Frequent homozygous deletions in the FRA3B region in tumor cell lines still leave the FHIT exons intact.

FRA3B at human chromosomal band 3p14.2 is the most active common fragile site in the human genome. The molecular mechanism of fragility at this region remains unknown but does not involve expansion of a trinucleotide or minisatellite repeat as has been observed for several of the cloned rare fragile sites. Deletions and rearrangements at FRA3B have been observed in a number of distinct tumors. The recently identified putative tumor suppressor gene FHIT spans FRA3B, and various groups have reported identifying deletions in this gene in different tumors. Using a high density of PCR amplifiable markers within FRA3B searching for deletions in the FRA3B region, we have analysed 21 tumor cell lines derived from renal cell, pancreatic, and ovarian carcinomas. We found a commonly deleted region in the renal cell and ovarian carcinoma cell lines located in the middle of an HPV16 viral integration site. Despite the presence of deletions in the FRA3B region in most of the cell lines, we did not detect alterations in FHIT exons in any of the cell lines examined. Thus, deletions of 3p14.2 in these carcinoma cell lines may simply reflect instability of the FRA3B region during tumor progression.