Our data indicate that LOH at chromosome 3p14.2-p25 is specific for conventional RCC and that loss of one allele of both the VHL and FHIT genes occurs in early stage of tumorigenesis.
We conclude that 3p LOH is a universal phenomenon in RCC, but has different underlying mechanisms, molecular targets, and implications in the different morphotypes, although FHIT inactivation may play a role in both cRCC and chRCC tumorigenesis.
Hemizygous deletions of the fragile histidine triad (FHIT) gene at human chromosome band 3p14.2 and down-regulation of its gene product are found in the majority of renal cell carcinomas (RCCs).
The results indicated functional evidence for a novel tumor suppressor locus within the 3p14-p12 interval known to contain the most common fragile site of the human genome (FRA3B), the FHIT gene, and the breakpoint region associated with the familial form of RCC.
Also, the 3p14.2 chromosome breakpoint of the familial clear cell kidney carcinoma-associated translocation, t(3;8)(p14.2;q24), disrupts one FHIT allele between exons 3 and 4, fulfilling one criterion for a familial tumor suppressor gene: that one allele is constitutionally inactivated.
Northern analyses with the exon 2a of the familial and the metastatic RCC demonstrates concurrent loss of expression of a 4.4 kb transcript with the loss of the E2a sequence, suggesting that exon 2a of the FHIT gene may play an important role in the oncogenesis of renal cell carcinoma.
Normal FHIT transcripts in renal cell cancer- and lung cancer-derived cell lines, including a cell line with a homozygous deletion in the FRA3B region.
In addition to two cases from a t(3;8) family, only three out of 100 sporadic nonpapillary RCC showed a breakpoint within the FHIT region, whereas 94 tumors showed a deletion breakpoint proximal to the FHIT gene.
The FHIT locus is composed of ten exons distributed over at least 500 kb, with three 5' untranslated exons centromeric to the renal carcinoma-associated 3p14.2 breakpoint, the remaining exons telomeric to this translocation breakpoint, and exon 5 within the homozygously deleted fragile region.
Human chromosome band 3p14 contains two tightly linked cytogenetic markers of broad interest, FRA3B and the t(3;8) breakpoint associated with hereditary renal cell carcinoma (RCC).