Repression of Dicer is associated with invasive phenotype and chemoresistance in ovarian cancer

Exploration of molecular markers related to chemotherapy efficacy of hepatoid adenocarcinoma of the stomach

PURPOSE

Preoperative neoadjuvant chemotherapy may not improve the prognosis of patients with hepatoid adenocarcinoma of the stomach (HAS), a rare pathological type of gastric cancer. Thus, the study aimed at the genomic and transcriptomic impacts of preoperative chemotherapy on HAS.

METHODS

Patients with HAS who underwent surgical resection at Peking University Cancer Hospital were retrospectively included in this study. Whole exome sequencing and transcriptome sequencing were performed on pre-chemotherapy, non-chemotherapy and post-chemotherapy samples. We then compared the alterations in molecular markers between the post-chemotherapy and non-chemotherapy groups, and between the chemotherapy-effective and chemotherapy-ineffective groups, respectively.

RESULTS

A total of 79 tumor samples from 72 patients were collected. Compared to the non-chemotherapy group, the mutation frequencies of several genes were changed after chemotherapy, including TP53. In addition, there was a significant increase in the frequency of frameshift mutations and cytosine transversion to adenine (C > A), appearance of COSMIC signature 6 and 14, and a reduced gene copy number amplification. Interestingly, the same phenomenon was observed in chemotherapy-ineffective patients. In addition, many HAS patients had ERBB2, FGFR2, MET and HGF gene amplification. Moreover, the expression of immune-related genes, especially those related to lymphocyte activation, was down-regulated after chemotherapy.

CONCLUSION

Chemotherapy is closely associated with changes in the molecular characteristics of HAS. After chemotherapy, at genomic and transcriptome level, many features were altered. These changes may be molecular markers of poor chemotherapeutic efficacy and play an important role in chemoresistance in HAS. In addition, ERBB2, FGFR2, MET and HGF gene amplification may be potential therapeutic targets for HAS.

Silencing of Dicer enhances dacarbazine resistance in melanoma cells by inhibiting ADSL expression

Dacarbazine (DTIC) is the primary first-line treatment for advanced-stage metastatic melanoma; thus, DTIC resistance is poses a major challenge. Therefore, investigating the mechanism underlying DTIC resistance must be investigated. Dicer, a type III cytoplasmic endoribonuclease, plays a pivotal role in the maturation of miRNAs. Aberrant Dicer expression may contribute to tumor progression, clinical aggressiveness, and poor prognosis in various tumors. Dicer inhibition led to a reduction in DTIC sensitivity and an augmentation in stemness in melanoma cells. Clinical analyses indicated a low Dicer expression level as a predictor of poor prognosis factor. Metabolic alterations in tumor cells may interfere with drug response. Adenylosuccinate lyase (ADSL) is a crucial enzyme in the purine metabolism pathway. An imbalance in ADSL may interfere with the therapeutic efficacy of drugs. We discovered that DTIC treatment enhanced ADSL expression and that Dicer silencing significantly reduced ADSL expression in melanoma cells. Furthermore, ADSL overexpression reversed Dicer silencing induced DTIC resistance and cancer stemness. These findings indicate that Dicer-mediated ADSL regulation influences DTIC sensitivity and stemness in melanoma cells.

Mechanisms of Regulation of the Expression of miRNAs and lncRNAs by Metformin in Ovarian Cancer

Ovarian cancer (OC) is one of the most lethal gynecological malignancies. The use of biological compounds such as non-coding RNAs (ncRNAs) is being considered as a therapeutic option to improve or complement current treatments since the deregulation of ncRNAs has been implicated in the pathogenesis and progression of OC. Old drugs with antitumoral properties have also been studied in the context of cancer, although their antitumor mechanisms are not fully clear. For instance, the antidiabetic drug metformin has shown pleiotropic effects in several in vitro models of cancer, including OC. Interestingly, metformin has been reported to regulate ncRNAs, which could explain its diverse effects on tumor cells. In this review, we discuss the mechanism of epigenetic regulation described for metformin, with a focus on the evidence of metformin-dependent microRNA (miRNAs) and long non-coding RNA (lncRNAs) regulation in OC.

Dicer-mediated miR-200b expression contributes to cell migratory/invasive abilities and cancer stem cells properties of breast cancer cells

Distant metastasis is the leading cause of death in patients with breast cancer. Despite considerable treatment advances, the clinical outcomes of patients with metastatic breast cancer remain poor. CSCs can self-renew, enhancing cancer progression and metastasis. Dicer, a microRNA (miRNA) processing–related enzyme, is required for miRNA maturation. Imbalanced Dicer expression may be pivotal in cancer progression. However, whether and how Dicer affects the stemness of metastatic breast cancer cells remains unclear. Here, we hypothesized that Dicer regulates the migration, invasion, and stemness of breast cancer cells. We established highly invasive cell lines (MCF-7/I-3 and MDA-MB-231/I-3) and observed that Dicer expression was conspicuously lower in the highly invasive cells than in the parental cells. The silencing of Dicer significantly enhanced the cell migratory/invasive abilities and CSCs properties of the breast cancer cells. Conversely, the overexpression of Dicer in the highly invasive cells reduced their migration, invasion, and CSCs properties. Our bioinformatics analyses demonstrated that low Dicer levels were correlated with increased breast cancer risk. Suppression of Dicer inhibited miR-200b expression, whereas miR-200b suppression recovered Dicer knockdown–induced migration, invasion, and cancer stem cells (CSCs) properties of the breast cancer cells. Thus, our findings reveal that Dicer is a crucial regulator of the migration, invasion, and CSCs properties of breast cancer cells and is significantly associated with poor survival in patients with breast cancer.

