. . _:b592473675 "4"^^ . _:b592473764 . . _:b592473674 "4"^^ . . _:b592473767 . . _:b592473685 "3"^^ . _:b45990699 "IGF1R tyrosine kinase inhibitors have been reported to reverse the drug resistance of NSCLC to EGFR-TKIs in vitro and in vivo [>>7<<]. IGF1R activates the downstream pathways of EGFR signaling, such as the phosphatidylinositol 3 kinase/protein kinase B (PI3K/AKT) pathway and the extracellular signal-regulated kinases/mitogen-activated protein kinase (ERK/MAPK) pathway," . . . _:b592473766 . _:b45990718 "Treatment with TGF-\u03B21 has also been shown in many cancer cells to promote a shift from epithelial to mesenchymal phenotype [25, >>26<<]. To further evaluate whether EMT constituted a major mechanism underlying acquired drug resistance, parental PC-9 and H460 cells were treated with exogenous TGF-\u03B21 (10 ng/mL) for 72 h." . _:b592473684 "3"^^ . _:b45990692 . _:b592473780 . _:b592473670 . _:b592473761 . _:b592473687 "3"^^ . _:b592473760 . _:b592473749 . _:b592473686 "3"^^ . _:b592473763 . _:b592473681 "3"^^ . . _:b592473757 . _:b592473806 . _:b592473762 . _:b592473680 "3"^^ . _:b592473773 . _:b592473683 "3"^^ . _:b592473772 . . _:b592473682 "3"^^ . _:b592473695 . . . _:b592473775 . _:b592473693 "3"^^ . _:b45990719 "discussion" . . _:b45990710 . _:b592473774 . _:b592473651 . _:b592473692 "3"^^ . . _:b592473769 . _:b592473695 "3"^^ . _:b45990705 . . _:b592473768 . _:b592473694 "3"^^ . . _:b592473771 . _:b592473798 . _:b592473660 . _:b45990711 . _:b592473689 "3"^^ . . . _:b592473770 . _:b592473688 "3"^^ . . _:b592473781 . _:b592473836 . _:b592473691 "3"^^ . . . . _:b592473780 . . _:b592473690 "3"^^ . _:b45990708 . . _:b592473783 . _:b592473701 "3"^^ . . _:b592473782 . _:b45990711 . _:b592473700 "3"^^ . _:b45990733 "Previous studies have shown that IGF-1/IGF1R activation can promote EMT in prostate cancer cells [15] and human mammary epithelial cells [>>32<<]. Nurwidya et al. [33] found that inhibition of IGF1R reversed hypoxia-induced EMT." . _:b592473700 . _:b592473777 . _:b592473869 . _:b592473703 "3"^^ . _:b592473793 . _:b592473776 . _:b592473702 "3"^^ . _:b592473779 . _:b592473697 "3"^^ . _:b592473778 . _:b592473855 . _:b592473696 "3"^^ . _:b592473789 . _:b592473850 . _:b592473699 "3"^^ . . _:b592473788 . _:b592473698 "3"^^ . _:b45990703 "Interestingly, IGF1R has been shown to play an important role in EMT [7] and IGF1R activation can induce EMT in breast epithelial cells [14] and prostate cancer cells [>>15<<]. EMT is a biological process of losing epithelial features and acquiring mesenchymal properties, characterized by E-cadherin reduction and Vimentin induction." . _:b45990737 . . _:b592473791 . _:b592473709 "3"^^ . . _:b592473790 . . _:b592473708 "3"^^ . _:b592473727 . _:b592473785 . . _:b592473711 "3"^^ . _:b592473677 . _:b592473702 . . _:b592473784 . . _:b592473710 "3"^^ . _:b592473734 . _:b592473787 . _:b592473705 "3"^^ . . _:b592473786 . . _:b592473704 "3"^^ . . _:b592473797 . . _:b592473707 "3"^^ . _:b45990712 . _:b592473796 . _:b592473706 "3"^^ . _:b592473799 . _:b592473717 "2"^^ . _:b592473733 . _:b592473839 . . _:b592473798 . _:b592473716 "2"^^ . _:b592473692 . . _:b592473793 . . . _:b592473719 "2"^^ . . . _:b592473792 . _:b592473718 "2"^^ . . _:b592473795 . . _:b592473713 "3"^^ . . _:b592473794 . _:b592473826 . _:b592473794 . . _:b592473870 . _:b592473712 "3"^^ . _:b592473805 . _:b45990723 "Guix et al. [>>29<<] also discovered that IGF-1 activated IGF1R in lung cancer cells, and showed that only cells, which depended on IGF1R and its downstream signaling pathways to promote cell growth, acquired the resistance ability against geftinib." . _:b592473859 . _:b592473715 "3"^^ . _:b592473804 . _:b45990722 "Vazquez-Martin et al. [27] and Cortot et al. [>>28<<] also suggested a role of IGF1R in acquired drug