A tumor-suppressive microRNA, miR-504, inhibits cell proliferation and promotes apoptosis by targeting FOXP1 in human glioma

MiR-504-3p Has Tumor-Suppressing Activity and Decreases IFITM1 Expression in Non-Small Cell Lung Cancer Cells

Objective: To analyze the impact of expression of miR-504-3p on the proliferation, migration, cell cycle transit and rate of apoptosis of NSCLC cells and explore the underlying mechanisms. Methods: The Cancer Genome Atlas (TCGA) database was used to compare the expression levels of miR-504 between NSCLC tissues and normal lung tissues. NSCLC cells were transfected with lentiviral vectors that either overexpressed or knocked down miR-504-3p to evaluate its effects on NSCLC biological behavior. Quantitative Real Time Polymerase Chain Reaction was used to measure the levels of miR-504-3p and Interferon-Induced Transmembrane Protein 1 (IFITM1). A luciferase reporter array was used to reveal whether miR-504-3p directly targets IFITM1. Results: The expression of miR-504 was significantly down-regulated in lung cancer tissues compared to normal lung tissues. Overexpression of miR-504-3p in NSCLC cell lines inhibited cell proliferation, migration and promoted cell apoptosis. Meanwhile, changes in the expression level of miR-504-3p had no significant effect on NSCLC cell cycle progression. Moreover, over-expressed miR-504-3p following its transfection significantly decreased the expression of IFITM1 in NSCLC cell lines and suppressed the activity of the luciferase reporter containing wild type but not mutant IFITM1 3' -UTR. Conclusion: miR-504-3p inhibits cell proliferation and migration and promotes cell apoptosis in NSCLC cells. MiR-504-3p decreases IFITM1 expression in NSCLC cells, which may be a potential mechanism of its tumor-suppressive functions in NSCLC.

Pan-Cancer Analysis Reveals Common and Specific Relationships between Intragenic miRNAs and Their Host Genes

MicroRNAs (miRNAs) are small endogenous non-coding RNAs that play important roles in regulating gene expression. Most miRNAs are located within or close to genes (host). miRNAs and their host genes have either coordinated or independent transcription. We performed a comprehensive investigation on co-transcriptional patterns of miRNAs and host genes based on 4707 patients across 21 cancer types. We found that only 11.6% of miRNA-host pairs were co-transcribed consistently and strongly across cancer types. Most miRNA-host pairs showed a strong coexpression only in some specific cancer types, demonstrating a high heterogenous pattern. For two particular types of intergenic miRNAs, readthrough and divergent miRNAs, readthrough miRNAs showed higher coexpression with their host genes than divergent ones. miRNAs located within non-coding genes had tighter co-transcription with their hosts than those located within protein-coding genes, especially exonic and junction miRNAs. A few precursor miRNAs changed their dominate form between 5' and 3' strands in different cancer types, including miR-486, miR-99b, let-7e, miR-125a, let-7g, miR-339, miR-26a, miR-16, and miR-218, whereas only two miRNAs with multiple host genes switched their co-transcriptional partner in different cancer types (miR-219a-1 with SLC39A7/HSD17B8 and miR-3615 with RAB37/SLC9A3R1). miRNAs generated from distinct precursors (such as miR-125b from miR-125b-1 or miR-125b-2) were more likely to have cancer-dependent main contributors. miRNAs and hosts were less co-expressed in KIRC than other cancer types, possibly due to its frequent VHL mutations. Our findings shed new light on miRNA biogenesis and cancer diagnosis and treatments.

MicroRNA regulation of the proliferation and apoptosis of Leydig cells in diabetes

BACKGROUND

The number of patients with diabetes is increasing worldwide. Diabetic testicular damage can cause spermiogenesis disorders and sexual dysfunction. We thus explored the role of miRNAs in diabetic testicular damage, and revealed that they could serve as effective prevention and treatment therapeutic targets.

METHODS

Streptozotocin (STZ) was used to generate a rat model of type 2 diabetes. Rat testicular tissues were used for miRNA and mRNA sequencing. Through bioinformatics analysis, we constructed an miRNA-mRNA diabetic testicular damage regulatory network and screened for key miRNAs. We also used Leydig cells to generate a diabetic cell model and detected the downstream target genes of miRNAs, secretion of testosterone, and proliferation and apoptotic levels to elucidate the role and mechanism of the selected miRNAs in diabetic testicular damage.

RESULTS

Using second-generation sequencing, we identified 19 differentially expressed miRNAs and 555 mRNAs in the testes of diabetic rats. Based on computational prediction of targets and negative regulation relationships, we constructed a miRNA-mRNA regulatory network, including 12 miRNAs and 215 mRNAs. KEGG enrichment analysis revealed that genes were more concentrated on the survival signalling pathway. Based on this, we screened 2 key miRNAs, miR-504 and miR-935. In vitro, glucose could induce an increase in miR-504 and miR-935, whereas a decrease in MEK5 and MEF2C in a dose-dependent manner. Overexpression of miR-504 and miR-935 led to the decreased expression of MEK5 and MEF2C, decreased proliferation rate of Leydig cells, increased apoptotic rate, and decreased secretion of testosterone. Whereas, knockdown of miR-504 and miR-935 displayed opposite tendencies.

CONCLUSIONS

miRNAs play important roles in diabetic testicular damage. miR-504 and miR-935 might regulate testicular damage through the classic survival pathway of MEK5-ERK5-MEF2C. Targeted inhibition of miR-504 and miR-935 could reverse the high-glucose-induced testicular complications, thus posing as a potential therapeutic approach in diabetic testicular injury.

HPV16 E6 regulates the proliferation, invasion, and apoptosis of cervical cancer cells by downregulating miR-504

BACKGROUND

Human papillomavirus (HPV) 16 infection is a necessary condition for the pathogenesis and development of cervical cancer. The E6 protein is expressed by the HPV16 E6 gene and promotes malignant phenotype transformation, which is an important mechanism for the occurrence and development of cervical cancer. MicroRNA-504 (miR-504) has been reported as an oncogene or tumor suppressor gene; the expression of miR-504 in cervical cancer has been found to be negatively correlated with HPV infection. However, the relationship between HPV16 E6 and miR-504 and the role of miR-504 in cervical cancer are not clear. In the current study, we observed the effect of HPV16 E6 on the expression of miR-504 in cervical cancer cells, and analyzed whether HPV16 E6 affects proliferation, invasion, and apoptosis in cervical cancer cells by regulating the expression of miR-504.

