Microscopic morphology of progressive and regressing subcutaneous K562 tumors. Balb/c nu/nu mice were injected subcutaneously with K562 cells and were subsequently injected with saline (A through C), monocyte-derived IL-8 (D through F), endothelial IL-8 (G through I), and TNF- (J through L). Tumors were removed in toto, and hematoxylin and eosin staining (A, B, D, E, G, H, J, and K) or TUNEL assay (C, F, I, and L) was performed after 8 days. Original magnification × 5 for (A), (D), (G), and (J); × 20 for (B), (C), (E), (F), (H), (I), and (K).