New Hybrid Molecular Modalities Comprised of DNA-Origami and Interfering Peptides as Inhibitors of Protein-Protein Interactions

Abstract

Immunotherapy is especially effective in blood cancers and melanoma. However, in solid tumors like breast cancer, immunotherapy typically fails. The tumor microenvironment (TME) has been implicated in playing a major role in the molecular crosstalk that suppresses the immune response against tumors, promoting tumor tolerance, disease progression, and metastasis. ST2/IL-33 signaling from myeloid-derived suppressor cells (MDSCs) is one example of a factor that contributes to immunotherapy failure. ST2/IL-33 signaling activation requires the recruitment of IL-1RAcP, forming a transient ternary complex that initiates the MyD88 cascade. By inhibiting this interaction with the ST2/IL-33 binary complex, it may be possible to foster an environment conducive to antitumor immune events. Here we demonstrate small peptides can inhibit IL-1 RAcP through western blotting and have determined the KD of the final ternary complex for comparison with the KD of the inhibitory peptides. Surface Plasmon Resonance (SPR) was used to measure the affinity of the trimer. The receptor accessory protein has a weaker affinity for the binary ST2/IL-33 complex than ST2 for IL-33 itself. Of the three hotspot-mimicking peptides, Peptide 3 showed the highest activity in isolation, but treatment with the ensemble of all three peptides was the most efficacious even in cell models. Future work will include further optimization of the peptides and ligation to a stabilizing DNA scaffold to build a multivalent inhibitor.