ORIGINAL RESEARCH published: 25 November 2021 doi: 10.3389/fcell.2021.762478 Hypoxic Characteristic Genes Predict Response to Immunotherapy for Urothelial Carcinoma Shuo Hong 1†, Yueming Zhang 1†, Manming Cao 1†, Anqi Lin 1†, Qi Yang 1†, Jian Zhang 1*, Peng Luo 1* and Linlang Guo 2* 1 Department of Oncology, Zhujiang Hospital, Southern Medical University, Guangzhou, China, 2Department of Pathology, Zhujiang Hospital, Southern Medical University, Guangzhou, China Objective: Resistance to immune checkpoint inhibitors (ICIs) has been a massive obstacle Edited by: Dong-Hua Yang, to ICI treatment in metastatic urothelial carcinoma (MUC). Recently, increasing evidence St. John’s University, United States indicates the clinical importance of the association between hypoxia and immune status in Reviewed by: tumor patients. Therefore, it is necessary to investigate the relationship between hypoxia Zhengang Qiu, and prognosis in metastatic urothelial carcinoma. First Affiliated Hospital of Gannan Medical University, China Methods: Transcriptomic and clinical data from 348 MUC patients who underwent ICI Wenjie Shi, Pius-Hospital Oldenburg, Germany treatment from a large phase 2 trial (IMvigor210) were investigated in this study. The cohort was randomly divided into two datasets, a training set (n 213) and a testing set (n 135). *Correspondence: Linlang Guo Data of hypoxia-related genes were downloaded from the molecular signatures database
[email protected](MSigDB), and screened by univariate and multivariate Cox regression analysis to Jian Zhang
[email protected]construct a prognosis-predictive model. The robustness of the model was evaluated in Peng Luo two melanoma cohorts. Furthermore, an external validation cohort, the bladder cancer
[email protected]cohort, from the Cancer Genome Atlas (TCGA) database, was t used to explore the † These authors have contributed mechanism of gene mutation, immune cell infiltration, signaling pathway enrichment, and equally to this work and share first authorship drug sensitivity. Results: We categorized patients as the high- or low- risk group using a four-gene hypoxia Specialty section: This article was submitted to risk model which we constructed. It was found that patients with high-risk scores had Molecular and Cellular Oncology, significantly worse overall survival (OS) compared with those with low-risk scores. The a section of the journal Frontiers in Cell and Developmental prognostic model covers 0.71 of the area under the ROC curve in the training set and 0.59 Biology in the testing set, which is better than the survival prediction of MUC patients using the Received: 22 August 2021 clinical characteristics. Mutation analysis results showed that deletion mutations in RB1, Accepted: 05 November 2021 TP53, TSC1 and KDM6A were correlated with hypoxic status. Immune cell infiltration Published: 25 November 2021 analysis illustrated that the infiltration T cells, B cells, Treg cells, and macrophages was Citation: Hong S, Zhang Y, Cao M, Lin A, correlated with hypoxia. Functional enrichment analysis revealed that a hypoxic Yang Q, Zhang J, Luo P and Guo L microenvironment activated inflammatory pathways, glucose metabolism pathways, (2021) Hypoxic Characteristic Genes Predict Response to Immunotherapy and immune-related pathways. for Urothelial Carcinoma. Front. Cell Dev. Biol. 9:762478. Conclusion: In this investigation, a four-gene hypoxia risk model was developed to doi: 10.3389/fcell.2021.762478 evaluate the degree of hypoxia and prognosis of ICI treatment, which showed a promising Frontiers in Cell and Developmental Biology | www.frontiersin.org 1 November 2021 | Volume 9 | Article 762478 Hong et al. Hypoxia Risk Model for MUC clinical prediction value in MUC. Furthermore, the hypoxia risk model revealed a close relationship between hypoxia and the tumor immune microenvironment. Keywords: metastatic urothelial carcinoma, prognosis model, immune checkpoint inhibitors, hypoxia, immune microenvironment INTRODUCTION Krzywinska and Stockmann, 2018). Furthermore, the hypoxic microenvironment of the tumor prevents adequate oxidation of Metastatic urothelial carcinoma (MUC) is a common malignancy glucose, promotes tumor cells to derive energy not only from which occurs in the urothelial organs of the urinary system oxidative phosphorylation but also from glycolysis, and results in (Humphrey et al., 2016; Moch et al., 2016). According to a the accumulation of lactic acid and adenosine, that lead to Global Data survey, bladder cancer ranks as the 10th most abnormal T cell ratio and T cell dysfunction (Beavis et al., common cancer in the world, and it is four times more 2015). A growing number of studies have revealed that the common in males than females (Bray et al., 2018). At present, hypoxic microenvironment reduces the stimulation of T cells, platinum-based chemotherapy is the first-line treatment for increase the recruitment of immunosuppressive cells such as patients with metastatic urothelial carcinoma (Flaig et al., regulatory T (Treg) cells, and reduce the mobility of antigen- 2020; Witjes et al., 2021). However, it is not uncommon for presenting cells, monocytes, and dendritic cells (Ohta, 2016; Yuen chemotherapy to fail or for a positive treatment response to only and Wong, 2020). Another study suggests that poor prognosis be short term (Koshkin and Grivas, 2018). Therefore, in recent caused by the immune-desert-type colon cancer may be years, new focus has been given to developing treatments that use associated with tumor hypoxia (Craig et al., 2020). However, immune checkpoint inhibitors (ICIs). there is a lack of research focused on hypoxic microenvironments At present, some known immune checkpoint inhibitors, in immunotherapy for patients with MUC. including antibodies against cytotoxic T lymphocyte associated In this study, we constructed a prognostic risk model to protein 4 (CTLA-4) as well as programmed cell death 1 (PD-1) evaluate the impact of hypoxia on the efficacy of immune receptor and its ligand (PD-L1), have displayed promising checkpoint inhibitor (ICI) therapy in patients with MUC. In efficacy in metastatic urothelial carcinoma (MUC) (Darvin addition, we explore the possible mechanisms of hypoxic et al., 2018; Bagchi et al., 2021). According to the 2020 microenvironments and the efficacy of ICI in patients with guidelines of the European Association of Urology (EAU), MUC by looking at biological markers, tumor immune typing, pembrolizumab and atezolizumab have become the first-line gene mutation, and immune microenvironment. treatment option for locally advanced or metastatic urothelial carcinoma after failure of platinum chemotherapy (Witjes et al., 2021). In a phase III clinical trial involving 542 patients with METHODS advanced MUC after platinum chemotherapy, KEYNOTE-045 showed that the median overall survival (mOS) of the Data Collection and Preprocessing pembrolizumab group was longer than that of the second-line Genomic, transcriptomic, and clinical data of patients with chemotherapy group by 3 months (10.3 vs 7.4 months; p 0.002) metastatic urothelial carcinoma treated with an anti-PD-L1 (Bellmunt et al., 2017). Long term results from the same phase III drug (Atezolizumab) were downloaded from a study trial (>2-year follow-up) indicated that pembrolizumab had conducted by Mariathasan et al. (2018). We split the data into longer 1-year and 2-year overall survival (OS) results than a training set and a testing set, with 60% of samples for the chemotherapy (Fradet et al., 2019). However, only part of the training set, and the remaining 40% of samples for the testing set population can benefit from immunotherapy. In a phase II, according to hierarchical random grouping. These groupings multicenter, uncontrolled trial of nivolumab for platinum- were used to construct and evaluate the prognostic model for resistant advanced urothelial carcinoma, the objective response risk of oxygen deficiency. From the Memorial Sloan Kettering rate was 19.6% in 265 patients (Sharma et al., 2017; Powles et al., Cancer Center (MSKCC) database, a cohort of cutaneous skin 2018). A single-arm phase II trial evaluated the efficacy of melanoma (MSKCC skcm) patients receiving anti-CTLA-4 pembrolizumab as the first-line treatment in 370 patients with immunotherapy was recorded in the data published by advanced urothelial carcinoma who were not suitable for cisplatin Samstein et al. (Snyder et al., 2014). We also downloaded the based therapy. Only 5% of patients achieved complete remission transcriptomic data for PD-1 treatment in the GSE78220 data set (Balar et al., 2017). Thus, exploring the mechanism of from the Gene Expression Omnibus (GEO) database (Hugo et al., immunosuppressant in patients with metastatic urothelial 2016) to further analyze the prognostic effect of the hypoxia carcinoma and seeking accurate predictive biomarkers is risk model. warranted. The “TCGAbiolinks” R package (Colaprico et al., 2016) was Due to the rapid growth and abnormal proliferation of solid used to download the TCGA BLCA bladder cancer data set (n tumors, inadequate oxygen supply causes the tumor 412) from The Cancer Genome Atlas (TCGA) database. This data microenvironment to experience uneven blood distribution set included clinical information, genomic data, and and immunosuppression (Choudhry and Harris, 2018; transcriptomic data. Patients with metastatic urothelial Frontiers in Cell and Developmental Biology | www.frontiersin.org 2 November 2021 | Volume 9 | Article 762478 Hong et al. Hypoxia Risk Model for MUC carcinoma were extracted for subsequent analysis (Cancer 2018) was used for mutual exclusion analysis of the driver mutation Genome Atlas Research, 2014; Robertson et al., 2017). The genes in the above cohorts. GSE120736 bladder cancer data set was downloaded from the GEO database to analyze the immune microenvironment. Analysis of the Immune Microenvironment We downloaded the GSE158632 dataset from the GEO Gene length was calculated using the database for subsequent functional validation analysis “TxDb.Hsapiens.UCSC.hg38.knownGene” (https://bioconductor. (Nersisyan et al., 2021). The GSE158632 dataset provides org/packages/) R package. Raw count gene expression data of the high-throughput sequencing data of 18 samples of Caco-2 and MUC and TCGA BLCA data set and the GSE120736 data set were HT-29 cells, nine from the CACO-2 cell lines and nine from the standardized and converted into the transcripts per million (TPM) HT-29 cell lines. Each cell line contains nine samples, among data format. The “xCell” R package was utilized to evaluate the them, three samples are control groups and the other six samples infiltration abundance of immune cells in the tumor are hypoxia groups. microenvironment (TME) (Aran et al., 2017). Differences were considered significant with a p-value less than 0.05. Differential expression analysis in immune-related genes between the MUC Identification of Hypoxia-Related Genes and TCGA BLCA data sets was performed using the “LIMMA” R Impacting Prognosis and Construction of package (Ritchie et al., 2015). The list of immune gene sets was the Risk Prognostic Model sourced from research by Thorsson et al. (2018) and