Construction of immunoradiometric assay for circulating c-erbB-2 protooncogene product in advanced breast cancer patients

Clinical implications of the ErbB/epidermal growth factor (EGF) receptor family and its ligands in ovarian cancer

The ERBB or EGF receptor (EGFR) proto-oncogene family, which consists of four structurally-related transmembrane receptors (i.e., EGFR, ErbB2, ErbB3, and ErbB4), plays an etiological role in the molecular pathogenesis of cancer and is a key therapeutic target in many types of cancer, including ovarian cancer. These ErbB/EGF receptor tyrosine kinases play important physiologic roles in cell proliferation, survival, adhesion, motility, invasion, and angiogenesis. It is, therefore, not surprising that gene amplification, genetic mutation, and altered transcription/translation result in aberrant ErbB/EGF receptor expression and/or signal transduction, contributing to the development of malignant transformation. Clinically, the diagnostic, prognostic, and theragnostic significance of any single ErbB receptor and/or ErbB ligand is controversial, but generally, ErbB receptor overexpression has been correlated with poor prognosis and decreased therapeutic responsiveness in ovarian cancer patients. Thus, anticancer agents targeting ErbB/EGF receptors hold great promise for personalized cancer treatment. Yet, challenges remain in designing prospective clinical trials to assess the clinical utility of ErbB receptors and their ligands to diagnose cancer; to predict progression-free and overall survival, therapeutic responsiveness, and disease recurrence; and to monitor treatment responsiveness. Here, we review the tissue expression and serum biomarker studies that have evaluated the diagnostic, prognostic, and theragnostic utility of ErbB/EGF receptors, their circulating soluble isoforms (sEGFR/sErbBs), and their cognate ligands in ovarian cancer patients.

Monitoring the Circulating Levels of the HER2/neu Oncoprotein in Breast Cancer

The HER2/neu oncoprotein is a major target for the development of new cancer therapies and is similar to the estrogen receptor, which guides hormone therapy. The HER2/neu status is used to guide therapy decisions in patients with HER2/neu-overexpressing breast cancer tumors. The HER2/neu oncogene, or c-erbB-2, encodes a transmembrane receptor protein that is expressed on normal epithelial cells and can be overexpressed in breast cancer cells. Studies have shown that the extracellular domain (ECD) of the HER2/neu oncoprotein is released from the cell and can be measured in the circulation of women with breast cancer. Enzyme-linked immunosorbent assay methods used to measure the circulating HER2/neu ECD have shown that the prevalence of elevated ECD levels is approximately 18.1% in women with primary breast cancer and approximately 45.6% in women with metastatic breast cancer (MBC). Many studies have monitored the circulating ECD levels after surgery and indicate that increasing ECD levels can indicate recurrence of breast cancer earlier than clinical diagnosis. Studies in women with MBC showed that serial changes in circulating HER2/neu ECD levels paralleled the clinical course of disease, regardless of the treatment regimen. Several studies identified a subgroup of patients with MBC who had HER2/neu-negative disease by tissue testing but developed elevated ECD levels with MBC. In contrast to tissue testing, which is a one-time event, monitoring the circulating levels of the HER2/neu ECD in patients with breast cancer provides a real-time assessment of the HER2/neu status and provides important information for managing the therapy of patients with MBC.

Potential clinical utility of serum HER-2/neu oncoprotein concentrations in patients with breast cancer

BACKGROUND

The HER-2/neu oncogene and its p185 receptor protein are indicators of a more aggressive form of breast cancer. HER-2/neu status guides Herceptin therapy, specifically directed to the extracellular domain (ECD) of the HER-2/neu oncoprotein. The HER-2/neu ECD is shed from cancer cells into the circulation and is measurable by immunoassay.

METHODS

We performed a systematic review of the peer-reviewed literature on circulating ECD with respect to prevalence, prognosis, prediction of response to therapy, and monitoring of breast cancer.

RESULTS

The prevalence of increased ECD in patients with primary breast cancer varied between 0% and 38% (mean, 18.5%), whereas in metastatic disease the range was from 23% to 80% (mean, 43%). Some women with HER-2/neu-negative tumors by tissue testing develop increased ECD concentrations in metastatic disease. Increased ECD has been correlated with indicators of poor prognosis, e.g., overall survival and disease-free survival. Increased ECD predicts a poor response to hormone therapy and some chemotherapy regimens but can predict improved response to combinations of Herceptin and chemotherapy. Many studies support the value of monitoring ECD during breast cancer progression because serial increases precede the appearance of metastases and longitudinal ECD changes parallel the clinical course of disease.

CONCLUSIONS

The monitoring of circulating HER-2/neu ECD provides a tool for assessing prognosis, for predicting response to therapy, and for earlier detection of disease progression and timely intervention with appropriate therapy.

ErbB-2 protein in sera and tumors of breast cancer patients

We compared levels of erbB-2 oncoprotein among three groups: Group I included 60 asymptomatic women; Group II had 51 women with benign breast biopsies; and Group III had 67 women with node-negative breast cancer. Serological levels of erbB-2 protein were measured in all participants; tumor levels were measured for Groups II and III. Forty-three percent of usable tumors (25/58), including three of seven lobular tumors, were erbB-2 positive. Tumor and blood oncoprotein levels were unrelated. Blood levels, however, were positively related to tumor volume, but only when the tumor had both a ductal carcinoma in situ (DCIS) component and an invasive component, suggesting a role for erbB-2 protein in progression of DCIS to invasive carcinoma. In Groups I and II serological levels of erbB-2 protein were directly related to age, and inversely related to having had a live birth. Therefore, a model that determined the threshold levels of serological erbB-2 positivity in Group III included age and nulliparity as independent variables. Only three of the 67 women (4.5%) in Group III were positive for serological erbB-2. In a multivariate model, with serological erbB-2 as the dependent variable, and in which the independent variables included Study Group, there was a statistical trend for younger women, in which Group III had the highest serological levels of erbB-2, followed by Group II, and then Group I. In women who were over the age of 50 years the trend was reversed; i.e., levels of erbB-2 tended to be lowest in Group III, followed by Group II, and finally Group I.

