Inhibition of the Pin1 Prolyl Isomerase: A Novel Approach for DNA checkpoint Abrogation in Breast Cancer Cell Lines.

摘要

We examined the hypothesis that the Pin1 prolyl isomerase plays a role in enforcing cell cycle checkpoints associated with DNA damage, and that inhibition of this enzyme would result in abrogation of the checkpoint. A set of synthetic peptides were prepared that would serve as competitive substrate inhibitors of Pin1 prolyl isomerase activity. To facilitate uptake into cells the peptides contained an amino terminal sequence of HIV-1 TAT. Negative and positive control peptides were also examined. We determined the effects of the synthetic peptide inhibitors on cell growth, abrogation of an S-phase checkpoint induced by hydroxyurea treatment, and abrogation of a G2 DNA damage checkpoint induced by bleomycin treatment. We found that none of the synthetic peptides had any affect on cell growth, nor were they effective in abrogating the S-phase checkpoint induced by hydroxyurea. However, a small but reproducible effect on DNA damaged cells was observed. The Pin1 peptide predicted to have the greatest activity induced a more rapid shift of G2 blocked cells into G1 phase after 48- 72 hours following initial bleomycin exposure. Our results do not suggest that the peptide inhibitors examined here have therapeutic potential, but they do show that inhibition of Pin1 may play a role in checkpoint control. A second generation of more active Pin1 inhibitors may provide a new therapeutic approach.