MicroRNA-886-3P functions as a tumor suppressor in small cell lung cancer

ABSTRACT

Small cell lung cancer (SCLC) is a highly aggressive disease and miRNAs may play an important role in modulating SCLC progression. We have previously screened 924 miRNAs and found that miR-886-3P was negatively associated with SCLC survival. In the current study, we further investigated the role of miR-886-3P mimic in regulating SCLC cell phenotypic alteration in vitro and xenograft tumor formation in vivo. We found that transfection of miR-886-3P mimic significantly inhibited SCLC cell proliferation, migration, and colony formation, and induced mesenchymal-epithelial transition (MET) by suppressing TGF-ß1 synthesis in vitro. Furthermore, intra-tumor injection of miR-886-3P mimic lead to necrosis and suppression of tumor invasion to the surrounding tissue in the subcutaneous xenograft tumor, and intra-vein injection of miR-886-3P mimic suppressed xenograft lung cancer growth in vivo. These findings suggested that miR-886-3P functions as a tumor suppressor in SCLC and thus, it might be a potential therapeutic molecule in the treatment of lung cancer.

Keywords:

• Small cell lung cancer
• miRNAs
• miR-886-3P
• TGF-ß1
• aggressive disease
• fetal bovine serum
• pGL3-luciferase
• cancer biology

Introduction

Lung cancer is one of the most aggressive malignant cancers in the world. Small cell lung cancer (SCLC) accounts for approximately 15% of all newly diagnosed lung cancer cases.¹ Based on whether a SCLC can be safely treated with definitive radiation fields, the American Veterans Administration Lung Study Group (VALG) defines SCLC stages as limited disease (LD) and extensive disease (ED).² Platinum-based chemotherapy in combination with radiotherapy remains as the main therapeutic strategy for SCLC.³ However, despite extreme sensitivity to chemotherapy and radiotherapy, approximately 67% of newly diagnosed patients have ED, with median progression-free survival of 5.5 months and median overall survival of 6–12 months,⁴ and 5-year survival rates of 5–10%.^5,6

SCLC is often found early metastasis when it is diagnosed. Many factors may contribute to the aggressive phenotype of SCLC. In this content, it has been reported that miRNAs play an important role in phenotypic alteration of cancer cells through regulating epithelial-mesenchymal transition (EMT.^7–10 EMT process involves distinct genetic and epigenetic alterations, and shifted expression of several biomarkers including E-cadherin, N-cadherin and vimenti.¹¹ The EMT process has been described in different kinds of human malignant tumors including breast cancer,¹² non-small cell lung cancer,¹³ colon cancer,¹⁴ and SCLC.¹⁵ TGF-ß1 has been known to induce EMT in variety kinds of cells including lung cancer cells.¹⁶

Due to limited therapeutic outcomes in SCLC, over the past few years, there has been a paradigm shift in cancer treatment from non-specific therapy to targeted therapies including immunotherapy and biological therapy.^17,18 In this regard, several miRNAs have been reported to suppress or promote lung cancer cell survival or death.^19–22 Consistent with these reports, we have previously reported that miR-886-3Pwas associated with survival of SCL.²³ In the current study, we further investigated role of miR-886-3P in regulating small cell lung caner cell proliferation, migration, colony formation, mesenchymal-epithelial transition (MET), and in vivo xenograft tumor formation and growth.

Materials and methods

Cell culture and transfection of exogenous mirnas

Human small cell lung cancer cell lines, NCI-H446 and NCI-H1688, were obtained from Peking Union Medical University (Beijing, China) and maintained in RPMI 1640 medium (GIBCO, USA) supplemented with 10% fetal bovine serum (FBS, GIBCO, USA) and antibiotics at 37°C and 5% CO₂ atmosphere. Mimic of miR-886-3P and control miRNA were purchased from Ribobio (Guangzhou, China) and the plasmid was synthesized by Generay (Shanghai, China).

Transfection of miRNA mimic was carried out using Lipofectamine 2000 following the manufacture’s instruction (Invitrogen, USA).

