Fine Mapping the Chromosome 17q23 Amplicon in MCF7 cells

• Main Authors: Mei-Xsuan Huang, 黃玫璇
• Other Authors: Ming-Ta Hsu
• Format: Others
• Language: en_US
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/71059328252164084707

碩士 === 國立陽明大學 === 生化暨分子生物研究所 === 94 === Breast cancer is one of the most common malignant diseases and a major cause of cancer-related deaths among women in Taiwan. Several chromosomal sites in breast cancer cells frequently undergo amplification, implicating genes in these chromosomal loci for tumor development and progression. Among these chromosomal aberrations, 17q23 is a common region of amplification in breast cancers with poor prognosis. Here we combined the methodology based on PCR, oligo-based CGH and Affymetrix 100K mapping to fine map the 17q23 amplicon in MCF7 breast cancer cells. Amplicon mapping in MCF7 cells identified three separate highly amplified regions flanked by two regions of low-level amplification. By the help of rapid amplification of cDNA ends near the amplification boundary, we cloned a novel fused cDNA from two of the most common amplification regions, 17q23 and 3p14, in MCF7 cells. The fused transcript is derived from the first six exons of BCAS3 gene in 17q23 joined to a novel gene in 3p14.2 near the evolutionary breakpoint between chimp and human genomes. Cytogenetic analysis of dual-color metaphase FISH was performed and showed a colocalization pattern of the BAC probe, RP11-67D12 from 17q23.2 and RP11-126M18 from 3p14.2, confirming the presence of the t(17;3)(q23.2;p14.2) in MCF7, but not MCF-10F. Since this fused cDNA isn’t unique to the immortalized or cancer cell lines we tested, but is universally expressed in adult normal tissues, except blood tissues, we surmised that the novel fused cDNA may be derived from pre-mRNA level trans-splicing. In summary, we discovered a novel t(17;3)(q23.2;p14.2) chromosomal translocation in MCF7 cells and that the fused transcript was also found in normal human tissues except leukocytes. Another fused transcript derived from BCAS3 and BCAS4 in t(17;20) translocation was also found present in normal human tissues. These results suggest prevalent RNA trans-splicing in human cells.