Drug resistance-related microRNAs in hematological malignancies: Translating basic evidence into therapeutic strategies

Unveiling the role of GAS41 in cancer progression

GAS41, a member of the human YEATS domain family, plays a pivotal role in human cancer development. It serves as a highly promising epigenetic reader, facilitating precise regulation of cell growth and development by recognizing essential histone modifications, including histone acetylation, benzoylation, succinylation, and crotonylation. Functional readouts of these histone modifications often coincide with cancer progression. In addition, GAS41 functions as a novel oncogene, participating in numerous signaling pathways. Here, we summarize the epigenetic functions of GAS41 and its role in the carcinoma progression. Moving forward, elucidating the downstream target oncogenes regulated by GAS41 and the developing small molecule inhibitors based on the distinctive YEATS recognition properties will be pivotal in advancing this research field.

Combating Drug Resistance by Exploiting miRNA-200c-Controlled Phase II Detoxification

Acquired drug resistance constitutes a serious obstacle to the successful therapy of cancer. In the process of therapy resistance, microRNAs can play important roles. In order to combat resistance formation and to improve the efficacy of chemotherapeutics, the mechanisms of the multifaceted hsa-miR-200c on drug resistance were elucidated. Upon knockout of hsa-miR-200c in breast carcinoma cells, a proteomic approach identified altered expression of glutathione S-transferases (GSTs) when cells were treated with the chemotherapeutic drug doxorubicin. In different hsa-miR-200c expression systems, such as knockout, inducible sponge and inducible overexpression, the differential expression of all members of the GST family was evaluated. Expression of hsa-miR-200c in cancer cells led to the repression of a multitude of these GSTs and as consequence, enhanced drug-induced tumor cell death which was evaluated for two chemotherapeutic drugs. Additionally, the influence of hsa-miR-200c on the glutathione pathway, which is part of the phase II detoxification mechanism, was investigated. Finally, the long-term effects of hsa-miR-200c on drug efficacy were studied in vitro and in vivo. Upon doxycycline induction of hsa-miR-200c, MDA-MB 231 xenograft mouse models revealed a strongly reduced tumor growth and an enhanced treatment response to doxorubicin. A combined treatment of these tumors with hsa-miR-200c and doxorubicin resulted in complete regression of the tumor in 60% of the animals. These results identify hsa-miR-200c as an important player regulating the cellular phase II detoxification, thus sensitizing cancer cells not expressing this microRNA to chemotherapeutics and reversing drug resistance through suppression of GSTs.

Alterations in microRNA Expression during Hematopoietic Stem Cell Mobilization

Simple Summary

Lymphoproliferative disorders comprise a heterogeneous group of hematological malignancies characterized by abnormal lymphocyte proliferation. Autologous hematopoietic stem cell transplantation plays a very important role in the treatment of lymphoproliferative diseases. The key element in this process is the effective mobilization of hematopoietic cells from the marrow niche to the peripheral blood. Mobilization of HSC is regulated by many factors, out of which miRNAs present in the hematopoietic niche via targeting cytokines, and signaling pathways may play an important regulatory role. This study investigated the expression of selected miRNAs in patients with multiple myeloma, Hodgkin’s lymphomas, and non-Hodgkin’s lymphomas undergoing mobilization procedures. The aim of the study was to evaluate the expression of hsa-miR-15a-5p, hsa-miR-16-5p, hsa-miR-34a-5p, hsa-miR-126-3p, hsa-miR-146a-5p, hsa-miR-155-5p, and hsa-miR-223-3p during the mobilization procedure, and to assess their role in mobilization efficacy. The level of miRNAs was tested at two time points before the initiation of mobilization and on the day of the first apheresis. Our results suggest that the investigated miRNAs, especially hsa-miR-146a-5p, may influence the efficacy of HSC mobilization.

