Activation of Wnt-β-catenin pathway in basal-parabasal layers of normal cervical epithelium comparable during development of uterine cervical carcinoma

In this study, importance of Wnt-beta-catenin pathway in the development of uterine cervical carcinoma was evaluated. For this purpose, the profiles (expression/methylation/deletion) of beta-catenin, p-beta-catenin (Y654), Wnt3a, and APC were studied in disease free normal cervical epithelium (n = 9), adjacent normal cervical epithelium of primary tumors (n = 70), CIN (n = 28), CACX (n = 102) samples, and two CACX cell lines (HeLa and SiHa). Immunohistochemical analysis revealed high/medium (74-95%) expression of beta-catenin/p-beta-catenin (Y654) and Wnt3a and low expression (23-26%) of APC in proliferating basal-parabasal layers contrary to differentiated spinous layer in normal cervix irrespective of HPV16 infection. The expression profile of the genes in the basal-parabasal layers did not change significantly during development of CACX. High (66%) promoter methylation of APC was seen in basal-parabasal layers and the cervical lesions (42-69%), unlike in spinous layers (25%). The promoter methylation status of APC was validated by in vitro demethylation experiments using 5-aza-dC in CACX cell lines. However, additional deletion of APC was significantly increased from CIN (12%) to stage I/II (40%) and became comparable in stage III/IV (48%) of the tumor. Patients with alterations (deletion/methylation) of APC and high/medium expression of Wnt3a/beta-catenin/p-beta-catenin (Y654) showed significantly poor survival. Thus our data indicate that cumulative effect of Wnt3a overexpression and APC inactivation are needed for overexpression of beta-catenin during the development of CACX.