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amplifi cation of HER2 in breast-cancer cells is associated with better clinical
responsiveness to anthracycline-containing chemotherapy regimen when compared
with the regimen of cyclophosphamide, methotrexate, and fl uorouracil (Pritchard
et al. 2006 ). Benefi t of anti-HER2 therapies demonstrated in clinical trials indicates
that HER2 is, to date, one of the most promising molecules for targeted therapy.
Nevertheless, since tumor cells utilizing alternative growth signaling pathways
through transmembrane receptors as well as intracellular signaling transduction
molecules can bypass HER2 blockade, a future ambitious aim is the successful
combination of anti-HER2 strategies with drugs directed to molecules that contrib-
ute to anti-HER2 resistance (Tagliabue et al. 2010 ).
Various methods that have been used to analyze the HER2 status of a tumor
include the following:
- Immunohistochemistry: protein expression levels
- ELISA: shedding of HER2 receptor
- FISH: HER2 gene amplifi cation
- Quantitative PCR: HER2 gene amplifi cation
- Quantitative RT-PCR: mRNA expression level
In practice, immunohistochemistry is the most frequently used method. However,
it is recommended that all specimens with weakly positive immunohistochemistry
(+2 Hercep Test result) be evaluated by FISH for HER2/neu gene amplifi cation. The
results of both assays should be considered before making a decision to recommend
anti-HER2 therapy. The LightCycler™ PCR assay (Roche) has now been developed
specifi cally to assess HER2 gene amplifi cation. The advantages are:
- It is accurate for determining HER2 gene amplifi cation and correlates well with
FISH; 85 % sensitivity and 95 % specifi city. - It is a rapid screening method with up to 30 samples per run
- The kit uses a reference sequence on chromosome 17 so that a correct data inter-
pretation should be possible in polysomic cases
One limitation of LightCycler PCR is that it does not give histopathological
assignment. Microdissection may be required in critical cases. The combined use of
laser capture microdissection, DNA microarray, and real-time quantitative PCR
technologies now provides a unique opportunity to elucidate the in vivo genetic
events that underlie the initiation and progression of human breast cancer. The
clinical utility of the serum test as a prognostic indicator has not yet been fully
established but is under investigation.
Current methods for checking HER2 are problematic because of issues with
intra- and inter-laboratory reproducibility and pre-analytic variables, such as fi xa-
tion time. In addition, the commonly used HER2/chromosome 17 ratio presumes
that chromosome 17 polysomy is present when the centromere is amplifi ed, even
though analysis of the rest of the chromosome is not included in the assay. In one
study, 97 frozen samples of invasive lobular and invasive ductal carcinoma, with
known ICH and FISH results for HER2, were analyzed by aCGH to a commercially
available bacterial artifi cial chromosome whole-genome array containing 99 probes
10 Personalized Therapy of Cancer