Fig. 4.

Reduced antiproliferative effects of cetuximab or gefitinib in combination with cisplatin in cells transfected with a constitutively active H-Ras. A431V and A431-Ras cells (5 × 10³) were seeded and allowed to adhere overnight in medium containing 10% FBS. (A) A431V (□) and A431-Ras (▲) cells were then pulsed with increasing doses of cisplatin (0–10 μM) for 3 h, washed in PBS and left for 5 days in medium containing 0.5% FBS. (B) Cells were left untreated (solid column) or were pulsed with 1 μM of cisplatin for 3 h, washed in PBS, and then treated with 1 nM of cetuximab (open column). (C) Cells were untreated (solid column) or were pulsed with 1 μM of cisplatin for 3 h, washed in PBS, and then treated with 0.1 μM of gefitinib (open column) in medium containing 0.5% FBS for 5 days. Cell proliferation was assessed by an MTT assay as described in Materials and Methods using the optical density (OD) of cell lysates as relative numbers of cells. The OD value in the treated groups was expressed as a percentage of the OD value of the control group. The bars indicate standard deviation.