| Background:Cervical cancer is one of the most common cancers among women worldwide. Nearly all of the cervical cancers are associated with human papillomavirus (HPV) infections. HPV16is the predominant type among the high risk types. The high risk human papillomavirus (HR-HPV) infect the basal epithelial cells. In low and high grade squamous intraepithelial lesions (LISL, HSIL), HR-HPV present as episomal form while as integrated form in cervical cancer. The differences of integration frequencies in different cervical lesions imply that HPV genome integration may play an important role in cervical carcinogenesis and may induce chromosomal instability. HPV integration frequently disrupts the E2open reading frame and remodel of the E6E7promoter which would result in the continuous expression of the E6and E7oncoproteins. The up-regulation of E6and E7deregulate the tumor suppressor genes P53and retinoblastoma proteins. The interferences between them disturb the regulation of the mitotic spindle apparatus and lead to the alteration of chromosomal structure and functions. All these factors may contribute the progression of cervical lesions.Previous studies report that HPV integration is random in almost all chromosomes. However, recent studies show that the integration presents an inclination for hot spots. The fragile site is one of them. The fragile sites play an important role in the deletion, translocation, gene amplification and integration of foreign DNA, tumor-associated viruses. They are highly unstable and recombinogenic regions of the genome. The fragile sites are the common preferential sites for HPV integration. To get a better understanding of the underlying mechanisms of HPV integration in cervical carcinogenesis, we performed an analysis of distribution of HPV16into human genome and disrupted sites in the viral genome. In addition, we carried out an analysis of their association with clinicopathological factors.Methods:A total of61cervical cancer samples were collected in the department of Obstetrics and Gynecology in our hospital between November2011and September2012. The total genomic DNA was extracted and HPV genotyping was performed. Samples solely infected with HPV16were subjected to the integration analysis by DIPS-PCR.Results:1. A total of42viral-cellular junctions were identified in26of47samples. The integrations distributed in most of the human chromosomes. Chromosome3and20presented with the most integration sites.66.7%(28/42) of HPV integrations were in the region of different genes in human genome and4of them were with more than once integration.2. Of the42integrations identified,31(73.8%) occurred near the fragile sites. Of the43miRNAs identified near the integration sites,31(72.1%) occurred near the fragile sites.3. The frequencies of HPV integration was not significantly associated with age, FIGO stage, histology, tumor grade, cervical stromal invasion, lymph node status. Multiple integration tended to be in cancer samples with lymph vascular space involvement.4. Of the26samples with HPV integration,12cases were identified with multiple integration events.25(59.5%) of the sites of viral gene disruption were at the E1,E2genes.25(59.5%) of the integration sites located in the repetitive region of the host genome.23(82.1%) of the integration sites located in the intron of the genes.5. The regions6q23.3,20p12.1were affected twice. By compiling the data of this study and published articles, a total of12genes and4predicted genes were affected at least twice in independently cervical samples. Most of them located in the regions of5hot spots:2q22.1,3q28,8q24,13q22.1and17q23.1.Conclusions:1. The HPV integration and miRNAs are frequently located near the fragile sites.2. There are no significantly associations between frequency of HPV16integration and clinicopathological factors.3. Multiple integrations of HPV16into host genome are common in cervical cancer.4. The HPV16genome is more likely to be disrupted in the E1, E2genes. Most of the integration sites locate in the repetitive region of the host genome. |
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