Data from Antitumor Impact of <i>p14<sup>ARF</sup></i> on Gefitinib-Resistant Non–Small Cell Lung Cancers

Activation of the epidermal growth factor receptor (EGFR) has been observed in many malignant tumors and its constitutive signal transduction facilitates the proliferation of tumors. EGFR-tyrosine kinase inhibitors, such as gefitinib, are widely used as a molecular-targeting agent for the inactivation of EGFR signaling and show considerable therapeutic effect in non–small cell lung cancers harboring activating EGFR mutations. However, prolonged treatment inevitably produces tumors with additional gefitinib-resistant mutations in EGFR, which is a critical issue for current therapeutics. We aimed to characterize the distinct molecular response to gefitinib between the drug-resistant and drug-sensitive lung adenocarcinoma cells in order to learn about therapeutics based on the molecular information. From the quantitative PCR analysis, we found a specific increase in p14^ARF expression in gefitinib-sensitive lung adenocarcinoma clones, which was absent in gefitinib-resistant clones. Moreover, mitochondria-targeted p14^ARF triggered the most augmented apoptosis in both clones. We identified the amino acid residues spanning from 38 to 65 as a functional core of mitochondrial p14^ARF (p14 38-65 a.a.), which reduced the mitochondrial membrane potential and caused caspase-9 activation. The synthesized peptide covering the p14 38-65 a.a. induced growth suppression of the gefitinib-resistant clones without affecting nonneoplastic cells. Notably, transduction of the minimized dose of the p14 38-65 peptide restored the response to gefitinib like that in the sensitive clones. These findings suggest that the region of p14^ARF 38-65 a.a. is critical in the pharmacologic action of gefitinib against EGFR-mutated lung adenocarcinoma cells and has potential utility in the therapeutics of gefitinib-resistant cancers. Mol Cancer Ther; 12(8); 1616–28. ©2013 AACR.