Until January 2024, a total of 182 research articles have demonstrated the potency of a wide range of parasites and their derivatives as potent anti-neoplastic activity verified in both in vitro and in vivo. The anti-neoplastic response of parasites against different cancer types is presented and summarized in Tables 1, 2, 3, 4, 5, 6, 7, and 8.

Table 1 a and b: in vitro and in vivo studies of the anti-neoplastic activity of different parasites against gastrointestinal cancers (colorectal cancer, gastric and esophageal cancers)Table 2 a and b: in vitro and in vivo studies of the anti-neoplastic activity of different parasites against hepato-pancreatic cancers (hepatocellular carcinoma and pancreatic cancer)Table 3 In vitro and in vivo studies of the anti-neoplastic activity of different parasites against lung cancerTable 4 In vitro and in vivo studies of the anti-neoplastic activity of different parasites against breast cancerTable 5 a–d: in vitro and in vivo studies of the anti-neoplastic activity of different parasites against hematological cancers (leukemia, lymphomas, multiple myeloma, and mastocytoma)Table 6 a and b: in vitro and in vivo studies of the anti-neoplastic activity of different parasites against connective tissue and bone cancers (sarcomas and bone tumors)Table 7 a and b: in vitro and in vivo studies of the anti-neoplastic activity of different parasites against skin cancers (melanoma and Merkel-cell carcinoma)Table 8 a–e: in vitro and in vivo studies of the anti-neoplastic activity of different parasites against miscellaneous cancers (gynecological cancers, prostate cancer, neuroglial and neural crest cancers, thymoma, and head and neck squamous cell carcinoma)Gastrointestinal cancers

Table 1a, b shows the in vitro and in vivo studies of the anti-neoplastic activity of different parasites against gastrointestinal cancers (Colorectal, Gastric, and Esophageal cancers).

Colorectal cancer (CRC)

Globally, colorectal cancer (CRC) is the third most commonly diagnosed cancer and the second leading cause of cancer-related deaths [56]. An effective therapy still does not exist, which necessitates an in-depth exploration of promising cancer immunotherapeutic modalities. Being an inflammatory-driven malignancy, the CRC microenvironment plays a crucial role in the behavior of the disease through the involvement of innate immunity. On the other hand, adaptive immunity has been found to play a role in cancer immunosurveillance [57].

Antineoplastic activity of helminth parasites against CRC

Despite the multiple factors that are listed to impose CRC, schistosomiasis is still a query-predisposing factor. Schistosomiasis is a neglected tropical parasitic disease that affects approximately 200 million people in the world’s tropical areas [58]. While there is conflicting evidence regarding the association between schistosomiasis and colon carcinogenesis in humans and experimental animals, the association between CRC and Schistosoma mansoni (S. mansoni) specifically is unjustified [59]. Interestingly, S. mansoni soluble egg antigen regulated the host’s immune system and achieved immunomodulation in an experimentally induced colitis model. It induced expansion of Foxp3+ Treg probably via an indirect antigen-presenting cells-mediated mechanism and direct effects on T cells. It attenuated experimentally trinitrobenzene sulfonic acid-induced colitis and protected mice from lethal inflammation [60]. Surprisingly, the soluble egg antigen of S. mansoni, which contains oncogenic antigens, was recently reported to have an unpredictable negative effect on colon cancer cell (CT26.WT) proliferation in vitro, even at high concentrations [61]. Interestingly, an earlier study in 1991 demonstrated the anti-neoplastic activity of S. mansoni antigen in a murine cancer model [62]. This is in agreement with a recent study by Eissa et al. [55] who reported a protective effect of the autoclaved S. mansoni cercarial antigen against chemically induced colon carcinogenesis in a murine model. It resulted in a notable reduction in the average size of lesions and the number of neoplasms per mouse. Additionally, schistosomal antigen provoked an immunomodulatory potential, as evidenced by a significant increase in serum interlukin-10 (IL-10), the percentage of splenic clusters of differentiation 4 T cells (CD4+ T cells), intestinal FoxP3+ Treg cells, and a significant decrease in serum IL-17 [55]. It is worth noting that in a series of previous studies, autoclaved parasitic antigens induced potent homologous protective immunity against experimental schistosomiasis [63], trichinellosis [64], toxoplasmosis [65], and leishmaniasis [66], as well as anti-cancer activity [39, 40, 55]. Their strong immunogenic potential was also capable of alleviating adjuvant-induced arthritis in a rat model [20] and has been demonstrated to be safe in both experimental studies and human clinical trials against leishmaniasis [67, 68]. These findings suggest that autoclaved parasitic antigens could be a promising, safe, and potent immunotherapeutic treatment. With advancements in technology, it will be possible to overcome challenges such as standardization or identification of the most antigenic components of these antigens. This could be a significant advancement in the pharmaceutical industry to develop nature-based therapeutics of parasitic origin that could target cancer, autoimmune diseases, and infectious diseases as well.