resistance to EGFR-TKIs in PC-9 cells." . _:b592473714 "3"^^ . _:b592473807 . _:b592473725 "2"^^ . _:b45990729 "It is well established that EMT is involved in acquired drug resistance to EGFR-TKIs in NSCLC cells carrying wild-type EGFR, for instance, in A549 [8, 30] and in H1229 cells [>>30<<]. However, there is still paucity of evidence to support a role of EMT in acquired drug resistance to EGFR-TKIs in NSCLC cells with EGFR mutations." . . _:b592473806 . _:b592473724 "2"^^ . . _:b592473822 . _:b592473721 . . _:b592473801 . _:b592473727 "2"^^ . _:b592473698 . _:b592473784 . _:b592473800 . _:b592473726 "2"^^ . _:b592473787 . _:b592473705 . _:b592473740 . _:b592473857 . _:b592473803 . _:b592473721 "2"^^ . _:b592473834 . _:b592473802 . _:b592473720 "2"^^ . _:b592473819 . . . _:b592473813 . _:b592473723 "2"^^ . . _:b592473812 . _:b592473722 "2"^^ . _:b45990709 "Furthermore, decreased expression of E-cadherin [8, 16, >>17<<] was associated with reduced sensitivity to EGFR-TKIs, and restoration of E-cadherin expression improved cells' sensitivity to EGFR-TKIs [18]." . . _:b592473815 . _:b592473738 . . _:b592473733 "2"^^ . _:b592473672 . _:b592473814 . _:b592473732 "2"^^ . . _:b592473809 . _:b592473735 "2"^^ . . _:b592473808 . . _:b592473734 "2"^^ . . _:b592473811 . _:b592473729 "2"^^ . _:b592473711 . _:b592473810 . _:b592473728 "2"^^ . _:b592473697 . _:b592473756 . _:b592473821 . _:b592473829 . _:b592473731 "2"^^ . _:b592473729 . _:b592473820 . _:b592473730 "2"^^ . . _:b592473823 . _:b592473741 "2"^^ . _:b592473822 . _:b592473848 . _:b592473740 "2"^^ . . _:b592473789 . _:b592473849 . _:b592473850 . _:b592473851 . _:b592473817 . _:b592473852 . _:b592473743 "2"^^ . _:b592473853 . . . _:b592473854 . _:b592473786 . _:b592473768 . _:b592473855 . _:b592473816 . _:b592473840 . _:b592473742 "2"^^ . _:b592473841 . . . _:b592473842 . _:b592473843 . _:b592473819 . _:b592473844 . _:b592473737 "2"^^ . _:b592473845 . _:b592473846 . _:b592473847 . _:b592473818 . . . _:b592473736 "2"^^ . _:b592473832 . . _:b592473833 . _:b592473834 . _:b592473835 . _:b592473829 . _:b592473836 . _:b592473739 "2"^^ . _:b592473837 . _:b592473838 . _:b45990697 "Previous studies showed that activation of IGF1R is involved in EGFR-TKIs resistance in NSCLC cell lines [>>9<<] and in lung cancer patients [10]." . _:b592473839 . _:b592473833 . _:b592473828 . _:b592473824 . _:b592473742 . _:b592473738 "2"^^ . . _:b592473825 . _:b592473826 . _:b592473827 . _:b592473831 . . _:b592473749 "2"^^ . _:b592473704 . _:b592473828 . . _:b592473829 . _:b45990700 . . _:b592473830 . _:b592473831 . _:b592473830 . _:b592473816 . _:b592473748 "2"^^ . _:b592473817 . _:b592473818 . _:b592473819 . _:b592473825 . _:b592473820 . _:b592473751 "2"^^ . _:b592473821 . _:b592473822 . _:b592473823 . _:b592473824 . _:b592473808 . _:b592473750 "2"^^ . _:b592473809 . _:b592473810 . _:b592473811 . _:b592473827 . _:b592473812 . _:b592473745 "2"^^ . . _:b592473813 . . _:b592473814 . _:b592473652 . _:b592473826 . _:b592473815 . _:b592473800 . _:b592473744 "2"^^ . _:b592473801 . _:b592473802 . _:b592473803 . _:b592473837 . _:b592473804 . _:b592473747 "2"^^ . _:b592473805 . _:b592473762 . _:b592473806 . _:b592473737 . . _:b592473836 . _:b592473707 . _:b592473807 . _:b592473792 . _:b592473746 "2"^^ . . _:b592473793 . _:b592473794 . _:b592473795 . _:b592473839 . _:b592473796 . _:b45990692 "Currently, the known mechanisms underlying this acquired drug resistance include T790M mutation [>>4<<, 5] and amplification of MET genes [6]." . _:b592473757 "2"^^ . _:b592473797 . _:b592473798 . _:b592473799 . _:b592473838 . _:b592473781 . _:b592473752 . . _:b592473756 "2"^^ . _:b592473784 . _:b592473785 . _:b592473786 . _:b592473787 . _:b592473833 . _:b592473788 . _:b592473872 . _:b592473759 "2"^^ . _:b592473666 . _:b592473789 . _:b592473790 . _:b592473818 . _:b592473767 . _:b592473791 . _:b592473832 . . _:b592473758 "2"^^ . _:b592473776 . _:b592473777 . _:b592473778 . _:b592473779 . _:b592473835 . _:b592473780 . _:b592473878 . _:b592473800 . _:b592473753 "2"^^ . _:b592473781 . . _:b592473782 . . _:b592473834 . _:b592473783 . _:b592473768 . _:b592473752 "2"^^ . _:b592473769 . _:b592473809 . . _:b592473770 . _:b592473771 . _:b592473845 . _:b592473772 . _:b592473755 "2"^^ . _:b592473773 . _:b592473774 . _:b592473877 . _:b592473775 . _:b592473844 . _:b592473760 . _:b45990738 . _:b592473754 "2"^^ . _:b592473761 . _:b45990715 "fluorescence in situ hybridization (FISH) was performed on unstained formalin-fixed lung cancer cell suspension, using a MET/CEP7 probe cocktail (Kreatech Diagnostics, Amsterdam, Netherlands) according to manufacturer's instructions [>>24<<]. A MET/CEP ratio was established on the basis of a count of at least 200 cells." . _:b592473762 . _:b592473763 . _:b45990695 "Recent studies show that the activation of epithelial-mesenchymal transition (EMT) and type 1 insulin-like growth factor receptor (IGF1R) is associated with acquired drug resistance against EGFR-TKIs in NSCLC [>>7<<, 8]." . _:b592473847 . _:b592473764 . _:b592473765 "2"^^ . _:b592473765 . _:b592473766 . _:b592473863 . _:b592473767 . _:b592473846 . _:b592473752 . _:b592473764 "2"^^ . _:b592473753 . _:b592473754 . _:b592473755 . _:b592473841 . _:b592473718 . . _:b592473767 "2"^^ . _:b592473719 . _:b592473756 . . _:b592473757 . _:b592473758 . _:b592473759 . _:b592473840 . . _:b592473766 "2"^^ . _:b592473747 . _:b592473744 . _:b592473745 . _:b592473746 . _:b592473747 . _:b592473843 . _:b592473748 . _:b592473761 "2"^^ . . _:b592473749 . _:b592473750 . _:b592473751 . _:b592473842 . _:b592473736 . _:b592473760 "2"^^ . _:b592473737 . _:b592473738 . _:b592473739 . _:b592473853 . _:b592473740 . _:b592473763 "2"^^ . _:b592473741 . _:b592473742 . _:b592473743 . _:b592473871 . _:b592473852 . _:b592473790 . _:b592473741 . _:b592473728 . _:b592473762 "2"^^ . _:b592473729 . _:b592473675 . _:b592473730 . _:b592473731 . _:b592473855 . _:b592473802 . _:b592473732 . _:b592473773 "2"^^ . _:b592473733 . _:b592473734 . _:b592473795 . _:b592473735 . _:b592473854 . _:b592473720 . _:b45990710 "Furthermore, decreased expression of E-cadherin [8, 16, 17] was associated with reduced sensitivity to EGFR-TKIs, and restoration of E-cadherin expression improved cells' sensitivity to EGFR-TKIs [>>18<<]. Consistently, clinical studies have suggested a prognostic value of E-cadherin in NSCLC patients treated with EGFR-TKIs [19\u201321]." . _:b592473856 . _:b592473772 "2"^^ . _:b592473721 . _:b592473722 . _:b592473723 . _:b592473849 . _:b592473724 . _:b592473775 "2"^^ . _:b592473725 . . _:b592473726 . _:b592473727 . _:b592473848 . _:b592473712 . _:b592473813 . _:b592473774 "2"^^ . _:b592473758 . . _:b592473713 . _:b592473714 . _:b592473715 . _:b592473851 . . _:b592473769 "2"^^ . _:b592473716 . . _:b592473717 . . . _:b592473735 . _:b592473718 . _:b592473656 . _:b45990703 . _:b592473850 . _:b592473719 . _:b592473704 . _:b592473768 "2"^^ . _:b592473705 . _:b592473706 . . _:b592473707 . _:b592473708 . _:b592473771 "2"^^ . _:b592473751 . _:b592473709 . _:b592473710 . _:b592473711 . _:b592473696 . _:b592473770 "2"^^ . _:b592473697 . . _:b592473698 . _:b592473699 . . _:b592473700 . _:b592473781 "2"^^ . _:b592473701 . . _:b592473702 . _:b592473703 . _:b592473688 . _:b592473780 "2"^^ . . _:b592473689 . . _:b592473690 . _:b592473691 . _:b592473692 . _:b592473783 "2"^^ . _:b592473693 . _:b592473694 . _:b592473695 . _:b592473853 . _:b592473680 . _:b592473782 "2"^^ . . _:b592473681 . . _:b592473682 . _:b592473807 . . _:b592473683 . . _:b592473684 . _:b45990705 "It has been reported that a subgroup of NSCLC with pronounced EMT was