Prostaglandin E_₂ Impacts Multiple Stages of the Natural Killer Cell Anti-Tumor Immune Response

Tumor immune escape is a major factor contributing to cancer progression and unresponsiveness to cancer therapies. Tumors can produce prostaglandin E₂ (PGE₂), an inflammatory mediator that directly acts on Natural killer (NK) cells to inhibit anti-tumor immunity. However, precisely how PGE₂ influences NK cell tumor-restraining functions remains unclear. Here, we report that following PGE_₂
treatment, human NK cells exhibited altered expression of specific activating receptors and a reduced ability to degranulate and kill cancer targets. Transcriptional analysis uncovered that PGE_₂ also differentially modulated the expression of chemokine receptors by NK cells, inhibiting CXCR3 but increasing CXCR4. Consistent with this, PGE_₂-treated NK cells exhibited decreased migration to CXCL10 but increased ability to migrate towards CXCL12. Using live cell imaging, we showed that in presence of PGE2, NK cells were slower and less likely to kill cancer target cells following conjugation. Imaging the sequential stages of NK cell killing revealed that PGE_₂ impaired NK cell polarization, but not the re-organization of synaptic actin or the release of perforin itself. Together, these findings demonstrate that PGE₂ affects multiple but select NK cell functions. Understanding how cancer cells subvert NK cells is necessary to more effectively harness the cancer-inhibitory function of NK cells in treatments.