METHODS

Cervical cancer cells (SiHa) were divided into four groups: the empty vector group, E6 overexpression group, E6 overexpression + miR-NC group, and E6 overexpression+miR-504 group. The expressions levels of HPV16 E6 mRNA and miR-504 were detected by real-time polymerase chain reaction (PCR), and the expression level of HPV16 E6 protein was detected by Western blot. Cell proliferation, invasion, and apoptosis were detected by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, Tastelessly, and flow cytometry, respectively.

RESULTS

The expression level of miR-504 was significantly decreased in E6 overexpression cells compared to the control cells (P<0.05); the overexpression of miR-504 with miR-504 mimic significantly reversed the downregulation of miR-504 in E6 overexpression SiHa cells (P<0.05). MTT and Transwell assays showed that the overexpression of E6 significantly increased proliferation and invasion of SiHa cells (P<0.05). The overexpression of miR-504 reversed the role of HPV16 E6 on the proliferation and invasion in E6 overexpression SiHa cells, and the difference was statistically significant (P<0.05). Further analysis showed that the overexpression of E6 significantly reduced apoptosis of SiHa cells (P<0.05). The overexpression of miR-504 reversed the role of HPV16 E6 on apoptosis in E6 overexpression SiHa cells, and the difference was statistically significant (P<0.05).

CONCLUSIONS

HPV16 E6 may promote the proliferation and invasion, and inhibit the apoptosis, of cervical cancer SiHa cells by downregulating miR-504 expression.

Microarray analysis of aberrant microRNA expression patterns in spinal cord gliomas of different grades

MicroRNAs (miRNAs) are involved in the development of several types of tumor; however, their role in spinal gliomas remains unknown. The present study aimed to identify potentially novel spinal cord gliomas (SCG)-associated miRNAs and to characterize their roles in the development and progression of SCG. miRNA expression levels in low-grade SCG (classed as stage I–II SCG based on the World Health Organization grading system), high-grade SCG (classed as stage IV SCG based on the World Health Organization grading system) and 5 control cases were measured using a miRNA expression microarray. Subsequently, blood samples from the spinal cord of patients with differing grades of SCG were screened for differentially expressed miRNAs (DEmiRNAs). Compared with the control group, 7 upregulated and 36 downregulated miRNAs were identified in the low-grade SCG group and a total of 70 upregulated and 20 downregulated miRNAs were identified in the high-grade SCG group (P≤0.05, fold change >2). Gene Ontology analysis revealed that the regulation of cellular metabolic processes, negative regulation of biological processes and axon guidance were primarily involved. Moreover, pathway analysis showed that the target genes of DEmiRNAs were enriched in tumor-related signaling pathways, such as the MAPK and Wnt signaling pathway. The results suggest that DEmiRNAs in peripheral blood may serve as novel target markers with high specificity and sensitivity for the diagnosis of SCG.

Differential expression of microRNAs in the hippocampi of male and female rodents after chronic alcohol administration

Background

Women are more vulnerable than men to the neurotoxicity and severe brain damage caused by chronic heavy alcohol use. In addition, brain damage due to chronic heavy alcohol use may be associated with sex-dependent epigenetic modifications. This study aimed to identify microRNAs (miRNAs) and their target genes that are differentially expressed in the hippocampi of male and female animal models in response to alcohol.

Methods

After chronic alcohol administration (3~3.5 g/kg/day) in male (control, n = 10; alcohol, n = 12) or female (control, n = 10; alcohol, n = 12) Sprague-Dawley rats for 6 weeks, we measured body weights and doublecortin (DCX; a neurogenesis marker) concentrations and analyzed up- or downregulated miRNAs using GeneChip miRNA 4.0 arrays. The differentially expressed miRNAs and their putative target genes were validated by RT-qPCR.

Results

Alcohol attenuated body weight gain only in the male group. On the other hand, alcohol led to increased serum AST in female rats and decreased serum total cholesterol concentrations in male rats. The expression of DCX was significantly reduced in the hippocampi of male alcohol-treated rats. Nine miRNAs were significantly up- or downregulated in male alcohol-treated rats, including upregulation of miR-125a-3p, let-7a-5p, and miR-3541, and downregulation of their target genes (Prdm5, Suv39h1, Ptprz1, Mapk9, Ing4, Wt1, Nkx3-1, Dab2ip, Rnf152, Ripk1, Lin28a, Apbb3, Nras, and Acvr1c). On the other hand, 7 miRNAs were significantly up- or downregulated in alcohol-treated female rats, including downregulation of miR-881-3p and miR-504 and upregulation of their target genes (Naa50, Clock, Cbfb, Arih1, Ube2g1, and Gng7).

Conclusions

These results suggest that chronic heavy alcohol use produces sex-dependent effects on neurogenesis and miRNA expression in the hippocampus and that sex differences should be considered when developing miRNA biomarkers to diagnose or treat alcoholics.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13293-020-00342-3.

Bladder cancer-associated transcript 2 contributes to nephroblastoma progression

BACKGROUND

Nephroblastoma is a common pediatric kidney tumor. Existing evidence has indicated that long non-coding RNAs (lncRNAs) may be associated with tumorigenesis such as nephroblastoma. However, the contribution of lncRNA bladder cancer-associated transcript 2 (BLACAT2) to tumorigenesis and postoperative nephroblastoma prognosis remains unknown.

METHODS

A total of 50 pairs of patient nephroblastoma and corresponding adjacent non-tumorous tissues were analyzed for BLACAT2 expression. The underlying roles of BLACAT2 in nephroblastoma cells were also investigated. BLACAT2 level was detected in four nephroblastoma cell lines and normal cell line NGC-407 using quantitative real-time PCR. The potential influence of BLACAT2 on nephroblastoma cells was explored based on RNA interference technology in vitro and in vivo. Moreover, the miRNA targeted by BLACAT2 and its target gene were predicted and verified.

RESULTS

BLACAT2 silencing suppressed cell proliferation, colony formation, and tumor growth in vivo and promoted cell apoptosis in vitro. Furthermore, BLACAT2 could directly bind to miR-504-3p, thereby decreasing miR-504-3p expression. In addition, the impact of miR-504-3p on proliferation, colony formation, and nephroblastoma cell apoptosis was reversed by BLACAT2. Wnt11 was identified as a target of miR-504-3p.

