We have identified a >600-kb region at 16q23.2 that is homozygously deleted from malignant ovarian ascites using representational difference analysis. Overlapping homozygous deletions were also observed in the colon carcinoma cell line HCT116 and a xenograft established from the small cell lung cancer cell line WX330. This region coincides with that described previously by others as showing loss of heterozygosity in prostate and breast cancers (C. Li et al., Genes Chromosomes Cancer, 24:

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... , 1999; A. Latil et al., Cancer Res., 57: 1058-1062, 1997; K. Driouch et al., Genes Chromosomes Cancer, 19: 185-191, 1997; A. Iida et al., Br. J. Cancer, 75: 264-267, 1997). In addition, the minimally deleted region spans the common fragile site FRA16D. We have constructed a 700-kb physical map encompassing the deleted region. By fluorescence in situ hybridization of aphidicolin-induced metaphase chromosomes, we have preliminary data to suggest that P1-derived bacterial artificial chromosome clones from the contig lie on both sides of FRA16D. This is confirmed by extensive fluorescence in situ hybridization analysis of the region reported in the accompanying article (M. Mangelsdorf et al., Cancer Res., 60: 1683-1689, 2000) and is consistent with an involvement of this common fragile site in the loss of 16q23.2 material in various cancer types. The minimally deleted region of approximately 210 kb has been characterized using our own markers and public domain markers. Eleven distinct expressed sequences mapped to the region, providing a basis for identifying the predicted tumor suppressor gene in this region.