Detection of human papillomavirus DNA in formalin-fixed tissues by in situ hybridization after amplification by polymerase chain reaction

The authors describe the detection of human papillomavirus (HPV) 16 DNA in paraffin-embedded, formalin-fixed tissues of cervical squamous intraepithelial lesions (SILs) by in situ hybridization after amplification by the polymerase chain reaction (PCR). Using conventional in situ hybridization and a biotin-labeled probe, variable numbers of superficial cells and none of the basal cells in the SILs showed detectable HPV 16 DNA. When the in situ assay was done after amplification, increased numbers of superficial cells had detectable HPV DNA, and the hybridization signal was much more intense. HPV DNA was also detected in basal and parabasal cells at the site of the lesion whereas not detectable in directly adjacent, normal squamous epithelium. Amplified HPV DNA was demonstrated in formalin-fixed SiHa cells using a biotin-labeled probe, demonstrating the ability to detect one copy of HPV 16 DNA. This technique should allow for direct visualization in cells of other DNA sequences of low copy number from achival specimens otherwise undetectable by conventional in situ hybridization analysis.