Expression of FHIT protein and allelic deletion at FHIT locus in primary cervical carcinoma tissues

Kim, Su Yeon; Seong, Yeon Sun

Abstract

Allelic deletions involving the short arm of chromosome 3(3p13-21.1) have been observed frequently in cervical carcinomas. Recently the fragile histidine triad(FHIT) gene was cloned and mapped to this chromosomal region(3p14.2). From various studies involving tumor cell lines and primary cancers, the FHIT gene has been presumed to be a candidate for tumor suppressor gene involving various tumors. In FHIT gene, the most common aphidicolin-inducible fragile site, FRA3B exists and the FRA3B has been considered as a region of the spontaneous integration site of HPV 16. In order to elucidate the role of the FHIT in carcinogenesis of cervical cancer, this study was designed to investigate both the expression of FHIT protein in normal, preinvasive and invasive cancer samples employing immunohistochemical study and allelic loss of FHIT gene locus against several microsatellite markers employing the PCR analysis. Immunohistochemical studies of FHIT protein revealed following features. In normal ectocervical squamous epithelium, the expression of FHIT was relatively weak and confined to the basal layer, but in normal endocervical glandular epithelium it was very strong. The expression of FHIT was reduced as the tumor progressed from early lesion to invasive cancer. The koilocytosis was associated with diminished expression of FHIT protein. The study of allelic loss of FHIT gene locus was undertaken against two intragenic (D3S1300, D3S1234) and one extragenic (D3S1295) microsatellite markers. The 5th intron, D3S1300, showed allelic change in 6 of 15 assays and 7th intron, D3S1234 showed allelic change in 10 of 29 assays. There was no apparent LOH from 29 assays in D3S1295. In conclusion, the expression of FHIT protein was markedly reduced or absent in cervical squamous cell carcinoma and the chromosome breakage in FHIT region might be related to the diminished expression of FHIT. On the basis of the reduced expression of FHIT and its encompassment of FRA3B region, it is suggested that disruption of FHIT, a putative tumor suppressor gene, might be the mechanism by which HPV infection enhances cervical tumorigenesis and clonal outgrowth.