Transcription profiling of human breast cancer cell lines and tissue samples to identify aberrant microRNA expression

MicroRNAs are a class of small non-coding RNAs that control gene expression by targeting messenger RNAs and triggering either translation repression or RNA degradation. Their aberrant expression may be involved in human diseases, including cancer. Indeed, microRNA aberrant expression has been previously found in human chronic lymphocytic leukemias, where microRNA signatures were associated with specific clinico-biological features. Here, we show that, in comparison to normal breast tissue, microRNAs are also aberrantly expressed in human breast cancer. The overall microRNA expression could clearly separate normal versus cancer tissues, with the most significantly deregulated microRNAs being mir-125b, mir-145, mir-21, mir-155. Results were confirmed by microarray and Northern blot analyses. We could identify microRNAs whose expression was correlated with specific breast cancer bio-pathologic features, such as estrogen and progesterone receptor expression, tumor stage, vascular invasion or proliferation index.