Cell culture. The liver HCC cell lines, Huh7 and HepG2, and the human dermal fibroblast (HDF) were obtained from Royan Cell Bank. The cells were cultured in high-glucose Dulbecco’s modified Eagle’s medium (HGDMEM, Gibco, 11995-040) media at 37°C in a humidified incubator with 5% CO2. The culture medium was supplemented with 10% fetal bovine serum (FBS, Gibco, 16140-071), 2 mM L-glutamine (Gibco; 25030-024), 1 mM non-essential amino acids (Gibco; 11140-035) and 1% penicillin/streptomycin (Pen/Strep, Gibco; 15070-063, Gaithersburg, MD). Huh7, HepG2, and HDF were sub-cultured by trypsin/EDTA (0.25%, Gibco; 25200056). The culture media were changed every other day.
Generation of HCC-LEM. Because of providing necessary cell-cell and cell-ECM interactions, cancer cells can maintain better their phenotype in 3D condition. The sheep liver extracellular matrix (LEM) already produced in our lab (45). Briefly, sheep liver was frozen and chopped into small pieces, and subjected to mechanical agitation 2.5 hours, in distilled water. The slices were then stirred in 1% sodium dodecyl sulfate (SDS, Sigma, L3771, St. Louis, MO) at 4°C for 36 hours. Finally, decellularized pieces were stirred in deionized water at 4°C for 12 hours to remove the detergents and cellular fragments. To generate HCC-LEM, 1.5×105 Huh7 or HepG2 cells were seeded on the scaffold derived from LEM-Hydrogel. Then, both 3D constructs were cultured for 10 days.
Cell proliferation assay. To find 50% inhibitory activity (IA50s), total number of 2 × 104 cells/well were seeded in 96-well plates. At 75% – 80% confluency, cells were treated with 73 MBq of 188 Rhenium Perrhenate (188 ReO4) (PARS ISOTOPE Company, Iran). After treatment with188 ReO4 at different time points (18, 24, and 48 hours), 10 µL of ORANGU solution (Cell Guidance Systems; OR01-500) were added to each well. The plate incubated at 37°C for 2 hours. The absorbance values measured at 450 nm using a Stat Fax microplate reader (Awareness Technology, Inc., Palm City, FL). According to the kit data sheet, cell proliferation is proportional to optical density (OD).
Viability assay. Cells cultured in 2D condition and exposed to IA50 dose of 188 ReO4 at three time points, 18, 24, and 48 hours, harvested and suspended in PBS and evaluated by LIVE/DEAD® Viability/Cytotoxicity Kit (Invitrogen, L3224). The nuclei were counterstained with DAPI, and the viability assessment was visualized by green (live) or red (dead) fluorescence labelled cells using a fluorescence microscope (Olympus IX71, Tokyo, Japan).
Cell cycle analysis. Equal numbers of cells were dissociated using trypsin/EDTA (0.25%, Gibco; 25200056). Cells were fixed in 500 µL of 70% EtOH overnight at − 20°C. Fixed cells were washed and resuspended in FxCycle PI/RNase Staining Solution (ThermoFisher) at a concentration of 106 cells/ml and incubated at RT in a dark place 20 minutes before flow cytometry analysis (FACSCalibur, BD). The data were analyzed using FlowJo 10.6.2.
Apoptosis assessment with flow cytometric analysis. In 2D culture system, in order to determine the apoptosis rate in control and treatment groups after 18, 24, and 48 hours post exposure to IA50 dose, three replicates of 1x105 Huh7 or HepG2 cells were incubated with fluorescein isothiocyanate (FITC)conjugated Annexin V and propidium iodide (556547, Annexin VFITC apoptosis detection kit, BD Pharmingen; BD Biosciences) on ice for 30 min. The cells were washed three times with PBS. Then, 400 µl binding buffer was added to the cells. Additionally, the cell suspension was analyzed by FACSCalibur. The data were analyzed using BD CellQuest™ Pro software (version 5.2.1; BD Biosciences) and the percentage of apoptotic cells per group were calculated.
