Identification of a Prognostic Model Based on Immune-Related Genes of Lung Squamous Cell Carcinoma

Abstract

Immune-related genes (IRGs) play considerable roles in tumor immune microenvironment (IME). This research aimed to discover the differentially expressed immune-related genes (DEIRGs) based on the Cox predictive model to predict survival for lung squamous cell carcinoma (LUSC) through bioinformatics analysis. First of all, the differentially expressed genes (DEGs) were acquired based on The Cancer Genome Atlas (TCGA) using the limma R package, the DEIRGs were obtained from the ImmPort database, whereas the differentially expressed transcription factors (DETFs) were acquired from the Cistrome database. Thereafter, a TFs-mediated IRGs network was constructed to identify the candidate mechanisms for those DEIRGs in LUSC at molecular level. Moreover, Gene Ontology (GO), together with Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis, was conducted for exploring those functional enrichments for DEIRGs. Besides, univariate as well as multivariate Cox regression analysis was conducted for establishing a prediction model for DEIRGs biomarkers. In addition, the relationship between the prognostic model and immunocytes was further explored through immunocyte correlation analysis. In total, 3,599 DEGs, 223 DEIRGs, and 46 DETFs were obtained from LUSC tissues and adjacent non-carcinoma tissues. According to multivariate Cox regression analysis, 10 DEIRGs (including CALCB, GCGR, HTR3A, AMH, VGF, SEMA3B, NRTN, ENG, ACVRL1, and NR4A1) were retrieved to establish a prognostic model for LUSC. Immunocyte infiltration analysis showed that dendritic cells and neutrophils were positively correlated with IRGs, which possibly exerted an important part within the IME of LUSC. Our study identifies a prognostic model based on IRGs, which is then used to predict LUSC prognosis and analyze immunocyte infiltration. This may provide a novel insight for exploring the potential IRGs in the IME of LUSC.

Introduction

Lung cancer remains a leading factor leading to cancer-related deaths worldwide (1). Lung cancer is associated with a high mortality compared with that of breast cancer (BC), prostate cancer (PCa), colorectal cancer (CRC), and leukemia (1, 2). Lung squamous cell carcinoma (LUSC) occupies about 20–30% non-small cell lung cancer (NSCLC) cases, which causes an annual of 400,000 deaths around the world (3, 4). For TNM stage II LUSC cases, the survival at 5 years is 40%, while that for LUSC cases at pathological TNM stage IV is <5% (5). Moreover, the prognostic biomarkers that can be used in a prediction model for LUSC patients are still lacking (6, 7).

Recently, immunotherapy has been widely recognized to be the efficient therapy for many cancer types (8–11). Recently, Fan et al. had identified reliable markers for predicting the immunotherapy effect on non-small cell lung cancer (NSCLC) (12). Currently, immunotherapy has been considered as the potentially efficient therapy in tumor patients (12). Prat et al. estimated the correlations of immune-related genes (IRGs) expression profiles in squamous NSCLC (sqNSCLC) cases with advanced non-squamous NSCLC (non-sqNSCLC) after PD-1 blockade (13). Furthermore, several clinical studies promote tumor immunology development within LUSC (14). Recently, Li et al. used IRGPs to construct the personalized prognostic model to predict the prognosis for early non-sqNSCLC patients (15). However, the prognostic significance of IRGs and clinical relevance in LUSC have not been illustrated so far.

This study aimed to obtain the differentially expressed genes (DEGs), differentially expressed IRGs (DEIRGs), and differentially expressed TFs (DETFs) in LUSC, so as to establish a Cox prediction model based on the DEIRGs to predict the prognosis for LUSC. The regulatory network between DEIRGs and DETFs possibly exerts an important part in exploring the underlying mechanisms at molecular level. Meanwhile, correlation analysis of immunocytes and risk score also sheds new light on the tumor immune microenvironment (IME) status.

Materials and Methods

Clinical Patients and Data Acquisition

Transcriptome RNA-sequencing gene expression profiles were downloaded from TCGA GDC data portal (https://portal.gdc.cancer.gov/), including 502 LUSC as well as 49 non-LUSC tissue specimens. Additionally, FPKM data were downloaded for differential analysis. Meanwhile, IRGs were obtained using the Immunology Database and Analysis Portal (ImmPort) (http://www.immport.org/) (16). Besides, the cancer TF targets were downloaded from Cistrome Project (http://www.cistrome.org/) (17).

Differential Expression Analysis in LUSC

All transcriptome RNA-Seq data, IRGs, and cancer TF targets were differentially analyzed using the “limma R” package (http://www.bioconductor.org/packages/release/bioc/html/limma.html) (18), according to the thresholds of adjusted false discovery rate (FDR) P-value of <0.01 and absolute fold change (log2) of >2. DEIRGs were obtained from DEGs based on the ImmPort database, whereas DETFs were extracted from DEGs using the Cistrome database.

