Novel p97/VCP inhibitor induces endoplasmic reticulum stress and apoptosis in both bortezomib-sensitive and -resistant multiple myeloma cells

Cancer Sci. 2019 Oct;110(10):3275-3287. doi: 10.1111/cas.14154. Epub 2019 Aug 14.

Abstract

p97/VCP is an endoplasmic reticulum (ER)-associated protein that belongs to the AAA (ATPases associated with diverse cellular activities) ATPase family. It has a variety of cellular functions including ER-associated protein degradation, autophagy, and aggresome formation. Recent studies have shown emerging roles of p97/VCP and its potential as a therapeutic target in several cancer subtypes including multiple myeloma (MM). We conducted a cell-based compound screen to exploit novel small compounds that have cytotoxic activity in myeloma cells. Among approximately 2000 compounds, OSSL_325096 showed relatively strong antiproliferative activity in MM cell lines (IC50 , 100-500 nmol/L). OSSL_325096 induced apoptosis in myeloma cell lines, including a bortezomib-resistant cell line and primary myeloma cells purified from patients. Accumulation of poly-ubiquitinated proteins, PERK, CHOP, and IREα, was observed in MM cell lines treated with OSSL_325096, suggesting that it induces ER stress in MM cells. OSSL_325096 has a similar chemical structure to DBeQ, a known p97/VCP inhibitor. Knockdown of the gene encoding p97/VCP induced apoptosis in myeloma cells, accompanied by accumulation of poly-ubiquitinated protein. IC50 of OSSL_325096 to myeloma cell lines were found to be lower (0.1-0.8 μmol/L) than those of DBeQ (2-5 μmol/L). In silico protein-drug-binding simulation suggested possible binding of OSSL_325096 to the ATP binding site in the D2 domain of p97/VCP. In cell-free ATPase assays, OSSL_325096 showed dose-dependent inhibition of p97/VCP ATPase activity. Finally, OSSL_325096 inhibited the growth of subcutaneous myeloma cell tumors in vivo. The present data suggest that OSSL_325096 exerts anti-myeloma activity, at least in part through p97/VCP inhibition.

Keywords: ERAD; OSSL_320596; apoptosis; myeloma; p97/VCP.

MeSH terms

  • Adenosine Triphosphatases / antagonists & inhibitors
  • Adenosine Triphosphatases / chemistry
  • Adenosine Triphosphatases / metabolism*
  • Animals
  • Binding Sites
  • Bortezomib / pharmacology
  • Cell Line, Tumor
  • Cell Proliferation / drug effects
  • Cell Survival / drug effects
  • Drug Resistance, Neoplasm / drug effects*
  • Drug Screening Assays, Antitumor
  • Endoplasmic Reticulum / drug effects
  • Endoplasmic Reticulum / metabolism*
  • Endoplasmic Reticulum Stress
  • Endoribonucleases / metabolism
  • Enzyme Inhibitors / administration & dosage*
  • Enzyme Inhibitors / chemistry
  • Enzyme Inhibitors / pharmacology
  • Female
  • Humans
  • Mice
  • Models, Molecular
  • Multiple Myeloma / drug therapy*
  • Multiple Myeloma / metabolism
  • Nuclear Proteins / antagonists & inhibitors
  • Nuclear Proteins / chemistry
  • Nuclear Proteins / metabolism*
  • Protein Serine-Threonine Kinases / metabolism
  • Small Molecule Libraries / administration & dosage*
  • Small Molecule Libraries / chemistry
  • Small Molecule Libraries / pharmacology
  • Transcription Factor CHOP / metabolism
  • Ubiquitination
  • Xenograft Model Antitumor Assays
  • eIF-2 Kinase / metabolism

Substances

  • DDIT3 protein, human
  • Enzyme Inhibitors
  • Nuclear Proteins
  • Small Molecule Libraries
  • Transcription Factor CHOP
  • Bortezomib
  • EIF2AK3 protein, human
  • ERN1 protein, human
  • Protein Serine-Threonine Kinases
  • eIF-2 Kinase
  • Endoribonucleases
  • Adenosine Triphosphatases
  • p97 ATPase