Hao et al. (2018). We collected the hallmark gene sets (Liberzon et al., 2011) from the molecular signatures database (MSigDB) (Liberzon et al., 2015). The Pathway Enrichment Analysis single sample pathway enrichment (ssGSEA) score of the Hallmark The “clusterProfiler” R package (Yu et al., 2012) was used to conduct gene sets of all samples in the MUC cohort was calculated using the gene ontology (GO) analysis (|logFC > 0|, p 0.05) as well as gene set “GSVA” R package (Hänzelmann et al., 2013). The relationship of the enrichment analysis (GSEA) (Subramanian et al., 2005) (|logFC > ssGSEA score of Hallmark gene sets and ICI efficacy and survival was 0|). Gene sets for GSEA enrichment analysis were downloaded from analyzed using the “LIMMA” and “survival” and “survimner” R the Hallmark gene sets (H), curated gene sets (C2), and ontology packages. Then, the “survival” (https://github.com/therneau/survival) gene sets (C5) in the molecular signatures database (MSigDB). and “survminer” (https://rpkgs.datanovia.com/survminer/) R packages were used to identify genes related to overall survival in Statistical Analysis the hypoxia gene sets in the MUC cohort. Based on the 44 genes Overall survival was estimated using the Kaplan–Meier method, and screened as previously described, we established a four-gene hypoxia the difference between the high- and low- risk groups was examined risk score model for risk stratification using univariate and using log-rank test in each data set. The association of risk scores multivariate Cox regression for the MUC training set. with tumor mutational burden (TMB) and tumor neoantigen n burden (TNB) was analyzed using Pearson correlation analysis. Risk score coefficientpgene expression Wilcoxon’s test was used to test the risk score difference between n1 TCGA phenotype and immune phenotype. The risk scores were then compared between the immune phenotypes through Kruskal- where N 4, gene expression was the expression value of hypoxia Wallis test. Associations between risk scores and ICI efficacy or genes, and the coefficient was the corresponding multivariable driver gene mutation frequency were assessed, using Fisher’s exact Cox regression coefficient. test. The “LIMMA” R package was used to analyze the differential A Kaplan–Meier survival analysis and the log-rank test were genes in the high- and low- risk score groups (p < 0.05). All analyses performed to evaluate the difference of patient survival time. were performed using R software (v4.0.5), and the p-value was According to median overall survival, patients with metastatic bilateral. urothelial carcinoma were divided into two groups. Patients with melanoma were grouped into two groups according to the best cutoff point calculated by the function “surv_cutpoint” of the “survminer” R package. The receiver operating characteristic RESULTS (ROC) curve was used to analyze the sensitivity and specificity Establishment of the Hypoxia Signature in the MUC training and testing sets. Model To investigate the role of hypoxia in ICI treatment, we calculated Analysis of Driver Gene Mutation ssGSEA scores of the 50 pathways set from the GSEA Hallmark gene A list of driver genes was taken from the cancer gene census (CGC) set. We found that genes in the hypoxia pathway was upregulated in database, and panoramic maps of driver gene mutations were patients without response (p < 0.05, Figure 1A). Meanwhile, results generated by “ComplexHeatmap” R package (Gu et al., 2016) for of univariate Cox regression revealed that high score of hypoxia the MUC training set, MUC testing set, and TCGA BLCA set. The ssGSEA was correlated with poor prognosis in patients with MUC top 20 driver genes were selected for the MUC training set and the (p 0.00049, HR 18, 95% CI 3.6–95, Figure 1B). Kaplan-Meier MUC testing set. As for the TCGA BLCA queue, we selected the top survival curves, illustrated that patients with poor prognosis had high 20 driver genes and the other top 20 driver genes in the two queues of expression of hypoxia signature genes (log-rank p 0.0013, HR MUC to analyze. The “Maftools” R package (Mayakonda et al., 1.52, 95% CI 1.17–1.97, Figure 1C). Univariate analysis identified Frontiers in Cell and Developmental Biology | www.frontiersin.org 3 November 2021 | Volume 9 | Article 762478 Hong et al. Hypoxia Risk Model for MUC FIGURE 1 | The expression of hypoxia microenvironment in metastatic urothelial carcinoma (mUC). (A) Histogram showed that the ssGSEA score of the Hallmark pathway set was different in CR/PR vs PD/SD patients (logFC < 0, p < 0.05). (B) The enrichment scores of hypoxia gene set were different in forest map. (C) KM curve showed that patients with high score of hypoxia gene set had poor OS (log rank p < 0.05). (D) The gene in each data set was shown by Wayne map. The forest map shows the genes and coefficients of risk score. forty-four genes significantly related to overall survival in the Validation of the Hypoxia Risk Prognostic Hallmark hypoxia gene set as potential prognostic factors for Model further analysis (Supplementary Figure S1B). Next, four hypoxia To further evaluate the performance of the hypoxia model, we genes, including TKTL1, JMJD6, IRS2 and ANXA2, were identified compared our hypoxia prognostic model with the routine clinical as independent prognostic factors for OS by multivariate analysis prognostic characteristics to ascertain whether our risk (Figure 1E). These identified prognostic factors were applied as basic assessment model was a feasible prognostic tool for MUC indexes in the novel prognostic model. Finally, we developed a