Deregulated microRNAs in gastric cancer tissue-derived mesenchymal stem cells: novel biomarkers and a mechanism for gastric cancer

Background:

MicroRNAs (miRNAs) are involved in gastric cancer development and progression. However, the expression and role of miRNAs in gastric cancer stromal cells are still unclear.

Methods:

The miRNAs differentially expressed in gastric cancer tissue-derived mesenchymal stem cells (GC-MSCs) relative to adjacent non-cancerous tissue-derived MSCs (GCN-MSCs) and in cancer tissues relative to adjacent non-cancerous tissues were screened using miRNA microarray and validated by quantitative RT–PCR. The impact of GC-MSCs on HGC-27 cells was observed in vitro using colony formation and transwell assays, and these cells were subcutaneously co-injected into mice to assess tumour growth in vivo. Exogenous downregulation of miR-221 expression in cells was achieved using an miRNA inhibitor.

Results:

miR-214, miR-221 and miR-222 were found to be commonly upregulated in GC-MSCs and cancer tissues. Their levels were tightly associated with lymph node metastasis, venous invasion and the TNM stage. Gastric cancer tissue-derived mesenchymal stem cells significantly promoted HGC-27 growth and migration and increased the expression of miR-221 via paracrine secretion, and the targeted inhibition of miR-221 in GC-MSCs could block its tumour-supporting role. GC-MSC-derived exosomes were found to deliver miR-221 to HGC-27 cells and promoted their proliferation and migration.

Conclusions:

Gastric cancer tissue-derived mesenchymal stem cells favour gastric cancer progression by transferring exosomal miRNAs to gastric cancer cells, thus providing a novel mechanism for the role of GC-MSCs and new biomarkers for gastric cancer.     

Genistein downregulates onco-miR-1260b and inhibits Wnt-signalling in renal cancer cells

Background:

Wnt-signalling has an important role in renal cancer and it is modulated by genistein in other cancers. Recently, microRNAs (miRNAs) have emerged as new regulators of gene expression. Thus, we focused on miRNAs to examine the regulatory mechanism of genistein on the Wnt-signalling pathway in renal cell carcinoma (RCC).

Methods:

Initially, we investigated the effect of genistein on Wnt-signalling (TOPflash reporter assay (TCF reporter assays)) in renal cancer cells, and using microarray identified candidate miRNAs whose expression was decreased by genistein. We performed functional analyses and investigated the relationship between miRNA expression and renal cancer patient outcomes. We also did 3′UTR luciferase assays to look at direct miRNA regulation of Wnt-signalling-related genes.

Results:

Genistein promoted apoptosis while inhibiting RCC cell proliferation and invasion. Genistein also decreased TCF reporter activity in RCC cells. We found that miR-1260b was highly expressed and significantly downregulated by genistein in RCC cells. The expression of miR-1260b was significantly higher in renal cancer tissues compared with normal, and significantly related to overall shorter survival. In addition, miR-1260b promoted renal cancer cell proliferation and invasion in RCC cells. The 3′UTR luciferase activity of target genes (sFRP1, Dkk2, Smad4) was significantly decreased and their protein expression significantly upregulated in miR-1260b inhibitor-transfected renal cancer cells.

Conclusion:

Our data suggest that genistein inhibited Wnt-signalling by regulating miR-1260b expression in renal cancer cells.     

MiR-221/-222 differentiate prognostic groups in advanced breast cancers and influence cell invasion

Background:

MiR-221/-222 are frequently overexpressed in breast cancer and are associated with increased malignancy. The specific modification of microRNAs (miRNAs) expression could be a promising strategy in breast cancer therapy, leading to the suppression of tumourigenic processes in tumour cells.

Methods:

MiR-221/-222 expressions were analysed in 86 breast cancer tissues by quantitative RT–PCR and tested for correlation with immunohistochemistry data and clinical follow-up. In vitro assays were conducted using human breast cancer cell lines with lentiviral overexpression of miR-221/-222.

Results:

In tumour tissues, miR-221/-222 were associated with the occurrence of distant metastases. In particular, high levels of miR-221 were revealed to have a high prognostic impact for the identification of significantly different groups with advanced tumours. MiR-221/-222 overexpression strongly increased cell proliferation and invasion in vitro. Following miR-221/-222 overexpression an increased uPAR expression and cell invasion were observed.