CONCLUSIONS

Our study revealed that a novel BLACAT2/miR-504-3p/Wnt11 axis is associated with nephroblastoma, where BLACAT2 is able to sponge miR-504-3p to down-regulate Wnt11.

miR-504 modulates the stemness and mesenchymal transition of glioma stem cells and their interaction with microglia via delivery by extracellular vesicles

Glioblastoma (GBM) is a highly aggressive tumor with poor prognosis. A small subpopulation of glioma stem cells (GSCs) has been implicated in radiation resistance and tumor recurrence. In this study we analyzed the expression of miRNAs associated with the functions of GSCs using miRNA microarray analysis of these cells compared with human neural stem cells. These analyses identified gene clusters associated with glioma cell invasiveness, axonal guidance, and TGF-β signaling. miR-504 was significantly downregulated in GSCs compared with NSCs, its expression was lower in GBM compared with normal brain specimens and further decreased in the mesenchymal glioma subtype. Overexpression of miR-504 in GSCs inhibited their self-renewal, migration and the expression of mesenchymal markers. The inhibitory effect of miR-504 was mediated by targeting Grb10 expression which acts as an oncogene in GSCs and GBM. Overexpression of exogenous miR-504 resulted also in its delivery to cocultured microglia by GSC-secreted extracellular vesicles (EVs) and in the abrogation of the GSC-induced polarization of microglia to M2 subtype. Finally, miR-504 overexpression prolonged the survival of mice harboring GSC-derived xenografts and decreased tumor growth. In summary, we identified miRNAs and potential target networks that play a role in the stemness and mesenchymal transition of GSCs and the miR-504/Grb10 pathway as an important regulator of this process. Overexpression of miR-504 exerted antitumor effects in GSCs as well as bystander effects on the polarization of microglia via delivery by EVs.

Molecular networks of FOXP family: dual biologic functions, interplay with other molecules and clinical implications in cancer progression

Though Forkhead box P (FOXP) transcription factors comprising of FOXP1, FOXP2, FOXP3 and FOXP4 are involved in the embryonic development, immune disorders and cancer progression, the underlying function of FOXP3 targeting CD4 + CD25+ regulatory T (Treg) cells and the dual roles of FOXP proteins as an oncogene or a tumor suppressor are unclear and controversial in cancers to date. Thus, the present review highlighted research history, dual roles of FOXP proteins as a tumor suppressor or an oncogene, their molecular networks with other proteins and noncoding RNAs, cellular immunotherapy targeting FOXP3, and clinical implications in cancer progression.

Dynamic Changes of DNA Methylation and Transcriptome Expression in Porcine Ovaries during Aging

The biological function of human ovaries declines along with aging. To identify the underlying molecular changes during ovarian aging, pigs were used as model animals. Genome-wide DNA methylation and transcriptome-wide RNA expression analyses were performed via high-throughput sequencing of ovaries from young pigs (180 days, puberty stage of first ovulation) and old pigs (eight years, reproductive exhaustion stage). The results identified 422 different methylation regions between old and young pigs; furthermore, a total of 2,243 mRNAs, 95 microRNAs, 248 long noncoding RNAs (lncRNAs), and 116 circular RNAs (circRNAs) were differentially expressed during both developmental stages. Gene ontology analysis showed that these genes related to different methylation and expression are involved in the ovarian aging cycle. Specifically, these are involved in cell apoptosis, death effector domain binding, embryonic development, reproduction and fertilization process, ovarian cumulus expansion, and the ovulation cycle. Multigroup cooperative control relationships were also assessed, and competing endogenous RNA (ceRNA) networks were constructed in the ovarian aging cycle. These data will help to clarify ovary age-associated potential molecular changes in DNA methylation and transcriptional patterns over time.

Down-regulated microRNA-183 mediates the Jak/Stat signaling pathway to attenuate hippocampal neuron injury in epilepsy rats by targeting Foxp1

Recently, the impacts of microRNAs (miRNAs) have been identified in epilepsy (EP), this study was designed to assess the role of miR-183 in hippocampal neuron injury in EP. Rat EP models were established by injected with lithium-pilocarpine. The pathological observation of rats' hippocampus sections was conducted. Expression of miR-183, Foxp1, Jak1, Stat1, and Stat3 in rats' hippocampal tissues was determined by reverse transcription quantitative polymerase chain reaction (RT-qPCR) and Western blot analysis. The proliferation ability and the apoptosis of the rats' neurons were measured. Furthermore, the target relation between miR-183 and Foxp1 was determined by bioinformatics analysis and dual-luciferase gene reporter assay. The levels of miR-183, Jak1, Stat1, and Stat3 were elevated, and the expression of Foxp1 was declined in EP rats' hippocampal tissues. Inhibited miR-183 could up-regulate Foxp1, inhibited miR-183 together with up-regulated Foxp1 could repress hippocampal neuron injury, promote neuron proliferation, suppress neuron apoptosis, and inactivate the Jak/Stat signaling pathway, resulting in an attenuation of EP progression. Moreover, down-regulated Foxp1 could reverse the attenuation of EP progression which was contributed by inhibited miR-183. Our study implies that inhibited miR-183 could up-regulate Foxp1, resulting in an inactivation of the Jak/Stat signaling pathway and promotion of neuron proliferation, as well as inhibition of apoptosis of hippocampal neurons in EP rats, by which the hippocampal neuron injury and EP progression could be repressed.

The expression of circulating miR-504 in plasma is associated with EGFR mutation status in non-small-cell lung carcinoma patients

MicroRNAs (miRNAs), key regulators of gene expression at the post-transcriptional level, are grossly misregulated in some human cancers, including non-small-cell lung carcinoma (NSCLC). The aberrant expression of specific miRNAs results in the abnormal regulation of key components of signalling pathways in tumour cells. MiRNA levels and the activity of the gene targets, including oncogenes and tumour suppressors, produce feedback that changes miRNA expression levels and indicates the cell's genetic activity. In this study, we measured the expression of five circulating miRNAs (miR-195, miR-504, miR-122, miR-10b and miR-21) and evaluated their association with EPIDERMAL GROWTH FACTOR RECEPTOR (EGFR) mutation status in 66 NSCLC patients. Moreover, we examined the discriminative power of circulating miRNAs for EGFR mutant-positive and -negative NSCLC patients using two different data normalisation approaches. We extracted total RNA from the plasma of 66 non-squamous NSCLC patients (31 of whom had tumours with EGFR mutations) and measured circulating miRNA levels using quantitative reverse transcription polymerase chain reaction (RT-qPCR). The miRNA expression levels were normalised using two endogenous controls: miR-191 and miR-16. We found significant associations between the expression of circulating miR-504 and EGFR-activating mutations in NSCLC patients regardless of the normalisation approach used (p = 0.0072 and 0.0236 for miR-16 and miR-191 normalisation, respectively). The greatest discriminative power of circulating miR-504 was observed in patients with EGFR exon 19 deletions versus wild-type EGFR normalised to miR-191 (area under the curve (AUC) = 0.81, p < 0.0001). Interestingly, circulating miR-504 levels were significantly reduced in the v-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog (KRAS)-mutated subgroup compared to EGFR-mutated patients (p < 0.0030) and those with EGFR/KRAS wild-type tumours (p < 0.0359). Our study demonstrated the feasibility and potential diagnostic value of plasma miR-504 expression analysis to distinguish between EGFR-mutated and wild-type NSCLC patients. However, quality control and normalisation strategies are very important and have a major impact on the outcomes of circulating miRNA analyses.

