Loss of HPV16 E2 Protein Expression Without Disruption of the E2 ORF Correlates with Carcinogenic Progression



Yuezhen Xue1, Diana Lim3, Liang Zhi2, Pingping He1, Jean-Pierre Abastado2, Françoise Thierry*, 1
1 Institute of Medical Biology, 8A Biomedical grove, Immunos, A*STAR, 138648, Singapore
2 SIgN (Singapore Immunology Network), 8A Biomedical grove, Immunos, A*STAR, 138648, Singapore
3 Department of Pathology. National University Hospital Singapore, Singapore


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© Xue et al.; Licensee Bentham Open.

open-access license: This is an open access article licensed under the terms of the Creative Commons Attribution Non-Commercial License (http: //creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted, non-commercial use, distribution and reproduction in any medium, provided the work is properly cited.

* Address correspondence to this author at 8A Biomedical Grove, #06-05, Immunos, 138648, Singapore; Tel: (65) 64070158; Fax: (65) 64642049; E-mail: francoise.thierry@imb.a-star.edu.sg


Abstract

Integration of the viral DNA in the cellular genome has been suggested to be critical in carcinogenic progression of HPV-associated cervical neoplasia. This event can be accompanied by disruption of the open reading frame (ORF) encoding the E2 repressor, thus leading to transcriptional up-regulation of the E6 and E7 viral oncogenes. At this stage, it is unclear whether disruption of the E2 ORF is mandatory for carcinogenic progression. We measured E2 RNA and protein expression in clinical samples of various grades of HPV16-associated cervical neoplasia and compared it with the status of the viral genome. RNA extracted from paraffin embedded tissues was hybridized to specific probes and quantified by the NanoString technology. Protein expression was appreciated by immunohistochemistry and the status of viral DNA was determined by in situ hybridization, all performed on serial sections of the same samples. E2 protein was found highly expressed in CIN1, CIN2 lesions where the HPV DNA was highly replicative, while it was decreased in more advanced grade lesions where replication is decreased or lost (CIN3 and SCC). In contrast, E2 transcripts could be elevated even in conditions of no or low expression of the protein, as found in the Caski cell line. Our data demonstrate that integration of the viral DNA in the cellular genome does not always lead to disruption of the E2 ORF and drastic reduction of E2 transcripts, while in contrast, expression of the E2 protein is always drastically reduced.

Keywords: HPV, transcription, IHC staining, E2, E6, E7, cyclin B1, viral genome status..