The pan-HER family tyrosine kinase inhibitor afatinib overcomes HER3 ligand heregulin-mediated resistance to EGFR inhibitors in non-small cell lung cancer
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Kimio Yonesaka1, Keita Kudo1, Satomi Nishida1, Takayuki Takahama1, Tsutomu Iwasa1, Takeshi Yoshida1, Kaoru Tanaka1, Masayuki Takeda1, Hiroyasu Kaneda1, Isamu Okamoto2, Kazuto Nishio3, Kazuhiko Nakagawa1
1Department of Medical Oncology, Kinki University School of Medicine, Osaka, Japan
2Center for Clinical and Translational Research, Kyushu University, Fukuoka, Kyushu, Japan
3Department of Genome Biology, Kinki University School of Medicine, Osaka, Japan
Kimio Yonesaka, e-mail: firstname.lastname@example.org
Keywords: afatinib, erlotinib, heregulin, non-small cell lung cancer, human epidermal growth factor receptor
Received: June 18, 2015 Accepted: September 04, 2015 Published: September 15, 2015
Afatinib is a second generation epidermal growth factor receptor-tyrosine kinase inhibitor (EGFR-TKI) characterized as an irreversible pan-human EGFR (HER) family inhibitor. Afatinib remains effective for a subpopulation of patients with non-small cell lung cancer (NSCLC) with acquired resistance to first generation EGFF-TKIs such as erlotinib. Heregulin activates HER3 in an autocrine fashion and causes erlotinib resistance in NSCLC. Here we examine whether afatinib is effective against heregulin-overexpressing NSCLCs harboring EGFR activating mutations. Afatinib but not erlotinib decreased EGFR mutant NSCLC PC9HRG cell proliferation in vitro and in mouse xenografts. Afatinib inhibited phosphorylation of the cell signaling pathway proteins HER3, EGFR, HER2, and HER4, likely by prevention of trans-phosphorylation as HER3 kinase activity is inadequate for auto-phosphorylation. Afatinib, unlike erlotinib, inhibited AKT activation, resulting in elevated apoptosis in PC9HRG cells. Clinically, a subpopulation of 33 patients with EGFR mutations and NSCLC who had received first generation EGFR-TKIs exhibited elevated plasma heregulin levels compared to healthy volunteers; one of these achieved a response with afatinib therapy despite having previously developed erlotinib resistance. Afatinib can overcome heregulin-mediated resistance to erlotinib in EGFR mutant NSCLC. Further studies are necessary to determine whether heregulin can predict afatinib efficacy after development offirst generation EGFR-TKI resistance.
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