Endocrine Abstracts

Oestradiol-17β regulates diverse tissues and cells, both within and outside the reproductive system including human cancer cells. Currently used ERs agonists or antagonists are synthetic compounds prepared by structure modifications. Alternatively, peptide mimics of steroids would allow preparation of biased combinatorial libraries of chemical and biological origin, from which estrogenic peptides with tissue selective profiles can be selected. The phage-display peptide library may offer a suitable way to obtain peptides that mimic E2 biological activity. These libraries are diverse collections of random peptides displayed on the surface of filamentous phages, which can be screened for binding to a target molecule, such as an antibody or receptor. These combinatorial peptide libraries have not been used to isolate peptides that mimic the activity of organic compounds such as steroids. Here we report the development of peptides with oestrogen-like activity. We employed a novel approach utilizing a monoclonal antibody against oestradiol (mAb E2-15) to screen a 15-mer phage-display peptide library and to affinity select phage that interacted with mAb E2-15. Synthesis of such peptides resulted in the identification of a 15-mer linear peptide which interacted specifically with mAb E2-15. Incorporation of flanking -residues at the N-terminus and the C-terminus of the peptide, resulted with peptides recognized specifically mAb E2-15 and ERα. The peptides A44 (KAWFFE), A45 (KRAFFE), EMP-1 (VSWFFE), EMP-2, and cyclic peptide (23mer) stimulated DNA and CK in ‘endocrine’ and ‘non-endocrine’ human cancer cell lines. In ovarian cancer A2780, only EMP1 and EMP2 induced CK whereas 23mer inhibited it. In prostate cancer C4-24 CK was induced by all peptides tested. In colon cancer 320D, CK was induced by all except EMP2 and in adrenal carcinoma H295R all peptides except EMP1 stimulated CK. In A2780 DNA was stimulated by EMP1 and EMP2 but inhibited by A44 and mer23. In C4-24 and in 320D all peptides except EMP2 stimulated DNA. In H295R DNA synthesis was stimulated by all peptides except EMP1. All cells tested expressed ERα, ERβ and VDR to different levels. These mRNAs were variably affected by oestrogens. In conclusion, some of these peptides can be lead compounds for the effects on human cancer cells and might be targets for chemical modifications leading to development of inhibitors of growth of these cancer cells.