Structural bases that underline Trypanosoma cruzi calreticulin proinfective, antiangiogenic and antitumor properties

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.

Trypanosoma cruzi, Chagas disease and cancer: putting together the pieces of a complex puzzle

Considering the extensive and widespread impact on individuals, cancer can presently be categorized as a pandemic. In many instances, the development of tumors has been linked to endemic microbe infections. Among parasitic infections, Trypanosoma cruzi stands out as one of the most extensively discussed protozoans in the literature that explores the association between diseases of parasite origin and cancer. However, the effective association remains an unsolved paradox. Both the parasite, along with protozoan-derived molecules, and the associated antiparasitic immune response can induce alterations in various host cell pathways, leading to modifications in cell cycle, metabolism, glycosylation, DNA mutations, or changes in neuronal signaling. Furthermore, the presence of the parasite can trigger cell death or a senescent phenotype and modulate the immune system, the metastatic cascade, and the formation of new blood vessels. The interaction among the parasite (and its molecules), the host, and cancer undoubtedly encompasses various mechanisms that operate differentially depending on the context. Remarkably, contrary to expectations, the evidence tilts the balance toward inhibiting tumor growth or resisting tumor development. This effect is primarily observed in malignant cells, rather than normal cells, indicating a selective or specific component. Nevertheless, nonspecific bystander mechanisms, such as T. cruzi's adjuvancy or the presence of proinflammatory cytokines, may also play a significant role in this phenomenon. This work aims to elucidate this complex scenario by synthesizing the main findings presented in the literature and by proposing new questions and answers, thereby adding pieces to this challenging puzzle.

Calreticulin: Endoplasmic reticulum Ca2+ gatekeeper

Endoplasmic reticulum (ER) luminal Ca2+ is vital for the function of the ER and regulates many cellular processes. Calreticulin is a highly conserved, ER-resident Ca2+ binding protein and lectin-like chaperone. Over four decades of studying calreticulin demonstrate that this protein plays a crucial role in maintaining Ca2+ supply under different physiological conditions, in managing access to Ca2+ and how Ca2+ is used depending on the environmental events and in making sure that Ca2+ is not misused. Calreticulin plays a role of ER luminal Ca2+ sensor to manage Ca2+ -dependent ER luminal events including maintaining interaction with its partners, Ca2+ handling molecules, substrates and stress sensors. The protein is strategically positioned in the lumen of the ER from where the protein manages access to and distribution of Ca2+ for many cellular Ca2+ -signalling events. The importance of calreticulin Ca2+ pool extends beyond the ER and includes influence of cellular processes involved in many aspects of cellular pathophysiology. Abnormal handling of the ER Ca2+ contributes to many pathologies from heart failure to neurodegeneration and metabolic diseases.

Anti-Tumor Effect of Protoscolex Hydatid Cyst Somatic Antigen on Inhibition Cell Growth of K562

BACKGROUND AND OBJECTIVE

Today, cancer is one of the most important causes of death in the world, and so far, many treatment methods have been used in this field. Immunotherapy is considered one of the newest developments in this science, and it is still being investigated in some forms in different cancers and with a variety of antigens as well. One of the subsets of cancer immunotherapy is its treatment using parasitic antigens. The present study evaluated the effect of using somatic antigens of protoscoleces of Echinococcus granulosus on K562 cancer cells.

METHODS

In this study, hydatid cysts' protoscolex antigens were extracted, purified, and added to K562 cancer cells at three concentrations (0.1, 1, and 2 mg/ml) and on three times (24, 48, and 72 h). The number of apoptotic cells was compared to the control flask. The antigen concentration of 2 mg/ml was used as a control sample to investigate its cytotoxic effect on the growth of healthy HFF3 cells. Annexin V and PI tests were also performed to differentiate apoptosis from necrosis.

RESULTS

In flasks treated with hydatid cyst protoscolex antigen, all three concentrations significantly reduced the growth of cancer cells compared with the control flask, and concentration 2 of crude antigen significantly caused the death of cancer cells. Furthermore, more cancer cells underwent apoptosis by increasing the time of exposure to the antigen. On the other hand, flow cytometry results also showed that the amount of apoptosis has increased compared to the control group. In fact, Protoscolex hydatid cyst somatic antigens induce programmed cell death in K562 cancer cells while not having a cytotoxic effect on normal cells.

CONCLUSION

Therefore, it is suggested to do more research on the anti-cancer and therapeutic properties of the antigens of this parasite.

The many faces of parasite calreticulin

Calreticulin from parasites and its vertebrate hosts share ~50% identity and many of its functions are equally conserved. However, the existing amino acid differences can affect its biological performance. Calreticulin plays an important role in Ca2+ homeostasis and as a chaperone involved in the correct folding of proteins within the endoplasmic reticulum. Outside the endoplasmic reticulum, calreticulin is involved in several immunological functions such as complement inhibition, enhancement of efferocytosis, and immune upregulation or inhibition. Several parasite calreticulins have been shown to limit immune responses and promote infectivity, while others are strong immunogens and have been used for the development of potential vaccines that limit parasite growth. Furthermore, calreticulin is essential in the dialogue between parasites and hosts, inducing Th1, Th2 or regulatory responses in a species-specific manner. In addition, calreticulin participates as initiator of endoplasmic reticulum stress in tumor cells and promotion of immunogenic cell death and removal by macrophages. Direct anti-tumoral activity has also been reported. The highly immunogenic and pleiotropic nature of parasite calreticulins, either as positive or negative regulators of the immune response, render these proteins as valuable tools to modulate immunopathologies and autoimmune disorders, as well as a potential treatment of neoplasms. Moreover, the disparities in the amino acid composition of parasite calreticulins might provide subtle variations in the mechanisms of action that could provide advantages as therapeutic tools. Here, we review the immunological roles of parasite calreticulins and discuss possible beneficial applications.

