Role of NLRs in Melanoma

Background and Innovation: Inflammation is one of the hallmarks of cancer, whose dysregulation is associated with unfavorable clinical prognosis in cancer patients. We have reported the activation of the “inflammasome,” a multi-protein complex responsible for caspase-1 activation and subsequent IL-1β secretion, as a mechanism of tumor progression, drug resistance, and immune suppression in human melanoma. The pro-tumorigenic role of inflammasomes has also been reported in other cancers. However, few studies have investigated the molecular mechanisms of inflammasome activation in cancer cells. Using The Cancer Genome Atlas (TCGA) data, we found that the inflammasome sensor NLRPs are highly mutated in melanoma, with 65.5% of melanoma (284 of 440 tumors) harboring somatic missense mutations. In contrast, mutation rates are low in other inflammasome genes, such as PYCARD (ASC gene), CASP1, or CASP5. Although the consequences of NLRP mutations in tumor cells are unknown, melanoma mutations in NLRP3 overlap with gain-of-function mutations in cryopyrin-associated periodic syndromes (CAPS), and preliminary data support our hypothesis that the somatic missense mutations in NLRP3 alter the structure of NLRP3 and activate NLRP3 inflammasome, leading to tumor progression in human melanoma. This is the first report of molecular mechanisms connecting somatic missense mutations in NLRP3 to inflammasome activation and tumor promotion. In addition to the conceptual innovation, our proposal uses a novel assay to model cancer-related somatic missense mutations in NLRP3 in silico and assess the effects of NLRP3 inhibitors on ATP binding affinity in the presence of mutations. Significance and Impact to Veterans Healthcare: Melanoma represents 4% of skin cancers but is responsible for 64% of skin cancer-related deaths. Sun exposure is part of daily life for US troops, especially during summer, and is linked to a higher incidence of melanoma. The risk of developing melanoma is increased in individuals who experience sunburn at an early age, including young women who play an increasingly important role in the VA population. Additionally, skin conditions such as skin cancers are a significant reason for the medical evacuation of soldiers during US military service. As a result, the economic burden of this malignancy is substantial, driven by both the rising direct costs of melanoma treatment and the indirect costs associated with productivity losses. We will investigate the molecular mechanisms of inflammasome activation and tumor progression by studying somatic missense mutations in NLRP3 in human melanoma cells and treating these cells using various inflammasome inhibitors. Path to translation/implementation: In this proposal, we will define the structural changes (Aim 1), biochemical and biological effects of somatic NLRP3 mutations (Aim 2), and their impacts on the therapeutic effects of inflammasome inhibitors in melanoma (Aim 3). Recent reports of the inflammasome structure and inhibitor binding of NLRP3 provided new insights into its mode of action and inhibitor-NLRP3 interaction at molecular levels, creating a framework for developing more effective and specific NLRP3 inhibitors against chronic diseases with major health concerns. Since inflammasome mutations can change their protein structures and compromise the interactions with their protein partners or inhibitors, elucidating the structure and its binding with protein partners and inhibitors at molecular levels in tumor cells is critical for clinical success in melanoma and potentially other cancers that carry mutations in NLRPs. Given the safety profile and clinical availability of many inflammasome inhibitors, promising findings in the current proposal could be easily translated into patient care. Furthermore, our study will allow us to modify the existing inhibitors using the structure-based drug design to develop novel inflammasome inhibitors with improved efficacy and specificity aga Project Number: 1I01BX006598-01A1 | Fiscal Year: 2025 | NIH Institute/Center: Veterans Affairs (VA) | Principal Investigator: Mayumi Fujita | Institution: VA EASTERN COLORADO HEALTH CARE SYSTEM, Aurora, CO | Activity Code: I01 | Study Section: Special Emphasis Panel[ZRD1 ONCE-A (01)] View on NIH RePORTER: https://reporter.nih.gov/project-details/11047189