Detection of ErbB2 oversignalling in a majority of breast cancers with phosphorylation-state-specific antibodies

The antibody sc-33040-R fails to specifically recognize phosphorylation of ErbB4 on tyrosine1056

Phosphorylation state specific antibodies are important reagents for characterizing protein phosphorylation and signaling. However, these antibodies require proper validation to determine that they do not cross-react with the unphosphorylated peptide or with other phosphoproteins. We have previously shown that phosphorylation of tyrosine1056 of ErbB4 is critical for it to inhibit colony formation on plastic by human tumor cell lines. Thus, an antibody directed against this site would be useful for studying ErbB4 signaling and coupling to biological responses. Here, we demonstrate that a commercially available antibody raised against a phosphopeptide corresponding to the carboxyl-terminal domain of the ErbB4 receptor tyrosine kinase fails to exhibit appropriate specificity. Thus, this antibody does not appear to be suitable for studying ErbB4 phosphorylation or signaling.

Evaluation of Plasma Insulin-like Growth Factor Binding Protein 2 and Her-2 Extracellular Domain as Biomarkers for 17-Allylamino-17-Demethoxygeldanamycin Treatment of Adult Patients with Advanced Solid Tumors

PURPOSE

Interaction of 17-allylamino-17-demethoxygeldanamycin (17-AAG) with heat shock protein 90 results in proteasomal degradation of many proteins, including Her-2-neu, with subsequent decreased expression of insulin-like growth factor binding protein-2 (IGFBP-2). Concentrations of both IGFBP-2 and Her-2 extracellular domain (Her-2 ECD) in sera of mice bearing BT474 human breast cancer xenografts decrease after 17-AAG treatment. We investigated whether this phenomenon occurred in patients.

MATERIALS AND METHODS

Eight to 15 plasma samples were obtained between 0 and 72 h from 27 patients treated with single-agent 17-AAG at doses between 10 and 307 mg/m(2) and 18 patients treated with 17-AAG at doses between 220 and 450 mg/m(2) combined with 70 to 75 mg/m(2) of docetaxel. Pretreatment plasma samples were also obtained from 12 healthy volunteers. Plasma IGFBP-2 and Her-2 ECD concentrations were quantitated by ELISA.

RESULTS

Pretreatment plasma IGFBP-2 concentrations in patients (171 +/- 116 ng/mL) were 2-fold higher than those in healthy volunteers (85 +/- 44 ng/mL; P < 0.05). Following 17-AAG treatment, there were no consistent dose-dependent or time-dependent changes in plasma IGFBP-2 and Her-2 ECD concentrations. IGFBP-2 concentrations decreased by >or=40% in 8 patients, increased 2- to 5-fold in 8 patients, and remained essentially unchanged in 29 patients. Her-2 ECD concentrations decreased by >or=40% in 10 patients, increased 1.5- to 5-fold in 2 patients, and remained essentially unchanged in 25 patients.

CONCLUSIONS

As previously reported, IGFBP-2 concentrations in plasma of cancer patients are significantly higher than those in healthy volunteers. In contrast to a mouse model, 17-AAG treatment was not consistently associated with decreases in IGFBP-2 or Her-2 ECD concentrations in patient plasma.

Mining the tumor phosphoproteome for cancer markers

Despite decades of cancer research, mortality rates remain high largely due to the failure of early detection, poor understanding of the epidemiology of rational drug targets, and molecular etiology of human cancers. The discovery of disease markers promises to deliver some solutions to these formidable challenges. Gene and protein expression profiling through DNA microarray and proteomics have already made a tremendous effect in this area. However, protein/gene expression does not necessarily reflect protein activity, which is often regulated via post-translation modifications, of which phosphorylation is one of the most prominent. This is an important consideration because the activity of protein is a more relevant phenotype than its expression during pathogenesis. Tyrosine kinases represent a very important class of enzymes that are critical regulators of mitogenic and angiogenic signaling, hence attractive targets for anticancer drugs as exemplified by BCR-ABL and ErbB2. More than 50% of them are overexpressed or mutated resulting in a gain of function in various human cancers. In this review, we discuss the potential effect of phosphoproteins as cancer markers in cancer diagnosis and therapeutics. Phosphoproteomics strategies that might pave the way to high-throughput analysis for routine clinical applications are also described.

