The expression of epidermal growth factor receptor on human bladder cancer: potential use in radioimmunoscintigraphy

Directed evolution to low nanomolar affinity of a tumor-targeting epidermal growth factor receptor-binding affibody molecule

The epidermal growth factor receptor 1 (EGFR) is overexpressed in various malignancies and is associated with a poor patient prognosis. A small, receptor-specific, high-affinity imaging agent would be a useful tool in diagnosing malignant tumors and in deciding upon treatment and assessing the response to treatment. We describe here the affinity maturation procedure for the generation of Affibody molecules binding with high affinity and specificity to EGFR. A library for affinity maturation was constructed by rerandomization of selected positions after the alignment of first-generation binding variants. New binders were selected with phage display technology, using a single oligonucleotide in a single-library effort, and the best second-generation binders had an approximately 30-fold improvement in affinity (K(d)=5-10 nM) for the soluble extracellular domain of EGFR in biospecific interaction analysis using Biacore. The dissociation equilibrium constant, K(d), was also determined for the Affibody with highest affinity using EGFR-expressing A431 cells in flow cytometric analysis (K(d)=2.8 nM). A retained high specificity for EGFR was verified by a dot blot assay showing staining only of EGFR proteins among a panel of serum proteins and other EGFR family member proteins (HER2, HER3, and HER4). The EGFR-binding Affibody molecules were radiolabeled with indium-111, showing specific binding to EGFR-expressing A431 cells and successful targeting of the A431 tumor xenografts with 4-6% injected activity per gram accumulated in the tumor 4 h postinjection.

Phage display selection of Affibody molecules with specific binding to the extracellular domain of the epidermal growth factor receptor

Affibody molecules specific for the epidermal growth factor receptor (EGFR) have been selected by phage display technology from a combinatorial protein library based on the 58-residue, protein A-derived Z domain. EGFR is overexpressed in various malignancies and is frequently associated with poor patient prognosis, and the information provided by targeting this receptor could facilitate both patient diagnostics and treatment. Three selected Affibody variants were shown to selectively bind to the extracellular domain of EGFR (EGFR-ECD). Kinetic biosensor analysis revealed that the three monomeric Affibody molecules bound with similar affinity, ranging from 130 to 185 nM. Head-to-tail dimers of the Affibody molecules were compared for their binding to recombinant EGFR-ECD in biosensor analysis and in human epithelial cancer A431 cells. Although the dimeric Affibody variants were found to bind in a range of 25-50 nM affinities in biosensor analysis, they were found to be low nanomolar binders in the cellular assays. Competition assays using radiolabeled Affibody dimers confirmed specific EGFR-binding and demonstrated that the three Affibody molecules competed for the same epitope. Immunofluorescence microscopy demonstrated that the selected Affibody dimers were initially binding to EGFR at the cell surface of A431, and confocal microscopy analysis showed that the Affibody dimers could thereafter be internalized. The potential use of the described Affibody molecules as targeting agents for radionuclide based imaging applications in various carcinomas is discussed.

Analysis of HER2 expression in primary urinary bladder carcinoma and corresponding metastases

OBJECTIVE

To evaluate the expression of HER2 receptors (previously reported to be over-expressed in malignant urothelium) in both primary tumours and metastases of transitional cell cancer, using two different staining methods and two different scoring techniques, considering the potential use of these receptors as targets for planned systemic anti-HER2 nuclide-based treatment.

MATERIALS AND METHODS

HER2 expression was evaluated with two different immunohistochemical methods in 90 patients with primary urinary bladder cancer tumours and corresponding metastases. Sections were first stained with the commercially available breast cancer test kit (HercepTest, Dako, Glostrup, Denmark). Parallel sections were then stained with a modified HercepTest procedure. Two different evaluation criteria were compared; the HercepTest score that requires > or = 10% stained tumour cells (as for breast cancer) and a proposed 'Target score' that requires > 67% stained tumour cells. The latter score is assumed to be preferable for HER2-targeted radionuclide therapy.

RESULTS

Using the HercepTest kit, the Target score gave lower fractions of positive primary tumours and metastases than the HercepTest score. The modified HercepTest staining procedure and Target score gave high HER2 values in 80% of primary tumours and 62% of metastases, which is considerably more than that obtained with the HercepTest staining and score. There was a significant decrease in HER2 positivity with increasing distance from the primary tumour. In nine sentinel-node metastases assessed, all but one were HER2-positive. Considering all regional metastases, 74% were positive, and of distant metastases, 47%; 72% of the patients with positive primary tumours also expressed HER2 in their metastases.

CONCLUSIONS

When combining the modified HercepTest with customised evaluation criteria, more HER2-positive tumours were diagnosed. The degree of HER2 down-regulation was significantly higher in distant than in regional metastases. HER2-targeted therapy may be an alternative or complementary to other methods in the future treatment of metastatic urinary bladder carcinoma.