Transcriptional suppression of Dicer by HOXB-AS3/EZH2 complex dictates Sorafenib resistance and cancer stemness

Sorafenib is multi-kinase inhibitor for the standard treatment of advanced liver cancer patients. However, acquired resistance to sorafenib is responsible for a poor prognosis. Therefore, uncovering the molecular mechanisms underlying sorafenib sensitization can provide biomarkers for sorafenib treatment and improve sorafenib activity in a precise medication. Here, we report that epigenetic suppression of Dicer by HOXB-AS3/EZH2 complex is responsible for sorafenib resistance. We observed that Dicer expression is inversely correlated with EZH2 levels, HOXB-AS3 expression, sorafenib resistance and cancer stem cell properties in liver cancer patients. Furthermore, ectopic expression of Dicer induced liver cancer cells re-sensitization to sorafenib. Mechanistically, we found HOXB-AS3 physically interacts with EZH2 and recruits EZH2 to the Dicer promoter, resulting in epigenetic suppression of Dicer expression. These findings reveal that HOXB-AS3/EZH2 complex-mediated Dicer suppression plays an important role in sorafenib resistance and cancer stemness and provide potential therapeutic strategies for diagnosing and treating liver cancer patients.

Clinical significance of microRNA-200 and let-7 families expression assessment in patients with ovarian cancer

Ovarian cancer (OC) represents the most lethal malignancy in gynaecologic oncology practice and shows a high recurrence rate due to its early chemoresistance to first-line chemotherapy. Yet, timely selection of the correct treatment strategy is likely to prolong a patient's survival. MicroRNAs (miRNAs) are a class of short non-coding RNAs responsible for the expression of 30%-60% of human genes. In numerous studies, miRNAs have been used to provide the overall prognosis for patients and analyse the process's prevalence and responses to chemotherapy. In particular, miRNAs as markers for predicting the sensitivity of OC to platinum- and taxane-based chemotherapeutics can significantly improve the treatment efficacy. This article highlights two families of miRNAs: miR-200 and let-7, which are promising for further research on OC and its chemosensitivity.

ERK-mediated transcriptional activation of Dicer is involved in gemcitabine resistance of pancreatic cancer

Gemcitabine has been a commonly used therapeutic agent for treatment of pancreatic cancer. In the clinic, a growing resistance to gemcitabine has been observed in patients with pancreatic cancer, and investigation of the underlying mechanism of gemcitabine resistance is urgently required. The microRNA (miRNA)-producing enzyme, Dicer, is crucial for the maturation of miRNAs, and is involved in clinical aggressiveness, poor prognosis, and survival outcomes in various cancers, however, the role of Dicer in acquired gemcitabine resistance of pancreatic cancer is still not clear. Here, we found that Dicer expression was significantly increased in gemcitabine-resistant PANC-1 (PANC-1/GEM) cells compared with parental PANC-1 cells and observed a high level of Dicer correlated with increased risk of pancreatic cancer. Suppression of Dicer obviously decreased gemcitabine resistance in PANC-1/GEM cells; consistently, overexpression of Dicer in PANC-1 cells increased gemcitabine resistance. Moreover, we identified that transcriptional factor Sp1 targeted the promoter region of Dicer and found ERK/Sp1 signaling regulated Dicer expression in PANC-1/GEM cells, as well as positively correlated with pancreatic cancer progression and suggest that targeting the ERK/Sp1/Dicer pathway has potential therapeutic value for pancreatic cancer with acquired resistance to gemcitabine.

Identification of an immune gene signature for predicting the prognosis of patients with uterine corpus endometrial carcinoma

Background

Uterine corpus endometrial carcinoma (UCEC) is a frequent gynecological malignancy with a poor prognosis particularly at an advanced stage. Herein, this study aims to construct prognostic markers of UCEC based on immune-related genes to predict the prognosis of UCEC.

Methods

We analyzed expression data of 575 UCEC patients from The Cancer Genome Atlas database and immune genes from the ImmPort database, which were used for generation and validation of the signature. We constructed a transcription factor regulatory network based on Cistrome databases, and also performed functional enrichment and pathway analyses for the differentially expressed immune genes. Moreover, the prognostic value of 410 immune genes was determined using the Cox regression analysis. We then constructed and verified a prognostic signature. Finally, we performed immune infiltration analysis using TIMER-generating immune cell content.