Functional Analyses for DEIRGs in the Context of LUSC

For exploring the functions among those DEIRGs in terms of their expression profiles, Gene Ontology (GO), together with Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis, was conducted on DEIRGs using the Database for Annotation, Visualization, and Integrated Discovery (DAVID: https://david.ncifcrf.gov/) (19). Upon GO analysis, a difference of P < 0.05 indicated statistical significance. Furthermore, the GOCircle as well as GOChord plotting was obtained using GOplot R package (https://cran.r-project.org/web/packages/GOplot/citation.html) (20). In addition, KEGG pathway enrichment analysis was performed using the “cluster profile R” package (http://www.bioconductor.org/packages/release/bioc/html/clusterProfiler.html) (21), and a difference of P < 0.05 indicated statistical significance. For additionally exploring the associations of DEIRGs with KEGG pathways, the Cytoscape software (version 3.6.1) was employed to construct the pathway-IRGs network for visual analysis.

Prognosis-Related DEIRGs and TFs Mediated IRGs Regulatory Network

We used the “survival R” package to perform the univariate Cox regression analysis to obtain prognosis-related DEIRGs in LUSC (P < 0.05). TFs stand for the significant molecules that can regulate gene expression level directly. Therefore, exploring the mechanism of TFs in the regulation of prognosis-related DEIRGs is of great necessity. The Cistrome Cancer database provides the regulatory interactions between TFs and transcriptomes from TCGA profiles (http://cistrome.org/CistromeCancer/CancerTarget/) (17). To further examine the molecular regulatory mechanisms of prognosis-related DEIRGs, a co-expression network between prognosis-related DEIRGs and DETFs was constructed, according to the thresholds of p-value filter of < 0.001 and standard coefficient filter of >0.4.

Construction of the DEIRGs-Based Prediction Model in LUSC

Univariate Cox regression analysis was carried out for obtaining those prognosis-related DEIRGs as the prognostic biomarkers for multivariate Cox regression analysis (P < 0.05). Then, LUSC cases were classified into low or high-risk group according to the median risk score value. The receiver operating characteristics (ROC) curve is based on the specificity and sensitivity of various critical values of continuous diagnostic tests judged according to the binary gold standard (22). To evaluate the specificity and sensitivity of the prognostic model, the ROC curve was performed to examine the signature of DEIRGs (low vs. high risk) on overall survival (OS). Moreover, the area under the ROC curve (AUC) values were determined for evaluating the prognostic model to reveal the prognostic biomarkers in LUSC, with values of 0.5–0.7 representing moderate, 0.7–0.9 representing better, and more than 0.9 representing superior values.

Correlation Analysis Between Clinical Features and DEIRGs in Prediction Model of LUSC

In order to further explore the correlations between DEIRGs in prediction model and clinical characteristics of LUSC, we used the “beeswarm” R package to analyze the correlations between clinical features (age, gender, pathological T stage, pathological N stage, pathological M stage, and pathological TNM stage) and the expression levels of 10 DEIRGs in the prediction model.

Infiltration of Immunocytes

Tumor Immune Estimation Resource (TIMER), an online database, is able to analyze and visualize the tumor-infiltrating immunocyte levels (23). It reanalyzes gene expression data of 10,897 TCGA samples from 32 types of cancers for identifying correlation between immunocyte infiltration and other characteristics, incorporating dendritic cells, neutrophils, macrophages, CD4 T cells, CD8 T cells, and B cells (https://zenodo.org/record/57669#.Xeezu9V5uMo).

Statistical Analysis

The “limma R” package in R software was used for differential analysis, whereas the “GOplot R” and “cluster profile R” packages were adopted for functional enrichment analysis. The prediction model was constructed and applied in univariate as well as multivariate Cox regression analysis. Besides, the “survival ROC R,” “survival R,” “risk Plot R,” and “beeswarm R” packages were adopted to validate the prognostic model in LUSC. The independent t-test was performed to validate the heterogeneities in clinical characteristics. A difference of P < 0.05 indicated statistical significance.

Results

DEGs, DEIRGs, and DETFs

In the present study, a total of 551 tissues were analyzed, which included 502 LUSC as well as 49 normal tissue specimens. According to the set thresholds (P < 0.01 and fold change of >2), 3,599 DEGs, 223 DEIRGs, and 46 DETFs were screened in LUSC as well as non-LUSC tissue specimens. In line with these criteria, we screened 2,598 up-regulated DEGs and 995 down-regulated ones, 110 up-regulated DEIRGs and 113 down-regulated ones, 31 up-regulated DETFs and 15 down-regulated ones. Among them, the top 50 DEGs, DEIRGs, and DETFs are shown in Tables 1–3, respectively. For exhibiting the distributions of all DEGs, DEIRGs, and DETFs at logFC and -log (FDR) dimensions, the volcano plots and heat maps were drawn (Figures 1A–F). Figure 2 presents the flow diagram of this research.

