title: Regulation of IGFBP6 gene and protein is mediated by the inverse expression and function of c-jun N-terminal kinase (JNK) and NFkappaB in a model of oral tumor cells.
abstract: The aim of this study is to identify potential gene and protein targets when nuclear factor kappa B (NFkappaB) and c-jun N-terminal kinase (JNK) were inversely expressed in oral tumors. To determine which genes were regulated synergistically by the inverse expression of NFkappaB and JNK, a pathway specific microarray analysis was performed. While either inhibition of NFkappaB or activation of JNK alone was unable to affect the IGFBP6 gene expression in microarray analysis, concomitant increase in JNK activation in the presence of NFkappaB inhibition increased the expression of this gene significantly. Synergistic increase in IGFBP6 gene expression was also confirmed by RT-PCR and Northern blot analysis of transfected cells. Accordingly, the levels of IGFBP6 protein secretion rose synergistically when JNK was over-expressed in NFkappaB knock down cells. In addition, increased expression of JNK in the absence of NFkappaB resulted in a significant induction of cell death in oral tumors when either left untreated or treated with TNF-alpha and TPA. Moreover, when JNK was inhibited by dominant negative JNK (APF), a significant decrease in cell death could be observed in TNF-alpha and TPA treated NFkappaB knock down oral tumors. Therefore, increased induction of IGFBP6 gene or protein expression in oral tumors could be regarded as a potential predictive marker of tumor sensitivity and could be used for prognostic purposes, since a significant correlation could be observed between increased induction of apoptotic cell death and elevated levels of IGFBP6 in these tumors.
authors.affiliation: Department of Radiation Oncology, UCLA School of Dentistry and Medicine, Los Angeles, CA 90095, USA.
authors.forename: Nicholas A
authors.initials: NA
authors.lastname: Cacalano
authors.forename: David
authors.initials: D
authors.lastname: Le
authors.forename: Avina
authors.initials: A
authors.lastname: Paranjpe
authors.forename: Mei-Ying
authors.initials: MY
authors.lastname: Wang
authors.forename: Augustine
authors.initials: A
authors.lastname: Fernandez
authors.forename: Tandik
authors.initials: T
authors.lastname: Evazyan
authors.forename: No-Hee
authors.initials: NH
authors.lastname: Park
authors.forename: Anahid
authors.initials: A
authors.lastname: Jewett
mesh_terms: D045744:Cell Line, Tumor; D005786:Gene Expression Regulation; D006801:Humans; D018976:Insulin-Like Growth Factor Binding Protein 6 / Q000235:genetics / Q000378:metabolism; D048031:JNK Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*; D009062:Mouth Neoplasms / Q000235:genetics / Q000378:metabolism; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism*; D020411:Oligonucleotide Array Sequence Analysis; D015398:Signal Transduction / Q000502:physiology
chemical_list: D018976:Insulin-Like Growth Factor Binding Protein 6; D016328:NF-kappa B; D048031:JNK Mitogen-Activated Protein Kinases