Summary auto-generated
This study examines how human papillomavirus type 16 (HPV-16) integration and expression correlate with cellular changes during cervical cancer development. Researchers analyzed cervical intraepithelial neoplastic (CIN) lesions of varying grades and cervical tumors using PCR, RNA in situ hybridization, and immunohistochemistry. In high-grade CIN III lesions and tumors, the viral E2 gene was disrupted with minimal E2 transcripts, but E6-E7 oncogene transcripts were detectable at increasing levels. The E2 gene disruption indicates viral DNA integration into the host genome. Cellular changes accompanying this integration included altered cytokeratin profiles and reduced expression of cell adhesion molecules (integrins, E-cadherin) while CD44 expression increased. Notably, the Notch signaling protein showed striking relocalization from membrane/cytoplasmic localization in CIN III lesions to nuclear localization in tumors. These findings support the hypothesis that HPV-16 integration occurs in high-grade precursor lesions and that specific cellular molecular changes—particularly increased E6-E7 expression and altered Notch protein localization—distinguish the transition from precancerous to malignant cervical tumors.
Key findings
- HPV-16 E2 gene disruption, indicating viral integration, occurs in 15 of 16 CIN III lesions and all 19 tumors studied, whereas early-grade CIN I/II lesions retain episomal viral DNA
- E6-E7 oncogene transcript levels increase progressively during CIN evolution, with highest expression in invasive tumors, while E2 transcripts are largely absent in high-grade lesions
- Cell surface adhesion molecules (integrins α2, β1, β4 and E-cadherin) show significant downregulation during CIN progression, while CD44 expression increases substantially in high-grade lesions and tumors
- Notch protein undergoes dramatic relocalization from membrane/cytoplasmic distribution in CIN III lesions to nuclear accumulation in invasive tumors, marking a key molecular transition in malignant progression
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Abstract
We have matched a PCR assay which detects disruptions in the E2 reading frame of human papillomavirus type 16, with RNA in situ hybridization patterns and shown that in 15 out of 16 cervical intraepithelial neoplastic (CIN) III lesions and in 19 out of 19 tumours, the E2 gene is disrupted with no detectable E2 transcripts. Varying levels of E6-E7 transcripts are detected in CIN III lesions, with stronger signals in tumours. The cytokeratin profile of most tumours: cytokeratin 10-, 14- and 19-positive and 4-, 13- and 18-negative, is also detected in CIN III lesions. The changes in levels of alpha 2, beta 1 and beta 4 integrins, CD44 and E-cadherin occur during the evolution of high-grade CIN lesions. Increases in the levels of expression of CD44 and E6-E7 transcripts, coupled with changes in the cellular localization of the Notch protein, define the transition from CIN III lesions to tumours.