Conclusion:

This study demonstrates a significant role for highly expressed miR-221/-222 in advanced breast cancers allowing for the identification of significantly different prognostic groups, particularly for HER2-positive and lymph-node-positive breast cancers. Considering that miR-221/-222 are strongly involved in cell invasion, these miRNAs may be promising markers for breast cancer prognosis and therapy.     

MicroRNA-143 targets DNA methyltransferases 3A in colorectal cancer

Background:

MicroRNAs (miRNAs) are 19-25-nucleotides regulatory non-protein-coding RNA molecules that regulate the expressions of a wide variety of genes, including some involved in cancer development. In this study, we investigated the possible role of miR-143 in colorectal cancer (CRC).

Methods:

Expression levels of human mature miRNAs were examined using real-time PCR-based expression arrays on paired colorectal carcinomas and adjacent non-cancerous colonic tissues. The downregulation of miR-143 was further evaluated in colon cancer cell lines and in paired CRC and adjacent non-cancerous colonic tissues by qRT–PCR. Potential targets of miR-143 were defined. The functional effect of miR-143 and its targets was investigated in human colon cancer cell lines to confirm miRNA–target association.

Results:

Both real-time PCR-based expression arrays and qRT–PCR showed that miR-143 was frequently downregulated in 87.5% (35 of 40) of colorectal carcinoma tissues compared with their adjacent non-cancerous colonic tissues. Using in silico predictions, DNA methyltranferase 3A (DNMT3A) was defined as a potential target of miR-143. Restoration of the miR-143 expression in colon cell lines decreased tumour cell growth and soft-agar colony formation, and downregulated the DNMT3A expression in both mRNA and protein levels. DNMT3A was shown to be a direct target of miR-143 by luciferase reporter assay. Furthermore, the miR-143 expression was observed to be inversely correlated with DNMT3A mRNA and protein expression in CRC tissues.

Conclusion:

Our findings suggest that miR-143 regulates DNMT3A in CRC. These findings elucidated a tumour-suppressive role of miR-143 in the epigenetic aberration of CRC, providing a potential development of miRNA-based targeted approaches for CRC therapy.     

Tumour suppressive microRNA-874 regulates novel cancer networks in maxillary sinus squamous cell carcinoma

Background:

On the basis of the microRNA (miRNA) expression signature of maxillary sinus squamous cell carcinoma (MSSCC), we found that miR-874 was significantly reduced in cancer cells. We focused on the functional significance of miR-874 in cancer cells and identification of miR-874-regulated novel cancer networks in MSSCC.

Methods:

We used PCR-based methods to investigate the downregulated miRNAs in clinical specimens of MSSCC. Our signature analyses identified 23 miRNAs that were significantly reduced in cancer cells, such as miR-874, miR-133a, miR-375, miR-204, and miR-1. We focused on miR-874 as the most downregulated novel miRNA in our analysis.

Results:

We found potential tumour suppressive functions such as inhibition of cancer cell proliferation and invasion. A molecular target search of miR-874 revealed that PPP1CA was directly regulated by miR-874. Overexpression of PPP1CA was observed in MSSCC clinical specimens. Silencing of the PPP1CA gene significantly inhibited cancer cell proliferation and invasion.

Conclusion:

The downregulation of miR-874 was a frequent event in MSSCC, which suggests that miR-874 functions as a tumour suppressive miRNA, directly regulating PPP1CA that has a potential role of an oncogene. The identification of novel miR-874-regulated cancer pathways could provide new insights into potential molecular mechanisms of MSSCC oncogenesis.     

Novel diagnostic value of circulating miR-18a in plasma of patients with pancreatic cancer

Background:

Several recent studies have demonstrated that microRNAs (miRNAs) are stably detectable in the plasma/serum. We hypothesised that miR-18a in the plasma is a potential biomarker in patients with pancreatic cancer.

Methods:

miR-18a is located in the miR-17–92 cluster and reported to be highly expressed in pancreatic cancer tissues. This study was divided into three parts: (1) Confirmation of higher miR-18a levels in primary pancreatic cancer tissues and cell lines than in normal pancreatic tissues and a human fibroblast cell line. (2) Evaluation of the plasma miR-18a assay using quantitative RT–PCR by comparing plasma results obtained from 36 patients with pancreatic cancer and from 30 healthy volunteers. (3) Evaluation of the assay for monitoring tumour dynamics in patients with pancreatic cancer.