Gene expression profiling allows distinction between primary and metastatic squamous cell carcinomas in the lung

Lung neoplasms commonly develop in patients previously treated for head and neck carcinomas. The derivation of these tumors, either as new primary lung cancers or as metastatic head and neck cancers, is difficult to establish based on clinical or histopathologic criteria since both are squamous cell carcinomas and have identical features under light microscopy. However, this distinction has significant treatment and prognostic implications. Gene expression profiling was performed on a panel of 52 sequentially collected patients with either primary lung (n = 21) or primary head and neck (n = 31) carcinomas using the Affymetrix HG_U95Av2 high-density oligonucleotide microarray. Unsupervised hierarchical clustering with Ward linkage and the Pearson correlation metric was performed. To assess robustness, bootstrap resampling was performed with 1,000 iterations. A t test of the normalized values for each gene was used to determine the genes responsible for segregating head and neck from lung primary carcinomas, and those with the most differential expression were used for later analyses. In the absence of a large "test" set of tumors, we used a supervised leave-one-out cross-validation to test how well we could predict the tumor origin. Once a gene expression profile was established, 12 lung lesions taken from patients with previously treated head and neck cancers were similarly analyzed by gene expression profiling to determine their sites of origin. Unsupervised clustering analysis separated the study cohort into two distinct groups which reliably remained segregated with bootstrap resampling. Group 1 consisted of 30 tongue carcinomas. Group 2 consisted of 21 lung cancers and 1 tongue carcinoma. The clustering was not changed even when normal lung or tongue profiles were subtracted from the corresponding carcinomatous lesions, and a leave-one-out cross-validation showed a 98% correct prediction (see Supplementary Data 1). A minimum set of 500 genes required to distinguish these groups was established. Given the ability to segregate these lesions using molecular profiling, we analyzed the lung tumors of undetermined origin. All cases clearly clustered with either lung or tongue tumor subsets, strongly supporting our hypothesis that this technique could elucidate the tissue of origin of metastatic lesions. Although histologically similar, squamous cell carcinomas have distinct gene expression profiles based on their anatomic sites of origin. Accordingly, the application of gene expression profiling may be useful in identifying the derivation of lung nodules and consequently enhances treatment planning.

Upregulated Akt signaling adjacent to gastric cancers: implications for screening and chemoprevention

Most gastric adenocarcinomas arise as a longterm complication of Helicobacter pylori infection of the stomach, but the high prevalence of this infection limits the cost-effectiveness of antibiotic eradication as a cancer prevention strategy. Here we have used phosphorylation-specific antibodies against the Akt kinase consensus sequence to detect downstream substrates of this oncogenic signaling pathway in normal and malignant gastric tissues. In vitro studies confirm that phosphorylation of Akt and its substrates is inducible by epithelial mitogens such as epidermal growth factor (EGF), which is implicated in the pathogenesis of H. pylori gastritis. Control clinical studies confirm far stronger Akt substrate phosphorylation in primary human breast cancers than in matched adjacent normal breast tissues; unexpectedly, however, increased Akt signaling is apparent in both primary stomach cancers and adjacent normal gastric tissues. These findings raise the possibility of a preneoplastic field defect induced in morphologically normal tissues, and suggest that immunoassays of mucosal Akt activity could guide preventive surveillance and/or intervention in patients at risk of gastric cancer. Moreover, since recent reports confirm Akt inhibition by COX-2 inhibitors, these data support the chemopreventive efficacy of such drugs for at-risk individuals.

