Unveiling the anti-neoplastic potential of Schistosoma mansoni-derived antigen against breast cancer: a pre-clinical study

Abstract

Background: Cancer is a global health concern, with millions of new cases and deaths annually. Recently, immunotherapy has strengthened cancer treatment by harnessing the body's immune system to fight cancer. The search for advanced cancer immunotherapies has expanded to explore pathogens like parasites for their potential anti-neoplastic effects. While some parasites have shown promising results, the role of Schistosoma mansoni in breast cancer remains unexplored.

Methods: This pre-clinical study investigated the anti-neoplastic potential of autoclaved Schistosoma mansoni antigen against breast cancer. In vitro, autoclaved Schistosoma mansoni antigen was evaluated on the MCF-7 human breast cancer cell line, while in vivo experiments used a chemically induced breast cancer rat model to evaluate tumour growth, liver enzyme levels, and immune response. Histopathological and immunohistochemical analyses assessed changes in tumour tissue, cell proliferation (Ki-67), angiogenesis (CD31), immune cell infiltration (CD8⁺ T cells), regulatory T cells (FoxP3⁺), and programmed death ligand 1 (PD-L1) expression.

Results: In vitro, autoclaved Schistosoma mansoni antigen significantly reduced MCF-7 cell viability in a dose- and time-dependent manner. In vivo, autoclaved Schistosoma mansoni antigen treatment significantly reduced tumour weight and volume, improved liver enzyme levels, increased tumour necrosis, and decreased fibrosis. Immunohistochemical analysis revealed decreased Ki-67 and CD31 expression, indicating reduced cell proliferation and angiogenesis, respectively. Autoclaved Schistosoma mansoni antigen also enhanced immune responses by increasing CD8⁺ T cells infiltration and decreasing FoxP3⁺ expression, resulting in a higher CD8⁺ T cells/FoxP3⁺ ratio within the tumour microenvironment. Notably, PD-L1 expression was also downregulated, suggesting potential immune checkpoint inhibition.

Conclusions: Autoclaved Schistosoma mansoni antigen demonstrated potent anti-neoplastic activity, significantly reducing tumour growth and modulating the immune response within the tumour microenvironment. These results highlight autoclaved Schistosoma mansoni antigen's potential as a novel immunotherapy for breast cancer.

Keywords: Schistosoma; Breast cancer; MCF-7; Parasite immunotherapy.

Fig. 1

The graphical representations of percentage of MCF-7 cell viability using MTT assay after treatment with cisplatin and ASmA for 24 and 48 h. Data are significant at P < 0.05. ^aSignificant versus non-treated cells. ^bSignificant versus ASmA 24 h incubation. ^cSignificant versus cisplatin 24 h incubation. ^dSignificant versus ASmA 48 h incubation. ASmA autoclaved Schistosoma mansoni antigen

Fig. 2

Representative gross photographs of tumour tissues excised from the untreated DMBA group and DMBA- ASmA-treated group. DMBA dimethylbenz[a]-anthracene, ASmA autoclaved Schistosoma mansoni antigen

Fig. 3

Microphotograph of rat mammary tissue stained with haematoxylin and eosin (H&E) (A–G) and Masson trichrome (H–J). Section of control rat mammary tissue showing normal mammary architecture (A in H&E stain and H in Masson trichrome) × 40. B–D and I Mammary tissue section of DMBA group showing invasive ductal carcinoma with squamous metaplasia grade III B × 100, higher magnification showed atypical mitosis and bizzar shaped malignant cells with hyperchromatic nuclei C × 200 & D × 400; and marked dense fibrosis I × 200. E–G and J Mammary tissue section of DMBA-ASmA-treated group showing extensive areas of necrosis and inflammatory cells infiltrations with foci of remnants invasive carcinoma E × 100, F × 200 and G × 400 and less dense fibrosis J × 200. DMBA: dimethylbenz[a]-anthracene; ASmA: autoclaved Schistosoma mansoni antigen

Fig. 4

Morphometric analysis of: A necrosis index, B fibrosis index, C percentage of Ki-67 expression (proliferation index), D CD8⁺ T cells, FoxP3⁺ cells and CD8⁺ cells/FoxP3⁺ ratio, E PD-L1 expression, and F CD31 micro-vessels density Values were expressed as mean ± SE. Data are significant at P < 0.05. ^aSignificant versus normal control group ^bSignificant versus DMBA group. DMBA dimethylbenz[a]-anthracene, ASmA autoclaved Schistosoma mansoni antigen, SE standard error

Fig. 5

Microphotograph of rat mammary tissue stained with immunohistochemical analysis. A Ki-67 expression showing low proliferative index in normal group, high proliferative index in DMBA group, reduction in proliferative index in DMBA-ASmA-treated group. B CD8⁺ T cells expression in cell membrane of infiltrating T cells in mammary tissue sections. CD8⁺ antibody expression was reduced in DMBA group and were elevated in DMBA-ASmA-treated group. C FoxP3⁺ expression in the perinuclear and nuclear pattern of infiltrating T cells in mammary tissue sections. FoxP3.⁺ expression was increased in DMBA group and reduced in DMBA- ASmA-treated group. D PD-L1 expression, it was negative in sections of normal breast tissue. DMBA group showed high PD-L1 expression and DMBA-ASmA-treated group showed reduction in PD-L1 expression. E CD31 expressions highlighting the vessels and micro-vessels, normal group exhibited a normal pattern of CD31 expression, DMBA group showed obviously nested CD31 expression in between cancer cells. DMBA-ASmA-treated group showed few expressions of CD31. Black arrows point out the positive-stained cells. DMBA dimethylbenz[a]-anthracene, ASmA autoclaved Schistosoma mansoni antigen, PD-L1 programmed death ligand 1