Hypermethylation-induced inactivation of IRF6 and RARΒ genes as potential prognostic biomarker in vulvar squamous cell carcinoma

Objectives: Vulvar squamous cell carcinoma (VSCC) represents 5% of gynecological malignancies. About 80% of VSCCs arises from inflammatory diseases, such as lichen sclerosus (LS). The molecular alterations involved in onset/progression of LS-associated VSCC are unknown. Interferon regulatory factor 6 (IRF6) and retinoic acid receptor β (RARβ) tumor-suppressor genes have been found downregulated by promoter methylation in different cancers.1,2 We aimed to evaluate the possible involvement of the IRF6 and RARβ in the development of VSCC from LS. Methods: IRF6 and RARβ mRNA expressions and promoter methylations were investigated by quantitative PCR (qPCR) and bisulphite-sequencing, respectively, in VSCC (n=20) and the adjacent LS (n=20), vulvar intraepithelial neoplasia (VIN; n=5, only for IRF6), cancer-free LS (cfLS, n=20) and normal skin (NS, n=20). IRF6 and RARβ pathway-related genes p63 and c-Jun mRNAs were also investigated.3,4 Results: IRF6 resulted downregulated in LS, VIN, VSCC and cfLS specimens, compared to NS, whereas p63 was overexpressed. IRF6 promoter was hypermethylated in 9/20 (45%) LS, 1/5 (20%) VIN, 16/20 (80%) VSCC, 2/20 (10%) cfLS, and 0 NS.3 RARβ was downregulated in VSCC compared to LS, cfLS and NS, whereas c-jun resulted overexpressed in VSCC compared to LS, cfLS and NS. RARβ promoter was hypermethylated in 18/20 (90%) VSCC, 11/20 (55%) cfLS, 10/20 (50%) LS and 5/20 (25%) NS. Interestingly, 2/18 (11.1%) VSCC showed full methylation of RARβ promoter were from women with tumor recurrence.4 Conclusions: IRF6 and RARβ are down expressed by promoter methylation in LS-associated VSCC and may be involved in the development/progression of VSCC from LS. IRF6 and RARβ promoter hypermethylation may be a biomarker of cancer-risk in LS patients, and a prognostic biomarker of cancer progression in LS-associated-VSCC patients.3,4 References: 1.Ivanova T et al. BMC Cancer.2:4,2002. 2.Botti E et al. PNAS.108:13710-15,2011. 3.Rotondo JC et al. JAMA Dermatol.152:928-33,2016. 4.Rotondo JC et al. JAMA Dermatol.154:1-5,2018.