Figure 1

Figure 2

Functional Analyses for DEIRGs

For explaining biological functions of DEIRGs in LUSC patients, functional enrichment analyses were conducted. According to GO analysis results, 5 GOs displayed significant difference (P < 0.05), among which, “GO: 0005576 extracellular region” was the most significant GO term (Figures 3A,C). Figure 3B shows the correlations between the top 30 statistically significant DEIRGs and corresponding GO terms. Furthermore, the “cluster profile R” package was used for KEGG pathway enrichment analyses. The dot plot shows the 10 most significant pathways with the highest enrichment levels of DERGs within the KEGG database (Figure 3D). In addition, the bar plot indicates the 12 most significant pathways with the highest enrichment levels of DEIRGs within the KEGG database (Figure 3E). Those 21 statistically significant pathways in the KEGG database were selected to construct the “pathway-DEIRGs” network (Figure 3F). The 21 statistically significant pathways in the KEGG database are shown in Table 4. A difference of P < 0.05 indicated statistical significance.

Figure 3

Univariate Cox Regression Analysis and Regulatory Network of Prognosis-Related DEIRGs and DETFs

Univariate Cox regression analysis was analyzed to identify prognosis-related DEIRGs in LUSC (P < 0.05). Then, 37 OS-related DEIRGs were identified, incorporating 31 high-risk DEIRGs and 6 low-risk DEIRGs (Figure 4A). For exploring the molecular mechanism of prognosis-related DEIRGs, we constructed the TFs-IRGs regulatory network. A total of 26 prognosis-related DEIRGs and 13 DETFs were shown in the network (Figure 4B). As shown in Figure 4B, CENPA had a negatively relationship with A2M, TIE1, ENG, and ACVRL1. ARRB1 had a negatively relationship with TP63, SNAI2. SOX2 had a negatively relationship with ICAM1 and TNFRSF10C. The coefficient filter >0.4 and the p-value filter < 0.001 were set as the threshold to indicate statistical significance. Table 5 shows the regulatory network between DETFs and prognosis-related DEIRGs in LUSC.

Figure 4

Establishment of the 10 DEIRGs-Based Prediction Model in LUSC

The prognostic DEIRGs were screened through univariate Cox regression analyses in LUSC, including 37 OS-related DEIRGs (P < 0.05) (Figure 4A). Then, the 37 DEIRGs were selected to incorporate into multivariate Cox regression analysis, which suggested that 10 DEIRGs might serve to be the prognostic factors to independently predict LUSC prognosis. These 10 DEIRGs were finally screened for constructing the prediction model (Table 6). Besides, expression profiles of these 10 DEIRGs were then linearly combined to build up the prediction model in LUSC. The weighted relative coefficients in multiple Cox regression were shown below: survival riskscore value = (0.2141 × SEMA3B expression + (−0.2698) × AMH expression + (−0.6777) × CALCB expression + 0.1896 × NRTN expression + 0.3628 × VGF expression + 0.4248 × ACVRL1 expression + (−0.3538) × ENG expression + (−0.4009) × GCGR expression + 0.1985 × HTR3A expression + 0.1339 × NR4A1 expression). Multivariate Cox regression analyses are shown in Table 6. Based on the median riskscore value, 431 cases who had intact survival time and status data were classified as high-(n = 215) or low- (n = 216) risk group. According to survival analysis based on the prediction model with the 10 DEIRGs, LUSC cases of high-risk group were associated with notably poor prognosis compared with those of low-risk group (P = 0) (Figure 5A). To evaluate the specificity and sensitivity of the prognostic model, we performed the ROC curve, for which the AUC value was 0.709, illustrating that the DEIRGs-based prediction model achieved better accuracy in survival monitoring (Figure 5B). The riskscore curve and survival status data of both groups of patients are exhibited in Figures 5C,D, respectively. As shown in Figure 5E, the expression of 10 DEIRGs was profiled.

Figure 5

Independent Prognosis Analysis

The prognostic IRGs were screened for predicting the prognosis for LUSC cases. Eventually, altogether 37 DEIRGs showed significant correlation with overall survival (OS) (P < 0.05) (Figure 6A). Meanwhile, univariate independent prognostic analysis showed that, pathological M stage and the riskscore were related to OS, and the difference was of statistical significance (P < 0.001). Moreover, the multivariate independent prognostic analysis showed that, pathological M stage and the riskscore might serve as the independent prognostic factors to predict the survival for LUSC (Table 7; Figure 6B).