EGFR-TKIs resistant [3, 8, >>16<<, 17], suggesting that EMT may render NSCLC insensitive to EGFR inhibition." . _:b592473777 "2"^^ . _:b592473694 . _:b592473685 . _:b592473730 . _:b592473686 . . _:b592473689 . _:b592473680 . _:b592473687 . _:b592473672 . _:b592473776 "2"^^ . _:b592473673 . _:b592473713 . _:b592473674 . _:b45990726 . _:b592473675 . _:b592473722 . _:b592473708 . _:b592473676 . _:b592473824 . _:b592473779 "2"^^ . . _:b592473677 . _:b592473678 . _:b592473679 . _:b592473664 . _:b592473778 "2"^^ . _:b592473665 . _:b592473666 . _:b592473667 . _:b592473668 . _:b592473789 "2"^^ . _:b592473669 . _:b592473670 . _:b592473671 . _:b45990739 . _:b592473656 . _:b592473788 "2"^^ . . _:b592473657 . _:b592473862 . _:b592473654 . . _:b592473658 . _:b592473797 . _:b592473659 . _:b592473660 . _:b592473791 "2"^^ . _:b592473661 . . _:b592473662 . _:b592473663 . _:b592473790 "2"^^ . _:b592473651 . _:b592473652 . _:b592473810 . _:b592473785 "2"^^ . _:b592473653 . _:b592473654 . _:b592473655 . _:b592473784 "2"^^ . _:b592473787 "2"^^ . . . . _:b592473786 "2"^^ . . _:b592473797 "2"^^ . . _:b592473796 "2"^^ . _:b592473852 . . _:b592473799 "2"^^ . . _:b592473798 "2"^^ . _:b592473685 . . _:b592473793 "2"^^ . . . _:b592473792 "2"^^ . _:b592473684 . _:b592473795 "2"^^ . _:b592473794 "2"^^ . _:b592473805 "2"^^ . _:b592473754 . _:b592473679 . _:b592473805 . _:b592473804 "2"^^ . _:b592473791 . _:b45990732 . _:b592473807 "2"^^ . _:b592473671 . . . . _:b592473806 "2"^^ . _:b592473712 . . . _:b592473801 "2"^^ . . _:b592473720 . _:b592473800 "2"^^ . _:b45990714 "EGFR mutations were detected using quantitative PCR-high-resolution melting (qPCR-HRM) curve analysis technology [>>23<<]." . _:b592473803 "2"^^ . . . _:b592473802 "2"^^ . . _:b592473813 "2"^^ . . _:b592473783 . . _:b592473812 "2"^^ . _:b45990734 "Nurwidya et al. [>>33<<] found that inhibition of IGF1R reversed hypoxia-induced EMT." . _:b592473815 "2"^^ . _:b592473876 . . _:b592473814 "2"^^ . _:b592473803 . . _:b592473809 "2"^^ . _:b45990735 "Loss of E-cadherin is a critical step in EMT and corresponds with the morphological and cellular alterations [>>34<<, 35]. Factors that inhibit E-cadherin expression, such as nuclear transcription factor Snail, ZEB, Slug etc [36] are involved in EMT process. Internalization of the protein complex leads to the degradation of E-cadherin and the" . _:b592473845 . _:b592473750 . _:b592473777 . . _:b592473808 "2"^^ . . _:b592473811 "2"^^ . . . _:b45990711 . _:b45990692 . _:b592473810 "2"^^ . _:b45990691 . _:b592473667 . _:b45990693 . _:b592473682 . _:b592473821 "2"^^ . _:b592473725 . _:b45990694 . . _:b592473820 "2"^^ . . . _:b45990695 . _:b592473823 "2"^^ . . _:b592473822 "2"^^ . _:b45990717 . . _:b592473817 "2"^^ . _:b592473765 . _:b592473710 . . _:b45990690 . _:b592473816 "2"^^ . _:b45990691 . _:b592473819 "2"^^ . _:b45990712 "Previously, we reported the association between EMT, IGF1R expression and drug response in advanced NSCLC patients treated with gefitinib [>>22<<]. NSCLC patients with negative EMT or lower IGF1R expression have a significantly higher objective response rate." . _:b45990737 "Factors that inhibit E-cadherin expression, such as nuclear transcription factor Snail, ZEB, Slug etc [>>36<<] are involved in EMT process." . . _:b45990700 . . _:b592473818 "2"^^ . . _:b592473811 . _:b592473726 . . _:b45990701 . . _:b592473829 "2"^^ . _:b592473688 . _:b45990702 . . _:b592473828 "2"^^ . . _:b45990703 . . _:b592473831 "2"^^ . _:b592473760 . . . _:b45990696 . _:b592473830 "2"^^ . _:b592473669 . _:b45990697 . _:b592473825 "2"^^ . . _:b45990728 "It is well established that EMT is involved in acquired drug resistance to EGFR-TKIs in NSCLC cells carrying wild-type EGFR, for instance, in A549 [8, >>30<<] and in H1229 cells [30]. However, there is still paucity