The enlargement of the hormone immune deprivation concept to the blocking of TGFα-autocrine loop: EGFR signaling inhibition

Abstract

Transforming growth factor alpha (TGFalpha) is a potent ligand of the epidermal growth factor receptor (EGFR). EGFR is frequently over-expressed in epithelial tumors and endogenous ligands, mostly TGFalpha, are frequently co-expressed with EGFR, potentially resulting in autocrine stimulation of tumor cell growth. Therefore, different therapeutic approaches aim for the inactivation of TGFalpha/EGF/EGFR signaling system, but no approach is based on TGFalpha as a target. The principal goal of this work was to assess the potential of an active specific immunotherapy approach to block the TGFalpha/EGFR autocrine loop. For the proof of the concept, a fusion protein between human TGFalpha (hTGFalpha) 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 hTGFalpha. The inmunodominant epitope of hTGFalpha when immunizing mice with the fusion protein involved the C-loop/C-terminal region. This region includes key residues for hTGFalpha binding to EGFR. The anti-hTGFalpha immune mice sera recognized the natural hTGFalpha precursor in A431 cells and hTGFalpha-transfected 3T3 fibroblasts as revealed by flow cytometry analysis and immunoblotting. They inhibited the binding of (125)I-TGFalpha 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 hTGFalpha 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.

Effective Inhibition of the Epidermal Growth Factor/Epidermal Growth Factor Receptor Binding by Anti–Epidermal Growth Factor Antibodies Is Related to Better Survival in Advanced Non–Small-Cell Lung Cancer Patients Treated with the Epidermal Growth Factor Cancer Vaccine

“…This suggests the necessity of a complementary vaccine with TGFa as immunogen. Our group is already evaluating a TGFa-based vaccine in the preclinical setting (10).…”

“…A cancer vaccine based on an immunogenic conjugate of human EGF is currently in clinical trials. 4 Additionally, recent preclinical studies to asses the potential of an active specific immunotherapy approach to block the TGFa/EGFR autocrine loop have been reported (10). Our group also obtained a TGFa fusion protein that could be a potential immunogen for the development of a new cancer vaccine.…”

Cancer Vaccines for Hormone/Growth Factor Immune Deprivation:A Feasible Approach for Cancer Treatment

“…A vaccine, targeting TGFα and intending to block the TGFα/EGFR autocrine loop, is currently in pre-clinical testing in our laboratories [25]. It consists of a recombinant fusion Fig.…”

“…This region includes key residues for TGFα binding to EGFR. Mice immune sera recognized natural hTGFα precursor in A431 cells and in hTGFα-transfected 3T3 fibroblasts, as revealed by flow citometry analysis [25].…”

“…Active immunotherapy, targeting growth factors and their receptors, is conceptually equivalent to signal transduction drugs, but may offer better specificity [18][19][20][21][22][23][24][25].…”