[Sequence analyses of aberrant FHIT transcripts in gastric cancer cell lines]

The fragile histidine triad (FHIT) gene located at chromosome 3p14.2, is a candidate tumor suppressor gene often involved in various tumors. Homozygous deletions, lack or reduced expression of FHIT protein, and alteration of its transcription were frequently observed in several types of primary human cancers and cell lines. In the present study, we examined the expression profiles of aberrant FHIT transcripts to explore the role of FHIT gene in gastric carcinogenesis.

In 6 gastric cancer cell lines, nested reverse transcription-polymerase chain reaction (RT-PCR) and cDNA sequence analyses were performed to detect and characterize the aberrant FHIT transcripts.

In addition to the wild-type FHIT transcript, small-sized transcripts with various numbers and lengths were observed in all of the cell lines examined. cDNA sequence analysis confirmed that different types of truncated transcripts included exonic deletions, insertions of intron 5 sequences between exons, and combinations of both. Most of these transcripts lacked exon 5 in which translation initiation codon is located. Aberrant transcripts with partial exonic deletions due to activation of cryptic splice sites were also observed in 5 cell lines. Additionally, multi-step splice patterns indicative of additional downstream processing, were observed in several cancer lines.

These results suggest that the aberrant FHIT transcripts in gastric cancer cell lines results from faulty splicing, including exon skipping, selection of cryptic splice site, and additional downstream splice processing.