Physical and Functional Mapping of a Tumor Suppressor Locus for Renal Cell Carcinoma within Chromosome 3p!!1

Using a functional genetic approach, we previously identified a novel genetic locus, NRC-1 (Wonpapillary /fermi Cell Carcinoma /). that medi ated tumor suppression and rapid cell death of renal cell carcinoma (RCC) cells in vivo. For these experiments, a defined subchromosomal fragment of human chromosome 3p was transferred into a sporadic RCC cell line via microcell fusion, and microcell hybrid clones were tested for tumorigenicity in vivo. The results indicated functional evidence for a novel tumor suppressor locus within the 3pl4-pl2 interval known to contain the most common fragile site of the human genome (FRA3B), the /•'///'/' gene, and the breakpoint region associated with the familial form of RCC. We now report the physical mapping of the NRC-1 critical region by detailed microsatellite analyses of novel microcell hybrid clones contain ing transferred fragments of chromosome 3p in the RCC cell background that were phenotypically suppressed or unsuppressed for tumorigenicity in vivo. The results limit the region containing the tumor suppressor locus within chromosome 3pl2. The FHIT gene, FRA3B, and the familial RCC breakpoint region were excluded from the NRC-1 critical region. Further more, the NRC-1 locus falls within a well-characterized homozygous deletion region of 5-7 Mb associated with a small cell lung carcinoma cell line, U2020, suggesting that a more general tumor suppressor gene may reside in this region.