patients. We subjected the predictor variables of hypoxia risk hypoxia risk score model to predict OS based on a low-risk hypoxia score, clinical signatures, TMB, and TNB of patients in the MUC gene (TKTL1) and three high-risk genes (JMJD6, IRS2, ANXA2) training set to univariate Cox regression analyses. It was found (Figures 1F–I). that three factors, including hypoxia risk score, TMB, and TNB, Frontiers in Cell and Developmental Biology | www.frontiersin.org 4 November 2021 | Volume 9 | Article 762478 Hong et al. Hypoxia Risk Model for MUC FIGURE 2 | Evaluation of hypoxia risk prognosis model. (A,B) shows the results of a univariate Cox regression and multivariate Cox regression showed that risk score was an independent prognostic factor for patients with mUC treated by ICIs. (C,D) Risk curve showed the relationship between gene expression, hypoxia risk score and survival. (E,H) Kaplan Meier curve showed that the high scores of hypoxia risk were associated with poor prognosis in MUC training set, testing set, MSKCC skcm and GSE78220 data sets. (I,L) ROC curve evaluated the AUC values of risk score, TMB and TNB in the training set and testing set queue, and the training set had better prediction effect (AUC 0.71). ROC curve was used to evaluate the AUC value of risk score predicting 1-year and 3-year survival rate in the training set and testing set cohort. Frontiers in Cell and Developmental Biology | www.frontiersin.org 5 November 2021 | Volume 9 | Article 762478 Hong et al. Hypoxia Risk Model for MUC FIGURE 3 | The interations of clinical features in MUC and hypoxia risk score. (A) The stacked histogram showed that the number of non-responders to ICI in the MUC Training set high risk score subgroup was higher than that in the low score subgroup. (B,C) Kaplan Meier curve showed the survival results of the joint analysis of MUC Training set risk score with TMB and TNB. (D) Box plot showed that the PD-L1 expression in tumor cells of the MUC training set. PD-L1 was higher in tumor cells with high hypoxia risk score. (E) Histogram showed that the number of non-responders to ICI in the MUC testing set high risk score subgroup was higher than that in the low score subgroup. (F,G) KM curve showed the survival results of risk score combined with TMB and TNB in the MUC testing set. (H) Box plot showed the expression of risk score and PD-L1 in tumor cells of the MUC testing set. There was no significant difference in the expression level of risk score among different PD-L1 expression levels. (I–K) Violin diagram shows the distribution of MUC training set, MUC testing set and TCGA BLCA risk score in TCGA molecular subtypes. The results showed that the risk score of TCGA III was higher than that of other types. The distribution of the MUC training set, MUC testing set and TCGA BLCA risk score in immunophenotyping was shown by violin diagram. were significant (p-value < 0.05) (Figure 2A). Next, we found that efficacy in patients with MUC. Collectively, the above results the hypoxia risk scores (HR 2.75, 95% CI 1.683–4.306, p < indicated that the hypoxia risk score model was a favorable 0.001) and TNB (HR 0.73,95% CI 0.571–0.982, p 0.0364) predictor of ICIs treatment efficacy (HR 2.692, 95% CI (Figure 2B) were independent predictors for ICIs treatment 1.683–4.306, p < 0.001). Frontiers in Cell and Developmental Biology | www.frontiersin.org 6 November 2021 | Volume 9 | Article 762478 Hong et al. Hypoxia Risk Model for MUC The training and testing set risk curves (Figures 2C,D) also According to previous studies, the MUC cohort was divided confirmed the accuracy of the model. Patients were categorized into three grades according to the results of the PD-L1 into the high- and low-risk groups according to the median immunohistochemical staining of tumor cells. TC0 indicated hypoxia risk score, and analyzed with Kaplan–Meier survival that the level of PD-L1 was lower than 1%, TC1 was between curves. As shown in Figures 2E,F, patients with high-risk 1 and 5%, and TC2+ was more than 5%. The results showed that scores had shorter overall survival time than those with low- the hypoxia risk score of TC2+ was significantly higher than that risk scores (log-rank p < 0.0001, HR 2.11, 95% CI of TC0 (Figure 3D). However, in the MUC testing set, there was 1.51–2.95; log-rank p < 0.0001, HR 2.11, 95% CI no significant difference in the hypoxia risk score at different TC 1.51–2.95; p <0.0001; log-rank p 0.019, HR 1.62, 95% levels (Figure 3H). Based on the results of immune cell PD-L1 CI 1.07–2.45). Although no significant difference was staining, the MUC cohort was also divided into three grades. IC0 observed across groups in the MSKCC skcm cohort treated indicated that the PD-L1 level was lower than 1%, IC1 indicated with anti-CTLA-4 drug or the GSE78220 melanoma treated that the PD-L1 expression level was between 1 and 5%, and IC2+ with anti-PD-1 drug, patients with high prognostic scores indicated that the PD-L1 expression level was more than 5%. showed a tendency of short-term OS (Figures 2G,H). There was no significant difference in PD-L1 expression between The area under the ROC curve (AUC) of three independent the MUC training set and the testing set on hypoxia risk scores prognostic factors: hypoxia risk score, TMB, and TNB, was (Supplementary Figures S3C,F). calculated to evaluate the efficacy of the prediction model. The In a study by Thorson et al. (Ritchie et al., 2015), the TCGA area under the curve (AUC) for the hypoxia-based model (AUC BLCA data set was classified into six subtypes according to 0.71) was higher than that of both the TMB and