The role of microRNAs in gallbladder cancer

Micro-RNAs With Prognostic Significance in Gallbladder Cancer: A Systematic Review and Meta-Analysis

Gallbladder cancer (GBC) stands out as one of the most widespread malignancies impacting the biliary tract globally. Despite increasing interest, to the best of our knowledge, no meta-analysis has been undertaken to amalgamate the existing data concerning the prognostic significance of micro-RNAs (miRNAs) in GBC in comparison to studies on miRNAs in other cancers. Hence, this systematic review and meta-analysis aimed at determining the prognostic significance of miRNAs in GBC patients. Comprehensive literature searches were conducted across PubMed, Cochrane Library, Ovid, Scopus, and Science Direct databases. Studies that evaluated the association between miRNAs and overall survival in GBC patients were included. Random-effect meta-analysis was employed to pool hazard ratios (HRs) and their 95% confidence intervals (CIs) across studies. A total of 15 studies, encompassing 16 miRs, were included for our analysis. The pooled analysis revealed that a high expression of miR-204, miR-7-2-3p, miR-29c-3p, miR-125b, miR-20a, miR-139-5p, miR-141, miR-92b-3p, miR-335, and miR-372 was significantly associated with poor prognosis and increased risk (HR>1 and the upper bound of the 95% CI>1). Additionally, these miRNAs were associated with the overall survival (HR = 1.56, 95% CI = 0.91-2.20, I2 = 91.82%). Significant heterogeneity was observed and could be attributed to the limited number of studies available on the GBC and significant reliance on quantitative real-time PCR for the detection of miRNAs. In conclusion, specific miRNAs exhibit prognostic significance in GBC, with potential implications for patient stratification and targeted therapeutic interventions. However, due to the heterogeneity among studies, these findings should be interpreted cautiously and validated in larger cohorts.

Identification of genes associated with gall bladder cell carcinogenesis: Implications in targeted therapy of gall bladder cancer

Gall bladder cancer (GBC) is becoming a very devastating form of hepatobiliary cancer in India. Every year new cases of GBC are quite high in India. Despite recent advanced multimodality treatment options, the survival of GBC patients is very low. If the disease is diagnosed at the advanced stage (with local nodal metastasis or distant metastasis) or surgical resection is inoperable, the prognosis of those patients is very poor. So, perspectives of targeted therapy are being taken. Targeted therapy includes hormone therapy, proteasome inhibitors, signal transduction and apoptosis inhibitors, angiogenesis inhibitors, and immunotherapeutic agents. One such signal transduction inhibitor is the specific short interfering RNA (siRNA) or short hairpin RNA (shRNA). For developing siRNA-mediated therapy shRNA, although several preclinical studies to evaluate the efficacy of these key molecules have been performed using gall bladder cells, many more clinical trials are required. To date, many such genes have been identified. This review will discuss the recently identified genes associated with GBC and those that have implications in its treatment by siRNA or shRNA.

The potential role of miRNAs in the pathogenesis of gallbladder cancer - A focus on signaling pathways interplay

microRNAs (also known as miRNAs or miRs) are a class of small non-coding RNAs that play a critical role in post-transcriptional gene regulation as negative gene regulators by binding complementary sequences in the 3'-UTR of target messenger RNAs (mRNAs) leading to translational repression and/or target degradation a wide range of genes and biological processes, including cell proliferation, invasion, migration, and apoptosis. The development and progression of cancer have been linked to the anomalous expression of miRNAs. According to recent studies, miRNAs have been found to regulate the expression of cancer-related genes through multiple signaling pathways in gallbladder cancer (GBC). Besides, miRNAs are implicated in several modulatory signaling pathways of GBC, including the Notch signaling pathway, JAK/STAT signaling pathway, protein kinase B (AKT), and Hedgehog signaling pathway. This review summarizes our current knowledge of the functions of miRNAs in the mechanisms underlying the pathogenic symptoms of GBC and illustrates their potential significance as treatment targets.

Circulating microRNAs in gallbladder cancer: Is serum assay of diagnostic value?

