Abnormal FHIT transcripts found in both lung cancer and normal lung tissue

Occurrence of abnormal transcripts of the FHIT (fragile histidine triad) gene has been reported in various types of cancer. On the other hand, aberrant transcripts are sometimes found in non-neoplastic tissues, so the relationship between the presence of abnormal transcripts of the FHIT gene and cancer pathogenesis is controversial. We investigated alterations in the FHIT locus, detected by nested reverse transcription-polymerase chain reaction and/or allelic status, in 88 primary lung cancers and normal lung tissues, and 22 normal lung tissues with metastasitic lung cancer as a control. The frequencies of abnormal transcripts were 59% in lung cancer, 35% in paired normal lung, and 64% in normal control lung; the difference in frequencies between lung cancer and paired normal lung was significant, while that between lung cancer and normal control lung was not. Sequence analysis revealed that there were no cancer-specific abnormal transcripts entirely missing two or more exons, nor were the abnormal transcripts of lung cancer identical with those of paired normal lung in the same individual. Furthermore, we found no correlation between loss of heterozygosity in the FHIT locus and occurrence of abnormal FHIT transcripts. These results suggest that the presence of abnormal FHIT transcripts, in terms of their frequency and variety, is not cancer-specific in lung carcinogenesis, and the abnormality may be mainly due to abnormal splicing and processing of the transcripts. To estimate the precise function of the FHIT gene, further study of the FHIT protein in lung carcinogenesis is needed.