Chaperone-derived Cu(I)-binding peptide nanofibers disrupt copper homeostasis in cancer cells

Copper (Cu) is a transition metal that plays crucial roles in the human cellular metabolism. Cu+ homeostasis is upregulated in many cancers and contributes to tumorigenesis. However, therapeutic strategies to target Cu+ homeostasis of cancer cells are rarely explored because small molecule Cu+ chelators have poor binding affinity in comparison to the intracellular Cu+ chaperons, enzymes, or ligands. To address this challenge, we introduce a Cu+ chaperon-inspired supramolecular approach to disrupt Cu+ homeostasis in cancer cells that induces programmed cell death. The Nap-FFMTCGGCR peptide self-assembles into nanofibers inside cancer cells with high binding affinity and selectivity for Cu+ due to the presence of the unique MT/CGGC peptide motif, which is conserved in u+ binding intracellular proteins. Nap-FFMTCGGCR exhibits cytotoxicity towards triple negative breast cancer cell lines (MDA-MB-231), impairs the activity of Cu+-dependent co-chaperon super oxide dismutase 1 (SOD1) and induces overproduction of reactive oxygen species (ROS) to initiate apoptosis. In contrast, Nap-FFMTCGGCR has minimal impact on normal HEK 293T cells. Control peptides show that the self-assembly and Cu+ binding properties must work in synergy to successfully disrupt Cu+ homeostasis. We show that assembly-enhanced affinity for metal ions opens new therapeutic strategies to address disease-relevant metal ion homeostasis.