Colorectal cancer (CRC) is one of the most devastating diseases that accounts for numerous deaths worldwide. Tumor cell-autonomous pathways, such as the oncogenic signaling activation, significantly contribute to CRC progression and metastasis. Recent accumulating evidence suggests that the CRC microenvironment also profoundly promotes or represses this process. As the roles of the tumor microenvironment (TME) in CRC progression and metastasis is gradually uncovered, the importance of these non-cell-autonomous signaling pathways is appreciated. However, we are still at the beginning of this TME function exploring process. In this review, we summarize the current understanding of the TME in CRC progression and metastasis by focusing on the gut microbiota and host cellular and non-cellular components. We also briefly discuss TME-remodeling therapies in CRC.

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Tumor Microenvironment Shapes Colorectal Cancer Progression, Metastasis, and Treatment Responses

Background Soft-tissue sarcoma (STS) represents a rare and diverse cohort of solid tumors, and encompasses over 100 various histologic and molecular subtypes. In recent years, RNA modifications including m6A, m5C, m1A, and m7G have been demonstrated to regulate immune response and tumorigenesis. Nevertheless, the cross-talk among these RNA modification regulators and related effects upon the tumor microenvironment (TME), immune infiltrates, and immunotherapy in STS remain poorly understood. Methods In this study, we comprehensively investigated transcriptional and genetic alterations of 32 RNA modification regulators in STS patients from The Cancer Genome Atlas (TCGA) cohort and validated them in the Gene Expression Omnibus (GEO) cohort. Single-cell transcriptomes were introduced to identify regulators within specific cell types, with own sequencing data and RT-qPCR conducted for biological validation. Distinct regulator clusters and regulator gene subtypes were identified by using unsupervised consensus clustering analysis. We further built the regulator score model based on the prognostic regulator-related differentially expressed genes (DEGs), which could be used to quantitatively assess the risk for individual STS patients. The clinical and biological characteristics of different regulator score groups were further examined. Results A total of 455 patients with STS were included in this analysis. The network of 32 RNA modification regulators demonstrated significant correlations within multiple different RNA modification types. Distinct regulator clusters and regulator gene subtypes were characterized by markedly different prognoses and TME landscapes. The low regulator score group in the TCGA-SARC cohort was characterized by poor prognosis. The robustness of the scoring model was further confirmed by the external validation in GSE30929 and GSE17674. The regulator score was negatively correlated with CD4+ T cell, Th2 cell, and Treg cell recruitment and most immunotherapy-predicted pathways, and was also associated with immunotherapy efficacy. Conclusions Overall, our study is the first to demonstrate the cross-talk of RNA modification regulators and the potential roles in TME and immune infiltrates in STS. The individualized assessment based on the regulator score model could facilitate and optimize personalized treatment.

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Cross-Talk of Multiple Types of RNA Modification Regulators Uncovers the Tumor Microenvironment and Immune Infiltrates in Soft Tissue Sarcoma

Pancreatic cancer is the fourth leading cause of cancer death in the United States. The main methods of treating pancreatic cancer are surgery and chemotherapy, but the treatment efficacy is low with a poor prognosis. Immunotherapy represented by PD-1/PD-L1 has brought a milestone progress in the treatment of pancreatic cancer. However, the unique tumor microenvironment of pancreatic cancer presents challenges for immunotherapy. In addition, m6A is a common RNA modification and a potential molecular target in tumor therapy. The expression pattern of m6A in pancreatic cancer is still unclear. LncRNAs also play an essential role in pancreatic cancer development and treatment. In this study, we found that some m6A regulators were significantly elevated in pancreatic cancer and associated with the expression of PD-1/PD-L1. Moreover, we observed that METTL3 can increase the expression of PD-L1. Notably, METTL3 positively regulates the expression of lncRNA MALAT1 in pancreatic cancer cells. Strikingly, lncRNA MALAT1 increased the expression of PD-L1 in pancreatic cancer cells. This finding indicated that METTL3 regulated the expression of PD-L1 possibly via targeting lncRNA MALAT1 in pancreatic cancer cells. Lastly, MALAT1 governed the viability of pancreatic cancer cells. Taken together, lncRNA MALAT1 is involved in METTL3-mediated promotion of PD-L1 expression in pancreatic cancer.

