Genomic instability is commonly seen in breast cancers. To date, various
chromosomal or segmental loss or amplification regions have been detected in
primary tumors and cell lines. Hence, an intensive search for potent tumor
suppressors or oncogenes located in these regions continues.
MicroRNAs (miRNAs) are ~18-24 nt long non-coding RNAs that regulate
protein expression either by target mRNA cleavage or translational repression.
We hypothesized that miRNAs located in genomic instability regions in breast
cancer cells may contribute to the initiation or maintenance of breast tumors.
Here, we investigated genomic levels of miRNAs on frequent loss or gain regions
of breast cancer cells. First, using bioinformatics resources we mapped known
miRNAs and candidate miRNAs to reported genomic instability regions. Our
extensive searches resulted with more than 30 known miRNAs and 35 candidate miRNAs. To further confirm loss or amplification of miRNA genes on these
chromosomal regions in breast cancer cells, we designed specific primers for the
known pre-miRNA DNA regions and performed semi-quantitative PCR in 20
breast cancer cell lines, 2 immortalized mammary cell lines, and 2 control
samples. Densitometry results suggested that a striking 61 % (22/36) of selected
miRNAs showed either loss or amplification in at least 3 different breast cancer
cell lines. Interestingly most of these alterations were found to be amplifications
even in regions reported to harbor losses in breast tumors. Genomic fold change
results of these microRNAs provide a biologically relevant starting point for
further expression and functional experiments of microRNAs in breast cancer
studies. Genomic fold change analysis followed expression analysis of two
significant microRNAs (hsa-miR-21 and hsa-miR-383) was done by qRT-PCR
method.
Our data provide a wide screen of genomic instability of 36 microRNA
genes in 20 breast cancer cells and normal samples detected by semi-quantitative
duplex PCR method as well as expression analysis of two microRNAs. To this
date, such an extensive data on genomic status of microRNA genes in breast
cancer cells did not exist. Therefore, our results are the first comprehensive
investigation of many microRNA genes on genomic instability regions in breast
cancers and provide further clues to the potential involvement of these
microRNAs in breast tumorigenesis MicroRNA genomic instability may affect
their expression and therefore their targets&rsquo / expressions. Understanding how these
microRNAs regulate their targets and contribute to the neoplastic events will also
contribute to the field by using this information for future diagnostic and
threaupetical applications.
| Identifer | oai:union.ndltd.org:METU/oai:etd.lib.metu.edu.tr:http://etd.lib.metu.edu.tr/upload/3/12609007/index.pdf |
| Date | 01 December 2007 |
| Creators | Selcuklu, Sadan Duygu |
| Contributors | Erson, Ayse Elif |
| Publisher | METU |
| Source Sets | Middle East Technical Univ. |
| Language | English |
| Detected Language | English |
| Type | M.S. Thesis |
| Format | text/pdf |
| Rights | To liberate the content for public access |
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