcl-2.

RESULTS

The tachyzoite of T. gondii RH strain can inhibit the proliferation of HCC H7402 cells. The inhibition rate of tumor cell growth increased with the increase of concentration of T. gondii tachyzoite. With the increase of concentration of T. gondii tachyzoite, the proportion of G0/G1 phase of H7402 cell increased, the proportion of S phase decreased, and PI value decreased accordingly. The expression of cyclinB1 and cdc2 genes decreased with the increase of the concentration of T. gondii tachyzoite. With the increase of the concentration of tachyzoite of T. gondii RH strain, the expression quantity of Caspase-3 in H7402 cell increased, but the expression quantity of Bcl-2 protein decreased.

CONCLUSIONS

T. gondii can inhibit the in vitro proliferation of HCC H7402 cell, and induce its apoptosis. This effect shows a trend of concentration-dependent increase. Moreover, it is related to the down-regulation of cyclinB1 and cdc2 (cell cycle-related genes), the increase of apoptosis-related protein Caspase-3, and the decrease of Bcl-2 expression.

Necrosis and apoptosis in Trichinella spiralis-mediated tumour reduction

It is known that infection with different pathogens, including helminths, can alter the progression of malignant or other diseases. We studied the effect of chronic Trichinella spiralis infection or muscle larvae excretory-secretory (ES L1) antigens on the malignant tumour growth in the mouse melanoma model system in vivo and in vitro. Our results confirmed that chronic infection with T. spiralis possesses the capacity to slow down the progression of tumour growth, resulting in an impressive reduction in tumour size. We found that the phenomenon could, at least partially, be related to a lower level of tumour necrosis compared to necrosis present in control animals with progressive malignancy course. An increased apoptotic potential among the low percentage of cells within the total tumour cell number in vivo was also observed. ES L1 antigen, as a parasitic product that is released during the chronic phase of infection, reduced the survival and slightly, but significantly increased the apoptosis level of melanoma cells in vitro. Our results imply that powerful Trichinella anti-malignance capacity does not rely only on necrosis and apoptosis but other mechanisms through which infection or parasite products manipulate the tumor establishment and expansion should be considered.

Effect of two hydatid cyst antigens on the growth of melanoma cancer in C57/black mice

Hydatid cyst is the larval stage of Echinococcus granulosus. In previous studies inhibitory effect of this parasite on cancer cell growth in culture medium has been shown. In this study effect of hydatid cyst antigens on tumor growth in experimental animals has been investigated. Two antigens of hydatid cyst including protoscolices excretory secretory antigen and hydatid fluid absorbed on alum as adjuvant were injected to two groups of C57/black mice as case groups. Control groups were injected with only saline and alum. All mice then were injected with melanoma cells. Both antigens reduced the tumor size in mice in case groups. The difference of tumor size in mice in case groups and control group was statistically significant. In conclusion, anti-tumor effect of hydatid cyst antigens may be related to antigenic similarities which exist between hydatid cyst and cancer cells.

Prominent IL-12 production and tumor reduction in athymic nude mice after Toxoplasma gondii lysate antigen treatment

Toxoplasma gondii is an intracellular protozoan parasite that causes a Th1 cellular immunity. Our previous study showed that T. gondii lysate antigen (TLA) treatment in S180 tumor-bearing mice resulted in tumor reduction by suppressing CD31 expression, a marker of angiogenesis. In the present study, to investigate tumor suppressive effect of TLA under the absence of T lymphocytes, athymic nude mice were compared with euthymic mice in the anti-tumorigenic effect triggered by TLA in CT26 tumors. According to the results, intratumorally injected TLA reduced tumor growth and TIMP-1 level, a metastatic marker, in both euthymic and athymic mice. TLA treatment led to a sharp increase in IL-12 expression in serum cytokine profiling of athymic mice, and increased MyD88 signals in macrophages derived from the bone marrow, implying the activation of innate immunity. The selective induction of IL-12 by TLA treatment had an anti-tumorigenic effect.

Mutual action of anticancer and antiparasitic drugs: are there any shared targets?

ABSTRACT 

Parasites and cancers have some common features. It has been shown that some parasites interfere with tumor growth. In addition, they both have common antigens such as the Tn antigen. A communal action of anticancer and antiparasitic drugs has been reported. This shared action may be related to common targets for these drugs in cancers and parasites. In this paper, mutual action of anticancer and antiparasitic drugs, with the aim of discussing shared targets of these drugs, has been reviewed.

Parasites and immunotherapy: with or against?

Immunotherapy is a sort of therapy in which antibody or antigen administrates to the patient in order to treat or reduce the severity of complications of disease. This kind of treatment practiced in a wide variety of diseases including infectious diseases, autoimmune disorders, cancers and allergy. Successful and unsuccessful immunotherapeutic strategies have been practiced in variety of parasitic infections. On the other hand parasites or parasite antigens have also been considered for immunotherapy against other diseases such as cancer, asthma and multiple sclerosis. In this paper immunotherapy against common parasitic infections, and also immunotherapy of cancer, asthma and multiple sclerosis with parasites or parasite antigens have been reviewed.

Targeting tumors with nonreplicating Toxoplasma gondii uracil auxotroph vaccines

Toxoplasma gondii is an intracellular parasite that has evolved to actively control its invaded host cells. Toxoplasma triggers then actively regulates host innate interleukin-12 (IL-12) and interferon-γ (IFN-γ) responses that elicit T cell control of infection. A live, nonreplicating avirulent uracil auxotroph vaccine strain (cps) of Toxoplasma triggers novel innate immune responses that stimulate amplified CD8(+) T cell responses and life-long immunity in vaccinated mice. Here, we review recent reports showing that intratumoral treatment with cps activated immune-mediated regression of established solid tumors in mice. We speculate that a better understanding of host-parasite interaction at the molecular level and applying improved genetic models based on Δku80 Toxoplasma strains will stimulate development of highly effective immunotherapeutic cancer vaccine strategies using engineered uracil auxotrophs.