Inflammasome and cancer

Summary

Since its creation in 2012 within the Atip-Avenir program, V Petrilli’s team studies the multi-faceted roles of NLRP3, a pattern recognition receptor (PRR). The NLRP3 protein is well-known for its function in the promotion of the inflammasome assembly upon danger or pathogen sensing in myeloid cells. Inflammasomes are caspase-1 activating platforms. They consist in a PRR such as NLRP3, the adaptor ASC which allows the dimerization and activation of caspase-1. Active caspase-1 then cleaves its substrates, the pro-IL-1beta, the proIL-18 and gasdermin-D (GSDMD) to promote the secretion of the inflammatory IL-1beta and IL-18 cytokines and pyroptosis, a lytic cell death triggered by GSDMD pores. This pathway plays major roles in innate immunity and its dysregulation results in inflammatory conditions including Alzheimer, gout diseases and also cancer, and autosomal dominant mutations cause cryopyrin (NLRP3) associated periodic syndromes (CAPS or  NLRP3-AIDs).

Studying the sole inflammasome activation outputs is challenging because its activation relies on the usage of danger or pathogen signals which induce multiple signaling pathways beyond the inflammasome. To bypass these signals, our lab has developed a light activable inflammasome using optogenetic approaches. The photosensitive domain of Cryptochrome 2 (Cry2, referred to as opto) from Arabidopsis thaliana was fused to the ASC protein, the adapter of the inflammasome, along with mRFP to visualize the protein in cells (construct called opto-ASC). Upon light activation, opto-ASC oligomerized, as if ASC was engaged by a PRR resulting in caspase-1 activation, and ultimately cytokine cleavage and pyroptosis (Nadjar, Monnier et al. Science Signaling 2024). Using opto-ASC, we were able to measure precisely cell swelling during pyroptosis and demonstrated with unprecedent precision that it occurs in two-steps and that plasma membrane rupture is an active and not a passive process as previously thought (collaborations with O Destaing Institute for advanced Biosciences and S Monnier Institute Lumière Matière). This tool will allow a better understanding of the molecular events leading to cell swelling and plasma membrane rupture events nducing inflammation.

Interestingly, new inflammasome independent functions have emerged for NLRP3, and our lab identified that in response to DNA double strand breaks (DSB), NLRP3 forms a complex with ATM, the apical kinase of the DNA damage response (DDR) in epithelial cells, to support ATM activation. Absence of NLRP3 led to decrease ATM activity and substrate phosphorylation. The lower ATM activation in the absence of NLRP3 confers resistance of lung epithelial cells to chemotherapy treatment due to impaired p53 activation. Our lab also showed that NLRP3 expression is frequently downregulated in Non-Small Cell Lung cancer and Breast Cancers (BC) and during cell transformation (Weinberg’s model of in vitro malignant transformation) (Bodnar-Wachtel*, Huber* et al.,Life Science Alliance 2023), akin to DDR actors.

We also discovered that NLRP3 is an actor of the DSB repair pathway. NLRP3 binding to REV7, a subunit of the shieldin complex, prevents REV7 binding to DSB and therefore promotes repair through homologous recombinaison (Burlet et al. Nucleic Acid Research 2025). This function is also independent of the inflammasome and of NLRP3’s role on ATM pathway. As a consequence, NLRP3 deficient cells are sensitive to PARP inhibitors, offering promising therapeutical perspectives for cancer treatment.
Whether NLRP3 binding to REV7 affects other REV7 functions in genome stability is currently under investigation.

In addition, a hot question for the lab is to understand how NLRP3 cytosolic versus nuclear functions are regulated.

Current projects

• Aim 1- Study the novel function of NLRP3 in DNA damage response and genome stability. (V Petrilli, AL Huber)
• Aim 2- Regulation of the NLRP3 functions by the circadian clock. (AL Huber, V Petrilli)
• Aim 3- Study the inflammasome functions in the anti-tumoral immunity. (V Petrilli)