miR-504 suppresses mesenchymal phenotype of glioblastoma by directly targeting the FZD7-mediated Wnt-β-catenin pathway

Background

MicroRNAs (miRNAs) play crucial roles in tumor initiation and development. Previously, we indicated that miR-504 is downregulated and suppresses tumor proliferation in glioblastoma (GBM). However, the regulation and relevant mechanism of miR-504 in GBM mesenchymal (ME) transition remain unclear.

Methods

Transcriptome and clinical data were obtained from The Cancer Genome Atlas (TCGA) database. The potential functions of miR-504 were predicted using gene ontology analysis. GBM cell migration and invasion were examined using wound healing and Transwell assays. Epithelial–mesenchymal transition (EMT) progression in GBM cell lines was detected with immunofluorescence and western blotting. The stemness activity of glioma stem-like cells (GSCs) was assessed by sphere formation assay and tumor xenograft model. miR-504 binding to the FZD7 (frizzled class receptor 7) 3′ untranslated region (3′UTR) was validated using dual luciferase reporter assay. TOP/FOP Flash assays were conducted to determine the effects of miR-504 on Wnt/β-catenin signaling.

Results

Analysis of TCGA transcriptomic data showed that low miR-504 expression correlated with ME subtype transition and poor survival in patients with GBM. Functional experiments showed that miR-504 overexpression suppressed malignant behaviors of GBM cells, such as migration, invasion, EMT, and stemness activity. Furthermore, miR-504 was a negative regulator of the Wnt–β-catenin pathway by directly repressing FZD7 expression, and FZD7 overexpression reversed the EMT inhibition caused by miR-504. Moreover, the low miR-504/FZD7 expression ratio was a ME subtype marker and could serve as a significant prognostic indicator and predict the clinical outcome of chemotherapy and radiotherapy for patients with GBM in TCGA dataset.

Conclusions

Our results suggest that miR-504 suppresses the aggressive biological processes associated with the ME phenotype of GBM and could be a potential candidate for therapeutic applications in these malignant brain tumors.

Electronic supplementary material

The online version of this article (10.1186/s13046-019-1370-1) contains supplementary material, which is available to authorized users.

MicroRNA‑504 targets AEG‑1 and inhibits cell proliferation and invasion in retinoblastoma

The dysregulation of microRNAs (miRNAs/miRs) has become increasingly recognized as a primary feature of retinoblastoma (RB). Furthermore, miRNAs have been demonstrated to be involved in the occurrence and development of RB. Therefore, it is crucial to investigate the expression profile and roles of miRNAs in RB in order to identify potential therapeutic targets to treat patients with RB. The expression profile and biological roles of miRNA‑504 (miR‑504) have been reported in numerous types of human cancer; however, the roles of miR‑504 in RB remain unknown. In the present study, it was demonstrated that miR‑504 expression was significantly decreased in RB tissues and cell lines. Functional analysis identified that resumption of miR‑504 expression suppressed cell proliferation and invasion in RB. Furthermore, astrocyte elevated gene‑1 (AEG‑1) was determined to be a direct target of miR‑504 in RB, and a negative correlation between miR‑504 and AEG‑1 mRNA expression levels was observed in RB tissues. Additionally, the tumor‑suppressing effects of miR‑504 overexpression in RB cells could be rescued by AEG‑1 upregulation. In conclusion, these results indicated a significant role of the miR‑504/AEG‑1 pathway in inhibiting the aggressiveness of RB, suggesting that this miRNA may be employed as a therapeutic target for the treatment of patients with this disease.

MicroRNA-504 modulates osteosarcoma cell chemoresistance to cisplatin by targeting p53

Chemoresistance implicates the therapeutic value of cisplatin and remains a primary obstacle to its clinical use. MicroRNAs (miRs) negatively modulate the expression of their target genes and are associated with the occurrence and progression of various types of tumor. The abnormal expression of miR-504 has been reported in certain types of human tumor and has been associated with tumor prognosis. However, the association between miR-504 and cisplatin in human osteosarcoma remains unclear. The present study therefore aimed to assess the in vitro effects and possible mechanism of miR-504 in cell proliferation, apoptosis and cisplatin resistance in MG63 osteosarcoma cells. The results demonstrated that miR-504 was overexpressed in osteosarcoma tissues and cells. This overexpression also induced cell proliferation, as determined by MTT and EdU staining assays. Furthermore, miR-504 suppressed cisplatin-induced apoptosis, which was demonstrated via MTT, cell morphology analysis and flow cytometry. Cisplatin-induced G₁ arrest was also suppressed, which was determined by flow cytometry. The potential target genes of miR-504 were predicted using bioinformatics. p53 was confirmed to be a direct target of miR-504 using a luciferase reporter assay and western blot analysis revealed that miR-504 negatively regulated p53 expression at a molecular level. These results indicate that miR-504 contributes to cisplatin resistance in MG63 osteosarcoma cells by suppressing p53. miR-504 may therefore be a potential biomarker for cisplatin resistance in patients with osteosarcoma.

