Chemoradiotherapy is considered to be the standard treatment for locally advanced NSCLC, but its therapeutic success is limited. ZD6474 targets two key pathways in tumor growth by selectively inhibiting VEGFR and EGFR tyrosine kinase activity. We evaluated the feasibility of combining ZD6474 with radiation therapy (RT), and compared this with chemoradiation, in an orthotopic model of human NSCLC. The left lungs of nude mice (n = 8 per group; experiment repeated twice) were injected with human lung adenocarcinoma cells (NCI-H441) and after 8 days of tumor growth, mice were randomized to one of six treatment regimens: low-dose ZD6474 (15 mg/kg daily p.o.); RT (4 Gy fractions 3 times/week to 20 Gy); paclitaxel (Pac; 200 μg weekly i.p.); ZD6474 + RT; Pac + RT; or vehicle. The experiment was terminated when the control group began to show signs of morbidity. Tumor burden was assessed by lung and tumor weight, and pleural effusion volume. Tumor and adjacent tissues were analyzed by immunohistochemical staining for CD-31, VEGF, VEGFR-2, EGF, EGFR, MMP2, MMP9 and βFGF. Lung and tumor weight (mg) of mice treated with vehicle, RT, Pac, Pac + RT, ZD6474, or ZD6474 + RT was 840 ± 220, 437 ± 49.6, 518 ± 100, 356 ± 37.3, 371 ± 59.7 and 271 ± 12.4 (P=0.032 vs Pac + RT), respectively. Pleural effusion (μl) in mice treated with vehicle, RT, Pac + RT or ZD6474 + RT was 745 ± 112, 565 ± 99.4, 246 ± 69.4 and 14.2 ± 4.8, respectively. Compared with vehicle, combined therapy with ZD6474 + RT enhanced tumor (12 ± 4.1 vs 1.3 ± 0.2%) and endothelial cell (9.4 ± 2.3 vs 0.3 ± 0.3%) apoptosis, and suppressed tumor (8.8 ± 1.2 vs 33 ± 3.8%) and endothelial cell (5.4 ± 3.0 vs 27 ± 3.5%) proliferation. Microvessel density of lung primary tumors in vehicle, RT, Pac + RT, and ZD6474 + RT treated groups was 55 ± 3.3, 52 ± 7.3, 31 ± 3.5 and 16 ± 1.9, respectively. Expression of VEGF and EGF significantly decreased after ZD6474 treatment (P<0.0001 and <0.001 vs vehicle, respectively). Expression of VEGFR-2 significantly increased after RT (P<0.0001 vs vehicle), but this was offset by combined treatment with ZD6474. Expression of EGFR increased after RT or Pac treatment, but not after ZD6474 treatment. A marked increase in expression of βFGF was observed after RT or Pac, but the RT-induced increase was offset by administration of ZD6474. Expression of MMP2 and MMP9 was induced by Pac, but not RT, and the Pac-induced increase was reduced by ZD6474. Targeted inhibition of VEGFR and EGFR with low-dose ZD6474 significantly enhances the antiangiogenic, antivascular and antitumor effects of RT for human lung cancer growing orthotopically in mice. Furthermore, low-dose ZD6474 + RT showed greater antitumor and antivascular effects than Pac + RT. These data strongly suggest that it will be prudent to include certain targeted agents in the multimodality management of lung cancer.
[Proc Amer Assoc Cancer Res, Volume 46, 2005]