In vivo and in vitro effects of beta-carotene and algae extracts in murine tumor models

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 beta-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.