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

Parasites and cancers: parasite antigens as possible targets for cancer immunotherapy

An adverse relationship between some parasite infections and cancer in the human population has been reported by different research groups. Anticancer activity of some parasites such as Trypanosoma cruzi, Toxoplasma gondii, Toxocara canis, Acantamoeba castellani and Plasmodium yoelii has been shown in experimental animals. Moreover, it has been shown that cancer-associated mucin-type O-glycan compositions are made by parasites, therefore cancers and parasites have common antigens. In this report anticancer activities of some parasites have been reviewed and the possible mechanisms of these actions have also been discussed.

Toxoplasmosis and Polygenic Disease Susceptibility Genes: Extensive Toxoplasma gondii Host/Pathogen Interactome Enrichment in Nine Psychiatric or Neurological Disorders

Toxoplasma gondii is not only implicated in schizophrenia and related disorders, but also in Alzheimer's or Parkinson's disease, cancer, cardiac myopathies, and autoimmune disorders. During its life cycle, the pathogen interacts with ~3000 host genes or proteins. Susceptibility genes for multiple sclerosis, Alzheimer's disease, schizophrenia, bipolar disorder, depression, childhood obesity, Parkinson's disease, attention deficit hyperactivity disorder (P  from  8.01E - 05  (ADHD)  to  1.22E - 71) (multiple sclerosis), and autism (P = 0.013), but not anorexia or chronic fatigue are highly enriched in the human arm of this interactome and 18 (ADHD) to 33% (MS) of the susceptibility genes relate to it. The signalling pathways involved in the susceptibility gene/interactome overlaps are relatively specific and relevant to each disease suggesting a means whereby susceptibility genes could orient the attentions of a single pathogen towards disruption of the specific pathways that together contribute (positively or negatively) to the endophenotypes of different diseases. Conditional protein knockdown, orchestrated by T. gondii proteins or antibodies binding to those of the host (pathogen derived autoimmunity) and metabolite exchange, may contribute to this disruption. Susceptibility genes may thus be related to the causes and influencers of disease, rather than (and as well as) to the disease itself.

Roles of Trypanosoma cruzi calreticulin in parasite-host interactions and in tumor growth

In Latin America, there are about 10-12 million people infected with Trypanosoma cruzi, the agent of Chagas' disease, one of the most important neglected tropical parasitism. Identification of molecular targets, specific for the aggressor or host cells or both, may be useful in the development of pharmacological and/or immunological therapeutic tools. Classic efforts in Chagas' disease explore those strategies. Although the immune system frequently controls parasite aggressions, sterile immunity is seldom achieved and chronic interactions are thus established. However, laboratory-modified immunologic probes aimed at selected parasite targets, may be more effective than their unmodified counterparts. Calreticulin (CRT) from vertebrates is a calcium binding protein, present mainly in the endoplasmic reticulum (ER), where it directs the conformation of proteins and controls calcium levels. We have isolated, gene-cloned, expressed and characterized T. cruzi calreticulin (TcCRT). Upon infection, the parasite can translocate this molecule from the ER to the surface, where it inhibits both the classical and lectin complement pathways. Moreover, by virtue of its capacity to bind and inactivate first complement component C1, it promotes parasite infectivity. These two related properties reside in the central domain of this molecule. A different domain, amino terminal, binds to endothelial cells, thus inhibiting their angiogenic capacity. Since tumor growth depends, to a large extent on angiogenesis, their growth is also inhibited.

Pulmonary exposure to single-walled carbon nanotubes does not affect the early immune response against Toxoplasma gondii

Background

Single-walled carbon nanotubes (SWCNT) trigger pronounced inflammation and fibrosis in the lungs of mice following administration via pharyngeal aspiration or inhalation. Human exposure to SWCNT in an occupational setting may occur in conjunction with infections and this could yield enhanced or suppressed responses to the offending agent. Here, we studied whether the sequential exposure to SWCNT via pharyngeal aspiration and infection of mice with the ubiquitous intracellular parasite Toxoplasma gondii would impact on the immune response of the host against the parasite.

