Epidemiologic study of the relationship between schistosomiasis due to Schistosoma japonicum and liver cancer/cirrhosis

From the discovery of helminths to the discovery of their carcinogenic potential

Cancer involves a major aberration in the normal behaviour of cells, making them divide continuously, which interferes with the normal physiology of the body. The link between helminths and their cancer-inducing potential has been proposed in the last century. The exact pathway is still not clear but chronic inflammation in response to the deposited eggs, immune response against soluble egg antigens, and co-infection with a third party (a bacteria, a virus, or infection leading to a change in microbiome) seems to be the reasons for cancer induction. This review looks into the historical outlook on helminths along with their epidemiology, morphology, and life cycle. It then focuses on providing correlations between helminth infection and molecular mechanism of carcinogenesis by elaborating upon epidemiological, clinical, and surgical studies. While the cancer-inducing potential has been convincingly established only for a few helminths and studies point out towards possible cancer-inducing ability of the rest of the helminths elucidated in this work, however, more insights into the immunobiology of helminths as well as infected patients are required to conclusively comment upon this ability of the latter.

The role of helminths in the development of non-communicable diseases

Non-communicable diseases (NCDs) like cardiovascular disease, chronic respiratory diseases, cancers, diabetes, and neuropsychiatric diseases cause significant global morbidity and mortality which disproportionately affect those living in low resource regions including low- and middle-income countries (LMICs). In order to reduce NCD morbidity and mortality in LMIC it is imperative to understand risk factors associated with the development of NCDs. Certain infections are known risk factors for many NCDs. Several parasitic helminth infections, which occur most commonly in LMICs, have been identified as potential drivers of NCDs in parasite-endemic regions. Though understudied, the impact of helminth infections on the development of NCDs is likely related to helminth-specific factors, including species, developmental stage and disease burden. Mechanical and chemical damage induced by the helminth in combination with pathologic host immune responses contribute to the long-term inflammation that increases risk for NCD development. Robust studies from animal models and human clinical trials are needed to understand the immunologic mechanisms of helminth-induced NCDs. Understanding the complex connection between helminths and NCDs will aid in targeted public health programs to reduce helminth-induced NCDs and reduce the high rates of morbidity that affects millions of people living in parasite-endemic, LMICs globally.

A Schistosoma japonicum MicroRNA Exerts Antitumor Effects Through Inhibition of Both Cell Migration and Angiogenesis by Targeting PGAM1

MicroRNA (miRNA) is an important regulator for gene expression. Recent studies showed that some heterogenous miRNAs derived from both parasite and plant can regulate expression of mammalian gene in a cross-species or even a cross-kingdom manner. Here, we identified a Schistosoma japonicum miRNA (designated as sja-miR-61) that is present in the hepatocyte of mice infected with the parasite. The sja-miR-61 mimics significantly inhibited the migration of both mouse and human hepatoma cells in vitro. In a xenograft animal model, significant reductions of the tumor volume and weight were observed in mice inoculated with hepatoma cells transfected with sja-miR-61 mimics compared to the controls. We found that the in vivo inhibition of tumor growth was through its anti-angiogenesis activity. Mechanically, we identified the phosphoglycerate mutase 1 (PGAM1) gene as a target of sja-miR-61 and found that the sja-miR-61-mediated suppression of cell migration and anti-angiogenesis by cross-species down-regulation of PGAM1 expression. These data indicated that sja-miR-61 is a tumor suppressor miRNA that may have therapeutic potential for human cancers.

Neglected Agent Eminent Disease: Linking Human Helminthic Infection, Inflammation, and Malignancy

Helminthic parasitic infection is grossly prevalent across the globe and is considered a significant factor in human cancer occurrence induced by biological agents. Although only three helminths (Schistosoma haematobium, Clonorchis sinensis, and Opisthorchis viverrini) so far have been directly associated with carcinogenesis; there are evidence suggesting the involvement of other species too. Broadly, human helminthiasis can cause chronic inflammation, genetic instability, and host immune modulation by affecting inter- and intracellular communications, disruption of proliferation-anti-proliferation pathways, and stimulation of malignant stem cell progeny. These changes ultimately lead to tumor development through the secretion of soluble factors that interact with host cells. However, the detailed mechanisms by which helminths introduce and promote malignant transformation of host cells are still not clear. Here, we reviewed the current understanding of immune-pathogenesis of helminth parasites, which have been associated with carcinogenesis, and how these infections initiate carcinogenesis in the host.