Molecular markers of carcinogenesis

The protein products of oncogenes and tumor suppressor genes play critical roles in the development of many cancers. The expression of a number of these proteins can be detected in extracellular fluids such as blood. This article reviews the literature on the application of methods for the detection of the proteins of oncogenes and tumor suppressor genes in the blood of humans with cancer or at risk for the development of cancer. The detection of these proteins in blood may be useful molecular markers of carcinogenesis that could play an important part in cancer diagnosis, prognosis, and prevention.

Biomarkers of gene expression: growth factors and oncoproteins

This article reviews the literature on the application of methods for the detection of growth factors, oncogene proteins, and tumor-suppressor gene proteins in the blood of humans with cancer or who are at risk for the development of cancer. The research summarized here suggests that many of these biomarker assays can be used to distinguish between diseased and nondiseased states and in some instances may be able to predict susceptibility for future disease. Thus, these biomarkers could be valuable tools for monitoring at-risk populations for purposes of disease prevention and control.

Flow Cytometric Assay of c-erbB-2 Protein in Fine Needle Aspirates of Fresh and Frozen Human Breast Cancer Tissues

Using FCM (flow cytometry), we analyzed the ErbB-2 (c-erbB-2 protein) status of 61 breast cancer tissue samples obtained by FNAB (fine-needle aspiration biopsy). The number of cancer cells collected by FNAB from fresh samples was 1.7+/-0.7 x10&sup5;, 2.5 +/-0.6 x10&sup5;, and 4.0+/- 0.8x10 &sup5;, by single, double and triple aspirations, respectively. A mean of 3.0+/-0.6 x10&sup5;cells was collected on three aspirations from frozen samples. The number of cells collected on three aspirations was sufficient for the measurement of ErbB-2. Cells with higher ErbB-2 levels than those of normal human lymphocytes were designated ErbB-2 positive cells. The mean overall for ErbB-2 positive cell rates was 20.5 +/- 27.9 % (mean+/-SD). The rates were 27.9 +/- 31.6 % in patients with recurrence and 15.9 +/- 24.4% in patients without recurrence. When the cut-off value was set at 20% of the positive cell rate (P =0.008, generalized Wilcoxon test), patients with ErbB-2 negative tumors showed highly significantly longer survival without recurrence (P=0.008, generalized Wilcoxontest) and better overall survival rates (P=0.013) than patients with ErbB-2 positive tumors. Among 61 specimens, 16 (26.2%) scored positive for ErbB-2 by FCM. These finding indicated that the analysis of ErbB-2 status using FCM of samples obtained by FNAB should be useful for preoperatively evaluating the prognosis of patients with breast cancer.

Simultaneous Assay of ErbB-2 Protein and Carcinoembryonic Antigen in Cyst Fluid as an Aid in Diagnosing Cystic Lesions of the Breast

C-erbB-2 oncoprotein (ErbB-2 protein)and carcinoembryonic antigen (CEA)were simultaneously evaluated in the breast cyst fluid of 6 patients with intracystic cancer, 6 patients with intracystic papilloma, and 42 patients with gross cystic disease. A combination test, using 12 ng of ErbB-2 protein and 150 ng of CEA/ml of cyst fluid, respectively, as cutoff values resulted in a positive detection rate of 83%(5/6 cases) for intracystic breast cancer. Two of the 6 patients with intracystic papilloma and 2 of the 42 patients with gross cystic disease were positive. In addition, elevated levels of these markers in cyst fluid correlated well with the expression of these antigens in the corresponding tumor. Thus, it can be concluded that measurements of ErbB-2 protein and CEA aid in the diagnosis of intracystic breast cancer, and the assay of ErbB-2 protein is valuable for detecting tumors in which this protein is overexpressed.

Detection of increased amounts of the extracellular domain of the c-erbB-2 oncoprotein in serum during pulmonary carcinogenesis in humans

Over-expression of the c-erbB-2 oncogene-encoded p185 protein product has been implicated in the pathogenesis of a wide variety of human malignancies, including lung cancer. Over-expression of p185 can be detected immunologically by quantification of the extracellular domain of p185 (c-erbB-2 oncopeptide) in extracellular fluid in vitro and in serum in vivo. An enzyme-linked immunosorbent assay (ELISA) for the c-erbB-2 oncopeptide was used to examine banked serum samples of 11 pneumoconiosis patients who subsequently developed lung cancer and serum samples from 11 hospital controls matched for age, sex, ethnic group and smoking as well as 55 unmatched general population controls. The mean serum level for the c-erbB-2 oncopeptide in human neu units/ml in the lung cancer cases (1,756 +/- 549 HNU/ml) was statistically significantly elevated (p < 0.001) in comparison to the mean level in the matched controls (976 +/- 488 HNU/ml) or the general population controls (888 +/- 655 HNU/ml). Defining a positive elevation of the serum c-erbB-2 oncopeptide as any value more than 2 standard deviations above the mean of the matched controls, 64% (7 of 11) of the lung cancer cases were positive compared to 0% (0 of 11) matched controls and 5% (3 of 55) of the unmatched controls. In addition, 4 of the 7 c-erbB-2 oncopeptide-positive cancer cases had positive serum samples prior to the time of disease diagnosis (average = 35 months). These results suggest that serum c-erbB-2 oncopeptide may be elevated at an early stage of pulmonary carcinogenesis and that further prospective study of the utility of this biomarker is warranted.