HER2/neu uses Akt to suppress retinoic acid response element binding activity in MDA-MB-453 breast cancer cells.
We previously demonstrated that HER2/neu prevents all trans-retinoic acid (ATRA) from inducing growth inhibition in MDA-MB-453 breast cancer cells. For ATRA to induce growth inhibition, it needs to bind to retinoic acid receptors and modulate gene transcription via retinoic acid response elements (RAREs). We hypothesized that HER2/neu suppresses RARE binding activity to prevent ATRA from inducing growth arrest in breast cancer cells. Electrophoretic mobility shift assays showed that when HER2/neu was inhibited by the trastuzumab antibody, RARE binding activity increased, indicating that HER2/neu suppresses RARE binding. Since trastuzumab also decreased Akt activity, we determined whether Akt regulates RARE binding activity. Compared to parental MDA-MB-453 cells, MDA-MB-453 cells transfected with a dominant negative Akt mutant (MDA-MB-453/DN-Akt) had higher RARE binding activity. However, trastuzumab did not further increase RARE binding activity in MDA-MB-453/DN-Akt cells. These data indicate that HER2/neu predominantly uses Akt to suppress RARE binding activity, which may be one mechanism by which HER2/neu induces ATRA resistance in breast cancer cells.
Siwak
Doris R
DR
Department of Bioimmunotherapy, Section of Immunobiology and Drug Carriers, The University of Texas M.D. Anderson Cancer Center, Houston, TX 77030, USA.
Mendoza-Gamboa
Edgar
E
Tari
Ana M
AM
D000911:Antibodies, Monoclonal / Q000494:pharmacology; D061067:Antibodies, Monoclonal, Humanized; D015153:Blotting, Western; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism; D015536:Down-Regulation; D005799:Genes, Dominant; D006801:Humans; D008081:Liposomes / Q000378:metabolism; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D011485:Protein Binding; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism*; D020218:Response Elements; D015398:Signal Transduction; D014162:Transfection; D000068878:Trastuzumab; D014212:Tretinoin / Q000378:metabolism*
D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D008081:Liposomes; D016376:Oligonucleotides, Antisense; D019869:Phosphatidylinositol 3-Kinases; D018719:Erb-b2 Receptor Tyrosine Kinases; D000068878:Trastuzumab; D014212:Tretinoin