Cross-Species Suppression of Hepatoma Cell Growth and Migration by a Schistosoma japonicum MicroRNA

Schistosoma japonicum eggs trapped in host liver secretes microRNA (miRNA)-containing extracellular vesicles (EVs) that can be transferred to host cells. Recent studies demonstrated that miRNAs derived from plants can modulate gene expression and phenotype of mammalian cells in a cross-kingdom manner. In this study, we identified a Schistosoma japonicum miRNA (e.g., Sja-miR-3096) that is present in the hepatocytes of mice infected with the parasite and has notable antitumor effects in both in vitro and in vivo models. The Sja-miR-3096 mimics suppressed cell proliferation and migration of both murine and human hepatoma cell lines by targeting phosphoinositide 3-kinase class II alpha (PIK3C2A). We generated a murine hepatoma cell line that stably expressed the pri-Sja-miR-3096 gene and demonstrated cross-species processing of the schistosome pri-miRNA to the mature Sja-miR-3096 in the mammalian cell. Importantly, inoculation of this cell line into the scapula and livers of mice led to a complete suppression of tumorigenesis of the hepatoma cells. Moreover, tumor weight was significantly reduced on intravenous administration of Sja-miR-3096 mimics. Thus, the schistosome miRNA-mediated antitumor activity occurs in host liver cells during schistosome infection, which may strengthen resistance of host to liver cancer, and discovery and development of such miRNAs may present promising interventions for cancer therapy.

Employing Parasite Against Cancer: A Lesson From the Canine Tapeworm Echinococcus Granulocus

Cystic echinococcosis (CE), a devastating zoonotic condition caused by the tapeworm Echinococcus granulosus, remain a significant public health problem worldwide. However, after a negative correlation between solid tumor and CE has been incidentally discovered, accumulating evidence have suggested that this parasite may induce anticancer effect through activating host immune response and secreting molecules with anticancer potential, which may provide some new understanding for immunotherapy. This article will review the evidence supporting the anticancer effect of E. granulosus and its underlying mechanisms and discuss the possible implications in immunotherapy.

Eugenol, a potential schistosomicidal agent with anti-inflammatory and antifibrotic effects against Schistosoma mansoni, induced liver pathology

Introduction

Schistosomiasis is one of the most prevalent parasitic infections in developing countries. Although chemotherapy is one of the main strategies in controlling the disease, it is less effective in reversal of schistosome-induced pathology especially in the chronic and advanced stages of schistosomiasis. New strategies and prospective therapeutic agents with antifibrotic effects are needed. Eugenol has a wide anti-inflammatory effect. In the present study, we investigated the possible antischistosomal effect of eugenol on Schistosoma mansoni.

Materials and methods

The murine model of S. mansoni was established in three groups of adult male Balb-c mice; group I (infected non-treated group) and groups II and III (infected groups) treated orally with eugenol and praziquantel (PZQ), respectively. The expression of the sensitive immunohistochemical marker α-smooth muscle actin (α-SMA) in schistosome-infected tissues was determined. In addition, parasitological, biochemical, and histological parameters that reflect disease severity and morbidity were examined.

Results

Eugenol treatment showed significant reduction in total worm burden by 19.2%; however, the oogram pattern showed no marked difference compared to that of the PZQ group. Yet, eugenol significantly reduced the serum levels of hepatic enzymes: aspartate aminotransferase and alanine aminotransferase. Histopathological examination revealed a significant reduction in both numbers and diameters of hepatic granulomata, which was consistent with reduction in collagen fiber deposition. Additionally, the antifibrotic effect of eugenol was validated by its considerable reduction in the expression of the sensitive marker α-SMA in both eugenol- and PZQ-treated groups.

