Mice C57BL/6 and hdac3fl/flcd4cre+/+ mice(KO mice) were used for experiments. Mice carrying a conditional floxed allele of hdac3 (hdac3flox, Stock No: 024119) were backcrossed onto the C57BL/6 background for 5 generations and then mated to C57BL/6 mice carrying the cd4 enhancer/ promoter/silence cre allele (obtained from The Jackson Laboratory, Stock No:022071) to generate the hdac3 conditional knockout mice, designated as hdac3fl/flcd4cre+/+. Mice were housed in a specific pathogen-free barrier unit. This experimental plan has been approved by the Animal Care and Use Committee at North China University of Science and Technology (No. LX201834). The handling of mice and experimental procedures were conducted in accordance with the relevant guidelines and regulations established by the committee. Mice were anesthetized and euthanized by intraperitoneal injection of sodium pentobarbital.
Cell line The Lewis lung carcinoma cell line (LLC) and the mouse lymphoma cell line (EL4) were both purchased from Wuhan Pricella Biotechnology. Cells were cultured at 37°C in a 5% CO2 environment. LLC cells were cultured in a complete medium composed of 10% fetal bovine serum(Pricella), 1% penicillin-streptomycin (Gibco), and 89% high-glucose DMEM basal medium༈Hyclone༉. EL4 cells were cultured in a complete medium composed of 10% fetal bovine serum, 1% penicillin-streptomycin (Gibco), and 89% 1640 basal medium༈Hyclone༉.
Genotyping Offsprings were genotyped using the following PCR primer pairs: for cd4cre mice, Wild type Reverse: 5’-TATGCTCTAAGGACAAGAATTGACA-3’; Mutant Reverse: 5’-CTTTGCAGAGGGCTAACAGC-3’; Common: 5’-GTTCTTTGTATATATTGAATGTTAGCC-3’. For hdac3 mice, Wild type Forward: 5’-TGGTGGTGAATGGCTTTAATC-3’, reverse: 5’-TAACGGGAGCAGAACTCGAA-3’. The hdac3fl/fl, cd4cre+/+ and cd4cre+/− mice produce DNA fragments of 700bp; 336 bp; 336 bp, and 262bp respectively after PCR amplification.
Mouse modeling Sex-matched C57BL/6 mice were subcutaneously injected with PBS containing 1×106 LLC cells. A week later, the presence of a palpable tumor mass at the injection site indicated successful modeling. hdac3fl/fl cd4cre+/+ mice were modeled in the same way. Fifty successfully modeled C57BL/6 mice were randomly divided into five groups: DMSO control group, 5 mg/kg RGFP966 group, 10 mg/kg RGFP966 group, 20 mg/kg RGFP966 group, and 30 mg/kg RGFP966 group. The treatment was administered every two days for two weeks. Additionally, 10 untreated C57BL/6 mice were randomly selected as the normal control group. Four hdac3fl/fl cd4cre+/+ and hdac3fl/fl cd4cre−/− genotype mice were used to establish subcutaneous lung tumor models. Forty successfully modeled C57BL/6 mice were randomly divided into four groups: solvent control group, 30 mg/kg RGFP966 group, 0.1 mg anti-IL-17 antibody (17F3, BioXCell) group, and 30 mg/kg RGFP966 plus anti-IL-17 antibody group. RGFP966 and anti-IL-17 antibody were administered via intraperitoneal injection, every two days for two weeks. The tumor size and body weight of the mice were measured. After the injections were completed, the mice were anesthetized and euthanized, and the number of bone marrow cells was counted under a microscope.
Flow Cytometry Analysis Anesthetize and euthanize the mice, then isolate the spleen or tumor tissues to prepare single-cell suspensions. Use NH4Cl to lyse red blood cells, and filter the suspension through a 100-micron mesh. Incubate the cell suspension at 4°C with Fc Block reagent (clone 2.4G2) for 10 minutes to block nonspecific binding. Add the following antibodies and perform cell surface staining at 4°C for 30 minutes: anti-CD4-APC(Biolegend), anti-CD8-PerCP-Cy5.5(BD Biosciences), anti-CD11b-APC (BD Biosciences), Anti-Ly6G-PerCP-Cy5.5(eBioscience), anti-PD-1-PE(BD Biosciences). The cell was washed with PBS buffer and then analyzed with a Beckman flow cytometer. The data were analyzed by FlowJo software.
Intracellular Cytokine Staining Splenic cells from the WT-control, the KO-control, the WT-RA, and the KO-RA mice were suspended in RPMI1640 cell culture medium in the presence of 2µg Activation Cocktail(550583, BD Biosciences), incubated 4h at 37℃. The cells were collected and first performed by cell surface staining. Then, the cells were fixed and permeated with a Cytofix/ Cytoperm kit (554722, BD Biosciences). After washing with PBS, the cells were intracellularly stained with anti-mouse-IFN-γ-PE(clone XMG1.2, Biolegend), anti-mouse-IL-4-APC(clone 11B11, Biolegend,) and anti-mouse-IL-17A-FITC (clone TC11-18H10.1, Biolegend) for 30 min at 4℃, washed with PBS buffer, and then analyzed with a Beckman flow cytometer. The data were analyzed by Flow Jo software.
Western Blot Isolate mouse tumor tissues and prepare a single-cell suspension. Add 1 ml of RIPA buffer and 10 µl of PMSF to extract the proteins, then measure the protein concentration using a BCA assay kit (Solarbio). Load 10 µg of the protein sample onto a 10% SDS-PAGE gel for electrophoresis (80V, 30min and then 120V, 90min), transferred to PVDF membrane (1h), sealed with 5% skimmed milk powder (1h), and then incubated overnight with anti-mouse HDAC3 antibody (1:1000, Abcam), rabbit anti-mouse GAPDH antibody (1:1000, Abcolonal) in 4°C refrigerator. The next day, they were incubated with goat anti-rabbit antibodies (1:5000, Proteintech) for 1h and observed protein bands with ECL kit.
Statistical analysis SPSS17 software was employed for the data processing and statistical analysis. One-way ANOVA and Student’s t-test were used to analyze the statistical difference of multiple or two groups of samples respectively. The data were presented as the mean ± SD, and p < 0.05 indicates that the difference is statistically significant.