Tomas Kahn

APM‐1 , a novel human gene, identified by aberrant co‐transcription with papillomavirus oncogenes in a cervical carcinoma cell line, encodes a BTB/POZ‐zinc finger protein with growth inhibitory activity

Integration of human papillomavirus (HPV) DNA into the host cell genome is an important step in cervical carcinogenesis. In tumour cells with integrated HPV DNA, transcription of viral oncogenes E6 and E7 continues into the flanking cellular sequences thereby producing viral–cellular fusion transcripts. Analysis of cellular sequences flanking the integrated HPV68 DNA in the cervical carcinoma cell line ME180 revealed homozygosity of the mutant allele in ME180 cells. We speculated that this could indicate the existence of a cellular tumour suppressor gene in the integration region. We report here the identification of a novel human gene, named APM‐1, which is co‐transcribed with the HPV68 E6 and E7 genes and is present in the 3′‐cellular part of the ME180 viral–cellular fusion transcripts. The APM‐1 gene encodes a protein with a BTB/POZ domain and four zinc fingers, and is located at chromosome 18q21. APM‐1 transcripts are detected in normal cervical keratinocytes, but not in the majority of cervical carcinoma cell lines analysed. The APM‐1 gene caused a reduction of clonal cell growth in vitro of HeLa and CaSki tumour cells. These characteristics make APM‐1, the first novel human gene identified in a HPV integration region, a likely candidate for the postulated tumour suppressor gene.

Prevalence of human papillomavirus in cervical cancer: A multicenter study in China

A large‐scale epidemiologic survey on the prevalence of different types of human papillomavirus (HPV) in cervical cancer in China is indicated because of the implications for the development of diagnostic probes and vaccines against cervical cancer. A total of 809 cervical cancer specimens were collected from 5 regions in China including Shanghai, Guangzhou, Sichuan, Beijing and Hong Kong. HPV DNA was detected in 83.7% of the specimens. HPV‐16 was present in 79.6%, HPV‐18 in 7.5%, HPV‐52 in 2.6% and HPV‐58 in 3.8% of all HPV‐positive specimens. The prevalences of HPV‐16 and HPV‐18 in Hong Kong were 61.7 and 14.8%, respectively, representing a lower HPV‐16 and a higher HPV‐18 proportion compared with the other regions. HPV‐16 remained the most common HPV infection in both squamous cell carcinoma (SCC) and adenocarcinoma (AC). The proportion of HPV‐18 infection was significantly higher in AC than in SCC.

Human papillomaviruses in lymph node neck metastases of head and neck cancers.

Conclusion The results of this study corroborate earlier findings that human papillomavirus (HPV)16 is the most prevalent type of HPV in squamous cell carcinomas of the head and neck (SCCHNs) and reinforce a possible influence of HPV on SCCHN progression by showing that the majority of HPV-positive patients harbor HPV16 (or HPV33) both in their primary tumors and in lymph node neck metastases (LNNMs). Objective HPVs are causally associated with carcinomas of the uterine cervix and have also been linked to a subset of SCCHNs. In order to further investigate the predicted causative role of HPV in SCCHNs, we analyzed pairs of primary tumors and LNNMs or LNNMs alone for the presence of HPV DNA using polymerase chain reaction (PCR). Material and methods DNA was extracted from fresh frozen tissue samples of primary tumors and the corresponding LNNMs of 18 patients and from LNNMs alone in 17 patients. For the detection and typing of HPV, PCR was performed using both type-specific and consensus primer pairs, followed by Southern hybridization and, in selected cases, sequencing of the PCR products. Results Of the 35 patients investigated, 22 (63%) were found to have HPV DNA in their tumors: HPV16 DNA in 21 cases and HPV33 in 1. The highest HPV prevalence was detected in tumors of Waldeyers tonsillar ring (8/9 patients; 89%). Of the 18 patients in whom primary tumors and LNNMs were analyzed, 7 (39%) were HPV-positive in both samples (HPV16, n=6; HPV33, n=1), in 3 (17%) the primary tumors were HPV-negative and the LNNMs HPV16-positive and in 1 (5.5%) the primary tumor contained HPV16 and the LNNM was negative. Interestingly, of the 7 patients in whom LNNMs had been detected only several months after diagnosis and treatment of the primary tumors, only 1 showed infection with HPV (HPV33).

PROMOTER ACTIVITY OF SEQUENCES LOCATED UPSTREAM OF THE HUMAN PAPILLOMAVIRUS TYPES 16 AND 18 LATE REGIONS

The regulation of human papillomavirus (HPV) late gene expression is difficult to analyse because the late proteins L1 and L2 are only produced in the upper layers of terminally differentiated keratinocytes. However, for the minor capsid protein L2 of HPV types 1, 6, 11 and 16, rare mRNAs or cDNAs starting 3 of the E5 open reading frame (ORF) were previously described. In order to analyse whether the DNA region preceding the late ORFs (late upstream region, LUR) of HPV-16 and HPV-18 has promoter activity, transient transfection assays employing luciferase reporter constructs were performed. The results show that the LUR of HPV-16 and HPV-18 exhibits an orientation-dependent promoter activity in different cells. By analysing 3-deletion mutants of the HPV-16 LUR, we identified 78 bp within the sequence between the E5 and L2 ORFs to be critical for the promoter activity. Furthermore, the analysis of a 5-deletion mutant revealed a negative cis-regulatory element located within the E2 ORF. The HPV-16 early poly(A) signal is located downstream of the critical promoter region. Inactivation of this element by site-directed mutagenesis strongly enhanced luciferase activity. However, mutation of two potential TATA-binding protein (TBP) sites located within the critical promoter region did not abolish the activity. Altogether, these data indicate the possibility of a TATA-less promoter in the HPV-16 and HPV-18 LURs. Together with the early poly(A) signal, this potential promoter might be involved in the differentiation-dependent regulation of late gene expression.