of evidence to support a role of EMT in acquired drug resistance to EGFR-TKIs in NSCLC cells with EGFR mutations." . _:b45990698 . _:b592473824 "2"^^ . _:b45990726 "Data in the present study, which were consistent with Peled et al's [>>9<<] report, showed that exogenous IGF-1 alone does not promote lung cancer cell proliferation, but instead increases cell survival against erlotinib." . _:b592473723 . _:b45990699 . _:b592473827 "2"^^ . _:b45990727 "It is well established that EMT is involved in acquired drug resistance to EGFR-TKIs in NSCLC cells carrying wild-type EGFR, for instance, in A549 [>>8<<, 30] and in H1229 cells [30]. However, there is still paucity of evidence to support a role of EMT in acquired drug resistance to EGFR-TKIs in NSCLC cells with EGFR mutations." . _:b592473867 . _:b45990708 . _:b592473826 "2"^^ . _:b45990709 . . _:b45990724 "One possible mechanism is that after EGFR pathway is inhibited, IGF1R pathway is activated to promote cell survival and proliferation [>>7<<]. Morgillo et al. [7] found that erlotinib treatment of H460 cells increase the levels of EGFR/IGFIR heterodimer on cell membrane, subsequently activate IGFIR and its downstream signaling mediators. Data in the present study, which were" . _:b592473837 "2"^^ . . _:b45990710 . _:b592473836 "2"^^ . _:b45990711 . _:b592473839 "2"^^ . _:b45990704 . _:b45990730 . _:b592473838 "2"^^ . _:b45990738 . _:b45990739 "Graham et al. [>>15<<] showed that IGF-1 up-regulates ZEB1 expression through the ERK/MAPK pathway in prostate cancer cells." . _:b592473858 . _:b45990705 . _:b592473833 "2"^^ . _:b45990706 . _:b592473832 "2"^^ . . _:b45990707 . _:b592473835 "2"^^ . . _:b45990694 . _:b592473778 . _:b45990716 . _:b592473834 "2"^^ . _:b592473755 . . _:b45990717 . _:b592473845 "2"^^ . . _:b45990732 "Previous studies have shown that IGF-1/IGF1R activation can promote EMT in prostate cancer cells [>>15<<] and human mammary epithelial cells [32]. Nurwidya et al. [33] found that inhibition of IGF1R reversed hypoxia-induced EMT." . _:b45990691 "Acquired drug resistance has become a bottleneck in the treatment of advanced non-small cell lung cancer (NSCLC) using epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs) [>>1<<\u20133]. Currently, the known mechanisms underlying this acquired drug resistance include T790M mutation [4, 5] and amplification of MET genes [6]." . . _:b45990718 . _:b592473844 "2"^^ . . _:b45990719 . _:b45990736 . _:b592473847 "2"^^ . _:b592473775 . _:b592473703 . _:b45990712 . _:b592473846 "2"^^ . . _:b592473875 . _:b45990713 . _:b592473841 "2"^^ . . _:b45990714 . _:b592473772 . _:b592473868 . _:b592473840 "2"^^ . _:b45990715 . _:b592473731 . _:b592473843 "2"^^ . . _:b592473832 . _:b45990724 . _:b592473842 "2"^^ . _:b592473693 . _:b45990725 . _:b592473854 . . _:b592473853 "2"^^ . _:b592473764 . _:b45990723 . _:b45990726 . _:b592473852 "2"^^ . _:b45990714 . _:b45990727 . _:b592473855 "2"^^ . _:b45990707 "Furthermore, decreased expression of E-cadherin [>>8<<, 16, 17] was associated with reduced sensitivity to EGFR-TKIs, and restoration of E-cadherin expression improved cells' sensitivity to EGFR-TKIs [18]." . _:b45990720 . _:b45990728 . _:b592473854 "2"^^ . _:b45990713 "materials and methods" . _:b592473812 . _:b592473842 . _:b45990721 . _:b45990729 . _:b592473849 "2"^^ . _:b592473861 . _:b45990700 "such as the phosphatidylinositol 3 kinase/protein kinase B (PI3K/AKT) pathway and the extracellular signal-regulated kinases/mitogen-activated protein kinase (ERK/MAPK) pathway, leading to secondary drug resistance to EGFR-TKIs [>>11<<\u201313]. However, the exact mechanisms of IGF1R-induced acquired EGFR-TKIs resistance remain to be elucidated." . _:b45990722 . _:b592473848 "2"^^ . _:b592473724 . _:b592473860 . _:b45990711 "Consistently, clinical studies