GRB-7 facilitates HER-2/Neu-mediated signal transduction and tumor formation.
Growth factor receptor-bound protein-7 (GRB-7), an adaptor molecule, can interact with multiple signal transduction molecules. GRB-7 is amplified concurrently with HER-2/Neu in most, if not all, of breast cancer with chromosome 17q11-21 amplification. GRB-7 gene amplification is associated with RNA over-expression. We show GRB-7 protein is over-expressed by immunoblotting in breast cancer cell lines and primary breast tumors with HER-2/Neu protein over-expression. Over-expression of GRB-7 in MCF-7 breast cancer cells that over-express HER-2/Neu leads to activation of tyrosine phosphorylation of HER-2/Neu. Knockdown of GRB-7 expression in SKBR-3 breast cancer cells with naturally occurring HER-2/Neu gene amplification decreases tyrosine phosphorylation of HER-2/Neu. Activation of HER-2/Neu phosphorylation is associated with increase in tyrosine phosphorylation of phosphoinositide-specific lipase C-gamma-1 (PLC-gamma-1) and recruitment of PLC-gamma-1 to HER-2/Neu protein molecule. Activation of downstream protein kinase C (PKC) pathway is evidenced by increase in the phosphorylation of a common PKC substrate-myristoylated alanine-rich protein kinase C substrate (MARCKS). In addition, over-expression of GRB-7 in MCF-7 breast cancer cells that over-express HER-2/Neu leads to activation of AKT phosphorylation. Knockdown of GRB-7 expression in MB-453 and SKBR-3 breast cancer cells results in decrease in AKT phosphorylation. GRB-7 over-expression therefore facilitates activation of phosphorylation of HER-2/Neu and AKT in breast cancer cells with HER-2/Neu over-expression. GRB-7 over-expression in MCF-7 cells over-expressing HER-2/Neu leads to morphologic change of cells and promotes tumor xenograft growth in nude mice. GRB-7 over-expression therefore plays pivotal roles in activating signal transduction and promoting tumor growth in breast cancer cells with chromosome 17q11-21 amplification.
Bai
Tao
T
Division of Hematology and Medical Oncology, Oregon Health Sciences University, Portland VA Medical Center, Portland, OR 97239, USA.
Luoh
Shiuh-Wen
SW
D000818:Animals; D001943:Breast Neoplasms / Q000378:metabolism* / Q000473:pathology; D045744:Cell Line, Tumor; D002471:Cell Transformation, Neoplastic; D002886:Chromosomes, Human, Pair 17; D004789:Enzyme Activation; D005260:Female; D051382:GRB7 Adaptor Protein / Q000502:physiology*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D008819:Mice, Nude; D000076250:Myristoylated Alanine-Rich C Kinase Substrate; D009368:Neoplasm Transplantation; D051966:Phospholipase C gamma / Q000378:metabolism; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology*
D051382:GRB7 Adaptor Protein; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D000076250:Myristoylated Alanine-Rich C Kinase Substrate; D051966:Phospholipase C gamma; D051057:Proto-Oncogene Proteins c-akt; D018719:Erb-b2 Receptor Tyrosine Kinases; C495955:GRB7 protein, human; C000619710:MARCKS protein, human; C000619711:Marcks protein, mouse