Jill L. Reiter

EGF/ErbB Receptor Family in Ovarian Cancer

In summary, the EGF/ErbB family of receptor tyrosine kinases has been shown to play a key role in normal ovarian follicle development, and cell growth regulation of the ovarian surface epithelium. Disregulation of these normal growth regulatory pathways, including overexpression and/or mutation of EGFR/ErbB receptor family members, as well as elements of their downstream signalling pathways, have been shown to contribute to the etiology and progression of epithelial ovarian cancer. It is, therefore, not surprising that these gene products, and their related soluble receptor isoforms may have clinical utility as tumor and/or serum biomarkers of disease activity. Moreover, since several of these soluble receptor isoforms have potent growth inhibitory activity, and are naturally occurring in the circulation, they are ideal candidates for the development of novel therapeutics for the treatment of ovarian cancer patients.

Characterization and Expression of Novel 60‐kDa and 110‐kDa EGFR Isoforms in Human Placenta

Abstract: The epidermal growth factor receptor (EGFR) and related family members (ERBB2, ERBB3, and ERBB4) previously have been shown to play pivotal roles in the development of female reproductive tissues, in blastocyst implantation, and in placental differentiation. We have cloned and sequenced several naturally occurring alternative transcripts of the human and mouse EGFR genes, which encode novel receptor isoforms containing varying portions of the extracellular ligand‐binding domain, but lacking the transmembrane and cytoplasmic domain sequences. The human 1.8‐kb and 3‐kb alternative EGFR transcripts encode secreted 60‐kDa and cell surface‐associated 110‐kDa EGFR isoforms, respectively. We have developed quantitative ribonuclease protection assays to study the expression of these alternative transcripts in human tissues. Similar to the full‐length EGFR mRNAs, the highest expression level of these alternative transcripts occurs in placenta. We speculate that both of these EGFR isoforms may be important regulators of EGF‐mediated cell growth and differentiation in human placenta.

Generation and characterization of polyclonal antibodies specific for human p110 sEGFR.

The EGFR/ERBB family of receptor tyrosine kinases mediates intracellular signal transduction pathways important in the regulation of cell growth, differentiation, and transformation. We previously have reported the cloning and expression of a 3 kb alternative EGFR transcript which encodes a 110 kDa form of the receptor (p110 sEGFR). This receptor isoform is identical to the extracellular region of the full-length 170 kDa EGFR through amino acid 603; in addition, p110 sEGFR contains 78 unique carboxy-terminal amino acids. Here, we report the generation and characterization of polyclonal antisera specific for the unique carboxy-terminal sequence of p110 sEGFR. Polyclonal antisera were generated by immunizing rabbits with synthetic peptides corresponding to peptides contained within the unique carboxy-terminal sequence of p110 sEGFR. Immunoglobulin fractions from antisera which tested positive for immune reactivity to these peptides by ELISA were affinity-purified by protein G and peptide-based chromatography. This affinity-purified immunoglobulin fraction specifically recognizes p110 sEGFR by ELISA, immunoprecipitation, immunoblot analysis, and immunocytochemical methods. No cross-reactivity with full-length p170 EGFR is observed using any of these detection methods. These new polyclonal antibodies will be useful in determining the expression, localization, and function of p110 sEGFR, and importantly will allow us to distinguish between the expression of this receptor isoform and p170 EGFR.