Oncogenic and Tumor-Suppressive Roles of MicroRNAs with Special Reference to Apoptosis: Molecular Mechanisms and Therapeutic Potential

MicroRNAs (miRNAs) are the non-coding class of minute RNA molecules that negatively control post-transcriptional regulation of various functional genes. These miRNAs are transcribed from the loci present in the introns of functional or protein-coding genes, exons of non-coding genes, or even in the 3'-untranslated region (3'-UTR). They have potential to modulate the stability or translational efficiency of a variety of target RNA [messenger RNA (mRNA)]. The regulatory function of miRNAs has been elucidated in several pathological conditions, including neurological (Alzheimer's disease and Parkinson's disease) and cardiovascular conditions, along with cancer. Importantly, miRNA identification in cancer progression and invasion has evolved as an incipient era in cancer treatment. Several studies have shown the influence of miRNAs on various cancer processes, including apoptosis, invasion, metastasis and angiogenesis. In particular, apoptosis induction in tumor cells through miRNA has been extensively studied. The biphasic mode (up- and down-regulation) of miRNA expression in apoptosis and other cancer processes has already been determined. The findings of these studies could be utilized to develop potential therapeutic strategies for the management of various cancers. The present review critically describes the oncogenic and tumor suppressor role of miRNAs in apoptosis and other cancer processes, therapy resistance, and use of their presence in the body fluids as biomarkers.

STAT3 promotes tumour progression in glioma by inducing FOXP1 transcription

Objective

This paper investigated the effects of STAT3 through promoting FOXP1 transcription on proliferation, apoptosis and invasion in glioma cells.

Methods

Quantitative real‐time PCR (qRT‐PCR) and Western blot assay were administered to assess the mRNA and protein expression levels of STAT3 and FOXP1 in glioma tissues and cells, respectively. Luciferase reporter and Chromatin Immunoprecipitation (ChIP) assays were implemented to determine the correlation between STAT3 and FOXP1. MTT and colony formation assays were conducted to identify cell growth. Flow cytometry was run to detect the cell apoptosis rate of glioma cells. Transwell assays were conducted to reveal cell invasion ability.

Results

The mRNA and protein expression levels of STAT3 were highly expressed in glioma tissues and cells. After cells transfected with siRNA of STAT3, both STAT3 and FOXP1 were simultaneously downregulated. STAT3 directly regulated FOXP1 transcription. STAT3 promoted cell proliferation, inhibited cell apoptosis and enhanced cell invasion through promoting FOXP1 transcription in glioma cells.

Conclusion

In summary, STAT3 gene was a transcriptional regulator of FOXP1. Depleted STAT3 restrained cell proliferation and invasion, promoted cell apoptosis in glioma cells. This molecular mechanism between STAT3 and FOXP1 can serve as a therapeutic target for glioma treatment.

MicroRNA-504 functions as a tumor suppressor in hepatocellular carcinoma through inhibiting Frizzled-7-mediated-Wnt/β-catenin signaling

Accumulating evidence suggests that microRNAs (miRNAs) are critical regulators in the development and progression of various malignant tumors, including hepatocellular carcinoma (HCC). Multiple findings have indicated that miRNA-504 (miR-504) is dysregulated in several types of cancers, functioning as an oncogenic miRNA or a tumor suppressive miRNA. However, the role of miR-504 in HCC remains unknown. In this study, we aimed to detect the expression pattern of miR-504 in HCC tissues and cell lines and investigate the precise biological function in HCC cells. Our results showed that miR-504 expression levels were frequently downregulated in both HCC tissues and cell lines. Gain-of-function experiments demonstrated that miR-504 overexpression inhibited the proliferation and invasion in HCC cell lines. By contrast, miR-504 inhibition had the opposite effect. Interestingly, bioinformatics analysis predicted that Frizzled-7 (FZD7) was a potential target gene of miR-504. Dual-luciferase reporter assays confirmed that miR-504 directly targeted the 3'-untranslated region of FZD7 mRNA. In addition, our results showed that miR-504 negatively regulated the mRNA and protein expression of FZD7 in HCC cell lines. Moreover, miR-540 overexpression inhibited the cellular expression of β-catenin and blocked the activation of Wnt signaling in HCC cells. Notably, restoration of FZD7 expression significantly reversed the inhibitory effect of miR-504 on proliferation, invasion, and Wnt/β-catenin signaling in HCC cells. In conclusion, our results demonstrate that miR-504 functions as a tumor suppressive miRNA that inhibits the proliferation and invasion of HCC cells by targeting FZD7 and inhibiting Wnt/β-catenin signaling. Our study provides evidence that miR-504-meidated FZD7/Wnt/β-catenin signaling pathway plays an important role in HCC development and progression and suggests miR-504 as a novel future therapeutic target for treatment of HCC.

Interplay between miRNAs and host genes and their role in cancer

MicroRNAs (miRNAs) are small endogenous non-coding functional RNAs that post-transcriptionally regulate gene expression. They play essential roles in nearly all biological processes including cell development and differentiation, DNA damage repair, cell death as well as intercellular communication. They are highly involved in cancer, acting as tumor suppressors and/or promoters to modulate cell proliferation, epithelial-mesenchymal transition and tumor invasion and metastasis. Recent studies have shown that more than half of miRNAs are located within protein-coding or non-coding genes. Intragenic miRNAs and their host genes either share the promoter or have independent transcription. Meanwhile, miRNAs work as partners or antagonists of their host genes by fine-tuning their target genes functionally associated with host genes. This review outlined the complicated relationship between intragenic miRNAs and host genes. Focusing on miRNAs known as oncogenes or tumor suppressors in specific cancer types, it studied co-expression relationships between these miRNAs and host genes in the cancer types using TCGA data sets, which validated previous findings and revealed common, tumor-specific and even subtype-specific patterns. These observations will help understand the function of intragenic miRNAs and further develop miRNA therapeutics in cancer.

MicroRNA-1231 exerts a tumor suppressor role through regulating the EGFR/PI3K/AKT axis in glioma

PURPOSE

MicroRNAs (miRNAs) have been shown to be involved in the initiation and progression of glioma. However, the underlying molecular mechanisms are still unclear.

METHODS

We performed microarray analysis to evaluate miRNA expression levels in 158 glioma tissue samples, and examined miR-1231 levels in glioma samples and healthy brain tissues using qRT-PCR. In vitro analyses were performed using miR-1231 mimics, inhibitors, and siRNA targeting EGFR. We used flow cytometry, CCK-8 assays, and colony formation assays to examine glioma proliferation and cell cycle analysis. A dual luciferase reporter assay was performed to examine miR-1231 regulation of EGFR, and the effect of upregulated miR-1231 was investigated in a subcutaneous GBM model.

