As opposed to its reported role in the innate immune system, NLRP3 inflammasome-mediated regulation of adaptive immune responses to cancer has been less well-described
[30]. Prior work has supported a role for NLRP3 in tumor immunosurveillance, including studies showing the NLRP3 inflammasome to upregulate PD-L1 expression and suppress the generation of T cell responses in diffuse large B cell lymphoma while also driving metastatic progression in the B16/F10 melanoma model by inhibiting NK cell activity
[31][32]. More recent studies have shown systemic pharmacologic inhibition of NLRP3 to increase effector CD8
+ T cells and suppress both CD4
+FoxP3
+ regulatory T cells and CD11b
+Ly6G
+Ly6C
lo PMN-MDSCs in a transgenic
Tgfbr1/Pten 2ccKO model of head and neck squamous cell carcinoma
[33]. These data are also consistent with studies performed in a transgenic p48
Cre;LSL-Kras
G12D model and an orthotopic Pdx1
Cre;LSL-Kras
G12D;Tp53
R172H model of pancreatic cancer, which demonstrated NLRP3 signaling in macrophages to drive M2 polarization and suppress both the activation and infiltration of CD4
+ and CD8
+ T cells in pancreatic tumors
[34]. This data is further in line with findings implicating macrophage NLRP3 signaling to enhance the migration and metastatic progression in models of both colorectal cancer and melanoma
[35][36]. Additional studies have shown NLRP3 expression by MDSCs to mitigate against the anti-tumor properties of 5-fluorouracil chemotherapy in several preclinical tumor models by driving T
H17 development
[37]. Notably, these effects were both found to be IL-1β-dependent. Indeed, many of the described pro-tumorigenic properties of NLRP3 have been attributed to its role in driving the expression of IL-1β by tumor-infiltrating myeloid cells. Studies have shown this process to support the recruitment of other myeloid cells to the tumor bed and promote tumor invasiveness and metastasis in an IL-1β-dependent manner
[36][38]. Indeed, studies have implicated the NLRP3-mediated release of IL-1β in the induction of the IL-22 cytokine by CD4
+ T cells, a process observed to support tumor cell proliferation and growth
[39]. Together, these data are consistent with the findings reported in the CANTOS clinical trial, which was originally designed to examine the impact of the IL-1β antagonistic antibody, canakinumab, on recurrent vascular events in patients with a prior myocardial infarction and persistently elevated C-reactive protein. Remarkably, a re-evaluation of this data revealed a significant decrease in lung cancer incidence (HR 0.33,
p < 0.0001) and lung cancer mortality (HR 0.23,
p = 0.0002) in patients treated with canakinumab relative to placebo
[40].
While several studies have demonstrated IL-1β to generally promote both intrinsic and extrinsic properties of tumorigenesis, including angiogenesis and immune evasion, it is important to also recognize that a role for IL-1β has been described in promoting anti-tumor immunity in specific contexts. This includes a report describing the delivery of systemic IL-1β distant from the tumor site to effectively condition adoptively transferred T cell populations to generate improved anti-tumor immune responses in a B16 melanoma model
[41]. Additional groups utilizing syngeneic murine tumor model systems have reported on the anti-tumor properties of IL-1β
[42][43]. Indeed, IL-1β signaling in dendritic cells has been shown to be critical for the induction of radiation-induced anti-tumor immune responses
[44]. The exact underlying reason for this seemingly discrepant data is generally believed to be associated with the context of IL-1β signaling, while the local concentration and secretion kinetics of IL-1β may also influence downstream outcomes following the activation of this pathway. These disparate results further emphasize the importance of validating pre-clinical data with correlative studies in cancer patients.