Figure 6

Relationships Between Differential IRGs in Prediction Models and Clinical Features in LUSC

Relationships between DEIRGs in risk model and clinical characteristics, including gender, age, pathological classification, pathological T stage, pathological N stage, and pathological M stage, were analyzed (Table 8). As observed from Figure 7, the expression levels of AMH, CALCB, ACVRL1 and NR4A1 were significantly different in LUSC at pathological I-II stage compared with those at III-IV stage (P < 0.05) (Figures 7A–D). The expression levels of AMH, CALCB, GCGR, and NR4A1 were significantly different in LUSC at pathological T1-T2 stage compared with those at T3-T4 stage (P < 0.05) (Figures 7E–H). The expression levels of SEMA3B, AMH, CALCB, and GCGR were significantly different in LUSC at pathological M0 stage relative to those at M1 stage (P < 0.05) (Figures 7I–L). The expression of VGF was conspicuously different in LUSC at pathological N0 stage relative to that at N1-N3 stage (P = 0.005) (Figure 7M).

Figure 7

Correlation Analysis Between DEIRGs in Prediction Model and Immunocyte Infiltration in LUSC

To figure out whether DEIRGs precisely reflected the status of LUSC IME, correlation analysis was carried out to examine the relationship between DEIRGs in the LUSC prediction model and immunocyte infiltration (Figure 8). As shown in Figure 8, B cells, CD4-T cells, CD8-Tcells, Macrophages were not associated with the riskScore of the prediction model (P > 0.05) (Figures 8A–E). Dendritic cells and neutrophils had a positively relationship with DEIRGs in prediction model (P < 0.05) (Figures 8D,F).

Figure 8

Discussion

In recent years, IRGs show increasing importance to cancer development and immunotherapies (24–27). However, transcriptome studies on IRGs, the relationships of IRGs with clinical characteristics, and the molecular mechanisms have not been performed yet. In the present work, the Cox prediction model was established for revealing IRGs specific to LUSC, so as to predict LUSC prognosis. The regulatory network between IRGs and TFs revealed the potential novel molecular mechanisms in LUSC. In this study, the DEIRGs obtained in LUSC might play a vital role in predicting the prognosis for LUSC. More importantly, an individualized Cox prediction model with DEIRGs was adopted for measuring immunocyte infiltration and evaluating the clinical prognosis.

In recent years, the prognostic or predictive biomarkers associated with the tumor IME are promising to identify new molecular targets and to enhance the treatment for patients during immunotherapy development (28–34). Several recent studies reveal the prognostic biomarkers in tumor IME for predicting tumor prognosis. Li et al. found that four IRGs were identified as the biomarkers to predict the prognosis for breast cancer (35). Pan et al. discovered that 149 immune genes were identified as the prognostic genes in tumor IME to predict ESCC prognosis (36). Yang et al. suggested that the diagnostic immune score (DIS) and prognostic immune score (PIS) showed diagnostic and prognostic significance for cancers in the digestive system (37). Nowadays, prognostic biomarkers related to the tumor IME in lung cancer are still lacking.

A study demonstrates that the NSCLC IME may be adopted to be the potential prognostic biomarkers to predict patient prognosis after receiving immune checkpoint inhibitor treatments (37). However, the molecular mechanism of prognosis-related DEIRGs associated with DETFs in LUSC tumor IME is not examined yet. The present study was carried out to explore DEIRGs and establish the IRGs-based prognostic model in LUSC IME to reveal the prognostic biomarkers to predict LUSC diagnosis and prognosis.

According to functional enrichment analysis in this work, DEIRGs showed the highest enrichment levels within tumor-related typical pathways, including the JAK-STAT signal transduction pathway, the TGF-β signal transduction pathway, the PI3K-Akt signal transduction pathway, the MAPK signal transduction pathway, and the TNF signal transduction pathway. According to recent research, alterations in MET-activation and JAK2-inactivation are the independent factors that affect the response to immune checkpoint inhibitors like PD-L1 in lung cancer (25). As suggested in one study, the combination of MEK and PD-L1 inhibitors in pre-clinical and ex-vivo NSCLC models exerts an important part in predicting patient sensitivity to such therapies (38).

