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Antimicrobial Agents and Chemotherapy, July 2000, p. 1869-1873, Vol. 44, No. 7
Departments of Microbiology and
Immunology1 and
Dermatology,2 University of Texas
Medical Branch, Galveston, Texas; Department of Pathology,
University of Cambridge, Cambridge, United
Kingdom3; and 3M Pharmaceuticals,
St. Paul, Minnesota4
Received 13 December 1999/Returned for modification 13 March
2000/Accepted 25 April 2000
Imiquimod (IQ) has been successfully used in treatment of genital
warts. In clinical settings, patients responded well but wart reduction
rates varied. Our aim was to find a correlation between clinical
responses and pretreatment (constitutive) levels of genes that might be
involved in the molecular action of IQ. Since IQ is a cytokine inducer,
we analyzed levels of expression of genes of the JAK/STAT signaling
pathway and their inhibitors as well as interferon response factors
(IRFs) in pretreatment biopsy specimens from complete responders (99 to
100% wart reduction rate) versus incomplete responders (75 to 92%
wart reduction rate) by reverse transcription-PCR. We found that mRNA
levels of signal transducer and activator of transcription 1 (STAT1)
and IRF1 were higher in complete responders than in incomplete
responders. Incomplete responders expressed larger amounts of STAT3,
IRF2, and protein inhibitor of activated STAT1 (PIAS1) mRNAs compared
to complete responders before IQ treatment. We hypothesize that
high-level expression of STAT1 and IRF1 is advantageous for a better IQ
response. The observed differences in constitutive mRNA levels of these genes may be the consequence of alterations in cellular differentiation and/or variable expression of endogenous interferons. Previous in vitro
studies showed that keratinocyte differentiation coordinates the
balance between positive and negative signals along the JAK/STAT pathway by regulating the IRF1:IRF2 and STAT1:PIAS1 ratios and thus
affecting induction of IQ-inducible genes. Specifically, differentiation supports constitutive expression of STAT1 and IRF1
mRNAs but not expression of IRF2 and PIAS1. Our data are in good
agreement with studies that showed the importance of STAT1 in cytokine
induction and activation of interferon-responsive genes by IQ.
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Copyright © 2000, American Society for Microbiology. All rights reserved.
Correlation between Pretreatment Levels of
Interferon Response Genes and Clinical Responses to an Immune Response
Modifier (Imiquimod) in Genital Warts
*
Corresponding author. Mailing address: Department of
Microbiology and Immunology, University of Texas Medical Branch,
Galveston, TX 77555-1070. Phone: (409) 772-8145. Fax: (409) 747-6869. E-mail: iarany{at}utmb.edu.
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