Quantitative reverse transcriptase–polymerase chain reaction (qPCR).To evaluate of apoptosis and radio resistance signaling pathway in Huh7 /HepG2 cells treated with IA50s at the transcriptional level, we performed qRT-PCR for p53, BAX, PTEN, and PI3K genes. RNA extractions were performed using TRIzol (Invitrogen®), and then cDNA synthesized using PrimeScript™ Reverse Transcriptase Kit (Takara Bio, Inc., Kusatsu-Shi, Japan) according to the instructions from the manufacturer. Quantitative RT-PCR reactions were performed by a real-time PCR system (Applied Biosystems StepOne instrument, Foster City, CA) using SYBR Green Master Mix (Takara Bio, Inc., SYBR Premix) and the results analyzed by StepOne software (Applied Biosystems; version 2.1). For each group, the samples were collected from three independent biological replicates. Finally, the expression levels of each target genes were normalized to GAPDH. Analysis was performed by the comparative CT Method 2−ΔΔct.
Histological and Immunofluorescence assessments. At the selected time points post-exposure from the both 3D constructs, the samples were harvested, fixed by 4% formaldehyde for overnight, and embedded in paraffin blocks. Then, 5-µm sections were prepared. To scrutinize the microstructure of the samples, H&E staining performed. In addition, to evaluate the expression of apoptosis related proteins, radio resistance and proliferation related proteins in both 3D constructs, immunostaining was performed to detect p53, BAX, P-AKT, and Ki67. The sections were incubated with primary antibodies overnight including mouse monoclonal antibody p53 (Santa Cruz, sc-126), BAX (Santa Cruz, sc-7480), rabbit polyclonal antibody P-AKT (sc-135650) and rabbit monoclonal antibody Ki67 (Cell Signaling Technology; #9129) at 4°C. Then, the sections were incubated with secondary antibody for 1 hour at 37°C. The nuclei were counterstained with DAPI, and the slides were analyzed under a fluorescent microscope (Olympus BX51).
Western blot. The 2D treated and control cells were lysed in 1X RIPA buffer (Sigma-Aldrich) supplemented with Halt™ protease and phosphatase inhibitor cocktail (ThermoFisher Scientific). The protein concentration was determined by Bradford method. Equal concentration of protein extract was subjected to 12% SDS-PAGE and transferred to poly vinylidene fluoride (PVDF) membrane. Blots were labelled with the primary antibodies, p53 (1:500, Santa Cruz, sc-126), BAX (1:500, Santa Cruz, sc-7480), and P-AKT (1/500, Santa Cruz, sc-135650). B-actin was used as control. The day after, HRP-conjugated secondary antibody (1:5000, Sigma-Aldrich) was added to the blot for 3 hours at RT. Protein expression was detected using ECL western blotting detection reagent (Bio-Rad, Hercules, CA, USA) and membranes were imaged by ImageQuant LAS 4000 mini, GE Healthcare.
HCC mouse model. To evaluate tumorigenicity of cells, different numbers of Huh7 cells (3×106, 5×106, 7×106, and 10 ×106) subcutaneously injected to four anatomical sites in nude mice. When the tumors reached a visible size, tumors removed and their dimensions measured (Figure. Supplemnetary.1).
Tumor formation assay. To assess whether 188ReO4 treated cells could form any tumor, Huh7 cells exposed to 37 MBq for 24 hours. The total number of 5×106 cells injected percutaneously to the flank of nude mice. As a control group, the same number (5×106) of untreated Huh7 cells injected percutaneously to the flank of another nude mouse. After 14 days, animals sacrificed for further assessments (Figure. Supplemnetary.1A).
Statistical analysis. All statistical analyses were performed using GraphPad-Prism, version 6. Data were presented as mean ± standard deviation (SD). In order to make statistical analysis between the treated and the control groups, the Kolmogorov-Smirnov normality tests were performed. These tests applied to find out which statistical test should be used to analyze the differences between the groups. Measurements were carried out using one-way repeated measures analysis of variance (ANOVA) and we choose the LSD method for post Hoc multiple comparisons. The p values of less than 0.05 were considered as statistically significant.