Loss of expression of the DRR I gene at chromosomal segment 3p21.1 in renal cell carcinoma

Consistent deletion of DNA sequences in chromosomal band 3p21 observed in a variety of human tumors suggests the presence of one or more tumor suppres sor genes within this region. Previously, we reported on the construction o f two distinct cosmid contigs and our identification of several new genes w ithin 3p21.1. In our search for tumor suppressor genes from this region, we have cloned a gene that we have called DRR I (downregulated in renal cell carcinoma). The gene was first mapped to 3p21.1 by fluorescence in situ hyb ridization analysis. Further analysis of yeast artificial chromosome clones in 3p14.2-p21.1 refined its localization. DRR I spans about 10 Kb of genom ic DNA with a 3.5-Kb mature transcript The putative protein encoded by this gene is 144 amino acids and includes a nuclear localization signal and a c oiled domain. The gene showed loss of expression in eight of eight renal ce ll carcinoma cell lines, one of seven ovarian cancer cell lines, one of one cervical cancer cell line, one of one gastric cancer cell line, and one of one non-smalt-cell lung cancer cell line. Southern blot analysis did not s how any altered bands, indicating that gross structural changes or deletion s did not cause the loss of expression. This gene was also found to have re duced expression in 23 of 34 paired primary renal cell carcinomas. Mutation al analysis detected three polymorphic sites within the gene, but no point mutations were identified in the 34 primary tumors. However, we did detect base substitutions in 4 of 12 cell lines that had undetectable expression o f the gene. We also transfected the gene into DRR I-negative cell lines and observed clear growth retardation. Our results suggest that loss of expres sion of the DRR I gene may play an important role in the development of ren al cell carcinoma and possibly other tumors. Genes Chromosomes Cancer 27:1- 10, 2000. (C) 2000 Wiley-Liss, Inc.