RESULTS

We found that miR-1231 expression was decreased in human glioma tissues and negatively correlated with EGFR levels. Moreover, the downregulation of miR-1231 negatively correlated with the clinical stage of human glioma patients. miR-1231 overexpression dramatically downregulated glioma cell proliferation, and suppressed tumor growth in a nude mouse model. Bioinformatics prediction and a luciferase assay confirmed EGFR as a direct target of miR-1231. EGFR overexpression abrogated the suppressive effect of miR-1231 on the PI3K/AKT pathway and G1 arrest.

CONCLUSIONS

Taken together, these results demonstrated that EGFR is a direct target of miR-1231. Our findings suggest that the miR-1231/EGFR axis may be a helpful future diagnostic target for malignant glioma.

Bioinformatics analysis of key differentially expressed genes in well and poorly differentiated endometrial carcinoma

Endometrial carcinoma (EC) is one of the most common gynecological malignancies. The malignant degree increases between grade (G)1 and G3, and EC of G3 usually presents a high recurrence rate and poor prognosis. Therefore, the present study aimed to examine the principal genes associated with the degree of differentiation in EC. The microarrays GSE17025, GSE24537 and GSE35784, representing data of Type I EC samples of G1 and G3, were downloaded from the Gene Expression Omnibus. The differentially expressed genes (DEGs) and differentially expressed micro (mi)RNAs (DEMs) were identified, followed by functional enrichment analyses and interaction network construction. In total, 83 upregulated and 130 downregulated DEGs with the same expression trends in two mRNA datasets were screened. The upregulated DEGs were primarily enriched in 'mitotic cell cycle process', 'cell cycle process' and 'mitotic cell cycle'; while the downregulated DEGs were enriched in 'cellular component assembly involved in morphogenesis', 'cell projection organization' and 'microtubule‑based movement'. From the protein‑protein interaction network, DNA topoisomerase IIα, kinesin family member 11, cyclin B1 and BUB1 mitotic checkpoint serine/threonine were identified as foremost hub genes. One module was extracted and involved in 'mitotic cell cycle process' and 'cell cycle process'. Based on the analysis of DEMs and the miRNA‑target regulatory network, miRNA‑9 may be the most important upregulated DEM, and the DEGs forkhead box P1 and cyclin E1 may serve vital roles in the differentiation of EC. In conclusion, principal genes were identified that may be determinants of the carcinogenesis of poorly differentiated EC, which may facilitate the examination of potential molecular mechanisms. These genes may additionally help identify candidate biomarkers and novel therapeutic targets for poorly differentiated EC.

circ-SHKBP1 Regulates the Angiogenesis of U87 Glioma-Exposed Endothelial Cells through miR-544a/FOXP1 and miR-379/FOXP2 Pathways

Circular RNAs (circRNAs) are a type of endogenous non-coding RNAs, which have been considered to mediate diverse tumorigenesis including angiogenesis. The present study aims to elucidate the potential role and molecular mechanism of circ-SHKBP1 in regulating the angiogenesis of U87 glioma-exposed endothelial cells (GECs). The expression of circ-SHKBP1, but not linear SHKBP1, was significantly upregulated in GECs compared with astrocyte-exposed endothelial cells (AECs). circ-SHKBP1 knockdown inhibited the viability, migration, and tube formation of GECs dramatically. The expressions of miR-379/miR-544a were downregulated in GECs, and circ-SHKBP1 functionally targeted miR-544a/miR-379 in an RNA-induced silencing complex (RISC) manner. Dual-luciferase reporter assay demonstrated that forkhead box P1/P2 (FOXP1/FOXP2) were targets of miR-544a/miR-379. The expressions of FOXP1/FOXP2 were upregulated in GECs, and silencing of FOXP1/FOXP2 inhibited the viability, migration, and tube formation of GECs. Meanwhile, FOXP1/FOXP2 promoted angiogenic factor with G patch and FHA domains 1 (AGGF1) expression at the transcriptional level. Furthermore, knockdown of AGGF1 suppressed the viability, migration, and tube formation of GECs via phosphatidylinositol 3-kinase (PI3K)/AKT and extracellular signal-regulated kinase (ERK)1/2 pathways. Taken together, the present study demonstrated that circ-SHKBP1 regulated the angiogenesis of GECs through miR-544a/FOXP1 and miR-379/FOXP2 pathways, and these findings might provide a potential target and effective strategy for combined therapy of gliomas.

Blood and lung microRNAs as biomarkers of pulmonary tumorigenesis in cigarette smoke-exposed mice

Cigarette smoke (CS) is known to dysregulate microRNA expression profiles in the lungs of mice, rats, and humans, thereby modulating several pathways involved in lung carcinogenesis and other CS-related diseases. We designed a study aimed at evaluating (a) the expression of 1135 microRNAs in the lung of Swiss H mice exposed to mainstream CS during the first 4 months of life and thereafter kept in filtered air for an additional 3.5 months, (b) the relationship between lung microRNA profiles and histopathological alterations in the lung, (c) intergender differences in microRNA expression, and (d) the comparison with microRNA profiles in blood serum. CS caused multiple histopathological alterations in the lung, which were almost absent in sham-exposed mice. An extensive microRNA dysregulation was detected in the lung of CS-exposed mice. Modulation of microRNA profiles was specifically related to the histopathological picture, no effect being detected in lung fragments with non-neoplastic lung diseases (emphysema or alveolar epithelial hyperplasia), whereas a close association occurred with the presence and multiplicity of preneoplastic lesions (microadenomas) and benign lung tumors (adenomas). Three microRNAs regulating estrogen and HER2-dependent mechanisms were modulated in the lung of adenoma-bearing female mice. Blood microRNAs were also modulated in mice affected by early neoplastic lesions. However, there was a poor association between lung microRNAs and circulating microRNAs, which can be ascribed to an impaired release of mature microRNAs from the damaged lung. Studies in progress are evaluating the feasibility of analyzing blood microRNAs as a molecular tool for lung cancer secondary prevention.

MiR-504 inhibits cell proliferation and invasion by targeting LOXL2 in non small cell lung cancer

BACKGROUND

MicroRNAs (miRNAs) play crucial roles in tumor initiation and development. The aim of the study was to explore the clinicopathological role and functional effects of miR-504 in non small cell lung cancer (NSCLC).

METHODS

Quantitative reverse transcription polymerase chain reaction (QRT-PCR) was applied to detect the expression of miR-504 in 55 cases of NSCLC tissues and matched adjacent normal tissues in NSCLC patients. MTT, colony formation and transwell invasion assays were performed to evaluate the effects of miR-504 on cell proliferation and invasion, respectively. Dual luciferase reporter assay was used to verify that LOXL2 was a direct target of miR-504. QRT-PCR and western blot analysis were performed to analyze mRNA and protein expression.