For further exploring the underlying mechanisms of DEIRGs at molecular level, the TF-mediated IRGs network was constructed in the present study, so as to reveal the significant TFs regulating DEIRGs in this network. FOXA2, TP63, FLI1, TCF21, EPAS1, ERG, GATA6, FOS, CENPA, SOX2, RXRG, NR4A1, and SNAI2 were the DETFs that might regulate the DEIRGs in LUSC. Tang et al. discovered that curcumin inhibited the growth of human NCI-H292 LUSCs by up-regulating FOXA2 expression (39). FLI1 acts as a novel oncogenic diver to promote the metastasis of small cell lung cancer (SCLC). LncRNA LINC00163 serves as the tumor suppressor through transcriptionally up-regulating TCF21 expression in inhibiting the development of lung cancer (40). In addition, the hypoxic-stabilized EPAS1 proteins transactivate DNMT1, which further promotes the hypermethylation of EPAS1 promoter and down-regulates EPAS1 mRNA expression in NSCLC (41). A recent study showed that CENPA could act as a novel diagnostic biomarker in lung adenocarcinoma (42). Compared with previous studies, our study had first constructed the co-expression DETFs-prognosis-related DEIRGs regulatory network in LUSC using bioinformatics analysis. From the network in our study, the DETFs positively and negatively regulated the DEIRGs, which shed new light on exploring the DEIRGs mechanisms in LUSC at molecular level.

In our study, univariate as well as multivariate Cox regression analysis was carried out to constructed the DEIRGs-based Cox prediction model. Eventually, the 10 DEIRGs in prediction model played critical parts in predicting LUSC prognosis. In addition, the AUC was 0.709, while the P-value between high and low risk groups was 0, which indicated that the Cox prediction model might be able to accurately estimate LUSC prognosis. Univariate as well as multivariate independent prognosis analysis in our study indicated that, the pathological M stage and the riskScore of the Cox prediction model might serve as the independent prognostic factors to predict LUSC prognosis. Furthermore, 10 DEIRGs were applied for correlation analysis between the expression profiles of IRGs and clinical characteristics. Semaphorin 3B (SEMA3B) can be used to be the tumor suppressor gene to suppress the Akt signal transduction pathway, which is achieved via the neuropilin-1 receptor in lung cancer cells (43). The AMH/AMHR2 axis provides a novel insight to illustrate the TGF-β/BMP resistance-associated signaling in NSCLC (44). Epigenetic modifications facilitate the expression of VGF, up-regulate its protein expression, and promote epithelial-mesenchymal transition (EMT) progression as well as kinase inhibitor resistance within NSCLC (45). GCGR acts as a member of the prognostic model, which can exert an important part in predicting LUSC survival (46). In addition, NR4A1 exerts an important part in the regulation of TGFβ-induced invasion and migration of lung cancer cells (47).

Our study first used bioinformatic analysis to integrate the clinical characteristics of LUSC with the expression profiles of 10 DEIRGs to explore the statistically significant DEIRGs for forecasting LUSC diagnosis and prognosis. Finally, immunocyte correlation analysis was conducted using the contents of the TIMER database of six types of immunocytes. According to our results, dendritic cells and neutrophils exhibited a significantly positive regulatory relationship with the riskscore of the Cox prediction model. Compared with previous studies, the present study presented the new signature in which DEIRGs were selected as the center, which might be used to predict LUSC prognosis. Furthermore, the DEIRGs might act as the prognostic biomarkers and immune status monitor for predicting LUSC prognosis. We explored the relationships between DEIRGs in prediction model and immunocyte infiltration to reflect the status of IME in LUSC. Dendritic cells and neutrophils were positively correlated with DEIRGs in prediction model, which indicated that the high infiltration levels of dendritic cells as well as neutrophils might be identified in high-risk LUSC patients. These results showed that DEIRGs in prediction model could act as predictor for predicting immunocyte infiltration in LUSC. A study demonstrated that STAT3 and NF-κB signaling pathways were simultaneously attenuated in dendritic cells of lung cancer (48). A study showed that the tumor-associated CD66b neutrophils were correlated with adverse prognostic factors of NSCLC (49). The number of mature dendritic cells were positively correlated with survival time in NSCLC patients (50), While our findings showed that dendritic cells had a positively relationship with the riskScore of the prediction model. These results demonstrated that the prediction model based on DEIRGs could predict the status of immunocyte infiltration in LUSC.

Our prognostic model, which was constructed based on 10 DEIRGs in LUSC, indicated favorable clinical viability. It showed that DEIRGs performed moderately in the ROC curve, and were associated with age, gender, pathological TNM stage, and metastasis. This predictive model may provide a treatment plan based on the immunocyte infiltration degree revealed by DEIRGs.

In conclusion, our study identifies the DEGs, DEIRGs, and DETFs by bioinformatics analysis from TCGA, ImmPort and Cistrome databases. A TFs-IRGs network is performed to reveal the possible mechanism for DEIRGs in LUSC at molecular level. Additionally, the Cox prediction model is constructed for identifying the prognostic independent factors to predict LUSC prognosis. Immunocyte correlation analysis is also performed to identify the relationships between the immune status and the clinical outcomes for LUSC patients.