Another helminth parasite is Echinococcus granulosus (E. granulosus), the tapeworm that causes hydatid disease in humans; a cosmopolitan zoonotic disease [69]. It is transmitted by dogs or other canines, who act as definitive hosts, while herbivorous animals serve as intermediate hosts [70]. Humans can be sporadically infected and act as accidental intermediate hosts. Interestingly, there have been reports of anti-cancer effects associated with hydatid disease in humans [25, 29]. In an in vitro study, hydatid cyst fluid has been shown to exhibit anti-neoplastic activity by inducing apoptosis in a colon cancer cell line (C26) [71]. Moreover, vaccination with hydatid cyst fluid induced anti-neoplastic activity in a murine model, protecting against colon tumor growth in both prophylactic and therapeutic experimental trials [72]. Similarly, it was shown by Rostamirad et al. [73] that hydatid cyst antigens (hydatid cyst fluid, the 78 kDa fraction or live protoscolices); especially hydatid cyst fluid fraction significantly inhibited colon cancer tumor growth in BALB/c mice [73]. Furthermore, anti-hydatid cyst antibodies were able to identify cell surface and intracellular antigens in colon cancer cells (CT26) using flow cytometry. Proteomic analysis of colon cancer CT26 antigens cross-reacted with anti-hydatid cyst antibodies and hydatid cyst fluid identified two proteins: mortalin and creatine kinase M-type. Interestingly, CT26 mortalin showed 60% homology with E. granulosus hsp70 [72]. Thus, the anti-neoplastic activity of E. granulosus against CRC may be attributed to shared antigens and the development of an effective cross-reactive immune response against cancer cells.

Taenia solium (T. solium) is an intestinal tapeworm that is acquired by eating undercooked pork. Ingestion of pork meat that contains the larval stage, cysticercus cellulose, leads to human taeniasis. On the other hand, human cysticercosis/neurocysticercosis is a fecal–oral infection caused by ingesting eggs excreted in the feces of a human carrier of T. solium [74]. Interestingly, recombinant T. solium Calreticulin (rTsCRT) was documented to promote an in vitro anti-tumoral effect. It inhibited the growth of the colon cancer cells (SW480 cell line) in a dose-dependent manner by interacting with scavenger receptors [75]. Although the main role of calreticulin, an endoplasmic reticulum protein, in T. solium, is to control intracellular Ca+2 homeostasis, it also participates in the assembly and surface expression of major histocompatibility complex (MHC) class I molecules for antigen presentation to CD8+ T cells, as well as in cell motility, secretion pathways, gene transcription regulation, protein synthesis, cellular adhesion, and apoptosis [76].

Taenia crassiceps (T. crassiceps) is another tapeworm that inhabits the intestine of carnivores, with rodents acting as its natural intermediate hosts. Human infection is rare and usually described in individuals with severe immunodeficiency. In such cases, humans act as an accidental intermediate host where the cysticerci, the larval stage of T. crassiceps can be found in skeletal muscles, subcutaneous tissue, or even intraocular [77]. The impact of T. crassiceps infection on the progression of colon cancer and colitis-associated colorectal tumorigenesis in mice was investigated. Infection with this mesocestod parasite inhibited the colonic inflammatory responses and CRC formation as well as prevented goblet cell loss. It also led to increased expression of IL-4, activated macrophage markers in colonic tissue, and negatively affected the expression of pro-inflammatory cytokines. Additionally, T. crassiceps infection prevented the up-regulation of β-catenin and CXCR2 expression, which are both markers associated with colitis-associated colorectal tumorigenesis [78].

