title: Acquisition of apoptotic resistance in arsenic-induced malignant transformation: role of the JNK signal transduction pathway.
abstract: This study examined the role of signal transduction and apoptosis in malignant transformation induced by arsenic. Prior study showed that chronic arsenite exposure (500 nM, > or =18 weeks) induced malignant transformation in rat liver TRL 1215 cells. In the present work, these transformed cells were compared with passage-matched control cells. In addition, TRL 1215 cells were treated subchronically (up to 6 weeks) with arsenic (termed pre-transformed cells) to define events occurring prior to arsenic-induced transformation. Flow cytometry using annexin/FITC revealed that arsenic-induced apoptosis in transformed cells was markedly suppressed in comparison to control or pre-transformed cells. Ro318220, a strong activator of JNK, enhanced arsenite-induced apoptosis in transformed cells. Densitometric analysis of western blots revealed that the ratios of both Bcl-x(L)/Bax and Bcl-2/Bax were significantly increased (>2.5-fold) in arsenic-transformed cells. Transformed, pre-transformed and control cells were treated with arsenic and levels of phosphorylated extracellular signal-regulated kinases, ERK1/2, JNK1/2 and p38 were determined by western blot analysis. The three mitogen-activated protein kinases (MAPKs) were phosphorylated in a dose-dependent fashion in all cell types. However, the levels of phosphorylated JNK1/2 were markedly decreased in the arsenic-transformed cells, whereas in pre-transformed cells the levels of phosphorylated MAPKs remained the same as in control cells. JNK kinase activity was suppressed in transformed cells whereas Ro318220 enhanced this activity. Thus, during arsenic-induced malignant transformation resistance to apoptosis develops, possibly due to perturbation of the JNK pathway.
authors.affiliation: Inorganic Carcinogenesis Section, Laboratory of Comparative Carcinogenesis, National Cancer Institute at the National Institute of Environmental Health Sciences, PO Box 12233, Mail Drop F0-09, 111 Alexander Drive, Research Triangle Park, NC 27709, USA.
authors.forename: Wei
authors.initials: W
authors.lastname: Qu
authors.forename: Carl D
authors.initials: CD
authors.lastname: Bortner
authors.forename: Teruaki
authors.initials: T
authors.lastname: Sakurai
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Hobson
authors.forename: Michael P
authors.initials: MP
authors.lastname: Waalkes
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D001151:Arsenic / Q000494:pharmacology*; D015153:Blotting, Western; D002461:Cell Line, Transformed; D002471:Cell Transformation, Neoplastic / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D004351:Drug Resistance; D004789:Enzyme Activation / Q000187:drug effects; D005434:Flow Cytometry; D022781:Hepatocytes / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism / Q000473:pathology; D020287:In Situ Nick-End Labeling; D007211:Indoles / Q000494:pharmacology; D048031:JNK Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D051381:Rats; D011916:Rats, Inbred F344; D015398:Signal Transduction / Q000187:drug effects*; D051028:bcl-2-Associated X Protein
chemical_list: C494828:Bax protein, rat; D007211:Indoles; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D051028:bcl-2-Associated X Protein; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D020929:Mitogen-Activated Protein Kinase Kinases; D001151:Arsenic; C064758:Ro 31-8220