Abstract

microRNAs play an important role in the regulation of gene expression, cell fate, hematopoiesis, and may influence the efficacy of CD34+ cell mobilization. The present study examines the role of hsa-miR-15a-5p, hsa-miR-16-5p, hsa-miR-34a-5p, hsa-miR-126-3p, hsa-miR-146a-5p, hsa-miR-155-5p, and hsa-miR-223-3p in the course of hematopoietic stem cell mobilization. The numbers of CD34+ cells collected in patients with hematological malignancies (39 multiple myelomas, 11 lymphomas) were determined during mobilization for an autologous hematopoietic stem cell transplantation. The miRNA level was evaluated by RT-PCR. Compared to baseline, a significant decline in hsa-miR-15a-5p, hsa-miR-16-5p, hsa-miR-126-3p, hsa-miR-146a-5p, and hsa-miR-155-5p was observed on the day of the first apheresis (day A). An increase was observed only in the expression of hsa-miR-34a-5p. On day A, a negative correlation was found between hsa-miR-15a-5p and hsa-miR-146a-5p levels and the number of CD34+ cells in peripheral blood. A negative correlation was observed between hsa-miR-146a-5p and the number of collected CD34+ cells after the first apheresis. Good mobilizers, defined according to GITMO criteria, demonstrated a lower hsa-miR-146a-5p level on day A than poor mobilizers. Patients from the hsa-miR-146a-5p “low expressors” collected more CD34+ cells than “high expressors”. Our results suggest that the investigated miRNAs, especially hsa-miR-146a-5p, may influence the efficacy of HSC mobilization.

CARD11 is a novel target of miR-181b that is upregulated in chronic lymphocytic leukemia

Aim: To investigate the targets of miR-181b in patients with chronic lymphocytic leukemia (CLL). Materials & methods: The bioinformatic softwares were used to indicate the key target genes associated with miR-181b, and the results were verified in CLL patient samples and 293T cells. Results: CARD11 is a potential target gene of miR-181b, an inverse relationship was revealed between the expression of CARD11 and miR-181b in 104 CLL patients, and it was confirmed in vitro with luciferase assays and western blotting. Kaplan-Meier analysis showed that CLL patients with high CARD11 expression demonstrated poor survival. Conclusion: CARD11 is a novel target of miR-181b that is upregulated, which could be a poor prognostic indicator for CLL patients.

miRNAs mediated drug resistance in hematological malignancies

Despite improvements in the therapeutic approaches for hematological malignancies in the last decades, refractory disease still occurs, and cancer drug resistance still remains a major hurdle in the clinical management of these cancer patients. The investigation of this problem has been extensive and different mechanism and molecules have been associated with drug resistance. MicroRNAs (miRNAs) have been described as having an important action in the emergence of cancer, including hematological tumors, and as being major players in their progression, aggressiveness and response to treatments. Moreover, miRNAs have been strongly associated with cancer drug resistance and with the modulation of the sensitivity of cancer cells to a wide array of anticancer drugs. Furthermore, this role has also been reported for miRNAs packaged into extracellular vesicles (EVs-miRNAs), which in turn have been described as essential for the horizontal transfer of drug resistance to sensitive cells. Several studies have been suggesting the use of miRNAs as biomarkers for drug response and clinical outcome prediction, as well as promising therapeutic tools in hematological diseases. Indeed, the combination of miRNA-based therapeutic tools with conventional drugs contributes to overcome drug resistance. This review addresses the role of miRNAs in the pathogenesis of hematological malignances, namely multiple myeloma, leukemias and lymphomas, highlighting their important action (either in their cell-free circulating form or within circulating EVs) in drug resistance and their potential clinical applications.

