Frequent Inactivation of Secreted Frizzled-Related Protein 2 during the Development of Cervical Carcinoma: Identification of Susceptible Alleles and Clinical Implications

Abstract

ABSTRACT In this study, importance of SFRP2, wnt stem cell renewal pathway antagonist, in the development of cervical cancer (CACX) was evaluated Alterations (expression/ methylation/ deletion) of SFRP2 were analysed in primary cervical lesions of different clinical stages followed by their correlation with different clinicopathological parameters. Then, susceptible allele(s) of SFRP2 was identified through case control study followed by and in vitro validation. The mRNA expression of SFRP2 was gradually reduced with progression of CACX. In immunohistochemistry, SFRP2 membrane expression was mainly present in the spinous layers of normal cervical epithelium and its reduced protein expression in CACX samples showed concordance with mRNA expression. Frequent deletion/ methylation of SFRP2 were seen to be associated with development of cervical cancer. Methylation of SFRP2 was prevalently associated with early invasive lesions (stage I/II) while, deletion with late invasive lesions (stage III/IV). Overall alterations (deletion/ methylation) of SFRP2 were significantly increased from premalignant CIN to stage-I/II samples followed by comparable change to the next stage (stage III/IV) samples. Moreover, deletion and/or methylation of SFRP2 were associated with poor prognosis of the patients. In a case control study, out of its seven microsatellite alleles infrequent SFRP_CA15/16 alleles along with frequent SFRP_CA17 allelewere found to be associated with CACX development. Comparatively reduced expression (mRNA/ protein) of SFRP2 was seen in the tumor adjacent normal cervical epithelium having SFRP_CA15/16 alleles than the other alleles. This has been further validated in in vitro luciferase promoter activity assay where SFRP_CA16 repeat showed high reduced activity followed by SFRP_CA15 repeat than the other repeats. Thus, our data showed that presence of the infrequent susceptible alleles along with deletion/methylation might have synergistic effect on frequent inactivation of SFRP2 during development of CACX.