Home Nanotechnology TiO2 nanoparticles promote tumor metastasis by eliciting pro-metastatic extracellular vesicles | Journal of Nanobiotechnology

TiO2 nanoparticles promote tumor metastasis by eliciting pro-metastatic extracellular vesicles | Journal of Nanobiotechnology

TiO2 nanoparticles promote tumor metastasis by eliciting pro-metastatic extracellular vesicles | Journal of Nanobiotechnology



TiO2 NPs have been obtained from Deke Daojin Science (Beijing, China). The first dimensions and shapes of the NPs have been noticed by Hitachi H-7500 transmission electron microscope (TEM, Jeol, Japan).

Cell cultures

Human umbilical vein endothelial cells (HUVECs) have been freshly remoted from umbilical cords and cultured in endothelial cell development medium (ECGM) (Promocell, Germany) supplemented with 5% FBS, 5 ng/mL epidermal development issue, 10 ng/mL fundamental fibroblast development issue, 0.5 ng/mL vascular endothelial development issue, 20 ng/mL insulin-like development issue, and 0.2 μg/mL hydrocortisone.

Human breast most cancers cells MDA-MB-231-Luc (American Kind Tradition Assortment) and MCF-7 (American Kind Tradition Assortment) have been cultured in DMEM supplemented with 10% fetal bovine serum (FBS) and 1% penicillin–streptomycin. All cells have been cultured in line with the directions.

EVs isolation and characterization

EVs have been remoted from tumor cells-derived conditioned media by sequential ultracentrifugation. MDA-MB-231 cells have been cultured in DMEM supplemented with 10% EV-depleted FBS for 48 h. Then the conditioned media have been collected, centrifuged at 500g for five min, 2000g for 10 min, and 16,800g for 20 min at 4 °C to take away lifeless cells and particles. The supernatants have been handed by way of a 0.22 μm filter machine (Merck, Germany), after which ultracentrifuged at 130,000g for 70 min at 4 °C. The pellets have been washed with PBS, adopted by ultracentrifugation at 130,000g for 70 min once more. The ensuing EVs have been dissolved in PBS and saved at − 80 °C.

The ready EVs have been confirmed utilizing transmission electron microscopy (TEM) and western blot. For TEM, purified EVs have been positioned on the carbon-coated 200 mesh grids to dry. The grids have been then stained with 2% uranyl acetate for 30 s and noticed utilizing a Hitachi H-7500 TEM (Jeol, Japan).

The protein content material of ready EVs have been measured utilizing the BCA protein assay reagent equipment (Beyotime, China). The dimensions and focus have been measured by Nanoparticle Monitoring Evaluation (NTA) (Nanosight NS300; Malvern Devices, UK). For EVs labeling, purified EVs have been labeled with PKH67 Inexperienced dye (Merck, Germany) in line with producer’s directions. Then, the labeled EVs have been collected by ultracentrifugation and resuspended in PBS.

Immunofluorescence staining

Cells have been fastened with pre-cooled 4% paraformaldehyde for 10 min and washed with PBS. The cells have been then incubated with Triton X-100, and blocking buffer in PBS containing 5% BSA was added for 30 min. Subsequently, the cells have been probed in a single day with main antibodies, adopted by 1 h incubation with Alexa Fluor-conjugated secondary antibody. The next main antibodies have been used: CD31 (Proteintech, 11,265-1-AP, 1:200 dilution), VMF (Proteintech, 27,186-1-AP, 1:50 dilution), VE-cadherin (CST, 2158S, 1:1000 dilution), ZO-1 (Cell Signaling, #8193, 1:1000 dilution), S1PR1 (Proteintech, 55,133-1-AP, 1:200 dilution), LC3 (Proteintech, 14,600-1-AP, 1:500 dilution). DAPI (Beyotime, China) was used to stain the nuclei with out mild for 15 min. To visualise the actin filaments, cells have been fastened, permeabilized and stained with TRITC phalloidin (Yeasen, China). The stained samples have been noticed by a confocal laser scanning microscope (IX5-RFACA; Olympus, Japan).

RNA interference and plasmids

The miR-301a-3p inhibitor, mimics and damaging management (NC) have been synthesized by GenePharma (Shanghai, China). The sequences of inhibitor and miRNA mimics referred above have been listed in Extra file 1: Desk S1. The vectors overexpressing miR-301a-3p and inhibiting miR-301a-3p have been constructed and produced. The cells together with 293 T cells, HUVECs, and MDA-MB-231 cells have been transfected above talked about plasmids with Lipofectamine™ 3000 (Invitrogen, USA) and have been used for additional experiments 24 h–48 h, respectively.