Conclusion

Although eugenol could not totally eradicate adults of S. mansoni, the significant amelioration of liver enzymes and hepatic fibrosis potentiate eugenol’s role as a promising antifibrotic and a complementary antischistosomal agent.

Schistosoma japonicum MiRNA-7-5p Inhibits the Growth and Migration of Hepatoma Cells via Cross-Species Regulation of S-Phase Kinase-Associated Protein 2

MicroRNAs (miRNAs) play important roles in human diseases, such as cancer. Human miRNA-7-5p is a tumor suppressor miRNA that inhibits tumor growth by regulating multiple oncogenic signal pathways. Recently, studies revealed that plant miRNAs could regulate mammalian gene expression in a cross-kingdom manner. Schistosoma japonicum miRNA-7-5p (designated as sja-miR-7-5p) is conserved between the parasites and mammals. Thus, we investigated whether sja-miR-7-5p has similar antitumor activity to its mammalian counterpart. We first showed that sja-miR-7-5p was detected in host hepatocytes during S. japonicum infection. The sja-miR-7-5p mimics significantly inhibited the growth, migration, and colony formation of mouse and human hepatoma cell lines in vitro, and induced G1/G0 cell cycle arrest. In a xenograft animal model, the tumor volume and weight were significantly reduced in mice inoculated with hepatoma cells transfected with sja-miR-7-5p mimics compared with those transfected with NC miRNAs. Furthermore, the antitumor activity of sja-miR-7-5p was suggested by cross-species downregulation of the S-phase kinase-associated protein 2 gene in the host. Thus, sja-miR-7-5p is translocated into hepatocytes and exerts its anti-cancer activities in mammals, implying that sja-miR-7-5p might strengthen host resistance to hepatocellular carcinoma during schistosome infection.

Comparative analysis of knowledge on schistosomiasis japonica in the local people in the former endemic area in Yamanashi Prefecture, Japan: comparisons among the background of age and occupation

Eradication of schistosomiasis japonica in Yamanashi Prefecture was officially declared in 1996, and all surveillance and health campaign were finished by the end of 2001. Schistosomiasis control had been carried out by strong collaboration among local Government, local people and academia, thought which knowledge and experiences of the disease control were accumulated among the local people. It is 20^th anniversary of the disease eradication in Yamanashi. We planned to analyze the current situation whether the local people still keep the knowledge of schistosomiasis or not. There was no more knowledge kept in the middle school students, to whom the local Government did not educate about schistosomiasis. Among adult individuals, elderly people who have experienced endemic condition still know about it at almost comparable level as in the past. However, younger people who learned it in the primary school but no experience of the disease transmission started losing the knowledge. Those situations of the adult local people were compared with the veterinarian group. It was confirmed that the veterinarian group had correct and proper knowledge of schistosomiasis japonica not only in elderly groups, but also in younger age group. Considering that methods for control and prevention of infectious diseases are common to some extent, their knowledge and experiences would be applicable for other infectious diseases in future. Therefore, the knowledge would be worth keeping in the local people. Taken together, individuals with specialty, such as veterinarians, are expected to play roles in public health for promotion of health and welfare.

Role of microRNAs in schistosomes and schistosomiasis

Schistosomes, a class of parasitic trematode worms, cause schistosomiasis. Accumulating evidence suggests that microRNAs (miRNAs)-small, non-coding RNAs that are known to play critical regulatory roles in many organisms-may be involved in schistosome development and sexual maturation, as well as the pathogenesis of schistosomiasis. Schistosoma miRNAs, such as Bantam and miR-10, may be involved in the pathological processes of schistosomiasis, and recent studies suggest that schistosome-specific miRNAs (e.g., Bantam, miR-3479-3p) in the bloodstream of a final host could be used as biomarkers for schistosomiasis diagnosis. Furthermore, aberrant miRNAs, such as miR-223 and miR-454, can be produced by a host in response to schistosome infection, and these miRNAs may contribute to the pathogenesis of schistosomiasis-associated liver injury. Here, we summarize recent progress evaluating the relationship between schistosome miRNAs and schistosomiasis and discuss how these miRNAs can mediate the pathogenesis of schistosomiasis and be used as biomarkers for schistosomiasis diagnosis.

