부산대학교 도서관

Transforming growth factor alpha (TGF[alpha]) is a potent ligand of the epidermal growth factor receptor (EGFR). EGFR is frequently over-expressed in epithelial tumors and endogenous ligands, mostly TGF[alpha], are frequently co-expressed with EGFR, potentially resulting in autocrine stimulation of tumor cell growth. Therefore, different therapeutic approaches aim for the inactivation of TGF[alpha]/EGF/EGFR signaling system, but no approach is based on TGF[alpha] as a target. The principal goal of this work was to assess the potential of an active specific immunotherapy approach to block the TGF[alpha]/EGFR autocrine loop. For the proof of the concept, a fusion protein between human TGF[alpha] (hTGF[alpha]) and P64k protein from Neisseria meningitidis was generated, and its immunogenicity characterized in a mouse model using different adjuvants. All immunogens were effective for the generation of specific humoral responses against hTGF[alpha]. The inmunodominant epitope of hTGF[alpha] when immunizing mice with the fusion protein involved the C-loop/C-terminal region. This region includes key residues for hTGF[alpha] binding to EGFR. The anti-hTGF[alpha] immune mice sera recognized the natural hTGF[alpha] precursor in A431 cells and hTGF[alpha]-transfected 3T3 fibroblasts as revealed by flow cytometry analysis and immunoblotting. They inhibited the binding of 125.sup.I-TGF[alpha] to the EGFR, EGFR-autophosphorylation, and downstream activation of MAP kinases as well as proliferation of two EGFR-expressing human carcinoma cell lines. These data suggest that EGFR signaling activation by the hTGF[alpha] autocrine loop may be inhibited in vivo by induction of specifically blocking antibodies. The fusion protein reported in this paper could be a potential immunogen for the development of a new cancer vaccine.