Reactivation of p53 by novel MDM2 inhibitors: implications for pancreatic cancer therapy

Curr Cancer Drug Targets. 2010 May;10(3):319-31. doi: 10.2174/156800910791190229.

Abstract

The present study is the first to show in pancreatic cancer (PC) the growth inhibition and apoptosis by novel MDM2 inhibitors (MI-319 & 219) through reactivation of p53 pathway. Our results highlight two new secondary targets of MDM2 inhibitor 'SIRT1' and Ku70. SIRT1 which has a role in ageing and cancer and is known to regulate p53 signaling through acetylation. Ku70 is a key component of non-homologous end joining machinery in the DNA damage pathway and is known to regulate apoptosis by blocking Bax entry into mitochondria. Growth inhibition and apoptosis by MI-219, MI-319 was accompanied by increase in levels of p53 along with p21(WAF1) and the proapoptotic Puma. SiRNA against p21(WAF1) abrogated the growth inhibition of PC cells confirming p21(WAF1) as a key player downstream of activated p53. Immunoprecipitation-western blot analysis revealed reduced association of MDM2-p53 interaction in drug exposed PC cells. In combination studies, the inhibitors synergistically augmented anti-tumor effects of therapeutic drug gemcitabine both in terms of cell growth inhibition as well as apoptosis. Surface plasmon resonance studies confirmed strong binding between MI-319 and Ku70 (K(D) 170 nM). Western blot revealed suppression of SIRT1 and Ku70 with simultaneous upregulation of acetyl-p53 (Lys379) and Bax. Co-Immunoprecipitation studies confirmed that MI-319 could disrupt Ku70-Bax and SIRT1-Bax interaction. Further, using wt-p53 xenograft of Capan-2, we found that oral administration of MI-319 at 300 mg/kg for 14 days resulted in significant tumor growth inhibition without any observed toxicity to the animals. No tumor inhibition was found in mut-p53 BxPC-3 xenografts. In light of our results, the inhibitors of MDM2 warrant clinical investigation as new agents for PC treatment.

Publication types

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

MeSH terms

  • Animals
  • Antigens, Nuclear / metabolism
  • Antineoplastic Agents / pharmacology*
  • Apoptosis / drug effects
  • Blotting, Western
  • Cell Cycle / drug effects
  • Cell Line, Tumor
  • Cell Proliferation / drug effects
  • Cyclin-Dependent Kinase Inhibitor p21 / metabolism
  • DNA-Binding Proteins / metabolism
  • Deoxycytidine / analogs & derivatives
  • Deoxycytidine / pharmacology
  • Dose-Response Relationship, Drug
  • Enzyme Inhibitors / pharmacology*
  • Female
  • Gemcitabine
  • Humans
  • Immunoprecipitation
  • Indoles / pharmacology*
  • Ku Autoantigen
  • Mice
  • Mice, Inbred ICR
  • Mice, SCID
  • Pancreatic Neoplasms / drug therapy*
  • Pancreatic Neoplasms / enzymology
  • Pancreatic Neoplasms / genetics
  • Pancreatic Neoplasms / pathology
  • Protein Binding
  • Proto-Oncogene Proteins c-mdm2 / antagonists & inhibitors*
  • Proto-Oncogene Proteins c-mdm2 / metabolism
  • RNA Interference
  • Sirtuin 1 / metabolism
  • Spiro Compounds / pharmacology*
  • Surface Plasmon Resonance
  • Time Factors
  • Transfection
  • Tumor Burden
  • Tumor Suppressor Protein p53 / genetics
  • Tumor Suppressor Protein p53 / metabolism*
  • Xenograft Model Antitumor Assays
  • bcl-2-Associated X Protein / metabolism

Substances

  • Antigens, Nuclear
  • Antineoplastic Agents
  • BAX protein, human
  • CDKN1A protein, human
  • Cyclin-Dependent Kinase Inhibitor p21
  • DNA-Binding Proteins
  • Enzyme Inhibitors
  • Indoles
  • MI 319
  • MI-291
  • Spiro Compounds
  • TP53 protein, human
  • Tumor Suppressor Protein p53
  • bcl-2-Associated X Protein
  • Deoxycytidine
  • MDM2 protein, human
  • Proto-Oncogene Proteins c-mdm2
  • SIRT1 protein, human
  • Sirtuin 1
  • Xrcc6 protein, human
  • Xrcc6 protein, mouse
  • Ku Autoantigen
  • Gemcitabine