Method statement
all research was performed in accordance with relevant guidelines and regulations.
Bioinformatics analysis
In this study, we recruited a bioinformatics approach to narrow the candidate genes for potential markers. In the Gene Expression Omnibus (GEO) repository of NCBI, microarray analysis results submitted by worldwide researchers are made available. From the NCBI database, data sets of gene expressions in PBMC were searched. Search terms were (Homo sapiens) AND (HCC OR (hepatocellular carcinoma)) AND (PBMC OR (peripheral blood mononuclear cell) OR (white blood cell) OR (WBC))”. Inclusion criteria were (1) PBMCs or any other white blood cells’ expression file (2) Including both healthy donor cases and HCC cases (3) Datasets of homo sapiens. As a result, two gene expression datasets that compared between PBMC samples from healthy individuals and HCC patients were selected, GSE49515 and GSE58208. We conducted t-tests in each gene expression of each dataset using “Connection Up and Down Regulation Expression Analysis of Microarrays (CU-DREAM) http://pioneer.netserv.chula.ac.th/~achatcha/CU-DREAM/)29”, to evaluate the intersection genes and obtained 187 upregulated genes from both datasets. Then, three genes with highly significant p-values (p < 0.001) were selected and used to observed gene expressions in our samples.
Study Population
All samples were recruited from King Chulalongkorn Memorial Hospital, Bangkok, Thailand and included 2 cohorts as the following:
Cohort 1: Samples were collected from June 2018 to January 2019 and included 83 HCC cases and 52 healthy donors.
Cohort 2: Samples were collected from January 2020 to July 2020 and included 70 HCC cases and 24 healthy donors.
A total of 153 HCC cases and 76 healthy donors participated in this study. Patients with hepatitis viral infection were excluded from this study. HCC staging was recorded according to current BCLC guidelines. All subjects in this study were of Asian descent, further bioinformation is provided in (Table 2).
We then used the preliminary results from both GSE 49515 and GSE 58208 to find the appropriate sample size with the following formula:
n = [(Zα/2 + Zβ)2(σ2d)]/( d)2
n = sample size
d = Different of value in each group
d = Different of mean in each group
σ2d = Different of variance in each group
Zα/2 = Standard normal variate for level of significance
Zβ = Standard normal variate for power
We calculated and found that the sample size for our study was 24.44 samples, confirming that our study has recruited enough samples for the experimentation.
Blood sampling and PBMC extraction
Two ml of EDTA blood was extracted from all patients. Lymphocyte isolation medium was added to a 15 ml tube and centrifuged at 1600 rpm at 16°C for 12 minutes and the plasma was separated. Whole blood (diluted 1: 1) with PBS was carefully layered on a tube of lymphocyte separation medium and centrifuged at 2,800 rpm for 15 minutes at 16°C. The cell interface layer was carefully separated into 1.5 ml tubes and cells were washed with 1 ml PBS for 15 minutes at 1700 rpm 16°C and 500 ml PBS for 5 minutes at 4°C. The research methodology employed in this project was approved by The Institutional Review Board of the Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand (IRB No. 108/60 and 438/60). All study subjects provided written informed consent.
RNA extraction
PBMCs were mixed with 1 ml of TRIzol reagent (ThermoFisher Scientific, MA, USA) and incubated at room temperature for 5 minutes, then 200 μl of chloroform was added and incubated at room temperature for 3 minutes. Thereafter, it was separated into three phases by centrifugation at 8,760 rpm at 4°C for 15 minutes. The colorless upper aqueous phase was transferred to a new RNA tube, supplemented with 4 μL of glycogen (20 mg / mL) and 500 μl of 100% isopropanol, incubated for 10 minutes at room temperature, then centrifuged at 8,760 rpm at 4°C for 15 minutes. The supernatants of the centrifuged tubes were discarded, and the RNA pellets were washed with 1 ml of 75% ethanol, mixed by vortexing, and centrifuged at 6,930 rpm at 4°C for 5 minutes. Thereafter, supernatant was discarded again, and RNA pellet was dried by vacuum for 8 minutes and resuspended with 30 μL of DEPC water. RNA concentration and integrity were confirmed by Nanodrop and bioanalyzer.