Methods

C57BL/6 mice were pre-exposed by pharyngeal administration of SWCNT (80 + 80 μg/mouse) for two consecutive days followed by intravenous injection with either 1x10³ or 1x10⁴ green fluorescence protein and luciferase-expressing T. gondii tachyzoites. The dissemination of T. gondii was monitored by in vivo bioluminescence imaging in real time for 7 days and by plaque formation. The inflammatory response was analysed in bronchoalveolar lavage (BAL) fluid, and by assessment of morphological changes and immune responses in lung and spleen.

Results

There were no differences in parasite distribution between mice only inoculated with T. gondii or those mice pre-exposed for 2 days to SWCNT before parasite inoculum. Lung and spleen histology and inflammation markers in BAL fluid reflected the effects of SWCNT exposure and T. gondii injection, respectively. We also noted that CD11c positive dendritic cells but not F4/80 positive macrophages retained SWCNT in the lungs 9 days after pharyngeal aspiration. However, co-localization of T. gondii with CD11c or F4/80 positive cells could not be observed in lungs or spleen. Pre-exposure to SWCNT did not affect the splenocyte response to T. gondii.

Conclusions

Taken together, our data indicate that pre-exposure to SWCNT does not enhance or suppress the early immune response to T. gondii in mice.

Parasites and malignancies, a review, with emphasis on digestive cancer induced by Cryptosporidium parvum (Alveolata: Apicomplexa)

The International Agency for Research on Cancer (IARC) identifies ten infectious agents (viruses, bacteria, parasites) able to induce cancer disease in humans. Among parasites, a carcinogenic role is currently recognized to the digenetic trematodes Schistosoma haematobium, leading to bladder cancer, and to Clonorchis sinensis or Opisthorchis viverrini, which cause cholangiocarcinoma. Furthermore, several reports suspected the potential association of other parasitic infections (due to Protozoan or Metazoan parasites) with the development of neoplastic changes in the host tissues. The present work shortly reviewed available data on the involvement of parasites in neoplastic processes in humans or animals, and especially focused on the carcinogenic power of Cryptosporidium parvum infection. On the whole, infection seems to play a crucial role in the etiology of cancer.

Hydatid Cyst Protoscolices Induce Cell Death in WEHI-164 Fibrosarcoma Cells and Inhibit the Proliferation of Baby Hamster Kidney Fibroblasts In Vitro

Both in vitro and in vivo models have demonstrated that some parasites can interfere with tumor cell growth. The present study investigates the anticancer activity of hydatid cyst protoscolices on WEHI-164 fibrosarcoma cells and baby hamster kidney (BHK) fibroblast cells in vitro. Those above two cell types were treated with live hydatid cyst protoscolices or left untreated for control groups. After 48 h, lactate dehydrogenase (LDH) and cell counts were assayed for both treated cells and control groups. Following treatment with hydatid cyst protoscolices, cell proliferation of both cell types was inhibited, and lysis of fibrosarcoma cells increased. Based on these results, it appears that hydatid cyst protoscolices have strong anticancer activity, and additional studies are needed to further clarify the mechanisms of this activity.

Extracellular Trypanosoma cruzi calreticulin in the host-parasite interplay

Calreticulin (CRT) from vertebrates is a calcium-binding protein present mainly in the endoplasmic reticulum (ER). There, it directs the conformation of proteins and controls calcium levels. This review will focus on several extracellular roles of Trypanosoma cruzi CRT (TcCRT) in relation to its capacity to inhibit the complement system, mediate parasite infectivity, interfere with angiogenesis and, as a possible consequence, with tumor growth. The TcCRT antiangiogenic effect parallels with the capacity of T. cruzi infection to inhibit tumor development in vivo. Thus, the TcCRT, complement, and endothelial cell interactions seem to be an evolutionary adaptation to promote prolonged parasite-host relationships.

