miR-221/222 confers radioresistance in glioblastoma cells through activating Akt independent of PTEN status

A 13 mer LNA-i-miR-221 Inhibitor Restores Drug Sensitivity in Melphalan-Refractory Multiple Myeloma Cells

PURPOSE

The onset of drug resistance is a major cause of treatment failure in multiple myeloma. Although increasing evidence is defining the role of miRNAs in mediating drug resistance, their potential activity as drug-sensitizing agents has not yet been investigated in multiple myeloma.

EXPERIMENTAL DESIGN

Here we studied the potential utility of miR-221/222 inhibition in sensitizing refractory multiple myeloma cells to melphalan.

RESULTS

miR-221/222 expression inversely correlated with melphalan sensitivity of multiple myeloma cells. Inhibition of miR-221/222 overcame melphalan resistance and triggered apoptosis of multiple myeloma cells in vitro, in the presence or absence of human bone marrow (BM) stromal cells. Decreased multiple myeloma cell growth induced by inhibition of miR-221/222 plus melphalan was associated with a marked upregulation of pro-apoptotic BBC3/PUMA protein, a miR-221/222 target, as well as with modulation of drug influx-efflux transporters SLC7A5/LAT1 and the ABC transporter ABCC1/MRP1. Finally, in vivo treatment of SCID/NOD mice bearing human melphalan-refractory multiple myeloma xenografts with systemic locked nucleic acid (LNA) inhibitors of miR-221 (LNA-i-miR-221) plus melphalan overcame drug resistance, evidenced by growth inhibition with significant antitumor effects together with modulation of PUMA and ABCC1 in tumors retrieved from treated mice.

CONCLUSIONS

Taken together, our findings provide the proof of concept that LNA-i-miR-221 can reverse melphalan resistance in preclinical models of multiple myeloma, providing the framework for clinical trials to overcome drug resistance, and improve patient outcome in multiple myeloma.

Exosome-mediated transfer of miR-222 is sufficient to increase tumor malignancy in melanoma

Background

Growing evidence is showing that metastatic cell populations are able to transfer their characteristics to less malignant cells. Exosomes (EXOs) are membrane vesicles of endocytic origin able to convey their cargo of mRNAs, microRNAs (miRs), proteins and lipids from donors to proximal as well as distant acceptor cells. Our previous results indicated that miR-221&222 are key factors for melanoma development and dissemination. The aim of this study was to verify whether the tumorigenic properties associated with miR-222 overexpression can be also propagated by miR-222-containing EXOs.

Methods

EXOs were isolated by UltraCentrifugation or Exoquick-TC^® methods. Preparations of melanoma-derived vesicles were characterized by using the Nanosight™ technology and the expression of exosome markers analyzed by western blot. The expression levels of endogenous and exosomal miRNAs were examined by real time PCR. Confocal microscopy was used to evaluate transfer and uptake of microvesicles from donor to recipient cells. The functional significance of exosomal miR-222 was estimated by analyzing the vessel-like process formation, as well as cell cycle rates, invasive and chemotactic capabilities.

Results

Besides microvesicle marker characterization, we evidenced that miR-222 exosomal expression mostly reflected its abundance in the cells of origin, correctly paralleled by repression of its target genes, such as p27Kip1, and induction of the PI3K/AKT pathway, thus confirming its functional implication in cancer. The possible differential significance of PI3K/AKT blockade was assessed by using the BKM120 inhibitor in miR-222-transduced cell lines. In addition, in vitro cultures showed that vesicles released by miR-222-overexpressing cells were able to transfer miR-222-dependent malignancy when taken-up by recipient primary melanomas. Results were confirmed by antagomiR-221&222 treatments and by functional observations after internalization of EXOs devoid of these miRs.

Conclusion

All together these data, besides generally confirming the role of miR-222 in melanoma tumorigenesis, supported its responsibility in the exosome-associated melanoma properties, thus further indicating this miR as potential diagnostic and prognostic biomarker and its abrogation as a future therapeutic option.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-016-0811-2) contains supplementary material, which is available to authorized users.

MicroRNA-490-3p inhibits colorectal cancer metastasis by targeting TGFβR1

Background

Colorectal cancer (CRC) is one of the most common malignances worldwide. Metastasis is responsible for the rapid recurrence and poor prognosis of CRC. However, the underlying molecular mechanism of CRC metastasis remains largely unclear. In this study we purposed to investigate the expression and biological functions of miR-490-3p in CRC metastasis, as well as to identify its downstream target genes and influenced pathway.

