title: Gefitinib circumvents hypoxia-induced drug resistance by the modulation of HIF-1alpha.
abstract: Hypoxia-inducible factor-1alpha (HIF-1alpha) is a transcriptional factor which is activated by hypoxia and associated with cell survival, proliferation and drug resistance. Recent studies have shown that the down-stream molecules of the epidermal growth factor receptor (EGFR) signal are involved in the hypoxia-dependent or -independent HIF-1alpha protein accumulation. Thus, we hypothesized that an EGFR-TK inhibitor, gefitinib, might circumvent the hypoxia-induced drug resistance via the regulation of HIF-1alpha expression. In our data, treatment of gefitinib suppressed induced HIF-1alpha by hypoxia. This action of gefitinib was caused by reduced protein stability without any change in the level of HIF-1alpha mRNA. The effect of gefitinib on down-regulation of HIF-1alpha was reversed by transfection of constitutively active form of Akt. The cellular response to gefitinib was similar in both normoxia and hypoxia condition. However, the response to conventional chemotherapeutic drugs decreased >50% under hypoxia condition and they did not change HIF-1alpha expression. In addition, the suppression of HIF-1alpha using siRNA overcame partially hypoxia-induced drug resistance. In conclusion, gefitinib was able to circumvent hypoxia-induced drug resistance suggesting that the effective suppression of HIF-1alpha by the inhibition of EGFR-Akt pathway may overcome the hypoxia-induced drug resistance.
authors.affiliation: Department of Internal Medicine, Korea Cancer Center Hospital, Korea Institute of Radiological and Medical Science, Seoul 139-706, Korea.
authors.forename: Jin Kyung
authors.initials: JK
authors.lastname: Rho
authors.forename: Yun Jung
authors.initials: YJ
authors.lastname: Choi
authors.forename: Jin Kyung
authors.initials: JK
authors.lastname: Lee
authors.forename: Baek-Yeol
authors.initials: BY
authors.lastname: Ryoo
authors.forename: Im Ii
authors.initials: II
authors.lastname: Na
authors.forename: Sung Hyun
authors.initials: SH
authors.lastname: Yang
authors.forename: Cheol Hyeon
authors.initials: CH
authors.lastname: Kim
authors.forename: Young Do
authors.initials: YD
authors.lastname: Yoo
authors.forename: Jae Cheol
authors.initials: JC
authors.lastname: Lee
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D015153:Blotting, Western; D015687:Cell Hypoxia / Q000187:drug effects* / Q000235:genetics; D045744:Cell Line, Tumor; D019008:Drug Resistance, Neoplasm / Q000187:drug effects* / Q000235:genetics; D005434:Flow Cytometry; D000077156:Gefitinib; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D011799:Quinazolines / Q000494:pharmacology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D014162:Transfection
chemical_list: D000970:Antineoplastic Agents; C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D011799:Quinazolines; D000077156:Gefitinib