DETAILED DELETION MAPPING OF CHROMOSOME 17Q IN OVARIAN AND BREAST CANCERS - 2-CM REGION ON 17Q21.3 OFTEN AND COMMONLY DELETED IN TUMORS

Using 11 restriction fragment length polymorphism markers, we examined loss of heterozygosity on the long arm of chromosome 17, where one or more genes responsible for hereditary breast and ovarian cancers may be present, in sporadic forms of 94 ovarian and 246 breast cancers. Lo ss of heterozygosity was observed in 33 of 84 (39.3%) ovarian and in 8 8 of 214 (41.1%) breast cancers that were informative with at least on e marker. Detailed deletion mapping of chromosome 17q in these cancers identified two distinct, commonly deleted regions. One was located be tween 17q12 and 17q21.3 and the other between 17q25.1 and 17q25.3. In breast cancers, the proximal commonly deleted region was between two l oci defined by markers CI17-701 and CI17-730 at 17q21.3, which are 2.4 cM apart. This segment overlaps the region that includes the putative gene for hereditary breast and ovarian carcinomas. The results sugges t that at least two tumor suppressor genes associated with sporadic ov arian and breast cancers are present on chromosome 17q and that one of them may be the same gene that is responsible for the hereditary form .