In vivo effect of IL-6 on MCL growth and survival. (A) Tumor burdens in SCID mice (5 per group) injected with parental-, gp80-overexpressing SP53 cells (S80)–, and empty vector-transfected SP53 (Svec) cells on week 4 after tumor inoculation. (B) ELISA showing the levels of secreted human gp80 in the sera of Svec or S80 SP53-inoculated SCID mice and in culture media of dissected cells from the subcutaneous tumor mass. Mouse serum was collected when tumor mass reached 15 mm in diameter. (C) IHC staining showing the expression of gp80 (top) or phosphorylated (p) STAT3 (bottom) by S80 and Svec tumors in mice. Phosphorylated STAT3 was intensively stained in the nuclei of the tumor cells. (D) Tumor burdens and (E) survival of parental-, Svec-, and S80-bearing SCID mice (10 per group) after BTZ treatment.