Lipoxin A4 and its analogue suppress the tumor growth of transplanted H22 in mice: the role of antiangiogenesis

Tumor angiogenesis plays an essential role in carcinogenesis, cancer progression, and metastasis. Some studies indicate that lipoxins, endogenous anti-inflammatory lipid mediators, might be involved in tumor angiogenesis; however, the governing mechanisms are still unknown. In the present study, we examined the effects of exogenous lipoxin A(4) (LXA(4)) in mouse hepatocarcinoma cell line (H22) and H22-bearing mice model. It was found that in H22 cells, LXA(4) inhibited the production of vascular endothelial growth factor and reduced hypoxia-inducible factor-1 alpha level. In addition, its analogue, BML-111, blocked the expression of vascular endothelial growth factor in serum and tumor sections from H22-bearing mice. H&E staining and immunostaining with antibodies against CD34 revealed that BML-111 suppressed tumor-related angiogenesis in vivo, but LXA(4) could not influence the proliferation of primary cultured human umbilical vein endothelial cells. The tumor growth was also inhibited by BML-111. We also found that BML-111 enhanced the in situ apoptosis while inhibiting macrophage infiltration in tumor tissue. The results provide new evidence that LXA(4) suppresses the growth of transplanted H22 tumor in mice through inhibiting tumor-related angiogenesis.

Antiangiogenic and antitumor effects of Trypanosoma cruzi Calreticulin

Background

In Latin America, 18 million people are infected with Trypanosoma cruzi, the agent of Chagas' disease, with the greatest economic burden. Vertebrate calreticulins (CRT) are multifunctional, intra- and extracellular proteins. In the endoplasmic reticulum (ER) they bind calcium and act as chaperones. Since human CRT (HuCRT) is antiangiogenic and suppresses tumor growth, the presence of these functions in the parasite orthologue may have consequences in the host/parasite interaction. Previously, we have cloned and expressed T. cruzi calreticulin (TcCRT) and shown that TcCRT, translocated from the ER to the area of trypomastigote flagellum emergence, promotes infectivity, inactivates the complement system and inhibits angiogenesis in the chorioallantoid chicken egg membrane. Most likely, derived from these properties, TcCRT displays in vivo inhibitory effects against an experimental mammary tumor.

Methodology and Principal Findings

TcCRT (or its N-terminal vasostatin-like domain, N-TcCRT) a) Abrogates capillary growth in the ex vivo rat aortic ring assay, b) Inhibits capillary morphogenesis in a human umbilical vein endothelial cell (HUVEC) assay, c) Inhibits migration and proliferation of HUVECs and the human endothelial cell line Eahy926. In these assays TcCRT was more effective, in molar terms, than HuCRT: d) In confocal microscopy, live HUVECs and EAhy926 cells, are recognized by FITC-TcCRT, followed by its internalization and accumulation around the host cell nuclei, a phenomenon that is abrogated by Fucoidin, a specific scavenger receptor ligand and, e) Inhibits in vivo the growth of the murine mammary TA3 MTXR tumor cell line.

Conclusions/Significance

We describe herein antiangiogenic and antitumor properties of a parasite chaperone molecule, specifically TcCRT. Perhaps, by virtue of its capacity to inhibit angiogenesis (and the complement system), TcCRT is anti-inflammatory, thus impairing the antiparasite immune response. The TcCRT antiangiogenic effect could also explain, at least partially, the in vivo antitumor effects reported herein and the reports proposing antitumor properties for T. cruzi infection.

In Latin America, 18 million people are infected with Trypanosoma cruzi, a protozoan that causes Chagas' disease. Vertebrate calreticulins (CRTs) are multifunctional, intra- and extracellular calcium binding, chaperone proteins. Since human CRT (HuCRT) inhibits capillary growth (angiogenesis) and suppresses tumor growth, the presence of these functions in T. cruzi CRT (TcCRT) may have interesting consequences in the host/parasite interactions. Previously, we have cloned and expressed TcCRT and shown that, when translocated from the endoplasmic reticulum to the area of trypomastigote flagellum emergence, it promotes infectivity, inactivates the complement system, an innate defense arm and inhibits angiogenesis in the chorioallantoid chicken egg membrane. TcCRT inhibits angiogenesis, since it interferes with endothelial cell multiplication, migration and capillary morphogenesis in vitro, as well as angiogenesis in rat aortic rings. The parasite molecule also displays important antitumor effects. In these activities, TcCRT is more effective than the human counterpart. Perhaps, by virtue of its capacity to inhibit angiogenesis, TcCRT is anti-inflammatory, thus impairing the antiparasite immune response. The TcCRT antiangiogenic effect could also explain, at least partially, the in vivo antitumor effects reported herein and the reports proposing antitumor properties for T. cruzi infection.