Detection of urokinase plasminogen activator receptor and c-erbB-2 in sera of patients with breast and ovarian carcinoma

The role of urokinase plasminogen activator receptor (uPAR) and c-erbB-2 in breast and ovarian cancer was investigated. Eighty patients of breast and ovarian cancer and benign lesions, as well as twenty normal controls were evaluated for the expression of c-erbB-2 by Western blotting and uPAR levels by ELISA. The c-erbB-2 and uPAR showed a significant increase in both types of cancer investigated compared to normal control and benign lesions. The frequency of c-erbB-2 was significantly higher in breast cancer lesions (p < 0.01). Levels of CA15.3 in breast cancer and CA125 in ovarian cancer were significantly higher in cases expressing c-erbB-2 (p < 0.01) than in negative c-erbB-2 cases. The uPAR showed a significant positive correlation with advanced stages of breast cancer (r = 0.7971) and ovarian cancer (r = 0.83662), while significant correlations were found for CA15.3 in breast cancer (r = 0.64967) and CA125 in ovarian cancer (r = 0.83996). Taken together, our data suggest that the c-erbB-2 and uPAR in the sera of ovarian and breast cancer act as valuable markers for the evaluation of the patients preoperatively.

Phosphorylation state-specific antibodies: applications in investigative and diagnostic pathology

Until recently, the investigation of protein phosphorylation was limited to biochemical studies of enzyme activities in homogenized tissues. The availability of hundreds of phosphorylation state-specific antibodies (PSSAs) now makes possible the study of protein phosphorylation in situ, and is opening many exciting opportunities in investigative and diagnostic pathology. This review illustrates the power of PSSAs, especially in immunohistochemical applications to human disease and animal models. Technical considerations, including antibody specificity and lability of phosphoepitopes, are covered, along with potential pitfalls, illustrated by a case study. In the arena of oncology, PSSAs may prove especially valuable in directly demonstrating the efficacy of chemotherapies targeted at protein kinase cascades. Novel applications of PSSAs are also beginning to reveal molecular mechanisms of inflammatory, degenerative, and toxin-induced diseases.

The potential use of saliva to detect recurrence of disease in women with breast carcinoma

BACKGROUND

Approximately 1 woman in every 10 will develop breast cancer in her lifetime. It has been shown that screening for breast cancer can reduce breast cancer mortality. The use of a saliva-based test could prove to be very useful in post-operative and/or adjunctive therapy management of breast cancer patients.

METHODS

The following study was undertaken to establish the possible usefulness of the salivary protein product of the oncogene c-erbB-2 in following patients diagnosed with carcinoma of the breast. Included in this study were 25 patients with a mean age of 54 years with varying histological diagnoses and stages of carcinoma of the breast. ELISA assays for c-erbB-2 and CA 15-3 were performed on serum and stimulated whole saliva samples collected on all patients prior to any adjunct therapy or surgery and sequentially during therapy.

RESULTS

The results of the GLM analyses using marker concentration as the dependent variable and treatment regimen and the serial assessments as independent variables yielded a significant overall model for both the serum (P < 0.007) and salivary (P < 0.017) c-erbB-2 markers. The model for serum c-erbB-2, however, exhibited a significant difference for treatment regimen (P < 0.001) with the chemotherapy and radiation treatment regimen being significantly different (P < 0.001) from the other treatment therapies. Time (serial assessments) was not significant. The model for the salivary c-erbB-2 marker was reversed. Treatment regimen was not significant for this model; however, time (serial assessments) was significant (P < 0.002). The serum and salivary CA 15-3 marker models yielded no significant results. Paired t-test analyses indicated that only the salivary c-erbB-2 concentrations exhibited a significant difference between the pre- and post-therapy values (t = 4.245, P < 0.0001). Additionally, salivary c-erbB-2 displayed greater percent reductions across all therapies as compared to the other markers.

CONCLUSIONS

This preliminary study appears to indicate that c-erbB-2 protein expression in saliva may be a very useful diagnostic tool for measuring patient response to chemotherapy and/or surgical treatment of their disease.

