Expression of HER2 and the coamplified genes GRB7 and MLN64 in human breast cancer: quantitative real-time reverse transcription-PCR as a diagnostic alternative to immunohistochemistry and fluorescence in situ hybridization.
OBJECTIVE
Accurate testing of HER2 is centrally important for breast cancer therapy and prognosis. Immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH) are current standard testing methods. As a potential alternative for assessment of HER2, we explored quantitative real-time reverse transcription-PCR (RT-PCR), a fast and inexpensive method yielding quantitative results insensitive to interobserver variability and amenable to standardized scoring.


METHODS
We assessed HER2 status at the DNA, mRNA, and protein levels with FISH, quantitative RT-PCR, and IHC in 136 tumor samples from 85 breast cancer patients. Expression of GRB7, MLN64, and p21, genes coregulated with HER2, was also quantified with quantitative RT-PCR and correlated with the overall survival (OS) and disease-free survival (DFS) individually and in combination with HER2.


RESULTS
Twenty-nine percent and 19% of the patients scored HER2 positive with IHC and quantitative RT-PCR, respectively. In 18 of 19 cases, HER2 statuses in tumors and lymph node metastases were identical. HER2 status significantly correlated with DFS when determined by IHC (P < 0.01), quantitative RT-PCR (P < 0.003), but not with FISH (P = 0.09). The combination of HER2 with MLN64, but not with GRB7 or p21, enhanced the prognostic power for the DFS (P < 0.00005) and OS (P < 0.0008).


CONCLUSIONS
Quantitative RT-PCR seems to be clinically as useful in the assessment of HER2 status as IHC and FISH, yielding comparable correlations of HER2 status with the OS and DFS. Thus, quantitative RT-PCR analysis of HER2 or HER2 plus MLN64 is a promising complement or alternative to current methods for HER2 testing, particularly in laboratories lacking FISH or IHC technology.
Vinatzer
Ursula
U
Department of Obstetrics and Gynecology, Medical University of Vienna, and Boehringer Ingelheim Austria, Vienna, Austria.
Dampier
Brigitta
B
Streubel
Berthold
B
Pacher
Margit
M
Seewald
Michael J
MJ
Stratowa
Christian
C
Kaserer
Klaus
K
Schreiber
Martin
M
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001943:Breast Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D018270:Carcinoma, Ductal, Breast / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D018275:Carcinoma, Lobular / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000235:genetics / Q000378:metabolism; D004273:DNA, Neoplasm / Q000032:analysis; D005260:Female; D051382:GRB7 Adaptor Protein / Q000235:genetics* / Q000378:metabolism; D005784:Gene Amplification; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007124:Immunoenzyme Techniques; D017404:In Situ Hybridization, Fluorescence; D008207:Lymphatic Metastasis / Q000473:pathology; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism; D008875:Middle Aged; D009367:Neoplasm Staging; D011379:Prognosis; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000235:genetics* / Q000378:metabolism; D012189:Retrospective Studies; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015996:Survival Rate
D002352:Carrier Proteins; D050759:Cyclin-Dependent Kinase Inhibitor p21; D004273:DNA, Neoplasm; D051382:GRB7 Adaptor Protein; D008565:Membrane Proteins; D018719:Erb-b2 Receptor Tyrosine Kinases; C493956:CDKN1A protein, human; C495955:GRB7 protein, human; C105684:STARD3 protein, human