have suggested a prognostic value of E-cadherin in NSCLC patients treated with EGFR-TKIs [>>19<<\u201321]." . _:b45990723 . _:b592473851 "2"^^ . _:b592473863 . _:b592473788 . _:b45990732 . _:b592473850 "2"^^ . _:b592473862 . _:b45990733 . _:b592473861 "2"^^ . _:b592473857 . _:b45990698 "Previous studies showed that activation of IGF1R is involved in EGFR-TKIs resistance in NSCLC cell lines [9] and in lung cancer patients [>>10<<]. IGF1R tyrosine kinase inhibitors have been reported to reverse the drug resistance of NSCLC to EGFR-TKIs in vitro and in vivo [7]. IGF1R activates the downstream pathways of EGFR signaling, such as the phosphatidylinositol 3" . _:b45990733 . _:b45990734 . _:b592473860 "2"^^ . _:b592473856 . _:b45990706 "It has been reported that a subgroup of NSCLC with pronounced EMT was EGFR-TKIs resistant [3, 8, 16, >>17<<], suggesting that EMT may render NSCLC insensitive to EGFR inhibition." . _:b45990735 . _:b592473863 "2"^^ . _:b592473859 . _:b592473830 . _:b45990728 . _:b592473872 . _:b592473862 "2"^^ . _:b592473873 . _:b592473858 . _:b592473874 . _:b592473674 . _:b45990729 . _:b592473875 . _:b592473876 . _:b592473857 "2"^^ . _:b592473877 . _:b592473869 . . _:b45990704 . . _:b592473878 . . _:b45990730 . _:b592473879 . . _:b592473864 . _:b592473856 "2"^^ . _:b592473653 . _:b592473865 . _:b592473868 . _:b592473866 . _:b592473865 . _:b592473773 . _:b592473867 . _:b45990731 . _:b592473868 . _:b592473859 "2"^^ . _:b592473652 . _:b592473869 . _:b592473871 . _:b592473870 . _:b592473871 . _:b45990691 . _:b592473856 . _:b592473858 "2"^^ . _:b592473655 . _:b592473857 . _:b45990701 . _:b592473870 . _:b592473858 . _:b45990707 . _:b592473859 . _:b592473841 . _:b592473774 . _:b592473860 . _:b592473869 "2"^^ . _:b592473654 . _:b592473861 . _:b592473865 . _:b592473862 . . _:b592473863 . _:b592473744 . _:b592473868 "2"^^ . _:b592473864 . _:b592473759 . . _:b592473871 "2"^^ . _:b592473867 . . _:b45990736 . _:b592473828 . _:b592473651 . _:b592473870 "2"^^ . . _:b592473860 . _:b592473866 . . _:b45990721 "Vazquez-Martin et al. [>>27<<] and Cortot et al. [28] also suggested a role of IGF1R in acquired drug resistance to EGFR-TKIs in PC-9 cells." . _:b45990737 . _:b592473865 "2"^^ . . _:b592473877 . _:b592473823 . _:b45990738 . _:b592473662 . _:b592473864 "2"^^ . _:b592473661 . _:b592473876 . _:b45990699 . . _:b45990739 . . _:b592473867 "2"^^ . _:b592473660 . . _:b592473879 . _:b592473663 . _:b592473866 "2"^^ . _:b592473820 . _:b592473878 . . _:b592473662 . _:b592473877 "2"^^ . . _:b592473873 . _:b592473701 . . . _:b592473657 . _:b592473876 "2"^^ . . _:b45990695 . _:b592473872 . _:b592473815 . . . _:b45990716 _:b45990717 . _:b45990716 _:b45990718 . _:b45990730 "By downregulating N-cadherin expression via siRNA, Zhang et al. [>>31<<] found that the loss of EMT can reduce the proliferation and invasion of erlotinib-resistant H1650ER cells harboring a mutation in exon 19 of the EGFR gene." . _:b592473656 . _:b592473879 "2"^^ . _:b592473875 . _:b592473659 . _:b592473878 "2"^^ . _:b592473874 . _:b592473785 . _:b592473658 . _:b592473873 "2"^^ . . _:b45990721 . _:b592473872 "2"^^ . _:b592473669 . _:b45990713 _:b45990714 . _:b45990713 _:b45990715 . _:b592473668 . _:b592473875 "2"^^ . _:b592473874 . _:b45990690 _:b45990700 . _:b592473874 "2"^^ . _:b592473671 . . . _:b45990690 _:b45990701 . . _:b45990690 _:b45990702 . _:b45990690 _:b45990703 . _:b45990690 _:b45990696 . _:b592473670 . . _:b45990690 _:b45990697 . _:b45990690 _:b45990698 . _:b592473825 . _:b45990690 _:b45990699 . _:b45990690 _:b45990692 . _:b592473665 . _:b45990719 _:b45990736 . _:b45990690 _:b45990693 . . _:b45990719 _:b45990737 . _:b45990690 _:b45990694 . _:b592473808 . _:b45990719 _:b45990738 . _:b45990719 _:b45990739 . _:b45990690 _:b45990695 . _:b592473664 . _:b45990736 "Loss of