Design, synthesis, and characterization of anti-estrogenic and anti-breast cancer alpha-fetoprotein-derived peptides

The null hypothesis of this thesis is that the native primary and secondary structures of existing peptide AFP_447–480 are necessary for the antiestrotrophic and anti-oncotic activities associated with the peptide. This hypothesis was tested by completing the following three specific aims: The first specific aim was to determine which structural features of AFP_447–480 contribute to its aggregation and loss of activity. The second specific aim was to design, produce, and characterize analogs of AFP_447–480 with the goal of enhancing structural stability and preventing the loss of biological activity that occurs during storage. The third specific aim was to determine whether smaller segments of this 34-mer peptide retain biological activity with the goal of identifying the minimal active sequence.; Circular dichroism spectroscopy, gel-filtration chromatography, mass spectrometry, and amino acid analysis were used for physical characterization of the synthetic peptides.; A number of 34-mer peptide analogs were designed to prevent possible disulfide bond formation and beta-sheet formation and were synthesized in attempt to generate an agent that would be stable during storage. These analogs included AFP_{447–480 (C455A, C468A)}, AFP_{447–480 (C455G, C468G)}, AFP_{447–480 (C455S, C468S)}, AFP _{447–480 (C455D, C468D)}, and AFP_{447–480 (C455P, I463P, C468P)}.; Several shorter peptides, including an 8-mer called AFP_472–479 (amino acids 472–479, peptide sequence EMTPVNPG) retained activity, whereas peptides shorter than eight amino acid residues were inactive.; Physical characterization of octapeptide AFP_472–479 indicated that the peptide aggregated during storage to form inactive species.; These data show that octapeptide EMTOVNOG and cyclo-(EMTOVNOGQ), which have approximately 1/3 the size of the original 34-mer peptide, are superior to the parent 34-mer peptide AFP_447–480 with respect to structural stability, biological activity, and shelf life. These peptides, or peptidomimetics designed therefrom, may become novel agents for the treatment or even prevention of breast cancer. (Abstract shortened by UMI.)...