title: Tamoxifen resistance and CYP2D6 copy numbers in breast cancer patients.
abstract: BACKGROUND
  Breast cancer accounts about one million from total annual ten million new diagnosed cases of neoplasia worldwide and is the main cause of death due to cancer in women. Tamoxifen is the most popular selective estrogen receptor modulator used in anti estrogen treatments. Tamoxifen must be converted into its metabolite endoxifen for biologic effects; this conversion process is catalysed by highly polymorphic cytochrome P450 2D6 (CYP2D6). This study surveyed copy number variation of the CYP2D6 gene and its possible correlation with Tamoxifen resistance in breast cancer patients.
  
  
  METHODS
  This case control study was performed on samples taken from 79 patients with breast cancer who used tamoxifen in Yazd and Tehran Cities, Iran. Real time reactions were conducted for 10 healthy samples using the comparative Ct (Cycles threshold) method, each pair of genes being compared and samples with ratios around 1 were taken as control samples. Proliferation reactions were done by Real-Time PCR ABI Prism 7500. All registered data were transformed into SPSS 15 program and analyzed.
  
  
  RESULTS
  Efficiency of PCR for both CYP2D6 and ALB genes was 100%. From all 23 drug resistant patients 21.7% had one copy, 47.8% two copies and 30.4% had three copies. Also from all 56 drug sensitive patients, 26.8% had one copy, 51.8% two copies and 21.4% had three copies. The percentage of patients with one and two copies was similar between two groups but patients with three copies were more likely to belong to the drug resistant group more. Odd ratios for one and two copies were 0.759 and 0.853 respectively, indicating possible protective effects while that for three copies was 1.604.
  
  
  CONCLUSIONS
  Based on our study there is no significant link between CYP2D6 gene copy numbers and tamoxifen resistance in women with breast cancer. But more studies considering other influencing factors appear warranted.
authors: Science and Research Tehran Branch of Islamic Azad University, Tehran Iran. pars.pajooh.group@gmail.com
authors: Sahar
authors: S
authors: Motamedi
authors: Keivan
authors: K
authors: Majidzadeh
authors: Mahta
authors: M
authors: Mazaheri
authors: Robab
authors: R
authors: Anbiaie
authors: Seyed Mohammad Reza
authors: SM
authors: Mortazavizadeh
authors: Rezvan
authors: R
authors: Esmaeili
mesh_terms: D018931:Antineoplastic Agents, Hormonal / Q000627:therapeutic use; D001943:Breast Neoplasms / Q000188:drug therapy; D016022:Case-Control Studies; D019389:Cytochrome P-450 CYP2D6 / Q000235:genetics; D056915:DNA Copy Number Variations; D005838:Genotype; D006801:Humans; D007492:Iran; D013629:Tamoxifen / Q000627:therapeutic use
chemical_list: D018931:Antineoplastic Agents, Hormonal; D013629:Tamoxifen; D019389:Cytochrome P-450 CYP2D6