Results:

(1) The expression of miR-18a was significantly higher in pancreatic cancer tissues (P=0.012) and pancreatic cancer cell lines (P=0.015) than in normal tissues and fibroblasts. (2) Plasma concentrations of miR-18a were significantly higher in pancreatic cancer patients than in controls (P<0.0001). The value of the area under the receiver-operating characteristic curve (AUC) was 0.9369. (3) Plasma levels of miR-18a were significantly lower in postoperative samples than in preoperative samples (P=0.0077).

Conclusion:

Circulating miR-18a might provide new complementary tumour markers for pancreatic cancer.     

The functional significance of microRNA-145 in prostate cancer

Background:

MicroRNAs (miRNAs) are small noncoding RNAs that have important roles in numerous cellular processes. Recent studies have shown aberrant expression of miRNAs in prostate cancer tissues and cell lines. On the basis of miRNA microarray data, we found that miR-145 is significantly downregulated in prostate cancer.

Methods and results:

We investigated the expression and functional significance of miR-145 in prostate cancer. The expression of miR-145 was low in all the prostate cell lines tested (PC3, LNCaP and DU145) compared with the normal cell line, PWR-1E, and in cancerous regions of human prostate tissue when compared with the matched adjacent normal. Overexpression of miR-145 in PC3-transfected cells resulted in increased apoptosis and an increase in cells in the G2/M phase, as detected by flow cytometry. Investigation of the mechanisms of inactivation of miR-145 through epigenetic pathways revealed significant DNA methylation of the miR-145 promoter region in prostate cancer cell lines. Microarray analyses of miR-145-overexpressing PC3 cells showed upregulation of the pro-apoptotic gene TNFSF10, which was confirmed by real-time PCR and western analysis.

Conclusion:

One of the genes significantly upregulated by miR-145 overexpression is the proapoptotic gene TNFSF10. Therefore, modulation of miR-145 may be an important therapeutic approach for the management of prostate cancer.     

Differential expression of microRNAs during melanoma progression: miR-200c, miR-205 and miR-211 are downregulated in melanoma and act as tumour suppressors

Background:

The incidence of malignant melanoma is increasing faster than that for any other cancer. Histological examination of skin excision biopsies remains the standard method for melanoma diagnosis and prognosis. Significant morphological overlap between benign and malignant lesions complicates diagnosis, and tumour thickness is not always an accurate predictor of prognosis.

Methods:

To identify improved molecular markers to support histological examination, we used microarray analysis of formalin-fixed and paraffin-embedded samples from different stages of melanomagenesis to identify differentially expressed microRNAs (miRNAs). Differential expression was validated by qRT–PCR, and functional studies were carried out after transfection of miRNA precursors or inhibitors into melanoma cells to modulate miRNA expression.

Results:

In all, 20 miRNAs showed highly significant differential expression between benign naevi and either primary or metastatic melanomas, the majority being downregulated in melanoma, whereas only 2 miRNAs, namely miR-203 and miR-205, were differentially expressed between primary and metastatic melanomas. In functional in vitro assays, overexpression of miR-200c and miR-205 inhibited anchorage-independent colony formation and overexpression of miR-211 inhibited both anchorage-independent colony formation and invasion.

Conclusion:

We have identified a series of differentially expressed miRNAs that could be useful as diagnostic or prognostic markers for melanoma and have shown that three miRNAs (namely miR-200c, miR-205 and miR-211) act as tumour suppressors.     

Circulating miR-378 in plasma: a reliable,haemolysis-independent biomarker for colorectal cancer

Background:

Plasma circulating tumour-specific microRNAs (miRNAs) are promising biomarkers of tumour presence and recurrence, especially for diseases whose best chance of successful treatment requires early diagnosis and timely surgery of an already malignant but not yet invasive tumour, such as colorectal cancer (CRC).

Methods:

Expression levels of miRNAs previously found to be differently expressed in tumour vs normal colon tissues were investigated by quantitative real-time PCR in plasma from CRC patients and from healthy donors and confirmed in independent case control series. The validated miRNAs were also measured after surgery. Analyses were repeated on the subsets of haemolysis-free samples.

Results:

We identified four miRNAs differently expressed between the compared groups, two (miR-21 and miR-378) of which were validated. miR-378 expression decreased in non-relapsed patients 4–6 months after surgery and miR-378 ability to discriminate CRC patients from healthy individuals was not influenced by haemolysis levels of plasma samples.

Conclusion:

The miRNA analysis on plasma samples represents a useful non-invasive tool to assess CRC presence as well as tumour-free status at follow-up. Plasma levels of miR-378 could be used to discriminate CRC patients from healthy individuals, irrespective of the level of haemoglobin of plasma samples.     