Trichinella spiralis (T. spiralis), a tissue-dwelling helminth, causes human trichinellosis through ingestion of undercooked pork meat containing the parasite’s infective larvae. It possesses potent immunomodulatory properties and can stimulate anti-tumor immunity [79]. Trichinella spiralis infection has been shown to induce inhibition of HCT-8 colorectal carcinoma in BALB/c mice as demonstrated by a decrease in size and weight of tumors [80].

Toxocara canis (T. canis), a dog-specific nematode that can infect humans and cause visceral larva migrans and ocular larva migrans syndrome, has also shown an anti-neoplastic activity against colon cancer [81, 82]. Toxocara canis-derived peptides, specifically the synthesized peptide fraction from the excretory–secretory Troponin protein peptide, were able to induce cellular changes and decrease cellular viability in colon carcinoma cell lines (HT-29 and Caco2) in a dose-dependent manner and significantly altered the cellular expression of gene (Mcl-2, APAF1, ZEB1, VEGF, cyclin-D1, and caspase-3) involved in cancer progression [82].

In another study, derived antigens as well as excretory/secretory products (ES) from adult Heligmosomoides polygyrus (H. polygyrus), a gastrointestinal helminth parasite of rodents, significantly reduced the in vitro proliferation of murine (CT26.WT) colorectal cancer cells. Heligmosomoides excretory/secretory products (HES) alone are also significantly reduced the in vitro proliferation of human (HCT116) colorectal cancer cells, potentially through an increase in cell cycle arrest rather than cell apoptosis [61].

Antineoplastic activity of protozoan parasites against CRC

Apart from helminths, Trypanosoma cruzi (T. cruzi), a flagellated protozoan parasite that causes Chagas’ disease in humans possesses anti-cancer activities. This finding was first reported by Russian researchers Roskin and Exempliarskaia in 1931 who observed the tropism of T. cruzi toward tumor cells [83]. Later on, the anti-cancer activity of T. cruzi was further reported in several studies [84,85,86]. The anti-neoplastic activity of T. cruzi against CRC has been demonstrated in several in vitro and in vivo studies. Rats chronically infected with T. cruzi demonstrated a low incidence of chemically induced colon cancer [87]. Additionally, vaccination with T. cruzi epimastigote lysates strongly inhibited colon cancer development in a rat model and evoked an integrated anti-tumor response involving both the cellular and humoral components of the immune response. Interestingly, rats developed specific antibodies upon vaccination with T. cruzi epimastigote lysates that cross-reacted in vitro with human colon cancer cells. This indicates that T. cruzi and colon cancer cells could share common antigens and were capable of mediating antibody-dependent cellular cytotoxicity [52]. A candidate probable antigen is the mucin-type cancer-associated sialyl-Tn antigen (sialic acid-GalNAc-O-Ser/Thr), previously characterized in T. cruzi [88]. Thus, protection induced by T. cruzi infection or antigens against colon cancer in rat models possibly explains the absence of colorectal cancer in patients with chagasic megacolon [26].

Malaria is a disease caused by an intracellular protozoan parasite, Plasmodium (P.). It is the most common parasitic infection in both humans and animals. Studies have indicated that Plasmodium infection can activate the immune system’s defense against cancer. In a recent experimental study, infecting colon-cancer-bearing mice with P. yoelii 17XNL-infected erythrocytes resulted in a reduction in tumor weight and size. This was achieved by inhibiting proliferation and promoting mitochondria-mediated apoptosis in colon cancer cells [89]. It was also reported that the refined malaria protein rVAR2 binds specifically and with high affinity to chondroitin sulfate from various cancer cell lines. This targeted tumor characteristic makes rVAR2 a promising candidate for anti-cancer drug delivery. In fact, a complex formed by conjugating rVAR2 with a hemiasterlin analog (KT886) named (VDC886) was found to have strong cytotoxicity to 33 cancer cell lines in vitro including human colon cancer cells (Colo 205) with inhibitory concentrations 50 (IC50) values ranging from 0.2 pM to 30 nM [90]. Interestingly, in an in vitro study, it was demonstrated that a recombinant circumsporozoite protein, the main surface protein of the malaria parasite’s sporozoite stage, inhibited the proliferation of the human colon cancer cell line, SW480 in a dose-dependent manner. It also induced apoptosis in SW480 cells by suppressing the activation of the nuclear factor κB (NF-κB). Blocking NF-κB activation is a promising strategy for cancer treatment. Further research is needed to investigate the potential use of circumsporozoite protein as a novel NF-κB inhibitor for treating colorectal cancer [91].