Suppressed CD31 expression in sarcoma-180 tumors after injection with Toxoplasma gondii lysate antigen in BALB/c mice

The anti-tumorigenic effects of Toxoplasma gondii (RH) antigens were studied in a murine sarcoma-180 tumor model. To determine the anti-tumor effects, the reduction in tumor size and expression of CD31 (an angiogenesis marker in the tumor tissue) were examined after injection of BALB/c mice with T. gondii lysate antigen (TLA) or formalin-fixed, proliferation-inhibited, T. gondii tachyzoites. Tumors were successfully produced by an intradermal injection of sarcoma-180 cells with plain Matrigel in the mid-backs of mice. After injection with TLA or formalin-fixed T. gondii tachyzoites, the increase in tumor size and weight nearly stopped while tumor growth continued in control mice that were injected with PBS. CD31 expression in TLA-treated or formalin-fixed T. gondii-injected mice was lower than the control mice. Accordingly, the present study shows that the treatment of mice with formalin-fixed T. gondii or TLA in the murine sarcoma-180 tumor model results in a decrease of both tumor size and CD31 expression.

Chronic bacterial osteomyelitis suppression of tumor growth requires innate immune responses

Clinical studies over the past several years have reported that metastasis-free survival times in humans and dogs with osteosarcoma are significantly increased in patients that develop chronic bacterial osteomyelitis at their surgical site. However, the immunological mechanism by which osteomyelitis may suppress tumor growth has not been investigated. Therefore, we used a mouse model of osteomyelitis to assess the effects of bone infection on innate immunity and tumor growth. A chronic Staphylococcal osteomyelitis model was established in C3H mice and the effects of infection on tumor growth of syngeneic DLM8 osteosarcoma were assessed. The effects of infection on tumor angiogenesis and innate immunity, including NK cell and monocyte responses, were assessed. We found that osteomyelitis significantly inhibited the growth of tumors in mice, and that the effect was independent of the infecting bacterial type, tumor type, or mouse strain. Depletion of NK cells or monocytes reversed the antitumor activity elicited by infection. Moreover, infected mice had a significant increase in circulating monocytes and numbers of tumor associated macrophages. Infection suppressed tumor angiogenesis but did not affect the numbers of circulating endothelial cells. Therefore, we concluded that chronic localized bacterial infection could elicit significant systemic antitumor activity dependent on NK cells and macrophages.

Effects of Toxoplasma gondii and Toxocara canis antigens on WEHI-164 fibrosarcoma growth in a mouse model

Cancer is the main cause of death in developed countries. However, in underdeveloped countries infections and parasitic diseases are the main causes of death. There are raising scientific evidences indicating that parasitic infections induce antitumor activity against certain types of cancers. In this study, the effects of Toxoplasma gondii and Toxocara canis egg antigens in comparison with Bacillus Calmette Guerin (BCG) (known to have anticancer distinctive) on WEHI-164 fibosarcoma transplanted to BALB/c mice was investigated. Groups of 6 male BALB/c mice injected with T. gondii antigen, BCG, or T. canis egg antigen as case groups and alum alone as control groups. All mice were then challenged with WEHI-164 fibrosarcoma cells. The mice were examined for growth of the solid tumor and the tumor sizes were measured every other day up to 4 wk. The mean tumor area in T. gondii, BCG, or alum alone injected mice in 4 different days of measurements was 25 mm(2), 23 mm(2), and 186 mm(2) respectively. Also the mean tumor area in T. canis injected mice in 4 different days was 25.5 mm(2) compared to the control group (alum treated) which was 155 mm(2). T. gondii parasites and T. canis egg antigens induced inhibition of the tumor growth in the fibrosarcoma mouse model. We need further study to clarify the mechanisms of anti-cancer effects.