title: Regulation of the multidrug resistance transporter P-glycoprotein in multicellular prostate tumor spheroids by hyperthermia and reactive oxygen species.
abstract: Hyperthermia is an important component of many cancer treatment protocols. In our study the regulation of the multidrug resistance (MDR) transporter P-glycoprotein by hyperthermia was studied in multicellular prostate tumor spheroids. Hyperthermia treatment of small (50-100 microm) tumor spheroids significantly increased P-glycoprotein and mdr-1 mRNA expression with a maximum effect at 42 degrees C, whereas only moderate elevation of P-glycoprotein was found in large (350-450 microm) tumor spheroids. Hyperthermia caused an elevation of intracellular reactive oxygen species (ROS). Inhibition of ROS generation with NADPH-oxidase inhibitors diphenylen iodonium (DPI) and 4-(2-aminoethyl)benzenesulfonyl fluoride (AEBSF) abolished P-glycoprotein expression but did not affect its transcript levels following heat treatment. This indicates that P-glycoprotein levels are controlled by regulating its translation rate or stability. Hyperthermia incubation resulted in a differential activation of p38 mitogen-activated protein kinase (MAPK), extracellular regulated kinase 1,2 (ERK1,2), and c-jun N-terminal kinase (JNK) immediately, 4 hr and 24 hr after treatment. Furthermore, upregulation of hypoxia-inducible factor 1alpha (HIF-1alpha) was observed. Elevation of HIF-1alpha and P-glycoprotein expression following hyperthermia treatment were abolished upon coadministration of the p38 inhibitor SB203580. In contrast the JNK inhibitor SP600125 and the ERK1,2 inhibitor UO126 resulted in increase of HIF-1alpha and P-glycoprotein in the control as well as the hyperthermia-treated samples, indicating negative regulation of intrinsic HIF-1alpha and P-glycoprotein expression by ERK1,2 and JNK signaling cascades. In summary our data demonstrate that hyperthermia-induced upregulation of P-glycoprotein and HIF-1alpha is mediated by activation of p38, whereas ERK1,2 and JNK are involved in repression of P-glycoprotein and HIF-1alpha under control conditions.
authors.affiliation: Institute of Neurophysiology, University of Cologne, Cologne, Germany.
authors.forename: Maria
authors.initials: M
authors.lastname: Wartenberg
authors.forename: Sabina
authors.initials: S
authors.lastname: Gronczynska
authors.forename: Mohamed M
authors.initials: MM
authors.lastname: Bekhite
authors.forename: Tomo
authors.initials: T
authors.lastname: Saric
authors.forename: Wilhelm
authors.initials: W
authors.lastname: Niedermeier
authors.forename: Jürgen
authors.initials: J
authors.lastname: Hescheler
authors.forename: Heinrich
authors.initials: H
authors.lastname: Sauer
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000096:biosynthesis*; D004268:DNA-Binding Proteins / Q000096:biosynthesis* / Q000494:pharmacology; D018257:Helix-Loop-Helix Motifs; D006801:Humans; D006979:Hyperthermia, Induced; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D008297:Male; D048052:Mitogen-Activated Protein Kinase 3 / Q000494:pharmacology; D009687:Nuclear Proteins / Q000096:biosynthesis* / Q000494:pharmacology; D011471:Prostatic Neoplasms / Q000473:pathology*; D012333:RNA, Messenger / Q000096:biosynthesis; D017382:Reactive Oxygen Species; D018874:Spheroids, Cellular; D014157:Transcription Factors / Q000096:biosynthesis* / Q000494:pharmacology; D015854:Up-Regulation; D048051:p38 Mitogen-Activated Protein Kinases / Q000494:pharmacology
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D004268:DNA-Binding Proteins; C497442:HIF1A protein, human; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D009687:Nuclear Proteins; D012333:RNA, Messenger; D017382:Reactive Oxygen Species; D014157:Transcription Factors; D048052:Mitogen-Activated Protein Kinase 3; D048051:p38 Mitogen-Activated Protein Kinases