Table 4

Immunohistochemical analysis of GEO colon cancer xenografts after treatment with ZD1839 and paclitaxel

Mice bearing GEO tumor xenografts were treated as described in “Materials and Methods.” Briefly, 107 cells were injected, after being suspended in 200 μl Matrigel, into the dorsal flank of 4–5-week-old nude mice on day 0. Treatment was started on day 7 after tumor cell injection, when tumor volume was ∼0.25 cm3. Mice were treated i.p. daily from day 1 to day 5 with the indicated doses of ZD1839 for 3 weeks or with the indicated dose of paclitaxel on day 1 of each week for 3 weeks. Mice were sacrificed, and histological and immunohistochemical analyses were performed on day 28 after tumor cell injection. The data presented are pooled data from two experiments in which each group consisted of eight mice. No histological evidence of GEO tumor was detected in 6 of 16 mice treated with the combination of paclitaxel and ZD1839. The percentage (± SD) of specifically stained GEO cancer cells for Ki67, TGF-α, bFGF, and VEGF was recorded. To determine the percentage of positive cells, at least 1000 cancer cells/slide were counted and scored. The number of microvessels for field (± SD) was measured using a monoclonal antibody raised against the human factor VIII-related antigen and was scored by averaging five field counts of three individual tumors for each group.
TreatmentTumor volume (cm3 ± SD)Micetumor-free% positive cellsFactor VIII-related antigena
Ki67TGF-αbFGFVEGF
Control1.45 ± 0.20/1670 ± 565 ± 555 ± 755 ± 521 ± 2
Paclitaxel 400 μg0.56 ± 0.10/1640 ± 1050 ± 535 ± 640 ± 515 ± 3
ZD1839 3.75 mg0.35 ± 0.050/1640 ± 520 ± 47 ± 35 ± 15 ± 2
Paclitaxel 400 μg + ZD1839 3.75 mg0.06 ± 0.016/1620 ± 52 ± 21 ± 11 ± 11 ± 1
  • a Values for factor VIII-related antigen are number of positively staining microvessels.