References

• 1.

  TorreLABrayFSiegelRLFerlayJLortet-TieulentJJemalA. Global cancer statistics, 2012. CA Cancer J Clin. (2015) 65:87–108. 10.3322/caac.21262

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 2.

  SiegelRLMillerKDJemalA. Cancer statistics, 2019. CA Cancer J Clin. (2019) 69:7–34. 10.3322/caac.21551

  • CrossRef
  • Google Scholar

• 3.

  ZhangPKangBXieGLiSGuYShenYet al. Genomic sequencing and editing revealed the GRM8 signaling pathway as potential therapeutic targets of squamous cell lung cancer. Cancer Lett. (2019) 442:53–67. 10.1016/j.canlet.2018.10.035

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 4.

  ShumEWangFKimSPerez-SolerRChengH. Investigational therapies for squamous cell lung cancer: from animal studies to phase II trials. Expert Opin Investig Drugs. (2017) 26:415–26. 10.1080/13543784.2017.1302425

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 5.

  HattoriATakamochiKOhSSuzukiK. New revisions and current issues in the eighth edition of the TNM classification for non-small cell lung cancer. Jpn J Clin Oncol. (2019) 49:3–11. 10.1093/jjco/hyy142

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 6.

  WangCTanSLiuW-RLeiQQiaoWWuYet al. RNA-Seq profiling of circular RNA in human lung adenocarcinoma and squamous cell carcinoma. Mol Cancer. (2019) 18:134. 10.1186/s12943-019-1061-8

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 7.

  HoangLTDomingo-SabugoCStarrenESWillis-OwenSAGMorris-RosendahlDJNicholsonAGet al. Metabolomic, transcriptomic and genetic integrative analysis reveals important roles of adenosine diphosphate in haemostasis and platelet activation in non-small-cell lung cancer. Mol Oncol. (2019) 13:2406–21. 10.1002/1878-0261.12568

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 8.

  AsciertoPABifulcoCBuonaguroLEmensLAFerrisRLFoxBAet al. Perspectives in immunotherapy: meeting report from the “Immunotherapy Bridge 2018” (28–29 November, 2018, Naples, Italy). J ImmunoTher Cancer. (2019) 7:332. 10.1186/s40425-019-0798-3

  • CrossRef
  • Google Scholar

• 9.

  WuY-LMokTSKKudabaIKowalskiDMChoBCTurnaHZet al. Pembrolizumab versus chemotherapy for previously untreated, PD-L1-expressing, locally advanced or metastatic non-small-cell lung cancer (KEYNOTE-042): a randomised, open-label, controlled, phase3 trial. Lancet. (2019) 393:1819–30. 10.1016/S0140-6736(18)32409-7

  • CrossRef
  • Google Scholar

• 10.

  CohenRRousseauBVidalJColleRDiazLAAndréT. Immune checkpoint inhibition in colorectal cancer: microsatellite instability and beyond. Target Oncol. (2019) 15:11–24. 10.1007/s11523-019-00690-0

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 11.

  AcsBAhmedFSGuptaSFai WongPGartrellRDSarin PradhanJet al. An open source automated tumor infiltrating lymphocyte algorithm for prognosis in melanoma. Nat Commun. (2019) 10:5440. 10.1038/s41467-019-13043-2

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 12.

  FanJYinZXuJWuFHuangQYangLet al. Circulating microRNAs predict the response to anti-PD-1 therapy in non-small cell lung cancer. Genomics. (2019) 112:2063–71. 10.1016/j.ygeno.2019.11.019

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 13.

  PratANavarroAParéLReguartNGalvánPPascualTet al. Immune-related gene expression profiling after PD-1 blockade in non–small cell lung carcinoma, head and neck squamous cell carcinoma, and melanoma. Cancer Res. (2017) 77:3540–50. 10.1158/0008-5472.CAN-16-3556

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 14.

  SteinJELipsonEJCottrellTRFordePMAndersRACimino-MathewsAet al. Pan-tumor pathologic scoring of response to PD-(L)1 blockade. Clin Cancer Res. (2019) 26:545–51. 10.1158/1078-0432.CCR-19-2379

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 15.

  LiBCuiYDiehnMLiR. Development and validation of an individualized immune prognostic signature in early-stage nonsquamous non-small cell lung cancer. JAMA Oncol. (2017) 3:1529. 10.1001/jamaoncol.2017.1609

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 16.