The microRNAs (miRNAs) in circulation could serve as biomarkers for cancer detection. Gallbladder carcinoma (GBC) is mostly asymptomatic; therefore, using microRNAs (miRNAs) as an early diagnostic biomarker could be a valuable tool. We aimed to identify the tumor-associated miR-1, miR130, miR-146, miR-182, and miR-21expression in serum as a biomarker for early detection of GBC and identify their possible diagnostic role. The study group comprised of paired serum and tissue samples from 34 GBC, 19 cholecystitis (CC), 21 normal controls (uninflamed gall bladder), and additional 29 serum-only samples of GBC. Total RNA was isolated using a commercially available RNA isolation kit (Applied Biosystem, USA) and reverse transcribed using Advanced Taqman MicroRNA reverse transcription kit. The relative expression of miRNAs was analyzed using Quantitative real-time polymerase chain reaction. The diagnostic potential of these miRNAs was assessed by ROC analysis. In paired samples, the trend towards up and down regulation for miR-182, miR-21, miR-1, miR-130, and miR-146 was similar in both tissue and sera of GBC. The expression pattern of serum miR-1, miR130, and miR-146 gradually decreased from normal control (NC) to CC to GBC, while miR-21 and miR-182 gradually increased from NC to CC to GBC. The miR-1, miR-121, miR-182, and miR-146 significantly differed between CC vs. early stage and early stage vs. NC. Among these miRNAs, the sensitivity of miR-1 (85.71 %) was the highest, and the specificity of miR-21 was the highest (92.73 %). The combined sensitivity for miRNAs ranged from 73.13 % (CI: 60.90-83.24 %) to 98.63 % (CI: 89.0-99.61 %); however, the specificity was lower. In stage I&II vs. III&IV discrimination, the diagnostic sensitivity of miR-1 was highest (89.36 %, CI: 76.90-96.45). The two miRNAs, in combination, increase the diagnostic sensitivity. Circulating serum miRNAs may provide a new approach for clinical application. Panels of specific circulating miRNA, which require further validation, could be potential non-invasive diagnostic biomarkers for GBC in combination with abnormal radio diagnostic scans.

Circulating miR-141 as a potential biomarker for diagnosis, prognosis and therapeutic targets in gallbladder cancer

MicroRNA-141(miR-141) has been reported to play vital roles in the regulation of carcinogenesis and cancer progression. However, the biological function of miR-141 in GBC has received less attention. The aim of this study was to estimate the potential value of the expression level of miR-141 as a diagnostic and prognostic blood-based biomarker in gallbladder cancer (GBC) patients. Meanwhile, to explore its biological role in GBC cells. RT-PCR was employed to confirm the expression of miR-141 in ten paired tissue samples (10 GBC tissues and 10 adjacent normal gallbladder tissues), GBC cell lines and peripheral blood specimens from 98 GBC patients and 60 healthy controls. MTT assay was used to evaluate the GBC cells proliferation and flow cytometry was used to detect the cell apoptosis. Receiver operating characteristic curve analysis and the area under the curve (AUC) were used to evaluate the value of miR-141 plasma levels for GBC diagnosis. Finally, clinicopathological and survival data of all GBC patients were collected and analyzed. Here, we confirmed that the expression of miR-141 were upregulated in primary gallbladder cancer cells and tissues compared with human gallbladder epithelial cells and adjacent normal tissues (P < 0.0001). Meanwhile, we found that downregulated expression of miR-141 by miR-141 inhibitor could induce apoptosis and inhibit proliferation of GBC cells. Additionally, elevated plasma miR-141 expression was also detected in the peripheral blood of GBC patients compared with healthy controls (P < 0.0001). The AUC value of miR-141 for GBC diagnosis was 0.894 (95% CI 0.843–0.945), which was more valuable than those including carcinoembryonic antigen (CEA) (0.713, 95% CI 0.633–0.793), carbohydrate antigen 125 (CA125) (0.837, 95% CI 0.776–0.899) and carbohydrate antigen 19–9 (CA19-9) (0.869, 95% CI 0.813–0.924). The high expression level of miR-141 in plasma was significantly associated with tumor invasion (P = 0.008), lymph node metastasis (P < 0.0001) and advanced pathologic tumor/node/metastasis (pTNM) stage (P = 0.009). More importantly, high plasma miR-141 expression was an independent prognostic factor for predicting poorer long-term survival in GBC patients. Elevated expression of circulating miR-141 in peripheral blood might be a potential novel biomarker for diagnosis and prognosis of GBC patients. Downregulated expression of miR-141 could inhibit proliferation and induce apoptosis of GBC cells, that provide a potential therapeutic target for GBC.

