Viral integration plays an important role in the development of malignant diseases. Viruses differ in preferred integration site and flanking sequence. Viral integration sites VIS have been found next to oncogenes and common fragile sites.
Understanding the typical DNA features near VIS is useful for the identification of potential oncogenes, prediction of malignant disease development and assessing the probability of malignant transformation in gene therapy. Therefore, we have built a database of human disease-related VIS Dr. The current build of Dr. Among them, about VIS have viralβhost junction sequence. The contribution of infectious agents to the development of serious human diseases, especially tumors, is increasingly understood 1.
Research has revealed that integration of viral genomes into human chromosomes is necessary for most viral induction of tumor development, which can activate or inactivate host genes by means of provirus insertion 2 , 3. This holds not only for retroviruses such as human T-cell leukemia virus 4 , but also for a number of non-retroviruses such as human papillomavirus 5 and hepatitis B virus 2 , 6. Finally, integration events can cause rearrangements of viral and host sequences 7 , expression of fused transcripts, deletions of chromosomal sequences and transpositions of viral sequences from one chromosome to another 8β Viral integration is site-specific in many cases Moreover, viruses differ in their preferred insertion site Viral integration sites VIS have become a key to associating viral infection and human malignant disease.
Up to date, at least seven viruses have been compellingly associated with human malignant diseases, including:. HTLV-1 adult T-cell leukemia and tropical spastic paraparesis 13 ;. HPV cervical cancer, head and neck cancer and anogenital cancer 14 , 15 ;.
HHV-8 Kaposi's sarcoma 16 ;. EBV Burkitt's lymphoma 17 ;. HBV hepatocellular carcinoma 18 ;. MCV, Merkel cell polyomavirus Merkel cell carcinoma 19 ; and. There are many viruses that are potentially associated with human malignant diseases such as Simian virus 40 brain cancer, bone cancer and mesothelioma , BK virus prostate cancer and so on 1β3. Some are still under study, such as xenotropic murine leukemia virus-related virus whose relationship with prostate cancer is still controversial 20β Most of those viruses have a significant integration step in viral infection and disease development.
