Expression of phosphorylated histone H2AX (γ-H2AX) in normal and neoplastic squamous epithelia of the uterine cervix: an immunohistochemical study with epidermal growth factor receptor

Abstract

The histone γ-H2AX is a marker of activated DNA damage and is overexpressed in different cancers and their precursor lesions, indicating a role in oncogenic transformation. Epidermal growth factor receptor (EGFR) is overexpressed in many kinds of epithelial neoplasms. This study aimed to determine whether immunohistochemical expression of γ-H2AX is involved in the progression of the morphological spectrum from normal squamous cervical epithelia (NE, n=33) to cervical intraepithelial neoplasia (CIN; CIN1, n=9; CIN2/3, n=33) and cervical invasive squamous cell carcinoma (ISCC, n=33), whether γ-H2AX expression follows the pattern of proliferation of atypical squamous cells as shown by EGFR immunoreactivity, and whether it is correlated with clinicopathologic variables in ISCC. Immunostaining for both the factors was scored semiquantitatively for moderate and strong intensities. Gamma-H2AX and EGFR expression, respectively, increased from NE and CIN1 to CIN2/3 and ISCCs significantly (P=0.0001, respectively). Gamma-H2AX reactivity was found in the nuclei of the cells of the upper epithelial levels and the cells of basal/parabasal type in variable quantities in NE and CIN; expression of γ-H2AX was seen in the nuclei of ISCC including keratinizing cells in horn pearls. EGFR staining was mainly membranous and noted in basal/parabasal cells in NE and atypically proliferating keratinocytes in CIN and nonkeratinizing cells of ISCC. In addition, immature squamous metaplasias were decorated by the antibodies used. Immunoscores for γ-H2AX and EGFR, respectively, did not differ between International Federation of Gynecology and Obstetrics stages I and II, keratinizing and nonkeratinizing ISCC, and CIN2/3 and ISCC. However, expression patterns were different for both the factors, suggesting their involvement in different biological mechanisms, with regard to γ-H2AX apart from proliferation. Overexpression of γ-H2AX in CIN2/3 and ISCC of the uterine cervix reflects the neoplastic transformation of cervical squamous epithelia in reaction to increased DNA-damage and supports the classification of dysplasia into low-grade squamous intraepithelial lesions and high-grade squamous intraepithelial lesions.