Immunoblotting

Cells were harvested with lysis buffer and briefly sonicated. Total protein concentration was measured with BAC Protein Assay Kit (PPLYGEN, Beijing, China). Samples were mixed with 2 times concentrated sample loading buffer and denatured by heating at 95°C followed by cooling on ice. A total of 50µg protein was loaded into each lane and separated by SDS-PAGED (10%). After transferring to nitrocellulose membrane (GE Health), it was blocked with 5% skim milk for 2 h at room temperature. Primary antibodies of anti-E-cadherin, anti-N-cadherin, anti-Vimentin, anti-TGF-ß1 (Santa Cruz Biotechnology, Santa Cruz, USA), and anti-ß-actin (Sigma-Aldrich, St. Louise, USA) were allowed to react for overnight at 4°C. After washing and incubation with appropriate HRP-conjugated 2^nd antibody for 1h at room temperature, blotting signal was analyzed using the Image Quant LAS 4000 (GE Healthcare, Life Science).

Luciferase reporter assay

The wild type and mutant 3ʹ-UTR of human TGF-ß1 was synthesized and cloned into the pGL3-luciferase reporter plasmid (Promega, Madison, USA). Cells were then co-transfected with wild type or mutated TGF-ß1 vector, and miR-886-3P mimic or control mimic, using Lipofectamine 2000. Renilla luciferase vector were co-transfected to characterize the transfection efficiency. After 48 h, cells were harvested and luciferase activity was assessed using the Dual-Luciferase reporter assay system (Promega, Madison, USA). Firefly luciferase activity was normalized to renilla luciferase activity.

Xenograft tumor formation and treatment with mirna mimic

Nude mice (3–4 weeks old) were purchased from Beijing Vital River Company (Beijing, China). Mice were randomly assigned to experimental group and control group. For the xenograft tumor formation experiment, 2 × 10⁶ NCI-H446 cells that stably expressing miR-886-3P or NCI-H446 cells lacking of miR-886-3P were injected subcutaneously. After 4 weeks, mice were sacrificed and tumor was weighed. Tissues were fixed with formalin and sections of paraffin embedded tissues were used for histology and immunohistochemistry assessment.

For the miRNA mimic therapeutic experiment, 2 × 10⁶ luciferase-labeled NCI-H446 cells were injected either subcutaneously or through tail veins. After formation of the xenograft tumors, equal amount of miR-886-3P mimic or control mimic were injected intra-tumor or through the tail vein. Two weeks later, mice were sacrificed, and tumors were weighed followed by fixing with formalin. Sections of paraffin embedded tumor tissue were used for histology and immunohistochemistry examination.

Immunocytochemistry

NCI-H446 cells were plated on poly-L-lysine coated coverslips in a 6-well tissue culture plate and transfected with either control miRNA mimic or miR-886-3P mimic. After fixation with 4% paraformaldehyde for 10 minutes, the cells were permeabilized with 0.1% Triton-X 100 for 15 minutes. After blocking with normal goat serum, primary antibodies including anti-E-cadherin, anti-N-cadherin, anti-TGF-ß1, and anti-vimentin (Santa Cruz Biotechnology, Santa Cruz, USA) were allowed to react overnight at 4°C. After washing, Alexa Fluor conjugated secondary antibodies (ZSGB-BIO, Beijing, China) were applied at dark for 1 hr. The coverslips were then mounted with ProLong Gold antifade with DAPI mounting medium (PPLYGEN, Beijing, China). Fluorescent images were obtained with a confocal microscope (Leica, Germany).

Histology and immunohistochemistry

All xenograft tumors were fixed with formalin for at least 24 h followed by embedding with paraffin. Serial sections of 5µm thickness from representative blocks were obtained. Sections were stained with hematoxylin and eosin (H & E) for histological examination.

For immunohistochemistry, after deparaffinization and rehydration, internal H₂O₂ was blocked with 3% H₂O₂ followed by non-specific blocking with normal goat serum. Primary antibodies were then allowed to react overnight at 4°C. After washing, appropriate HRP-conjugated secondary antibody was applied at room temperature for 1h. Expression of the target proteins was visualized using Enhance Polymer DAB Detection Kit following the manufacture’s instruction (ZSGB-BIO, Beijing, China). Images were further analyzed using Aperio Imagescope (Leica Biosystems, Germany).

Real time RT-PCR

Total RNA was extracted using TRIzol Reagent (Invitrogen Life Technologies, 15596–026). Two micrograms of total RNA were converted to complementary DNA using Superscript reverse transcriptase (Invitrogen Life Technologies, 18064–014) following the manufacturer’s instructions. RT- PCR was performed in a 20μl reaction volume according to the manufacturer’s protocol using SYBRP remix Ex Taq (Liaoning, China, RR420A).

