Cell culture
4T1 cell line was obtained from the cell bank of Pasteur Institute of Iran (C604). The cells were cultured in high glucose Dulbecco’s Modified Eagle’s Medium (DMEM) containing 10% FBS (fetal bovine serum) and 2% Penicillin-Streptomycin (all from Gibco, USA) in humidified atmosphere of 5% CO2 at 37°C.
Induction of syngeneic animal model of breast cancer
Female BALB/c mice weighing 20 to 25 gram obtained from Royan institute (Iran). The animals were housed in cages at 12-h photoperiod while they had free access to food and water. All animal experiments were in compliance with the relevant laws, and this study was approved by the Ethics Committee of Shahroud University of Medical Sciences (registration number: IR.SHMU.REC.1400.112). 4T1 cells were subcutaneously injected to the flank (or the right hind limb) of the mice (105 cells suspended in 100 μL PBS) using an insulin syringe with 32G needle. The mice were monitored daily for the appearance and behavior characteristics.
Brain metastatic and primary breast tumor cell extraction
Primary and metastatic tumor cell extraction, was performed according to our and other group previous works[22-25]. Briefly primary tumor and brain of cancerous mice were excised after 35 days of tumor induction in mice, and surface blood was removed by rinsing it in PBS. After mincing with scissors, fragments were placed to 50 ml conical tube. For enzymatic digestion, primary tumor and the brain were digested in 10 mg ⁄ ml collagenase type IV at 37°C for 75 min on a platform rocker. All enzymes were purchased from Sigma (St Louis, MO, USA). The digested organ filtered through 70-um cell strainers, and washed with PBS. In the next step, washed cells were resuspended in medium containing 10% FBS, 100 U/ml Penicillin, and 100 ug/ml Streptomycin (all from Gibco, USA). Ultimately, the cells were cultured at 37°C in 5% CO2.
Quantification of MMP-2 and MMP-9 by RT-qPCR
Primary and brain metastatic tumor cells (1×104) were seeded in each well of 24-well plates in complete medium. After 48 hours Total RNA was extracted from these cells using QIAzol Lysis Reagent (QIAGEN). The quality, yield, and size of extracted RNA were analyzed using spectrophotometry (NanoDrop-ThermoFisher) and electrophoresis. The first strand cDNA synthesis was performed using reverse transcription system (Easy cDNA Synthesis Kit for RNA or mRNA to cDNA - pars tous). Real-time PCR procedure was executed based on the 1 ul cDNA in all samples. Quantization of all gene transcripts was done by SYBR Green Real time PCR Master Mix (Amplicon A/S, Denmark) using StepOnePlus™ Real-Time PCR System, according to the manufacturer’s instruction. The amplification procedure was as follows: 1 cycle of 95°C for 15 min, 40 cycles of 95°C for 30 sec, 60°C for 30 sec, and 72°C for 30 sec. The exact mRNA expression was normalized to the expression level of GAPDH. Relative changes of gene expression were calculated by the following formula, and the data was represented as fold up-regulation/down-regulation.
Fold change = 2-ΔΔCt, where ΔΔCt = [Ct of MMPS (in treated cells) - Ct of GAPDH (in treated cells)] - [Ct of MMPS (in control cells) - Ct of GAPDH (in control cells)].
Primers were designed using AlleleID version 6 software (Premier Biosoft Inc.).
The used primers are as follows:
For MMP-2, Forward 5′-TTTATTTGGCGGACAGTGAC-3′, Reverse 5′- AGTTAAAGGCAGCATCTACTTG -3′;
For MMP-9, Forward 5'-TCCAGTATCTGTATGGTCGTG-3′, Reverse 5′- CATAGTGGGAGGTGCTGTC -3′;
For GADPH, Forward 5′-CCTGGAGAAACCTGCCAAGTA-3′, Reverse 5′-GGCATCGAAGGTGGAAGAGT -3′.
Zymography
Zymography was performed on 9% polyacrylamide gels that had been cast in the presence of gelatin. Briefly, samples (100 μl) were resuspended in loading buffer and separated on a 9% SDS-PAGE gel containing 0.5 mg/ml gelatin without prior denaturation. After electrophoresis, the gels were washed to remove SDS and incubated for 30 min at room temperature in a renaturing buffer (50 mM Tris, 5 mM CaCl2, and 1% Triton X-100). The gels were incubated for 48 h at 37°C in a developing buffer (50 mM Tris-HCl [pH 7.8], 5 mM CaCl2, 0.15 M NaCl, and 1% Triton X-100) and then stained with Coomassie Brilliant Blue G-250, destained in 30% methanol, and flooded with 10% acetic acid to detect gelatinase secretion.
Statistical analysis
Results are expressed as the mean ± standard deviation. Data were analyzed with GraphPad Prism statistical software 6.0 (GraphPad Software, La Jolla, CA, USA) using Paired Samples t Test. P <0.05 was considered statistically significant.