title: Loss of Nrdp1 enhances ErbB2/ErbB3-dependent breast tumor cell growth.
abstract: Dysregulation of ErbB receptor tyrosine kinases is thought to promote mammary tumor progression by stimulating tumor cell growth and invasion. Overexpression and aberrant activation of ErbB2/HER2 confer aggressive and malignant characteristics to breast cancer cells, and patients displaying ErbB2-amplified breast cancer face a worsened prognosis. Recent studies have established that ErbB2 and ErbB3 are commonly co-overexpressed in breast tumor cell lines and in patient samples. ErbB2 heterodimerizes with and activates the ErbB3 receptor, and the two receptors synergize in promoting growth factor-induced cell proliferation, transformation, and invasiveness. Our previous studies have shown that the neuregulin receptor degradation protein-1 (Nrdp1) E3 ubiquitin ligase specifically suppresses cellular ErbB3 levels by marking the receptor for proteolytic degradation. Here, we show that overexpression of Nrdp1 in human breast cancer cells results in the suppression of ErbB3 levels, accompanied by the inhibition of cell growth and motility and the attenuation of signal transduction pathways. In contrast, either Nrdp1 knockdown or the overexpression of a dominant-negative form enhances ErbB3 levels and cellular proliferation. Additionally, Nrdp1 expression levels inversely correlate with ErbB3 levels in primary human breast cancer tissue and in a mouse model of ErbB2 mammary tumorigenesis. Our observations suggest that Nrdp1-mediated ErbB3 degradation suppresses cellular growth and motility, and that Nrdp1 loss in breast tumors may promote tumor progression by augmenting ErbB2/ErbB3 signaling.
authors.affiliation: University of California Davis Cancer Center, Sacramento, CA 95817-2305, USA.
authors.forename: Lily
authors.initials: L
authors.lastname: Yen
authors.forename: Zhongwei
authors.initials: Z
authors.lastname: Cao
authors.forename: Xiuli
authors.initials: X
authors.lastname: Wu
authors.forename: Ellen R Q
authors.initials: ER
authors.lastname: Ingalla
authors.forename: Colin
authors.initials: C
authors.lastname: Baron
authors.forename: Lawrence J T
authors.initials: LJ
authors.lastname: Young
authors.forename: Jeffrey P
authors.initials: JP
authors.lastname: Gregg
authors.forename: Robert D
authors.initials: RD
authors.lastname: Cardiff
authors.forename: Alexander D
authors.initials: AD
authors.lastname: Borowsky
authors.forename: Colleen
authors.initials: C
authors.lastname: Sweeney
authors.forename: Kermit L
authors.initials: KL
authors.lastname: Carraway
mesh_terms: D000818:Animals; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D004441:Ecdysterone / Q000031:analogs & derivatives / Q000494:pharmacology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005260:Female; D005822:Genetic Vectors / Q000235:genetics; D006801:Humans; D015674:Mammary Neoplasms, Animal / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D051379:Mice; D008822:Mice, Transgenic; D009419:Nerve Tissue Proteins / Q000494:pharmacology; D020890:Neuregulin-1; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000235:genetics / Q000378:metabolism*; D020893:Receptor, ErbB-3 / Q000235:genetics / Q000378:metabolism*; D012190:Retroviridae / Q000235:genetics; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D014162:Transfection; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism* / Q000502:physiology
chemical_list: D004441:Ecdysterone; D048049:Extracellular Signal-Regulated MAP Kinases; D009419:Nerve Tissue Proteins; D020890:Neuregulin-1; D019869:Phosphatidylinositol 3-Kinases; D034741:RNA, Small Interfering; D018719:Erb-b2 Receptor Tyrosine Kinases; D020893:Receptor, ErbB-3; D044767:Ubiquitin-Protein Ligases; C094131:NRG1 protein, human; C055348:muristerone A; C452580:RNF41 protein, human