PGE2-mediated NK cell reprogramming drives acquired immunotherapy resistance in lung adenocarcinoma

Acquired resistance limits the durability of programmed cell death protein-1 (PD-1) blockade in lung adenocarcinoma, yet the tumor-intrinsic programs and immune circuits that drive acquired resistance relapse remain poorly defined. The purpose of this study was to identify tumor-intrinsic mediators of acquired resistance and determine how they remodel antitumor immunity.

An orthotopic bioluminescence-tracked Lewis lung carcinoma (LLC1) lung adenocarcinoma model was established in immunocompetent mice treated with anti-PD-1. Tumor-intrinsic regulators were identified by an in vivo genome-wide CRISPR loss-of-function screen and validated using inducible tetracycline-off knockdown. Prostaglandin E2 (PGE2) signaling was interrogated through tumor-cell Ptgs2 knockdown/deletion, 16,16-dimethyl PGE2 administration, selective EP2/EP4 antagonists, and celecoxib treatment. Natural killer (NK)-cell function was analyzed by flow cytometry, immunofluorescence, RNA sequencing, cAMP measurement, calcium flux assays, mouse and human NK-cell co-culture cytotoxicity assays, and NK-cell adoptive transfer. Celecoxib was used to evaluate the therapeutic potential of pharmacologic PGE2 blockade in vivo. Public immunotherapy datasets were analyzed to assess the clinical relevance of PTGS2.

The orthotopic LLC1 model captured key features of heterogeneous anti-PD-1 responses, including relapse after initial regression. The CRISPR screen identified Ptgs2 as a key driver of acquired resistance. Tumor-derived PGE2 progressively increased in resistant tumors, and its genetic silencing overcame resistance by restoring NK-cell infiltration and function. Mechanistically, PGE2 signaled through EP2/EP4 receptors to elevate cAMP and induce CREM, thereby suppressing NK-cell cytotoxicity and cytokine production. This axis was validated in human NK cells. Pharmacologic inhibition of cyclooxygenase-2 with celecoxib reversed acquired resistance, an effect abrogated by NK-cell depletion.

Tumor-derived PGE2 is an important contributor to acquired resistance to PD-1 blockade in lung adenocarcinoma. Therapeutic disruption of the EP2/EP4-cAMP-CREM axis restores NK-cell function and overcomes acquired resistance.