The constitutive fragile site at chromosomal band 3p14.2, FRA3B, is th
e most active common fragile site in the human genome, We have localiz
ed aphidicolin-induced breakpoints to two distinct clusters, separated
by 200 Kb, in FRA3B (Paradee et al., 1996). Sequence analysis of thes
e regions identified two polymorphic microsatellite markers immediatel
y adjacent to each of these breakpoint clusters. In this report we hav
e used these two new microsatellites and 14 additional 3p microsatelli
tes to analyse chromosome 3p breakage and loss in 94 sporadic RCC samp
les, including nonpapillary, papillary and oncocytomas, We have found
heterozygous loss of 3p14 sequences in >60% of the RCC samples, includ
ing both clear cell and papillary renal cell carcinomas, We have found
frequent breakage in the region immediately surrounding FRA3B, demons
trating that FRA3B does play a role in chromosome breakage and loss in
RCC, In contrast to other reports, >50% of the papillary tumors also
showed LOH of 3p markers, We also observed microsatellite instability
(MIN) with most of the tested markers in seven of eight oncocytomas an
d one of 69 clear cell carcinomas, The MIN in some oncocytomas was of
the RER + (replication error) type I phenotype, None of the five 3p14.
2 markers detected any homozygous deletions in tumor samples, but 69/9
4 (73%) of the tumors had LOH for the region, which includes the recen
tly identified FHIT gene.