Evaluation of p16INK4a and pRb expression in cervical squamous and glandular neoplasia

p16(INK4a) is known to play a critical role as a negative regulator of cell cycle progression and differentiation by controlling the activity of the tumor-suppressor protein pRb. The present study evaluated the expression of p16(INK4a) and pRb in cervical squamous and glandular neoplasia. Immunohistochemical staining was performed for p16(INK4a) and pRb in formalin-fixed, paraffin-embedded tissue sections of the uterine cervix using an indirect immunoperoxidase method. p16(INK4a) staining was detected in 7 of 108 sections (6.5%) of normal squamous mucosa, in scattered ciliated columnar cells in 33 of 88 sections (37.5%) of normal endocervical glands, in 9 of 30 sections (30%) with Nabothian cysts, and in 4 of 4 areas (100%) of tubal metaplasia. In contrast, strong p16(INK4a) staining was found in 13 of 18 cases (72.2%) of cervical intraepithelial neoplasia (CIN) I and in all cases of CIN II/III (n = 46), squamous cell carcinoma (n = 18), endocervical glandular dysplasia (n = 10), adenocarcinoma in situ (n = 23), and invasive adenocarcinoma (n = 12). pRb expression was detected in each diagnostic category; however, the proportion of pRb-positive cells was relatively decreased in high-grade premalignant and malignant lesions of the squamous and endocervical mucosa and showed a generally inverse correlation with the expression of p16(INK4a) at the tissue level. These findings confirm a correlation between the expression of p16(INK4a) and pRb in cervical neoplasias and indicate that p16(INK4a) is a specific marker for premalignant and malignant lesions of the squamous and endocervical mucosa.