Many human papillomavirus (HPV)-positive high-grade lesions and cancers of the uterine cervix harbor integrated HPV genomes expressing the E6 and E7 oncogenes from chimeric virus-cell mRNAs, but less is known about HPV integration in head and neck cancer (HNC).Mucosal high-risk (HR) human papillomavirus (HPV) types are found in nearly 100% of carcinomas of the uterine cervix, many anogenital cancers, and ϳ25% of head and neck cancers (HNC) (9, 13, 42). The most common HR HPV is type 16, found in over 50% of cervical cancers and 90 to 95% of HPVpositive HNCs. In persistent infection, HPV genomes are maintained as circular, unintegrated plasmids that persist in the nuclei of infected cells (see Fig. 1A). In contrast, HR HPV DNA found in cervical cancer specimens is frequently disrupted and integrated in the cellular genome in a way that potentially alters the expression program of the viral early gene region and/or the host genome (2,5,8,21,23,24,31,43). The integrated HR HPV fragments in high-grade precancerous cervical lesions, cervical carcinomas, and derived cell lines express the viral transforming genes E6 and E7 from chimeric virus-cell mRNAs, while the downstream early genes that are required for viral replication and regulated viral gene expression are disrupted or silenced (33,37,47,55). Further, chimeric virus-cell mRNAs may be more stable than the viral early mRNAs, which harbor a 3Ј destabilization motif (20,53). In addition, some integration sites in cervical cancer and precursor lesions have been found near potential growth control genes (11,40,55).Advances in keratinocyte culture techniques have permitted the study of the life cycle of HR HPV types that replicate efficiently and persist in primary human keratinocytes, such as 34,35), and to a more limited extent 36). However, relatively little is known about the progression of the infected cell toward a malignant phenotype in vivo or in culture. While some cervical cancers have been shown to harbor extrachromosomal HPV DNA, it is apparent that integration of viral DNA accompanied by disruption of the integrity of the HR HPV genomes represents a common, albeit not absolutely obligatory, step associated with carcinogenic progression associated with the genital tract (42, 57). The majority of cervical carcinomas caused by the two most common HR HPV types, HPV-16 and -18, contain integrated viral sequences (52) that express E6-E7 from chimeric, spliced virus-cell transcripts. However, the genetic structure and expres-