Toxoplasma gondii (T. gondii) is a protozoan parasite that has attracted attention for its potential anti-cancer effects. It infects a wide variety of warm-blooded animals, and about one-third of the world’s population is infected with it. T. gondii is able to infect many different types of cells and alter the immune response of the host, which makes it a possible candidate for use in human medicine as a potential oncolytic protozoan [92]. In vitro studies demonstrated that the dense granular protein 16 of T. gondii (GRA16) can act as a new telomerase inhibitor, an excellent candidate for gene therapy targeting cancer. It induced apoptosis in HCT116 human colorectal cancer cells by down-regulating the expression of human telomerase reverse transcriptase. This led to the shortening of telomere through the inactivation of telomerase, which was achieved by activating the tumor suppressor phosphatase and tension homolog [93]. Interestingly, conjugation of GRA8, a dense granule protein of T. gondii, with the acidity-triggered rational membrane (ATRAM) forming (rATRAM-GRA8-M/AS) induced HCT116 cell death in a dose-dependent manner via mitochondrial metabolic resuscitation pathways. Furthermore, rATRAM-GRA8-M/AS demonstrated significant therapeutic effects in a mouse model with HCT116 xenografts, with noticeable inhibition in tumor growth in mice [94]. Additionally, in a mouse model of colon adenocarcinoma (MC38), intratumoral administration of attenuated T. gondii tachyzoites (RH-ΔGRA17) strain with programmed death ligand-1 (PD-L1) blockade significantly improved the survival of mice and halted tumor growth compared to each treatment alone. This treatment also increased lymphocyte infiltration and sensitized the microenvironment in local and distant tumors to systemic PD-L1 blockade treatment [95]. Likewise, intratumoral injection of Toxoplasma lysate antigen in CT26 tumor-bearing Athymic nude mice and euthymic mice reduced tumor growth and TIMP-1 level, a metastatic marker, in both mouse models. In Athymic mice, Toxoplasma lysate antigen treatment led to a sharp increase in serum IL-12, and MyD88 signals in bone marrow-derived macrophages, suggesting activation of innate immunity. The selective induction of IL-12 by Toxoplasma lysate antigen treatment had an anti-tumorigenic effect [96].

In T. gondii, the profilin-like protein (TgPLP) acts as a Toll-like receptor (TLR) agonist. A study demonstrated that recombinant profilin-like protein in T. gondii (TgPLP) could serve as a TLR-based vaccine adjuvant, enhancing anti-tumor immune responses upon vaccination with autologous whole-tumor cell vaccine (AWV) that was exhibited by prolonged mice survival and smaller CT26 tumors. Additionally, TgPLP treatment triggered immune responses as evidenced by increased expression of antigen-presenting cell markers (MHC class I and II, B7.1, and B7.2) in bone marrow-derived macrophage and increased IL-12 and IFN-γ expression in mice. Mice vaccinated with AWV and TgPLP showed more immune cells [CD4+ and CD8+ T cells, natural killer (NK) cells, and macrophages] in the spleen and higher total IgG and IgG2a concentrations in the blood than mice vaccinated with AWV alone [97].

Similarly, the amino-terminus region of the dense granule protein 6 (GRA6Nt) of T. gondii has been shown to activate cancer-specific immunity. In a mouse model of MC38 CRC, the recombinant GRA6Nt (rGRA6Nt) protein acts as an effective adjuvant when combined with non-replicable MC38 colorectal cancer cells treated with mitomycin C or a lethal dose of ionizing radiation. This immunization approach markedly activates protective immunity against replicable MC38 tumor cells challenge, leading to significant inhibition of tumor growth and a marked increase in the infiltration of CD8+ T cells in the tumor microenvironment. The CD8+ T cells also showed increased activity in secreting granzyme B and IFN-γ in response to cancer cells in vitro. Importantly, this immunization approach is specific to MC38 CRC cells and did not significantly inhibit the growth of EL4 lymphoma tumors [98]. Therefore, both the recombinant Profilin-like protein (rTgPLP) and the recombinant GRA6Nt of T. gondii have the potential as powerful adjuvants for cancer cell vaccines used in cancer immunotherapy to effectively activate their specific protective immunity.