MicroRNA‑22 regulates autophagy and apoptosis in cisplatin resistance of osteosarcoma

Osteosarcoma (OS) is a primary malignant tumor of bone tissue. Effective chemotherapy may improve the survival of patients with OS. MicroRNAs (miRs) serve significant roles in the regulatory function of tumorigenesis and chemosensitivity of different types of cancer. miR‑22 has been revealed to inhibit the proliferation and migration of OS cells, as well as increasing their sensitivity to cisplatin (CDDP). The mechanisms of action behind the functions of miR‑22 in OS drug resistance require investigation. Therefore, in the present study, the human OS cell lines (MG‑63, U2OS, Saos2 and OS9901) and a drug‑resistant cell line (MG‑63/CDDP) were cultured. Cell proliferation, apoptosis and autophagy assays were performed to investigate the proliferation, apoptosis and autophagy of cell lines transfected with miR‑22 mimic. Reverse transcription‑quantitative polymerase chain reaction and western blot analysis were performed to investigate the expression levels of associated genes. The results revealed that miR‑22 inhibited the proliferation of MG‑63 cells and MG‑63/CDDP cells, and enhanced the anti‑proliferative ability of CDDP. miR‑22 induced apoptosis and inhibited autophagy of MG‑63 cells and MG‑63/CDDP cells. Apoptosis‑related genes, including caspase‑3 and Bcl‑2‑associated X protein were upregulated, while B‑cell lymphoma‑2 was downregulated in both cell lines transfected with the miR‑22 mimic. Autophagy protein 5, beclin1 and microtubules‑associated protein 1 light chain 3 were downregulated in both cell lines transfected with miR‑22 mimic. Furthermore, the in vitro and in vivo expression levels of metadherin (MTDH) in the OS/OS‑CDDP‑resistant models were downregulated following transfection with the miR‑22 mimic. Therefore, the results of the present study suggested that miR‑22 promoted CDDP sensitivity by inhibiting autophagy and inducing apoptosis in OS cells, while MTDH may serve a positive role in inducing CDDP resistance of OS cells.

LncRNA FENDRR attenuates adriamycin resistance via suppressing MDR1 expression through sponging HuR and miR-184 in chronic myelogenous leukaemia cells

Chemotherapy is a major anticancer therapeutic modality, however, multidrug resistance (MDR) is frequently observed and hinders treatment efficacy. Here, we investigated the role and potential mechanism of the long noncoding RNA (lncRNA) FENDRR in adriamycin resistance of chronic myeloid leukaemia (CML) cells. FENDRR overexpression attenuates adriamycin resistance, as shown by increased Rhodamine 123 accumulation, promotion of cell apoptosis in vitro and suppression of tumour growth in vivo. Mechanistically, we identified that FENDRR reduces the interaction of the RNA-binding protein HuR with MDR1 via acting as a sponge, and miR-184 competitively binds to FENDRR with HuR. Thus, the HuR/FENDRR/miR-184 interaction contributes to MDR1 activity. These findings indicate that FENDRR is a potential target for reversing adriamycin resistance.

Drug resistance-related microRNAs in osteosarcoma: Translating basic evidence into therapeutic strategies

Although the application of multiple chemotherapy brought revolutionary changes to improve overall survival of osteosarcoma patients, the existence of multidrug resistance (MDR) has become a great challenge for successful osteosarcoma treatment in recent decades. Substantial studies have revealed various underlying mechanisms of MDR in cancers. As for osteosarcoma, evidence has highlighted that microRNAs (miRNAs) can mediate in the processes of DNA damage response, apoptosis avoidance, autophagy induction, activation of cancer stem cells, and signal transduction. Besides, these drug resistance‐related miRNAs showed much promise for serving as candidates for predictive biomarkers of poor outcomes and shorter survival time, and therapeutic targets to reverse drug resistance and overcome treatment refractoriness. This review aims to demonstrate the potential molecular mechanisms of miRNAs‐regulated drug resistance in osteosarcoma, and provide insight in translating basic evidence into therapeutic strategies.

miR-221/222-Mediated Inhibition of Autophagy Promotes Dexamethasone Resistance in Multiple Myeloma

