Her-2/neu and breast cancer.

Breast cancer is the most common malignancy in women in the United States in the year 2000. The proto-oncogene Her-2/neu (c-erb-B2) has become an increasingly important prognostic and predictive factor in breast cancer. Overexpression/amplification of the Her-2/neu has been associated with a worse outcome in patients with breast cancer. Herceptin, a "humanized" murine monoclonal antibody directed against the extracellular domain of the Her-2/neu protein, is being used to treat breast cancer that overexpresses Her-2/neu. The status of Her-2/neu in the tumor has become a critical factor in the management strategy of a breast cancer patient. The objective of this article is to provide a comprehensive review of all aspects of Her-2/neu in breast cancer, including biology, prognostic and predictive value, targeted Herceptin therapy, and the laboratory testing of Her-2/neu.

Weekly trastuzumab and paclitaxel therapy for metastatic breast cancer with analysis of efficacy by HER2 immunophenotype and gene amplification.

PURPOSE: This phase II study evaluated weekly trastuzumab and paclitaxel therapy in women with HER2-normal and HER2-overexpressing metastatic breast cancer. Efficacy was correlated with immunohistochemical and fluorescent in situ hybridization (FISH) assay results. PATIENTS AND METHODS: Eligible patients had bidimensionally measurable metastatic breast cancer. Up to three prior chemotherapy regimens, including prior anthracycline and taxane therapy, were allowed. Trastuzumab 4 mg/kg and paclitaxel 90 mg/m2 were administered on week 1, with trastuzumab 2 mg/kg and paclitaxel 90 mg/m2 administered on subsequent weeks. HER2 status was evaluated using four different immunohistochemical assays and FISH. RESULTS: Patients received a median of 25 weekly infusions (range, one to 85 infusions). Median delivered paclitaxel dose-intensity was 82 mg/m2/wk (range, 52 to 90 mg/m2/wk). The intent-to-treat response rate for all 95 patients enrolled was 56.8% (95% confidence interval, 47% to 67%). A response rate of 61.4% (4.5% complete response, 56.8% partial response) was observed in 88 fully assessable patients. In patients with HER2-overexpressing tumors, overall response rates ranged from 67% to 81% compared with 41% to 46% in patients with HER2-normal expression (ranges reflect the different assay methods used to assess HER2 status). Differences in response rates between patients with HER2-overexpressing tumors and those with normal HER2 expression were statistically significant for all assay methods, with CB11 and TAB250 antibodies and FISH having the strongest significance. Therapy was generally well tolerated, although three patients had serious cardiac complications. CONCLUSION: Weekly trastuzumab and paclitaxel therapy is active in women with metastatic breast cancer. Therapy was relatively well tolerated; however, attention to cardiac function is necessary.

Sentinel lymph node biopsy: is it indicated in patients with high-risk ductal carcinoma-in-situ and ductal carcinoma-in-situ with microinvasion?

BACKGROUND: Axillary lymph node status is the strongest prognostic indicator of survival for women with breast cancer. The purpose of this study was to determine the incidence of sentinel node metastases in patients with high-risk ductal carcinoma-in-situ (DCIS) and DCIS with microinvasion (DCISM). METHODS: From November 1997 to November 1999, all patients who underwent sentinel node biopsy for high-risk DCIS (n = 76) or DCISM (n = 31) were enrolled prospectively in our database. Patients with DCIS were considered high risk and were selected for sentinel lymph node biopsy if there was concern that an invasive component would be identified in the specimen obtained during the definitive surgery. Patients underwent intraoperative mapping that used both blue dye and radionuclide. Excised sentinel nodes were serially sectioned and were examined by hematoxylin and eosin and by immunohistochemistry. RESULTS: Of 76 patients with high-risk DCIS, 9 (12%) had positive sentinel nodes; 7 of 9 patients were positive for micrometastases only. Of 31 patients with DCISM, 3 (10%) had positive sentinel nodes. 2 of 3 were positive for micrometastases only. Six of nine patients with DCIS and three of three with DCISM and positive sentinel nodes had completion axillary dissection; one patient with DCIS had an additional positive node detected by conventional histological analysis. CONCLUSIONS: This study documents a high incidence of lymph node micrometastases as detected by sentinel node biopsy in patients with high-risk DCIS and DCISM. Although the biological significance of breast cancer micrometastases remains unclear at this time, these findings suggest that sentinel node biopsy should be considered in patients with high-risk DCIS and DCISM.

A regulated RNA binding protein also possesses aconitase activity.

A clone for the iron-responsive element (IRE)-binding protein (IRE-BP) has been transfected and expressed in mouse fibroblasts. The IRE-BP gene product binds IREs with high affinity and specificity. Amino acid alignments reveal that the IRE-BP is 30% identical to mitochondrial aconitase. The 18 active site residues of mitochondrial aconitase are identical to those in the IRE-BP, suggesting that the IRE-BP may possess aconitase activity. After purification of native IRE-BP and immunoaffinity purification of transfected and expressed IRE-BP, we demonstrate that the purified IRE-BP has aconitase activity.

Cloning of the cDNA encoding an RNA regulatory protein--the human iron-responsive element-binding protein.

Iron-responsive elements (IREs) are stemloop structures found in the mRNAs encoding ferritin and the transferrin receptor. These elements participate in the iron-induced regulation of the translation of ferritin and the stability of the transferrin receptor mRNA. Regulation in both instances is mediated by binding of a cytosolic protein to the IREs. High-affinity binding is seen when cells are starved of iron and results in repression of ferritin translation and inhibition of transferrin receptor mRNA degradation. The IRE-binding protein (IRE-BP) has been identified as an approximately 90-kDa protein that has been purified by both affinity and conventional chromatography. In this report we use RNA affinity chromatography and two-dimensional gel electrophoresis to isolate the IRE-BP for protein sequencing. A degenerate oligonucleotide probe derived from a single peptide sequence was used to isolate a cDNA clone that encodes a protein containing 13 other sequenced peptides obtained from the IRE-BP. Consistent with previous characterization of the IRE-BP, the cDNA encodes a protein of 87 kDa with a slightly acidic pI, and the corresponding mRNA of approximately 3.6 kilobases is found in a variety of cell types. The encoded protein contains a nucleotide-binding consensus sequence and regions of cysteine and histidine clusters. This mRNA is encoded by a single gene on human chromosome 9, a finding consistent with previous localization by functional mapping. The protein contains no previously defined consensus motifs for either RNA or DNA binding. The simultaneous cloning of a different, but highly homologous, cDNA suggests that the IRE-BP is a member of a distinct gene family.