Quantitative RT-PCR

Complete RNAs have been extracted from cells or EVs utilizing Trizol reagent (Invitrogen, USA) in line with the producer’s instruction. Thereafter, extracted RNA was reverse transcribed through the use of PrimeScript RT Grasp Combine equipment for cDNA (TaKaRa, Japan). qRT-PCR was then carried out through the use of SYBR Inexperienced PCR Grasp Combine (TaKaRa, Japan) on Utilized Bio-systems 7500 Quick Actual-Time RCR System (Utilized Biosystems, USA). Every pattern was carried out in triplicate and the relative transcription ranges of goal genes have been normalized to GAPDH or U6 (for miRNA). The sequences of all indicated primers are offered in Extra file 1: Desk S1.

Western blot assay

The cells and EVs lysates have been extracted in RIPA lysis buffer (Beyotime, China). The protein content material within the supernatant was quantified by BCA protein assay equipment (Beyotime, China). Subsequently, equal quantities of denatured proteins have been subjected to SDS-PAGE and transferred onto nitrocellulose membranes (Millipore, USA). After blocking with 5% nonfat dry milk for 1 h, the membranes have been probed in a single day at 4 °C with diluted main antibodies. The next main antibodies have been used: Alix (Proteintech, 12,422-1-AP, 1:1000 dilution), CD9 (Proteintech, 20,597-1-AP, 1:1000 dilution), S1PR1 (Proteintech, 55,133-1-AP, 1:2000 dilution), LC3 (Proteintech, 14,600-1-AP, 1:2500 dilution), β-actin (Proteintech, 20,536-1-AP, 1:1000 dilution). After washing with TBST buffer, the membranes have been additional reprobed with IRDye-conjugated secondary antibodies (1:5000) for 1 h at room temperature. The membranes have been analyzed utilizing an Odyssey infrared imaging system (LI-COR Biosciences, USA).

Cell viability assay

Cell viability was decided by the CCK-8 assay (Beyotime, China) in line with the producer’s directions. Briefly, 5 × 103 cells have been seeded in 96-well plates and handled with EVs of various concentrations. After 24 h, 10 μl CCK-8 answer was supplemented to every properly for one more 2 h and absorbance at 450 nm was measured utilizing a microplate reader (ELx-800; BioTek Devices, USA).

Transwell permeability assay

The integrity of endothelial cell barrier was decided by quantifying the quantity of FITC-dextran (MW = 70 kDa, Merck, Germany) that handed by way of the endothelial monolayers. Briefly, 2 × 104 HUVECs have been grown on the highest properly of the transwell filters (0.4 μm pore; Corning Costar, USA) till the confluent monolayer was obtained. The cells have been uncovered to EVs (20 µg/mL) for 1 h, after which FITC-dextran (1 mg/mL) was supplemented. After EVs remedy, the FITC-dextran could possibly be transferred to the decrease compartment of transwell. FITC fluorescence alerts have been measured utilizing a microplate reader (ELx-800; BioTek Devices, USA) at 520 nm. The fluorescence sign of the remedy teams was normalized to the management group, and the leakage diploma was given.

Transendothelial invasion assay was carried out to review the consequences of endothelial cell leakage on tumor cell migration. 2 × 104 HUVECs have been first seeded on the higher properly of the transwell insert (8 μm pore; Corning Costar, USA) till confluent. Then, the HUVECs have been handled with EVs (20 µg/mL) for 1 h. Thereafter, 1 × 104 Cell-Tracker Inexperienced labeled MDA-MB-231 cells, MCF-7 cells, or Cell-Tracker Purple labeled A549 cells resuspended in serum-free media have been positioned contained in the higher chamber, respectively. Full DMEM media containing 10% FBS was positioned into the underside chamber. After 24 h, non-migrated cells within the higher chamber of transwell inserts have been eliminated with cotton buds and washed with PBS. Then, the tumor cells that invaded by way of HUVEC monolayers and caught to the decrease floor of the membrane have been fastened with 4% paraformaldehyde and calculated below a inverted fluorescence microscope (IXplore Professional; Olympus, Japan) a minimum of three random visible fields per properly.

Angiogenesis assay

For tube formation assay, matrigel matrix (100 μL/properly) was plated in 48-well plate and incubated at 37 °C for 30 min to permit the matrigel to polymerize. The EVs-treated HUVECs have been seeded on the matrigel-coated wells after which incubated for six h–12 h. The tube formation potential was decided by measuring the variety of tubes with inverted microscope (IXplore Professional; Olympus, Japan).