Meta-analysis of transcriptomics data identifies potential biomarkers and their associated regulatory networks in gallbladder cancer

Aim

This study aimed to identify key genes, non-coding RNAs, and their possible regulatory interactions during gallbladder cancer (GBC).

Background

The early detection of GBC, i.e. before metastasis, is restricted by our limited knowledge of molecular markers and mechanism(s) involved during carcinogenesis. Therefore, identifying important disease-associated transcriptome-level alterations can be of clinical importance.

Methods

In this study, six NCBI-GEO microarray dataseries of GBC and control tissue samples were analyzed to identify differentially expressed genes (DEGs) and non-coding RNAs {microRNAs (DEmiRNAs) and long non-coding RNAs (DElncRNAs)} with a computational meta-analysis approach. A series of bioinformatic methods were applied to enrich functional pathways, create protein-protein interaction networks, identify hub genes, and screen potential targets of DEmiRNAs and DElncRNAs. Expression and interaction data were consolidated to reveal putative DElncRNAs:DEmiRNAs:DEGs interactions.

Results

In total, 351 DEGs (185 downregulated, 166 upregulated), 787 DEmiRNAs (299 downregulated, 488 upregulated), and 7436 DElncRNAs (3127 downregulated, 4309 upregulated) were identified. Eight genes (FGF, CDK1, RPN2, SEC61A1, SOX2, CALR, NGFR, and NCAM) were identified as hub genes. Genes associated with ubiquitin ligase activity, N-linked glycosylation, and blood coagulation were upregulated, while those for cell-cell adhesion, cell differentiation, and surface receptor-linked signaling were downregulated. DEGs-DEmiRNAs-DElncRNAs interaction network identified 46 DElncRNAs to be associated with 28 DEmiRNAs, consecutively regulating 27 DEGs. DEmiRNAs-hsa-miR-26b-5p and hsa-miR-335-5p; and DElnRNAs-LINC00657 and CTB-89H12.4 regulated the highest number of DEGs and DEmiRNAs, respectively.

Conclusion

The current study has identified meaningful transcriptome-level changes and gene-miRNA-lncRNA interactions during GBC and laid a platform for future studies on novel prognostic and diagnostic markers in GBC.

Liquid biopsy in cholangiocarcinoma: Current status and future perspectives

Cholangiocarcinoma (CCA) are a heterogeneous group of tumors in terms of aetiology, natural history, morphological subtypes, molecular alterations and management, but all sharing complex diagnosis, management, and poor prognosis. Several mutated genes and epigenetic changes have been detected in CCA, with the potential to identify diagnostic and prognostic biomarkers and therapeutic targets. Accessing tumoral components and genetic material is therefore crucial for the diagnosis, management and selection of targeted therapies; but sampling tumor tissue, when possible, is often risky and difficult to be repeated at different time points. Liquid biopsy (LB) represents a way to overcome these issues and comprises a diverse group of methodologies centering around detection of tumor biomarkers from fluid samples. Compared to the traditional tissue sampling methods LB is less invasive and can be serially repeated, allowing a real-time monitoring of the tumor genetic profile or the response to therapy. In this review, we analysis the current evidence on the possible roles of LB (circulating DNA, circulating RNA, exosomes, cytokines) in the diagnosis and management of patients affected by CCA.

Overexpression of microRNA-205-5p exerts suppressive effects on stem cell drug resistance in gallbladder cancer by down-regulating PRKCE

Some microRNAs (miRs or miRNAs) have been reported to function as tumor suppressors in gallbladder cancer (GBC). However, the specific effect of miR-205-5p on GBC remains unclear. The objective of the present study was to unravel the effects of miR-205-5p on the drug resistance in GBC. For this purpose, the expression of miR-205-5p and protein kinase C ϵ (PRKCE) was quantified in the peripheral blood sample harvested from GBC patients and healthy volunteers. Then the relationship between miR-205-5p and PRKCE was validated. After isolating the GBC stem cells, ectopic expression and depletion experiments were conducted to analyze the effect of miR-205-5p and PRKCE on cell proliferation, drug resistance, apoptosis, and colony formation rate as well as the expression of apoptotic factors (Bcl-2-associated X protein (Bax), B-cell lymphoma 2 (Bcl-2), and cleaved caspase 3). Finally, the mouse xenograft model of GBC was established to verify the function of miR-205-5p in vivo. Intriguingly, our results manifested that miR-205-5p was down-regulated, while PRKCE was up-regulated in peripheral blood samples and stem cells of patients with GBC. Moreover, miR-205-5p targeted PRKCE and negatively regulated its expression. The overexpression of miR-205-5p or silencing of PRKCE inhibited the drug resistance, proliferation, and colony formation rate while promoting apoptosis of GBC stem cells. Additionally, the overexpression of miR-205-5p attenuated drug resistance to gemcitabine but promoted the gemcitabine-induced cell apoptosis by inhibiting the PRKCE in vivo. Overall, an intimate correlation between miR-205-5p and PRKCE is a key determinant of drug resistance of GBC stem cells, thus, suggesting a novel miR-205-5p-based clinical intervention target for GBC patients.