Bilharzia: Pathology, Diagnosis, Management and Control

More than one billion people travel internationally each year and approximately 100 million to the tropics. Schistosomiasis is a neglected tropical disease caused by trematode blood flukes of the genus Schistosoma. It currently infects over 250 million people worldwide and results in approximately 25 million disability adjusted life years lost. Clinical manifestations depend on the affected organ. Subtle morbidities have also been documented including: growth retardation, anaemia and poor cognitive function in children. While schistosomiasis has been eradicated from Japan and significantly reduced in parts of China and Egypt, transmission in many other regions remains ongoing due to the wide-spread distribution of the intermediate snail host, poor sanitation, lack of health education and decreasing compliance to mass drug administration. Integrated control has significantly reduced the burden of disease in China but considerable financial capital is needed if similar results are to be duplicated elsewhere. Human vaccination is in various stages of development, and once found, will become an integral part of future control. This comprehensive review examines the epidemiology, pathology, diagnosis, clinical management, prevention and control of the disease.

Deep sequencing-based identification of pathogen-specific microRNAs in the plasma of rabbits infected withSchistosoma japonicum

Circulating microRNAs (miRNAs) have received considerable attention as a novel class of biomarkers for the diagnosis of cancer and as signalling molecules in mediating intercellular communication. Schistosomes, the causative agents of schistosomiasis, live in the blood vessels of a mammalian host in the adult stage. In the present study, we characterized schistosome-specific small RNA populations in the plasma of rabbits infected withSchistosoma japonicum(S. japonicum) using a deep sequencing method and then identified five schistosome-specific miRNAs, including four known miRNAs (Bantam, miR-3479, miR-10 and miR-3096), and one novel miRNA (miR-0001, miRBase ID: sja-miR-8185). Four of the five schistosome-specific miRNAs were also detected by real-time RT–PCR in the plasma ofS. japonicum-infected mice. In addition, our study indicated that schistosome Argonaute 2/3 may be an excretory-secretory (ES) protein. In summary, our findings are expected to provide useful information for further development of novel biomarkers for the diagnosis of schistosomiasis and also for deeper understanding of the mechanism of host–parasite interaction.

New insight into the antifibrotic effects of praziquantel on mice in infection with Schistosoma japonicum

BACKGROUND

Schistosomiasis is a parasitic disease infecting more than 200 million people in the world. Although chemotherapy targeting on killing schistosomes is one of the main strategies in the disease control, there are few effective ways of dealing with liver fibrosis caused by the parasite infection in the chronic and advanced stages of schistosomiasis. For this reason, new strategies and prospective drugs, which exert antifibrotic effects, are urgently required.

METHODS AND FINDINGS

The antifibrotic effects of praziquantel were assessed in the murine models of schistosomiasis japonica. Murine fibrosis models were established by cutaneous infection with 14 ± 2 Schistosoma japonicum cercariae. Then, the mice of both chronic (8 weeks post-infection) and advanced (15 weeks post-infection) schistosomiasis were treated by gavage of praziquantel (250 mg/kg, once daily for 3 days) to eliminate worms, and followed by praziquantel anti-fibrosis treatment (300 mg/kg, twice daily for 30 days). The fibrosis-related parameters assessed were areas of collagen deposition, content of hydroxyproline and mRNA expressions of Col1α1, Col3α1, α-SMA, TGF-β, MMP9, TIMP1, IL-4, IL-10, IL-13 and IFN-γ of liver. Spleen weight index, alanine aminotransferase activity and liver portal venous pressure were also measured. The results showed that anti-fibrosis treatment improved liver fibrosis, splenomegaly, hepatic function, as well as liver portal hypertension. In order to confirm the anti-fibrotic properties of praziquantel, we established a CCL(4)-induced model and revealed that CCL(4)-induced liver fibrosis was inhibited by PZQ treatment for 30 days. Furthermore, we analyzed the effects of praziquantel on mouse primary hepatic stellate cells (HSCs). It is indicated that mRNA expressions of Col1α1, Col3α1, α-SMA, TGF-β, MMP9 and TIMP1 of HSCs were all inhibited after praziquantel anti-parasite treatments.

