Downregulation of the Arg/N-degron Pathway Sensitizes Cancer Cells to Chemotherapy In Vivo

Mol Ther. 2020 Apr 8;28(4):1092-1104. doi: 10.1016/j.ymthe.2020.01.021. Epub 2020 Jan 21.


The N-degron pathway is an emerging target for anti-tumor therapies, because of its capacity to positively regulate many hallmarks of cancer, including angiogenesis, cell proliferation, motility, and survival. Thus, inhibition of the N-degron pathway offers the potential to be a highly effective anti-cancer treatment. With the use of a small interfering RNA (siRNA)-mediated approach for selective downregulation of the four Arg/N-degron-dependent ubiquitin ligases, UBR1, UBR2, UBR4, and UBR5, we demonstrated decreased cell migration and proliferation and increased spontaneous apoptosis in cancer cells. Chronic treatment with lipid nanoparticles (LNPs) loaded with siRNA in mice efficiently downregulates the expression of UBR-ubiquitin ligases in the liver without any significant toxic effects but engages the immune system and causes inflammation. However, when used in a lower dose, in combination with a chemotherapeutic drug, downregulation of the Arg/N-degron pathway E3 ligases successfully reduced tumor load by decreasing proliferation and increasing apoptosis in a mouse model of hepatocellular carcinoma, while avoiding the inflammatory response. Our study demonstrates that UBR-ubiquitin ligases of the Arg/N-degron pathway are promising targets for the development of improved therapies for many cancer types.

Keywords: N-degron pathway; UBR-ubiquitin ligases; UBR1; UBR2; UBR4; UBR5; apoptosis; chemotherapy; hepatocellular carcinoma.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Calmodulin-Binding Proteins / antagonists & inhibitors
  • Calmodulin-Binding Proteins / genetics
  • Carcinoma, Hepatocellular / drug therapy*
  • Carcinoma, Hepatocellular / genetics
  • Cell Line, Tumor
  • Cell Movement / drug effects
  • Cell Proliferation / drug effects
  • Cell Survival / drug effects
  • Down-Regulation*
  • Doxorubicin / administration & dosage*
  • Doxorubicin / pharmacology
  • Drug Synergism
  • Gene Expression Regulation, Neoplastic / drug effects
  • Liposomes
  • Liver Neoplasms / drug therapy*
  • Liver Neoplasms / genetics
  • Mice
  • Nanoparticles
  • RNA, Small Interfering / administration & dosage*
  • RNA, Small Interfering / pharmacology
  • Ubiquitin-Protein Ligases / antagonists & inhibitors
  • Ubiquitin-Protein Ligases / genetics*
  • Xenograft Model Antitumor Assays


  • Calmodulin-Binding Proteins
  • Lipid Nanoparticles
  • Liposomes
  • RNA, Small Interfering
  • Doxorubicin
  • UBR5 protein, mouse
  • UBR2 protein, mouse
  • Ubiquitin-Protein Ligases
  • Ubr4 protein, mouse