Results

The immune cell microenvironment as well as the PI3K-Akt, and MARK signaling pathways were involved in UCEC development. The established prognostic signature revealed a ten-gene prognostic signature, comprising of PDIA3, LTA, PSMC4, TNF, SBDS, HDGF, HTR3E, NR3C1, PGR, and CBLC. This signature showed a strong prognostic ability in both the training and testing sets and thus can be used as an independent tool to predict the prognosis of UCEC. In addition, levels of B cells and neutrophils were significantly correlated with the patient’s risk score, while the expression of ten genes was associated with immune cell infiltrates.

Conclusions

In summary, the ten-gene prognostic signature may guide the selection of the immunotherapy for UCEC.

Dicing the Disease with Dicer: The Implications of Dicer Ribonuclease in Human Pathologies

Gene expression dictates fundamental cellular processes and its de-regulation leads to pathological conditions. A key contributor to the fine-tuning of gene expression is Dicer, an RNA-binding protein (RBPs) that forms complexes and affects transcription by acting at the post-transcriptional level via the targeting of mRNAs by Dicer-produced small non-coding RNAs. This review aims to present the contribution of Dicer protein in a wide spectrum of human pathological conditions, including cancer, neurological, autoimmune, reproductive and cardiovascular diseases, as well as viral infections. Germline mutations of Dicer have been linked to Dicer1 syndrome, a rare genetic disorder that predisposes to the development of both benign and malignant tumors, but the exact correlation of Dicer protein expression within the different cancer types is unclear, and there are contradictions in the data. Downregulation of Dicer is related to Geographic atrophy (GA), a severe eye-disease that is a leading cause of blindness in industrialized countries, as well as to psychiatric and neurological diseases such as depression and Parkinson's disease, respectively. Both loss and upregulation of Dicer protein expression is implicated in severe autoimmune disorders, including psoriasis, ankylosing spondylitis, rheumatoid arthritis, multiple sclerosis and autoimmune thyroid diseases. Loss of Dicer contributes to cardiovascular diseases and causes defective germ cell differentiation and reproductive system abnormalities in both sexes. Dicer can also act as a strong antiviral with a crucial role in RNA-based antiviral immunity. In conclusion, Dicer is an essential enzyme for the maintenance of physiology due to its pivotal role in several cellular processes, and its loss or aberrant expression contributes to the development of severe human diseases. Further exploitation is required for the development of novel, more effective Dicer-based diagnostic and therapeutic strategies, with the goal of new clinical benefits and better quality of life for patients.

MiRNA-103/107 in Primary High-Grade Serous Ovarian Cancer and Its Clinical Significance

High levels of miRNA-103/107 are associated with poor outcomes in the case of breast cancer patients. MiRNA-103/107-DICER axis may be one of the key regulators of cancer aggressiveness. MiRNA-103/107 expression levels have never been related to patients' clinicopathological data in epithelial ovarian cancer. We aimed to assess miRNA-103/107 expression levels in high grade serous ovarian cancer tissues. Expression levels of both miRNAs were related to the clinicopathological features and survival. We also evaluated expression levels of miRNA-103/107 and DICER in selected ovarian cancer cell lines (A2780, A2780cis, SK-OV-3, OVCAR3). We assessed the relative expression of miRNA-103/107 (quantitative reverse transcription-polymerase chain reaction) in fifty archival formalin-fixed paraffin-embedded tissue samples of primary high grade serous ovarian cancer. Then, miRNA-103/107 and DICER expression levels were evaluated in selected ovarian cancer cell lines. Additionally, DICER, N-/E-cadherin protein levels were assessed with the use of western blot. We identified miRNA-107 up-regulation in ovarian cancer in comparison to healthy tissues (p = 0.0005). In the case of miRNA-103, we did not observe statistically significant differences between cancerous and healthy tissues (p = 0.07). We did not find any correlations between miRNA-103/107 expression levels and clinicopathological features. Kaplan-Meier survival (disease-free and overall survival) analysis revealed that both miRNAs could not be considered as prognostic factors. SK-OV-3 cancer cell lines were characterized by high expression of miRNA-103/107, relatively low expression of DICER (western-blot), and relatively high N-cadherin levels in comparison to other ovarian cancer cell lines. Clinical and prognostic significance of miRNA-103/107 was not confirmed in our study.

Recent trends in targeting miRNAs for cancer therapy

OBJECTIVES

MicroRNAs (miRNAs) are a type of small noncoding RNA employed by the cells for gene regulation. A single miRNA, typically 22 nucleotides in length, can regulate the expression of numerous genes. Over the past decade, the study of miRNA biology in the context of cancer has led to the development of new diagnostic and therapeutic opportunities.

KEY FINDINGS

MicroRNA dysregulation is commonly associated with cancer, in part because miRNAs are actively involved in the mechanisms like genomic instabilities, aberrant transcriptional control, altered epigenetic regulation and biogenesis machinery defects. MicroRNAs can regulate oncogenes or tumour suppressor genes and thus when altered can lead to tumorigenesis. Expression profiling of miRNAs has boosted the possibilities of application of miRNAs as potential cancer biomarkers and therapeutic targets, although the feasibility of these approaches will require further validation.

