Figure 4.
Anti-tumor effect of single-agent lefitolimod in syngeneic B16 and EMT-6 tumor models. (a-d), peritumoral sc injection in B16 model: 5 × 105 B16 tumor cells were inoculated sc into the flank of the mice (day 0). Seven to eight mice each were assigned per group via body weight stratification. 200 µg lefitolimod was injected sc (9x, starting day 3) with vehicle as control. The tumor size at day 7 was 37 mm3 (lefitolimod) and 32 mm3 (vehicle), respectively. Mean tumor growth (±SEM), p = .02 for days 11/14, p = .006 at days 18/20 (multiple t-tests), analyzed until day 20 (a), survival, p = .0001 (log-rank) (b), individual tumor volumes of vehicle (c, black) and lefitolimod group (d, blue) are shown. (e-h), anti-tumor effect and induction of long-lasting immunity in the EMT-6 model after itu treatment: Balb/c mice were inoculated sc with 5 × 105 EMT-6 tumor cells. Established tumors (app. 40 mm3, 3 days after tumor inoculation) were injected with 250 µg lefitolimod (9x, starting day 3). Mean tumor growth (±SEM), p = .04 at day 13, p ≤ 0.0001 at days 17/20/24 (Sidak`s multiple comparison test) (e) and survival, p ≤ 0.0001 (log-rank) (f) are shown. Tumor growth inhibition by lefitolimod was 86% (day 17–24). (g), surviving mice from (f) were inoculated with 5 × 105 EMT-6 tumor cells at day 54 (1st re-challenge) and subsequently with 5 × 105 CT26 cells at day 115 (2nd re-challenge) without further treatment. Age-matched naïve mice were used as controls. Individual tumor volumes are shown. (h), detection of systemic anti-tumor immunity in mice surviving the two re-challenges (EMT-6 and CT26 cells). Spleens were collected and splenocytes were re-stimulated with mitomycin-treated EMT-6, CT26, Renca, A20, 4T1 or WEHI164 cells for 24 h. IFN-gamma ELISpot was performed. Spleen cells of age-matched naïve mice were used as controls. Shown are numbers of spots per 8 × 105 splenocytes corrected by subtraction of numbers of spots obtained for the respective “splenocyte only” control.