Methods

The expression level of miR-490-3p in CRC cell lines, CRC adjacent normal tissues, non-metastasis and metastasis tissues were assessed by quantitative real-time PCR. Patient survivals were follow-up up to 7 years. Gain-of-function and loss-of-function study on cell migration and invasion abilities were carried out by transfection of miR-490-3p mimics or inhibitors respectively. The molecular targets of miR-490-3p were computationally identified and experimentally verified by dual-luciferase reporter assay and western blot. Functional rescue was also conducted to confirm miR-490-3p inhibits CRC metastasis by targeting TGF-β signaling pathway.

Results

miR-490-3p expression was persistently downregulated during CRC malignant progression, as well as in CRC cell lines. Artificially overexpression miR-490-3p in CRC cell lines inhibited cell migration and invasion abilities while knockdown miR-490-3p expression caused the reverse effects. TGFβR1 and MMP2/9 were the downstream targets of miR-490-3p in CRC. Inhibition of TGFβR1 could partially recover the tumor suppression effect of miR-490-3p.

Conclusion

miR-490-3p is downregulated during CRC malignant progression. miR-490-3p represses CRC cell migration and invasion abilities, partially by targeting to the TGF-β signaling pathway. Taken together, miR-490-3p is acting as a tumor suppressor in CRC.

High levels of apoptosis are induced in human glioma cell lines by co-administration of peptide nucleic acids targeting miR-221 and miR-222

The biological activity of a combined treatment of U251, U373 and T98G glioma cell lines with two anti-miR PNAs, directed against miR‑221 and miR‑222 and conjugated with an ocataarginine tail (R8-PNA-a221 and R8-PNA-a222) for efficient cellular delivery, was determined. Apoptosis was analyzed, and the effect of the combined treatment of glioma cells with either or both PNAs on the reversion of drug-resistance phenotype was assessed in the temozolomide-resistant T98G glioma cell line. Selectivity of PNA/miRNA interactions was studied by surface plasmon resonance (SPR)-based Biacore analysis. Specificity of the PNA effects at the cellular level was analyzed by RT-qPCR. These experiments support the concept that the effects of R8-PNA-a221 and R8-PNA-a222 are specific. The studies on apoptosis confirmed that the R8-PNA-a221 induces apoptosis and demonstrated the pro-apoptotic effects of R8-PNA-a222. Remarkably, increased pro-apoptotic effects were obtained with the co-administration of both anti-miR‑221 and anti-miR‑222 PNAs. In addition, co-administration of R8-PNA-a221 and R8-PNA-a222 induced apoptosis of TMZ-treated T98G cells at a level higher than that obtained following singular administration of R8-PNA-a221 or R8-PNA-a222.

Reduced PTEN expression and overexpression of miR-17-5p, -19a-3p, -19b-3p, -21-5p, -130b-3p, -221-3p and -222-3p by glioblastoma stem-like cells following irradiation

Phosphatase and tensin homolog deleted on chromosome 10 (PTEN) is a tumor suppressor gene that induces cell apoptosis by inhibiting the PI3K/Akt signaling pathway. Glioblastoma (GBM) is a brain tumor that is resistant to irradiation and chemotherapy and, thus, is difficult to cure. GBM stem-like cells (GSCs) have been implicated as a cause of this resistance. microRNA (miRNA/miR) inhibits the expression of proteins. The objective of the present study was to identify miRNAs that target PTEN, which induces apoptosis, in irradiation-resistant GSCs. When the expression of miRNAs was examined in GSCs irradiated at 60 Gy using the human GBM A172 cell line, the expression of PTEN-targeting miR-17-5p, -19a-3p, -19b-3p, -21-5p, -130b-3p, -221-3p and -222-3p was significantly higher in irradiated GSCs than in non-irradiated cells, and the PTEN expression levels, as revealed by immunostaining, were lower in the irradiated GSCs than in the non-irradiated cells. These results suggested that the expression of PTEN was suppressed through the overexpression of PTEN-targeting miRNAs in GSCs following irradiation.

