title: Anterior gradient 2 is a binding stabilizer of hypoxia inducible factor-1α that enhances CoCl2 -induced doxorubicin resistance in breast cancer cells.
abstract: Hypoxia inducible factor-1α (HIF-1α) is associated with human breast cancer chemoresistance. Various reports have suggested that multiple pathways are involved in HIF-1α induction and that the molecular mechanisms regulating HIF-1α-induced chemoresistance are still not fully understood. Here, we report that anterior gradient 2 (AGR2), a proposed breast cancer biomarker, is an essential regulator in hypoxia-induced doxorubicin resistance through the binding and stabilization of HIF-1α. Our results show that knockdown of AGR2 in MCF-7 cells leads to the suppression of HIF-1α-induced doxorubicin resistance, whereas elevated levels of AGR2 in MDA-MB-231 cells enhance HIF-1α-induced doxorubicin resistance. AGR2 expression, in turn, is upregulated by the hypoxic induction of HIF-1α at both translational and transcriptional levels via a hypoxia-responsive region from -937 to -912 bp on the AGR2 promoter sequence. By specific binding to HIF-1α, the increased level of intracellular AGR2 stabilizes HIF-1α and delays its proteasomal degradation. Finally, we found that AGR2-stabilized HIF-1α escalates multiple drug resistance protein 1 (MDR1) mRNA levels and limits doxorubicin intake of MCF-7 cells, whereas MCF-7/ADR, a doxorubicin resistant cell line with deficient AGR2 and HIF-1α, acquires wild-type MDR1 overexpression. Our findings, for the first time, describe AGR2 as an important regulator in chemical hypoxia-induced doxorubicin resistance in breast cancer cells, providing a possible explanation for the variable levels of chemoresistance in breast cancers and further validating AGR2 as a potential anti-breast cancer therapeutic target.
authors.affiliation: School of Pharmacy, Shanghai Jiao Tong University, Shanghai, China.
authors.forename: Zheqi
authors.initials: Z
authors.lastname: Li
authors.affiliation: School of Pharmacy, Shanghai Jiao Tong University, Shanghai, China.
authors.forename: Qi
authors.initials: Q
authors.lastname: Zhu
authors.affiliation: School of Pharmacy, Shanghai Jiao Tong University, Shanghai, China.
authors.forename: Lingyun
authors.initials: L
authors.lastname: Hu
authors.affiliation: School of Pharmacy, Shanghai Jiao Tong University, Shanghai, China.
authors.forename: Hao
authors.initials: H
authors.lastname: Chen
authors.affiliation: School of Pharmacy, Shanghai Jiao Tong University, Shanghai, China.
authors.forename: Zhenghua
authors.identifier: http://orcid.org/0000-0001-8639-9689
authors.initials: Z
authors.lastname: Wu
authors.affiliation: School of Pharmacy, Shanghai Jiao Tong University, Shanghai, China.|Engineering Research Center of Cell and Therapeutic Antibody, Ministry of Education, Shanghai, China.
authors.forename: Dawei
authors.initials: D
authors.lastname: Li
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000378:metabolism*; D045744:Cell Line, Tumor; D003035:Cobalt / Q000494:pharmacology; D004317:Doxorubicin / Q000494:pharmacology; D019008:Drug Resistance, Neoplasm / Q000502:physiology*; D005260:Female; D005455:Fluorescent Antibody Technique; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism*; D047468:Immunoprecipitation; D009088:Mucoproteins; D015513:Oncogene Proteins; D011506:Proteins / Q000378:metabolism*; D034741:RNA, Small Interfering; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014162:Transfection
chemical_list: C502296:AGR2 protein, human; D000970:Antineoplastic Agents; C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D009088:Mucoproteins; D015513:Oncogene Proteins; D011506:Proteins; D034741:RNA, Small Interfering; D003035:Cobalt; D004317:Doxorubicin; C018021:cobaltous chloride
keywords: Anterior gradient 2; chemical hypoxia; doxorubicin resistance; hypoxia inducible factor-1α; hypoxia responsive element