For aortic ring assay, thoracic aortas excised from 4- to 8-week-old mice have been eliminated extreme fats and reduce into 1–1.5 mm lengthy cross sections. Matrigel matrix (100 μL/properly) was plated in 48-well plate and incubated at 37 °C for 30 min to facilitate matrigel polymerization. Then, rings have been gently positioned onto the polymerized matrigel layer and coated with an extra matrigel (50 μL) for 30 min at 37 °C. Subsequently, ECGM medium (Promocell, Germany) was added to every properly. After 24 h incubation, the aortic rings have been incubated with ECGM conditioned medium, which included EVs derived from MDA-MB-231 cells. And the media was changed each 2 days. The variety of sprouts was noticed on day 3–5 with inverted microscope and quantified by counting all sprouts from one ring.

Microarray evaluation

The miRNA expressions of EVs derived MDA-MB-231 cells, TiO2 handled MDA-MB-231 cells have been carried out in Illumina NextSeq 500 (Illumina, USA). After extracting and quantifying whole RNA samples, the library was constructed, and the standard of the library was decided utilizing Agilent 2100 Bioanalyzer. Sequencing libraries of various samples have been combined, and single-stranded DNA was generated by denaturing with 0.1 M NaOH. Sequencing was carried out for 50 cycles utilizing a Illumina NextSeq 500 sequencer. Then, we used miRDeep2 software program to quantify recognized miRNAs and predict new miRNAs for all trimmed reads. Primarily based on CPM standardized miRNAs, the R software program edgeR was used to carry out differential expression calculations and display screen for differential miRNAs. The highest differential miRNA goal genes have been statistically analyzed, and the GO and path evaluation of the goal genes have been carried out.

Luciferase exercise assay

The wild-type (wt) and mutant (mt) 3′-UTR segments of S1PR1 have been inserted into the luciferase reporter plasmid psiCHECK-2 and amplified, respectively. Co-transfections of S1PR1 3′-UTR plasmids with miR-301a-3p mimics (50 nM) into 293 T cells or HUVECs have been achieved through the use of Lipofectamine 3000 reagent (Merck, Germany). Cell lysates have been harvested 48 h after transfection, and luciferase exercise was examined by a twin luciferase reporter assay equipment. All assays have been carried out in triplicate and every experiment was repeated 3 times.

Animal fashions

Immune-deficient NOD SCID mice (feminine, 4 weeks previous) have been bought from the Very important River Firm (Beijing, China). All animal experiments have been carried out in accordance with the Tips for Care and Use of Laboratory Animals of Jilin College and authorized by the Animal Ethics Committee of Jilin College (Changchun, China). MDA-MB-231-Luc cells (5 × 106) have been suspended in 100 μL PBS containing matrigel matrix (5 mg/mL) and transplanted into the left fourth stomach fats pad on the base of the nipple of the mouse. When the subcutaneous xenograft tumor reached ~ 100 mm3, the tumor-bearing mice have been anaesthetized and injected with 5 µg of EVs in PBS or TiO2 NPs by way of tail vein each different day for a complete of ten therapies. After 3 weeks, the mice have been administered 15 μg of luciferin intraperitoneally per gram of physique weight. And the bioluminescence depth was noticed with the IVIS Spectrum In Vivo Imaging System (PerkinElmer, USA). Then the tissue of mice have been harvested for bioluminescence imaging and histology evaluation proper after being intraperitoneally injected with luciferin.

For in vivo vascular permeability evaluation, mice have been anaesthetized and injected with 5 µg of EVs in PBS by way of tail vein each different day for a complete of ten therapies. Then 100 μL FITC-dextran (100 mg/kg) was intravenously injected into the tail vein of nude mice. After 2 h, the extreme dye was eliminated by the transcardiac perfusion, and the lungs of mice have been taken for examination. For tail vein metastasis assay, 1 × 105 MDA-MB-231 cells have been injected into the tail vein of mice at some point after the final EVs administration. After 2 weeks, mice injected with MDA-MB-231 cells have been sacrificed and lungs have been used to quantify metastatic tumor burden. To judge the metastasis, lungs have been stained with hematoxylin/eosin (HE) and screened for metastatic nodules. In the meantime, immunohistochemical staining for endothelial cell marker CD31, and tight junction protein ZO-1, was utilized to judge the extent of vascular harm attributable to EVs remedy.

Statistical evaluation

Statistical analyses have been carried out utilizing GraphPad Prism. The statistical significance was ascertained utilizing one-way ANOVA. Quantitative values of all experiments have been expressed because the imply ± SD. P < 0.05 was thought-about considerably. Statistical significance of the info was summarized as follows: *P < 0.05, **P < 0.01, ***P < 0.001.



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