The antitumor and
metastasis-inhibitory activities, mode of action, and clinical application of
lentinan, a strictly purified beta-1,6:beta-1,3-
glucan, are reviewed.
Lentinan exerts a prominent antitumor effect and prevents chemical and viral
oncogenesis. The antitumor action of
lentinan is host-mediated. Compared to other well-known
immunostimulants, such as bacille Calmette Guérin (BCG), Corynebacterium parvum, and
lipopolysaccharide (LPS),
lentinan appears to represent a unique class of
immunopotentiator, a T cell-oriented adjuvant.
Lentinan triggers the increased production of various kinds of bioactive serum factors associated with immunity and
inflammation, such as
IL-1, CSF,
IL-3, vascular dilation inducer, and
acute-phase protein inducer, by the direct impact of macrophages or indirectly via
lentinan-stimulated T cells, which results in the induction of many immunobiological changes in the host. Augmented
IL-1 production amplifies the maturation of immature effector cells to mature cells capable of responding to
lymphokines such as
IL-2 and T cell-replacing factors. Because of this mode of action, intact T cell compartments for antitumor activity of
lentinan are required.
Lentinan has little toxic side effects. Excellent results were obtained in a 4 year follow-up of the randomized control study of
lentinan in phase III on patients with advanced and recurrent stomach and
colorectal cancer.