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LncRNA MALAT1 regulates METTL3-mediated PD-L1 expression and immune infiltrates in pancreatic cancer

Background Pancreatic adenocarcinoma (PAAD) is one of the most malignant cancers and has a poor prognosis. As a critical RNA modification, 5-methylcytosine (m5C) has been reported to regulate tumor progression, including PAAD progression. However, a comprehensive analysis of m5C regulators in PAAD is lacking. Methods In the present study, PAAD datasets were obtained from the Gene Expression Omnibus (GEO), The Cancer Genome Atlas (TCGA), International Cancer Genome Consortium (ICGC), and ArrayExpress databases. The expression pattern of m5C regulators were analyzed and patients were divided into different m5C clusters according to consensus clustering based on m5C regulators. Additionally, m5C differentially expressed genes (DEGs) were determined using Limma package. Based on m5C DEGs, patients were divided into m5C gene clusters. Moreover, m5C gene signatures were derived from m5C DEGs and a quantitative indicator, the m5C score, was developed from the m5C gene signatures. Results Our study showed that m5C regulators were differentially expressed in patients with PAAD. The m5C clusters and gene clusters based on m5C regulators and m5C DEGs were related to immune cell infiltration, immune-related genes and patient survival status, indicating that m5C modification play a central role in regulating PAAD development partly by modulating immune microenvironment. Additionally, a quantitative indicator, the m5C score, was also developed and was related to a series of immune-related indicators. Moreover, the m5C score precisely predicted the immunotherapy response and prognosis of patients with PAAD. Conclusion In summary, we confirmed that m5C regulators regulate PAAD development by modulating the immune microenvironment. In addition, a quantitative indicator, the m5C score, was developed to predict immunotherapy response and prognosis and assisted in identifying PAAD patients suitable for tailored immunotherapy strategies.

https://www.frontiersin.org/articles/10.3389/fonc.2022.851766/pdf

Comprehensive Analysis of 5-Methylcytosine (m5C) Regulators and the Immune Microenvironment in Pancreatic Adenocarcinoma to Aid Immunotherapy

Background Ferroptosis is one of the main mechanisms of sorafenib against hepatocellular carcinoma (HCC). Epithelial-mesenchymal transition (EMT) plays an important role in the heterogeneity, tumor metastasis, immunosuppressive microenvironment, and drug resistance of HCC. However, there are few studies looking into the relationship between ferroptosis and EMT and how they may affect the prognosis of HCC collectively. Methods We downloaded gene expression and clinical data of HCC patients from the Cancer Genome Atlas (TCGA) and International Cancer Genome Consortium (ICGC) databases for prognostic model construction and validation respectively. The Least absolute shrinkage and selection operator (LASSO) Cox regression was used for model construction. The predictive ability of the model was assessed by Kaplan–Meier survival analysis and receiver operating characteristic (ROC) curve. We performed the expression profiles analysis to evaluate the ferroptosis and EMT state. CIBERSORT and single-sample Gene Set Enrichment Analysis (ssGSEA) methods were used for immune infiltration analysis. Results A total of thirteen crucial genes were identified for ferroptosis-related and EMT-related prognostic model (FEPM) stratifying patients into two risk groups. The high-FEPM group had shorter overall survivals than the low-FEPM group (p<0.0001 in the TCGA cohort and p<0.05 in the ICGC cohort). The FEPM score was proved to be an independent prognostic risk factor (HR>1, p<0.01). Furthermore, the expression profiles analysis suggested that the high-FEPM group appeared to have a more suppressive ferroptosis status and a more active EMT status than the low- FEPM group. Immune infiltration analysis showed that the myeloid-derived suppressor cells (MDSCs), and regulatory T cells (Tregs) were highly enriched in the high-FEPM group. Finally, a nomogram enrolling FEPM score and TNM stage was constructed showing outstanding predictive capacity for the prognosis of patients in the two cohorts. Conclusion In conclusion, we developed a ferroptosis-related and EMT-related prognostic model, which could help predict overall survival for HCC patients. It might provide a new idea for predicting the response to targeted therapies and immunotherapies in HCC patients.

