Cancer Susceptibility to Stapled Oncolytic Peptides is Dictated by Membrane Cholesterol and Inflammatory Signaling

Relapsed and refractory cancers effectively overcome diverse modalities of cancer treatment, whose principal targets are nucleic acids and proteins. The plasma membranes of cancer cells represent an alternative and underutilized target, with the potential for membrane lysis to induce a rapid, pro-inflammatory cell death that circumvents the challenges of intratumor heterogeneity and immune evasion. Here, we repurposed StAMP51.2, a stapled Magainin II peptide previously optimized for selective membrane lysis of gram-negative bacteria, to target cancer cell membranes. Using PRISM, a high throughput cancer cytotoxicity screen, we identified cancer cells most vulnerable to StAMP51.2 and biomarkers of susceptibility, specifically reduced cholesteryl esters and elevated triacylglycerols. We validated this signature in a pair of sensitive (OCI-AML3) and resistant (K562) leukemia cell lines, correlating their differential responses to distinct lipidomic profiles. Susceptibility of OCI-AML3 cells in culture extended to the in vivo context, where StAMP51.2 suppressed leukemic growth in orthotopic and intraperitoneal models. To further characterize the mechanism of action, we undertook the challenge of generating StAMP51.2-resistant OCI-AML3 cells, which required four months of low-level exposure. Strikingly, drug-resistant OCI-AML3 cells recapitulated the lipidomic phenotype of naturally-resistant K562 cells. Transcriptomic analyses further revealed that lipid reprogramming was accompanied by pervasive downregulation of inflammatory signaling. Thus, in advancing StAMP51.2 as an oncolytic prototype, we uncovered an immune regulatory axis that links membrane integrity to inflammatory signaling.