Loss of one chromosome #13 during development of a polyposis tumor

A cell panel from six different familial cancers, where both normal and tumor tissues were available, was examined for genotypic changes with polymorphic DNA probes. Seventeen probes were tested, representing chromosomes #1, #2, #5, #6, #13, #14, #17, and #19. One probe, p7F12 (D13S1, at 13q12-q14) revealed loss of heterozygosity in two tumors: an osteosarcoma from a patient with retinoblastoma that had been included as a control, and one polyposis tumor that had been established in nude mice from a duodenal carcinoma biopsy. Loss of heterozygosity was observed in the first passage of the mouse tumor. Chromosome analysis in later passages revealed loss of one whole chromosome #13 as the single consistent karyotypic change.