CONCLUSIONS

The significant amelioration of hepatic fibrosis by praziquantel treatment validates it as a promising drug of anti-fibrosis and offers potential of a new chemotherapy for hepatic fibrosis resulting from schistosomiasis.

Decision-model estimation of the age-specific disability weight for schistosomiasis japonica: a systematic review of the literature

Schistosomiasis is among the most prevalent parasitic infections worldwide. However, current Global Burden of Disease (GBD) disability-adjusted life year estimates indicate that its population-level impact is negligible. Recent studies suggest that GBD methodologies may significantly underestimate the burden of parasitic diseases, including schistosomiasis. Furthermore, strain-specific disability weights have not been established for schistosomiasis, and the magnitude of human disease burden due to Schistosoma japonicum remains controversial. We used a decision model to quantify an alternative disability weight estimate of the burden of human disease due to S. japonicum. We reviewed S. japonicum morbidity data, and constructed decision trees for all infected persons and two age-specific strata, <15 years (y) and ≥15 y. We conducted stochastic and probabilistic sensitivity analyses for each model. Infection with S. japonicum was associated with an average disability weight of 0.132, with age-specific disability weights of 0.098 (<15 y) and 0.186 (≥15 y). Re-estimated disability weights were seven to 46 times greater than current GBD measures; no simulations produced disability weight estimates lower than 0.009. Nutritional morbidities had the greatest contribution to the S. japonicum disability weight in the <15 y model, whereas major organ pathologies were the most critical variables in the older age group. GBD disability weights for schistosomiasis urgently need to be revised, and species-specific disability weights should be established. Even a marginal increase in current estimates would result in a substantial rise in the estimated global burden of schistosomiasis, and have considerable implications for public health prioritization and resource allocation for schistosomiasis research, monitoring, and control.

Schistosomiasis is a parasitic infection caused by a flatworm that disproportionately affects the world's poorest populations. Schistosomiasis is one of the most common infections worldwide, affecting over 207 million people in 76 countries. Current international estimates indicate that schistosomiasis has a minimal impact at the population level. This has contributed to its low prioritization in global health and subsequent resource allocation for disease control. However, recent studies indicate that these measures underestimate the extent of neglected tropical diseases, including schistosomiasis. Despite World Health Organization recommendations, the burden of schistosomiasis has not been re-examined in over a decade, and there are no established estimates for different types of schistosomiasis. The impact of symptoms associated with the Asian strain, Schistosoma japonicum, remains controversial. This study was conducted to provide an alternate measure of the burden of S. japonicum. We reviewed the literature and calculated a summary estimate for S. japonicum which was seven to 46 times greater than current measures for schistosomiasis. Findings suggest that current measures severely underestimate the extent of schistosomiasis, and urgently need to be revised. Further research is needed to examine the burden of schistosomiasis and other forgotten tropical diseases affecting the world's poorest people in endemic countries.

Association between Strongyloides stercoralis infection and biliary tract cancer

Infectious agents, including parasites, often have oncogenic potential. However, there has been no study on the association between Strongyloides stercoralis infection and cancer risk. Therefore, we investigated the relationship between S. stercoralis infection and the occurrence of hepato-pancreato-biliary cancer. This case-control study examined 1,654 patients aged>or=50 years in the Department of Medicine and Therapeutics, Ryukyu University Hospital, Okinawa, Japan, between 1991 and 2005. There were 196 patients with hepato-pancreato-biliary cancer and 1,458 control patients without cancer. The association between S. stercoralis infection and cancer was analyzed by logistic regression analysis adjusted for human T cell lymphotropic virus type 1 infection, age, and sex. The prevalence of S. stercoralis infection in controls and biliary tract cancer was significantly different at 7.5 and 18.4%, respectively (P=0.03, adjusted odds ratio 2.7, 95% confidence intervals 1.1-6.3). In conclusion, our study indicates that the prevalence of S. stercoralis infection in patients with biliary tract cancer appears significantly higher than that in control patients. Thus, we propose that S. stercoralis infection is a risk factor for biliary tract cancer.