SUMMARY

In this review, we will focus on how miRNAs regulate tumour development and the potential applications of targeting miRNAs for cancer therapy.

Histone Methyltransferase EZH2: A Therapeutic Target for Ovarian Cancer

Ovarian cancer is the fifth leading cause of cancer-related deaths in females in the United States. There were an estimated 22,440 new cases and 14,080 deaths due to ovarian cancer in 2017. Most patients present with advanced-stage disease, revealing the urgent need for new therapeutic strategies targeting pathways of tumorigenesis and chemotherapy resistance. While multiple genomic changes contribute to the progression of this aggressive disease, it has become increasingly evident that epigenetic events play a pivotal role in ovarian cancer development. One of the well-studied epigenetic modifiers, the histone methyltransferase EZH2, is a member of polycomb repressive complex 2 (PRC2) and is commonly involved in transcriptional repression. EZH2 is the enzymatic catalytic subunit of the PRC2 complex that can alter gene expression by trimethylating lysine 27 on histone 3 (H3K27). In ovarian cancer, EZH2 is commonly overexpressed and therefore potentially serves as an effective therapeutic target. Multiple small-molecule inhibitors are being developed to target EZH2, which are now in clinical trials. Thus, in this review, we highlight the progress made in EZH2-related research in ovarian cancer and discuss the potential utility of targeting EZH2 with available small-molecule inhibitors for ovarian cancer. Mol Cancer Ther; 17(3); 591-602. ©2018 AACR.

Role of Dicer in regulating oxaliplatin resistance of colon cancer cells

Colorectal cancer (CRC) is a major health problem due to its high mortality rate. The incidence of CRC is increasing in young individuals. Oxaliplatin (OXA) is an approved third-generation drug and is used for first-line chemotherapy in CRC. Although current standard chemotherapy improves the overall survival of CRC patients, an increasing number of reports of OXA resistance in CRC therapy indicates that resistance has become an urgent problem in clinical applications. Dicer is a critical enzyme involved in miRNA maturation. The expression of Dicer has been reported to be involved in the resistance to various drugs in cancer. In the present study, we aimed to investigate the role of Dicer in OXA resistance in CRC. We found that OXA treatment inhibited Dicer expression through decreasing the protein stability. OXA-induced Dicer protein degradation occurred through both proteasomal and lysosomal proteolysis, while the CHIP E3 ligase was involved in OXA-mediated Dicer ubiquitination and degradation. We established stable OXA-resistant clones from CRC cells, and observed that the CHIP E3 ligase was decreased, along with the increased Dicer expression in OXA-resistant cells. Knockdown of Dicer resensitized CRC cells to OXA treatment. In this study, we have revealed the role of miRNA biogenesis factors in OXA resistance in CRC cells.

Dicer affects cisplatin‑mediated apoptosis in epithelial ovarian cancer cells

Dicer is an essential enzyme that processes micro (mi)-RNA precursors into mature miRNAs, and serves a critical role in cancer development and progression by regulating gene expression. However, the role of Dicer in cisplatin‑mediated apoptosis and chemotherapy resistance in epithelial ovarian cancer (EOC) cells is poorly understood. In the present study, Dicer was expressed at low levels in cisplatin‑resistant A2780 cells when compared with parental cells. In addition, knocking down Dicer using short hairpin RNA decreased the sensitivity of A2780 and CAOV3 cells to cisplatin. Furthermore, downregulating Dicer significantly inhibited cisplatin‑induced apoptosis in ovarian cancer cells, and decreased the levels of proteins involved in apoptosis signaling pathways, including P73, P63, P53, caspase‑9 and caspase‑3. These findings indicated that Dicer may be a promising target for overcoming drug resistance in ovarian cancer.

miR-98-5p contributes to cisplatin resistance in epithelial ovarian cancer by suppressing miR-152 biogenesis via targeting Dicer1

Epithelial ovarian cancer (EOC) is a highly lethal gynecological malignancy, and cisplatin resistance is usually correlated with the poor prognosis of EOC. Increasing evidence indicates that the dysregulation of miRNAs is related to chemotherapy sensitivity. In this study, we revealed that miR-98-5p, a member of the let-7 family, was enriched in cisplatin-resistant EOC cells compared with cisplatin-sensitive cells, and could promote cisplatin resistance in EOC cells. Further studies showed that miR-98-5p could directly target the 3′-UTR of Dicer1 and suppress its expression, causing global miRNA downregulation. By miRNA array and qRT-PCR verification, we identified miR-152 as the vital downstream target of the miR-98-5p/Dicer1 axis in EOC cells. Moreover, we demonstrated that the ectopic expression of miR-152 reversed cisplatin resistance both in vitro and in vivo by targeting RAD51, a central member in homologous recombination. Importantly, miR-98-5p expression, as determined by in situ hybridization in tumor tissues, was associated with poor outcome of EOC patients. Together, these findings suggest the essential role of the miR-98-5p/Dicer1/miR-152 pathway in regulating cisplatin resistance of EOC cells and provide a potential target for EOC therapy.