Statistical analysis

Statistical analysis was conducted using GraphPad Prism software (GraphPad Software, La Jolla, CA, USA). Data are presented as the mean ± s.e.m. Differences in measured variables between experimental and control groups were assessed using the Student’s t-test. P values were calculated, and minimum statistical significance was accepted at P < 0.05, NS, not significant, *P < 0.05, **P < 0.01.

Results

Overexpression of mir-886-3p resulted in phenotypic alteration of SCLC cells

We have previously reported that miR-886-3P was down-regulated in SCLC and thus, we hypothesized that lack of miR-886-3P may be associated with aggressive phenotype of small cell lung cancer. In the current study, therefore, exogenous mimic of miR-886-3P was transfected into the two cell lines of small cell lung cancer, NCI-H446 and NCI-H1688. Phenotypes of the cells were then examined. As expected, expression of miR-886-3P significantly increased in the cells transfected with exogenous mimic of miR-886-3P both at mRNA (Figure 1A) and protein level (Figure 1B). Overexpression of miR-886-3P resulted in significant suppression of cell proliferation (Figure 1C), cell migration and invasion into Matrigel (Figure 1D) compared to the control cells (Figure 1E, migration in NCI-H446: 168 ± 25 vs 65 ± 10; Migration in NCI-H1688: 112 ± 20 vs 52 ± 22; invasion in NCI-446: 195 ± 36 vs 79 ± 15; invasion in NCI-H1688 132 ± 19 vs 65 ± 14, p < 0.05). In addition, ability of colony formation was also significantly reduced in the cells over-expressing miR-886-3P compared to the control cells (Figure 1F and G, NCI-H446: 148 ± 32 vs 31 ± 5; NCI-H1688: 521 ± 79 vs 209 ± 53, p < 0.05).

Figure 1. In vitro suppression of SCLC cell proliferation, migration and invasion by exogenous miR-886-3P.

Small cell lung cancer cell lines (NCI-H1688 and NCI-H446) were transfected with miR-886-3Pmimic (Mimic-886) or negative control mimic (Mimic-NC). Expression of miR-886-3P was then assessed by real-time PCR quantification (Panel A) or agarose electrophoresis analysis (Panel B). Panel C: Cell proliferation assessed by RTCA MP system. Green line: cells transfected with Mimic-NC; Red line: cells transfected with Mimic-886. Panel D: Representative image of crystal violet staining of migration and invasion of NCI-H446 and NCI-H1688 cells transfected with Mimic-NC or Mimic-866; Panel E: Quantification of cell migration and invasion expressed as Relative Cell Number of cells transfected with Mimic-886 versus the number of cells transfected with Mimic-NC. * p < 0.05 compared to the cells transfected with Mimic-NC. Panel F: Representative image of colony formation assay in the cells transfected with Mimic-NC or Mimic-886. Panel G: Quantification of the colonies expressed as number of colonies. * p < 0.05, ** p < 0.01 compared to the cells transfected with Mimic-NC.

TGF-ß1 was targeted by miR-886-3P

By searching databases including http://www.microrna.org/microrna/getTargets, we found that TGF-ß1 is a predicted target for miR-886-3P and thus effect of miR-886-3P mimic on TGF-ß1 expression was assessed. It was demonstrated by the luciferase reporter assay that TGF-ß1 promoter activity was significantly reduced in the cells transfected with miR-886-3P mimic compared to the cells transfected with negative control mimic (Figure 2A, NCI-H1688: 912 ± 149 of miR-886-3P mimic vs (2.12 ± 0.36)× 10³ of control mimic; NCI-H446: (5.54 ± 0.45) × 10³ of miR-886-3P mimic vs (1.42 ± 0.56)× 10⁴ of control mimic, p < 0.01). Furthermore, TGF-ß1 protein was significantly reduced in the small cell lung cancer cells transfected with miR-886-3P mimic compared to the cells transfected with control mimic as evidenced by immunofluorescence staining (Figure 2B and 2C) and immunoblotting (Figure 2D).

Figure 2. Effect of miR-886-3P mimic on TGF-ß1 expression by the SCLC cells.

