Chemical Biology
Tumor targeting
Oligoproline-based hybrid ligands
Tumor targeting with radiolabeled ligands that bind selectively to receptors overexpressed on cancer cells is valuable for tumor imaging and therapy. Yet, current ligands typically suffer from either low internalization into tumor cells (agonists) or high wash-out since they only bind to the receptors (antagonists).
We use azidoproline containing oligoprolines as functionalizable molecular scaffolds that allow for combining agonists with antagonists in defined distances. Our group showed that hybrid ligands consisting of a bombesin-based agonist and antagonist as recognition motifs exhibit extraordinary tumor uptake properties in prostate carcinoma. The oligoproline scaffold allowed for distance control between the agonist and the antagonist and revealed that hybrid ligands with 20 Å spacing have significantly higher tumor uptakes in vitro and in vivo compared to monovalent and divalent controls.
Based on these findings we are now designing oligoproline-based ligands to expand the method to targeting other cancer types and to achieve a deeper understanding of how the uptake takes place on the molecular and cellular level.
C. Kroll, R. Mansi, F. Braun, S. Dobitz, H. Maecke, H. Wennemers, "Hybrid Bombesin Analogues – Combining an Agonist and an Antagonist in Defined Distances for Optimized Tumor Targeting"
J. Am. Chem. Soc. 2013, 135, 16793–16796
Peptide-coated metal nanoparticles
Peptide H‐Lys‐Pro‐Gly‐DLys‐NH2 was identified by screening of a combinatorial library and further optimized to a heptapeptide H‐Lys‐[Pro‐Gly‐DLys]2‐NH2 which enabled the formation of water‐soluble, monodisperse PtNPs with average diameters of 2.5 nm that are stable for years. The peptide‐coated PtNPs were shown to be highly toxic against hepatic cancer cells but did not affect the viability of other cancer or non‐cancerous cells to nearly the same extent. To the best of our knowledge, these PtNPs have the highest cytotoxicity combined with selectivity for hepatic cancer cells achieved thus far. Cellular uptake combined with cell viability studies revealed that the combination of high cellular uptake and an oxidative environment of the cancer cells is key for the cytotoxicity of the PtNPs. Our results open exciting prospects for the development of PtNP‐based therapeutics.
(for more information on our metal nanoparticle research please click here)
M. S. Shoshan, T. Vonderach, B. Hattendorf, H. Wennemers "Peptide‐coated Platinum Nanoparticles with Selective Toxicity against Liver Cancer Cells”
Angew. Chem. Int. Ed. 2019, asap
Cell-penetrating peptides
Cell‐penetrating peptides (CPPs) are a promising tool for non‐invasive delivery of therapeutic or diagnostic molecules into mammalian cells. Inspired by the HIV‐entry peptide Tat and oligoarginines, numerous cationic CPPs have been developed as molecular transporters. These studies showed that the number and spatial array of cationic groups are key to cellular uptake. Yet, the structural prerequisites for cellular uptake and intracellular localization are still not well‐understood and limit the design of more efficient CPPs.
We have demonstrated that preorganization of cationic charges in distances of 9Å along oligoproline backbone enhanced the cellular uptake of these CPPs into various cancer cells (HeLa, MCF‐7, and HT‐29) compared to more flexible oligoarginines with undefined charge display. We also showed that the higher cellular entry of the CPPs with preorganized positive charges correlates with their higher binding affinity to anionic cell‐surface glycans. In addition, a defined nuclear localization of cationic oligoprolines and high proteolytic stability as well as low cytotoxicity was observed.
We are currently further investigating cationic oligoprolines as tools for delivery of cargo into cells.
Y. A. Nagel,* P. S. Raschle,* H. Wennemers "Effect of Preorganized Charge Display on the Cell Penetrating Properties of Cationic Peptides”
Angew. Chem. Int. Ed. 2017, 56, 122 – 126
Nucleotide-binding-peptides
Bis‐(3′,5′)‐cyclic dimeric guanosine monophosphate (c‐di‐GMP) is an important signaling molecule in bacteria. Since c‐di‐GMP has only been observed in bacteria and simple eukaryotes but not in higher‐order organisms, it is an attractive target for the fight against bacterial infections. However, the development of selective binders of c‐di‐GMP is difficult and consequently most efforts towards therapeutically active compounds have focused on interfering with protein regulators of c‐di‐GMP rather than targeting the messenger molecule itself.
We have shown that short proline‐rich peptides bearing cationic and aromatic groups bind the bacterial second messenger c‐di‐GMP selectively over closely related nucleotides with binding affinities in water in the micromolar range. In addition, the peptides were found to inhibit the formation of biofilms by the opportunistic pathogen P. aeruginosa. Spectroscopic, molecular modeling, and SAR studies revealed that the binding is driven by a combination of π–π stacking, H‐bonding, and electrostatic interactions between the peptide and c‐di‐GMP. These are the first examples of short peptides that bind c‐di‐GMP selectively and result in a phenotypic response in bacteria.
Based on the above findings we are currently investigating the possibility to bind other relevant nucleotide and non-nucleotide targets with short peptide receptors.
C. Foletti, R. A. Kramer, H. Mauser, U. Jenal, K. H. Bleicher, H. Wennemers "Functionalized Proline-Rich Peptides Bind the Bacterial Second Messenger c-di-GMP”
Angew. Chem. Int. Ed. 2018, 57, 7729-7733
Synthetic Collagen
Research in the Wennemers group led to a “toolkit” of functionalizable synthetic collagen model peptides (CMPs) that have different propensities for self-assembly into collagen triple helices. Moreover, we have utilized this knowledge to establish pH-responsive synthetic collagen (for more details on this research please click here). Based on this versatility, we can finetune our synthetic CMPs towards tackling challenges in tissue engineering and wound healing. In particular, we envision creating CMPs that can 1) influence the growth and protein expression of fibroblasts, 2) modify the mechanical properties of collagenous tissue, and 3) integrate into wounds and promote the repair process.