Impaired expression of DICER and some microRNAs in HBZ expressing cells from acute adult T-cell leukemia patients

Global dysregulation of microRNAs (miRNAs), a class of non-coding RNAs that regulate genes expression, is a common feature of human tumors. Profiling of cellular miRNAs on Adult T cell Leukemia (ATL) cells by Yamagishi et al. showed a strong decrease in expression for 96.7% of cellular miRNAs in ATL cells. However, the mechanisms that regulate the expression of miRNAs in ATL cells are still largely unknown. In this study, we compared the expression of 12 miRs previously described for being overexpress by Tax and the expression of several key components of the miRNAs biogenesis pathways in different HBZ expressing cell lines as well as in primary CD4 (+) cells from acute ATL patients. We showed that the expression of miRNAs and Dicer1 were downregulated in cells lines expressing HBZ as well as in fresh CD4 (+) cells from acute ATL patients. Using qRT-PCR, western blotting analysis and Chromatin Immunoprecipitation, we showed that dicer transcription was regulated by c-Jun and JunD, two AP-1 transcription factors. We also demonstrated that HBZ affects the expression of Dicer by removing JunD from the proximal promoter. Furthermore, we showed that at therapeutic concentration of 1mM, Valproate (VPA) an HDAC inhibitors often used in cancer treatment, rescue Dicer expression and miRNAs maturation. These results might offer a rationale for clinical studies of new combined therapy in an effort to improve the outcome of patients with acute ATL.

Modulation of chemoresponsiveness to platinum-based agents by microRNAs in cancer

Ovarian cancer accounts for the highest mortality among all gynecologic cancers. Cytoreductive surgery followed by chemotherapy with a platinum-based agent (cisplatin or carboplatin) plus paclitaxel is the first-line option for treatment of epithelial ovarian cancer. However, primary or acquired resistance to platinum-based agents is a major clinical challenge. MicroRNAs are a group of small non-coding RNAs that regulate gene expression post-transcriptionally and may function as oncogenes or tumor-suppressor genes through extensive crosstalk with intracellular signaling pathways. Importantly, their dysregulation has been implicated in ovarian tumorigenesis. Pertinent to chemotherapy, increasing evidence has revealed that miRNAs can be directly linked to chemosensitivity to platinum-based agents in ovarian cancer. In this review, we summarize current evidence concerning the role of miRNAs in prediction and modulation of cellular responses to cisplatin and carboplatin in ovarian cancer.

Resistance to cancer chemotherapeutic drugs is determined by pivotal microRNA regulators

Chemo-resistance, which is the main obstacle in cancer therapy, is caused by the onset of drug-resistant cells in the heterogeneous cell population in cancer tissues. MicroRNAs regulate gene expression at the post-transcriptional level, and they are involved in many different biological processes, including cell proliferation, differentiation, metabolism, stress response, and apoptosis. The aberrant expression of microRNAs plays a major pathogenic role from the early stages of the carcinogenesis process. Recently, microRNAs have been reported to play an important role in inducing resistance to anti-cancer drugs. Specific microRNA alterations occur selectively in cancer cells, rendering these cells resistant to various chemotherapeutic agents. For example, resistance to 5-fluorouracil is mediated by alterations in miR-21, miR-27a/b, and miR-155; the sensitivity to Docetaxel is influenced by miR-98, miR-192, miR-194, miR-200b, miR-212, and miR-424; and the resistance to Cisplatin is mediated by miR-let-7, miR-15, miR-16 miR-21 and miR-214. Chemo-resistant cancer cells are characterized by altered functions in enzymes that are involved in microRNA maturation, primarily including Dicer, as demonstrated in ovarian cancer, oral squamous cell carcinoma, breast cancer and cervical cancer. Based on the evidence reviewed in this paper, various strategies have been developed to artificially re-establish microRNA expression in resistant cells, thus restoring chemo-sensitivity. These strategies employ synthetic analogs, anti-microRNA oligonucleotides, locked nucleic acid, microRNA sponges, drugs that inhibit DNA methylation or histone deacetylation, and the introduction of microRNA mimics. The ability to modulate microRNA expression is a promising strategy for overcoming the problem of drug resistance in cancer treatment.

Interactions between anticancer active platinum complexes and non-coding RNAs/microRNAs

Platinum(II) complexes such as cisplatin, carboplatin and oxaliplatin are clinically approved for the therapy of various solid tumors. Challenging pathogenic properties of cancer cells and the response of cancers towards platinum-based drugs are strongly influenced by non-coding small RNA molecules, the microRNAs (miRNAs). Both increased platinum activity and formation of tumor resistance towards platinum drugs are controlled by miRNAs. This review gives an overview of the interactions between platinum-based drugs and miRNAs, and their influence on platinum activity in various cancer types is discussed.

