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J Virol, January 1998, p. 749-757, Vol. 72, No. 1
Unit of Molecular Pathology, Department of
Pathology, University Hospital Vrije Universiteit, 1081 HV Amsterdam,
The Netherlands,1 and
Department of
Biochemistry and Molecular Genetics, The University of Alabama at
Birmingham, Birmingham, Alabama 35294-00052
Received 18 June 1997/Accepted 3 October 1997
Organotypic cultures of human keratinocytes provide a useful model
system to study human papillomavirus (HPV)-host cell interactions. In
this study, we analyzed organotypic cultures of two HPV type 16 (HPV16)
(FK16A and FK16B)- and two HPV18 (FK18A and FK18B)-transfected keratinocyte cell lines through the process of immortalization in
vitro. For FK16A and FK18B cells, passages of both mortal cells in
their extended life span and subsequent immortal stages were studied.
Mortal cells of FK16A and FK18B showed a morphology reminiscent of mild
to moderate dysplasia, whereas in their immortal descendants, severely
dysplastic features were observed. Immortal FK18A cells were mildly to
moderately dysplastic, while FK16B cells were severely dysplastic. The
increasing degrees of dysplasia were associated with a decreasing
expression of differentiation markers cytokeratin 10 and profilaggrin.
All raft cultures expressed E6-E7 mRNAs in the basal layer, while the
amount of viral transcripts in the suprabasal cells was in general
proportional to the degree of dysplasia. In all cases, E6-E7
transcription and dysplastic features were highly correlated with
cellular proliferation, as assessed by Ki-67 (MIB-1) antigen
expression. Moreover, high levels of E6-E7 transcription and expression
of p21cip1 protein in the basal layer seemed to be mutually exclusive.
We conclude that expression of E6-E7 in the basal cells associated with
increased proliferation in the absence of detectable p21cip1 protein is
apparently necessary but not sufficient for immortalization, or for the
loss of terminal differentiation, for which yet to be discovered
additional events are required. The model system described in this
study provides a valuable tool to analyze alterations in viral
transcription regulation during HPV-mediated cell transformation.
0022-538X/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Viral E6-E7 Transcription in the Basal Layer of
Organotypic Cultures without Apparent p21cip1 Protein Precedes
Immortalization of Human Papillomavirus Type 16- and 18-Transfected
Human Keratinocytes
*
Corresponding author. Mailing address: Dept. of
Biochemistry and Molecular Genetics, The University of Alabama at
Birmingham, 508 McCallum Basic Health Sciences Bldg., 1918 University
Blvd., Birmingham, AL 35294-0005. Phone: (205) 975-8300. Fax: (205)
975-6075. E-mail: lchow{at}bmg.bhs.uab.edu.
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