MicroRNA-196a promotes cervical cancer proliferation through the regulation of FOXO1 and p27Kip1

Background:

The phosphoinositide 3-kinase (PI3K)/Akt signalling pathway appears to be a key regulator in cervical carcinogenesis. However, the downstream regulatory mechanism of PI3K/Akt signalling remains largely unknown.

Methods:

The expression of miR-196a in cervical cancer cell lines and cervical cancer tissues was examined using real-time PCR. The effects of miR-196a on PI3K/Akt signalling and cellular proliferation were evaluated by bromodeoxyuridine labelling, 3-(4,5-Dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazoliumbromide, colony formation assays and luciferase assays.

Results:

The expression level of miR-196a was markedly increased in cervical cancer tissues and cell lines compared with normal cervical tissue and normal cervical squamous cells. Upregulation of miR-196a was correlated with advanced tumour stage and poor overall and recurrence-free survival in cervical cancer patients. Upregulation of miR-196a enhanced G1/S-phase transition and the proliferative ability of cervical cancer cells, whereas suppression of miR-196a had the opposite effect. Using bioinformatics and biological approaches, we showed that FOXO1 and p27^Kip1, two key effectors of PI3K/Akt signalling, were direct targets of miR-196a.

Conclusions:

Our findings suggest that miR-196a has an important role in promoting human cervical cancer cell proliferation and may represent a novel therapeutic target of microRNA-mediated suppression of cell proliferation in cervical cancer.     

Circulating microRNAs in plasma of patients with oesophageal squamous cell carcinoma

Background:

Several recent studies demonstrated that microRNAs (miRNAs) are stably detectable in plasma/serum. We hypothesised that plasma miRNAs concentrations contributed to potential biomarkers in patients with oesophageal squamous cell carcinoma (ESCC).

Methods:

We selected three oncogenic miRNAs (miR-21, miR-184, miR-221) and one tumour suppressive miRNA (miR-375), which are frequently reported in squamous cell carcinoma, as candidate targets for this plasma miRNA assay. This study was divided into three steps: (1) Determination of appropriate plasma miRNAs in preliminary tests. (2) Evaluation of whether the plasma miRNA assays could monitor tumour dynamics. (3) Validation study on the clinical application of plasma miRNA assays in 50 ESCC patients and 20 healthy volunteers.

Results:

(1) In preliminary tests, the plasma level of miR-21 was significantly higher (P=0.0218) and that of miR-375 (P=0.0052) was significantly lower in ESCC patients than controls. (2) The high plasma miR-21 levels reflected tumour levels in all cases (100%). The plasma level of miR-21 was significantly reduced in postoperative samples (P=0.0058). (3) On validation analysis, the plasma level of miR-21 tended to be higher in ESCC patients (P=0.0649), while that of miR-375 was significantly lower (P<0.0001) and the miR-21/miR-375 ratio was significantly higher (P<0.0001) in ESCC patients than in controls. The value of the area under the receiver-operating characteristic curve (AUC) was 0.816 for the miR-21/miR-375 ratio assay. Patients with a high plasma level of miR-21 tended to have greater vascular invasion (P=0.1554) and to show a high correlation with recurrence (P=0.0164).

Conclusion:

Detection of circulating miRNAs might provide new complementary tumour markers for ESCC.     

MicroRNA-1246 expression associated with CCNG2-mediated chemoresistance and stemness in pancreatic cancer

Background:

Pancreatic cancer has a poor prognosis because of its high refractoriness to chemotherapy and tumour recurrence, and these properties have been attributed to cancer stem cells (CSCs). MicroRNA (miRNA) regulates various molecular mechanisms of cancer progression associated with CSCs. This study aimed to identify the candidate miRNA and to characterise the clinical significance.

Methods:

We established gemcitabine-resistant Panc1 cells, and induced CSC-like properties through sphere formation. Candidate miRNAs were selected through microarray analysis. The overexpression and knockdown experiments were performed by evaluating the in vitro cell growth and in vivo tumourigenicity. The expression was studied in 24 pancreatic cancer samples after laser captured microdissection and by immunohistochemical staining.

Results:

The in vitro drug sensitivity of pancreatic cancer cells was altered according to the miR-1246 expression via CCNG2. In vivo, we found that miR-1246 could increase tumour-initiating potential and induced drug resistance. A high expression level of miR-1246 was correlated with a worse prognosis and CCNG2 expression was significantly lower in those patients.