  BhattacharyaSAndorfSGomesLDunnPSchaeferHPontiusJet al. ImmPort: disseminating data to the public for the future of immunology. Immunol Res. (2014) 58:234–9. 10.1007/s12026-014-8516-1

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 17.

  MeiSMeyerCAZhengRQinQWuQJiangPet al. Cistrome cancer: a web resource for integrative gene regulation modeling in cancer. Cancer Res. (2017) 77:e19–22. 10.1158/0008-5472.CAN-17-0327

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 18.

  RitchieMEPhipsonBWuDHuYLawCWShiWet al. limma powers differential expression analyses for RNA-sequencing and microarray studies. Nucl Acids Res. (2015) 43:e47. 10.1093/nar/gkv007

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 19.

  DennisGShermanBTHosackDAYangJGaoWLaneHCet al. DAVID: database for annotation, visualization, and integrated discovery. Genome Biol. (2003) 4:P3. 10.1186/gb-2003-4-5-p3

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 20.

  Sánchez-CaboFWalterWRicoteM. GOplot: an R package for visually combining expression data with functional analysis. Bioinformatics. (2015) 31:2912–4. 10.1093/bioinformatics/btv300

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 21.

  KanehisaMFurumichiMTanabeMSatoYMorishimaK. KEGG: new perspectives on genomes, pathways, diseases and drugs. Nucl Acids Res. (2017) 45:D353–61. 10.1093/nar/gkw1092

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 22.

  McNeilBJHanleyJA. The meaning and use of the area under a receiver operating characteristic (ROC) curve. Radiology. (1982) 143:29–36. 10.1148/radiology.143.1.7063747

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 23.

  LiTFanJWangBTraughNChenQLiuJSet al. TIMER: a web server for comprehensive analysis of tumor-infiltrating immune cells. Cancer Res. (2017) 77:e108–10. 10.1158/0008-5472.CAN-17-0307

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 24.

  GePWangWLiLZhangGGaoZTangZet al. Profiles of immune cell infiltration and immune-related genes in the tumor microenvironment of colorectal cancer. Biomed Pharmacother. (2019) 118:109228. 10.1016/j.biopha.2019.109228

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 25.

  SaigiMAlburquerque-BejarJJMcLeer-Florin APereiraCProsERomeroOAet al. MET-oncogenic and JAK2-inactivating alterations are independent factors that affect regulation of PD-L1 expression in lung cancer. Clin Cancer Res. (2018) 24:4579–87. 10.1158/1078-0432.CCR-18-0267

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 26.

  VerdeilGLawrenceTSchmittVAuphanA. Targeting STAT3 and STAT5 in tumor-associated immune cells to improve immunotherapy. Cancers. (2019) 11:1832. 10.3390/cancers11121832

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 27.

  BerglundAMillsMPutneyRMHamaidiIMuléJKimS. Methylation of immune synapse genes modulates tumor immunogenicity. J Clin Invest. (2019) 130:974–80. 10.1172/JCI131234

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 28.

  VargasAJHarrisCC. Biomarker development in the precision medicine era: lung cancer as a case study. Nat Rev Cancer. (2016) 16:525–37. 10.1038/nrc.2016.56

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 29.

  TaubeJMShollLMRodigSJCottrellTRGiraldoNABarasASet al. Implications of the tumor immune microenvironment for staging and therapeutics. Mod Pathol. (2018) 31:214–34. 10.1038/modpathol.2017.156

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 30.

  LaraODKrishnanSWangZCorvignoSZhongYLyonsYet al. Tumor core biopsies adequately represent immune microenvironment of high-grade serous carcinoma. Sci Rep. (2019) 9:17589. 10.1038/s41598-019-53872-1

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 31.

  LiaoW-YYangC-YHoC-CChenK-YTsaiT-HHsuC-Let al. Association between programmed death-ligand 1 expression, immune microenvironments, and clinical outcomes in epidermal growth factor receptor mutant lung adenocarcinoma patients treated with tyrosine kinase inhibitors. Eur J Cancer. (2019) 124:110–22. 10.1016/j.ejca.2019.10.019

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 32.

  KwonMJ. Emerging immune gene signatures as prognostic or predictive biomarkers in breast cancer. Arch Pharm Res. (2019) 42:947–61. 10.1007/s12272-019-01189-y

  • CrossRef
  • Google Scholar

• 33.

  ZhaoYGeXXuXYuSWangJSunL. Prognostic value and clinicopathological roles of phenotypes of tumour-associated macrophages in colorectal cancer. J Cancer Res Clin Oncol. (2019) 145:3005–19. 10.1007/s00432-019-03041-8

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 34.

