A network of interacting proteins controls the activity of cyclin-dependent kinase 2 (Cdk2) (refs 1,2) and governs the entry of higher eukaryotic cells into S phase. Analysis of this and other genetic regulatory networks would be facilitated by intracellular reagents that recognize specific targets and inhibit specific network connections. We report here the expression of a combinatorial library of constrained 20-residue peptides displayed by the active-site loop of Escherichia coli thioredoxin, and the use of a two-hybrid system to select those that bind human Cdk2. These peptide aptamers were designed to mimic the recognition function of the complementarity-determining regions of immunoglobulins. The aptamers recognized different epitopes on the Cdk2 surface with equilibrium dissociation constant in the nanomolar range; those tested inhibited Cdk2 activity. Our results show that peptide aptamers bear some analogies with monoclonal antibodies, with the advantages that they are isolated together with their coding genes, that their small size should allow their structures to be solved, and that they are designated to function inside cells.

Postoperative ileus (POI) is a major focus of concern for surgeons because it increases duration of hospitalization, cost of care, and postoperative morbidity. The definition of POI is relatively consensual albeit with a variable definition of interval to resolution ranging from 2 to 7 days for different authors. This variation, however, leads to non-reproducibility of studies and difficulties in interpreting the results. Certain risk factors for POI, such as male gender, advanced age and major blood loss, have been repeatedly described in the literature. Understanding of the pathophysiology of POI has helped combat and prevent its occurrence. But despite preventive and therapeutic efforts arising from such knowledge, 10 to 30% of patients still develop POI after abdominal surgery. In France, pharmacological prevention is limited by the unavailability of effective drugs. Perioperative nutrition is very important, as well as limitation of preoperative fasting to 6 hours for solid food and 2 hours for liquids, and virtually no fasting in the postoperative period. Coffee and chewing gum also play a preventive role for POI. The advent of laparoscopy has led to a significant improvement in the recovery of gastrointestinal function. Enhanced recovery programs, grouping together all measures for prevention or cure of POI by addressing the mechanisms of POI, has reduced the duration of hospitalization, morbidity and interval to resumption of transit.

The inhibition of heat shock protein 70 (HSP70) is an emerging strategy in cancer therapy. Unfortunately, no specific inhibitors are clinically available. By yeast two-hybrid screening, we have identified multiple peptide aptamers that bind HSP70. When expressed in human tumor cells, two among these peptide aptamers-A8 and A17-which bind to the peptide-binding and the ATP-binding domains of HSP70, respectively, specifically inhibited the chaperone activity, thereby increasing the cells' sensitivity to apoptosis induced by anticancer drugs. The 13-amino acid peptide from the variable region of A17 (called P17) retained the ability to specifically inhibit HSP70 and induced the regression of subcutaneous tumors in vivo after local or systemic injection. This antitumor effect was associated with an important recruitment of macrophages and T lymphocytes into the tumor bed. Altogether, these data indicate that peptide aptamers or peptides that target HSP70 may be considered as novel lead compounds for cancer therapy. Cancer Res; 71(2); 484-95. Ó2011 AACR.