Endonuclease-resistant DNA: a novel histochemical marker for cervical intraepithelial neoplasia and cervical carcinoma.

The diagnosis of cervical intraepithelial neoplasia (CIN) has low interobserver reproducibility. The pathogenesis of human papillomavirus (HPV) from infection to high-grade CIN is well understood. In benign lesions, HPV-DNA is often packaged into virions, whereas malignant transformation disrupts virion assembly. It is conceivable that if cervical lesions were exposed to endonuclease digestion, HPV virions would alter nuclear susceptibility to DNA degradation. We propose that susceptibility to endonuclease digestion can serve as a simple marker to identify CIN grade. From paraffin-embedded tissue blocks, condyloma accuminata, CIN I-III, and cervical carcinoma cases were identified. Sections were placed in a bath containing DNAse I for DNA digestion. Residual DNA was stained by a Feulgen process. Endonuclease-resistant DNA (erDNA) staining was correlated to disease grade. In addition, 10 HPV (+) patients whose infection regressed and 8 whose infection progressed to CIN II or above had their initial HPV lesions stained for erDNA. erDNA was observed in 81% condylomas and 80% CIN I cases. All CIN II, III, and cancer cases were endonuclease sensitive with 100% of lesions showing no staining. Eighty percent of HPV lesions that regressed had erDNA staining, whereas 75% lesions that progressed had no erDNA staining. The spectrum of cervical disease caused by HPV has different susceptibilities to endonuclease digestion, which may aid in the diagnosis of CIN. Furthermore, in our small pilot study, erDNA status was associated with the clinical outcomes. Prospective studies are needed to confirm this observation. erDNA status is a promising novel biomarker.