title: EGFR mediates docetaxel resistance in human castration-resistant prostate cancer through the Akt-dependent expression of ABCB1 (MDR1).
abstract: Recent studies have shown that docetaxel-based chemotherapy confers a survival benefit in patients with castration-resistant prostate cancer (PC). Also epidermal growth factor receptor (EGFR) was found to have multiple roles in prostatic tumorigenesis. However, the EGFR-mediated chemoresistance mechanism in human PC was not well delineated. In this study, we explored the mechanism of EGFR-mediated docetaxel resistance in PC. A series of stable docetaxel-resistant PC/DX sublines were established at our laboratory. The docetaxel IC50s of PC3 and PC/DX25 cells were 0.01 and 1.33 μM, respectively. Cellular resistance to docetaxel was significantly associated with increased EGFR and EGFR activation in PC/DX25. There was a dose-dependent increase in EGFR expression associated with the magnitude of docetaxel resistance. Expression of EGFR in PC/DX25 was higher than that in PC3, RWPE-1 and LNCaP cells. Similar results were also found in human PC tissues by immunohistochemical staining. We showed that docetaxel sensitivity can be stored in PC/DX25 cells by knockdown and inactivation of EGFR expression through EGFR siRNA and specific inhibitors, respectively. Contrarily, overexpression of EGFR or recombinant EGF protein treatment could rescue PC3 cells from docetaxel-mediated cytotoxicity. Gefitninb (ZD1839) significantly inhibited the growth of PC/DX25 cells by MTT in vitro and on xenografted nude mice in vivo. Moreover, EGFR-mediated docetaxel resistance occurred through the Akt-dependent ABCB1 expression in PC cells. These findings demonstrated EGFR played an important role in docetaxel-resistant PC and EGFR inhibition may enhance the therapeutic efficacy of docetaxel-based treatment.
authors.affiliation: Institute of Biochemistry, Kaohsiung Medical University, Kaohsiung, Taiwan.
authors.forename: Tzyh-Chyuan
authors.initials: TC
authors.lastname: Hour
authors.forename: Shiu-Dong
authors.initials: SD
authors.lastname: Chung
authors.forename: Wang-Yi
authors.initials: WY
authors.lastname: Kang
authors.forename: Ying-Chu
authors.initials: YC
authors.lastname: Lin
authors.forename: Shu-Ju
authors.initials: SJ
authors.lastname: Chuang
authors.forename: A-Mei
authors.initials: AM
authors.lastname: Huang
authors.forename: Wen-Jeng
authors.initials: WJ
authors.lastname: Wu
authors.forename: Shu-Pin
authors.initials: SP
authors.lastname: Huang
authors.forename: Chao-Yuan
authors.initials: CY
authors.lastname: Huang
authors.forename: Yeong-Shiau
authors.initials: YS
authors.lastname: Pu
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B / Q000235:genetics / Q000378:metabolism; D000818:Animals; D000970:Antineoplastic Agents / Q000008:administration & dosage / Q000627:therapeutic use*; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D000077143:Docetaxel; D019008:Drug Resistance, Neoplasm / Q000235:genetics; D066246:ErbB Receptors / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D008297:Male; D008807:Mice, Inbred BALB C; D064129:Prostatic Neoplasms, Castration-Resistant / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D015398:Signal Transduction; D043823:Taxoids / Q000008:administration & dosage / Q000627:therapeutic use*; D023041:Xenograft Model Antitumor Assays
chemical_list: C513055:ABCB1 protein, human; D018435:ATP Binding Cassette Transporter, Subfamily B; D000970:Antineoplastic Agents; D034741:RNA, Small Interfering; D043823:Taxoids; D000077143:Docetaxel; C512478:EGFR protein, human; D066246:ErbB Receptors; D051057:Proto-Oncogene Proteins c-akt