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As the most common gene mutation found in cancers, p53 mutations are detected in up to 96% of high-grade serous ovarian carcinoma (HGSOC). Meanwhile, mutant p53 overexpression is known to drive oncogenic phenotypes in cancer patients and to sustain the activation of EGFR signaling. Previously, we have demonstrated that the combined inhibition of EGFR and MDM2-p53 pathways, by gefitinib and JNJ-26854165, exerts a strong synergistic lethal effect on HGSOC cells. In this study, we investigated whether the gain-of-function p53 mutation (p53R248Q) overexpression could affect EGFR-related signaling and the corresponding drug inhibition outcome in HGSOC. The targeted inhibition responses of gefitinib and JNJ-26854165, in p53R248Q-overexpressing cells, were extensively evaluated. We found that the phosphorylation of AKT increased when p53R248Q was transiently overexpressed. Immunocytochemistry analysis further showed that upon p53R248Q overexpression, several AKT-related regulatory proteins translocated in unique intracellular patterns. Subsequent analysis revealed that, under the combined inhibition of gefitinib and JNJ-26854165, the cytonuclear trafficking of EGFR and MDM2 was disrupted. Next, we analyzed the gefitinib and JNJ-26854165 responses and found differential sensitivity to the single- or combined-drug inhibitions in p53R248Q-overexpressing cells. Our findings suggested that the R248Q mutation of p53 in HGSOC caused significant changes in signaling protein function and trafficking, under EGFR/MDM2-targeted inhibition. Such knowledge could help to advance our understanding of the role of mutant p53 in ovarian carcinoma and to improve the prognosis of patients receiving EGFR/MDM2-targeted therapies. [ABSTRACT FROM AUTHOR]