E-cadherin is a critical step in EMT and corresponds with the morphological and cellular alterations [34, >>35<<]. Factors that inhibit E-cadherin expression, such as nuclear transcription factor Snail, ZEB, Slug etc [36] are involved in EMT process. Internalization of the protein complex leads to the degradation of E-cadherin and the relocalization" . _:b45990690 _:b45990691 . _:b45990719 _:b45990728 . _:b45990731 . _:b592473667 . _:b45990719 _:b45990729 . . _:b45990719 _:b45990730 . _:b45990719 _:b45990731 . _:b45990690 _:b45990712 . _:b592473666 . _:b45990719 _:b45990732 . _:b45990719 _:b45990733 . _:b592473846 . _:b592473687 . _:b45990696 . _:b45990719 _:b45990734 . _:b45990719 _:b45990735 . _:b592473849 . _:b592473677 . _:b45990690 _:b45990708 . _:b45990719 _:b45990720 . _:b45990690 _:b45990709 . _:b45990719 _:b45990721 . . _:b592473739 . _:b45990719 _:b45990722 . _:b45990690 _:b45990710 . _:b45990719 _:b45990723 . _:b45990704 "It has been reported that a subgroup of NSCLC with pronounced EMT was EGFR-TKIs resistant [3, >>8<<, 16, 17], suggesting that EMT may render NSCLC insensitive to EGFR inhibition." . _:b45990690 _:b45990711 . _:b592473676 . . _:b45990719 _:b45990724 . _:b45990690 _:b45990704 . _:b45990690 _:b45990705 . _:b45990719 _:b45990725 . _:b45990719 _:b45990726 . _:b45990690 _:b45990706 . . . _:b45990690 _:b45990707 . _:b45990719 _:b45990727 . _:b592473679 . . _:b592473799 . _:b45990700 . _:b592473879 . _:b592473678 . _:b45990697 . _:b45990702 "Interestingly, IGF1R has been shown to play an important role in EMT [7] and IGF1R activation can induce EMT in breast epithelial cells [>>14<<] and prostate cancer cells [15]. EMT is a biological process of losing epithelial features and acquiring mesenchymal properties, characterized by E-cadherin reduction and Vimentin induction." . _:b592473753 . _:b592473673 . _:b45990690 "introduction" . . _:b45990735 . _:b592473672 . _:b592473675 . . _:b592473690 . _:b592473674 . _:b592473776 . _:b592473685 . . _:b592473684 . _:b592473687 . _:b592473801 . _:b592473840 . . . _:b592473686 . . . _:b592473681 . _:b592473680 . . _:b592473716 . _:b592473683 . _:b592473838 . _:b45990698 . _:b592473682 . . _:b592473693 . _:b592473831 . _:b45990702 . . . _:b592473692 . _:b592473763 . _:b45990717 "Treatment with TGF-\u03B21 has also been shown in many cancer cells to promote a shift from epithelial to mesenchymal phenotype [>>25<<, 26]. To further evaluate whether EMT constituted a major mechanism underlying acquired drug resistance, parental PC-9 and H460 cells were treated with exogenous TGF-\u03B21 (10 ng/mL) for 72 h." . _:b592473695 . _:b45990725 . . . _:b592473694 . _:b45990690 . _:b45990724 . _:b592473689 . . _:b592473688 . _:b45990713 . . _:b45990716 . _:b592473691 . . _:b45990719 . . _:b592473690 . _:b45990720 . . . _:b592473827 . _:b592473748 . _:b592473701 . . _:b592473837 . _:b592473700 . _:b592473703 . . . _:b592473702 . . _:b45990693 "Currently, the known mechanisms underlying this acquired drug resistance include T790M mutation [4, >>5<<] and amplification of MET genes [6]." . _:b592473697 . _:b592473736 . _:b592473696 . _:b45990722 . . _:b592473699 . _:b592473761 . _:b592473816 . _:b592473698 . . . . _:b592473782 . _:b592473709 . _:b592473817 . _:b592473655 . . _:b592473708 . . _:b45990731 "Vazquez-Martin et al. [>>27<<] showed that EMT also occurred after PC-9 cells acquired drug resistance to erlotinib." . _:b592473717 . _:b592473699 . _:b592473770 . . _:b592473711 . _:b592473710 . . . . _:b592473705 . _:b592473681 . . _:b592473704 . . _:b592473707 . . _:b592473706 . _:b45990694 "Currently, the known mechanisms underlying this acquired drug resistance include T790M mutation [4, 5] and amplification of MET genes [>>6<<]. These mechanisms account for about 60\u201370% of acquired