title: The mRNA-binding protein HuR promotes hypoxia-induced chemoresistance through posttranscriptional regulation of the proto-oncogene PIM1 in pancreatic cancer cells.
abstract: Previously, it has been shown that pancreatic ductal adenocarcinoma (PDA) tumors exhibit high levels of hypoxia, characterized by low oxygen pressure (pO2) and decreased O2 intracellular perfusion. Chronic hypoxia is strongly associated with resistance to cytotoxic chemotherapy and chemoradiation in an understudied phenomenon known as hypoxia-induced chemoresistance. The hypoxia-inducible, pro-oncogenic, serine-threonine kinase PIM1 (Proviral Integration site for Moloney murine leukemia virus 1) has emerged as a key regulator of hypoxia-induced chemoresistance in PDA and other cancers. Although its role in therapeutic resistance has been described previously, the molecular mechanism behind PIM1 overexpression in PDA is unknown. Here, we demonstrate that cis-acting AU-rich elements (ARE) present within a 38-base pair region of the PIM1 mRNA 3'-untranslated region mediate a regulatory interaction with the mRNA stability factor HuR (Hu antigen R) in the context of tumor hypoxia. Predominantly expressed in the nucleus in PDA cells, HuR translocates to the cytoplasm in response to hypoxic stress and stabilizes the PIM1 mRNA transcript, resulting in PIM1 protein overexpression. A reverse-phase protein array revealed that HuR-mediated regulation of PIM1 protects cells from hypoxic stress through phosphorylation and inactivation of the apoptotic effector BAD and activation of MEK1/2. Importantly, pharmacological inhibition of HuR by MS-444 inhibits HuR homodimerization and its cytoplasmic translocation, abrogates hypoxia-induced PIM1 overexpression and markedly enhances PDA cell sensitivity to oxaliplatin and 5-fluorouracil under physiologic low oxygen conditions. Taken together, these results support the notion that HuR has prosurvival properties in PDA cells by enabling them with growth advantages in stressful tumor microenvironment niches. Accordingly, these studies provide evidence that therapeutic disruption of HuR's regulation of PIM1 may be a key strategy in breaking an elusive chemotherapeutic resistance mechanism acquired by PDA cells that reside in hypoxic PDA microenvironments.
authors.affiliation: Department of Pharmacology and Experimental Therapeutics, Division of Clinical Pharmacology, Thomas Jefferson University, Philadelphia, PA, USA.|Department of Surgery, Thomas Jefferson University, Philadelphia, PA, USA.
authors.forename: F F
authors.initials: FF
authors.lastname: Blanco
authors.affiliation: Department of Surgery, Thomas Jefferson University, Philadelphia, PA, USA.
authors.forename: M
authors.initials: M
authors.lastname: Jimbo
authors.affiliation: Center for Applied Proteomics and Molecular Medicine, School of Systems Biology, George Mason University, Manassas, VA, USA.
authors.forename: J
authors.initials: J
authors.lastname: Wulfkuhle
authors.affiliation: Center for Applied Proteomics and Molecular Medicine, School of Systems Biology, George Mason University, Manassas, VA, USA.
authors.forename: I
authors.initials: I
authors.lastname: Gallagher
authors.affiliation: Center for Applied Proteomics and Molecular Medicine, School of Systems Biology, George Mason University, Manassas, VA, USA.
authors.forename: J
authors.initials: J
authors.lastname: Deng
authors.affiliation: Department of Surgery, Thomas Jefferson University, Philadelphia, PA, USA.
authors.forename: L
authors.initials: L
authors.lastname: Enyenihi
authors.affiliation: Novartis Institutes for Biomedical Research, Novartis, Switzerland.
authors.forename: N
authors.initials: N
authors.lastname: Meisner-Kober
authors.affiliation: Center for Computational Medicine, Thomas Jefferson University, Philadelphia, PA, USA.
authors.forename: E
authors.initials: E
authors.lastname: Londin
authors.affiliation: Center for Computational Medicine, Thomas Jefferson University, Philadelphia, PA, USA.
authors.forename: I
authors.initials: I
authors.lastname: Rigoutsos
authors.affiliation: Lankenau Institute for Medical Research, Philadelphia, PA, USA.
authors.forename: J A
authors.initials: JA
authors.lastname: Sawicki
authors.affiliation: Department of Orthopedic Surgery, Thomas Jefferson University, Philadelphia, PA, USA.
authors.forename: M V
authors.initials: MV
authors.lastname: Risbud
authors.affiliation: Department of Pathology, University of Texas Southwestern Medical Center, Dallas, TX, USA.
authors.forename: A K
authors.initials: AK
authors.lastname: Witkiewicz
authors.affiliation: Department of Pathology, Thomas Jefferson University, Philadelphia, PA, USA.
authors.forename: P A
authors.initials: PA
authors.lastname: McCue
authors.affiliation: Department of Pathology, Thomas Jefferson University, Philadelphia, PA, USA.
authors.forename: W
authors.initials: W
authors.lastname: Jiang
authors.affiliation: Department of Cancer Biology, Thomas Jefferson University, Philadelphia, PA, USA.
authors.forename: H
authors.initials: H
authors.lastname: Rui
authors.affiliation: Department of Surgery, Thomas Jefferson University, Philadelphia, PA, USA.
authors.forename: C J
authors.initials: CJ
authors.lastname: Yeo
authors.affiliation: Center for Applied Proteomics and Molecular Medicine, School of Systems Biology, George Mason University, Manassas, VA, USA.
authors.forename: E
authors.initials: E
authors.lastname: Petricoin
authors.affiliation: Department of Surgery, Thomas Jefferson University, Philadelphia, PA, USA.
authors.forename: J M
authors.initials: JM
authors.lastname: Winter
authors.affiliation: Department of Surgery, Thomas Jefferson University, Philadelphia, PA, USA.
authors.forename: J R
authors.initials: JR
authors.lastname: Brody
mesh_terms: D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism; D002470:Cell Survival; D019008:Drug Resistance, Neoplasm; D000067780:ELAV-Like Protein 1 / Q000502:physiology*; D005472:Fluorouracil / Q000494:pharmacology; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D009944:Organoplatinum Compounds / Q000494:pharmacology; D000077150:Oxaliplatin; D010100:Oxygen / Q000378:metabolism; D010190:Pancreatic Neoplasms / Q000235:genetics*; D000090063:Proto-Oncogene Mas; D051573:Proto-Oncogene Proteins c-pim-1 / Q000235:genetics*; D012333:RNA, Messenger / Q000378:metabolism
chemical_list: D000067780:ELAV-Like Protein 1; C000715470:MAS1 protein, human; D009944:Organoplatinum Compounds; D000090063:Proto-Oncogene Mas; D012333:RNA, Messenger; D000077150:Oxaliplatin; C496634:PIM1 protein, human; D051573:Proto-Oncogene Proteins c-pim-1; D010100:Oxygen; D005472:Fluorouracil