Conclusions:

miR-1246 expression was associated with chemoresistance and CSC-like properties via CCNG2, and could predict worse prognosis in pancreatic cancer patients.     

MicroRNA expression signature of castration-resistant prostate cancer: the microRNA-221/222 cluster functions as a tumour suppressor and disease progression marker

Background:

Our present study of the microRNA (miRNA) expression signature in castration-resistant prostate cancer (CRPC) revealed that the clustered miRNAs microRNA-221 (miR-221) and microRNA-222 (miR-222) are significantly downregulated in cancer tissues. The aim of this study was to investigate the functional roles of miR-221 and miR-222 in prostate cancer (PCa) cells.

Methods:

A CRPC miRNA signature was constructed by PCR-based array methods. Functional studies of differentially expressed miRNAs were analysed using PCa cells. The association between miRNA expression and overall survival was estimated by the Kaplan–Meier method. In silico database and genome-wide gene expression analyses were performed to identify molecular targets regulated by the miR-221/222 cluster.

Results:

miR-221 and miR-222 were significantly downregulated in PCa and CRPC specimens. Kaplan–Meier survival curves showed that low expression of miR-222 predicted a short duration of progression to CRPC. Restoration of miR-221 or miR-222 in cancer cells revealed that both miRNAs significantly inhibited cancer cell migration and invasion. Ecm29 was directly regulated by the miR-221/222 cluster in PCa cells.

Conclusions:

Loss of the tumour-suppressive miR-221/222 cluster enhanced migration and invasion in PCa cells. Our data describing targets regulated by the tumour-suppressive miR-221/222 cluster provide insights into the mechanisms of PCa and CRPC progression.     

MicroRNA expression signature of oral squamous cell carcinoma: functional role of microRNA-26a/b in the modulation of novel cancer pathways

Background:

MicroRNAs (miRNAs) have been shown to play major roles in carcinogenesis in a variety of cancers. The aim of this study was to determine the miRNA expression signature of oral squamous cell carcinoma (OSCC) and to investigate the functional roles of miR-26a and miR-26b in OSCC cells.

Methods:

An OSCC miRNA signature was constructed by PCR-based array methods. Functional studies of differentially expressed miRNAs were performed to investigate cell proliferation, migration, and invasion in OSCC cells. In silico database and genome-wide gene expression analyses were performed to identify molecular targets and pathways mediated by miR-26a/b.

Results:

miR-26a and miR-26b were significantly downregulated in OSCC. Restoration of both miR-26a and miR-26b in cancer cell lines revealed that these miRNAs significantly inhibited cancer cell migration and invasion. Our data demonstrated that the novel transmembrane TMEM184B gene was a direct target of miR-26a/b regulation. Silencing of TMEM184B inhibited cancer cell migration and invasion, and regulated the actin cytoskeleton-pathway related genes.

Conclusions:

Loss of tumour-suppressive miR-26a/b enhanced cancer cell migration and invasion in OSCC through direct regulation of TMEM184B. Our data describing pathways regulated by tumour-suppressive miR-26a/b provide new insights into the potential mechanisms of OSCC oncogenesis and metastasis.     

Circulating microRNAs as prognostic therapy biomarkers in head and neck cancer patients

Background:

The prediction of therapy response in head and neck squamous cell cancer (HNSCC) requires biomarkers, which are also a prerequisite for personalised therapy concepts. The current study aimed to identify therapy-responsive microRNAs (miRNAs) in the circulation that can serve as minimally invasive prognostic markers for HNSCC patients undergoing radiotherapy.

Methods:

We screened plasma miRNAs in a discovery cohort of HNSCC patients before therapy and after treatment. We further compared the plasma miRNAs of the patients to age- and sex-matched healthy controls. All miRNAs identified as biomarker candidates were then confirmed in an independent validation cohort of HNSCC patients and tested for correlation with the clinical outcome.

Results:

We identified a signature of eight plasma miRNAs that differentiated significantly (P=0.003) between HNSCC patients and healthy donors. MiR-186-5p demonstrated the highest sensitivity and specificity to classify HNSCC patients and healthy individuals. All therapy-responsive and patient-specific miRNAs in plasma were also detectable in tumour tissues derived from the same patients. High expression of miR-142-3p, miR-186-5p, miR-195-5p, miR-374b-5p and miR-574-3p in the plasma correlated with worse prognosis.