Depletion of Dicer promotes epithelial ovarian cancer progression by elevating PDIA3 expression

Dicer is an essential component of the microRNA (miRNA) processing machinery whose low expression is associated with advanced stage and poor clinical outcome in epithelial ovarian cancer. To investigate the functional relevance of Dicer in epithelial ovarian cancer and to identify its downstream effectors, two-dimensional gel electrophoresis combined with mass spectrometry was used for proteomic profiling. Dicer depletion promoted ovarian cancer cell proliferation and migration accompanied by a global upregulation of proteins. Twenty-six proteins, 7 upregulated and 19 downregulated, were identified. The functions of the identified proteins and their interactions were bioinformatically analyzed. Among them, protein disulfide-isomerase A3 (PDIA3) was considered to be a potential target protein of Dicer. PDIA3 repression by siRNA could significantly relieve the proliferation- and migration-promoting effect mediated by Dicer depletion in vitro and in vivo. Moreover, the miRNAs targeting PDIA3 were decreased in cells with Dicer depletion. In summary, low Dicer expression contributes to epithelial ovarian cancer progression by elevating PDIA3 expression.

Dicer Elicits Paclitaxel Chemosensitization and Suppresses Cancer Stemness in Breast Cancer by Repressing AXL

Paclitaxel is a standard-of-care chemotherapy for breast cancer, despite the increasing recognition of its poor effectiveness in the treatment of patients with advanced disease. Here, we report that adenovirus-type 5 E1A-mediated elevation of the miRNA-processing enzyme Dicer is sufficient to enhance paclitaxel sensitization and reduce cancer stem-like cell properties in this setting. Elevating Dicer expression increased levels of the AXL kinase targeting miRNA miR-494, thereby repressing AXL expression to increase paclitaxel sensitivity. We found that Dicer expression was regulated at the transcription level by E1A, through activation of an MAPK14/CEBPα pathway. Our findings define a mechanism of E1A-mediated chemosensitization for paclitaxel, which is based upon the suppression of breast cancer stem-like cells, with potential implications for the diagnosis and treatment of breast cancer patients. Cancer Res; 76(13); 3916-28. ©2016 AACR.

Prognostic significance of Dicer expression in hepatocellular carcinoma

Dicer is a RNaseIII endonuclease of the microRNA processing pathway, which is implicated in carcinogenesis of various types of human cancer. The present study assessed the expression level of Dicer in hepatocellular carcinoma (HCC) tissue to evaluate its association with HCC tumorigenesis. A low expression of Dicer was significantly associated with a shorter postoperative survival time of patients with HCC, which was assessed using the log-rank test with Kaplan-Meier survival analysis. Multivariate analysis identified that Dicer expression was an independent predictor for HCC outcome (relative risk, 0.660; 95% confidence interval, 0.506–0.861; P=0.002). A functional assay demonstrated that Dicer overexpression inhibited the proliferation and promoted the apoptosis of HCC cells. In addition, a Transwell assay revealed that Dicer markedly inhibited the migration and invasion of HCC cells. The present findings indicate that Dicer expression modified the outcomes of HCC patients by inhibiting proliferation, promoting apoptosis and inhibiting metastasis of HCC cells.

Dicer ablation promotes a mesenchymal and invasive phenotype in bladder cancer cells

Dicer expression is frequently altered in cancer and affects a wide array of cellular functions acting as an oncogene or tumor suppressor in varying contexts. It has been shown that Dicer expression is also deregulated in urothelial cell carcinoma of the bladder (UCCB) but the nature of this deregulation differs between reports. The aim of the present study was to gain a better understanding of the role of Dicer in bladder cancer to help determine its contribution to the disease. The results showed that Dicer transcript levels were decreased in UCCB tumor tissues as compared to normal tissues, suggesting that Dicer is a tumor suppressor. However, consistent with previous results, we demonstrated that knockdown of Dicer decreases cell viability and increases the induction of apoptosis, suggesting that Dicer is an oncogene. To resolve this discrepancy, we assessed the effects of decreased Dicer expression on epithelial-to‑mesenchymal transition, migration and invasion. We showed that decreased Dicer levels promoted a mesenchymal phenotype and increased migration. Additionally, the results showed that Dicer protein ablation leads to increased cell invasion, higher levels of matrix metalloproteinase-2, and decreased levels of key miRNAs shown to inhibit invasion. The results of this study suggest that decreased Dicer levels may portend a more malignant phenotype.