  JiangYXieJHuangWChenHXiSHanZet al. Tumor immune microenvironment and chemosensitivity signature for predicting response to chemotherapy in gastric cancer. Cancer Immunol Res. (2019) 7:2065–73. 10.1158/2326-6066.CIR-19-0311

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 35.

  LiJLiuCChenYGaoCWangMMaXet al. Tumor characterization in breast cancer identifies immune-relevant gene signatures associated with prognosis. Front Genet. (2019) 10:1119. 10.3389/fgene.2019.01119

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 36.

  LuYPanX-BHuangJ-LLongYYaoD-S. Prognostic genes in the tumor microenvironment in cervical squamous cell carcinoma. Aging. (2019) 11:10154–66. 10.18632/aging.102429

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 37.

  YangSLiuTChengYBaiYLiangG. Immune cell infiltration as a biomarker for the diagnosis and prognosis of digestive system cancer. Cancer Sci. (2019) 110:3639–49. 10.1111/cas.14216

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 38.

  Della CorteCMBarraGCiaramellaVDi LielloRVicidominiGZappavignaSet al. Antitumor activity of dual blockade of PD-L1 and MEK in NSCLC patients derived three-dimensional spheroid cultures. J Exp Clin Cancer Res. (2019) 38:253. 10.1186/s13046-019-1257-1

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 39.

  TangLLiuJZhuLChenQMengZSunLet al. Curcumin inhibits growth of human NCI-H292 lung squamous cell carcinoma cells by increasing FOXA2 expression. Front Pharmacol. (2018) 9:60. 10.3389/fphar.2018.00060

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 40.

  WeiYGuoXWangZLiuWYangYYuX. LncRNA LINC00163 upregulation suppresses lung cancer development though transcriptionally increasing TCF21 expression. Am J Cancer Res. (2018) 8:2494–506.

  • Pubmed Abstract
  • Google Scholar

• 41.

  XuX-HBaoYWangXYanFGuoSMaYet al. Hypoxic-stabilized EPAS1 proteins transactivate DNMT1 and cause promoter hypermethylation and transcription inhibition of EPAS1 in non-small cell lung cancer. FASEB J. (2018) 32:6694–705. 10.1096/fj.201700715

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 42.

  LiuWTWangYZhangJYeFHuangXHLiBet al. A novel strategy of integrated microarray analysis identifies CENPA, CDK1 and CDC20 as a cluster of diagnostic biomarkers in lung adenocarcinoma. Cancer Lett. (2018) 425:43–53. 10.1016/j.canlet.2018.03.043

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 43.

  Castro-RiveraERanSBrekkenRAMinnaJD. Semaphorin 3B inhibits the phosphatidylinositol 3-Kinase/Akt pathway through neuropilin-1 in lung and breast cancer cells. Cancer Res. (2008) 68:8295–303. 10.1158/0008-5472.CAN-07-6601

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 44.

  BeckTNKorobeynikovVAKudinovAEGeorgopoulosRSolankiNRAndrews-HokeMet al. Anti-müllerian hormone signaling regulates epithelial plasticity and chemoresistance in lung cancer. Cell Rep. (2016) 16:657–71. 10.1016/j.celrep.2016.06.043

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 45.

  HeinbockelLMarwitzSScheufeleSNitschDKuglerCPernerSet al. Epigenetic modifications of the VGF gene in human non-small cell lung cancer tissues pave the way towards enhanced expression. Clin Epigenetics. (2017) 9:123. 10.1186/s13148-017-0423-6

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 46.

  LiJWangJChenYYangLChenS. A prognostic 4-gene expression signature for squamous cell lung carcinoma. J Cell Physiol. (2017) 232:3702–13. 10.1002/jcp.25846

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 47.

  HedrickEMohankumarKSafeS. TGFβ-induced lung cancer cell migration is NR4A1-dependent. Mol Cancer Res. (2018) 16:1991–2002. 10.1158/1541-7786.MCR-18-0366

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 48.

  LiRFangFJiangMWangCMaJKangWet al. STAT3 and NF-kappaB are simultaneously suppressed in dendritic cells in lung cancer. Sci Rep. (2017) 7:45395. 10.1038/srep45395

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 49.

  CarusALadekarlMHagerHPilegaardHNielsenPSDonskovF. Tumor-associated neutrophils and macrophages in non-small cell lung cancer: no immediate impact on patient outcome. Lung Cancer. (2013) 81:130–7. 10.1016/j.lungcan.2013.03.003

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 50.

  DaiFLiuLCheGYuNPuQZhangSet al. The number and microlocalization of tumor-associated immune cells are associated with patient's survival time in non-small cell lung cancer. BMC Cancer. (2010) 10:220. 10.1186/1471-2407-10-220

  • Pubmed Abstract
  • CrossRef
  • Google Scholar