NCI-H446 and NCI-H1688 cells were transfected with control Mimic (Mimic-NC) or miR-886-3P Mimic (Mimic-886). Effect of exogenous miR-886-3P on TGF-ß1 expression was then assessed as described in the methods. Panel A: Relative luciferase activity of the indicated TGF-ß1 reporter constructs. ** p < 0.01 compared to the cells transfected with Mir-NC. Panel B: Immunofluorescence staining of TGF-ß1. Panel C: Quantification of TGF-ß1 mRNA by real time RT-PCR. * p < 0.05 compared to the cells transfected with Mir-NC. Panel D: Immunoblotting of TGF-ß1.

Microrna-886-3p resulted in mesenchymal-epithelial transition (MET) through suppressing TGF-ß1

TGF-ß1 is known to induce epithelial-mesenchymal transition (EMT), one of the mechanisms by which cancer cell invades surrounding tissue. Since miR-886-3P targeting TGF-ß1, we further examined if miR-886-3p could induce mesenchymal-epithelial transition (MET) through suppressing TGF-ß1. As shown in Figure 3A, transfection of exogenous miR-886-3P mimic resulted in the morphological transition of the lung cancer cell lines from spindle-shape to round shape (Figure 3A). Next, miR-886-3P mimic-induced MET in small cell lung cancer cells was further examined by assessing the expression of biomarkers including E-cadherin, N-cadherin, and vimentin (Figure 3B and 3C). It was found that miR-886-3P significantly increased E-cadherin (NCI-H446: 0.49 ± 0.05 of miR-886-3P mimic vs 0.05 ± 0.01 of control mimic; NCI-H1688: 0.12 ± 0.01 of miR-886-3P mimic vs 0.03 ± 0.01 of control mimic, p < 0.05, Figure 3C), and in contrast, it significantly suppressed N-cadherin (NCI-H446: 0.02 ± 0.01 of miR-886-3P mimic vs 0.98 ± 0.06 of control mimic; NCI-H1688: 0.09 ± 0.01 of miR-886-3P mimic vs 0.75 ± 0.06 of control mimic, p < 0.05, Figure 3C) and vimentin (NCI-H446: 0.03 ± 0.01 of miR-886-3P mimic vs 0.02 ± 0.01 of control mimic; NCI-H1688: 0.01 ± 0.01 of miR-886-3P mimic vs 0.82 ± 0.04 of control mimic, p < 0.05, Figure 3C), which was partially or completely blocked in the presence of TGF-ß1 as evidenced by immunoblotting (Figure 3B and 3C) or by confocal immunofluorescence staining (Figure 3D). Consistently, expression of miR-886-3P in the SCLCs resulted in significant up-regulation of E-cadherin (NCI-H446: 1.95 ± 0.21 of miR-886-3P mimic vs 1.49 ± 0.05 of control mimic; NCI-H1688: 1.04 ± 0.02 of miR-886-3P mimic vs 6.49 ± 0.87 of control mimic, p < 0.05, Figure 3E), but down-regulation of N-cadherin (NCI-H446: 4.88 ± 0.92 of miR-886-3P mimic vs 9.27 ± 0.29 of control mimic; NCI-H1688: 3.65 ± 0.21 of miR-886-3P mimic vs 5.62 ± 0.40 of control mimic, p < 0.05, Figure 3E) and vimentin (NCI-H446: 6.55 ± 2.55 of miR-886-3P mimic vs 3.12 ± 0.06 of control mimic; NCI-H1688: 5.50 ± 1.03 of miR-886-3P mimic vs 9.32 ± 1.25 of control mimic, p < 0.05, Figure 3E).

Figure 3. Effect of miR-886-3P mimic on TGF-ß1-induced EMT and expression of biomarkers of EMT.

SCLC cells were transfected with either miR-886-3P mimic or control mimic followed by treated with or without TGF-ß1. The expression of EMT biomarkers was assessed as described in the methods. Panel A: Comparison of cell morphology following transfection of Mimic-NC or Mimic-886. Panel B and C: Immunoblotting of N-cadherin, E-cadherin and vimentin (B) and semi-quantification of the protein level versus ß-actin (C). * p < 0.05, ** p < 0.01 compared to Mimic-NC. Panel D: Representative image of immunofluorescence staining of N-cadherin and E-cadherin in the NCI-H446 cells transfected with either Mimic-NC or Mimic-886. Panel E: Quantification of mRNAs of N-cadherin, E-cadherin, and vimentin. * p < 0.05, ** p < 0.01 compared to Mimic-NC.