drug resistance. However, the underlying mechanisms for approximately 30%-40% of cases are still unclear. Recent studies show that the activation of epithelial-mesenchymal transition" . _:b45990738 "Internalization of the protein complex leads to the degradation of E-cadherin and the relocalization of \u03B2-catenin into the nucleus also contributes to this process [>>37<<\u201339]. Data of the present study showed that the expression of Snail was significantly increased after cells acquired drug resistance, and was significantly decreased when IGF1R was silenced, indicating that Snail may be the major" . . _:b592473717 . _:b592473664 . . _:b45990725 "Morgillo et al. [>>7<<] found that erlotinib treatment of H460 cells increase the levels of EGFR/IGFIR heterodimer on cell membrane, subsequently activate IGFIR and its downstream signaling mediators." . _:b592473716 . _:b592473719 . _:b592473686 . . _:b592473718 . . . _:b592473676 . _:b592473713 . _:b592473712 . _:b592473683 . _:b592473715 . . _:b45990693 . . _:b45990718 . _:b592473714 . _:b45990701 "Interestingly, IGF1R has been shown to play an important role in EMT [>>7<<] and IGF1R activation can induce EMT in breast epithelial cells [14] and prostate cancer cells [15]." . _:b592473696 . _:b592473814 . _:b592473804 . _:b592473725 . . _:b592473724 . . . . _:b592473678 . _:b592473727 . _:b592473851 . . _:b592473726 . . _:b592473866 . _:b592473721 . . _:b592473653 . _:b592473720 . _:b592473658 . _:b592473835 . . _:b592473723 . . _:b45990696 "Recent studies show that the activation of epithelial-mesenchymal transition (EMT) and type 1 insulin-like growth factor receptor (IGF1R) is associated with acquired drug resistance against EGFR-TKIs in NSCLC [7, >>8<<]." . . _:b592473722 . . _:b592473733 . _:b592473691 . _:b592473732 . _:b592473714 . _:b592473735 . _:b592473661 . . _:b592473654 "7"^^ . _:b592473769 . _:b592473844 . _:b592473734 . _:b592473655 "6"^^ . . . _:b45990700 . _:b592473729 . _:b592473652 "7"^^ . _:b592473728 . _:b592473653 "7"^^ . . _:b592473731 . . . _:b592473792 . _:b592473796 . _:b45990708 "Furthermore, decreased expression of E-cadherin [8, >>16<<, 17] was associated with reduced sensitivity to EGFR-TKIs, and restoration of E-cadherin expression improved cells' sensitivity to EGFR-TKIs [18]." . _:b592473730 . "PMC0" . _:b592473873 . _:b592473665 . _:b592473651 "7"^^ . _:b592473741 . . _:b592473821 . _:b592473740 . _:b592473847 . _:b592473743 . _:b45990709 . _:b592473848 . . . _:b592473661 "5"^^ . _:b592473742 . . . _:b592473660 "5"^^ . _:b592473737 . _:b592473673 . _:b592473663 "5"^^ . _:b592473736 . _:b45990716 "results" . . _:b592473662 "5"^^ . _:b592473739 . _:b592473663 . _:b592473715 . _:b592473706 . _:b45990706 . _:b592473738 . . _:b592473749 . _:b592473656 "6"^^ . . _:b45990715 . _:b592473659 "5"^^ . _:b592473864 . _:b592473748 . _:b592473657 "6"^^ . _:b592473861 . _:b592473668 . . _:b592473745 . _:b592473658 "5"^^ . _:b592473751 . . _:b592473669 "4"^^ . _:b592473743 . _:b592473750 . _:b592473657 . _:b592473668 "4"^^ . _:b592473728 . _:b592473745 . . _:b592473671 "4"^^ . . _:b592473744 . _:b592473771 . _:b592473670 "4"^^ . _:b592473766 . _:b592473746 . _:b592473747 . . _:b592473665 "4"^^ . . _:b592473746 . _:b592473843 . _:b592473664 "5"^^ . _:b592473757 . . _:b592473667 "4"^^ . . _:b592473756 . . _:b592473666 "4"^^ . _:b592473659 . _:b592473759 . . _:b592473677 "4"^^ . _:b592473758 . . _:b45990720 "For example, Morgillo et al. [>>7<<] found decreased EGFR and increased pIGF1R in erlotinib-resistant H460 cells." . _:b592473676 "4"^^ . _:b592473779 . _:b592473753 . _:b45990734 . _:b592473679 "4"^^ . _:b592473732 . _:b592473752 . . _:b592473678 "4"^^ . _:b592473755 . _:b45990727 . _:b592473673 "4"^^ . _:b592473709 . _:b592473754 . _:b592473672 "4"^^ . _:b592473765 .