Role of the C-terminal linear region of EGF-like growth factors in ErbB specificity

EGF-Containing Membrane-Bound Mucins: A Hidden ErbB2 Targeting Pathway?

Membrane-bound mucins belong to a heterogeneous family of large O-glycoproteins involved in numerous cancers and inflammatory diseases of the epithelium. Some of them are also involved in protein-protein interactions, with receptor tyrosine kinase ErbB2, and fundamental and clinical data showed that these complexes have a detrimental impact on cancer outcome, thus raising interest in therapeutic targeting. This paper aims to demonstrate that MUC3, MUC4, MUC12, MUC13, and MUC17 have a common evolutionary origin and share a common structural organization with EGF-like and SEA domains. Theoretical structure-function relationship analysis of the conserved domains indicated that the studied membrane-bound mucins share common biological properties along with potential specific functions. Finally, the potential druggability of these complexes is discussed, revealing ErbB2-related pathways of cell signaling to be targeted.

Molecular pathways and molecular imaging in breast cancer: an update

Breast cancer is a heterogenic cancer being characterized by a variability of somatic mutations and in particular by different receptor expressions, such as estrogen, progesterone and human epidermal receptor. These phenotype characteristics play a crucial role in determining tumour response to various chemotherapies and other treatments and in the development of resistance to therapies. Positron emission tomography (PET) as a nuclear medicine technique, has recently demonstrated the advantages in determining the severity of disease and in evaluating the efficacy of treatments in a variety of neoplasm, including breast cancer. Because this procedure is able to pinpoint molecular activity within the body, it offers the potential to identify disease in its earliest stages as well as a patient's immediate response to therapeutic interventions in a non-invasive way. In this paper we performed an extended view about the correlation between molecular factors of breast cancer and PET tracers; in particular, we focalized our attention on their possible advantages in terms of 1) early detection of primary or recurrent cancer; 2) as a guide for target therapies and 3) for the evaluation of response to specific and now-available molecular treatments.

PET imaging of EGF receptors using [18F]FBEM-EGF in a head and neck squamous cell carcinoma model

PURPOSE

To prepare and evaluate a new radiotracer for molecular imaging of cell surface receptors for epidermal growth factor (EGF).

METHODS

Cys-tagged EGF (cEGF) was labeled with (18)F by coupling the free thiol group of the Cys tag with N-[2-(4-[(18)F]fluorobenzamido)ethyl]maleimide ([(18)F]FBEM) to form [(18)F]FBEM-cEGF. Cell uptake, internalization and efflux of [(18)F]FBEM-cEGF were tested in human head and neck squamous carcinoma UM-SCC1 cells. In vivo tumor targeting and pharmacokinetics of the radiotracers were evaluated in UM-SCC1 tumor-bearing athymic nude mice by static and dynamic microPET imaging. Ex vivo biodistribution assays were performed to confirm the noninvasive imaging results.

RESULTS

The radiolabeling yield for [(18)F]FBEM-cEGF was over 60%, based on starting [(18)F]FBEM. [(18)F]FBEM-cEGF exhibited rapid blood clearance through both hepatobiliary and renal excretion. UM-SCC1 tumors were clearly visualized and showed modest tracer uptake of 2.60 ± 0.59 %ID/g at 30 min after injection. Significantly higher tumor uptake of [(18)F]FBEM-cEGF (5.99 ± 1.61%ID/g at 30 min after injection, p < 0.01) and tumor/nontumor ratio were achieved by coinjection of 50 μg of unlabeled EGF. Decreased liver uptake of [(18)F]FBEM-cEGF was observed when unlabeled EGF was coadministered.

CONCLUSION

With optimized liver blocking, [(18)F]FBEM-cEGF has the potential to be used in a noninvasive and quantitative manner for detection of malignant lesions and evaluation of EGFR activity.