miR-146b Functions as an Oncogene in Oral Squamous Cell Carcinoma by Targeting HBP1

Oral squamous cell carcinoma (OSCC) represents more than 90% of all oral cancer and is the most common oral threat around the world. In this study, we examined the roles of miR-146b in OSCC cells. The miR-146b expression in OSCC tissues and cell lines was evaluated by quantitative real-time PCR (qRT-PCR). MTT assay was used to investigate the impact of miR-146b on the growth of OSCC cells in vitro. Transwell assay was utilized to analyze the effect of miR-146b on the migration and invasion of OSCC cells. Target prediction and luciferase assay were employed to demonstrate the interaction between miR-146b and HMG-Box Transcription Factor 1 (HBP1). Western blot was carried out to investigate the protein expressions of HBP1 related genes. miR-146b expression was significantly higher in OSCC tissues and cells compared with paired normal tissues and normal oral keratinocyte cells. Inhibition of miR-146b decreased cell proliferation, migration, and invasion of OSCC cells. Further studies found that HBP1 was a direct target of miR-146b. Co-inhibition of HBP1 reversed the suppressive impact of miR-146b inhibition on OSCC cell proliferation, migration, and invasion. In conclusion-ourresults reveal that miR-146b potentially regulates the proliferation, migration, and invasion of OSCC cells through binding and downregulating HBP1 expression in OSCC cells.

Epigenetic Biomarkers in Gallbladder Cancer

Gallbladder cancer (GBC) is associated with various nongenetic and genetic factors. Lack of specific and sensitive diagnostic markers has significantly impacted the mortality of this disease. Here we discuss the recent discovery of epigenetic changes that show great promise as diagnostic biomarkers as well as potential therapeutic targets for GBC.

A Systemic Review on the Regulatory Roles of miR-34a in Gastrointestinal Cancer

MicroRNAs (miRNAs) are a class of endogenous non-coding single-stranded small-molecule RNAs that regulate gene expression by repressing target messenger RNA (mRNA) translation or degrading mRNA. miR-34a is one of the most important miRNAs participating in various physiological and pathological processes. miR-34a is abnormally expressed in a variety of tumors. The roles of miR-34a in gastrointestinal cancer (GIC) draw lots of attention. Numerous studies have demonstrated that dysregulated miR-34a is closely related to the proliferation, differentiation, migration, and invasion of tumor cells, as well as the diagnosis, prognosis, treatment, and chemo-resistance of tumors. Thus, we systematically reviewed the abnormal expression and regulatory roles of miR-34a in GICs including esophageal cancer (EC), gastric cancer (GC), colorectal cancer (CRC), hepatocellular carcinoma (HCC), pancreatic cancer (PC), and gallbladder cancer (GBC). It may provide a profile of versatile roles of miR-34a in GICs.

Molecular pathways and potential biomarkers in gallbladder cancer: A comprehensive review

The most common malignancy of the biliary tract, gallbladder cancer (GBC) often has a dismal prognosis. The aggressive nature of the tumor, delayed diagnosis at advanced stages of the disease, and lack of effective treatment options are some of the factors that contribute to a poor outcome. Early detection and accurate assessment of disease burden is critical to optimize management and improve long-term survival, as well as identify patients for adjuvant therapy and clinical trials. With recent advances in the understanding of the molecular pathogenesis of GBC, several specific diagnostic and biomarkers have been proposed as being of diagnostic and prognostic importance. Indeed, identification of novel diagnostic and prognostic markers has an important role in early diagnosis and development of targeted therapies among patients with GBC. Next-generation sequencing technology and genomewide data analysis have provided novel insight into understanding the molecular pathogenesis of biliary tract cancers, thereby identifying potential biomarkers for clinical use. We herein review available GBC biomarkers and the potential clinical implications in the management of GBC.

