Cytogenetic analyses of peripheral blood cells of breast cancer patients unveiled in one case a grossly enlarged G-band in one copy of chromosome 16 (16qh+), which scored also strongly positive in C-banding. Fluorescence in situ hybridization with both a total chromosome 16 library and with probe pHuR195 detecting locus D16Z3 further documented the increase of the copy number of the corresponding satellite DNA at 16q-11.2. Slot-blot analyses with pHuR195 revealed an approximately 10-fold amplification compared to a random selection of normal chromosomes 16. The chromosome 16 carrying amplified DNA is passed on to one of 3 children, who shows no obvious anomaly. Previous studies (Kokalj-Vokac N, Alemeida A, Gerbault-Seureau M, Malfoy B, Dutrillaux B: Gene Chromosome Cancer 7: 8-14, 1993) had revealed that satellite DNA in chromosome 16 often participates in interchromosomal recombinations, preferentially with chromosome 1, in breast cancer cells. Although the increased copy number of satellite DNA could represent a polymorphism, it might provide an enlarged target for recombination events and therefore could be a determinant for cancer predisposition.

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