title: Microarray-assisted pathway analysis identifies mitogen-activated protein kinase signaling as a mediator of resistance to the green tea polyphenol epigallocatechin 3-gallate in her-2/neu-overexpressing breast cancer cells.
abstract: Overexpression of the epidermal growth factor receptor family member Her-2/neu in breast cancer leads to autophosphorylation of the receptor and induction of multiple downstream signaling pathways, including the Akt kinase to nuclear factor-kappaB (NF-kappaB) cascade that is associated with poor prognosis. Previously, we showed that the green tea polyphenol epigallocatechin 3-gallate (EGCG) inhibits growth of NF639 Her-2/neu-driven breast cancer cells via reducing receptor autophosphorylation and downstream Akt and NF-kappaB activities. Interestingly, upon prolonged culture in the presence of EGCG, cells resistant to the polyphenol could be isolated. Here, we report that resistant cells have lost tyrosine phosphorylation on the Her-2/neu receptor. Surprisingly, they displayed elevated NF-kappaB activity, and inhibition of this activity sensitized cells to EGCG. Data from microarray studies of the original and resistant NF639 populations of cells were subjected to Gene Set Enrichment Analysis pathway assessment, which revealed that the mitogen activated protein kinase (MAPK) pathway was activated in the resistant cells. Treatment of the resistant cells with the MAPK inhibitor U0216 reduced growth in soft agar and invasive phenotype, whereas the combination of EGCG and U0216 resulted in cells with a cobblestone epithelial phenotype. Thus, activation of the MAPK pathway mediates resistance to EGCG.
authors.affiliation: Department of Biochemistry and Women's Health Interdisciplinary Research Center, Boston University School of Medicine, Boston, Massachusetts 02118, USA.
authors.forename: Shangqin
authors.initials: S
authors.lastname: Guo
authors.forename: Jun
authors.initials: J
authors.lastname: Lu
authors.forename: Aravind
authors.initials: A
authors.lastname: Subramanian
authors.forename: Gail E
authors.initials: GE
authors.lastname: Sonenshein
mesh_terms: D000818:Animals; D016588:Anticarcinogenic Agents / Q000494:pharmacology; D002392:Catechin / Q000031:analogs & derivatives* / Q000494:pharmacology; D002448:Cell Adhesion / Q000187:drug effects; D048708:Cell Growth Processes / Q000187:drug effects; D003907:Dexamethasone / Q000494:pharmacology; D019008:Drug Resistance, Neoplasm; D004789:Enzyme Activation; D020935:MAP Kinase Signaling System / Q000502:physiology*; D008325:Mammary Neoplasms, Experimental / Q000188:drug therapy* / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism; D020411:Oligonucleotide Array Sequence Analysis; D010766:Phosphorylation; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism
chemical_list: D016588:Anticarcinogenic Agents; D002392:Catechin; D003907:Dexamethasone; D020928:Mitogen-Activated Protein Kinases; D016328:NF-kappa B; D012333:RNA, Messenger; D018719:Erb-b2 Receptor Tyrosine Kinases; C045651:epigallocatechin gallate