TNB based tumor molecular characteristics. These were C1 (wounding prediction (AUC 0.33, 0.33) in the MUC training set. Similar healing) and C2 (IFN-γ Dominant), C3 (Inflammatory), C4 tendencies were observed in the testing group, in which the areas (Lymphocyte Depleted), C5 (Immunologically Quiet), and C6 under the curve (AUC) of hypoxia risk score, TMB, and TNB (TGF-βDominant). The results show that the risk scores of were 0.59, 0.37 and 0.29, respectively (Figures 2I,J). Furthermore, hypoxia for the C2 type are the highest among all immune we found that the hypoxia risk score model had the best subtypes (Figure 3J). The TCGA phenotype is based on the predictive value at 3 years (training set: 1-year AUC 0.707, TCGA molecular phenotype of bladder cancer (Cancer 3-year AUC 0.722, Figure 2K; test set: 1-year AUC 0.547, 3- Genome Atlas Research, 2014). We observed that the year AUC 0.574, Figure 2L). TCGA type III (basic/square-like) had a high hypoxia risk score, and overexpression of KRT14 and KRT5 proteins (Figures 3I,K). Prognostic Model and Clinical Features of Hypoxia Risk Next, we evaluated the possible associations between hypoxia scores Hypoxia Risk Prognostic Model, Gene and clinical characteristics. We investigated the relationship among Mutation, Co-Occurrence and Mutual the following indicators: hypoxia scores, immunotherapy efficacy, Exclusion Analysis of Mutated Genes PD-L1 expression level on the tumor surface, PD-L1 expression level Previous studies have shown that the chronic hypoxic in immune cells, immunogenicity related factors, TCGA molecular microenvironment reduces DNA repair ability and impairs the phenotype, and tumor immune phenotype. DNA repair system. Therefore, we further distinguish the As shown in Figure 3, patients with high-risk scores had an function of hypoxic microenvironment on gene mutations in inadequate response to anti-PD-L1 inhibitors (p 0.000047, metastatic urothelial carcinoma (Figures 4A–C). In the MUC Figure 3A). Despite no statistical difference in the testing set, training set, TERT (64 vs 65%) and TP53 (49 vs 51%) were in the patients with high-risk scores illustrated a trend of poor response high- and low- risk groups, among which TERT and TP53 were to ICI treatment (p 0.37, Figure 3B). We further performed known to have short mutations as the major mutation. The survival analysis on hypoxia risk scores, TMB, and TNB, to mutation frequencies of ARID1A, KDM6A, FGFR3, and Rb1 explore the relationship between the survival rate and were low in the subgroup with high-risk scores. Notably, there prediction factors that may affect the efficacy of ICIs. We was no significant difference in the mutation frequency of these found that high-TMB and low-risk score patients have longer genes in any group. OS (paired log rank test p 0.00000067). Significantly increased In the MUC testing set, TERT (70 vs 60%) and TP53 (49 vs OS was observed in high-TNB and low-risk patients compared 57%) had high frequencies of known short mutations in both the with low-TNB and high-risk patients (paired log-rank test p high-risk and low-risk subgroups. However, in contrast to the 0.00074, Figures 3B,C). In the MUC testing set, the high-TMB MUC training group, the mutation frequency of ARID1A, and low-risk group showed a similar trend of association with OS KDM6A, and Rb1 was higher in the subgroup with high-risk in the training set (paired log-rank test p 0.055). Additionally, scores. There was no significant difference in the mutation patients with high TNB and a low hypoxia risk score had longer frequency of these genes in any group. In the TCGA BLCA OS (paired log-rank test, p 0.046, Figures 3F,G). These results cohort, Rb1, KDM6A, and FGFR3 showed significant differences suggest that the risk score of hypoxia combined with in mutation frequency among the hypoxia risk groups. The high- characteristics of tumor immunogenicity are good predictors risk group had a higher mutation frequency of Rb1 (26%) than of survival and the efficacy of anti-PD-L1 inhibitors. that of the low-risk subgroup (11%), whereas the high-risk group Frontiers in Cell and Developmental Biology | www.frontiersin.org 7 November 2021 | Volume 9 | Article 762478 Hong et al. Hypoxia Risk Model for MUC FIGURE 4 | Panoramic view of metastatic urothelial carcinoma and TCGA BLCA mutation gene, gene co mutation and mutual exclusion analysis. (A) Panoramic view of the top20 driving gene mutation of the MUC training set. (B) Panorama of top20 driving gene mutation of the MUC testing set. (C) Panorama of top driving gene mutation in the TCGA BLCA cohort. Frontiers in Cell and Developmental Biology | www.frontiersin.org 8 November 2021 | Volume 9 | Article 762478 Hong et al. Hypoxia Risk Model for MUC FIGURE 5 | Changes of immune components in tumor hypoxia microenvironment. (A–D) Diagram shows the immune microenvironment infiltration score of the training set, testing set, TCGA BLCA and GSE120736 datasets in metastatic urothelial carcinoma. The figure shows the immune cells with statistical difference in the analysis results (p < 0.05), and the results show that T cells, B cells, macrophages, and Treg cells were more infiltrated in the high hypoxia risk score subgroup. (CD4 + Tcm: CD4+ central memory T cells, CD8 + Tcm: CD8+ central memory T cells, NKT: natural killer T cells). had lower mutation frequencies of KDM6A (22%) and FGFR3 and FGFR3 had co-mutations. TP53 and FGFR3 had (10%) than that of the low-risk subgroup. mutually exclusive mutations. In the TCGA BLCA cohort Diagrams of mutation genes with computation and mutual with low hypoxia risk