A differential PCR assay for the detection of c-erbB 2 amplification used in a prospective study of breast cancer

Ultrasound targeted apoptosis imaging in monitoring early tumor response of trastuzumab in a murine tumor xenograft model of her-2-positive breast cancer(1.)

OBJECTIVE

Our study aimed to monitor the trastuzumab therapy response of murine tumor xenograft model with human epidermal growth factor receptor 2 (Her-2)-positive breast cancer using ultrasound targeted apoptosis imaging.

METHODS

We prepared targeted apoptosis ultrasound probes by nanobubble (NB) binding with Annexin V. In vitro, we investigated the binding rate of NB-Annexin V with breast cancer apoptotic cells after the trastuzumab treatment. In vivo, tumor-bearing mice underwent ultrasound targeted imaging over 7 days. After imaging was completed, the tumors were excised to determine Her-2 and caspase-3 expression by immunohistochemistry (IHC). The correlation between parameters of imaging and histologic results was then analyzed.

RESULTS

For seeking the ability of targeted NB binding with apoptotic tumor cells (Her-2 positive), we found that binding rate in the treatment group was higher than that of the control group in vitro (P = .001). There were no differences of tumor sizes in all groups over the treatment process in vivo (P = .98). However, when using ultrasound imaging to visualize tumors by targeted NB in vivo, we observed that the mean and peak intensities from NBs gradually increased in the treatment group after trastuzumab therapy (P = .001). Furthermore, these two parameters were significantly associated with caspase-3 expression of tumor excised samples (P = .0001).

CONCLUSION

Ultrasound targeted apoptosis imaging can be a non-invasive technique to evaluate the early breast tumor response to trastuzumab therapy.

Current Diagnostic Methods of HER-2/neu Detection in Breast Cancer With Special Regard to Real-Time PCR

In this study we compare different diagnostic methods to measure HER-2/neu gene amplification in breast cancer with special regard to real-time polymerase chain reaction. Fifty specimens of breast cancer were analyzed, and the use of laser-assisted microdissection prior to PCR was investigated. A total of 38 of 50 cases showed HER-2/neu overexpression in immunohistochemistry. In the 2+ scored group, 2 of 23 cases turned out to be amplified after FISH analysis and 14 of 15 cases in the 3+ group were amplified. Of the 16 amplified cases, 3 initially were measured as nonamplified by real-time PCR but showed amplification after laser capture microdissection. One case showed amplification by PCR but turned out to have only one copy of chromosome 17 by FISH. All 0 or 1+ scored cases were measured as nonamplified both by FISH and PCR. Initial concordance rate between FISH and PCR was 92% and could be increased to 98% using laser-assisted microdissection. FISH and PCR showed high diagnostic accuracy and concordance while immunohistochemistry overestimates amplification within the 2+ scored group. Therefore, either FISH or PCR should be applied in cases scored 2+ by immunohistochemistry. Diagnostic accuracy of PCR can be increased using laser-assisted microdissection.

The clinical evaluation of HER-2 status: which test to use?

Accurate determination of the status of the type I receptor tyrosine kinase HER-2 in breast carcinomas provides significant insight into patient prognosis and may also inform selection of chemotherapeutic and hormonal treatments. At present, however, the single most important application of HER-2 testing is in the selection of patients for treatment with targeted therapies such as Herceptin. Although, based on current literature, fluorescence in situ hybridization (FISH) detection of HER-2 gene amplification may provide more accurate information in this context, this method is not yet widely available. Therefore, screening by immunohistochemistry (IHC) for HER-2 protein, backed by rigorous quality controls and FISH testing of equivocal cases with intermediate staining intensity, remains the current practice. In laboratories with highly standardized testing and quality assurance procedures, this protocol appears highly effective. Improvements in fixation procedures, standardization of antibodies, and use of automated image analysis may all increase the precision of IHC testing. However, on the basis of current data, there is a case to be made for the wider implementation of FISH testing to determine HER-2 status in breast cancer.

p185HER2 overexpression in human breast cancer using molecular and immunohistochemical methods

With the successful clinical trials of the engineered antibody Herceptin (in advanced-stage breast cancer) and adriamycin-based chemotherapy regimens (in the adjuvant setting), the need to detect p185HER2 overexpression or associated amplification of the coding gene HER2 in breast cancer patients is escalating. Twenty to 30% of breast carcinomas have overexpression of p185HER2. This condition correlates with poor patient prognosis and predicts response to chemotherapy in lymph node-positive patients. In this study we compare quantitation of p185HER2 in breast cancer at the gene and protein levels using differential polymerase chain reaction (PCR) and immunohistochemistry, respectively. To assign HER2 gene copy numbers, a calibration curve was constructed using normal breast epithelia and breast carcinoma cell lines having known dosages of amplified HER2. We found corresponding molecular and immunohistochemical results in 85% of the 13 paraffin-embedded breast carcinoma cases examined. Two cases were found to have minimum gene amplification but marked p185HER2 overexpression, suggesting an alternative mechanism to overexpression such as transcriptional activation. Although the differential PCR assay exhibits saturation approaching 20 HER2 gene copies, this may not be clinically significant because the immunohistochemical assay also appears to saturate in this gene copy number range.