In vivoandin vitroeffects of β‐carotene and algae extracts in murine tumor models

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Abstract
Phycotene, an algae extract with known antineoplastic activity, was demonstrated to prolong, but not sustain, an increased survival rate in a murine fibrosarcoma model when it was combined with immunotherapy. It was further shown that splenocytes from phycotene and β‐carotene‐treated survivors could not confer protection to a fresh tumor cell challenge in virgin mice after adoptive transfer. In a series of cytotoxicity assays, phycotene combined with immunization was demonstrated to enhance cell‐mediated and complement‐dependent cytotoxicity in the first 14–21 days. However, after 21 days, the phycotene and immunization groups exhibited a decreased ability to mediate immune cytotoxicity compared with immunization‐only controls. This may serve to explain the in vivo findings that while survival was increased early on in active immunization and phycotene‐treated mice, it eventually dropped to the level of the active immunization controls.