Genomic alterations as mediators of miRNA dysregulation in ovarian cancer

Ovarian cancer is the fifth most common cause of cancer death in women worldwide. Serous epithelial ovarian cancer (SEOC) is the most common and aggressive histological subtype. Widespread genomic alterations go hand-in-hand with aberrant DNA damage signaling and are a hallmark of high-grade SEOC. MicroRNAs (miRNAs) are a class of small noncoding RNA molecules that are nonrandomly distributed in the genome. They are frequently located in chromosomal regions susceptible to copy number variation (CNV) associated with malignancy that can influence their expression. Widespread changes in miRNA expression have been reported in multiple cancer types including ovarian cancer. This review examines CNV and single nucleotide polymorphisms, two common types of genomic alterations that occur in ovarian cancer, in the context of their influence on the expression of miRNA and the ability of miRNA to bind to and regulate their target genes. This includes genes encoding proteins involved in DNA repair and the maintenance of genomic stability. Improved understanding of mechanisms of miRNA dysregulation and the role of miRNA in ovarian cancer will provide further insight into the pathogenesis and treatment of this disease.

miR326 maturation is crucial for VEGF-C-driven cortactin expression and esophageal cancer progression

Esophageal cancer is an aggressive human malignancy with increasing incidence in the developed world. VEGF-C makes crucial contributions to esophageal cancer progression that are not well understood. Here, we report the discovery of regulatory relationship in esophageal cancers between the expression of VEGF-C and cortactin (CTTN), a regulator of the cortical actin cytoskeleton. Upregulation of CTTN expression by VEGF-C enhanced the invasive properties of esophageal squamous cell carcinoma in vitro and tumor metastasis in vivo. Mechanistic investigations showed that VEGF-C increased CTTN expression by downregulating Dicer-mediated maturation of miR326, thereby relieving the suppressive effect of miR326 on CTTN expression. Clinically, expression of Dicer and miR326 correlated with poor prognosis in patients with esophageal cancer. Our findings offer insights into how VEGF-C enhances the robust invasive and metastatic properties of esophageal cancer, which has potential implications for the development of new biomarkers or therapies in this setting.

Restoring TRAIL mediated signaling in ovarian cancer cells

Ovarian cancer has emerged as a multifaceted and genomically complex disease. Genetic/epigenetic mutations, suppression of tumor suppressors, overexpression of oncogenes, rewiring of intracellular signaling cascades and loss of apoptosis are some of the deeply studied mechanisms. In vitro and in vivo studies have highlighted different molecular mechanisms that regulate tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) mediated apoptosis in ovarian cancer. In this review, we bring to limelight, expansion in understanding systematical characterization of ovarian cancer cells has led to the rapid development of new drugs and treatments to target negative regulators of TRAIL mediated signaling pathway. Wide ranging synthetic and natural agents have been shown to stimulate mRNA and protein expression of death receptors. This review is compartmentalized into programmed cell death protein 4, platelet-derived growth factor signaling and miRNA control of TRAIL mediated signaling to ovarian cancer. Mapatumumab and PRO95780 have been tested for efficacy against ovarian cancer. Use of high-throughput screening assays will aid in dissecting the heterogeneity of this disease and increasing a long-term survival which might be achieved by translating rapidly accumulating information obtained from molecular and cellular studies to clinic researches.

MicroRNAs in cancer: biomarkers, functions and therapy

The emergence of microRNAs has been one of the defining developments in cancer biology over the past decade, and the explosion of knowledge in this area has brought forward new diagnostic and therapeutic opportunities. The importance of microRNAs in cancer has been underlined by the identification of alterations in microRNA target binding sites and the microRNA processing machinery in tumor cells. Clinical trials utilizing microRNA profiling for patient prognosis and clinical response are now underway, and the first microRNA mimic entered the clinic for cancer therapy in 2013. In this article we review the potential applications of microRNAs for the clinical assessment of patient outcome in cancer, as well as in cancer monitoring and therapy.

MicroRNA Machinery Genes as Novel Biomarkers for Cancer

MicroRNAs (miRNAs) directly and indirectly affect tumorigenesis. To be able to perform their myriad roles, miRNA machinery genes, such as Drosha, DGCR8, Dicer1, XPO5, TRBP, and AGO2, must generate precise miRNAs. These genes have specific expression patterns, protein-binding partners, and biochemical capabilities in different cancers. Our preliminary analysis of data from The Cancer Genome Atlas consortium on multiple types of cancer revealed significant alterations in these miRNA machinery genes. Here, we review their biological structures and functions with an eye toward understanding how they could serve as cancer biomarkers.

Micro-RNAs and ovarian cancer: the state of art and perspectives of clinical research

Dysregulation of microRNA (mi-RNA) expression plays a major role in the development and progression of most human malignancies. Members of the miR-200 family, miR-182, miR-214 and miR-221 are frequently up-regulated, whereas miR-100, let-7i, miR-199a, miR-125b, mir-145 and miR-335 are often down-regulated in ovarian cancer compared with normal ovarian tissue. Most mi-RNA signatures are overlapping in different tumor histotypes but some mi-RNAs seem to be histotype specific. For instance, the endometrioid type shares with the serous and clear cell types the up-regulation of miR-200 family members, but also presents over-expression of miR-21, miR-202 and miR-205. Clear cell carcinoma has a significantly higher expression of miR-30a and miR-30a*, whereas mucinous histotype has elevated levels of miR-192/194. In vitro and in vivo investigations have shown that several mi-RNAs can modulate the sensitivity of ovarian cancer to platinum and taxane, and clinical studies have suggested that mi-RNA profiling may predict the outcome of patients with this malignancy. Some mi-RNAs could be used as biomarkers to identify patients that might benefit from the addition of molecularly targeted agents (i.e. anti-angiogenic agents, MET inhibitors and poly(ADP-ribose) polymerase (PARP) inhibitors) to standard chemotherapy. Moreover, mi-RNAs could represent potential targets for the development of novel therapies.