Encapsulated miR-200c and Nkx2.1 in a nuclear/mitochondria transcriptional regulatory network of non-metastatic and metastatic lung cancer cells

BACKGROUND

MicroRNAs are noncoding RNA molecules of ~ 22 nucleotides with diagnostic and therapeutic action [Curr Drug Targets, 2015. 16(12): p. 1381-403], affecting the expression of mRNAs involved in invasion, migration, and development [Oncotarget, 2015. 6(9): p. 6472-98, Cancer Manag Res, 2014. 6: p. 205-16]. miR-200c is part of the miR-200c/141 cluster on chromosome 12p13. Its mechanism of action when encapsulated is critical in lung cancer when patients express changes in miRNAs. miR-200c be a potential biomarkers for various lung diseases. As a potential therapy, miR-200c can impacts lives as target lung cancer is a leading cause of death with about 234,000 cases annually, high heterogeneity, complex screening, and a 5-year survival rate of 16% [CA Cancer J Clin, 2016.66(1): p. 7-30]. Encapsulated miR-200c efficiently enhances bioavailability, pharmacokinetics of therapeutics and targeting to cells, improves efficacy and provides potential cure.

METHODS

The functions of miR-200c were determined in non-metastatic KW-634 and metastatic 821-T4 and 821-LN mouse lung cancer cell lines after various Nano vehicle treatments. Viability and cytotoxicity were determined by cell cycle and quantitative real-time PCR analyses were used to quantify levels of miR-200c and its target genes. In situ hybridization was used to visualize patterns of expression of miR-200c and others in the lung and many organs. Next-generation sequencing accession number GSE125000, invasion and migration assays using transwell chambers, and ActivSignal were used to elucidate the activation and inhibition profiles and perform direct expression measurements and modification of cellular components.

RESULTS

Due to their effectiveness as intracellular vesicles transporting miR-200c into, out, and between parts of the cells, miR-200c is encapsulated with cholesterol, an integral part of the biological membranes with very important physical properties of the vehicle. Nano miR-200c showed efficient cellular uptake in KW-634, 821-T4, and 821-LN cells with important changes in gene expression and new isoforms. In KW-634, when treated with encapsulated miR-200c and compare to the non-encapsulated control; miR-29b increased by 5261-fold, and in 821-T4/LN, miR-1247 increased by 150-fold. Conversely, miR-1247 and miR-675 decreased by 348 and 1029.5-fold, respectively. miR-189 decreased by 34-fold in treated 821-T4 cells. A reduction of growth was observed only after 48 h of treatment with Nano miR-200c. Moreover, labeling the vehicle with carboxy-fluorescein showed that the encapsulated particles enter the nucleus and mitochondria. Encapsulated miR-200c by entering the cells, the nucleus and mitochondria, trigger changes in cell cycle phases with 4 up to 12 fold percentage in G2 and S phase respectively compare to miR-200c. Endogenous expression of Nkx2.1, miR-200c, and their targets Myb, Nfib, Six4 and Six1 showed an inverse correlation, as observed in development.

CONCLUSIONS

Little is known about miR-200c involvement in regulatory processes. Nano miR-200c affects invasion and migration mechanisms. The expression of encapsulated miR-200c contributes to the inhibition/activation of Kras, EMT, Hippo, regulatory pathways and blockers of metastasis. Delivery of miR-200c increases the expression of miR-29b, an EMY regulator, and miR-1247, an inhibitor of cancer genes, both tumor suppressors involved in lung metastasis. Encapsulated miR-200c act on different proteins that regulates cell cycle pathways. These findings represent a part of a regulatory network providing new insights towards improvement of therapy.

The microRNA miR-33a suppresses IL-6-induced tumor progression by binding Twist in gallbladder cancer

Cytokine is a key molecular link between chronic inflammation and gallbladder cancer (GBC) progression. The potential mechanism of cytokine-associated modulation of microRNAs (miRNAs) expression in GBC progression is not fully understood. In this study, we investigated the biological effects and prognostic significance of interleukin-6 (IL-6) -induced miRNAs in the development of GBC. We identify that inflammatory cytokine, IL-6 promotes proliferation, migration, invasion and epithelial-mesenchymal transition (EMT) of GBC both in vitro and in vivo. Among all the changed miRNAs in miRNA profiling, miR-33a expression was significantly decreased in IL-6 treated GBC cell lines, as well as in GBC tissues compared with case-matched normal tissues and cholecystitis tissues. In turn, miR-33a suppresses IL-6-induced tumor metastasis by directly binding Twist which was identified as an EMT marker. High expression of miR-33a suppressed xenograft tumor growth and dissemination in nude mice. The downregulation of miR-33a was closely associated with advanced clinical stage, lymph node metastasis, and poor clinical outcomes in patients with GBC. miR-33a acts as a tumor suppressor miRNA in GBC progression and may be considered for the development of potential therapeutics against GBC.

