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Aberrant activation of the NLR family pyrin domain containing 3 (NLRP3) inflammasome mediates numerous inflammatory diseases. Oncogenes can activate the NLRP3 inflammasome and thereby promote myeloproliferative neoplasia, suggesting a crucial role of NLRP3 in the malignant transformation of hematopoietic cells. Here, we show that bone marrow-derived mononuclear cells of AML patients display enhanced expression of NLRP3, IL-1β and IL-18 and that high-level expression of NLRP3 is linked to poor survival of AML patients. Pharmacological and genetic inhibition of NLRP3 inflammasome activation attenuated cell proliferation of MOLM-13 AML cells in vitro. In vivo, genetic inhibition of NLRP3 in MOLM-13 AML cells resulted in reduced engraftment potential in xenografts, along with reduced splenomegaly and organ infiltration. Differential proteomic analysis revealed the eIF2 pathway as potential target of NLRP3 in AML, with a significant increase of eIF2α phosphorylation upon NLRP3 inhibition. NLRP3 inhibition also caused a strong decrease in cyclin – dependent kinases CDK4 and CDK6, accompanied by an upregulation of the CDK inhibitor p21 (CDKN1A) and a marked arrest of cell cycle progression in the G0/G1 phase, consistent with the role of eIF2α phosphorylation as negative cell cycle regulator.Taken together, we show that inhibition of the NLRP3 inflammasome reduces AML cell proliferation by promoting eIF2α phosphorylation, which in turn enhances the expression of cell cycle arrest genes such as p21. Thus, the study uncovers the NLRP3/eIF2 axis as new driver of AML proliferation and proposes a novel therapeutic treatment of AML by targeted inhibition of NLRP3 activation.

Pharmacological targeting of Hedgehog (HH)/GLI has proven effective for certain blood, brain and skin cancers including basal cell carcinoma (BCC). However, limited response rates and the development of drug resistance call for improved anti-HH therapies that take into account synergistic crosstalk mechanisms and immune evasion strategies.In previous work, we demonstrated that crosstalk of HH/GLI with pro-inflammatory Interleukin-6 (IL6) signaling drives BCC by promoting tumor cell proliferation [1]. In the present study, we screened for possible mechanisms of cancer immune evasion regulated by synergistic HH-IL6 signaling and identified the immunosuppressive enzyme indoleamine 2,3-dioxygenase 1 (IDO1) as a novel transcriptional target co-regulated by HH-IL6 signaling. Analysis of thecis-regulatory region of IDO1 by chromatin-immunoprecipitation revealed co-occupancy of this region by HH- IL6 induced GLI1 and STAT3 transcription factors along with active chromatin marks at the histone level. Elevated expression of IDO1 in human BCC with high-level HH and IL6 signatures supports the clinical relevance of our mechanistic data. Genetic inhibition of GLI1 expression prevented the induction of IDO1 expression in response to IL6/STAT3 and IFNγ/STAT1 signaling in human melanoma cells. Pharmacological targeting of HH signaling at the level of GLI proteins interfered with IDO1 expression and consequently prevented the production of the immunosuppressive metabolite kynurenine generated by active IDO1 from tryptophan. Further, inhibition of GLI1 enhanced the efficacy of the selective IDO1 inhibitor epacadostat. Of note, inhibition of HH/GLI signaling in melanoma cells not only reduced IDO1 expression but also interfered with the repression of T cell activation by attenuating IDO1/kynurenine-mediated immunosuppression. These data identify the immunosuppressive IDO1-kynurenine pathway as a novel pro-tumorigenic effector of oncogenic HH-IL6 and GLI-STAT cooperation. Our data suggest simultaneous pharmacological targeting of the HH/GLI, JAK/STAT and IDO1- kynurenine axis as rational combination therapy in skin cancers.

Background Over 100 million people worldwide suffer from birch pollen allergy. However, identification of molecular determinants driving Th2-biased allergic sensitization to Bet v 1, the major birch pollen allergen, remains elusive. Objective Here, we examined whether Bet v 1 or the pollen matrix is responsible for activation of antigen-presenting cells and the subsequent Th2 polarization, relevant in the process of allergic sensitization. Methods The allergenicity of Bet v 1 and of birch pollen extract (BPE) was addressed by stimulation of murine and human dendritic cells and by in vivo monitoring of Th2 polarization. Further, Bet v 1 was depleted from BPE by immunoprecipitation in order to analyze its involvement in the occurrence of a Th2 response. Results The allergen alone did neither stimulate dendritic cells in vitro nor induced Th2 polarization in vivo, even in the presence of the natural LPS concentration determined in the BPE. In contrast, BPE was shown to activate dendritic cells and strongly promoted a Th2 polarization. Even upon immunization with Bet v 1-depleted BPE the amount of induced Th2 cells remained unaltered. Conclusion This finding indicates that the Th2-polarizing potential of BPE is Bet v 1 independent; therefore, sensitization to Bet v 1 is induced by an as-yet-undetermined pollen compound or mechanism in the pollen environment. These data suggest that sensitization is not exclusively linked to the intrinsic properties of individual proteins. These findings are relevant in understanding allergic sensitization towards pollen allergens and might pave the way for future prophylactic approaches.