Genetically engineered mouse models for epithelial ovarian cancer: are we there yet?

The development of preclinical spontaneous genetically engineered mouse models (GEMMs) requires an understanding of the genetic basis of the human disease. Such robust models have proven invaluable for increasing understanding of human malignancies as well as identifying new biomarkers and testing new therapies for these diseases. While GEMMs have been reported for ovarian cancer, the majority have proven disappointing overall in their recapitulation of paired genetic and histological features especially for serous ovarian epithelial cancer. This review describes GEMMs for ovarian cancer, in particular, high grade serous ovarian cancer and assesses these in light of recent changes in our understanding of the human malignancy.

Mutant p53 regulates Dicer through p63-dependent and -independent mechanisms to promote an invasive phenotype

The control and processing of microRNAs (miRs) is critical in the regulation of all cellular responses. Previous studies have suggested that a reduction in the expression of certain miRs, or an overall decrease in miR processing through the partial depletion of Dicer, can promote enhanced metastatic potential. We show here that Dicer depletion can promote the invasive behavior of cells that is reflected in enhanced recycling and activation of the growth factor receptors Met and EGF receptor. These responses are also seen in response to the expression of tumor-derived mutant p53s, and we show that mutant p53 can down-regulate Dicer expression through both direct inhibition of the TAp63-mediated transcriptional activation of Dicer and a TAp63-independent control of Dicer protein expression. Our results delineate a clear relationship between mutant p53, TAp63, and Dicer that might contribute to the metastatic function of mutant p53 but, interestingly, also reveal TAp63-independent functions of mutant p53 in controlling Dicer activity.

A low Dicer expression is associated with resistance to 5-FU-based chemoradiotherapy and a shorter overall survival in patients with oral squamous cell carcinoma

BACKGROUND

The deregulation of microRNA (miRNA) is associated with multiple processes involved in cancer progression. RNase III endonucleases, Dicer and Drosha, are key enzymes for miRNA biogenesis, and it has been reported that altered expressions of these molecules affect the clinical outcomes of patients with various cancers. However, the clinical value of measuring the levels of Dicer and Drosha in oral squamous cell carcinoma (OSCC) patients is unclear. The purpose of this study was to determine the clinical significance of the expressions of Dicer and Drosha in patients with OSCC.

METHODS

Oral squamous cell carcinoma specimens were obtained from 61 patients who underwent surgery following 5-fluorouracil-based chemoradiotherapy at Kumamoto University Hospital between October 2003 and January 2009. Paraffin-embedded sections obtained from biopsy specimens were immunohistochemically analyzed. The associations between Dicer, Drosha, and various clinicopathological features were examined, and the effects of Dicer and Drosha on the prognosis were evaluated.

RESULTS

A low Dicer tumor expression was significantly correlated with the pathological response to chemoradiotherapy. Furthermore, a Cox regression analysis based on the overall survival revealed the Dicer expression status (hazard ratio, 0.34; P = 0.048) and pathological response to chemoradiotherapy (hazard ratio, 0.21; P = 0.014) to be significant prognostic factors in OSCC patients. On the other hand, the Drosha expression was not associated with any clinicopathological features or the prognosis.

CONCLUSION

These results suggest that Dicer is a potential biomarker for predicting the clinical response to 5-FU-based chemoradiotherapy and the overall survival in patients with OSCC.

VX680 suppresses the growth of HepG2 cells and enhances the chemosensitivity to cisplatin

VX680 is an Aurora A inhibitor. It has been reported to inhibit the growth of the HepG2 cell line in several studies. However, whether it enhances chemosensitivity to cisplatin remains unclear. In this study, the synergistic effect of VX680 and cisplatin on the proliferation of HepG2 cells was determined by MTT assay. The changes in cell apoptosis were detected by flow cytometry. Aurora A, Bcl-2 and p53 protein levels were analyzed by western blotting. This study demonstrated that VX680, cisplatin and a combination of the two inhibit the growth of HepG2 cells in a dose- and time-dependent manner. A synergistic effect was observed with the combined therapy. Moreover, the inhibitory effect of VX680 was positively correlated with the expression of Aurora A. The rate of apoptosis in the combined group was significantly higher compared with that of the VX680 and cisplatin groups. In addition, VX680 and cisplatin increased the expression of the p53 protein. Cisplatin reduced the expression of Bcl-2 protein, while VX680 did not. In the combined group, the expression of Bcl-2 and p53 changed significantly compared with the single drug group and control group. This study suggests that Aurora A may represent a valid target in hepatocellular carcinoma. We also demonstrated that the Aurora A inhibitor VX680 has a synergistic effect with cisplatin.