Immunohistochemistry Evaluation of the Effect in Vivo of Tumor Necrosis Factor (TNF)-α on Blood Vessel Density in Murine Fibrosarcoma

PURPOSE Angiogenesis is essential for tumor growth and metastases, thus bestowing obvious importance upon methodologies which could enable its inhibition. MATERIALS C57BL/6 female mice bearing a subcutaneous (s.c.) MCA205 fibrosarcoma were used. METHODS Ten mice were divided equally into two groups. One group was injected intraperitoneally (i.p.) with 10 mug tumor necrosis factor-alpha (TNF-alpha and the other (controls) with Hanks balanced salt solution (HBSS). Tumor growth was monitored at least twice weekly. The number of endothelial cells in the blood microvessels was assessed by immunohistostaining on paraffin-embedded tumor tissue sections using vascular endothelial growth factor (VEGF) and Factor 8 antibodies. Expression of the p53 gene was similarly assessed by immunohistostaining. RESULTS Injection of 10 mug TNF-alpha into the tumor-bearing mice reduced the number of endothelial cells in the blood microvessels by 46% on day 3 post-injection which was accompanied by an increase (by 37%) in the expression of p53 in these cells. It also inhibited tumor growth compared to the HBSS-injected group starting at 17 days post-cytokine injection. DISCUSSION The antitumor in vivo effect exerted by TNF-alpha on established murine sarcoma s.c. tumors may be due to an earlier effect of the cytokine on the tumor's blood microvessels, probably through an apoptotic mechanism involving the p53 gene.