Human papillomavirus E6 and E7 mRNA testing in detection of uterine cervical lesions

Abstract

Background: HPV DNA testing, commonly used for cervical cancer screening along with cytology test has shown high sensitivity but low specificity. Recently, it was suggested that detection of E6/E7 oncogene transcripts of high-risk HPV types shows higher specificity for detection of high grade cervical squamous lesions but less sensitivity due to few HPV types targeted. There is still no reliable method with equal high sensitivity and specificity for the detection of HPV in cervical intraepithelial neoplasia (CIN) and cancers. Methods: Primers for real-time PCR to detect HPV E7 mRNA of HPV types 16, 18, 31, 33, 35, 39, 45, 51, 52, 53, 56, 58, 59, 66, 68, and 69 were developed and the clinical application was evaluated and compared to commercial HPV DNA and mRNA assays. In total of 180 Thin Prep® samples, the remaining fluid after the cytology slide preparation were tested with Goodgene HPV DNA chip (DNA assay), NucliSENS EasyQ® HPV E6/E7 mRNA assay (EasyQ assay) and real-time PCR with new HPV E7 primers, which we developed (mRNA qRT-PCR). The sensitivity and specificity of each test were calculated with histologically CIN2+ (CIN, grade 2 or higher) lesions as the disease endpoint. Results: Among them, 54 (30%) were positive for mRNA qRT-PCR while 127 (71%) and 54 (30%) were positive for DNA assay and EasyQ assay, respectively. DNA assay was positive in all abnormal cytology cases. In cytology groups of squamous cell carcinoma (SCC), high grade squamous intraepithelial lesion (HSIL), atypical squamous cells – cannot exclude HSIL (ASC-H), low grade squamous intraepithelial lesion (LSIL) and atypical squamous cells of undetermined significance (ASC-US), the mRNA qRT-PCR test showed 100%, 100%, 100%, 25%, and 18% positivity while EasyQ assay showed 73%, 74%, 60%, 56%, and 32% positivity, respectively. In normal cytology cases, the positivity rates were 3%, 7% and 51% by mRNA qRT-PCR, EasyQ assay and HPV DNA assay, respectively. For the detection of CIN2+ lesions, the sensitivity of mRNA qRT-PCR and DNA assay was 100% each, while EasyQ assay showed sensitivity of 72%. HPV E7 mRNA qRT-PCR showed the highest specificity (92%) among the three tests (DNA assay: 36% and EasyQ assay: 83%). Conclusion: It is suggested that HPV E7 mRNA qRT-PCR can overcome the shortcoming of low specificity in DNA assay as well as the low sensitivity of EasyQ assay for clinical detection of high grade cervical lesions and malignancies.