Effect of mir-886-3p mimic on subcutaneous tumor formation and growth

To further determine whether miR-886-3P affect tumor growth in vivo, a xenograft tumor model was established by subcutaneously injecting NCI-H446 cells into the nude mice. As expected, xenograft tumors formed by the cells transfected with miR-886-3P mimic were significantly smaller and less weight in average compared to that formed by the cells transfected with control mimic (Figure 4A and 4B, 0.755 ± 0.219 × 10³ mg of miR-886-3P mimic vs 1.42 ± 0.484 × 10⁴ mg of control mimic, p < 0.05). Stable expression of miR-886-3P in the xenograft tumor was confirmed by in situ hybridization (Figure 4C). Moreover, effect of miR-886-3P mimic on the expression of EMT/MET biomarkers in the xenograft tumor tissues was assessed by immunocytochemistry. As shown in Figure 4D, N-cadherin and vimentin were highly expressed in the tumors formed by the cells transfected with control mimic, while they were significantly suppressed in the tumors formed by the cells transfected with miR-886-3P mimic.

Figure 4. Subcutaneous tumor formation and growth by the SCLC cells transfected with miR-886-3P mimic or control mimic.

NCI-H446 cells were transfected with either Mimic-NC or Mimic-886 followed by subcutaneous injection into the nude mice as described in the methods. Panel A: Representative image of tumor formation and growth. Panel B: Comparison of tumor weight in the two groups (n=6 each group). * p < 0.05. Panel C: Representative images of in situ hybridization of human miR-886-3P (has-miR-886-3P) or U6 in the sections of subcutaneous tumors formed by the cells transfected with either Mimic-NC or Mimic-886. Panel D: Immunohistochemistry staining of N-cadherin and vimentin in the sections of subcutaneous tumors formed by the cells transfected with either Mimic-NC or Mimic-886.

Antitumor effect of mir-886-3p mimic delivered locally or systemically

Next, in order to examine antitumor effect of miR-886-3P, following two different strategies were applied. First, NCI-H446 cells were injected subcutaneously and allowed to form xenograft tumors. The cholesterol conjugated miR-886-3P mimic or control mimic was then locally injected into the subcutaneous tumors. As shown in Figure 5A, intra-tumor injection of miR-886-3P mimic resulted in necrosis of the tumor tissue as well as suppression of intra-muscular invasion of the tumor. Consistent with the suppression of invasion, expressions of N-cadherin and TGF-ß1 were significantly reduced in the tumor injected with miR-886-3P mimic compared to that injected with control mimic (Figure 5B).

Figure 5. In vivo effect of miR-886-3P mimic on xenograft tumor formation, growth, and invasion.

Panel A and B: Cholesterol conjugated miR-886-3P agomir or negative control (NC) agomir were injected into the subcutaneous xenograft tumors as described in the methods. Sections of tumor were stained H&E followed by assessing necrotic foci and muscular tissue invasion (A). Expression of E-cadherin, N-cadherin, and TGF-ß1 was assessed by immunohistochemistry (B). Panel C and D: Luciferase labeled NCI-H446 cells were injected into mice through tail veins. After tumor formation, cholesterol conjugated miR-886-3P agomir or negative control (NC) agomir were injected into the mice through tail veins as described in the methods. Intensity of luciferase activity in the lung cancer was obtained by Xenogen Corporation Optical in vivo imaging (C). Tumor histology and TGF-ß1 expression in the tumors and lung tissue were examined as described in the methods (D).

Second, luciferase-labeled NCI-H446 cells were injected into the tail veins and established a model of lung metastasis tumor. The cholesterol conjugated miR-886-3P mimic or control mimic was then systemically delivered by injecting into the tail veins. As shown in Figure 5C, the size of metastatic lung cancer was significantly smaller in the mice received cholesterol conjugated miR-886-3P mimic than in the mice injected with control mimic as evidenced by lung cancer luciferase imaging. Histological examination and immunohistochemistry further confirmed that systemic delivery of miR-886-3P mimic resulted in suppression of metastatic lung xenograft tumor growth although expression of TGF-ß1 was not significantly affected by the miR-886-3p mimic (Figure 5D).