Complementary DNA (cDNA) synthesis
After, the total RNA was extracted from PBMCs using TRIzol reagent (Thermo Scientific) according to the manufacturer’s protocol. Then, cDNA was synthesized using RevertAid First Strand cDNA Synthesis (Thermo Scientific). The process of cDNA synthesis is as follows: thaw, mix and centrifuge the components of the kit then add the template RNA 0.1 ng - 5 µg, primer 1 µL, nuclease-free water up to 12 µL, 5X reaction buffer 4 µL, Ribolock RNAse inhibitor 1 µL, 10 mM dNTP mix 2 µL, RevertAid M-MuLV RT 1 µL. After mixing and brief centrifuging, the samples were incubated for 5 min at 25°C followed by 60 min at 42°C. Finally, terminate the reaction by heating at 70°C for 5 min. The product of the first strand cDNA synthesis can be used directly in PCR or qPCR.
Primer preparation
Primers were designed using Primer3plus30 (for FLNA) and Primer Blast31 (for CAP1 and CLU). Primers were synthesized by BIONEER. Each primer sequence, melting temperature, and product length are shown in (Table 3). Prior to quantitative PCR, conventional PCR and electrophoresis for finding optimal temperature for each primer was conducted.
Table 3
Details of forward and reverse primer sequences of three candidated genes used for qRT-PCR analysis.
Gene
|
Forward
|
Reverse
|
Tm
|
Product length
|
CLU
|
CAGGCCATGGACATCCACTT
|
GTCATCGTCGCCTTCTCGTA
|
60.03
|
78 bp
|
FLNA
|
TTTCCGCCAAATGCAGCTTG
|
ACACCAGTTTGATGCTCTCG
|
60.32
|
74 bp
|
CAP1
|
GGAACTCTGAGGTGGTCCATTA
|
ACGGTGCATGTCAGAGGTATG
|
60.13
|
108 bp
|
Quantitative Real-time PCR (qRT-PCR) analysis
The quantitative PCR contained 10µl SensiFast (Bioline), 0.8µl of forward and reverse primers, cDNA(1µl for FLNA, 0.5µl for CLU and CAP1), and 7.4µl distilled water in a total volume of 20µl. The reactions were carried out on QuantStudio 6 (Thermo Fisher Scientific) according to the manufacturer’s protocol. PCR conditions were as follows: denaturation at 95°C for 2 mins with 45 cycles, annealing at 59°C, 55°C, 59°C for CLU, FLNA, CAP1, respectively for 30s. Fluorescence signals from the amplified product were detected at the end of the annealing step. Duplications were done on available and unamplified samples. The Ct value was set to 45 if the sample did not show any amplification twice. In this study, the housekeeping gene or the reference gene, that was used is glyceraldehyde 3-phosphate dehydrogenase (GAPDH). We used this gene to test and analyze alongside our interested gene (CLU, FLNA, and CAP1).
The calculation is as follows:
ΔΔCt = ΔCt (a target sample)−ΔCt (a reference sample)
The final result is represented in the folds of change (thus, the equation is in the power of 2 or 2-ΔΔCt) of the interested gene expression in the sample against the reference sample.32
Statistical analysis
Box plot, summary of the dataset (including t-test results of Ct mean of each gene), benchmarks (Accuracy, Sensitivity, and Specificity) heatmaps (confusion matrices) and the Receiver Operating Characteristic (ROC) curves were drawn with python 3.9 program with packages (scipy33, pandas34 and matplotlib35). Ct values of each gene were included into the dataset. For the evaluation of performance, the entire dataset was used for the test. The p-value cut-off for each test was at <0.05 for results to be statistically significant.