Abstract

Mutations of the epidermal growth factor receptor (EGFR) selectively activate Akt and signal transducer and activator of transcription (STAT) pathways that are important in lung cancer cell survival. Src family kinases can cooperate with receptor tyrosine kinases to signal through downstream molecules, such as phosphatidylinositol 3-kinase/PTEN/Akt and STATs. Based on the importance of EGFR signaling in lung cancer, the known cooperation between EGFR and Src proteins, and evidence of elevated Src activity in human lung cancers, we evaluated the effectiveness of a novel orally bioavailable Src inhibitor dasatinib (BMS-324825) in lung cancer cell lines with defined EGFR status. Here, we show that cell fate (death versus growth arrest) in lung cancer cells exposed to dasatinib is dependent on EGFR status. In cells with EGFR mutation that are dependent on EGFR for survival, dasatinib reduces cell viability through the induction of apoptosis while having minimal apoptotic effect on cell lines with wild-type (WT) EGFR. The induction of apoptosis in these EGFR-mutant cell lines corresponds to down-regulation of activated Akt and STAT3 survival proteins. In cell lines with WT or resistant EGFR mutation that are not sensitive to EGFR inhibition, dasatinib induces a G(1) cell cycle arrest with associated changes in cyclin D and p27 proteins, inhibits activated FAK, and prevents tumor cell invasion. Our results show that dasatinib could be effective therapy for patients with lung cancers through disruption of cell growth, survival, and tumor invasion. Our results suggest EGFR status is important in deciding cell fate in response to dasatinib.

Highlights

  • Activating mutations in the tyrosine kinase domain of the epidermal growth factor (EGF) receptor (EGFR) selectively activate Akt and signal transducer and activator of transcription (STAT) pathways important in lung cancer cell survival and can predict sensitivity to small-molecule inhibitors of epidermal growth factor receptor (EGFR), such as gefitinib and erlotinib [1,2,3,4]

  • We found that cell lines with mutant EGFR (H3255, H1650, PC9, HCC827, and H1975) have enhanced levels of pEGFR and pTyr705 STAT3 (pSTAT3) compared with WT EGFR cells (H460, H358, H1299, and A549), with PC9 being the exception because it has undetectable pSTAT3 expression (Fig. 1B)

  • Dasatinib resulted in apoptosis in cells with EGFR mutants sensitive to gefitinib (H3255, H1650, HCC827, and PC9), whereas minimal apoptosis was observed in WT EGFR cells (A549 and H358) or in gefitinibresistant H1975 cells (Fig. 1C)

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Summary

Introduction

Activating mutations in the tyrosine kinase domain of the epidermal growth factor (EGF) receptor (EGFR) selectively activate Akt and signal transducer and activator of transcription (STAT) pathways important in lung cancer cell survival and can predict sensitivity to small-molecule inhibitors of EGFR, such as gefitinib and erlotinib [1,2,3,4]. Src family kinases can cooperate with receptor tyrosine kinases to signal through downstream molecules, such as phosphatidylinositol 3-kinase (PI3K)/PTEN/Akt and STATs [6, 7, 9]. For these reasons, we surmised that that cell lines harboring activating EGFR mutations may show increased sensitivity to Src inhibitors. In addition to Src proteins, dasatinib can potentially interact with other important tyrosine kinase proteins involved in tumor cell growth and survival and these interactions could enhance its antitumor activity [11]

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