Immunotherapy of Madison 109 lung carcinoma and other murine tumors using lentinan

Lentinan was evaluated initially against the Lewis (LL) and Madison 109 (M109) lung carcinomas implanted in the footpads of syngeneic mice. Activity in these tumor models was assessed by both reduction in early tumor growth rates and increases in life span and cures, relative to untreated control mice with tumors. Lentinan given i.p. to mice bearing LL footpad tumors caused a reduction in tumor growth rate in only one of three experiments and an increase in life span of 48% at one dose level on another occasion. In contrast, lentinan given i.p. to mice bearing M109 footpad tumors was consistently curative (50 to 70%) in three experiments despite the lack of an effect upon early tumor growth rate. In subsequent experiments, syngeneic mice were implanted s.c. with M109 or LL and treated with lentinan. Although lentinan had no substantial effect upon LL, 25 to 75% of mice bearing s.c. M109 tumors were cured in three separate experiments following early treatment initiation. Delayed lentinan therapy, initiated when s.c. M109 tumors were greater than 100 mg, also resulted in complete tumor regression and cure of 29 to 63% of the mice in three experiments. Surgical adjuvant immunotherapy of s.c. M109 using lentinan also improved survival rates over those obtained using surgery alone. Mice cured of s.c.-implanted M109 using lentinan, or surgery plus lentinan, but not surgery alone, survived a rechallenge with M109. The therapeutic effects of lentinan in mice implanted s.c. with B16 melanoma were inconsistent.