From pathogen to cure: exploring the antitumor potential of Toxoplasma gondii

Abstract

Toxoplasma gondii (T. gondii), an intracellular protozoan parasite, has attracted significant attention in recent years for its dual role in both promoting and inhibiting cancer. Although traditionally recognized as a potential risk factor for tumor development, particularly in immunocompromised individuals, emerging research suggests that T. gondii may possess anti-cancer properties. This paradox is rooted in the parasite’s ability to modulate the host’s immune system, triggering antitumor immune responses through the activation of immune cells and the secretion of cytokines such as TNF-α and IFN-γ. T. gondii has demonstrated efficacy in reversing tumor-associated immunosuppression, inhibiting angiogenesis, and promoting tumor regression in preclinical models. However, its potential as an immunotherapeutic agent is tempered by the risks associated with administering live parasites, including infection and immune system complications. This article reviews the current understanding of T. gondii impact on cancer and its potential role in cancer therapy. Despite promising preclinical results, challenges remain, including the need for safer therapeutic approaches. Future research should focus on genetically modified or attenuated strains of T. gondii that retain their antitumor capabilities while minimizing risks. Understanding the underlying mechanisms by which T. gondii modulates the tumor microenvironment will be crucial for translating these findings into clinical applications, potentially offering new avenues for cancer treatment.

Keywords: Toxoplasma gondii; Antitumor immunity; Cytokine modulation; Immunotherapy; Tumor microenvironment.

Fig. 1

Immunomodulatory Effects of Toxoplasma gondii in Enhancing Antitumor Responses. T. gondii infection significantly increases the expression of inflammatory markers, such as CD80 and CD86, in dendritic cells (DCs), which are key antigen-presenting cells in the immune system. This upregulation is critical for the maturation of DCs, enabling them to effectively present antigens in conjunction with MHC class II molecules and activate T cells. Mature DCs stimulate the differentiation of CD4 + T cells into the Th1 subset, which secretes interleukin-12 (IL-12) and interferon-gamma (IFN-γ). The IL-12/IFN-γ axis is pivotal in the antitumor response, as IFN-γ induces apoptosis in cancer cells and enhances the cytotoxic activity of CD8 + T cells and natural killer (NK) cells. In addition to cellular immunity, T. gondii also promotes a humoral response by stimulating some CD4 + T cells to activate B cells, leading to the production of specific IgG antibodies against tumor antigens. This antibody-mediated response further supports the immune system in combating cancer cells. Moreover, T. gondii infection recruits CD4 + and CD8 + T cells and macrophages into the tumor microenvironment (TME). These immune cells secrete IL-12 and IFN-γ, thereby amplifying the antitumor immune response and inhibiting tumor growth

Fig. 2

Mechanisms of the Antitumor Activity of Toxoplasma gondii Involving Immune Cells