RESUMO
<p><b>OBJECTIVE</b>To observe the impact of concurrent administration of recombinant human p53 adenovirus (Ad-p53) with EGFR inhibitor gefitinib on breast cancer MDA-MB-468 cells.</p><p><b>METHODS</b>MDA-MB-468 cells were treated with Ad-p53 and/or gefitinib. The effect of Ad-p53 and gefitinib on the growth of MDA-MB-468 cells was evaluated by MTT assay. Cell apoptosis was detected by flow cytometry. Western blot analysis was used to detect the alteration of p53,EGFR, phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway and apoptosis-related proteins. Ad-p53 combined with gefitinib was used in vivo to explore their effect on tumor xenograft in nude mice. Immunohistochemistry was used to detect the p53 expression in vivo.</p><p><b>RESULTS</b>The MTT assay showed a stronger inhibitory effect of gefitinib on MDA-MB-468 cells infected with Ad-p53 than on the control cells. Cell apoptosis assay revealed that the apoptosis rates of MDA-MB-468 cells in vehicle-treated group, Ad-p53 group, gefitinib group, and combination group were 8.5%, 17.4%, 20.5% and 32.6%, respectively. The apoptosis rate of MDA-MB-468 cells in the combination group was higher than that in other groups (P < 0.05, for all) . Western blot analysis revealed that the expression of p53 was significantly up-regulated in the presence of Ad-p53. The combination of Ad-p53 and gefitinib significantly down-regulated p-Akt (S473)(P < 0.01) and up-regulated caspase-9 and cleaved caspase-3 (P < 0.01 for both). Tumor inhibition rates (TIR) in the Ad-p53, gefitinib, and combination groups were 35.7%, 28.7% and 74.4%, respectively. Ad-p53 and gefitinib combination therapy significantly reduced the tumor burden in nude mice (P < 0.05 for all).Immunohistochemistry showed that after intratumoral administration of Ad-p53, wild-type p53 was increased (P < 0.01). p53 expressions in the vehicle-treated, Ad-p53, gefitinib and combination groups were 45.2%, 80.1%, 50.7% and 90.6%, respectively.</p><p><b>CONCLUSIONS</b>Wild-type p53 may reverse the sensitivity of MDA-MB-468 cells to gefitinib through down-regulation of the PI3K/Akt pathway. The apoptotic activity induced by this combination treatment might be regulated through caspase cascade.</p>