Generation and characterization of peptide mimotopes specific for anti ErbB-2 monoclonal antibodies

Abstract

The erbb-2 gene receptor is often over-expressed in human cancer and its overexpression is accompanied by worse prognosis. Targeting erbb-2 gene with antibodies is an effective approach to curtail the progression of erbb-2 gene-expressing cancer types. Two monoclonal antibodies, L-26 and N-12, previously generated in our laboratory, have shown effective tumor inhibition in mice, especially when used in combination. Here, we describe novel peptide mimics of erbb-2 gene protein epitopes, also called mimotopes, that were selected from a constraint random 12-mer peptide phage library, specific for the antibodies L-26 and N-12. Initial sequencing analyses revealed little sequence conservation among the peptide mimotopes, and no sequence homology with the erbb-2 gene protein. However, computational analyses of the two groups of peptides, specific for L-26 and N-12, suggested different epitopes on the erbb-2 gene extracellular domain. In vitro assays showed that the phage displayed peptide mimotopes were specific to their respective antibodies. Selected cyclic peptide mimotopes, but not their corresponding linear equivalents, were able to inhibit binding of the antibodies L-26 and N-12 to the surface of erbb-2 gene-expressing cancer cells in a concentration-dependent manner. In line with this observation, phage-displayed cyclic peptides successfully competed in vitro with recombinant erbb-2 gene protein for binding to their respective antibodies L-26 or N-12. Consistent with the antibody inhibition experiments, we detected specific anti-erbb-2 gene antibodies following vaccination with KLH-coupled cyclic peptides but not with multiple antigenic linear peptides. Potentially, the selected peptides could serve as a starting point for the development of a vaccine against erbb-2 gene over-expressing cancer.

Anti-metastatic effect of the TM4SF5-specific peptide vaccine and humanized monoclonal antibody on colon cancer in a mouse lung metastasis model

“…In fact, the advantages of cyclic peptides over linear peptides in cancer management have been shown previously [23–25]. Cyclic peptides named mimotopes were generated and proved to be more effective than linear epitopes in establishment of anti-ErbB-2 monoclonal antibodies [23].…”

“…Cyclic peptides named mimotopes were generated and proved to be more effective than linear epitopes in establishment of anti-ErbB-2 monoclonal antibodies [23]. Cyclic peptides, of which the structure is similar to paclitaxel, efficaciously induced apoptosis in many cancer cell lines [24].…”

Epitope mapping of epidermal growth factor receptor (EGFR) monoclonal antibody and induction of growth-inhibitory polyclonal antibodies by vaccination with EGFR mimotope

“…B cell epitopes are usually conformational and their structure predictions are based on crystallography methods and computational estimates with their considerable difficulties 28 . In this regard, phage display is a fascinating technique to find mimetic peptides with identical characteristics of the natural antibody epitope but not necessarily the same protein sequence as the original antigen 29,30 . These so called mimotopes can be used as vaccine in related cancers.…”

“…However, it is known that the epitope of an antibody and its isotope plays the main role in eliciting an immune response. Witsch et al 29 also isolated mimotope of ErbB-2 protein epitopes, from a constraint random 12-mer peptide phage library, specific for the antibodies L-26 and N-12. No sequence homology was reported among the mimotopes with the ErbB-2 gene protein.…”

Anti-angiogenic peptides application in cancer therapy; a review

“…In addition, they are more cost-effective than mAbs because they linger the immune responses and require only a low dose to achieve the therapeutic goal. Also, the administration of mimotopes in comparison to mAbs has special advantages for the induction of specific endogenous immune responses ( 17 18 19 ).…”