Data collection and processing
All clinical information and bulk RNA-seq and array expression data were downloaded from Gliovis (http://gliovis.bioinfo.cnio.es/). All the data were preprocessed by normalizing. Single-cell expression profiles were obtained from a previous study published in the GEO database (GEO Accession No. GSE131928). Data analysis was conducted using R 4.0 (R Core Team, 2020).
Clinical Samples
Glioma tissues were resected in 2020 from patients in the Department of Neurosurgery, Huashan Hospital of Fudan University. Normal brain tissues were gathered from traumatic brain injury patients. The experiments were approved by the Human Ethics Committee of Huashan Hospital, and informed consent was signed by all patients.
Cell culture and cell line construction
U87-MG cells cell lines were maintained in DMEM (PWL035), supplemented with 10% FBS (Gibco) and 1% PenStrepGlutamine in a humidified incubator with 5% CO2 at 37%.
Scramble-shRNA lentivirus, and FAM64A-shRNA lentivirus were purchased from Hanbio (Shanghai, China). U87-MG cells were transfected with lentivirus according to the manufacturers’ instructions. 2 μg/mL puromycin were used to select stable clonal cell lines.
Immunoblotting and Immunofluorescence
RIPA lysis buffer was used for both tissues and cell protein extraction. After centrifugation, the supernatant was gathered, then the 5× loading buffer was added and boiled for 5 min. Western blot was conducted as previously described [21]. The data analysis and statistics were performed through ImageJ as reported previously [22]. Anti-FAM64A anti-body (#ab118102) produced in rabbit was purchased from Abcam. Anti-b-Tubulin antibody (#M30109) was purchased from Abmart.
In vitro cell growth and migration assays
In vitro cell growth assays were performed by cell-counting kit-8 (CCK8) assays. U87-MG cells were seeded in 96-well plates and were incubated with 10% CCK8 solution at 37 °C for 2 h, and then the absorbance at 450 nm was measured. DMEM supplemented with 10% FBS was added along with denoted ligands to detect whether FAM64A could be induced by TGF-b signaling.
In vitro migration assays were performed by wound healing assay. ShFAM64A and shScramble U87-MG cells were plated in 24-well culture plates. Cell monolayers were allowed to rest for 12 h and a wound was made by scraping the middle of the cell monolayer with a P10 pipette tip. Cells were washed thrice with PBS twice and photographed. Migration was monitored and photographed 12 h later in DMEM supplemented with 10% FBS. Quantitation was performed on images at least three independent experiments for each experimental condition.
Immunofluorescence
Cells and glioma tissues were fixed with prechilled 4% paraformaldehyde for 30min and blocked with 1% bovine serum albumin (BSA) for 1 hour. Immunofluorescence staining was performed with antibody overnight at 4˚C. Then the sections were incubated with the secondary antibodies for 1 hour. The nucleus was stained with DAPI (1:500, Proteintech). Olympus IX73 microscopic system was used for imaging. Confocal images were acquired with a Leica SP8 confocal microscope (Leica).
Flow cytometry analysis of cell-cycle progression
Cell cycle analysis was conducted with propidium iodide (PI) (Biosharp, China). 5 × 106 cells were harvested after digestion and fixed with ice-cold 70% ethanol at 4°C for 1 hour. After being washed with PBS, 100 µL RNase A and 400 µL PI were mixed well and added to the suspensions in a dark place for 30 min. Finally, a flow cytometer and data fitting software were employed for the cell cycle analysis.
Single-cell transcriptome data analysis
R package Seurat was applied to aggregate all samples [23], and perform quality control on raw gene expression matrix obtained from Cell Ranger pipeline. The filtering criteria for each cell were: (1) the number of genes expressed ranges from 200 to 4000, and (2) the percentage of the mitochondrial genes is less than 25%. Cells that did not satisfy the above criteria were discarded. Gene expressions were normalized by log normalization with factor 10,000, and the top 2000 highly variable genes were selected for PCA. Harmony was utilized for batch-effect correction based on the top 50 principal components of PCA [24]. The corresponding cell types of the clusters were annotated using SingleR with the reference datasets of human immune cells. The annotation was further verified manually following known gene markers.
Transcription factor prediction
CistromeDB toolkit (http://dbtoolkit.cistrome.org/) was used to predict the function of this TF [25]. FAM64A (NM_001195228) was used as input. Transcription factors and chromatin regulators with a 10 kb half-decay distance to the transcription start site were predicted. The cutoff value of a relatively high regulatory potential (RP) score was set as 0.3.
Nomogram and chemotherapeutic responses evaluation
A nomogram was built on the predictive model as a graphical presentation. Chemotherapeutic responses of glioma were assessed by R package “pRRophetic” based on gene expression profiles [26]. Cgp2016 dataset was used as a reference dataset.
Statistical analysis
Comparisons between groups were done using either Student’s t-test or one-way ANOVA test on GraphPad Prism 8. Difference between groups is considered significant at p-values<0.05. P value for multiple comparisons was adjusted by the Tukey–Kramer post hoc test. Kaplan–Meier analysis was used to analyze the data and used the log-rank p-value to compare the two groups.