LAUSR

The tumor-intrinsic NOD-, LRR- and pyrin domain-containing protein-3 (NLRP3) inflammasome–heat shock protein 70 (HSP70) signaling axis is triggered by CD8+ T cell cytotoxicity and contributes to the development of adaptive resistance to anti–programmed cell death protein 1 (PD-1) immunotherapy by recruiting granulocytic polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs) into the tumor microenvironment. Here, we demonstrate that the tumor NLRP3-HSP70 axis also drives the accumulation of PMN-MDSCs into distant lung tissues in a manner that depends on lung epithelial cell Toll-like receptor 4 (TLR4) signaling, establishing a premetastatic niche that supports disease hyperprogression in response to anti–PD-1 immunotherapy. Lung epithelial HSP70-TLR4 signaling induces the downstream Wnt5a-dependent release of granulocyte colony-stimulating factor (G-CSF) and C-X-C motif chemokine ligand 5 (CXCL5), thus promoting myeloid granulopoiesis and recruitment of PMN-MDSCs into pulmonary tissues. Treatment with anti–PD-1 immunotherapy enhanced the activation of this pathway through immunologic pressure and drove disease progression in the setting of Nlrp3 amplification. Genetic and pharmacologic inhibition of NLRP3 and HSP70 blocked PMN-MDSC accumulation in the lung in response to anti–PD-1 therapy and suppressed metastatic progression in preclinical models of melanoma and breast cancer. Elevated baseline concentrations of plasma HSP70 and evidence of NLRP3 signaling activity in tumor tissue specimens correlated with the development of disease hyperprogression and inferior survival in patients with stage IV melanoma undergoing anti–PD-1 immunotherapy. Together, this work describes a pathogenic mechanism underlying the phenomenon of disease hyperprogression in melanoma and offers candidate targets and markers capable of improving the management of patients with melanoma. Description The tumor-intrinsic NLRP3 inflammasome-HSP70-TLR4 axis promotes distant metastatic progression in response to anti-PD-1 immunotherapy. Preventing progression A subset of patients with melanoma treated with PD-1 blockade develop hyperprogression, where disease progresses more rapidly after treatment. Here, Theivanthiran et al. aimed to determine the mechanism by which this phenomenon occurs. The authors found that a NLRP3 inflammasome–HSP70-TLR4 signaling axis drove premetastatic niche development in the lungs of mice with melanoma and that this was further enhanced by PD-1 blockade. These in vivo findings mirrored what the authors observed in patients with melanoma, where tumor NLRP3 activity correlated with hyperprogression. Genetic ablation or pharmacological inhibition of this signaling axis suppressed metastasis in mice, suggesting that this axis merits further investigation as a clinical target.—CM.