Trypanosoma cruzi infection induces proliferation and impairs migration of a human breast cancer cell line

Breast cancer is considered the type of cancer that most affects women in the world. The triple negative breast cancer is considered aggressive with poor prognosis. In the 1930s Russian researchers observed that T. cruzi has tropism for tumor cells. Since then, this research field has been subject of a numerous of researches. Here, we proposed to investigate the impact of T. cruzi infection on proliferation and migration of triple negative breast cancer cell line (MDA-MB-231). T. cruzi showed high invasion and multiplication rate in MDA-MB-231 cell line. The infection promoted the multiplication of MDA-MB-231 cell, continuous cell lysis throughout of days of in vitro infection and impaired MDA-MB-231 cell migration. Taken together, these results demonstrated the high susceptibility of MDA-MB-231 cell to T. cruzi and suggested that molecules from T. cruzi may impair host cell migration with potential use to avoid metastasis.

Trypanosoma cruzi Antigenic Proteins Shared with Acute Lymphoblastic Leukemia and Neuroblastoma

Background. Research studies indicate that immunization with protein extracts of Trypanosoma cruzi, the protozoan parasite that causes Chagas disease, prevents the appearance of tumors in 60% of mice injected with the murine lung carcinoma tumor line. The molecular basis of this process is unknown, although the presence of specific antigens in tumor cells and on the surface of T. cruzi suggests an antiparasitic immune response, with an effective cross-reaction against cancer cells, hence the importance to identify the antigens involved and determine their potential as target cells in anticancer therapy. Aim. This study aimed to determine the presence of antigenic proteins of T. cruzi shared with acute lymphoblastic leukemia and neuroblastoma cells. Material and methods. To achieve this, polyclonal antibodies against T. cruzi were developed in rabbits, and reactivity was determined with protein extracts of acute lymphoblastic leukemia cells and neuroblastoma. The immunodetection of five different strains of T. cruzi against anti-T. cruzi polyclonal antibodies was also performed. Conclusion. The study allows the knowledge of the immunological interactions between cancer and parasites to be expanded and, therefore, contributes to the design of more and better projects that improve the therapeutic strategies applied in oncology.

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.

Is It Possible to Intervene in the Capacity of Trypanosoma cruzi to Elicit and Evade the Complement System?

Chagas' disease is a zoonotic parasitic ailment now affecting more than 6 million people, mainly in Latin America. Its agent, the protozoan Trypanosoma cruzi, is primarily transmitted by endemic hematophagous triatomine insects. Transplacental transmission is also important and a main source for the emerging global expansion of this disease. In the host, the parasite undergoes intra (amastigotes) and extracellular infective (trypomastigotes) stages, both eliciting complex immune responses that, in about 70% of the cases, culminate in permanent immunity, concomitant with the asymptomatic presence of the parasite. The remaining 30% of those infected individuals will develop a syndrome, with variable pathological effects on the circulatory, nervous, and digestive systems. Herein, we review an important number of T. cruzi molecules, mainly located on its surface, that have been characterized as immunogenic and protective in various experimental setups. We also discuss a variety of parasite strategies to evade the complement system - mediated immune responses. Within this context, we also discuss the capacity of the T. cruzi infective trypomastigote to translocate the ER-resident chaperone calreticulin to its surface as a key evasive strategy. Herein, it is described that T. cruzi calreticulin inhibits the initial stages of activation of the host complement system, with obvious benefits for the parasite. Finally, we speculate on the possibility to experimentally intervene in the interaction of calreticulin and other T. cruzi molecules that interact with the complement system; thus resulting in significant inhibition of T. cruzi infectivity.

The Interactions of Parasite Calreticulin With Initial Complement Components: Consequences in Immunity and Virulence

Because of its capacity to increase a physiologic inflammatory response, to stimulate phagocytosis, to promote cell lysis and to enhance pathogen immunogenicity, the complement system is a crucial component of both the innate and adaptive immune responses. However, many infectious agents resist the activation of this system by expressing or secreting proteins with a role as complement regulatory, mainly inhibitory, proteins. Trypanosoma cruzi, the causal agent of Chagas disease, a reemerging microbial ailment, possesses several virulence factors with capacity to inhibit complement at different stages of activation. T. cruzi calreticulin (TcCalr) is a highly-conserved, endoplasmic reticulum-resident chaperone that the parasite translocates to the extracellular environment, where it exerts a variety of functions. Among these functions, TcCalr binds C1, MBL and ficolins, thus inhibiting the classical and lectin pathways of complement at their earliest stages of activation. Moreover, the TcCalr/C1 interaction also mediates infectivity by mimicking a strategy used by apoptotic cells for their removal. More recently, it has been determined that these Calr strategies are also used by a variety of other parasites. In addition, as reviewed elsewhere, TcCalr inhibits angiogenesis, promotes wound healing and reduces tumor growth. Complement C1 is also involved in some of these properties. Knowledge on the role of virulence factors, such as TcCalr, and their interactions with complement components in host-parasite interactions, may lead toward the description of new anti-parasite therapies and prophylaxis.