title: PTEN loss is not associated with trastuzumab resistance in metastatic breast cancer.
abstract: OBJECTIVE
  Although the clinical benefits of trastuzumab are well known, intrinsic or acquired resistance is a commonly encountered clinical condition. A potential resistance mechanism is aberrant downstream signal transmission due to loss of phosphatase and tensine homologue (PTEN). This study investigated the relationship between trastuzumab response and loss of PTEN in metastatic breast cancer patients.
  
  
  METHODS
  Patients with histologically confirmed human epidermal growth factor receptor 2 (HER2) positive metastatic breast cancer, who were treated with trastuzumab were enrolled into the study. PTEN expression was immunohistochemically evaluated.
  
  
  RESULTS
  The patient median age was 50 years. Of 38 patients, 6 (15.8%) showed PTEN loss. No statistically significant difference was found between trastuzumab response, overall survival (OS) and progression-free survival (PFS) and PTEN loss (p=0.538).
  
  
  CONCLUSIONS
  The activation of phosphatidylinositol 3-kinase (PI3K) pathway resulting from PTEN loss was not found to be correlated with trastuzumab response and survival. PTEN loss should not lead to exclusion of patients from the potential to benefit from trastuzumab administration.
authors.affiliation: Department of Medical Oncology, Sanliurfa State Hospital, Sanliurfa, Turkey.
authors.forename: Muharrem
authors.initials: M
authors.lastname: Kocar
authors.forename: Emine
authors.initials: E
authors.lastname: Bozkurtlar
authors.forename: Ferhat
authors.initials: F
authors.lastname: Telli
authors.forename: Nazim
authors.initials: N
authors.lastname: Serdar Turhal
authors.forename: Handan
authors.initials: H
authors.lastname: Kaya
authors.forename: Hande
authors.initials: H
authors.lastname: Kocar
authors.forename: Fulden
authors.initials: F
authors.lastname: Yumuk
mesh_terms: D061067:Antibodies, Monoclonal, Humanized / Q000494:pharmacology*; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000235:genetics; D002352:Carrier Proteins / Q000235:genetics*; D016207:Cytokines / Q000235:genetics*; D018572:Disease-Free Survival; D006801:Humans; D008875:Middle Aged; D019869:Phosphatidylinositol 3-Kinases; D000068878:Trastuzumab / Q000494:pharmacology*
chemical_list: D061067:Antibodies, Monoclonal, Humanized; D002352:Carrier Proteins; D016207:Cytokines; C066845:pleiotrophin; D019869:Phosphatidylinositol 3-Kinases; D000068878:Trastuzumab