406985

MIR200C

microRNA 200c;MIR200C;microRNA 200c

hsa-mir-200c

12p13.31

ncRNA

Resistance to trastuzumab and concomitantly distal metastasis are leading causes of mortality in HER2-positive breast cancers, the molecular basis of which remains largely unknown. Here, we generated trastuzumab-resistant breast cancer cells with increased tumorigenicity and invasiveness compared with parental cells, and observed robust epithelial-mesenchymal transition (EMT) and consistently elevated TGF-beta signaling in these cells. MiR-200c, which was the most significantly downregulated miRNA in trastuzumab-resistant cells, restored trastuzumab sensitivity and suppressed invasion of breast cancer cells by concurrently targeting ZNF217, a transcriptional activator of TGF-beta, and ZEB1, a known mediator of TGF-beta signaling. Given the reported backward inhibition of miR-200c by ZEB1, ZNF217 also exerts a feedback suppression of miR-200c via TGF-beta/ZEB1 signaling. Restoration of miR-200c, silencing of ZEB1 or ZNF217 or blockade of TGF-beta signaling increased trastuzumab sensitivity and suppressed invasiveness of breast cancer cells. Therefore, our study unraveled nested regulatory circuits of miR-200c/ZEB1 and miR-200c/ZNF217/TGF-beta/ZEB1 in synergistically promoting trastuzumab resistance and metastasis of breast cancer cells. These findings provide novel insights into the common role of EMT and related molecular machinery in mediating the malignant phenotypes of breast cancers.

OBJECTIVE: To evaluate the ability of epithelial-to-mesenchymal transition-related microRNAs (miRNAs) as serum biomarkers for prognosis and prediction of metastasis in patients with colorectal cancer (CRC). BACKGROUND: Epithelial-to-mesenchymal transition-related miRNAs drive CRC progression and metastasis. However, their potential as serum biomarkers in CRC has not been studied. METHODS: This was a 3-phase study using 446 colorectal specimens. In the first phase, we selected candidate miRNAs associated with metastasis by analyzing the expression of 4 miR-200 family members (miR-200b, -200c, -141, and -429) in serum samples from 12 patients with stage I and IV CRC. The second phase involved independent validation of candidate miRNAs in serum from 182 patients with CRC and 24 controls. Finally, we analyzed expression in matched 156 tumor tissues from 182 patients with CRC and an independent set of 20 matched primary CRC and corresponding liver metastases to identify the source of circulating miRNAs. RESULTS: After initial screening, miR-200c was selected as the candidate serum miRNA best associated with metastasis. Validation analysis revealed that serum miR-200c levels were significantly higher in stage IV than in stage I-III CRCs. High serum miR-200c demonstrated a significant positive correlation with lymph node metastasis, distant metastasis, and prognosis (P = 0.0026, P = 0.0023, and P = 0.0064, respectively). More importantly, serum miR-200c was an independent predictor for lymph node metastasis (odds ratio: 4.81, 95% confidence interval: 1.98-11.7, P = 0.0005) and tumor recurrence (hazard ratio: 4.51, 95% confidence interval: 1.56-13.01, P = 0.005) and emerged as an independent prognostic marker for CRC (hazard ratio: 2.67, 95% confidence interval: 1.28-5.67, P = 0.01). CONCLUSIONS: Serum miR-200c has strong potential to serve as a noninvasive biomarker for CRC prognosis and predicting metastasis.

The expression of miR-200c has been widely reported to be elevated in tumor tissues and sera of patients with colorectal cancer (CRC) and has been found to correlate with poor prognosis. However, how miR-200c regulates the apoptosis, survival, invasion, metastasis, and tumor growth in colon cancer cells remains to be fully elucidated. This study seeks to further investigate the role of miR-200c in colon cancer development. The expression of miR-200c in tumor and peritumoral tissues of 101 colon cancer patients was measured by real-time PCR. miR-200c expression in HCT-116 and HT-29 colon cancer cells was silenced by adenovirus-carried expression of antisense mRNA against miR-200c. The protein levels of PTEN, p53 Ser(15), PP1, and activated caspase-3 in HCT-116 and HT-29 cells were measured by Western blot. This study demonstrated that the expression of miR-200c was significantly higher in tumor tissues than in peritumoral tissues of colon cancer patients. The elevated miR-200c expression significantly correlated with the TNM stage, lymph node metastasis, and invasion of colon cancer. Silencing miR-200c expression significantly induced cell apoptosis, inhibited long-term survival, invasion, and metastasis, and delayed xenograft tumor growth. Importantly, silencing miR-200c expression sensitized the therapeutic effect of Ara-C (Cytarabine). The effects of silencing miR-200c expression were associated with upregulation of PTEN protein and p53 Ser(15) phosphorylation levels in HCT-116 cells and PTEN protein expression in HT-29 cells. In conclusion, miR-200c functions as an oncogene in colon cancer cells through regulating tumor cell apoptosis, survival, invasion, and metastasis as well as xenograft tumor growth through inhibition of PTEN expression and p53 phosphorylation.

