Dynamic single-cell RNA sequencing identifies immunotherapy persister cells following PD-1 blockade

Resistance to oncogene-targeted therapies involves discrete drug-tolerant persister cells, originally discovered through in vitro assays. Whether a similar phenomenon limits efficacy of programmed death (PD)-1 blockade is poorly understood. Here, we performed dynamic single-cell RNA sequencing of murine organotypic tumor spheroids undergoing PD-1 blockade, identifying a discrete sub-population of immunotherapy persister cells (IPCs) that resisted CD8 T-cell mediated killing. These cells expressed Snai1 and stem cell antigen-1 (Sca-1), and exhibited hybrid epithelial-mesenchymal features characteristic of a stem cell-like state. IPCs were expanded by interleukin-6 (IL-6) but were vulnerable to tumor necrosis factor-alpha (TNF-α)-induced cytotoxicity, relying on Birc2 and Birc3 as survival factors. Combining PD-1 blockade with Birc2/3 antagonism in mice reduced IPCs and enhanced tumor cell killing in vivo, resulting in durable responsiveness that matched TNF cytotoxicity thresholds in vitro. Together, these data demonstrate the power of high-resolution functional ex vivo profiling to uncover fundamental mechanisms of immune escape from durable anti-PD-1 responses, while identifying IPCs as a cancer cell subpopulation targetable by specific therapeutic combinations.