Genotyping and differential expression analysis of inflammasome genes in sporadic malignant melanoma reveal novel contribution of CARD8, IL1B and IL18 in melanoma susceptibility and progression

Abstract

Sporadic melanoma malignancy is correlated with constitutive secretion of IL-1 beta in transformed melanocytes suggesting the involvement of inflammasome in melanoma. Common variants in inflammasome genes are known to affect IL-1 beta expression. To investigate the contribution of inflammasome genetics in melanoma development and progression and to identify a potential prognostic marker, the distribution of selected inflammasome SNPs was analysed in a Brazilian case/control cohort of sporadic malignant melanoma (SMM) and then the expression of inflammasome components was evaluated in melanoma biopsies. Allele and gene-specific Taqman assays were implied for genotyping of case/control DNA samples and for relative expression analysis in skin biopsies respectively. CARD8 rs6509365 was found to be significantly more common in healthy volunteers than in SMM patients suggesting a protection effect of this variant towards melanoma development. Accordingly, CARD8 expression was found to be reduced in nevus compared to melanoma biopsies. Upon stratification, NLRP1 rs11651270 and CARD8 rs2043211 were found associated with nodular melanoma; IL1B rs1143643 to a lower value of Breslow index; IL18 rs5744256 to melanoma development in sun sensitive individuals. As expected, IL1B expression was up-regulated in tumour biopsies especially in metastatic samples, whereas IL18 was down-regulated compared to nevus. Our results demonstrated for the first time the contribution of inflammasome genes CARD8, IL1B and IL18 in SMM.