Overexpression of annexin A2 (Anxa2) is correlated with invasion and metastasis in breast cancer cells. In this study, breast cancer patients with upregulated Anxa2 exhibited poor overall and disease-free survival rates. Anxa2 expression was also positively correlated with the expression of epidermal growth factor receptor (EGFR) and epithelial–mesenchymal transition (EMT) markers in breast cancer tissues and cell lines. Moreover, knockdown of Anxa2 impaired EGF-induced EMT, as well as the migration and invasion of breast cancer cells in vitro. Meanwhile, Anxa2 depletion significantly ablated pulmonary metastasis in a severe combined immunodeficiency mouse model of breast cancer. Importantly, Anxa2 reduction inhibited EGF-induced activation of STAT3, which is required for EGF-induced EMT. Anxa2 directly bound to STAT3 and enhanced its transcriptional activity, thereby indicating that Anxa2 promotes EGF-induced EMT in a STAT3-dependent manner. Our findings provide clinical evidence that Anxa2 is a poor prognostic factor for breast cancer and reveal a novel mechanism through which Anxa2 promotes breast cancer metastasis.

Multidrug resistance (MDR) is the major cause of failure in cancer chemotherapy. Recent reports even suggest that MDR is associated with elevated invasion and metastasis of tumor cells. In the current study, we used a proteomic approach to identify genes that play an important role in MDR induced cell migration. 2D-PAGE and MALDI-TOF/MS-based proteomics approach were used to separate and identify differentially expressed proteins between MCF-7 and MCF-7/ADR, a p-glycoprotein-overexpressing adriamycin-resistance breast cancer cell line. Annexin a2 (Anxa2) was identified as highly expressed in MCF-7/ADR cells, but not in MCF-7 cells. Small interference RNA-mediated gene suppression demonstrated that Anxa2 was required for enhanced cell proliferation and invasion of the MCF-7/ADR cells. Down-regulation of Anxa2 alone was not sufficient to revert the cell sensitivity to adriamycin, suggesting that Anxa2 was not required for MDR phenotype. Taken together, our results showed that expression of Anxa2 is enhanced when cancer cells, MCF-7, acquired drug resistance and it plays an essential role in MDR-induced tumor invasion.

BackgroundMicroRNAs (miRNAs) are small, non-coding RNAs capable of postranscriptionally regulating gene expression. Accurate expression profiling is crucial for understanding the biological roles of miRNAs, and exploring them as biomarkers of diseases.Methodology/Principal FindingsA novel, highly sensitive, and reliable miRNA quantification approach,termed S-Poly(T) miRNA assay, is designed. In this assay, miRNAs are subjected to polyadenylation and reverse transcription with a S-Poly(T) primer that contains a universal reverse primer, a universal Taqman probe, an oligo(dT)11 sequence and six miRNA-specific bases. Individual miRNAs are then amplified by a specific forward primer and a universal reverse primer, and the PCR products are detected by a universal Taqman probe. The S-Poly(T) assay showed a minimum of 4-fold increase in sensitivity as compared with the stem-loop or poly(A)-based methods. A remarkable specificity in discriminating among miRNAs with high sequence similarity was also obtained with this approach. Using this method, we profiled miRNAs in human pulmonary arterial smooth muscle cells (HPASMC) and identified 9 differentially expressed miRNAs associated with hypoxia treatment. Due to its outstanding sensitivity, the number of circulating miRNAs from normal human serum was significantly expanded from 368 to 518.Conclusions/SignificanceWith excellent sensitivity, specificity, and high-throughput, the S-Poly(T) method provides a powerful tool for miRNAs quantification and identification of tissue- or disease-specific miRNA biomarkers.

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