DARPP-32 increases interactions between epidermal growth factor receptor and ERBB3 to promote tumor resistance to gefitinib

Gastroenterology. 2011 Nov;141(5):1738-48.e1-2. doi: 10.1053/j.gastro.2011.06.070. Epub 2011 Jul 7.


Background & aims: Dopamine and adenosine 3',5'-cyclic monophosphate-regulated phosphoprotein, Mr 32000 (DARPP-32), is overexpressed during gastric carcinogenesis. Gastric tumors can become resistant to gefitinib, an inhibitor of the epidermal growth factor receptor (EGFR). We investigated the role of DARPP-32 in gastric tumor resistance to gefitinib.

Methods: Cell survival was determined by clonogenic survival and ATP-Glo Viability Assays. Apoptosis was assessed by Annexin-V and immunoblot analyses. The association between DARPP-32 and EGFR was evaluated by immunofluorescence and co-immunoprecipitation assays. Findings were validated in mice with gastric xenograft tumors. DARPP-32 expression was reduced using small hairpin RNAs in the human gastric cancer cell lines SNU-16 and MKN-45 cells.

Results: Overexpression of DARPP-32 in MKN-28 cells, which do not normally express DARPP-32, blocked gefitinib-induced apoptosis and increased the drug's IC(50) 10-fold, compared to that of control cells (P < .01). Reduced expression of DARPP-32 in SNU-16 cells increased the sensitivity to gefitinib (P < .01). DARPP-32 activated phosphatidylinositol-3-kinase-AKT signaling, increased stability of the EGFR, and suppressed EGF- or gefitinib-induced degradation of the EGFR. DARPP-32 colocalized with EGFR on the cell membrane in a complex with EGFR and the EGF receptor ERBB3. DARPP-32-mediated resistance to gefitinib resulted from increased phosphorylation of and interaction between EGFR and ERBB3, which led to phosphorylation of AKT (at serine 473). Knockdown of DARPP-32 in gastric cancer cells reduced the mean size of tumors in mice and increased their response to gefitinib.

Conclusions: DARPP-32 promotes resistance of gastric cancer cells to gefitinib by promoting interaction between EGFR and ERBB3 and activating phosphatidylinositol-3-kinase-AKT signaling.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Adenocarcinoma / drug therapy
  • Adenocarcinoma / pathology
  • Animals
  • Antineoplastic Agents / pharmacology
  • Antineoplastic Agents / therapeutic use
  • Apoptosis / drug effects
  • Apoptosis / physiology
  • Cell Line, Tumor
  • Disease Models, Animal
  • Dopamine and cAMP-Regulated Phosphoprotein 32 / metabolism*
  • Drug Resistance, Neoplasm*
  • ErbB Receptors / metabolism*
  • Female
  • Gefitinib
  • Humans
  • Mice
  • Mice, Nude
  • Phosphatidylinositol 3-Kinases / metabolism
  • Proto-Oncogene Proteins c-akt / metabolism
  • Quinazolines / pharmacology
  • Quinazolines / therapeutic use*
  • Receptor, ErbB-3 / metabolism*
  • Signal Transduction / drug effects
  • Signal Transduction / physiology
  • Stomach Neoplasms / drug therapy*
  • Stomach Neoplasms / pathology


  • Antineoplastic Agents
  • Dopamine and cAMP-Regulated Phosphoprotein 32
  • PPP1R1B protein, human
  • Ppp1r1b protein, mouse
  • Quinazolines
  • Phosphatidylinositol 3-Kinases
  • ErbB Receptors
  • Receptor, ErbB-3
  • Proto-Oncogene Proteins c-akt
  • Gefitinib