scores, Rb1 showed co-mutation with exclusion analysis (Supplementary Figures S4A–C) show TP53 and ARID1A, and Rb1 had a mutually exclusive the results of three clinical cohorts. In the high-risk MUC mutation with FGFR3. training set, RB1 and TP53, ERB2 and TSC1, Rb1 and ARID1A had co-mutations. In the low-risk set, TP53 was Immune Correlation Analysis mutable with FGFR3 and CDKN2A, TSC1 and EP300, Rb1 Some studies suggest that a hypoxic microenvironment might and ERBB2, PIK3CA and STAG2. In the TCGA BLCA data affect the activation of infiltrating immune cells and the immune set with high hypoxia risk scores, Rb1 and TP53, KDM6A, response of tumor cells. Therefore, we examined the possible Frontiers in Cell and Developmental Biology | www.frontiersin.org 9 November 2021 | Volume 9 | Article 762478 Hong et al. Hypoxia Risk Model for MUC FIGURE 6 | The results of GSEA analysis of risk score group. (A,B) Histogram showed the enrichment of up-regulated genes (p < 0.05, logFC > 0) and down regulated genes (p < 0.05, logfc < 0) in the top15 pathways of the GO gene set (p < 0.05, logFC < 0). The pathways were mainly the intercellular and hypoxia related pathways. (C,D) Results of GSEA analysis on inflammatory pathway, immune pathway, glucose metabolism and lipid metabolism in metastatic urothelial carcinoma (FigC) and TCGA BLCA (FigD) cohort (p < 0.05). Frontiers in Cell and Developmental Biology | www.frontiersin.org 10 November 2021 | Volume 9 | Article 762478 Hong et al. Hypoxia Risk Model for MUC FIGURE 7 | Results of drug sensitivity analysis of GDSC and CMAP. (A) Thermogram showed the small molecule drugs in the CMAP analysis results. Blue means that the cell expression profile treated with the small molecule drugs has similar effect with the low hypoxia score subgroup, and red represents that the effect of the cell expression profile treated with the small molecule drugs is similar to that of the high hypoxia score subgroup (|score| > 60). (B) The drug molecular mechanism of small molecule drugs according to the above CMAP results. Frontiers in Cell and Developmental Biology | www.frontiersin.org 11 November 2021 | Volume 9 | Article 762478 Hong et al. Hypoxia Risk Model for MUC associations between hypoxia and immune microenvironment. group into the low-risk group. Then, we performed GO analysis We used the xCell method to calculate the infiltration of immune comparing the high- and low-risk groups. As is shown in cell components in the training set, testing set, TCGA BLCA Supplementary Figures S8A,C, RNA and mRNA catabolic cohort, and GSE120736 cohort downloaded from the GEO processes were activated under hypoxia in the CACO2 cell database. line. Similarly, the GO analysis demonstrated that the hypoxia As is shown in Figure 5, we found that the number of CD4+ microenvironment was significantly associated with cellular T cells was higher in the high-risk subgroup than in the low-risk response to topologically incorrect protein and regulation of subgroup. And the immunosuppression-related cells, such as autophagy in the HT29 cell line. These results indicated that Treg cells and macrophages, were significantly higher in the the low level of oxygen during hypoxic conditions leading to high-risk subgroup than in the low-risk subgroup, whereas the increased abnormal protein expression and cell membrane immune cell scores tended to be lower in the high-risk subgroup. instability of tumor cells. In the MUC training set, the high-risk subgroup showed high Next, we calculated the activation degree of the glucose metabolic immune cell infiltration scores in the following cell types: Treg pathway through the GSEA algorithm to verify the role of glucose cells, Th2 cells, macrophages, macrophages M1, macrophages metabolism in the hypoxic tumor microenvironment. Pathway M2, CD4+ T cells, CD4+ central memory T cells (CD4 + Tcm). In enrichment analysis indicated that glucose catabolic pathway was contrast, naive B cells, CD8+ T cells, and CD8+ central memory significantly enriched under hypoxic microenvironment both in the T cells (CD8 + Tcm) remained at a relatively low level in the high- CACO2 and HT29 cell lines. This result was in consistent to a risk subgroup. previous study from Denko (2008). Immune-related genes were In the TCGA BLCA cohort, significantly decreased expression reported to orchestrate tumor-associated immune responses; of naive CD4+ T cells, CD4+ central memory T cells (CD4 + therefore, we further investigated the differences in the expression Tcm), and naive CD8+ T cells was observed in the high-risk of immune-related genes. As is shown in Supplementary Figure subgroup, while the expression of CD8 T cells, CD8+ central S8G, the expression of immune-related genes ACTN4, TMBIM6, memory T cells (CD8 + Tcm), Th2 cells, and macrophages M1 DAZAP2 and CAMTA1 were significantly up-regulated in the tended to be low in the low-risk subgroup. In the GSE120736 hypoxic groups. bladder cancer cohort, B cells and CD4+ central memory T cells (CD4 + Tcm) were lower in the high-risk subgroup than in the Drug Sensitivity Analysis low-risk subgroup. In comparison, the number of natural killer T To explore the drug sensitivity using our hypoxia risk (NKT) cells was high in the high hypoxia risk score subgroup stratification system, we conducted a drug sensitivity analysis (Figures 5A–D). The differentially expressed genes were HLA- of 138 small and medium molecular drugs through the GDSC DPA1, HLA-DPA2, BTN3A2, GZMA, CD27, PDCD1, and database. Clinically, cisplatin, gemcitabine, and methotrexate are TIGIT (Supplementary Figure S5A). commonly