Recent studies have shown that the use of an exosome-based strategy instead of live parasite infections could be a safe alternative approach for clinical applications in treating cancer [99, 100]. Exosomes derived from culture supernatants of DCs infected with T. gondii Me49 strain induced an anti-tumor effects CRC mouse model. These exosomes significantly slowed tumor growth, inhibited macrophage polarization to M2 phenotype, and regulated the suppressor of cytokine signaling 1 (SOCS1) expression by delivering functional miR-155-5p [100]. Furthermore, a subsequent study showed that these exosomes reduced the proportion of polymorphonuclear granulocytic bone marrow-derived suppressor cells (G-MDSCs, CD11b+Ly6G+) and monocytic myeloid-derived suppressor cells (M-MDSCs, CD11b+Ly6C+), while significantly increased the proportion of DCs (CD45+CD11c+). There was also a significant decrease in the levels of IL-6 and granulocyte–macrophage colony-stimulating factor. The exosomes achieved such an impact by inhibiting the signal transducer and activator of the transcription signaling pathway. Thus, exosomes derived from DCs infected with T. gondii could potentially be a new cancer treatment strategy decreasing the proportion of MDSCs and altering the “cold” tumor to a “hot” tumor. These exosomes could also be modified for drug and antibody delivery. These findings could lead to a new approach for treating CRC [99].

Eimeria spp. is another apicomplexan intestinal protozoan parasite of domestic animals. Interestingly, domestic animals known to maintain this parasite in their small intestinal tissues have a very low incidence of colon cancer. In humans, cyst-forming coccidia parasites belonging to phylum Apicomplexa, with life cycles like Eimeria, are maintained through the use of night soil as fertilizer. Therefore, a research study investigated the impact of using human excrement (night soil) as a fertilizer on the development of human colon cancer. Japan’s mortality data demonstrated that colon cancer increased after the cessation of night soil use [101]. Thus, the presence of protozoa within intestinal tissue layers may enhance the immune system and prevent colon cancer, and the loss of these organisms could lead to a higher incidence of colon cancer. The authors consider this to be similar to the helminth hypothesis and an extension of the hygiene hypothesis [101].

These findings were further supported by a recent study by Huang and colleagues, who demonstrated that Eimeria stiedae (E. stiedae) soluble protein is an extremely effective activator of innate immunity in mice. In the murine model of colon cancer (CT26), it enhanced the anti-tumor immune response, inhibited tumor growth, promoted dendritic cell maturation, and activated natural killer cells and CD8+ T cells. Additionally, it inhibited angiogenesis and metastasis as demonstrated by the significant reduction in the number of metastatic lung nodules. Thus, Eimeria surface protein could play an important role in the treatment of cancer and has the potential to prevent tumor metastasis, which is a leading cause of cancer-related death in patients with colorectal cancer as well as other solid tumors [102].

Gastric and esophageal cancers

Gastric and esophageal cancers are prevalent and have high mortality rates. Patients are usually diagnosed at an advanced stage, leading to poor survival outcomes. Despite advancements in cancer treatments, survival rates remain low, highlighting the need for ongoing research to improve treatment strategies [103].

Antineoplastic activity of helminth parasites against gastric and esophageal cancers

Studies have shown that the helminth nematode parasites T. spiralis and T. canis have anti-neoplastic activity against gastric cancer. In an in vitro study, T. canis synthesized Troponin protein peptide, a fraction from the excretory–secretory antigens, was able to induce cellular changes and decrease cellular viability in a gastric cancer cell line (AGS) in a dose-dependent manner. It also significantly altered the cellular expression of genes (Mcl-2, APAF1, ZEB1, VEGF, cyclin-D1, and caspase-3) involved in cancer progression [82]. In addition, the extract of T. spiralis from adults and newborn larvae inhibited tumor growth in mice grafted with murine forestomach carcinoma (cell line MFC) [104].

Antineoplastic activity of protozoan parasites against gastric and esophageal cancers

Apart from helminths, live T. gondii tachyzoites have been found to have a significant inhibitory effect on human esophageal carcinoma cells (EC-109 cell line) in a dose-dependent manner [