Conclusions:

Circulating miR-142-3p, miR-186-5p, miR-195-5p, miR-374b-5p and miR-574-3p represent the most promising markers for prognosis and therapy monitoring in the plasma of HNSCC patients. We found strong evidence that the circulating therapy-responsive miRNAs are tumour related and were able to validate them in an independent cohort of HNSCC patients.     

miRNA profiling in metastatic renal cell carcinoma reveals a tumour-suppressor effect for miR-215

Background:

Renal cell carcinoma (RCC) is the most common neoplasm of the adult kidney. Metastatic RCC is difficult to treat. The 5-year survival rate for metastatic RCC is ⩽10%. Recently, microRNAs (miRNAs) have been shown to have a role in cancer metastasis and potential as prognostic biomarkers in cancer.

Method:

We performed a miRNA microarray to identify a miRNA signature characteristic of metastatic compared with primary RCCs. We validated our results by quantitative real-time PCR. We performed experimental and bioinformatic analyses to explore the involvement of miR-215 in RCC progression and metastasis.

Results:

We identified 65 miRNAs that were significantly altered in metastatic compared with primary RCCs. We validated our results by examining the expression of miR-10b, miR-126, miR-196a, miR-204 and miR-215, in two independent cohorts of patients. We showed that overexpression of miR-215 decreased cellular migration and invasion in an RCC cell line model. In addition, through gene expression profiling, we identified direct and indirect targets of miR-215 that can contribute to tumour metastasis.

Conclusion:

Our analysis showed that miRNAs are altered in metastatic RCCs and can contribute to kidney cancer metastasis through different biological processes. Dysregulated miRNAs represent potential prognostic biomarkers and may have therapeutic applications in kidney cancer.     

Identifying microRNAs regulating B7-H3 in breast cancer: the clinical impact of microRNA-29c

Background:

B7-H3, an immunoregulatory protein, is overexpressed in several cancers and is often associated with metastasis and poor prognosis. Here, our aim was to identify microRNAs (miRNAs) regulating B7-H3 and assess their potential prognostic implications in breast cancer.

Methods:

MicroRNAs targeting B7-H3 were identified by transfecting two breast cancer cell lines with a library of 810 miRNA mimics and quantifying changes of B7-H3 protein levels using protein lysate microarrays. For validations we used western immunoblotting and 3′-UTR luciferase assays. Clinical significance of the miRNAs was assayed by analysing whether their expression levels correlated with outcome in two cohorts of breast cancer patients (142 and 81 patients).

Results:

We identified nearly 50 miRNAs that downregulated B7-H3 protein levels. Western immunoblotting validated the impact of the 20 most effective miRNAs. Thirteen miRNAs (miR-214, miR-363*, miR-326, miR-940, miR-29c, miR-665, miR-34b*, miR-708, miR-601, miR-124a, miR-380-5p, miR-885-3p, and miR-593) targeted B7-H3 directly by binding to its 3′-UTR region. Finally, high expression of miR-29c was associated with a significant reduced risk of dying from breast cancer in both cohorts.

Conclusions:

We identified miRNAs efficiently downregulating B7-H3 expression. The expression of miR-29c correlated with survival in breast cancer patients, suggesting a tumour suppressive role for this miRNA.     

MicroRNA-126 inhibits invasion in bladder cancer via regulation of ADAM9

Background:

The miRNA deregulation is commonly observed in human malignancies, where they act as tumour suppressors or oncogenes. Despite the association of several miRNAs with bladder cancer, little is known about the miRNAs that contribute to bladder cancer progression from non-muscle invasive (NMI) to muscle-invasive (MI) disease.

Methods:

We first profiled the expression of miRNAs and mRNAs in a cohort of urothelial carcinomas and further characterised the role of miR-126 in invasion, as it emerged as the most downregulated miRNA between MI and NMI tumours.

Results:

We found that restoration of miR-126 levels attenuated the invasive potential of bladder cancer cells. Mechanistically, we identified the role of miR-126 in invasion through its ability to target ADAM9. Notably, a significant inverse correlation between miR-126 and ADAM9 expression was observed, where ADAM9 was upregulated in MI bladder cancer cells. While knockdown of ADAM9 attenuated the invasiveness of cells with low miR-126 levels, experimental upregulation of ADAM9 recapitulated the invasive phenotype. Furthermore, ADAM9 expression assessed by immunohistochemistry significantly correlated with poor prognosis in patients with urothelial carcinoma.

Conclusions:

In this study we describe the role of miR-126 in bladder cancer progression, identifying miR-126 and ADAM9 as potential clinical biomarkers of disease aggressiveness.