Expression of epidermal growth factor receptor in urinary bladder cancer metastases

Bladder cancers frequently exhibit an increased number of epidermal growth factor receptors (EGFR) in comparison to normal urothelium. The EGFR could potentially be a target for toxic conjugates. The aim of our study was to compare the expression of EGFR in metastases with concurrent or primary tumour in the urinary bladder using immunohistochemical techniques and a monoclonal antibody. Tumour material from 20 patients was investigated. The majority (13/20) of the metastases were homogeneously stained and showed a moderate to strong membranous staining for EGFR. The expression of EGFR in primary bladder tumours and metastases was similar. There was no indication that tumour tissue exposed to chemotherapy or radiation had a decreased number of EGFR. Targeting of the EGFR thus seems potentially applicable to metastatic disease.

Recovery of epidermal growth factor in voided urine of patients with bladder cancer

Epidermal growth factor (EGF), a potent mitogen and tumor promoter, is excreted in urine permitting it to incubate with urothelial cells. We have previously shown that the distribution of receptors for EGF (EGF-Rs) on malignant urothelium changes to favor contact between EGF-Rs and intraluminal EGF. OBJECTIVES. To determine if concentrations of EGF in voided urine are different in patients with transitional cell carcinoma (TCC) of the bladder than in those without this condition. METHODS. EGF was measured by radioimmunoassay in the urine of 54 patients with newly diagnosed TCC (16 with grade 1, Stage Ta lesions, and 38 with grade 3, Stage T > or = 2 lesions) and 66 pathologic and normal controls without TCC. Subjects were matched for age and good renal function. RESULTS. EGF concentrations were significantly reduced in patients with TCC compared with controls either when uncorrected (p < 0.0001) or corrected (p < 0.000000002) for urinary creatinine excretion. CONCLUSIONS. The reduced concentration of EGF in voided urine supports previous evidence that the urinary EGF/urothelial EGF-R interaction is important for TCC development and growth, and has the potential to serve as a marker of tumor persistence, recurrence, and therapeutic response.

Alterations in antigen expression in superficial bladder cancer

Bladder cancer can be viewed as a prototype for carcinogen-induced neoplasia. This has been demonstrated experimentally in a variety of systems and in man through epidemiological studies of occupational exposure to putative carcinogens. The natural history of this neoplasm demonstrates recurrence in time and space, i.e., multifocal disease. This clinical scenario is precisely what would be expected if a target tissue, e.g., urothelium, was continuously exposed to a weak carcinogen. The detection of gross disease is clinically easy. However, the ability to intervene at early stages and monitor the success of this treatment requires the definition of early markers for bladder cancer. Integrins are a family of cell surface proteins, many of which function as receptors for extracellular matrix components. Normal epithelial cells express the integrin alpha 6 beta 4 in association with an anchoring structure known as the hemidesmosome. Urothelium expresses alpha 6 beta 4 on the basal layer of cells similar to the distribution seen on other epithelial surfaces. Even early stages of bladder cancer demonstrate an alteration in the expression of this integrin. Low-stage bladder tumors express alpha 6 beta 4 diffusely throughout the tumor as well as at the invading margin. Altered expression of alpha 6 beta 4 may be an early marker for bladder cancer which may contribute to an invasive phenotype. A second potential marker is detected by DD23, an IgG1 murine monoclonal antibody triggered by the immunization of a BALB/c mouse with a fresh human bladder tumor specimen. The antigen detected by DD23 is not present on normal urothelial specimens.(ABSTRACT TRUNCATED AT 250 WORDS)

Epidermal growth factor and its receptor: markers of--and targets for--chemoprevention of bladder cancer

Epidermal growth factor (EGF) is excreted in urine in high concentrations in a biologically active form. Several lines of evidence indicate that EGF plays a role in transitional cell carcinoma (TCC) development and growth. These include: (1) EGF in the normal urine of rats promotes chemically initiated TCC; (2) EGF in normal human urine stimulates the clonal growth of human TCC cells in vitro; (3) EGF stimulates the in vitro growth of human TCC cells, but not normal human urothelial cells; (4) the density and distribution of the EGF receptor (EGF-R) on human urothelial tissues permits significant access of premalignant, dysplastic, and malignant cells to EGF; and (5) the concentration of EGF in the voided urine of patients with TCC is reduced, implying that EGF may be "extracted" from urine by the greater number of EGF-Rs in patients with urothelial malignancy. Abnormal expression of the urothelial EGF-R and/or altered excretion of EGF may well precede overt evidence of TCC and thus may serve as markers of risk or exposure. Similarly, reversion of EGF-R expression or the return of excreted EGF to normal levels may provide a marker of response for preventive and therapeutic strategies. Interference with the EGF/EGF-R interaction through dietary or pharmacological manipulations of the urine, or via targeting strategies employing intravesical administration of conjugated toxins or isotopes is already being employed in experimental and clinical studies. These approaches offer promising new tools in the detection, monitoring, prevention, and management of early stage bladder cancer.