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RESEARCH PRODUCT
Trastuzumab therapy vs tetracycline controlled ERBB2 downregulation: influence on tumour development in an ERBB2-dependent mouse tumour model
Ilka B. SchifferLars-christian HornGerd A. MüllerJan G. HengstlerChristian WilhelmS GebhardM. BrulportDirk PrawittJoachim MössnerK UhlemannMatthias HermesF LupatschE LauschW. SchormannC AllgaierM WeishauptA BauerAnika SchumannKurt EngelandM Schmidtsubject
MaleCancer ResearchReceptor ErbB-2AKT1AKT2ApoptosisMiceTrastuzumabPKBskin and connective tissue diseasesERBB2Mitogen-Activated Protein Kinase 3biologyERK1/2herceptinAntibodies MonoclonalCytochromes cImmunohistochemistrynude miceGene Expression Regulation NeoplasticOncologyTetracyclinesKi-67Ki-67Femalemedicine.drugmedicine.medical_specialtyBlotting WesternDown-RegulationMice NudeAntineoplastic AgentsProtein Serine-Threonine KinasesAntibodies Monoclonal Humanizedresistance3-Phosphoinositide-Dependent Protein Kinasesbreast cancerDownregulation and upregulationresponse to therapyInternal medicineHER2medicineAnimalsRNA Messengercytochrome c releaseProtein kinase Bneoplasmstumour developmentCell Proliferationhumanised monoclonal antibodyAktCancerMammary Neoplasms ExperimentalTrastuzumabmedicine.diseaseEndocrinologyKi-67 AntigenApoptosisDrug Resistance Neoplasmbiology.proteinCancer researchreceptor tyrosine kinaseTranslational TherapeuticsProto-Oncogene Proteins c-aktdescription
Trastuzumab (Herceptin) has improved therapy of breast cancer. Only patients overexpressing ERBB2 are treated with trastuzumab, whereas its use in tumours without ERBB2 expression is useless. This led to the concept that the subgroup of trastuzumab-sensitive tumours is ‘ERBB2-dependent', meaning that ERBB2 signalling is indispensable for growth of these tumours. We used a mouse model that allows anhydrotetracycline (ATc)-controlled downregulation of ERBB2 in tumour tissue. ERBB2 mRNA and protein expression were downregulated below detection limit leading to a macroscopically complete tumour remission within 14 days. Tumour remission was accompanied by a strong decrease in proliferation, a moderate increase in apoptosis, as well as dephosphorylation of ERK1/2 and AKT/PKB. These data clearly indicate ERBB2 dependence. Therefore, a high sensitivity to trastuzumab may be suspected. Surprisingly, trastuzumab caused a much weaker effect compared to ATc-induced ERBB2 downregulation, although a decrease in ERBB2 membrane localisation was induced. Only a slight decrease in proliferation and a weak transient increase in apoptosis were observed. Interestingly, tumours responded to trastuzumab by a sharp fivefold increase in phosphorylated AKT/PKB as well as a 3.5- and 5.3-fold increase in AKT1 and AKT2 mRNA levels, respectively. In conclusion, ‘ERBB2 dependence' is not sufficient to define trastuzumab-responsive tumours. The suboptimal effect of trastuzumab compared to the maximally possible effect induced by ATc demonstrates a high potential for improved ERBB2 blocking therapies.
year | journal | country | edition | language |
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2008-04-01 | British Journal of Cancer |