Neureiter, D. | Search bioRxiv

bioRxiv2021

The NLRP3/eIF2 axis drives cell cycle progression in acute myeloid leukemia

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-1{beta} 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 eIF2 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 eIF2 phosphorylation as negative cell cycle regulator. Taken together, we show that inhibition of the NLRP3 inflammasome reduces AML cell proliferation by promoting eIF2 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.

immunology↗

bioRxiv2019

Epidermal activation of Hedgehog signaling establishes an immunosuppressive microenvironment in basal cell carcinoma by modulating skin immunity

Genetic activation of Hedgehog (HH)/GLI signaling causes basal cell carcinoma (BCC), a very frequent non-melanoma skin cancer. Small molecule targeting of the essential HH effector Smoothened (SMO) proved an efficient medical therapy of BCC, although lack of durable responses and frequent development of drug resistance pose major challenges to anti-HH treatments. In light of the recent breakthroughs in cancer immunotherapy, we analyzed in detail the possible immunosuppressive mechanisms in HH/GLI-induced BCC. Using a genetic mouse model of BCC, we identified profound differences in the infiltration of BCC lesions with cells of the adaptive and innate immune system. Epidermal activation of HH/GLI led to an accumulation of immunosuppressive regulatory T cells, and to an increased expression of immune checkpoint molecules including PD-1/PD-L1. Anti-PD1 monotherapy, however, did not reduce tumor growth, presumably due to the lack of immunogenic mutations in common BCC mouse models, as shown by whole-exome sequencing. BCC lesions also displayed a marked infiltration with neutrophils, the depletion of which unexpectedly promoted BCC growth. The results provide a comprehensive survey of the immune status of murine BCC and provide a basis for the design of efficacious rational combination treatments. This study also underlines the need for predictive immunogenic mouse models of BCC to evaluate in vivo the efficacy of immunotherapeutic strategies.

cancer biology↗