Yasai Yao

MiR‐200b expression in breast cancer: a prognostic marker and act on cell proliferation and apoptosis by targeting Sp1

MicroRNAs (miRNAs) have been identified as important post‐transcriptional regulators involved in various biological and pathological processes of cells. In the present study, we investigated the roles and mechanisms of miR‐200b in human breast cancer (BC). MiR‐200b expression was carried out by qRT‐PCR in human BC cell lines and clinical samples and the prognostic potential of miR‐200b expression was further evaluated. In vitro, effects of miR‐200b on BC cell proliferation, apoptosis and cell cycle distribution were tested by CCK‐8 kit, flow cytometric analysis respectively. Luciferase assay and Western blot analysis were performed to validate the potential targets of miR‐200b after the preliminary screening by employing open access software. We found that miR‐200b was significantly down‐regulated in both BC tissues and cell lines. The low expression of miR‐200b was correlated with late TNM stage, negative oestrogen receptor and positive HER‐2 status. Multivariate analysis showed that miR‐200b expression was an independent prognostic predictor for BC patients. Integrated analysis identified Sp1 as a direct and functional target of miR‐200b. Knockdown of Sp1 inhibited cell proliferation, induce apoptosis and act on cell cycle resembling that of miR‐200b high expression. Our data demonstrates that miR‐200b has potential to serve as prognostic biomarker and tumour suppressor for BC patients. As a direct and functional target of miR‐200b, Sp1 and miR‐200b both could be an exciting target for BC treatment strategy.

FOXM1 mediates resistance to docetaxel in gastric cancer via up‐regulating Stathmin

Docetaxel is commonly used as an effective chemotherapeutic drug for gastric cancer patients recently. With the increasing emergence of docetaxel resistance nowadays, identification of suitable biomarkers for predicting chemosensitivity to docetaxel may be a key role for improving therapeutic effects for gastric cancer patients. In this study, we investigated the correlation between the expression of transcription factor forkhead box protein M1 (FOXM1) and chemotherapy response to docetaxel in gastric cancer, the possible mechanism for which was further explored. As a result, FOXM1 overexpression was shown to mediate resistance to docetaxel in gastric cancers. It altered microtubule dynamics to protect tumour cells from docetaxel‐induced apoptosis. Mechanistic investigations revealed that tubulin‐destabilizing protein Stathmin, which mediated docetaxel resistance in FOXM1‐silenced gastric cancer cells, is a direct down‐stream target of FOXM1, whereas another microtubule dynamics protein mitotic centromere–associated kinesin (MCAK), shown to be related to docetaxel resistance in gastric cancer cells, is not associated with FOXM1 expression significantly. These results were further provided by immunohistochemical analysis, indicating that FOXM1 and Stathmin expression levels were correlated in 103 post‐operational gastric cancer specimens. Moreover, when we attenuated FOXM1 expression with FOXM1 inhibitor thiostrepton, docetaxel resistance in gastric cancers was found to be reversed, simultaneously with the down‐regulation of FOXM1 and Stathmin. Therefore, FOXM1 can be a useful marker for predicting and monitoring docetaxel response. Through the inhibition of FOXM1, docetaxel resistance can be reversed, and thus FOXM1 could be a new therapeutic target in docetaxel‐resistant gastric cancer.

miR-141 confers docetaxel chemoresistance of breast cancer cells via regulation of EIF4E expression

Resistance to docetaxel, a chemotherapy drug for breast cancer (BC) treatment, occurs in ~50% of patients, and the underlying molecular mechanisms of drug resistance are not fully understood. Gene regulation through miR-141 has been proven to play an important role in cancer drug resistance. The present study investigated the role of miR-141 expression in BC cells of acquired docetaxel resistance. Inhibition of miR-141 enhanced the response to docetaxel in docetaxel-resistant cells (MCF-7/DTX and MDA-MB-231/DTX, respectively), whereas overexpression of miR-141 confered resistance in docetaxel-sensitive cells (MCF-7 and MDA-MB-231, respectively). By directly targeting the eukaryotic translation initiation factor 4E (EIF4E) mRNA, miR-141 acts on genes that are necessary for drug induced apoptosis rendering the cells drug resistant. Modulation of miR-141 expression was correlated with EIF4E expression changes and a direct interaction of miR-141 with EIF4E was shown by a luciferase assay. Thus, the present study is the first to show an increased expression of miR-141 in an acquired model of docetaxel resistance in BC. This serves as a mechanism of acquired docetaxel resistance in BC cells, possibly through direct interactions with EIF4E, therefore presenting a potential therapeutic target for the treatment of docetaxel resistant BC.

Inhibition of ErbB‐2 induces TFF3 downregulation in breast cancer cell lines

ErbB‐2 gene plays an important role in carcinoma formation whose overexpression was observed in many types of tumors, including breast cancer. Dysregulation of Trefoil factor 3 (TFF3), which is thought to function in the development and progression of breast cancer, was found to be upregulated in ErbB2‐overexpressing breast cancers and cells. However, a putative interaction between ErbB‐2 and TFF3 in breast cancer remains unknown. To determine whether TFF3 has an important role in breast tumor, its levels were measured by immunohistochemistry in 130 cases of breast infiltrating duct carcinoma and 30 cases of normal breast tissue with a specific monoclonal antibody raised against human TFF3. Patients who were positive for ErbB‐2 also had high expression levels of TFF3 (p < 0.05). Also, after infecting the SK‐BR‐3 cells with lentivirus‐mediated ErbB2‐specific shRNA (Lenti‐ShERBB2), we detected the expressions of ErbB‐2 and TFF3 by real‐time polymerase chain reaction and Western blotting, respectively. Compared with the control groups, ErbB‐2 mRNA expression was decreased in the Lenti‐ShERBB2 infection group, and Western blotting indicated a concordant ErbB‐2 protein reduction. On the other hand, TFF3 expression at both mRNA and protein levels was significantly downregulated by ErbB‐2 silencing in SK‐BR‐3. These findings are a proof of the foundation for a certain relationships of ErbB‐2 and TFF3, which may serve as novel therapeutic markers of ErbB2‐overexpressing breast cancers in the future.