Acquisition thyroid cancer datasets
The dataset concerning thyroid cancer with survival data from The Cancer Genome Atlas (TCGA) was acquired from the UCSC Xena database[10]. In addition, 12 GEO cohorts were studied to focus on thyroid cancer (GSE104005, GSE196264, GSE29265, GSE32662, GSE35570, GSE53157, GSE5364, GSE60542, GSE65074, GSE65144, GSE76039, and GSE82208) to examine mRNAs associated with cancer stemness. Furthermore, the gene expression profiles of a single-cell dataset for thyroid cancer with accession number GSE184362[11] were collected from the GEO database to explore mRNAs linked to intrinsic stemness in cancer cells. This dataset comprised 7 primary tumors, 6 para-tumors, 8 metastatic LNs, and 2 subcutaneous metastatic sites of thyroid cancer tissues.
Collection pan-cancer anti-CTLA4 treated Immunotherapy-associated datasets
To authenticate the precision of the model in forecasting the response to CTLA4 immunotherapy, we collected diverse datasets from cohorts treated with anti-CTLA4. These included the cohort by Riaz N[12] (GSE91061: melanoma patients administered with anti-CTLA4 and PD-1) and the cohort by Necchi[13] (IMvigor210: individuals with advanced or metastatic urothelial carcinoma treated with Atezolizumab) obtained via the "IMvigor210CoreBiologies" R package. We amassed gene expression and clinical data from these cohorts.
Collection of single cell datasets for ICI-treated SKCM cohort
To explore the relationship between the stemness properties of cancer cells and their response to immunotherapy, a cohort of melanoma patients treated with ICIs was analyzed. This analysis incorporated single-cell RNA sequencing data and ICI response information, accessible from GEO under accession number GSE115978[14].
Identifying essential genes for thyroid carcinoma
Thyroid carcinoma cells underwent CRISPR screening via the DepMap portal (https://depmap.org/portal/download). Utilizing the CERES algorithm, dependency scores for around 17,000 genes were computed. Genes deemed vital displayed a CERES score below − 1 in 75% of the 21 THCA cell lines[15].
Development and validation of tumor stemness cell prediction model
The construction of a new pipeline was undertaken to create a forecast model for cancer stem cells, illustrated in Fig. 1. Firstly, the calculation of mRNAsi was conducted on 12 GEO datasets as well as the TCGA-THCA dataset. Subsequently, the connection between overall mRNA and mRNAsi was evaluated, and mRNAs showing noteworthy positive correlations in a minimum of seven out of thirteen sets (Cor > 0.2 and P < 0.05) were recognized as mRNAsi-related mRNAs, leading to the identification of 135 mRNAsi-linked mRNAs.
As a result of the scarcity of clinical survival data on thyroid cancer, the TCGA-THCA dataset was split into two halves, Cohort1 and Cohort2, while all samples were merged into Cohort3. Afterwards, the effectiveness of the stemness model for cancer was created and assessed. A range of machine learning methods including random forest (RSF), elastic net (Enet), gradient boosting (GBM), survival-SVM, ridge regression, Stepcox, plsRcox, CoxBoost, lasso, and SuperPC were employed to construct the stemness model for cancer.
Prediction of immunotherapy outcomes using TIDE webserver
To assess the efficacy of PD-1/CTLA4 immunotherapy, we first calculated scores for tumor immune dysfunction and exclusion (TIDE) by manipulating expression data from individuals with thyroid cancer. The resulting array of expression patterns was then examined on the TIDE database platform (http://tide.dfci.harvard.edu/) to assess patient outcomes. Following this, we employed the submap algorithm on the GenePattern portal to contrast response probabilities among low- and high-TSC categories.
Cell lines
Cell lines for human thyroid cancer (KHM-5M, TPC-1) were sourced from the Cell Bank of the Committee for Conservation of Typical Cultures at the Chinese Academy of Sciences. These specific cell strains were grown in Dulbecco's Modified Eagle Medium (DMEM) acquired from HyClone, located in Logan, UT, USA, and supplemented with 10% fetal bovine serum. Additionally, the medium contained 100 IU/mL of penicillin and streptomycin from Gibco based in New York, USA.