Inherent or acquired resistance to chemotherapeutic drugs is still an obstacle for the treatment of multiple myeloma (MM). MicroRNA dysregulation is related to the development of chemoresistance in cancers. However, its role in chemoresistance of MM is largely unknown. Here we demonstrated that miR-221/222 were upregulated in plasma cells from patients with MM, especially those with relapsed or refractory disease. Moreover, expression levels of miR-221/222 were inversely correlated with dexamethasone (Dex) sensitivity of human MM cell lines. Importantly, we found that Dex induced pro-death autophagy in MM cells and the inhibition of autophagy significantly decreased Dex-induced cell death. Mechanistically, autophagy-related gene 12 (ATG12) was identified as a novel target gene of miR-221/222, and miR-221/222 overexpression inhibited autophagy by directly targeting ATG12 and the p27^kip (p27)-mammalian target of rapamycin (mTOR) pathway. Indeed, Dex treatment decreased the expression of miR-221/222, thereby activating the ATG12/p27-mTOR autophagy-regulatory axis and inducing cell death in Dex-sensitive MM cells. Furthermore, both in vitro and in vivo results showed that the inhibitions of miR-221/222 increased the expression of ATG12 and p27 and functionally induced extended autophagy and cell death of MM cells. In conclusion, our findings demonstrated the crucial role of the miR-221/222-ATG12/p27-mTOR autophagy-regulatory axis in Dex resistance of MM, and they suggest potential prediction and treatment strategies for glucocorticoid resistance.

miRNA-15a, miRNA-16, miRNA-126, miRNA-146a, and miRNA-223 expressions in autologous hematopoietic stem cell transplantation and their impact on engraftment

OBJECTIVE

MicroRNAs engaged in angiogenesis and hematopoiesis can influence hematopoietic stem cells (HSCs) homing after transplantation by targeting bone marrow niche microenvironment. This study aimed to examine the kinetics of miRNA-15a, miRNA-16, miRNA-126, miRNA-146a, and miRNA-223 in autologous HSC transplantation settings.

METHODS

The study comprised of 51 patients with hematological malignancies (42 multiple myeloma, 9 lymphoma). Samples were taken at four time points: before conditioning, after chemotherapy but prior to autologous HSC transplantation (day 0), on day +7, and +14 days after HSCT. The miRNA levels were evaluated by the real-time PCR method.

RESULTS

A significant, steady decline of all tested microRNAs in the course of transplantation, as compared to the baseline, was found. The study revealed that higher levels of miRNA-15a, miRNA-16, miRNA-126, and miRNA-146a on day 0 correlated with longer time to engraftment. Additionally, a positive correlation between the levels of miRNA-15a, miRNA-146a, and miRNA-223 assessed on day +7 and the time to engraftment was observed.

CONCLUSIONS

In conclusion, all investigated microRNAs changed significantly in the course of transplantation. Our results suggest that the miRNAs may participate in hematopoietic recovery in the early post-transplant period and influence engraftment efficiency after HSCT.

Molecular mechanisms and theranostic potential of miRNAs in drug resistance of gastric cancer

INTRODUCTION

Systemic chemotherapy is a curative approach to inhibit gastric cancer cells proliferation. Despite the great progress in anti-cancer treatment achieved during the last decades, drug resistance and treatment refractoriness still extensively persists. Recently, accumulating studies have highlighted the role of miRNAs in drug resistance of gastric cancers by modulating some drug resistance-related proteins and genes expression. Pre-clinical reports indicate that miRNAs might serve as ideal biomarkers and potential targets, thus holding great promise for developing targeted therapy and personalized treatment for the patients with gastric cancer. Areas covered: This review provide a comprehensive overview of the current advances of miRNAs and molecular mechanisms underlying miRNA-mediated drug resistance in gastric cancer. We particularly focus on the potential values of drug resistance-related miRNAs as biomarkers and novel targets in gastric cancer therapy and envisage the future research developments of these miRNAs and challenges in translating the new findings into clinical applications. Expert opinion: Although the concrete mechanisms of miRNAs in drug resistance of gastric cancer have not been fully clarified, miRNA may be a promising theranostic approach. Further studies are still needed to facilitate the clinical applications of miRNAs in drug resistant gastric cancer.

