Immunohistochemical expression of internal and external ErbB-2 domains in invasive breast cancer

The effects of antibody clone and pretreatment method on the results of HER2 immunostaining in cytologic samples of metastatic breast cancer: A query and a review of the literature

The standardization and use of heat-induced epitope retrieval (HIER) is particularly important with immunohistochemical markers that direct the course of cancer treatment, such as Herceptin therapy. Increasingly, many laboratories are performing immunohistochemical analysis using various antibodies and methodologies for HER2/neu. We attempted to determine the effects of antibody clone and pretreatment methods on the interpretation of HER-2/neu staining in cytologic samples. Cell block sections from 54 cases of metastatic breast cancer (24 FNAs, 30 effusions) were analyzed for HER2 expression using antibodies to CB-11, TAB250, and A0485. Antibodies were analyzed with and without HIER. One pathologist using the FDA-approved scoring system for the HercepTest reviewed all slides in a blinded fashion. Five of fifty-four cases (9%) using CB-11 showed a significant increase in HER2 immunoreactivity using HIER (i.e. from 0/1+ to 2-3+). However, in twenty-nine of fifty-four cases (54%), the cytoplasmic background was significantly higher after HIER. With the A0485 antibody, two of fifty four cases (4%) showed a significant increase in immunoreactivity using HIER, while seventeen of fifty-four cases (31%) exhibited only more pronounced cytoplasmic staining. HIER pretreatment did not increase HER2 staining in any TAB250 stained sample, rather four of fifty-four cases (7%) showed a significant decrease in staining with HIER. We conclude that HIER may enhance membrane staining with the CB-11 and A0485 antibodies, but also increases cytoplasmic background. Loss of antigenicity is seen when HIER is used with TAB250.

HER2 evaluation using the novel rabbit monoclonal antibody SP3 and CISH in tissue microarrays of invasive breast carcinomas

BACKGROUND

Laboratory methods for HER2 assessment currently include immunohistochemical (IHC) methods (measuring protein overexpression) and fluorescence in situ hybridisation (FISH) (measuring gene amplification). The measure of HER2 protein by IHC is usually assessed by the mouse monoclonal antibody CB11, and polyclonal antibodies (Herceptest) directed against the internal portion of the receptor. Recently, chromogenic in situ hybridisation (CISH), in which HER2 is detected by a peroxidase reaction and the gene amplification can be determined by regular bright-field microscopy, has emerged as an alternative to FISH.

AIMS

To evaluate the status of HER2 in tissue microarrays (TMAs) of invasive breast cancer using the novel rabbit monoclonal antibody SP3 directed against the external portion of HER2, and correlate the results with CB11 and CISH.

METHODS

IHC was performed with two antibodies (CB11 and SP3) and CISH for HER2 in 10 TMA blocks with 190 formalin-fixed paraffin-embedded cases of invasive breast carcinomas.

RESULTS

The correlation between SP3 and CB11 was significant (p<0.001) with an agreement rate of 86.9%. When the staining pattern of the two antibodies was compared, the majority of SP3 immunostainings were assessed more easily, with a strong complete membrane staining pattern without non-specific cytoplasmic staining. There was a good correlation between SP3 and CISH (p<0.001). 23/24 SP3 3+ cases showed gene amplification, 97.3% of the cases without gene amplification were SP3 negative, and 6/7 SP3 2+ were amplified.

CONCLUSION

The high level of agreement between SP3, a monoclonal antibody that recognises the extracellular domain of the HER2 receptor, and CB11 and CISH, shows that this novel antibody is a reliable candidate to evaluate the expression of HER2 in breast cancer.

