Discovery of Genomic Breakpoints Affecting Breast Cancer Progression and Prognosis
Annual summary rept. 15 Sep 2008-14 Sep 2009
BAYLOR COLL OF MEDICINE HOUSTON TX
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157 genomic breakpoints could be confirmed as likely somatic mutations. We focused on breakpoints predicted to lead to fusion transcripts. By RT-PCR we determined that four showed a fusion mRNA. In the case of the ARFGEF2SULF2 fusion, a non-functional Sulfatase 2 might be created. To give insight into the function, SULF2 mRNA was knocked down using siRNA. Cells treated with SULF2 siRNA, exhibited a growth advantage compared to control siRNA. Also, cells treated with SULF2 siRNA showed enhanced survival, and an advantage in anchorage-independent growth. This shows that knocking-down SULF2 enhances tumorigenic properties, and that the presence of this fusion might mean a loss of function of the tumor suppressor Sulfatase 2 and enhance the tumorigenicity. Another fusion, RAD51CATXN7 results in the truncation RAD51C, a protein involved in double stranded break repair. We were able to confirm chimeric mRNA expression in 3 breast cancer cell lines. We were also able to detect a shorter form of RAD51C by western blot, indicating that the fusion introduces a truncation in RAD51C protein. To gain insight into the heterogeneity of genomic breakpoints, and narrow down on breakpoints originating from the ancestor, we studied these 157 validated breakpoints in seven MCF-7 sub-lines. There is an enrichment for breakpoints containing genes 50.3 vs 77.4, and for fusion-containing breakpoints 6.4 vs 16.1. Also, all chimeric mRNA products are present in all MCF-7 sub-lines, indicating these breakpoints might originate from the ancestor.
- Genetic Engineering and Molecular Biology
- Medicine and Medical Research