Abstract

Spirulina platensis is a cyanobacteria species that contains a TLR2 agonist and phycocyanin that supports probiotic health care through innate immunity. The oral administration of hot water-extracted spirulina (spirulina extract) induced NK cell activation and shrunk the NK-sensitive tumors loaded onto mice. However, it remains undetermined whether spirulina extract contributes to provoking T cell immunity represented by the tumor-specific induction of cytotoxic T lymphocytes (CTLs). Using a mouse model comprised of mice with CTL-sensitive tumors and a diet consisting of spirulina extract, we found that tumor-specific CTLs were spontaneously activated by spirulina extract in some mice, in which tumor regression was observed in a CTL-dependent manner. CTLs were induced without an injection of extrinsic tumor-associated antigen (TAA). These results indicated that the spirulina extract affected the activation of both NK cells and CTLs in the gut microbial environment to induce tumor regression in some mice when the tumor provided sufficient TAA.

Keywords: Spirulina; Tumor regression; CTL