used for chemotherapy in urothelial carcinoma. These drugs did not show superior drug sensitivity in the subgroup with GSEA Analysis and Functional Verification high hypoxia scores (p > 0.05) (Supplementary Figure S1D). Next, we performed Gene Ontology (GO) analysis and GSEA We also used CMAP to analyze the similarities in gene expression analysis to elucidate the biochemical functions. We selected profiles between other drugs and the MUC hypoxia risk score group. differentially expressed genes (DEGs) in the high-risk groups The results show that protein synthesis inhibitor, bacterial cell wall compared with low-risk groups (p < 0.05, logFC > 0) for a GO synthesis inhibitor, farnesyltransferase inhibitor, glycogen synthase pathway enrichment analysis. In terms of the top15 GO kinase inhibitor, and HSP inhibitor were effective in patients with a pathways, the high-risk subgroup was mainly concentrated in high hypoxia score. These drugs may reverse the hypoxia the extracellular matrix remodeling related pathways microenvironment of patients and changing it into a state of (Figures 6A,B). mild hypoxia. To gain further insight into the potential mechanisms, we used GSEA to explore the relationship between hypoxia microenvironment and lipid metabolism, glucose metabolism, DISCUSSION and immune pathways. In terms of metabolic pathways, the genes of the high-risk subgroup were mainly enriched in the glucose Metastatic urothelial carcinoma usually responds poorly to metabolism-related pathway. Meanwhile, the genes of the low- treatment with immunosuppressive agents. In this study, we risk subgroup were mainly concentrated in lipid metabolism- speculate that the insensitivity of some MUCs to ICI may be related pathways. T cells, macrophages, and NK cells were related to the hypoxic microenvironment. Therefore, we screened significantly enriched in the high-risk subgroup in the the hypoxia-related genes to construct a risk model to evaluate immune process-related pathways but not in the low-risk hypoxia microenvironment and predict the survival of patients subgroup. Meanwhile, inflammation-related pathways were with MUC undergoing ICI treatment. We constructed a hypoxia enriched considerably in the high-risk subgroup (Figures 6C,D). risk prognostic model based on four hypoxia-related genes To further verify the associated signaling pathways activated in (TKTL1, JMJD6, IRS2, ANXA2) through multivariate Cox hypoxia microenvironment, we downloaded the GSE158632 regression analysis. TKTL1 was negatively correlated with dataset and classified six samples from the hypoxia group into survival rate, while JMJD6, IRS2 and ANXA2 showed a the high-risk group and the other three samples from the control positive correlation. The robustness of the proposed model Frontiers in Cell and Developmental Biology | www.frontiersin.org 12 November 2021 | Volume 9 | Article 762478 Hong et al. Hypoxia Risk Model for MUC was evaluated on multiple cohorts. The results showed that the the competitive uptake of glucose by tumor cells, which model effectively identified distinct subgroups with different promotes T cells to a unfavorable nutritional status and hypoxia risk, indicating that high hypoxia was correlated with inhibits T cells from carrying out their immune functions or poor prognosis. Simultaneously, the potential mechanisms of clearing out tumor cells. Additionally, the enhanced glycolysis action were determined by multi-omics studies. activity of tumor cells in a hypoxic environment leads to an acidic We found that TP53, Rb1, KDM6A, and TSC1 experience microenvironment, which also affects the function of T cells mutational inactivation in a hypoxic microenvironment by (Leone and Powell, 2020). The PDCD1 gene was up-regulated in analyzing the mutations of driver genes. TP53 is a known the high hypoxia risk subgroup. PDCD1 encodes PD-1 protein, tumor suppressor gene and expresses p53 protein to regulate an essential protein on the surface of T cells (and other immune the DNA repair system in cells under normal conditions (Zhang cells) that recognizes abnormal cells. It has been found that in an and Zhang, 2015). Rb1 is a known tumor suppressor gene that inflammatory environment, PD-1 protein is overexpressed on the regulates cell cycle (Dyson, 2016). Arakawa et al. found that Rb1 surface of T cells. This overexpression inhibits the expression of mutational inactivation may cause lung cancer resistance to PD-1 PD-1 protein in T cells around the tumor and suppresses a T cell- inhibitors (Arakawa et al., 2021). Our study found that Rb1 and mediated immune response (Baumeister et al., 2016; Multhoff TP53 co-mutate in a hypoxic microenvironment, suggesting that and Vaupel, 2020). In addition, Nicole E. et al. established a Rb1 and TP53 mutational inactivation may cause tumor mouse model with a hypoxia microenvironment to observe resistance to ICIs in a hypoxic microenvironment (Ku et al., possible changes in T cells under hypoxic conditions 2017). KDM6A belongs to the KDM6 family of histone H3 lysine (Scharping et al., 2021). Their research confirmed that the 27 (H3K27) demethylases. KDM6A deletion mutation induce a metabolic stress under hypoxia could accelerate the terminal repressive H3K27 demethylation state and block differentiation cell differentiation, increase reactive oxygen species (ROS) (Chakraborty et al., 2019). Yuichiro et al. (Itoh et al., 2019) found level of T cells, and eventually cause severe T-cell dysfunction, that a KDM6A deletion mutation resulted in the activation of Th1 which further verified our conjecture. and Th2 cell pathways and