Dominant negative knockout of p53 abolishes ErbB2-dependent apoptosis and permits growth acceleration in human breast cancer cells

We previously reported that the ErbB2 oncoprotein prolongs and amplifies growth factor signalling by impairing ligand-dependent downregulation of hetero-oligomerised epidermal growth factor receptors. Here we show that treatment of A431 cells with different epidermal growth factor receptor ligands can cause growth inhibition to an extent paralleling ErbB2 tyrosine phosphorylation. To determine whether such growth inhibition signifies an interaction between the cell cycle machinery and ErbB2-dependent alterations of cell signalling kinetics, we used MCF7 breast cancer cells (which express wild-type p53) to create transient and stable ErbB2 transfectants (MCF7-B2). Compared with parental cells, MCF7-B2 cells are characterised by upregulation of p53, p21(WAF) and Myc, downregulation of Bcl2, and apoptosis. In contrast, MCF7-B2 cells co-transfected with dominant negative p53 (MCF7-B2/Delta p53) exhibit reduced apoptosis and enhanced growth relative to both parental MCF7-B2 and control cells. These data imply that wild-type p53 limits survival of ErbB2-overexpressing breast cancer cells, and suggest that signals of varying length and/or intensity may evoke different cell outcomes depending upon the integrity of cell cycle control genes. We submit that acquisition of cell cycle control defects may play a permissive role in ErbB2 upregulation, and that the ErbB2 overexpression phenotype may in turn select for the survival of cells with p53 mutations or other tumour suppressor gene defects.

Reliability assessment of soluble c-erbB-2 concentrations in the saliva of healthy women and men

BACKGROUND

The protein c-erb B-2, also known as Her2/neu, is a prognostic breast cancer marker assayed in tissue biopsy specimens from women diagnosed with malignant tumors. Current studies suggest that soluble fragments of the c-erb B-2 oncogene may be released from the cell surface and become detectable in patients with a carcinoma of the breast. Consequently, the purpose of this study is to assay soluble c-erb B-2 protein in the saliva of healthy men and women to determine the reliability of the assay.

METHODS

To determine the diagnostic utility of this oncogene, we assayed the soluble form of the c-erb B-2 protein in the saliva with an enzyme-linked immunosorbent assay. The study population consisted of 10 healthy women and 9 healthy men who were serially sampled for saliva 3 times a day for a 5-day period. Saliva was collected from each subject at 9 AM, 4 PM, and 9 PM during the 5-day period.

RESULTS

We found the presence of c-erb B-2 protein in the saliva of both groups of subjects. The salivary levels of c-erb B-2 were not significantly different when compared for gender differences. Likewise, the results suggest that sampling during various times of the day for salivary c-erb B-2 levels has no effect on marker concentration. Reliability analyses showed that supervised salivary collections were more reliable than unsupervised collections.

CONCLUSIONS

The results of this pilot study suggest that the assay for salivary c-erb B-2 protein is reliable and might have potential use in the initial detection and follow-up screening for the recurrence of breast cancer in both men and women.

Association of ErbB2 Ser1113 phosphorylation with epidermal growth factor receptor co-expression and poor prognosis in human breast cancer

The carboxyterminal domain of the epidermal growth factor receptor (EGFR)--a putative binding site for the ubiquitin ligase Cbl--is the site of serine phosphorylation events which are essential for ligand-dependent EGFR desensitization and degradation. Using a monoclonal antibody (aPS1113) which selectively recognizes the homologous phosphorylated domain in the ErbB2 oncoprotein, we show here that wild-type ErbB2 becomes Ser1113-phosphorylated following treatment of 3T3 cells with growth factors or tyrosine phosphatase inhibitors. In EGFR-overexpressing A431 cells, ligand-inducible aPS1113 immunoreactivity declines more rapidly than other detectable phosphorylation events and is followed by EGFR downregulation. Analysis of 65 ErbB2-expressing primary breast cancers reveals a highly significant relationship between Ser1113 phosphorylation and EGFR overexpression (p < 0.0001) as well as an association with poor prognosis (p = 0.005). We submit that ErbB2 Ser1113 phosphorylation status represents a novel and informative biomarker of cancer cell biology and tumor behavior.