Immunohistological analysis of HPV L1 capsid protein and p16 protein in low-grade dysplastic lesions of the uterine cervix

Human papillomavirus (HPV) L1 capsid protein (L1) is associated with the productive phase of HPV infection. However, the expression of L1 and its relationship to p16 expression, a surrogate marker for HPV infection, are unknown. We examined the relationship between L1 and p16 expression in cervical intraepithelial neoplasia. Tissues were divided into four categories: regressive lesions (n = 48), progressive lesions (n = 40), and randomly selected CIN1-2 (n = 67) and CIN3 (n = 44). P16 positivity in the progression cases was significantly higher than that in the regression cases, and p16 positivity in the CIN3 cases was significantly higher than that in any other categories. L1 positivity was not significant between each category. The staining pattern was divided into the following four groups: L1−/p16−, L1+/p16−, L1+/p16+, L1−/p16+. The L1−/p16− pattern was significantly associated with the regression nature in CIN1-2. Some CIN3 cases showing a feature of L1+/p16+, which are still HPV-productive, are likely to exist. The combination of both L1 and p16 may be useful in the evaluation of the progression risk of low-grade cervical dysplasia.