the down regulation of an One of the crucial mechanisms of tumor invasion and inflammatory response in CD4+ T cells, which is likely to metastasis mediated by a hypoxic microenvironment is the contribute to a pro-tumor microenvironment. Thus, we degradation of fibrin and collagen (Ricard-Blum, 2011; Dragoš consider that a hypoxic microenvironment may promotes the and Kovács, 2017). The results of the GO analysis showed that formation of KDM6A deletion mutation, enhancing the genes related to extracellular matrix remodeling exist in the differentiation of immunosuppressive cells, and ultimately subgroup with a high hypoxia score. The destruction of results in immunological resistance and poor prognosis. Our stromal cells can easily lead to abnormal differentiation and mutation analysis also found that KDM6A and FGFR3 have co- malfunction of T cells, resulting in immunosuppression (Vito occurrence, suggesting that both may lead to immune et al., 2020). Therefore, we believe that hypoxia can promote the resistance. The protein encoded by TSC1 and TSC2 decomposition and reconstruction of the matrix structure of constitutes tuberous sclerosis (TSC) complex, which tumor cells. Additionally, it may inhibit the differentiation of negatively impacts the regulation of mTOR activity, and T cells into Th1 cells and promote the differentiation of T cells participates in the functional regulation of macrophages into Treg cells, thus leading to immunosuppression (Schito and (Yang et al., 2011; Yang et al., 2013). Meanwhile, tumor- Semenza, 2016). associated macrophages tend to differentiate into M2 type Several limitations to the present study should be considered. and inhibit immune response in a hypoxic microenvironment First, although we have included as many ICI treatment cohorts (Samanta and Semenza, 2018). Therefore, unique driver gene as possible to verify the accuracy of the model, the sample size of mutations in a hypoxic microenvironment may enhance the some cohort is small. In addition, the validation cohort used is ability of tumor cells to escape being killed by immune cells or based on retrospective data, so the model needs to be further affect the function of immune-related cells. This may lead to a validated in large-scale clinical studies. Finally, the theoretical poor response to immunosuppressive therapy. mechanisms need to be further verified by biological The hypoxia microenvironment facilitates glucose uptake in experiments. malignant tumor cells, therefore affects the functions of some of the most important immunologically active cells, especially the recognition and clearance functions of T cells. We found that the CONCLUSION infiltration of CD4+ T cells in MUC was slightly higher than in the high-risk subgroup. Treg cells, macrophages, and Th2 cells play Our study establishes a novel four-gene risk stratification system an inhibitory role in ICI treatment, also have a higher infiltration that could inform ICIs treatment response in urothelial degree in the high-risk subset (Gajewski et al., 2013; Samanta and carcinoma with by evaluating hypoxic microenvironment. In Semenza, 2018). The research of Chang et al. (2015) shows that addition, we systematically explained the reasons for the poor tumor cells compete with T cells for glucose in a mouse model, efficacy of ICI treatment in MUC with a hypoxic and the ability of tumor cells to utilize glucose for energy is more microenvironment from the perspectives of genome, potent than that of T cells, which results in the inhibition of transcriptome sequencing data, and the immune nutritional metabolism in T cells. Hypoxia increases the microenvironment. The validation of our results and the activation of glucose metabolism-related pathways as well as underlying mechanisms remain to be studied further. Frontiers in Cell and Developmental Biology | www.frontiersin.org 13 November 2021 | Volume 9 | Article 762478 Hong et al. Hypoxia Risk Model for MUC DATA AVAILABILITY STATEMENT FUNDING The datasets supporting the conclusions of this article are available in This work was supported by the Natural Science Foundation of the R package "IMvigor210CoreBiologies" (http://research-pub.gene. Guangdong Province (Grant No. 2018A030313846 and com/IMvigor210CoreBiologies), and GEOdatabase (https://www. 2021A1515012593), the Science and Technology Planning ncbi.nlm.nih.gov/geo/query/acc.cgi?accGSE120736, https://www. Project of Guangdong Province (Grant No. ncbi.nlm.nih.gov/geo/query/acc.cgi?accGSE78220, https://www. 2019A030317020) and the National Natural Science ncbi.nlm.nih.gov/geo/query/acc.cgi?accGSE158632). Foundation of China (Grant No. 81802257, 81871859, 81772457, 82172750, and 82172811). AUTHOR CONTRIBUTIONS SUPPLEMENTARY MATERIAL LG, JZ, and PL conceived and supervised the article. SH analyzed the data and wrote the manuscript. YZ and AL revised the The Supplementary Material for this article can be found online at: manuscript. MC and QY verified the figures. All authors https://www.frontiersin.org/articles/10.3389/fcell.2021.762478/ contributed to the article and approved the final manuscript. full#supplementary-material Colaprico, A., Silva, T. C., Olsen, C., Garofano, L., Cava, C., Garolini, D., et al. REFERENCES (2016). TCGAbiolinks: an R/Bioconductor Package for Integrative Analysis of TCGA Data. Nucleic Acids Res. 44 (8), e71. doi:10.1093/nar/gkv1507 Arakawa, S., Yoshida, T., Shirasawa, M., Takayanagi, D., Yagishita, S., Motoi, N., Craig, S. G., Humphries, M. P., Alderdice, M., Bingham, V., Richman, S. D., et al. (2021). 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