Figure 4
Complement-dependent antitumor activity of cetuximab in A549 xenografts. A, MTT assay for the in vitro antitumor activity of cetuximab in A549 and HCC827 lung cancer cell lines (with wild-type and mutant-EGFR, respectively). Cell proliferation was determined after 24 h treatment using an MTT assay. The graph shows mean ± SEM. B, A549 cells were injected s.c. on athymic nude mice. When tumors reached 200-250 mm3, mice (n = 10) were randomized into two groups: one was treated with cetuximab and the other with PBS. Cetuximab was administered i.p. at 0.5 mg per mouse three times a week and tumor growth was measured every 2-3 days. Data represent mean ± SEM (*, P < 0.05). C, Representative example of the deposition of C3-related fragments, determined by immunofluorescence, in explanted tumors from each experimental group. D, A549 xenografts were generated as above. Animals (n = 18) were divided into three groups. In one group, complement was depleted with CVF. Cetuximab treatment was administrated to the CVF-treated group and to a second group with full complement activity. The last group received PBS. Data represent mean ± SEM (*, P < 0.05).