Amplification of the BP1 homeobox gene in breast cancer.
The homeobox gene BP1 is expressed in over 80% of breast cancers and is associated with tumor progression and invasion. However, the mechanism of BP1 activation in these tumors remains unknown. Therefore our aim in this study is to assess the amplification status of the BP1 gene in breast cancer and to determine whether BP1 protein expression is caused by gene amplification in these tumors. BP1 amplification and expression were assessed in 36 samples. Twenty primary breast tumors (PBT) and 14 sentinel lymph node (SLN) metastases were analyzed using fluorescence in situ hybridization (FISH) and immunohistochemistry (IHC), respectively. Because of the close proximity of BP1 and HER2/NEU genes on 17q, correlation between their amplification/expression was also investigated. Increased BP1 copy number was observed in 33% of the cases, with a frequency of 36% and 29% in the PBT and SLN metastasis, respectively. BP1 protein was expressed in 91% of the samples: in all of the PBT with increased BP1 copy number and 65% of PBT with normal copy number. HER2/NEU amplification was detected in 22% of the cases. Concordance between BP1 and HER2/NEU copy numbers was found in 68% of the PBT and 90% of the SLN metastasis. In conclusion, we demonstrated that the BP1 homeobox gene is amplified in breast cancer, both in PBT and SLN metastasis, with a significant correlation with HER2/NEU amplification. Considering that BP1 expression was observed in cases with both increased and normal BP1 copy number, we conclude that other mechanisms in addition to gene amplification play a role in BP1 protein expression.
Cavalli
Luciane R
LR
Department of Oncology, Lombardi Comprehensive Cancer Center, Georgetown University, 3800 Reservoir Rd, Room S165A - LL Lombardi Building, Washington, DC 20007, USA. lrc@georgetown.edu
Man
Yan-Gao
YG
Schwartz
Arnold M
AM
Rone
Janice D
JD
Zhang
Ying
Y
Urban
Cicero A
CA
Lima
Rubens S
RS
Haddad
Bassem R
BR
Berg
Patricia E
PE
D001943:Breast Neoplasms / Q000235:genetics* / Q000473:pathology; D005260:Female; D005784:Gene Amplification; D015972:Gene Expression Regulation, Neoplastic; D018398:Homeodomain Proteins / Q000235:genetics*; D006801:Humans; D007150:Immunohistochemistry; D017404:In Situ Hybridization, Fluorescence; D008207:Lymphatic Metastasis; D009362:Neoplasm Metastasis / Q000235:genetics / Q000473:pathology; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000235:genetics; D021701:Sentinel Lymph Node Biopsy; D014157:Transcription Factors / Q000235:genetics*
D018398:Homeodomain Proteins; D018719:Erb-b2 Receptor Tyrosine Kinases; D014157:Transcription Factors; C105304:DLX4 protein, human