RESULTS

In the study, we demonstrated that miR-504 was notably downregulated in NSCLC tissues compared with adjacent normal tissues. Lower miR-504 expression positively correlated with lymph node metastasis and advanced TNM stage in patients. Furthermore, upregulation of miR-504 significantly inhibited cell proliferation, cell invasion and EMT process of NSCLC. QRT-PCR, western blot and luciferase reporter assays confirmed that miR-504 could bind to LOXL2 3'UTR region and regulate its expression. Moreover, ectopic expression of LOXL2 could rescue the inhibiting effects on cell proliferation and invasion induced by miR-504 in NSCLC cells.

CONCLUSIONS

Our results indicated that miR-504 functioned as a tumor suppressor in NSCLC and may serve as a target of NSCLC treatment.

Inhibition of TDP43-Mediated SNHG12-miR-195-SOX5 Feedback Loop Impeded Malignant Biological Behaviors of Glioma Cells

Long non-coding RNA (lncRNA) dysregulation is involved in tumorigenesis and regulation of diverse cellular processes in gliomas. lncRNA SNHG12 is upregulated and promotes cell growth in human osteosarcoma cells. TAR-DNA binding protein 43 (TDP43) functions as an oncogene in various tumors by modulating RNA expression. Downregulation of TDP43 or SNHG12 significantly inhibited malignant biological behaviors of glioma cells. miR-195, downregulated in glioma tissues and cells, significantly impaired the malignant progression of glioma cells. TDP43 upregulated miR-195 in an SNHG12-dependent manner. We further revealed that SNHG12 and miR-195 were in an RNA-induced silencing complex (RISC). Inhibition of SNHG12 combined with restoration of miR-195 robustly reduced tumor growth in vivo. SOX5 was overexpressed in glioma tissues and cells. miR-195 targeted SOX5 3′ UTR in a sequence-specific manner. Gelsolin was activated by SOX5. More importantly, SOX5 activated SNHG12 promoter and upregulated its expression, forming a feedback loop. Dysregulation of SNHG12, miR-195, and SOX5 predicted poor prognosis of glioma patients. The present study demonstrated that SNHG12-miR-195-SOX5 feedback loop exerted a crucial role in the regulation of glioma cells’ malignant progression.

miR-504 promotes tumour growth and metastasis in human osteosarcoma by targeting TP53INP1

An increasing number of studies have demonstrated that microRNAs participate in the development of osteosarcoma by acting as tumour suppressor or tumour-promoting genes. We investigated the role of miR-504 in the growth and metastasis of osteosarcoma. The expression of miR-504 in clinical osteosarcoma samples was higher than that in the adjacent normal tissue and correlated with tumour size and clinical stage. Tumour protein p53-inducible nuclear protein 1 (TP53INP1) was downregulated in the clinical osteosarcoma samples compared with the adjacent normal tissues and was consistently correlated with the clinical stage. The results of dual-luciferase reporter assay and western blot analysis demonstrated that the TP53INP1 gene is a direct target of miR-504. Altogether, the Cell Counting Kit-8 (CCK-8), the colony formation, the flow cytometry and the Transwell assay results demonstrated that miR-504 promoted osteosarcoma cell growth and metastasis in vitro. P73, P21, Bax, cleaved-caspase-3 and secreted protein acidic and rich in cysteine (SPARC) were associated with the suppressive role of miR-504/TP53INP1. The overexpression of miR-504 in osteosarcoma xenografts enhanced the tumour growth and increased the metastatic burden. Collectively, these results revealed that TP53INP1 is a target gene of miR-504 and that miR-504 enhances osteosarcoma growth and promotes distant metastases by targeting TP53INP1. Thus, miR-504/TP53INP1 may be associated with osteosarcoma size and clinical stage.

Roles of GSK-3 and microRNAs on epithelial mesenchymal transition and cancer stem cells

Various signaling pathways exert critical roles in the epithelial to mesenchymal transition (EMT) and cancer stem cells (CSCs). The Wnt/beta-catenin, PI3K/PTEN/Akt/mTORC, Ras/Raf/MEK/ERK, hedgehog (Hh), Notch and TP53 pathways elicit essential regulatory influences on cancer initiation, EMT and progression. A common kinase involved in all these pathways is moon-lighting kinase glycogen synthase kinase-3 (GSK-3). These pathways are also regulated by micro-RNAs (miRs). TP53 and components of these pathways can regulate the expression of miRs. Targeting members of these pathways may improve cancer therapy in those malignancies that display their abnormal regulation. This review will discuss the interactions of the multi-functional GSK-3 enzyme in the Wnt/beta-catenin, PI3K/PTEN/Akt/mTORC, Ras/Raf/MEK/ERK, Hh, Notch and TP53 pathways. The regulation of these pathways by miRs and their effects on CSC generation, EMT, invasion and metastasis will be discussed.

MicroRNAs as regulators and mediators of forkhead box transcription factors function in human cancers

Evidence has shown that microRNAs are widely implicated as indispensable components of tumor suppressive and oncogenic pathways in human cancers. Thus, identification of microRNA targets and their relevant pathways will contribute to the development of microRNA-based therapeutics. The forkhead box transcription factors regulate numerous processes including cell cycle progression, metabolism, metastasis and angiogenesis, thereby facilitating tumor initiation and progression. A complex network of protein and non-coding RNAs mediates the expression and activity of forkhead box transcription factors. In this review, we summarize the current knowledge and concepts concerning the involvement of microRNAs and forkhead box transcription factors and describe the roles of microRNAs-forkhead box axis in various disease states including tumor initiation and progression. Additionally, we describe some of the technical challenges in the use of the microRNA-forkhead box signaling pathway in cancer treatment.