Epithelial-to-mesenchymal transition in gallbladder cancer: from clinical evidence to cellular regulatory networks

Gallbladder cancer (GBC), with late diagnosis, rapid disease progression and early metastasis, is a highly aggressive malignant tumor found worldwide. Patients with GBC have poor survival, low curative resection rates and early recurrence. For such a lethal tumor, uncovering the mechanisms and exploring new strategies to prevent tumor progression and metastasis are critically important. Epithelial-to-mesenchymal transition (EMT) has a prominent role in the early steps of tumor progression and metastasis by initiating polarized epithelial cell transition into motile mesenchymal cells. Accumulating evidence suggests that EMT can be modulated by the cooperation of multiple mechanisms affecting common targets. Signaling pathways, transcriptional and post-transcriptional regulation and epigenetic alterations are involved in the stepwise EMT regulatory network in GBC. Loss of epithelial markers, acquisition of mesenchymal markers and dysregulation of EMT-inducing transcription factors (EMT-TFs) have been observed and are associated with the clinicopathology and prognosis of GBC patients. Therefore, EMT may be a detectable and predictable event for predicting GBC progression and metastasis in the clinic. In this review, we will provide an overview of EMT from the clinical evidence to cellular regulatory networks that have been studied thus far in clinical and basic GBC studies.

Genome-wide profiling of micro-RNA expression in gefitinib-resistant human lung adenocarcinoma using microarray for the identification of miR-149-5p modulation

To understand the mechanism involved in gefitinib resistance, we established gefitinib-resistant human HCC827/GR-8-1 cell line from the parental HCC827 cell line. We compared the micro-RNA expression profiles of the HCC827 cells HCC827/GR-8-1 using Agilent micro-RNA microarrays. The micro-RNAs, such as the miR-149-5p, were up- or downregulated and associated with acquired gefitinib resistance. Quantitative real-time polymerase chain reaction was then performed to verify the expression patterns of different micro-RNAs. The result showed that miR-149-5p was upregulated in the HCC827/GR-8-1 cell line. To investigate the biological function of miR-149-5p in non-small cell lung cancer cells acquired gefitinib resistance, we examined cell proliferation using a cell counting kit-8 assay. Cell viability was evaluated after the miR-149-5p mimics, inhibitors, and negative control were separately transfected into the non-small cell lung cancer cells. The results showed that the non-small cell lung cancer cells transfected with miR-149-5p mimics exhibited reduced cell motility. The drug-sensitivity assay results revealed that the overexpression of miR-149-5p effectively evaluates the half maximal inhibitory concentration values of the cell in response to gefitinib, and the downregulation of miR-149-5p can attenuate the half maximal inhibitory concentration values of the cell lines in response to gefitinib. Furthermore, the levels of miR-149-5p in the HCC827 and HCC827/GR-8-1 cells were inversely correlated with caspase-3 expression. In conclusion, this study revealed that miR-149-5p is upregulated in the HCC827/GR-8-1 cells and involved in the acquired gefitinib resistance.

The Emerging Role of miRNAs and Their Clinical Implication in Biliary Tract Cancer

Biliary tract cancers are aggressive malignancies that include gallbladder cancer and tumors of intra- and extrahepatic ducts and have a poor prognosis. Surgical resection remains the main curative therapy. Nevertheless, numerous patients experience recurrence even after radical surgery. This scenario drives the research to identify biliary tract cancer biomarkers despite the limited progress that has been made. Recently, a large number of studies have demonstrated that deregulated expression of microRNAs is closely associated with cancer development and progression. In this review, we highlight the role and importance of microRNAs in biliary tract cancers with an emphasis on utilizing circulating microRNAs as potential biomarkers. Additionally, we report several single-nucleotide polymorphisms in microRNA genes that are associated with the susceptibility of biliary tract tumors.