Regulation of expression of O6-methylguanine-DNA methyltransferase and the treatment of glioblastoma (Review)

O-6-methylguanine-DNA methyltransferase (MGMT) is an abundantly expressed nuclear protein dealkylating O⁶-methylguanine (O⁶-MG) DNA residue, thus correcting the mismatches of O⁶-MG with a thymine residue during DNA replication. The dealkylating effect of MGMT is relevant not only in repairing DNA mismatches produced by environmental alkylating agents promoting tumor pathogenesis, but also when alkylating molecules are applied in the chemotherapy of different cancers, including glioma, the most common primary tumor of the central nervous system. Elevated MGMT gene expression is known to confer resistance to the treatment with the alkylating drug temozolomide in patients affected by gliomas and, on the contrary, methylation of MGMT gene promoter, which causes reduction of MGMT protein expression, is known to predict a favourable response to temozolomide. Thus, detecting expression levels of MGMT gene is crucial to indicate the option of alkylating agents or to select patients directly for a second line targeted therapy. Further study is required to gain insights into MGMT expression regulation, that has attracted growing interest recently in MGMT promoter methylation, histone acetylation and microRNAs expression. The review will focus on the epigenetic regulation of MGMT gene, with translational applications to the identification of biomarkers predicting response to therapy and prognosis.

MiR-20a Induces Cell Radioresistance by Activating the PTEN/PI3K/Akt Signaling Pathway in Hepatocellular Carcinoma

PURPOSE

To investigate the role of miR-20a in hepatocellular carcinoma (HCC) cell radioresistance, which may reveal potential strategies to improve treatment.

METHODS AND MATERIALS

The expression of miR-20a and PTEN were detected in HCC cell lines and paired primary tissues by quantitative real-time polymerase chain reaction. Cell radiation combined with colony formation assays was administrated to discover the effect of miR-20a on radiosensitivity. Bioinformatics prediction and luciferase assay were used to identify the target of miR-20a. The phosphatidylinositol 3-kinase inhibitor LY294002 was used to inhibit phosphorylation of Akt, to verify whether miR-20a affects HCC cell radioresistance through activating the PTEN/PI3K/Akt pathway.

RESULTS

MiR-20a levels were increased in HCC cell lines and tissues, whereas PTEN was inversely correlated with it. Overexpression of miR-20a in Bel-7402 and SMMC-7721 cells enhances their resistance to the effect of ionizing radiation, and the inhibition of miR-20a in HCCLM3 and QGY-7701 cells sensitizes them to it. PTEN was identified as a direct functional target of miR-20a for the induction of radioresistance. Overexpression of miR-20a activated the PTEN/PI3K/Akt signaling pathway. Additionally, the kinase inhibitor LY294002 could reverse the effect of miR-20a-induced radioresistance.

CONCLUSION

MiR-20a induces HCC cell radioresistance by activating the PTEN/PI3K/Akt pathway, which suggests that miR-20a/PTEN/PI3K/Akt might represent a target of investigation for developing effective therapeutic strategies against HCC.

Predictive and Prognostic Roles of Abnormal Expression of Tissue miR-125b, miR-221, and miR-222 in Glioma

Glioma is the most prevalent primary brain tumors in adults. In addition to the high incidence and mortality rate, the 5-year survival rate of glioma is also extremely low. MicroRNAs (miRNAs), as a class of small non-coding RNAs, may play an important role in carcinogenesis. It was also proposed that miRNAs might also be associated with glioma diagnosis and prognosis. In this study, we aimed at investigating the predictive and prognostic values of miR-125b, miR-221, and miR-222 in glioma and, hopefully, to provide some evidence for novel therapy of glioma. Tissue specimens were obtained from tumor tissue and adjacent non-tumor tissue. RNA was extracted and qRT-PCR was performed with U6 being the internal control. Receiver-operating characteristic (ROC) curves were constructed, and the area under the ROC curves (AUC) was calculated to evaluate the significance of candidate miRNAs in distinguishing glioma tumor tissues and adjacent normal tissues. Survival curves of Kaplan-Meier method were constructed for both high expression group and low expression group, and the difference between curves was evaluated by log-rank test. All the statistical analyses were performed using Stata version 12.0 software, and graphs were generated by GraphPad Prism 5.0. The significance of miR-125b, miR-221, and miR-222 expression level in distinguishing glioma tumor from adjacent non-tumor tissues was further validated. Combination of miR-125b, miR-221, and miR-22 was significantly superior compared to the clinical standard of using these miRNAs alone. A clear demarcation was shown by survival analysis between patients with high miR-125b, miR-221, and miR-222 expression and patients with poor prognosis. Similarly, panel of these miRNAs could play a better prognostic role in glioma. In this study, we confirmed the significance of miR-125b, miR-221, and miR-222 in distinguishing glioma tumor from adjacent non-tumor tissues. Higher expressions of miR-125b and miR-222 have also been proved to be associated with glioma. Furthermore, glioma patients with higher miR-125b, miR-221, and miR-222 expression were manifested to have poorer prognostic status, which might be attributed to their attenuated sensitivity to chemotherapy and radiotherapy.

