Effects of the systemic treatment of F9 tumor-bearing mice with L19mTNFα (A) Results of the quantitative analysis of F9 tumor cell viability at different times after intravenous injection of 1.0 pmol/g of mouse of L19mTNFα and TN11mTNFα, respectively. The resulting values are the average (± SE) of the percentage of tumor cell viability. (B) TUNEL analysis in the vital part of F9 tumors. (i) Twenty-four hours after treatment with L19mTNFα, numerous apoptotic endothelial cells are visible; (ii) no endothelial cell labeling of tumor vessels is found in the tumor of untreated mice in which only few apoptotic tumor cells are detected. Bars = 50 μm. (C) F9 tumor growth curves (mean ± SD) in mice treated with a single injection of PBS and 1.0 pmol/g TN11mTNFα, rmTNFα, and L19mTNFα, respectively. The number of days after subcutaneous inoculum of F9 cells is reported in the abscissa. An arrow indicates the day of the treatment. (D) Dose-dependent effect on tumor doubling time of a single intravenous injection with 0.25, 0.5, and 1.0 pmol/g L19mTNFα, TN11mTNFα, and rmTNFα. The doubling time results are expressed in hours (± SD).