FHIT oncosuppressor gene expression profile in human anal cancers

The FHIT gene, a member of the histidine triad gene family, is a tumor suppressor gene exhibiting deletions in the majority of human cancers. Aberrant transcripts of this gene have been found in about 50% of esophageal, stomach and colon carcinomas. Little is known about the molecular mechanisms involved in malignant transformation of the lining cells of the anus. In this study FHIT gene expression was investigated in this particular kind of human cancer. FHIT expression was comparatively analyzed at the mRNA level, by RT-PCR, in squamous anal cancers, normal anal tissue and peripheral blood samples. cDNA analyses showed variability in FHIT transcripts, without apparent effects on the predicted amino acid sequence. These different FHIT mRNAs could represent transcripts from an alternative splicing event. Our data indicate that the FHIT mRNA detected in anal cancers and in normal samples is heterogeneous. Immunohistochemical data suggest that the Fhit protein is expressed only in a fraction of the tumor cells, while it is strongly expressed in the epithelial cells of glands of the normal anal mucosa. The absence or poor expression of the Fhit protein in anal cancers suggests a role for this tumor suppressor gene product, as a risk factor, in the onset of this human cancer, as reported before for other human gastrointestinal tumors.