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Prognostic prediction and immune infiltration analysis based on ferroptosis and EMT state in hepatocellular carcinoma

Pancreatic cancer (PAAD) is one of the most malignant cancers and immune microenvironment has been proved to be involved in pathogenesis of PAAD. m6A modification, related to the expression of m6A regulators, participates in the development of multiple cancers. However, the correlation between m6A regulators and immune microenvironment was largely unknown in PAAD. And because of the small sample size of pancreatic cancer in the TCGA database, it is not enough to draw a convincing conclusion. In the present study, we downloaded seven pancreatic cancer datasets with survival data and removed batch effects among these datasets to be used as the PAAD cohort to analyze the immune landscape of PAAD and the expression pattern of m6A regulators and divided the integrated dataset into cluster 1 and cluster 2 by consensus clustering for m6A regulators. Lower m6A regulators were found to be related to higher immune cell infiltration and a better survival. Moreover, we identified six m6A regulators and constructed the prognostic signature of m6A regulators. Patients with low-risk score had a higher response to immune checkpoint inhibitor and a longer overall survival. To figure out the underlying mechanism, we analyzed the cancer immunity cycle, most altered genes, gene set enrichment analysis (GSEA) and gene set variation analysis (GSVA) in risk subtypes. In summary, the present study proved m6A regulators modulated the PAAD immune microenvironment. And risk scores served as predictive indicator for immunotherapy and played a prognostic role for PAAD patients. Our study provided novel therapeutic targets to improve immunotherapy efficacy.

Comprehensive Analysis of m6A RNA Methylation Regulators and the Immune Microenvironment to Aid Immunotherapy in Pancreatic Cancer.


 Background:Colorectal cancer (CRC) is one of the most malignant cancers and its pathological mechanism is largely unknown.Unfolded protein response and ferroptosis are both critical factors involved in CRC development. However, their relationship in CRC remains to be explored. Methods:In this study, erastin was used to induce ferroptosis in CRC cells. Cell viability and apoptosis were assessed by CCK-8 and colony formation assayand annexin V/propidium iodide staining, respectively. Ferroptosis was confirmed by the detection of glutathione, malondialdehyde, and lipid reactive oxygen species. Unfolded protein response-related proteins and GPX4 protein were analyzed by western blotting. The CRC datasetswere analyzed using the R software, GEPIA2 and TIMER2.0. Results:The results indicated that GPX4 was decreased when treated with the ferroptosis inducer erastin. As an intrinsic protective pathway, the unfolded protein response was activated and HSPA5 was increasedduring ferroptosis. HSPA5 was found to attenuateerastin-induced GPX4 decrease, repress ferroptosis, and promote CRC cell growth both in vitro and in vivo. Mechanistically, HSPA5 bounddirectly to GPX4 andthe interaction between HSPA5 and GPX4increased when treated with erastinfor a short time period. Although the HSPA5-GPX4 interaction failed to completely reverse erastin-induced GPX4 decrease, HSPA5 slowed down GPX4 degradation process and gave CRC cells more time to adjust to erastin toxicity. Additionally, HSPA5 was demonstrated to play a diagnostic role and correlated to immune microenvironment in CRC patients.Conclusion:Our study demonstrates that increased HSPA5 was an intrinsic protective strategy to resist ferroptosis. Specifically, HSPA5 restrained ferroptosis to promote colorectal cancer development by maintaining GPX4 stability. Our study provides potential diagnostic and therapeutic targets for patients with CRC.

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HSPA5 Repressed Ferroptosis to Promote Colorectal Cancer Development by Maintaining GPX4 Stability

Epithelium-specific Ets protein 3 (Ese-3), a member of the Ets family of transcription factors, plays an important role in the development of cancers. However, little is known concerning its role in colon cancer (CC). In this study, we demonstrate that the expression of Ese-3 is upregulated in CC tissues and elevated Ese-3 expression is relationship with advanced T stage (P=0.037) and poor disease-free survival (DFS, P=0.044). Univariate and multivariate cox regression analyses show that Ese-3 expression may be an independent prognostic value for CC patients. Moreover, Ese-3 knockdown suppresses CC cell proliferation in vitro and in vivo, while Ese-3 overexpression has the opposite result. Further, we first demonstrate that EHD2 and INPP4B are the downstream genes of Ese-3. Subsequent investigation find that EHD2 is downregulated in CC tissues and knockdown of EHD2 significantly increase CC cell proliferation in vitro and vivo. Our findings reveal that Ese-3 promotes CC cell proliferation by downregulating EHD2 and transactivating INPP4B, and targeting the pathway may be a promising therapeutic target for CC patients.

Ronglin Wang

Papers

Comprehensive Analysis of m6A RNA Methylation Regulators and the Immune Microenvironment to Aid Immunotherapy in Pancreatic Cancer.

HSPA5 Repressed Ferroptosis to Promote Colorectal Cancer Development by Maintaining GPX4 Stability

Ese-3 contributes to colon cancer progression by downregulating EHD2 and transactivating INPP4B.