MicroRNA-342 inhibits the progression of glioma by directly targeting PAK4

Glioma is an extremely aggressive and lethal type of brain tumour that originates from glial cells. MicroRNA (miRNA) dysregulation has been implicated in the occurrence and progression of many human cancers, including glioma. Thus, some specific miRNAs are potential therapeutic targets for glioma diagnosis, therapy and prognosis. MicroRNA-342 (miR‑342) has been reported to be abnormally expressed in various types of cancer. However, the precise roles of miR‑342 in glioma remain unknown. The present study showed that miR‑342 is relatively downregulated in glioma tissues and cell lines compared with that in adjacent normal tissues and normal human astrocytes. We observed that low miR‑342 expression levels are correlated with advanced WHO grades and low KPS scores of glioma patients. In addition, the results of the functional assays demonstrated that miR‑342 overexpression inhibits the proliferation and invasion of glioma cells and induces apoptosis. Further investigation revealed that P21 activated kinases 4 (PAK4) is a direct target of miR‑342 in glioma. PAK4 was significantly upregulated in glioma tissues and inversely correlated with miR‑342 expression. Moreover, PAK4 knockdown can mimic the effects of miR‑342 on glioma cell proliferation, invasion and apoptosis. Notably, restoration of expression of PAK4 reversed the suppressive effects induced by the miR‑342 in the glioma cells. The upregulation of miR‑342 inactivated the AKT and ERK pathways in glioma. These findings may contribute to the understanding of the molecular mechanism underlying the carcinogenesis and progression of glioma, and to provide novel therapeutic target for the treatment of glioma patients.

Suppressive Role of MicroRNA-148a in Cell Proliferation and Invasion in Ovarian Cancer Through Targeting Transforming Growth Factor-β-Induced 2

Ovarian cancer (OC) is one of the most common gynecological malignancies. MicroRNAs (miRs) play a crucial role in the development and progression of OC, but the underlying mechanism remains largely unclear. Our study investigated the regulatory role of miR-148a in OC cell proliferation and invasion. We found that miR-148a was significantly downregulated in OC tissues compared to their matched adjacent nontumor tissues. In addition, its expression was also reduced in OC cell lines (SKOV3, ES-2, OVCAR, and A2780) compared to normal ovarian epithelial cells. Overexpression of miR-148a caused a significant decrease in OC cell proliferation and invasion, as well as reduced MMP9 protein levels. Transforming growth factor-β-induced 2 (TGFI2) was further identified as a target gene of miR-148a, and its protein expression was downregulated in OC cells after miR-148a overexpression. Restoration of TGFI2 attenuated the suppressive effects of miR-148a on OC cell proliferation and invasion. Moreover, we found that TGFI2 was remarkably upregulated in OC tissues when compared with their matched adjacent nontumor tissues, and observed a reverse correlation between miR-148a and TGFI2 expression in OC tissues. On the basis of these findings, we suggest that miR-148a inhibits OC cell proliferation and invasion partly through inhibition of TGFI2. Therefore, our study highlights the importance of the miR-148a/TGFI2 axis in the malignant progression of OC.

Knockdown of Long Non-Coding RNA KCNQ1OT1 Restrained Glioma Cells' Malignancy by Activating miR-370/CCNE2 Axis

Accumulating evidence has highlighted the potential role of long non-coding RNAs (lncRNAs) as biomarkers and therapeutic targets in solid tumors. Here, we elucidated the function and possible molecular mechanisms of lncRNA KCNQ1OT1 in human glioma U87 and U251 cells. Quantitative Real-Time polymerase chain reaction (qRT-PCR) demonstrated that KCNQ1OT1 expression was up-regulated in glioma tissues and cells. Knockdown of KCNQ1OT1 exerted tumor-suppressive function in glioma cells. Moreover, a binding region was confirmed between KCNQ1OT1 and miR-370 by dual-luciferase assays. qRT-PCR showed that miR-370 was down-regulated in human glioma tissue and cells. In addition, restoration of miR-370 exerted tumor-suppressive function via inhibiting cell proliferation, migration and invasion, while promoting the apoptosis of human glioma cells. Knockdown of KCNQ1OT1 decreased the expression level of Cyclin E2 (CCNE2) by binding to miR-370. Further, miR-370 bound to CCNE2 3′UTR region and decreased the expression of CCNE2. These results provided a comprehensive analysis of KCNQ1OT1-miR-370-CCNE2 axis in human glioma cells and might provide a novel strategy for glioma treatment.

Integration of MicroRNA, mRNA, and Protein Expression Data for the Identification of Cancer-Related MicroRNAs

MicroRNAs (miRNAs) are responsible for the regulation of target genes involved in various biological processes, and may play oncogenic or tumor suppressive roles. Many studies have investigated the relationships between miRNAs and their target genes, using mRNA and miRNA expression data. However, mRNA expression levels do not necessarily represent the exact gene expression profiles, since protein translation may be regulated in several different ways. Despite this, large-scale protein expression data have been integrated rarely when predicting gene-miRNA relationships. This study explores two approaches for the investigation of gene-miRNA relationships by integrating mRNA expression and protein expression data. First, miRNAs were ranked according to their effects on cancer development. We calculated influence scores for each miRNA, based on the number of significant mRNA-miRNA and protein-miRNA correlations. Furthermore, we constructed modules containing mRNAs, proteins, and miRNAs, in which these three molecular types are highly correlated. The regulatory interactions between miRNA and genes in these modules have been validated based on the direct regulations, indirect regulations, and co-regulations through transcription factors. We applied our approaches to glioblastomas (GBMs), ranked miRNAs depending on their effects on GBM, and obtained 52 GBM-related modules. Compared with the miRNA rankings and modules constructed using only mRNA expression data, the rankings and modules constructed using mRNA and protein expression data were shown to have better performance. Additionally, we experimentally verified that miR-504, highly ranked and included in the identified modules, plays a suppressive role in GBM development. We demonstrated that the integration of both expression profiles allows a more precise analysis of gene-miRNA interactions and the identification of a higher number of cancer-related miRNAs and regulatory mechanisms.

miR-320a regulates cell proliferation and apoptosis in multiple myeloma by targeting pre-B-cell leukemia transcription factor 3

Aberrant expression of microRNAs (miRNAs) is implicated in cancer development and progression. While miR-320a is reported to be deregulated in many malignancy types, its biological role in multiple myeloma (MM) remains unclear. Here, we observed reduced expression of miR-320a in MM samples and cell lines. Ectopic expression of miR-320a dramatically suppressed cell viability and clonogenicity and induced apoptosis in vitro. Mechanistic investigation led to the identification of Pre-B-cellleukemia transcription factor 3 (PBX3) as a novel and direct downstream target of miR-320a. Interestingly, reintroduction of PBX3 abrogated miR-320a-induced MM cell growth inhibition and apoptosis. In a mouse xenograft model, miR-320a overexpression inhibited tumorigenicity and promoted apoptosis. Our findings collectively indicate that miR-320a inhibits cell proliferation and induces apoptosis in MM cells by directly targeting PBX3, supporting its utility as a novel and potential therapeutic agent for miRNA-based MM therapy.