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CD72 is a membrane protein that involves in the negative regulation of B cells. CD72 is also expressed in many other cell types and its function is still unknown. In the analysis of cDNAs from tumor tissues, we have found that mutations exist in cDNA clones from several forms of tumor including thyroid follicular carcinoma, leukemia, chondrosarcoma and endometrial adenocarcinoma. Human CD72 gene has nine exons and contains variable numbers of tandem repeat in Intron 8. When normal human population was investigated, one or two tandem repeats were found. In another region of Intron 8, allele with a deletion of four nucleotides was found (CACT- allele). We investigated if the alleles of CD72 are associated with kidney cancer. 45 kidney tumor samples, 66 tissue samples of normal individuals were analyzed by polymerase chain reaction to determine the alleles. The tandem repeat of Intron 8 is not associated with kidney cancer. However, 2 out of 33 (6%) tumor tissues were found to have microsatellite instability in the tandem repeat region. We also investigated the association of CACT alleles with kidney cancer. CACT+ is negatively associated with kidney cancer (3 out of 45 vs 23 out of 66 normal samples, 2-tailered Fisher’s exact test, P<0.0005). In 7 of the 33 tumor tissues (21.2%), loss of heterozygosity was found. Our results suggest that CD72 is associated with kidney cancer and we thus propose that CD72 is a new tumor suppressor gene.

[Proc Amer Assoc Cancer Res, Volume 46, 2005]