Decreased expression of miR-939 contributes to chemoresistance and metastasis of gastric cancer via dysregulation of SLC34A2 and Raf/MEK/ERK pathway

BACKGROUND

The development of chemoresistance and metastasis are the leading causes of death for gastric cancer (GC) patients, however, the molecular mechanisms involved remain unclear. Dysregulation of miRNAs is associated with a variety of disease, including GC. Recently, microarray profiling analysis revealed that miR-939 was dysregulated in human GC samples, but the role of miR-939 in GC has not been intensively investigated.

METHODS

In the present study, we firstly examined the expression pattern of miR-939 in two independent cohorts of clinical GC samples: one cohort of 112 GC patients with stage I-III disease who underwent surgery followed by adjuvant chemotherapy; and another cohort of 110 GC patients with stage IV disease who received palliative chemotherapy. A series of in vivo and in vitro assays were then performed to investigate the function of miR-939 in GC.

RESULTS

We detected that reduced expression of miR-939 was associated with chemoresistance and increased risk of tumor recurrence in GC patients. Further function study demonstrated that overexpression of miR-939 suppressed GC cell growth, and enhanced 5-fluorouracil-induced chemosensitivity by compromising cellular growth and inducing apoptosis in vitro and in vivo. Moreover, miR-939 repressed the migration and invasion of GC cells in vitro, and diminished the occurrence of lung metastasis in vivo. We further identified solute carrier family 34 member 2 (SLC34A2) was a novel target of miR-939. Mechanistically, we elucidated that miR-939 exerted its function mainly through inhibiting SLC34A2/Raf/MEK/ERK pathway, which is activated in GC. Multivariate analysis identified miR-939, SLC34A2, and their combination as independent indicators for poor prognosis and tumor recurrence in GC patients.

CONCLUSION

Our data indicate that miR-939 acts as a tumor suppressor miRNA in GC, and miR-939/SLC34A2 axis represents a novel therapeutic strategy for future GC treatment.

MicroRNA-146a affects the chemotherapeutic sensitivity and prognosis of advanced gastric cancer through the regulation of LIN52

The present study aimed to evaluate the correlation between the expression of microRNA-146a (miR-146a) and its target gene, LIN52, in advanced gastric cancer, and determine their potential effects on chemotherapeutic sensitivity and prognosis. Total RNA was extracted from 93 tissue samples of advanced gastric cancer and corresponding adjacent non-tumor tissues to quantify the relative expression levels of miR-146a using reverse transcription-quantitative polymerase chain reaction analysis. The expression of LIN52 was detected in tumors and normal tissues using immunohistochemical analysis. Correlation analysis was performed to assess the correlation between the expression of miR-146a and LIN52 and clinicopathological parameters of gastric cancer, including clinical diagnostic specificity, clinical tumor-necrosis-metastasis staging, lymph node metastasis, differentiation grade, chemotherapeutic sensitivity and prognosis. The expression of miR-146a in advanced gastric cancer tissues was lower, compared with that in the adjacent non-tumor tissues, and was negatively correlated with lymph node metastasis (P<0.05). Gastric cancer tissues with a low expression level of miR146a exhibited an increased expression level of LIN52 (P<0.05). Receiver operating characteristic curve regression analysis showed that miR-146a had 98% sensitivity in distinguishing gastric cancer tissues and adjacent non-tumor tissues. A high expression of miR-146a in gastric cancer was associated with improved treatment efficacy in patients. The chemotherapeutic sensitivity of patients with tumors expressing high levels of miR-146a was significantly higher, compared with that of patients with tumors expressing low levels of miR-146a (P<0.05). The expression of miR-146a was low in advanced gastric cancer tissues. As a tumor suppressor gene in advanced gastric cancer, miR-146a had a significant negative correlation with LIN52. High expression levels of miR-146a in advanced gastric cancer tissue may be associated with improved treatment efficacy of chemotherapy, suggesting that miR-146a may be a molecular marker for the diagnosis, prediction of treatment efficacy and prognosis of advanced gastric cancer.

