title: RNAi-mediated downregulation of uPAR synergizes with targeting of HER2 through the ERK pathway in breast cancer cells.
abstract: Overexpression of urokinase plasminogen activator receptor (uPAR) or HER2 (erbB-2) in breast cancer is associated with a poor prognosis. We previously reported that gene amplification and overexpression of HER2 and uPAR occur in 70% of HER2-amplified tumor cells from blood or tissue of patients with breast cancer. In this study, we first examined whether depletion of HER2 and uPAR synergized in suppression of the growth of breast cancer cells that overexpress both HER2 and uPAR (SKBR3 and ZR 751). The results showed that depletion of either HER2 or uPAR by RNA interference suppressed cell growth and induced cell apoptosis, but that these effects were significantly enhanced in cells depleted of both HER2 and uPAR. Mechanistic analysis demonstrated that silencing of HER2 and uPAR caused suppression of MAPK signal pathways, resulting in decrease of ERK activity and prompting a high p38/ERK activity ratio. The level of the phosphorylated form of ERK was decreased in cells depleted of HER2, uPAR or both, and the effect in cells depleted of both is the most evident. Moreover, downregulation of uPAR synergized with trastuzumab to suppress the growth and induce apoptosis of SKBR3 and ZR 751 cells. uPAR RNAi significantly enhanced the effect of trastuzumab on inhibition of MAPK signal pathways. In conclusion, targeting HER2 and uPAR has a synergistic inhibitory effect on breast cancer cells. Our results provide evidence that simultaneous downregulation of HER2 and uPAR may offer an effective tool for breast cancer therapy.
authors.affiliation: CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China.
authors.forename: Changfei
authors.initials: C
authors.lastname: Li
authors.forename: Sheng
authors.initials: S
authors.lastname: Cao
authors.forename: Zhen
authors.initials: Z
authors.lastname: Liu
authors.forename: Xin
authors.initials: X
authors.lastname: Ye
authors.forename: Lizhao
authors.initials: L
authors.lastname: Chen
authors.forename: Songdong
authors.initials: S
authors.lastname: Meng
mesh_terms: D000911:Antibodies, Monoclonal / Q000494:pharmacology; D061067:Antibodies, Monoclonal, Humanized; D017209:Apoptosis; D001943:Breast Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology; D002453:Cell Cycle / Q000187:drug effects; D002455:Cell Division; D045744:Cell Line, Tumor; D015536:Down-Regulation; D005109:Extracellular Matrix / Q000473:pathology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D005822:Genetic Vectors; D006801:Humans; D010957:Plasmids; D034622:RNA Interference / Q000502:physiology*; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D055293:Receptors, Urokinase Plasminogen Activator / Q000235:genetics*; D012844:Sincalide / Q000378:metabolism; D014162:Transfection; D000068878:Trastuzumab
chemical_list: D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D048049:Extracellular Signal-Regulated MAP Kinases; D018719:Erb-b2 Receptor Tyrosine Kinases; D055293:Receptors, Urokinase Plasminogen Activator; D012844:Sincalide; D000068878:Trastuzumab; C508053:ERBB2 protein, human