Discussion

In the current study, we investigated the effect of miR-886-3P in suppressing proliferation, migration and formation of xenograft tumor by the small cell lung cancer (SCLC) cell lines. We found that transfection of exogenous miR-886-3P mimic resulted in alteration of SCLC cells from aggressive to non-aggressive phenotype, which includes reduced proliferation, migration, and colony formation. In addition, expression of TGF-ß1, N-cadherin, and vimentin was significantly suppressed, and in contrast, expression of E-cadherin was significantly increased in the cells overexpressing miR-886-3P. Furthermore, subcutaneous xenograft tumor formation and growth was significantly reduced in the SCLC cells containing exogenous miR-886-3P mimic compared to the cells transfected with control mimic. Intra-tumor or intra-venous injection of exogenous miR-886-3P mimic resulted in necrosis of the tumor tissue and suppression of the tumor invasion into the lung tissues. These findings suggested that lack of miR-886-3P may contribute the aggressive phenotype of small cell lung cancer.

Small cell lung cancer is a highly aggressive disease and most of the patients die of metastasis and recurrence. It has been reported that about 25% of small cell lung cancer patients have distance metastases at initial diagnosis.²⁴ While multiple factors may be associated with early metastasis of SCLC, recent studies indicated that miRNA be one of the crucial factors that contribute to the aggressive phenotype of SCLC.^25,26 Consistently, with limited number of cases, we have also previously reported that miR-886-3P might be associated with poor prognosis of SCL.²³ In the current study, we further demonstrated that transfection of miR-886-3P mimic into the SCLC cell lines resulted in suppression of cell proliferation, migration and formation of subcutaneous xenograft tumor, suggesting miR-886-3P could modulate phenotype of small cell lung caner.

Epithelial-mesenchymal transition (EMT) is a crucial step for a cancer cell migration and aggressive invasion to the surrounding tissue or metastasis distance organs.^27,28 Accumulating evidence from in vitro studies has demonstrated that TGF-ß1 plays an important role in EMT induction in variety kinds of cells including lung cancer cells.^11,16,29 Blockade of TGF-ß1 synthesis and its biological action in tumor and surrounding tissue, therefore, may result in suppression of EMT and consequent migration of the tumor cells. In support of this concept, the current study demonstrated that exogenous miR-886-3P mimic not only inhibited TGF-ß1 production by the SCLC cell lines, but also morphological alteration of SCLC cells from spindle-shape into round shape cells, a phenomenon of mesenchymal-epithelial transition (MET). Furthermore, miR-886-3P transfection in the SCLC cells leads to down-regulation of N-cadherin and vimentin, typical biomarkers of mesenchymal type and aggressive tumor cells; and in contrast, up-regulation of E-cadherin, a biomarker of epithelial cells. In addition, effect of miR-886-3P mimic on the alteration of EMT/MET biomarkers was partially blocked by the exogenous TGF-ß1. These findings indicated that TGF-ß1 play a role in the process of EMT and tumor cell migration, and that miR-886-3P suppress EMT and tumor cell migration partially through regulating TGF-ß1 synthesis and its biological function on EMT of the SCLC cells.

Subcutaneous xenograft tumor formation in nude mice is often used as an in vivo model of tumor stud.³⁰ Using this model, for the first time, we demonstrated that miR-886-3P mimic could inhibit subcutaneous xenograft tumor formation, growth, and invasion into the surrounding tissue, as well as significant suppression of N-cadherin and vimentin expression in the xenograft tumor tissue. In addition, local injection of miR-886-3P mimic into the subcutaneous xenograft tumor resulted in topical necrosis of the subcutaneous tumor and suppression of TGF-ß1 and N-cadherin expression. Furthermore, intravenous injection of miR-886-3P mimic could dramatically reduce the tumor size of metastatic xenograft lung cancer. These findings further suggested that miR-866-3P could be used as a therapeutic molecule that could be delivered either locally (intra-tumor injection) or systemically (intravenous injection).

Taken together, the current study demonstrated that exogenous miR-886-3P could lead to phenotypic alteration of small cell lung cancer cells from aggressive and mesenchymal phenotype into non-aggressive epithelial cell type as evidenced by down-regulation of N-cadherin and vimentin, and up-regulation of E-cadherin. Over-expression of miR-886-3P in the SCLC cell lines resulted in suppression of cell proliferation, migration, colony formation, and TGF-ß1 production. Injection of miR-886-3P mimic could suppress xenograft tumor formation, growth and invasion into the surrounding tissue. The findings of the current study suggested that miR-886-3P could be a biological therapeutic tool, which could be delivered either locally or systemically, in the treatment of small cell lung cancer.

Additional information

Funding

This study was supported by National Natural Science Foundation of China [No. 81572971].