Differential hypermethylation of genes in vulvar cancer and lichen sclerosus coexisting or not with vulvar cancer

Abstract

Squamous cell carcinoma (SCC) of the vulva is a heterogeneous disease, associated or not with vulvar lichen sclerosus (LS). The precursor role of LS in vulvar cancer is unclear. We studied the epigenetic alterations of RASSF1A, RASSF2A, p16, TSP-1 and MGMT genes in vulvar SCCs, LS associated with SCC, isolated LS and normal vulvar skin. Gene hypermethylation and human papillomavirus presence were evaluated by methylation-specific PCR and PCR/reverse line blot, respectively. High-risk human papillomavirus types were present in 16.7% of the patients with vulvar SCC. There were increasing percentages of hypermethylation of genes from isolated LS to LS associated with vulvar SCC and vulvar SCC. The genes were hypermethylated more frequently in vulvar SCC associated with LS than in those not associated with LS, MGMT and RASSF2A being unmethylated in LS not associated with vulvar SCC. TSP-1 hypermethylation was related to recurrence in patients with vulvar cancer. Conclusions are as follows: (i) the epigenetic inactivation of genes is a common event in vulvar SCC and is also present in adjacent lesions, implying a possible precursor role for these alterations; (ii) MGMT and RASSF2A hypermethylation are present exclusively in vulvar SCC and LS associated with SCC, and absent from isolated LS; and (iii) TSP-1 hypermethylation is a bad prognosis factor in vulvar SCC.Vulvar cancer (VC) accounts for 3-5% of all female genital cancers and is more frequent in women older than 75 years. Squamous cell carcinoma (SCC) is the most common type of VC and has been divided into two groups on the basis of the presence or absence of the human papillomavirus (HPV), which leads to different models of progression.2 It is well known that there are, on one hand, HPV-associated VCs of the warty or basaloid type and, on the other, keratinizing SCC, most of which are not HPV related. First, SCC associated with HPV, mostly HPV16, is the least frequent, accounting for one third of vulvar SCC. It is diagnosed at young ages and is associated with other types of cancer, such as vaginal and anal carcinoma. It shares risk factors with cervical cancer (multiple sexual partners, previous history of smoking and HPV presence and typical pathological features with warty or basaloid subtypes). The precursor lesion is of the classic vulvar intraepithelial neoplasia (VIN) type, and 4% of VIN have a risk of malignancy and frequently relapse spontaneously. 4 On the other hand, SCC that is not associated with HPV is more frequent (66% of cases), typical of older ages and more frequently associated with lichen sclerosus (LS) or squamous cell hyperplasia. 4,5 The exact role of LS in pathogenesis of VC is not yet known, but the risk of developing vulvar SCC approaches 5% in women with these lesions.5 SCC is of the keratinizing type and is preceded by differentiated VIN, which is characterized by atypical basal keratinocytes with normal maturation. These precursor lesions are rarely diagnosed, their grade of malignancy is high and they exhibit immunohistochemical ...

Vulvar intraepithelial neoplasia

“…p53 and phosphatase and tensin homolog (PTEN) mutations and microsatellite instability have been demonstrated in early-stage HPV-independent vulvar carcinogenesis [16,23,24,25,26]. In addition, the possible role of Ras-association domain family 2A (RASSF2A), O-6-methylguanine-DNA methyltransferase (MGMT), and thrombospondin-1 (TSP-1) genes in transcriptional silence caused by methylation has been reported [27,28].…”

Overexpression of Cancer-Associated Genes via Epigenetic Derepression Mechanisms in Gynecologic Cancer

“…Many TSGs in vulvar cancer, including tumor protein p73 ( TP73 ), immunoglobulin superfamily member 4 ( IGSf4 ), DAPK1, RASSF1A, RASSF2A, CDKN2A , thrombospondin 1 ( TSP-1 ), MGMT , and others, are inactivated through promoter region DNA hypermethylation. Among these genes, TSP-1 shows a potential prognostic role in VSCC recurrence (137), and TP73 displays features that may serve as therapeutic biomarkers in vulvar cancer (138). DNA hypomethylation patterns may also be used as potential prognostic markers in several cancers.…”

Altered global methylation and hydroxymethylation status in vulvar lichen sclerosus: further support for epigenetic mechanisms

“…However, chronic broadband UVA irradiation of human keratinocytes can induce alterations in histone modification and sever promoter hypermethylation of p16 INK4a , leading to substantial impairment of p16 INK4a transcription. 10 Guerrero et al 8 demonstrated that there was increasing hypermethylation of genes from isolated VLS associated with vulvar SCC. The genes were hypermethylated more frequently in vulvar SCCs associated with LS than in those not associated with LS.…”

“…6 Hypermethylation of genes such as TP53, KRAS, CDKN2A (p16) and DAPK1 has been reported in both genital LS and LS-associated SCCs. [7][8][9][10][11][12][13] DNA methylation at the 5-position of cytosine is well recognized as an important epigenetic modification in human health and disease. 10 Recent evidence has demonstrated that 5-methylcytosine (5mC) can be converted by teneleven translocation (TET) enzymes in association with isocitrate dehydrogenases (IDHs) to 5-hydroxymethylcytosine (5hmC).…”