title: HER2 as therapeutic target for overcoming ATP-binding cassette transporter-mediated chemoresistance in small cell lung cancer.
abstract: Small cell lung cancer (SCLC) easily acquires multidrug resistance after successful initial therapy. Overexpression of ATP-binding cassette (ABC) transporters is important for the multidrug resistance. Among them, ABCB1 and ABCG2 are known to be upregulated in chemoresistant SCLC cells. We found that human epidermal growth factor receptor 2 (HER2) expressions are also upregulated in chemoresistant SBC-3/ETP, SBC-3/SN-38, and SBC-3/CDDP cells, compared with chemosensitive SBC-3 cells. Lapatinib, a tyrosine kinase inhibitor of HER2, could not suppress proliferation of these HER2-positive SCLC cells alone but successfully restored chemosensitivity to etoposide and SN-38 with a clinically applicable concentration. The reversal effect of lapatinib was thought to be caused by inhibition of drug efflux pump functions of ABC transporters, although lapatinib itself has been reported to be a substrate for them. Moreover, knocking down of HER2 by an short interfering RNA weakened the effect of lapatinib on ABCB1, indicating the involvement of HER2 in the inhibitory mechanisms. Notably, we showed that caveolin-1 and Src play key roles in modulating ABCB1 function via HER2 inactivation. In SBC-3/ETP cells, dephosphorylation of HER2 by lapatinib activates Src and successively leads to increased caveolin-1 phosphorylation. Through this process, caveolin-1 dissociates from HER2 and strengthens association with ABCB1, and finally impairs the pump functions. Furthermore, we showed that treatment by lapatinib in combination with etoposide or irinotecan significantly suppresses the growth of subcutaneous SBC-3/ETP and SBC-3/SN-38 tumors in mice, respectively. Collectively, these results indicate that combination therapy with lapatinib and cytotoxic agents could conquer ABC transporter-mediated chemoresistance especially in HER2-positive SCLC.
authors.affiliation: Department of Respiratory Medicine, Allergy and Rheumatic Diseases, Osaka University Graduate School of Medicine, Osaka University, Osaka, Japan.
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Minami
authors.forename: Takashi
authors.initials: T
authors.lastname: Kijima
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Otani
authors.forename: Satoshi
authors.initials: S
authors.lastname: Kohmo
authors.forename: Ryo
authors.initials: R
authors.lastname: Takahashi
authors.forename: Izumi
authors.initials: I
authors.lastname: Nagatomo
authors.forename: Haruhiko
authors.initials: H
authors.lastname: Hirata
authors.forename: Mayumi
authors.initials: M
authors.lastname: Suzuki
authors.forename: Koji
authors.initials: K
authors.lastname: Inoue
authors.forename: Yoshito
authors.initials: Y
authors.lastname: Takeda
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kida
authors.forename: Isao
authors.initials: I
authors.lastname: Tachibana
authors.forename: Atsushi
authors.initials: A
authors.lastname: Kumanogoh
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D045744:Cell Line, Tumor; D006801:Humans; D000077341:Lapatinib; D008175:Lung Neoplasms / Q000188:drug therapy* / Q000201:enzymology / Q000235:genetics; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D058990:Molecular Targeted Therapy; D011799:Quinazolines / Q000494:pharmacology*; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D055752:Small Cell Lung Carcinoma / Q000188:drug therapy* / Q000201:enzymology / Q000235:genetics; D014162:Transfection; D015854:Up-Regulation
chemical_list: D018528:ATP-Binding Cassette Transporters; D000970:Antineoplastic Agents; D000077341:Lapatinib; D011799:Quinazolines; D018719:Erb-b2 Receptor Tyrosine Kinases