Supplementation of Spirulina (= Arthrospira) Platensis Induces Immunosuppression through Increasing T-regulatory Cells in a Syngeneic Mouse Model of Breast Cancer

Spirulina (= Arthrospira) platensis has been reported to have several health-enhancing activities. To date, the anticancer and immunomodulatory effects of Spirulina platensis against breast cancer (BC) in an experimental model have not been fully explored. The aim of this study was to assess the anticancer and immunomodulatory effects of Spirulina (= Arthrospira) platensis against BC in a syngeneic mouse model of BC using two approaches (1) simultaneous treatment and (2) early treatment models. The simultaneous treatment model evaluated the effect of feeding Spirulina at the time of tumor induction to investigate if this can inhibit tumor growth and metastasis. The aim of the early treatment model was to study if feeding the mice with Spirulina daily for two weeks prior to tumor induction can prevent the onset, growth and spread of the BC. In both models, the total duration of Spirulina supplementation was 28 days. There were no differences in body weight (p > 0.05) and tumor volume (p > 0.05) between the simultaneous and early treatments. However, a marked increase (p < 0.05) in the T-regulatory (Treg) population was observed in mice from the simultaneous treatment groups compared to control animals. The findings suggest that Spirulina feeding may induce an immunosuppressive environment in the tumor-induced animal, which may work through increasing their Treg populations, thereby suppressing the host’s immune response to the tumor.