Recently, a group of microRNAs (miRNAs), the miR-200 family (miR-200s) has been found to be deregulated in multiple types of cancers, in which this family of miRNAs was demonstrated to play a pivotal role in tumor initiation, maintenance, malignant metastasis and chemotherapy resistance. By targeting several central inducers of the epithelial-to-mesenchymal transition (EMT), e.g. ZEB1, ZEB2 and SLUG, miR-200s are currently recognized as master regulators of EMT, thereby suppressing cancer invasion and metastasis. The involvement of miR-200s in angiogenesis has also been reported, and they were found to directly target VEGF-A, FLT1/VEGFR1 and KDR/VEGFR2, three key components of the VEGF signaling pathway. Importantly, miR-200s also modulate the self-renewal ability of cancer stem cells by targeting BMI1 and SUZ12. Aberrant expression of miR-200s has been shown to confer chemoresistant properties to various kinds of cancers. Thus, miR-200s, by playing critical and pleiotropic roles in malignancies, are promising targets for cancer therapy. Notably, it has been shown that several types of natural agents and herbal extracts could be employed to manipulate the expression of miR-200s, making the targeting of miR-200s in cancer therapy more clinically attractive. Nevertheless, a very recent study reported a metastasis-promoting role of miR-200s in breast cancer; thus, careful assessment should be conducted before applying therapeutic interventions using miR-200s as treatment targets. In this review, we will focus on our emerging understanding of the roles of miR- 200s in cancer, specifically their therapeutic potential in treating cancer.

MUC1 is a transmembrane glycoprotein that modulates transcription via its cytoplasmic domain. We evaluated the capacity of MUC1 to regulate the global transcription of microRNAs in pancreatic cancer cells expressing MUC1. Results indicated that MUC1 regulated expression of at least 103 microRNAs. We evaluated further regulation of the microRNA transcript cluster miR-200c/141, which was among the most highly regulated microRNAs. We found that MUC1 directly interacted with ZEB1, a known transcriptional repressor of the miR-200c/141 cluster, at the promoter of miR-200c/141, and further reduced transcript production. These data indicate that signaling through MUC1 influences cancer progression by regulating transcription of microRNAs that are associated with the process of metastasis.

MUC1 is a transmembrane glycoprotein that modulates transcription via its cytoplasmic domain. We evaluated the capacity of MUC1 to regulate the global transcription of microRNAs in pancreatic cancer cells expressing MUC1. Results indicated that MUC1 regulated expression of at least 103 microRNAs. We evaluated further regulation of the microRNA transcript cluster miR-200c/141, which was among the most highly regulated microRNAs. We found that MUC1 directly interacted with ZEB1, a known transcriptional repressor of the miR-200c/141 cluster, at the promoter of miR-200c/141, and further reduced transcript production. These data indicate that signaling through MUC1 influences cancer progression by regulating transcription of microRNAs that are associated with the process of metastasis.

Notch signalling is crucial for the correct development and growth of numerous organs and tissues, and when subverted it can cause cancer. Loss of miR-8/200 microRNAs (miRNAs) is commonly observed in advanced tumours and correlates with their invasion and acquisition of stem-like properties. Here, we show that this miRNA family controls Notch signalling activation in Drosophila and human cells. In an overexpression screen, we identified the Drosophila miR-8 as a potent inhibitor of Notch-induced overgrowth and tumour metastasis. Gain and loss of mir-8 provoked developmental defects reminiscent of impaired Notch signalling and we demonstrated that miR-8 directly inhibits Notch ligand Serrate. Likewise, miR-200c and miR-141 directly inhibited JAGGED1, impeding proliferation of human metastatic prostate cancer cells. It has been suggested that JAGGED1 may also be important for metastases. Although in metastatic cancer cells, JAGGED1 modestly regulated ZEB1, the miR-200c's target in invasion, studies in Drosophila revealed that only concurrent overexpression of Notch and Zfh1/ZEB1 induced tumour metastases. Together, these data define a new way to attenuate or boost Notch signalling that may have clinical interest.