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Investigations for Fine Mapping of Amplifications in Chromosome 3q26.3–28 Frequently Occurring in Squamous Cell Carcinomas of the Head and Neck

Objective: Overrepresentations of chromosomal material on the long arm of chromosome 3 frequently occur in squamous cell carcinoma of the head and neck. This experimental study was conducted for further fine mapping of these overrepresentations by interphase fluorescence in situ hybridization (FISH) of tumor cells in cell lines. Methods: Seven cell lines derived from squamous cell carcinomas of the head and neck were investigated by comparative genomic hybridization to analyze unbalanced chromosomal aberrations. Overrepresentations of chromosomal material on the telomeric part of the long arm of chromsome 3 were further analyzed by interphase FISH using YAC contig clones. Results: Chromosomal aberrations which frequently occurred were overrepresentations on 5p (n = 4), 7p (n = 5), 11q13 (n = 3), 15q (n = 5), 17q (n = 3), 19q (n = 2), 20q (n = 2) and 22q (n = 3). Reoccurring losses of chromosomal material were found in 3p (n = 3), 7q (n = 2), 18q (n = 3) and 19p (n = 2). Gains of chromosomal material on chromosome 3q were found in 4 out of 7 cell lines, with a high copy number of amplifications occurring in the chromosomal region of 3q26.3–28. Further experiments revealed a physical mapping of this amplification to a narrow band of 13.8 Mbp on chromosome 3q, whose amplification borders were represented by the YAC clones 754_f_3 centomeric and 955_b_2 telomeric. Conclusions: By FISH, the amplification of chromosomal material on 3q could be fine mapped on a narrow band on 3q26.3–27. This aberration can be considered as a breakpoint in tumorigenesis. Putative candidate oncogenes and tumor suppressor genes located in this region might be a target for mutations leading to tumor progression.