Cervical carcinogenesis is a multistep process which starts with an acquisition of high-risk HPV infection. Multiple biological and behavioural risk factors affect the progression towards severe lesions. The most pronounced risk factors include viral factors, immunosuppression, co-occurrence of other sexually transmitted infections (STI), genetic polymorphism of tumour suppressor genes (TSG), and smoking. Risk factors contribute to the transition from incident to permanent HPV infection and from persistent infection to high-grade lesion.
HPV-induced methylation silencing of TSGs is believed to be a sign of high-grade lesions carrying higher risk of short-term progression into invasive stadium. While almost all cases of invasive carcinomas have methylated promotors of specific TSGs, less advanced severe cervical lesions (HSIL) are methylated only in 60-90 % cases. Morphology or biomarkers reflecting differences between methylated and unmethylated HSIL lesions are scarcely described in the literature.
In our study, we focused on exploring biological risk factors in methylated and unmethylated HSIL lesions, namely co-occurrence of other STIs and presence of certain HR-HPV genotypes.
108 residual samples of liquid-based cytology of Czech women with histologically confirmed high-grade cervical lesion were analysed with
1) Precursor M kit (Self-screen) to assess methylation status of tumour-suppressor genes CADM1, MAL, and has-miR-124, related to cervical carcinogenesis
2) LINEAR ARRAY HPV Genotyping Test (Roche) and type-specific PCR targeting E6 and E7 viral oncogenes to reveal specific HR-HPV genotypes
3) Allplex STI Essential Assay (SeeGene) to discover possible co-occurrence of 7 most common microbial pathogens responsible for cervicitis
Methylated and unmethylated HSILs were evaluated in two categories, first presence of HPV genotypes 16,18 and 45, and second co-occurrence of any microbial pathogen.
36 % of HSIL lesions in our study had negative methylation status. At least one microbial pathogen was detected in 50 % of HSIL lesions but there was no significant difference between methylated and unmethylated groups. HPV types 16,18, and 45 were detected more often among methylation positive samples but this finding was not statistically significant.
There is no difference in STIs co-occurrence between methylation negative and positive HSILs. HPV types 16,18, and 45 occur more often in methylation positive HSILs but also infection of other HR-HPV types might result in methylation of TSG´s promoters. Further studies are needed to confirm that the methylation status differentiates biological early lesions from advanced HSILs.
1) CADM1, MAL and miR124-2 methylation analysis in cervical scrapes to detect cervical and endometrial cancer. Journal of Clinical Pathology
2) Infection and cervical neoplasia: facts and fiction. Int J Clin Exp Pathol5. Infection and cervical neoplasia: facts and fiction. International journal of clinical and experimental pathology