Linear peptide analogs of AFPep are potential anticancer agents.

B87

Purpose : Cyclo [EKTOVNOGN] (AFPep), a cyclic peptide derived from the active site of alpha-fetoprotein, has been shown to prevent breast cancer in animal models. This peptide is comprised of 9 amino acids in cyclic head-to-tail peptide linkage. Previous synthetic studies suggested that the pharmacophore consisted of OVNO, while replica exchange molecular dynamics suggested that the pharmacophore consisted of TOVN. We hypothesized that smaller analogs of AFPep, especially those that include OVN, would be effective anticancer agents. Experimental Design : Twelve linear AFPep analogs were assembled on PAL-PEG-PS resin beginning with the C-terminus using N-terminally protected amino acids. These peptides were either four or five amino acids long, and were designed to resemble the putative pharmacophoric region of AFPep. An unrelated five amino acid peptide (PGVGQ) was synthesized as a negative control, and AFPep was used as a positive control. These peptides were evaluated using an immature mouse uterine growth inhibition assay (for antiestrogenicity) and a T47D breast cancer cell proliferation assay (for anticancer activity). Results and Conclusions : Linear analogs of AFPep were synthesized; mass spectrometry showed that each peptide was of the correct molecular weight. Inhibition of uterine growth was as follows: TOVNO (31± 2%), TOVN (23±2%), OVNO (9 ± 4%), OVNOG (21± 4%), KTOVN (28± 5%), TPVNP (27± 1%), TPVN (29±2%), PVNP (9±2%), EKTPV (0%), EMTPV (11%), EMTOV (0%), and VNOG (0%) compared to AFPep (38±2%) and PGVGQ (0%). Inhibition of E₂-stimulated T47D cell growth was as follows: TOVNO (41±10%), OVNO (10%), and OVNOG (47%) compared to AFPep (53±6%) and PGVGQ (11%). We concluded that analogs of AFPep as small as 4 or 5 amino acids are effective antiestrotrophic and anticancer agents. OVNO is of low biological activity, whereas TOVN may be, and TOVNO is, biologically active.