Knockout and overexpression in ATC cell lines
Lentiviral vectors for CKS1B overexpression were provided by Genechem (Shanghai, China). The cells were stably transfected with CKS1B overexpression lentiviruses and the respective control plasmids to induce puromycin resistance. According to the manufacturer's instructions, stable transfectants were selected using 2 µg/mL puromycin for 2–3 days to establish stable CKS1B overexpressing cell lines. The siRNA targeting CSK1B was synthesized by Biotend Co., Ltd. Cells were transfected with 50 nM of siRNA for 24 hours utilizing the jetPRIME transfection kit from Polyplus-transfection (Strasbourg, France).
Western blotting
The procedure for Western blotting was as follows: Cells in culture were rinsed with ice-cold PBS, and total cellular protein lysates were extracted at 4°C using RIPA lysis buffer (Beyotime, Shanghai, China) containing 1% protease inhibitor cocktail (MedChemExpress, New Jersey, USA). After centrifugation at 12,000 g for 20 minutes at 4°C, the resulting supernatant was gathered and combined with loading buffer. Subsequently, the samples were separated through 10% SDS-PAGE and transferred onto a PVDF membrane. The membrane was then obstructed using 5% skim milk for 2 hours at room temperature, followed by an overnight incubation at 4°C with primary antibodies. Following a wash with Tris Buffered Saline, the membrane underwent incubation with secondary antibodies. Detection was conducted using enhanced chemiluminescence reagents (Beyotime, Shanghai, China). The subsequent antibodies were employed for the western blot analysis: CKS1B (ab72639 Abcam, Waltham, Massachusetts, USA), GAPDH (60004-1-Ig proteintech, Wuhan, China). The dilution ratios for the antibodies used were as specified.
Assessment of cell proliferation and migration abilities
In order to assess the capacity for clone formation, a total of 1000 to 2000 cells were introduced into individual wells of a 6-well plate and incubated for approximately 7 to 10 days. Upon reaching a size of over 50 cells, the clones were treated with 0.2% crystal violet solution for half an hour. Subsequent to a thorough rinsing with PBS thrice, the clones underwent imaging and enumeration.
Cells were distributed evenly in a 6-well plate. When they achieved confluence, a 10-µL pipette tip was used to scratch a straight line along a ruler. After rinsing with PBS, the cells were cultured in a medium without serum. Incubation was done at 37°C with 5% CO2, and images were taken at both 0 and 24 hours.
To evaluate the migration capacity of cells, 3–5×10^4 cells were resuspended in 200 µL of culture medium and positioned in the upper chamber of Transwell plates (BD Biosciences, Bedford, MA, USA). Concurrently, 600 µL of culture medium containing 10% FBS was introduced into the lower chamber. Following an incubation period of 24 hours at 37°C, the cells were fixed using 4% paraformaldehyde for a duration of 30 minutes and subsequently stained with 0.25% crystal violet for another 30 minutes. The cells in the upper chamber were then carefully removed, and those that had migrated to the bottom side of the membrane were imaged and counted.
Statistical Analysis
Various clinical features between the high and low TSC score groups were compared using the Wilcoxon test. Analyzing the diversity in the response to immunotherapy among the groups with low and high TSC score was carried out using the Chisq test. Calculating Pearson's correlation coefficient served to explore the linkage between mRNA and mRNAsi. Investigations into the relationship among TSC, CKS1B, and survival were conducted using Kaplan-Meier survival analysis; the log-rank test determined the significance of observed differences. Time-dependent receiver operating characteristic (ROC) curves were utilized to assess both the prognostic and immunotherapy advantages of TSC, employing the 'pROC' R package. Based on the optimal threshold identified by the 'survminer' R package, patients were categorized accordingly. Statistical significance was defined by a significance level of P or adjP < 0.05.