title: Transcriptional repression of Mad-Max complex by human umbilical cord blood stem cells downregulates extracellular signal-regulated kinase in glioblastoma.
abstract: Previously, we have shown that human umbilical cord blood stem cell (hUCBSC) treatment downregulate cyclin D1 in glioma cells. To study the cell cycle progression and investigate the upstream molecules regulating cyclin D1 expression, we analyzed the involvement of extracellular signal-regulated kinase (ERK) and its functionality after treatment with hUCBSC. We observed downregulation of pERK after hUCBSC treatment at both transcriptional and translational levels. Increased translocation of ERK from cytoplasm to the nucleus was observed in glioma cells, whereas hUCBSC cocultures with glioma cells showed suppressed nuclear translocation. This finding suggests that hUCBSC regulates ERK by suppressing its phosphorylation at phospho-Thr(202)/Tyr(204) retarding pERK nuclear translocation. ERK promoter analysis has shown c-Myc binding sites, indicative of possible transcriptional interactions that regulate cyclin D1 and ERK expression levels. Treatment of U251 and 5310 glioma cells with U0126, a MEK/ERK inhibitor receded pERK and c-Myc levels. In another experiment, U251 and 5310 cells treated with 10074-G5, c-Myc/Max inhibitor displayed reduction in pERK and c-Myc levels suggestive of a positive feedback loop between ERK/c-Myc/Max molecules. In the present study, we show that glioma cells exhibit abundant c-Myc expression and increased c-Myc/Max activity. In contrast, the glioma cells cocultured with hUCBSC demonstrated high Mad1 expression that competitively binds to Max to repress the c-Myc/Max mediated gene transcription. Our studies thus elucidate the potential role of hUCBSC in controlling glioma cell cycle progression and invasion by limiting Max binding to c-Myc, thus regulating the expression of glioma cell cycle and invasion associated molecules such as ERK, integrins via increased levels of Mad1 expression.
authors.affiliation: Department of Cancer Biology and Pharmacology, University of Illinois College of Medicine at Peoria, Peoria, IL 61656, USA.
authors.forename: Kiran Kumar
authors.initials: KK
authors.lastname: Velpula
authors.forename: Venkata Ramesh
authors.initials: VR
authors.lastname: Dasari
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Tsung
authors.forename: Dzung H
authors.initials: DH
authors.lastname: Dinh
authors.forename: Jasti S
authors.initials: JS
authors.lastname: Rao
mesh_terms: D021581:Active Transport, Cell Nucleus; D000818:Animals; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors / Q000378:metabolism*; D001932:Brain Neoplasms / Q000201:enzymology / Q000473:pathology / Q000628:therapy*; D018797:Cell Cycle Proteins / Q000378:metabolism*; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D018920:Coculture Techniques; D036101:Cord Blood Stem Cell Transplantation; D015536:Down-Regulation; D048049:Extracellular Signal-Regulated MAP Kinases / Q000235:genetics / Q000378:metabolism*; D005312:Fetal Blood / Q000166:cytology; D051417:Focal Adhesion Kinase 1 / Q000378:metabolism; D059585:G1 Phase Cell Cycle Checkpoints; D005909:Glioblastoma / Q000201:enzymology / Q000473:pathology / Q000628:therapy*; D006801:Humans; D039001:Integrin alpha Chains / Q000378:metabolism; D019012:Integrin beta1 / Q000378:metabolism; D051379:Mice; D008819:Mice, Nude; D009361:Neoplasm Invasiveness; D009368:Neoplasm Transplantation; D009687:Nuclear Proteins / Q000378:metabolism*; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D018797:Cell Cycle Proteins; D039001:Integrin alpha Chains; D019012:Integrin beta1; C501384:MAD1L1 protein, human; C499330:MAX protein, human; C489427:MYC protein, human; D009687:Nuclear Proteins; D016271:Proto-Oncogene Proteins c-myc; C084613:integrin alpha9; D051417:Focal Adhesion Kinase 1; C496050:PTK2 protein, human; D048049:Extracellular Signal-Regulated MAP Kinases