A functional screen identifies miRs that induce radioresistance in glioblastomas

The efficacy of radiotherapy in many tumor types is limited by normal tissue toxicity and by intrinsic or acquired radioresistance. Therefore, it is essential to understand the molecular network responsible for regulating radiosensitivity/resistance. Here, an unbiased functional screen identified four microRNAs (miR1, miR125a, miR150, and miR425) that induce radioresistance. Considering the clinical importance of radiotherapy for patients with glioblastoma, the impact of these miRNAs on glioblastoma radioresistance was investigated. Overexpression of miR1, miR125a, miR150, and/or miR425 in glioblastoma promotes radioresistance through upregulation of the cell-cycle checkpoint response. Conversely, antagonizing with antagomiRs sensitizes glioblastoma cells to irradiation, suggesting their potential as targets for inhibiting therapeutic resistance. Analysis of glioblastoma datasets from The Cancer Genome Atlas (TCGA) revealed that these miRNAs are expressed in glioblastoma patient specimens and correlate with TGFβ signaling. Finally, it is demonstrated that expression of miR1 and miR125a can be induced by TGFβ and antagonized by a TGFβ receptor inhibitor. Together, these results identify and characterize a new role for miR425, miR1, miR125, and miR150 in promoting radioresistance in glioblastomas and provide insight into the therapeutic application of TGFβ inhibitors in radiotherapy.

IMPLICATIONS

Systematic identification of miRs that cause radioresistance in gliomas is important for uncovering predictive markers for radiotherapy or targets for overcoming radioresistance.

Influence of peripheral whole-blood microRNA-7 and microRNA-221 high expression levels on the acquisition of castration-resistant prostate cancer: evidences from in vitro and in vivo studies

Prostate cancer (PC) is the more frequently diagnosed neoplasia in men in developed countries. The evolution of PC to castration-resistant prostate cancer (CRPC) represents real problems of clinical management, in consequence to the limited therapeutic options. MicroRNAs (miRNAs) are small noncoding RNAs that play an important role in gene expression and function regulation. The increased evidence that miRNAs are involved in cancer development and progression has made them potential biomarkers for cancer diagnosis, prognosis, and aggressiveness. Our purpose was to identify a miRNA expression profile associated with the development of CRPC. We firstly observed a miRNA expression profile differentially expressed between the castration-resistant (CR) PC3 cell line and the hormone-sensitive LnCaP cell line, where miR-7, miR-221, and miR-222 were upregulated in PC3 (11.3-fold increase, P = 0.012; 11.3-fold increase, P = 0.002; 8.6-fold increase, P = 0.002, respectively). We also observed that the trend of miR-1233 expression levels was higher in PC3 (3.7-fold increase, P = 0.057). These miRNAs differentially expressed in vitro were studied in a peripheral whole-blood samples from PC patients. We observed that patients presenting an early CR acquisition (≤ 20 months) had higher expression levels of miR-7 and miR-221 (P = 0.034 and P = 0.036, respectively). Furthermore, we found that patients diagnosed with high-Gleason score tumors and presenting simultaneous higher miR-7 expression levels have a significant reduce time to CR compared with patients who present lower miR-7 expression levels (11 vs. 51 months, log-rank test P = 0.004). We also found that patients diagnosed with high-Gleason score tumors and higher expression levels of miR-221 have an early CRPC compared to patients with lower miR-221 expression levels (10 vs. 46 months, log-rank test P = 0.012). We observed a significantly lower overall survival in patients with higher peripheral whole-blood expression levels of miR-7 (28 vs. 116 months, log-rank test P = 0.001). Our results suggest that miR-7 and miR-221 peripheral whole-blood expression levels can be potential predictive biomarkers of CRPC development.

miR-17 inhibitor suppressed osteosarcoma tumor growth and metastasis via increasing PTEN expression

MicroRNAs (miRNAs) play essential roles in cancer development and progression. Here, we investigated the role of miR-17 in the progression and metastasis of osteosarcoma (OS). miR-17 was frequently increased in OS tissues and cell lines. Inhibition of miR-17 in OS cell lines substantially suppressed cell proliferation, migration, and invasion. Phosphatase and tensin homolog (PTEN) was identified as a target of miR-17, and ectopic expression of miR-17 inhibited PTEN by direct binding to its 3'-untranslated region (3'-UTR). Expression of miR-17 was negatively correlated with PTEN in OS tissues. Together, these findings indicate that miR-17 acts as an oncogenic miRNA and may contribute to the progression and metastasis of OS, suggesting miR-17 as a potential novel diagnostic and therapeutic target of OS.