Involvement of NF-κB/miR-448 regulatory feedback loop in chemotherapy-induced epithelial–mesenchymal transition of breast cancer cells

Abstract

The epithelial-mesenchymal transition (EMT) induced by chemotherapeutic agents promotes malignant tumor progression; however, the mechanism underlying the drug-induced EMT remains unclear. In this study, we reported that miR-448 is the most downregulated microRNA following chemotherapy. Suppression of miR-448 correlated with EMT induction in breast cancer in vitro and in vivo. With the use of chromatin immunoprecipitation-seq analysis, we demonstrated that miR-448 suppression induces EMT by directly targeting special AT-rich sequence-binding protein-1 (SATB1) mRNA, leading to elevated levels of amphiregulin and thereby, increasing epidermal growth factor receptor (EGFR)-mediated Twist1 expression, as well as nuclear factor jB (NF-jB) activation. On the other hand, we also found that the adriamycin-activated NF-jB directly binds the promoter of miR-448 suppressing its transcription, suggesting a positive feedback loop between NF-jB and miR-448. Furthermore, all patients who received cyclophosphamide (CP), epirubicin plus taxotere/CP, epirubicin plus 5-fluorouracil chemotherapy showed miR-448 suppression, an increased SATB1, Twist1 expression and acquisition of mesenchymal phenotypes. These findings reveal an underlying regulatory pathway, in which the autoregulation between NF-jB and miR-448 is important for restrain miR-448 suppression upon chemotherapy and may have a role in the regulation of chemotherapy-induced EMT. Disruption of the NF-jB-miR-448 feedback loop during clinical treatment may improve the chemotherapy response of human breast cancers in which EMT is a critical component. Chemotherapy is a systemic treatment that destroys reproducing cells, but it cannot differentiate between normal and cancerous cells. Side effects occur when normal cells become damaged. Apart from the side effects of cancer chemotherapy, unexpected 'opposite effects' of chemotherapy, which enhance the critical steps in malignancy rather than inhibiting them, 1-3 have attracted progressively more attention, suggesting that novel strategies should be developed to reverse these opposite effects and render chemotherapy more effective.Tumor cells progress from non-invasive to malignant phenotypes via a series of critical steps that involve morphological changes referred to as the epithelial-mesenchymal transition (EMT). 4 EMT is a process originally observed during the embryonic development, in which cells lose epithelial characteristics. [5][6][7][8][9][10] With respect to the chemotherapy, recent studies have demonstrated a close link between EMT and insensitivity to chemotherapeutic agents. Hiscox et al. 11 showed increased b-catenin expression and elevated levels of transcription of b-catenin target genes known to be involved in tumor progression and EMT in the tamoxifen (TAM)-resistant MCF7 cells. Kajiyama et al. 12 identified an association between chronic paclitaxel resistance and induction of EMT in epithelial ovarian carcinomas. In addition, we previously showed that transient adriamycin treatmentinduced EMT and apoptosi...

FOXP3 and FOXP3-regulated microRNAs suppress SATB1 in breast cancer cells

“…As FOXP3 loss appears to occur more frequently in primary breast cancer cells than does SATB1 induction (Zuo et al, 2007b;Han et al, 2008), other mechanisms that participate in the suppression of SATB1 such as miR-488 may also need to be lost for SATB1 induction to occur (Li et al, 2010a). Together, these findings indicate that SATB1 expression is tightly regulated in breast epithelia both through transcriptional control and post-transcriptionally through miRs.…”

miR-448 downregulates MPPED2 to promote cancer proliferation and inhibit apoptosis in oral squamous cell carcinoma

“…It is upregulated in breast cancer (24) and early cerebral aneurysm (12), and downregulated in hepatocellular carcinoma (25) . It has also been reported that miR-448 is the most downregulated microRNA following chemotherapy in breast cancer (13), suggesting that it may act as an oncogene or anti-oncogene in different cancers. The results of the present study suggest that the expression of miR-448 in OSCC tissues was significantly higher than that in matched paraneoplastic normal tissues.…”

“…miR-448 is reportedly associated with various human malignancies. It is upregulated in breast cancer and early cerebral aneurysm (12,13), indicating regulatory effects of miR-448 in various conditions.…”

MicroRNA-mediated breast cancer metastasis: from primary site to distant organs

“…Aberrant activation of NF-kB was frequently observed in cancers and was reported to be involved in metastasis (Karin, 2006;Van Waes, 2007;Sethi et al, 2008). It has been revealed that NF-kB can form a positive feedback loop with miR-448 through EMT to regulate metastasis in chemotherapy response (Li et al, 2011). Adriamycin-activated NF-kB directly binds the promoter of miR-448 to suppress its transcription.…”