Macrophages are involved in antitumor activity of SGN-30 in vivo. L540cy-bearing mice were depleted of NK cells (A) and macrophages (MΦ) (B) as described in “Xenograft models.” Mice were either left untreated (control) or treated with 10 mg/kg SGN-30 on day 1 after L540cy challenge (n = 10 per group). (A) Untreated vs. SGN-30 (P = .007), –NK vs SGN-30 –NK (P < .001), SGN-30 vs SGN-30 –NK (P = .245). (B) Untreated vs SGN-30 (P = .007), –MΦ vs SGN-30 –MΦ (P = .002), SGN-30 vs SGN-30 –MΦ (P < .001).