The role of the NLRP1 receptor in the immune response and progression of melanoma: an in vivo and in silico approach

Author(s)

Vitor Pedro Targhetta

• Document type: Master's Dissertation
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Instituto de Ciências Biomédicas (ICB/SDI)
• Defense date: 2022-09-19

Examining board members

Niels Olsen Saraiva Câmara; Luciana Rodrigues Carvalho Barros; Alessandra Pontillo; Elaine Guadelupe Rodrigues

• Advisor: Niels Olsen Saraiva Câmara; Cristiane Naffah de Souza Breda

Abstract

Inflammasomes are protein complexes that lead to the activation of pro-caspase-1 and the consequent generation of the active forms of the cytokines IL-1&#946 and IL-18. NLRP1 was the first receptor discovered with inflammasome-forming capability and is robustly expressed in skin and immune cells. Even though it has a direct relationship with the skin and the immune system, the relationship of NLRP1 with melanomas is still not fully understood. This project aimed to verify the importance of the NLRP1 inflammasome in CD4&#43 T lymphocytes differentiation and to relate this possible interaction with an immune response against melanoma in mouse models. Comparative immunophenotyping showed that both C57BL/6 and NLRP1 KO mice are similar in their major immune cell populations, except for a decrease in splenic Treg lymphocytes. The literature has shown that the NLRP1 activator Valboro-Pro (VbP) has interesting immuno-dependent antitumor effects. Interestingly, treatment with VbP on CD4&#43 T lymphocytes in vitro did not interfere with cell viability and was shown to be able to robustly reduce the amounts of CD4&#43 Foxp3&#43 cells. Both tumor models from the murine melanoma lineage B16-F10 in NLRP1 KO and C57Bl/6 mice, as well as mice treated or not with VbP, did not show relevant statistical differences in tumor progression. In parallel, computational biology analyzes were performed trying to understand the role of NLRP1 in melanoma and immunotherapy resistance in humans. In the approaches proposed here, we observed, from the TCGA-SKCM cohort, that NLRP1 correlates with a greater inflammatory infiltrate and its co-expressed genes are primarily related to the activation of T lymphocytes. In addition, we constructed a risk score to predict survival of melanoma patients, using genes related to the inflammasome and pyroptosis pathways. Finally, we showed that NLRP1 was not able to predict the response to anti-PD-1 treatment in human melanomas. In this sense, we identified genes and isoforms differentially expressed between responsive and non-responsive patients and related them to a global cellular context, analyzing their transcriptional profiles, ontology pathways, splicing modes and possible effects on the resulting proteins. We found that a positive response to treatment is strongly marked by the presence of events related to B lymphocytes and humoral immunity, not necessarily being reflected in a group of differentially expressed genes. Although a humoral response was predictive for immunotherapy-responsive patients, the presence of B lymphocytes determined from algorithms of deconvolution of gene expression data was not shown to be predictive. Finally, splicing profiles and protein consequences were also not predictive to discriminate between responders and non-responders. As main conclusions we have that our results point to a possible new mechanism of delimitation of the differentiation of Treg cells associated with VbP and that NLRP1 does not directly interfere in lymphocyte differentiation or melanoma growth in murine models, as well as does not influence the response to immunotherapy in humans. (AU)

• FAPESP's process: 20/04408-8 - The role of NLRP1 inflamassome in the antitumor response of Th17 limphocytes
• Grantee: Vitor Pedro Targhetta
• Support Opportunities: Scholarships in Brazil - Master