RECEPTOR

THE EPIDERMAL GROWTH FACTOR RECEPTOR IS A 170,000 DALTON GLYCOPROTEIN COMPOSED OF THREE DOMAINS. THE CELL SURFACE DOMAIN BINDS EPIDERMAL GROWTH FACTOR (EGF) AND A LOW MOLECULAR WEIGHT, TUMOR-SPECIFIC GROWTH FACTOR (TGF ALPHA). AUTOCRINE STIMULATION OF THE EGF RECEPTOR OCCURS WHEN THE SAME TUMOR CELL POSSESSES EGF RECEPTORS AND PRODUCES TGF ALPHA. THE RECEPTOR HAS A HYDROPHOBIC MEMBRANE-SPANNING DOMAIN CONNECTING THE CELL SURFACE REGION WITH THE INTRA- CELLULAR TRYOSINE-SPECIFIC PROTEIN KINASE DOMAIN. THE EGF RECEPTOR SHARES REGIONS OF PRIMARY SEQUENCE HOMOLOGY WITH THE SRC FAMILY OF PROTEIN KINASES AND MOST CLOSELY RESEMBLESTHE V-ERB-B AND NEU GENES. EGF RECEPTOR AMPLIFICATION HAS BEEN DEMONSTRATED IN THE A431 CARCINOMA CELL LINE, RAISING THE POSSIBILITY THAT ELEVATED OR ABERRANT EGF RECEPTOR EXPRESSION MAY REPRESENT A DIAGNOSTICALLY USEFUL FEATURE OF CERTAIN CLASSES OF HUMAN CANCERS. IN THIS PHASE I PROJECT, METHODS WILL BE DEVELOPED FOR PREPARATIVE ISOLATION OF HUMANEGF RECEPTOR FROM A431 CELLS USING RICIN B CHAIN, ION EXCHANGE, AND EGF AFFINITY CHROMATOGRAPHY. THE PROTEIN KINASE C PHOSPHORYLATION SUBSTRATE SEQUENCE FLANKING THREONINE 654 WILL BE PRODUCED BY SOLID-PHASE PEPTIDE SYNTHESIS. MICE WILL BE IMMUNIZED, HYPERIMMUNE SERA PRODUCED, AND HYBRIDOMA FUSIONS INITIATED. FUTURE PHASE II EXPERIMENTS WILL BE DESIGNED TO DEVELOP PANELS OF MONOCLONALANTIBODIES TO BOTH NATIVE AND FORMALIN FIXED EGF RECEPTORS. THESE WILL BE ANALYZED FOR POTENTIAL USE IN HISTOPATHOLOGY, IN VIVO IMAGING, AND A SERUM-BASED ANTIGEN CAPTURE TEST FOR RECEPTOR PROTEIN.