Refined mapping of the region of loss of heterozygosity on the long arm ofchromosome 7 in human breast cancer defines the location of a second tumorsuppressor gene at 7q22 in the region of the CUTL1 gene

In breast cancer, loss of heterozygosity (LOH) has been described on the lo ng arm of chromosome 7, at band q31, suggesting the presence of a tumor sup pressor gene in this region, In this study, we have identified a second reg ion of LOH on 7q, at band 7q22. Deletion of genetic material at 7q22 was fo und in all tumor types and grades and was associated with increased tumor s ize. The region of LOH at 7q22 in every case included one or more of three polymorphic markers that are located within the CUTL1 gene. LOH of 7q22 has also been documented in the case of human uterine leiomyomas (Zeng et al., 1997; Ishmad et al., 1997), Interestingly, in both leiomyomas and mammary tumors induced in transgenic mice expressing the Polyomavirus (PyV) large T (LT) antigen, immunocomplexes of CUTL1 and PyV LT antigen were detected (W ebster et al., 1998), Altogether, genetic data in human breast cancer and b iochemical analyses in breast tumors from transgenic mice suggest that CUTL 1 is a candidate tumor suppressor gene.