Disease burden and epidemiology of soil-transmitted helminthiases and schistosomiasis in Asia: the Japanese perspective

The disease burden due to soil-transmitted helminthiases (STH) and schistosomiasis is not well documented in Asia. Both STH and schistosomiasis are chronic diseases but case detection is not easy because of the absence of clinical symptoms. STH and schistosomiasis are, however, endemic in Asia and their burden is significant. At the preparatory meeting for the Hashimoto Initiative in Japan in 1997, STH and schistosomiasis were categorized as Group 2 diseases. Parasitic infections in this category were well understood at the time but sophisticated control strategies were lacking. Japan has promoted comprehensive collaborative projects to reduce the burden of STH and schistosomiasis throughout Asia, creating an international network to collect epidemiological information and to implement and improve disease control, thus extending the school-based control method that had proved so successful in Japan.

A matched, case-control study of the association between Schistosoma japonicum and liver and colon cancers, in rural China

A study of liver and colon cancers and their association with a previous diagnosis of schistosomiasis was performed in rural Sichuan, China. The data analysed came from 127 liver-cancer and 142 colon-cancer patients, each matched, by age, gender, hospital and township, with one or two controls. The cancer cases were identified from the hospital records of three Sichuan counties (all of which have some level of endemic schistosomiasis japonicum): Meishan (66 liver and 54 colon cases), Pujiang (16 liver and 22 colon cases) and Xichang (45 liver and 66 colon cases). Each control was selected using the hospital records for the same year the matched case of cancer was diagnosed, when the control had been found to have an illness other than cancer. Previous schistosomal infection was determined by examining the medical records at the county hospitals, searching the records at the local schistosomiasis-control stations or health-surveillance units, and, when no written record could be found, by interviews with the subjects or their relatives. Given the extremely strong association between hepatitis and liver cancer in China, only data from hepatitis-negative pairs were used in the analyses. Previous schistosomal infection was found to be significantly associated with both liver cancer (odds ratio = 3.7; 95% confidence interval = 1.0-13) and colon cancer (odds ratio = 3.3; 95% confidence interval = 1.8-6.1). The results indicate a fraction of disease attributable to schistosomiasis of 24% for colon cancer, and (among the hepatitis-negative population) one of 27% for liver cancer.

Atopy, helminths, and cancer

There are two hypotheses for the primary function of the T(H)/IgE system: protection against helminths that 'spills over' into inappropriate allergic responses in the modern environment, or protection from a variety of environmental carcinogens and infectious diseases that is adaptive even today. We suggest that rather than being alternatives, these two hypotheses fit into a single causal framework. Atopic responses to helminths kill, inhibit, or expel the parasites, thereby reducing their debilitating effects, the most serious of which is bladder cancer. The ultimate (evolutionary) reason for the T(H)2/IgE system may be minimizing chances that multiple biotic and abiotic hazards and carcinogens will enter the body; in some tropical areas, helminths are the major proximate (immediate) triggers of this response.

Different levels of Schistosoma mansoni infection increased the mutagenicity of benzo(a)pyrene, the activity of aryl hydrocarbon hydroxylase and the formation of hepatic microsomal hydrogen peroxide

The present study investigates the influence of different levels of Schistosoma mansoni infection (60, 120, 180, 300, 600 cercariae per mice) after 33 days on the activity of aryl hydrocarbon hydroxylase (AHH) and the formation of hepatic hydrogen peroxide (H(2)O(2)) during the metabolic activation of benzo(a)pyrene [B(a)p]. Also, it shows the mutagenic effect of B(a)p at different levels of S. mansoni infection using Salmonella typhimurium TA 98 and TA 102 as a tester strains. High levels of H(2)O(2) production (222 nmol/mg protein) and AHH activity (240 pmol 3-OH B(a)p per mg protein) were seen at 300 cercariae per mice. Increasing histidine revertant colonies at TA98 and TA102 were detected at different levels of S. mansoni infection. These data clearly demonstrate that S. mansoni infection changes the mutagenicity of B(a)p, AHH activity, as well as enhancing the formation of hepatic H(2)O(2) generated during the metabolic activation of B(a)p in infected mice.