Objectives: Infection with high-risk human papillomavirus (HPV) is a critical factor associated with carcinogenesis of the uterine cervix. HPV-16 is most frequently found, and is further subclassified into intratypic variants based on the nucleotide sequences of the viral genes. Although certain HPV-16 variants are reported to be associated with the progression of cervical lesions, these relationships remain controversial with different results for different populations. To provide data for another population, we investigated the prevalence of HPV-16 and distributions of its intratypic variants among Mongolian women with cervical intraepithelial neoplasia (CIN) and invasive cervical cancer.
Materials and methods: We analyzed samples from 374 randomly selected women who attended the National Cancer Center of Mongolia between January 2002 and July 2007, including 147 invasive cervical cancer patients, 127 CIN patients and 100 age-matched controls who were cytologically normal. HPV genotyping was initially conducted, followed by variant analysis for HPV-16-positive samples by nucleotide sequencing of the E6 gene. The HPV data were evaluated statistically for correlations with the patients' clinical data.
Results: HPV genotyping detected 101 HPV-16-positive samples. Among these samples, 92 were available for subsequent variant analysis, including 66 invasive cervical cancer samples, 25 CIN samples and 1 cytologically normal sample. A total of 14 different variants were identified. All 14 variants belonged to the European lineage, and the European prototype was detected in 66% (61/92) of the samples. Among the remaining 31 variants, variants with the T350G nucleotide change were predominant (13/31, 42%), followed by variants containing G94A (11/31, 35%), G176A (4/31, 13%) and G274T (2/31, 7%). There were no significant differences among all the variants regarding their distributions in CIN and invasive cervical cancers.
Conclusions: HPV-16 variants of the European lineage were exclusively distributed among the Mongolian women examined, and the European prototype was overwhelmingly predominant. Since no significant differences were found between the types of variants and severities of the cervical lesions, it is possible that racial or geographic factors may have some influences on these relationships.