Analyzing the FHIT Gene by RT-PCR, Western Blotting, and Immunohistochemistry.

FHIT (fragile histidine triad) is a tumor-suppressor gene located at chromosome band 3p14.2. The genomic locus, which is greater than 1 Mb, contains 10 small exons that make up the 1.1-kb FHIT cDNA. The coding region starts in exon 5 and stops in exon 9, producing a 16.8-kDa cytoplasmic protein. The FHIT locus contains the hereditary renal cell carcinoma (RCC) t(3;8) translocation, and also encompasses the FRA3B common fragile region (for review, 1). Numerous studies have proven that the FHIT gene is inactivated by deletions in both primary tumors and cell lines derived from head and neck, stomach, lung, and kidney cancers (2-6). Since FHIT is inactivated in so many cancers, it is essential to learn its normal function and analyze how the loss of its function contributes to the progression and development of cancer. For example, an early event in the lungs of a smoker is breakage at the FHIT locus, causing a reduced or absent FHIT protein expression in the preneoplastic lesions. Compensation for the functional loss of FHIT via a recombinant, nonfragile FHITgene may prove therapeutically useful (7,8). Our studies have also shown that the FHIT gene is altered or absent in the majority of transitional-cell carcinoma (TCC) cases of the bladder examined (9). Through the utilization of molecular techniques such as those described here, FHIT alterations may be detected in an early stage of cancer, and thus prove to be a useful diagnostic tool to prevent cancer progression.