Downregulation of YEATS4 by miR-218 sensitizes colorectal cancer cells to L-OHP-induced cell apoptosis by inhibiting cytoprotective autophagy

Colorectal cancer (CRC) is a leading cause of cancer-related death worldwide. Deregulation of microRNAs (miRNAs) has been reported to participate in CRC progression. In the present study, we observed downregulation of miR-218 and upregulation of YEATS domain containing 4 (YEATS4) in CRC tissues and in multidrug-resistant HCT-116/L-OHP cells compared with these levels in normal tissues and parental HCT-116 cells, respectively. The results indicated that miR-218 overexpression significantly decreased the IC50 value of oxaliplatin (L-OHP) in the HCT-116/L-OHP cells, and suppression of miR-218 significantly enhanced the IC50 of L-OHP in the HCT-116 cells. Flow cytometric analysis showed that miR-218 overexpression alone promoted cell apoptosis in the HCT-116/L-OHP cells, which was further enhanced in response to L-OHP, and miR-218 inhibition decreased cell apoptosis in the HCT-116 cells following treatment with L-OHP. Western blot analysis indicated that, compared with the small increase observed in HCT-116 cells, the relative LC3 II level in HCT-116/L-OHP cells after lysosome inhibition via chloroquine (CQ) was markedly upregulated following L-OHP treatment, suggesting induction of autophagy. Exposure of HCT-116/L-OHP cells to L-OHP after control mimic transfection increased autophagic flux, as reflected by increased LC3 II levels, while miR-218 overexpression partly reversed L-OHP-mediated LC3 II accumulation. Additionally, both miR-218 overexpression and CQ treatment promoted L-OHP-induced HCT-116/L-OHP cell apoptosis. Molecularly, our results confirmed that miR-218 directly targets the YEATS4 gene and inhibits YEATS4 expression. Furthermore, YEATS4 overexpression without the 3'-untranslated region (3'-UTR) restored miR-218-inhibited YEATS4 and LC3 II expression, and abolished miR-218-stimulated cell viability loss and cell apoptosis increase in response to L-OHP. In conclusion, miR-218 sensitized HCT-116/L-OHP cells to L-OHP-induced cell apoptosis via inhibition of cytoprotective autophagy by targeting YEATS4 expression.

Loss of MiR-424-3p, not miR-424-5p, confers chemoresistance through targeting YAP1 in non-small cell lung cancer

MiR-424 has been discovered to be involved in the chemoresistance of lung cancer. However, the underlying mechanism by which miR-424 played role in chemoresistance has been unknown. Here, in our study, to investigate the role of miR-424 in non-small cell lung cancer (NSCLC), we have detected the expression of miR-424-3p and -5p in NSCLC tissues and paired normal control. Moreover, to explore the role of miR-424-3p in NSCLC cells, miR-424-3p and -5p were both re-expressed and knocked down using transient transfection with their respective mimics and inhibitors. Cell viability, migration, and invasion were evaluated using MTT, wound-healing and Transwell assays, respectively. It was found that down-regulation of miR-424-3p was pronouncedly associated with NSCLC progression and overall prognosis; and that both miR-424-3p and -5p were markedly capable of preventing the proliferation, migration, and invasion in NSCLC cells. Additionally, it is miR-424-3p but not miR-424-5p that enhances the chemo-sensitivity of NSCLC cells through targeting YAP1. Mechanistically, YAP1 was identified as down-stream target of miR-424-3p. Together, it was for the first time in our study found that it is loss of miR-424-3p not miR-424-5p that enables chemoresistance through targeting YAP1 in NSCLC, supporting that miR-424-3p could be used as therapeutic target in the curing of NSCLC with chemoresistance. © 2016 Wiley Periodicals, Inc.

