Potential of endogenous estrogen receptor beta to influence the selective ER modulator ERbeta complex.

The ratio of estrogen receptor beta (ERbeta) to ERalpha can alter the estrogen-like properties of tamoxifen. Transient transfection of ERbeta cDNA into cells can decrease the estrogen-like properties of the ERalpha:tamoxifen complex, whereas an increase in the amount of ERbeta is associated with tamoxifen-resistant breast cancer. We have addressed each of these hypotheses by examining well characterized laboratory models. We determined whether changes in endogenous ERbeta are responsible for the estrogen-like or antiestrogenic properties of tamoxifen or raloxifene in MDA-MB-231 cells transfected with cDNAs for ERalpha or mutants D351G, D351Y. We found that the amount of ERbeta mRNA in separate, stable transfectants of mutant ERalpha cDNA was always < 2% of ERalpha. Since at least a 50:50 mixture of ERalpha:ERbeta is needed to silence the tamoxifen:ERalpha complex, we conclude that insufficient ERbeta mRNA is available for selective ER modulation in stable transfectants of D351G and D351Y ERalpha. Similarly, to test the hypothesis that ERbeta is up-regulated and plays an important role during the development of tamoxifen-stimulated tumor growth, we quantitatively analyzed ERbeta and ERalpha mRNA in tamoxifen-naïve (MCF-7:E2, ECC1:E2) and tamoxifen-stimulated tumors (MCF-7:TAM, EnCa 101:TAM). We found that ERbeta mRNA levels were not significantly elevated in tamoxifen-stimulated tumors and the ERalpha mRNA remained over 99% out of all ER species for all the tumors tested. The same results were also obtained when mRNA levels of ERbeta and ERalpha in a series of tamoxifen-naïve and tamoxifen-resistant breast cancer was analyzed. We conclude that endogenous ERbeta may not play a dominant role in the modulation of the tamoxifen ERalpha complex, or in the development of tamoxifen-stimulated resistant tumor growth.

Expression of androgen receptor and prostate-specific antigen in male breast carcinoma.

BACKGROUND: The androgen-regulated proteins prostate-specific antigen (PSA) and prostate-specific acid phosphatase (PSAP) are present in high concentrations in normal prostate and prostatic cancer and are considered to be tissue-specific to prostate. These markers are commonly used to diagnose metastatic prostate carcinoma at various sites including the male breast. However, expression of these two proteins in tumors arising in tissues regulated by androgens such as male breast carcinoma has not been thoroughly evaluated. METHODS: In this study we analyzed the expression of PSA, PSAP and androgen receptor (AR) by immunohistochemistry in 26 cases of male breast carcinomas and correlated these with the expression of other prognostic markers. RESULTS: AR, PSA and PSAP expression was observed in 81%, 23% and 0% of carcinomas, respectively. Combined expression of AR and PSA was observed in only four tumors. CONCLUSION: Although the biological significance of PSA expression in male breast carcinomas is not clear, caution should be exercised when it is used as a diagnostic marker of metastatic prostate carcinoma.

The use of TMA for interlaboratory validation of FISH testing for detection of HER2 gene amplification in breast cancer.

HER2 fluorescence in situ hybridization (FISH) testing for breast cancer is largely limited to academic centers and commercial laboratories. As testing demands increase, methods for rapid and cost-effective technical validation and quality assessment will be required. Tissue microarray (TMA), a technique for high-throughput biomarker evaluation, could help facilitate these needs. Our objective was to assess the usefulness of TMA technology for validation of HER2 FISH testing. Two TMA blocks containing paired cores from 41 breast cancers were constructed. HER2 FISH was performed in parallel at two institutions and the results compared. One institution, with considerable HER2 FISH experience, served as the reference laboratory. HER2 chromogenic in situ hybridization (CISH) and immunohistochemistry (IHC) were compared to the FISH results. For positive and negative results, the concordance rate between laboratories was 100%. Using kappa statistical analysis to determine interobserver agreement, HER2 to chromosome 17 gene copy ratios showed strong agreement between laboratories with kappa = 0.85 (perfect agreement = 1.0). Four cases displaying low-level amplification by CISH contained chromosome 17 polysomy and gene copy ratios of <2.0 by FISH. Good concordance was observed between HER2 IHC and in situ hybridization testing. TMA is a robust and effective method for the technical validation of HER2 FISH testing and should be considered for use by quality assessment programs.