Effective allogeneic natural killer cell therapy for pancreatic adenocarcinoma avails conserved activating receptors and evades HLA I-driven inhibition.

backgroundAt diagnosis, ~80% of pancreatic ductal adenocarcinomas (PDAC) have metastasized. Relapse is thus common even among patients who undergo surgical resection, the only curative option. PDAC progresses rapidly, and existing immunotherapies have been ineffective. We hypothesized that natural killer (NK) cell immunotherapies could be effective against PDAC because they recognize conserved and heterogeneous features associated with cellular stress and transformation and can seek out metastases distal to the primary tumor site. Here, we aim to define the key features of NK cells as effective agents for PDAC immunotherapy.

methodsWe used The Cancer Genome Atlas Program (TCGA) PDAC Firehose data and flow cytometry to predict and measure the most common activating or inhibitory ligands available on PDAC for NK cell activation. To ascertain how the tumor might alter expression of these ligands during treatment, inflammation or immune pressure, we measured expression of NK ligands at rest, or after exposure to immune cells or inflammation. To test and rank the functional importance of these dynamic ligands in the recognition, killing and control of PDAC we used co-culture, antibody-blocking and an NK-competent humanized mouse model.

resultsLeveraging the known sequential acquisition of mutations as a surrogate for disease progression, we observed a progressive loss of transcript expression for activating NK cell ligands and chemoattractants. Exposure of PDAC to NK cells or interferon-γ, an inflammatory stimulus, drove dynamic changes in expression of both activating and inhibitory ligands. In vitro co-culture assays revealed a redundancy in the activating receptors engaged in NK:PDAC interactions, but that human leukocyte antigens (HLA)-killer immunoglobulin-like receptors (KIR) signaling dominantly interrupted anti-PDAC activity. In NK-competent humanized mice, adoptively transferred, unselected, unmodified NK cells slowed tumor growth in a dose-dependent manner, but NK cells selected to avoid HLA I-driven inhibition were the most competent effectors for PDAC control.

conclusionsAlthough there is redundancy among activating ligand:receptor pairs for recognizing PDAC tumors, interactions between KIR and HLA define the extent to which antitumor activity can proceed. During tumor progression and in response to immunotherapy, NK:tumor interactions drive upregulation of HLA I molecules. Thus, educated NK cells from HLA I-disparate donors may be the more effective allogeneic NK immunotherapy for PDAC.