Mechanisms of Drug Resistance in Relapse and Refractory Multiple Myeloma

Multiple myeloma (MM) is a hematological malignancy that remains incurable because most patients eventually relapse or become refractory to current treatments. Although the treatments have improved, the major problem in MM is resistance to therapy. Clonal evolution of MM cells and bone marrow microenvironment changes contribute to drug resistance. Some mechanisms affect both MM cells and microenvironment, including the up- and downregulation of microRNAs and programmed death factor 1 (PD-1)/PD-L1 interaction. Here, we review the pathogenesis of MM cells and bone marrow microenvironment and highlight possible drug resistance mechanisms. We also review a potential molecular targeting treatment and immunotherapy for patients with refractory or relapse MM.

MicroRNA-494 sensitizes colon cancer cells to fluorouracil through regulation of DPYD

Chemoresistance of colon cancer cells to the chemotherapeutics is still a main obstacle in treatment of this malignancy. The microRNA (miRNA) mediated chemosensitivity regulation in colon cancer cells is still largely unknown. Here we constructed a fluorouracil (5-Fu) resistant SW480 cell line (SW480/5-Fu) and discovered that miRNA miR-494 was down-regulated in the drug resistant cells compared with the parental cells. miR-494 level was found to be correlated with 5-Fu sensitivity in colon cancer cells, and artificial alteration of miR-494 affects the sensitivity of colon cancer cell lines to 5-Fu. miR-494 also promoted apoptosis of colon cancer cells at present of 5-Fu. Importantly, as a regulatory enzyme in the 5-Fu catabolic pathway, DPYD was confirmed to be a direct target of miR-494 through the interaction of miR-494 and its binding site within DPYD 3' untranslated region (3'UTR). miR-494 also negatively regulated endogenous DPYD expression in SW480 cells. Overexpression or knockdown of DPYD could attenuate miR-494 mediated 5-Fu sensitivity regulation, suggesting the dependence of DPYD regulation in miR-494 activity. miR-494 inhibited SW480/5-Fu derived xenograft tumors growth in vivo at present of 5-Fu. Thus, we concluded that in colon cancer cells, tumor suppressor miR-494 enhanced 5-Fu sensitivity via regulation of DPYD expression.

MiR-26a enhances the sensitivity of gastric cancer cells to cisplatin by targeting NRAS and E2F2

BACKGROUND/AIMS

MiR-26a has been identified as a tumor suppressor in various tumors, but the relationship between miR-26a and the sensitivity of gastric cancer to chemotherapies has not been established. The present study was performed to investigate the effect of miR-26a on drug sensitivity in gastric cancer (GC).

MATERIALS AND METHODS

The expression level of miRNA-26a in cisplatin-resistant SGC-7901/DDP cells and parent SGC-7901 cells was evaluated by qRT-PCR. The effect of miR-26a on sensitivity of GC cells to cisplatin was assayed using MTS method. The effect of miR-26a on cisplatin-induced apoptosis were determined by Annexin V/propidium iodide (PI) double staining method and flow cytometry. The targets of miR-26a were identified using a luciferase activity assay and miR-26a-mediated target genes expression analysis. Furthermore, the role of the targets neuroblastoma RAS viral (v-ras) oncogene homolog (NRAS) and E2F2 on sensitivity of chemotherapy in GC by MTS and apoptotic cell analysis was assessed.

RESULTS

We found that miR-26a was downregulated in cisplatin-resistant SGC-7901/DDP cells compared with SGC-7901 cells. Using both gain- and loss-of-function analyses, we further revealed that miR-26a could improve the sensitivity of GC cells to cisplatin. Furthermore, miR-26a has target sites in the 3'-UTR of NRAS and E2F2 by luciferase reporter assay and reduces the expression levels of NRAS and E2F2. In addition, knockdown of NRAS or E2F2 sensitize GC cells to cisplatin.

CONCLUSION

Our results suggest that miR-26a can improve the sensitivity of GC cells to cisplatin-based chemotherapies through targeting NRAS and E2F2, and provide the first evidence of the potential utility of miR-26a as a sensitizer in chemotherapy for GC.