Immunochemical analysis of protein expression in breast epithelial cells transformed by estrogens and high linear energy transfer (LET) radiation

Breast cancer is a complex disease involving numerous genetic aberrations. Immunochemical analysis of protein expression is presented in a human breast epithelial cell line neoplastically transformed by high linear energy transfer (LET) alpha particle radiation in the presence of 17beta estradiol (E) and in the parental human breast epithelial cell line (MCF-10F) which served as a non-tumorigenic control. The aim of this work was to determine the levels of mRNA and protein expression in control and transformed cells at various stages of the neoplastic process. The levels of mRNA and protein expression of PCNA, c-fos, JNK2 and Fra-1 were increased in the transformed cell line compared to the levels in non-tumorigenic control cells. The transforming factor Rho A was significantly increased only in the tumor cell line. Furthermore, the levels of mRNA and protein expression of ErbB2 were significantly increased in the transformed cell line and in tumor cells derived from the transformed cells after injecting them into nude mice. A decrease in RbA/p48 protein expression and mRNA levels was observed in cells treated with double doses of alpha particle radiation in the presence of estrogen, regardless of tumorigenicity. Such expression was lower than that in the control untreated MCF-10F cells. In summary, these studies show that estrogen and high LET-radiation induce changes in oncoprotein expression and mRNA levels of human breast cell lines. These changes are indicative of a cascade of events that characterize the process of cell transformation in breast cancer. These results provide evidence that multiple steps with consecutive changes are involved when normal cells become tumorigenic cells as a result of alpha particle irradiation and estrogen treatments.

A modified Trastuzumab antibody for the immunohistochemical detection of HER-2 overexpression in breast cancer

The immunohistochemical determination of HER-2 to identify patients with advanced breast cancer candidates for Trastuzumab treatment proved neither accurate nor fully reliable, possibly because none of the current reagents detects the specific antigenic site target of Trastuzumab. To circumvent this problem, we conjugated the NH₂ groups of Trastuzumab with biotin, and the compound obtained, designated BiotHER, was added directly to tissue sections. Biotin-labelling was revealed with horseradish peroxidase-conjugated streptavidin. Specificity and sensitivity of BiotHER immunostaining with respect to HER-2 amplification were tested on 164 breast carcinoma samples. BiotHER staining was detected on the tumour cell membrane of 12% of all specimens and in 49% specimens with gene amplification, while absent in nonamplified tumours. Predictivity of BiotHER status with respect to the clinical outcome was analysed in 54 patients with HER-2 amplified advanced breast cancer treated with Trastuzumab plus chemotherapy. BiotHER staining, detected in 50% of tumours with HER-2 amplification, was an independent predictor of clinical outcome. In fact, BiotHER positivity was independently associated with increased likelihood of tumour response and reduced risk of tumour progression and death. Biotinylated Trastuzumab can thus be used for immunohistochemical detection of HER-2 overexpression in breast cancer, and has the potential to identify patients likely to benefit from Trastuzumab treatment.

Which breast carcinomas need HER-2/neu gene study after immunohistochemical analysis? Results of combined use of antibodies against different c-erbB2 protein domains

AIMS

Evaluation of HER2 gene amplification in breast cancers is a compelling, routine procedure. The aim of this work was to evaluate which breast carcinomas would really benefit from HER-2/neu gene analysis.

METHODS AND RESULTS

We studied 130 invasive breast carcinomas by immunohistochemistry (IHC) using CB11 and TAB250 MAbs directed against different domains of the c-erbB2 molecule. From this series, we selected 106 cases (32 G1, 36 G2, and 38 G3) in which HER-2/neu gene analysis, using chromogenic in-situ hybridization (CISH), was successful. IHC results were scored using the FDA approved system with three score values: 0/1+ (negative), 2+, 3+ (positive). In addition, we developed a double scoring system with six score values (0/1+ 2+ negative, 3+, 4+, 5+, 6+ positive) obtained by summating the individual scoring values obtained with each MAb. All double scoring negative cases were non-amplified (100% sensitivity), whereas all cases scored 6+ were amplified. Double scoring values and CISH results were then correlated with grade and histological type. G1 ductal carcinomas and carcinomas of lobular and of special histological type did not show HER-2/neu amplification even in the presence of protein over-expression.

CONCLUSIONS

The combined results of IHC analysis (double scoring values) obtained using MAbs directed against different c-erbB2 domains correctly indicates the HER-2/neu gene status in 57.5% of cases. In addition, simple morphological features such as low grade and special histological type are good predictors of the non-amplification of the HER-2/neu gene in breast carcinoma.