BioProject

Deciphering the molecular mechanisms involved in breast tumorigenesis has been the subject of extensive research in the last years; yet unpredictable response and development of resistance to adjuvant therapies remain major questions in the management of breast cancer patients. More...

Deciphering the molecular mechanisms involved in breast tumorigenesis has been the subject of extensive research in the last years; yet unpredictable response and development of resistance to adjuvant therapies remain major questions in the management of breast cancer patients. The power of miR expression signatures has emerged recently from several studies. Normal and breast tumor tissues can be discriminated by a miR signature as reported by Iorio et al (Iorio et al, 2005). Recent findings have also linked deregulated miR expression to breast cancer metastasis (Adorno et al, 2009; Huang et al, 2008; Tavazoie et al, 2008). Moreover, microRNAs are considering as a powerful tool in diagnosis and prognosis of breast cancer. In our study, we measured microRNA expression profiles from 64 primary breast cancer patients, comprising 56 matched tumor and adjacent peritumoral breast tissues, 5 tumor and 3 peritumor unmatched tissues. Our aim was to identify new microRNAs involved in the process of neoplastic transformation. The microarray data analysis identified, in every subgroup of breast cancers analyzed, a specific subset of microRNAs that were differentially expressed in tumor compared to peritumoral tissues. Among these miRs, we identified two (miR-10b* and miR-139-5p) that were down-regulated and three (miR-425, miR-454 and miR-301a) that were up-regulated for all three subtypes. We further show that microRNA-10b* is a master regulator of breast cancer cell proliferation. Two canonical CpG islands (5kb) upstream from the precursor sequence are hypermethylated in breast cancer tissues analyzed. Ectopic delivery of synthetic microRNA-10b* in breast cancer cell lines or into xenograft mouse breast tumors inhibits cell proliferation and impairs tumor growth in vivo, respectively. We identified and validated in vitro and in vivo three novel target mRNAs of miR-10b*, BUB1, PLK1 and CCNA2 genes, which play a remarkable role in cell cycle regulation and whose high expression in breast cancer patients reduced disease free survival, relapse free survival and metastasis free survival when compared to low expressors. This also suggests that restoration of microRNA-10b* expression might bear therapeutic promise. Overall design: In exploring the potential involvement of miRs in breast tumorigenesis, we profiled the miRs expression of 64 primary breast cancer patients, comprising 56 matched tumor and adjacent peritumoral breast tissues, 5 tumor and 3 peritumor unmatched tissues, using the Agilent microarray platform. For 14 samples technical replicate were also performed. Less...