title: An undesired effect of chemotherapy: gemcitabine promotes pancreatic cancer cell invasiveness through reactive oxygen species-dependent, nuclear factor κB- and hypoxia-inducible factor 1α-mediated up-regulation of CXCR4.
abstract: Recently, we have shown that CXCL12/CXCR4 signaling plays an important role in gemcitabine resistance of pancreatic cancer (PC) cells. Here, we explored the effect of gemcitabine on this resistance mechanism. Our data demonstrate that gemcitabine induces CXCR4 expression in two PC cell lines (MiaPaCa and Colo357) in a dose- and time-dependent manner. Gemcitabine-induced CXCR4 expression is dependent on reactive oxygen species (ROS) generation because it is abrogated by pretreatment of PC cells with the free radical scavenger N-acetyl-L-cysteine. CXCR4 up-regulation by gemcitabine correlates with time-dependent accumulation of NF-κB and HIF-1α in the nucleus. Enhanced binding of NF-κB and HIF-1α to the CXCR4 promoter is observed in gemcitabine-treated PC cells, whereas their silencing by RNA interference causes suppression of gemcitabine-induced CXCR4 expression. ROS induction upon gemcitabine treatment precedes the nuclear accumulation of NF-κB and HIF-1α, and suppression of ROS diminishes these effects. The effect of ROS on NF-κB and HIF-1α is mediated through activation of ERK1/2 and Akt, and their pharmacological inhibition also suppresses gemcitabine-induced CXCR4 up-regulation. Interestingly, our data demonstrate that nuclear accumulation of NF-κB results from phosphorylation-induced degradation of IκBα, whereas HIF-1α up-regulation is NF-κB-dependent. Lastly, our data demonstrate that gemcitabine-treated PC cells are more motile and exhibit significantly greater invasiveness against a CXCL12 gradient. Together, these findings reinforce the role of CXCL12/CXCR4 signaling in gemcitabine resistance and point toward an unintended and undesired effect of chemotherapy.
authors.affiliation: From the Department of Oncologic Sciences, Mitchell Cancer Institute, University of South Alabama, Mobile, Alabama 36604.
authors.forename: Sumit
authors.initials: S
authors.lastname: Arora
authors.affiliation: From the Department of Oncologic Sciences, Mitchell Cancer Institute, University of South Alabama, Mobile, Alabama 36604.
authors.forename: Arun
authors.initials: A
authors.lastname: Bhardwaj
authors.affiliation: From the Department of Oncologic Sciences, Mitchell Cancer Institute, University of South Alabama, Mobile, Alabama 36604.
authors.forename: Seema
authors.initials: S
authors.lastname: Singh
authors.affiliation: From the Department of Oncologic Sciences, Mitchell Cancer Institute, University of South Alabama, Mobile, Alabama 36604.
authors.forename: Sanjeev K
authors.initials: SK
authors.lastname: Srivastava
authors.affiliation: From the Department of Oncologic Sciences, Mitchell Cancer Institute, University of South Alabama, Mobile, Alabama 36604.
authors.forename: Steven
authors.initials: S
authors.lastname: McClellan
authors.affiliation: From the Department of Oncologic Sciences, Mitchell Cancer Institute, University of South Alabama, Mobile, Alabama 36604.
authors.forename: Chaitanya S
authors.initials: CS
authors.lastname: Nirodi
authors.affiliation: From the Department of Oncologic Sciences, Mitchell Cancer Institute, University of South Alabama, Mobile, Alabama 36604.
authors.forename: Gary A
authors.initials: GA
authors.lastname: Piazza
authors.affiliation: the Department of Pathology, University of Alabama at Birmingham, Birmingham, Alabama 35294, and.
authors.forename: William E
authors.initials: WE
authors.lastname: Grizzle
authors.affiliation: From the Department of Oncologic Sciences, Mitchell Cancer Institute, University of South Alabama, Mobile, Alabama 36604.
authors.forename: Laurie B
authors.initials: LB
authors.lastname: Owen
authors.affiliation: From the Department of Oncologic Sciences, Mitchell Cancer Institute, University of South Alabama, Mobile, Alabama 36604,; the Department of Biochemistry and Molecular Biology, College of Medicine, University of South Alabama, Mobile, Alabama 36688. Electronic address: asingh@usouthal.edu.
authors.forename: Ajay P
authors.initials: AP
authors.lastname: Singh
mesh_terms: D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects / Q000235:genetics; D003841:Deoxycytidine / Q000009:adverse effects / Q000031:analogs & derivatives* / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism*; D009361:Neoplasm Invasiveness; D010190:Pancreatic Neoplasms / Q000201:enzymology / Q000235:genetics / Q000473:pathology*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism*; D019718:Receptors, CXCR4 / Q000235:genetics* / Q000378:metabolism; D051996:Transcription Factor RelA / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects; D015854:Up-Regulation / Q000187:drug effects* / Q000235:genetics; D000093542:Gemcitabine
chemical_list: D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D016328:NF-kappa B; D017382:Reactive Oxygen Species; D019718:Receptors, CXCR4; D051996:Transcription Factor RelA; D003841:Deoxycytidine; D051057:Proto-Oncogene Proteins c-akt; D048049:Extracellular Signal-Regulated MAP Kinases; D000093542:Gemcitabine
keywords: CXCR4; Chromatography; Hypoxia-inducible Factor (HIF); NF-κB; Pancreatic Cancer; Reactive Oxygen Species (ROS)