Expression and prognostic value of E2F activators in NSCLC and subtypes: a research based on bioinformatics analysis

Current concepts of the crosstalk between lncRNA and E2F1: shedding light on the cancer therapy

Long noncoding RNAs (lncRNAs) constitute a distinctive subset of RNA molecules with limited protein-coding potential, which exert crucial impacts on various biological activities. In the context of cancer, dysregulated lncRNAs function as essential regulators that affect tumor initiation and malignant progression. These lncRNAs serve as competitive endogenous RNAs (ceRNAs) through sponging microRNAs and regulating the expression of targeted genes. Moreover, they also directly bind to RNA-binding proteins, which can be integrated into a complex mechanistic network. E2F1, an extensively studied transcription factor, mediates multiple malignant behaviors by regulating cell cycle progression, tumor metastasis, and therapeutic response. Emerging evidence suggests that lncRNAs play a pivotal role in regulating the E2F1 pathway. This review aims to elucidate the intricate gene regulatory programs between lncRNAs and E2F1 in cancer progression. We elaborate on distinct mechanistic networks involved in cancer progression, emphasizing the potential of the lncRNAs/E2F1 axes as promising targets for cancer therapy. Additionally, we provide novel perspectives on current evidence, limitations, and future directions for targeting lncRNAs in human cancers. Fully deciphering the intricate network of lncRNA/E2F1-mediated regulatory mechanisms in cancer could facilitate the translation of current findings into clinical course, such efforts ultimately significantly improve the clinical prognosis of cancer patients.

Prognostic role of E2F1 gene expression in human cancer: a meta-analysis

OBJECTIVE

E2F1 has been confirmed to be highly expressed in a variety of cancers. To better understand the prognostic value of E2F1 in cancer patients, this study was conducted to comprehensively evaluate the prognostic value of E2F1 in cancer according to published data.

METHOD

PubMed, Web of Science and CNKI database were searched until May 31^th, 2022 by using key words to retrieve the published essays on the role of E2F1 expression in the prognostic value of cancer. The essays were identified according to the inclusion and exclusion criteria. The pooled result of hazard ratio and 95% confidence interval was calculated with Stata17.0 software.

RESULT

A total of 17 articles were included in this study involved in 4481 cancer patients. The pooled results showed that higher E2F1 expression was significantly correlated with unfavorable overall survival (HR = 1.10, I² = 95.3%, *P_{Heterogeneity} = 0.000) and disease-free survival (HR = 1.41, I² = 95.2%, *P_{Heterogeneity} = 0.000) of cancer patients. Such a significant association of was maintained subgroup of sample size of patients (> 150: for OS, HR = 1.77, and for DFS, HR = 0.91; or < 150: for OS, HR = 1.93, and for DFS, HR = 4.39), ethnicity (Asian: for OS, HR = 1.65, and for DFS, HR = 1.08; or not Asian: HR = 3.55, and for DFS, HR = 2.87), the data from database (clinical: for OS, HR = 1.24, and for DFS, HR = 1.40; or database: for OS, HR = 2.29, and for DFS, HR = 3.09), paper published year (after 2014: for OS, HR = 1.90;and for DFS,HR = 1.87; or before 2014: for OS, HR = 1.40, and for DFS, HR = 1.22); cancer type (female specific cancer: for OS, HR = 1.41, and for DFS, HR = 0.64; or non-gender specific cancers: for OS, HR = 2.00, and for DFS, HR = 2.95). In addition, according to the database data, we also found that higher E2F1 expression level would lead to worse prognosis of patients, and the results were consistent with the statistical analysis results in the paper.

CONCLUSION

E2F1 could be served as a prognostic biomarker in cancer patients and higher levels of in cancer patients could predict shorter overall survival and disease-free survival.

miR-125b-5p, miR-155-3p, and miR-214-5p and Target E2F2 Gene in Oral Squamous Cell Carcinoma

It is known that E2F2 (E2F transcription factor 2) plays an important role as controller in the cell cycle. This study aimed to analyse the expression of the E2F2 gene and E2F2 protein and demonstrate E2F2 target microRNAs (miRNAs) candidates (miR-125b-5p, miR-155-3p, and miR-214-5p) in oral squamous cell carcinoma tumour and margin samples. The study group consisted 50 patients. The E2F2 gene and miRNAs expression levels were assessed by qPCR, while the E2F2 protein was assessed by ELISA. When analysing the effect of miRNAs expression on E2F2 gene expression and E2F2 protein level, we observed no statistically significant correlations. miR-125b-5p was downregulated, while miR-155-3p, and miR-214-5p were upregulated in tumour samples compared to margin. We observed a difference between the miR-125b-5p expression level in smokers and non-smokers in margin samples. Furthermore, HPV-positive individuals had a significantly higher miR-125b-5p and miR-214-5p expression level compared to HPV-negative patients in tumour samples. The study result showed that the E2F2 gene is not the target for analysed miRNAs in OSCC. Moreover, miR-155-3p and miR-125b-5p could play roles in the pathogenesis of OSCC. A differential expression of the analysed miRNAs was observed in response to tobacco smoke and HPV status.

E2F2 promotes lung adenocarcinoma progression through B-Myb- and FOXM1-facilitated core transcription regulatory circuitry

Lung adenocarcinoma (LUAD) causes severe cancer death worldwide. E2F2 is a canonical transcription factor implicated in transcription regulation, cell cycle and tumorigenesis. The role of E2F2 as well as its transcription regulatory network in LUAD remains obscure. In this study, we constructed a weighted gene co-expression network and identified several key modules and networks overrepresented in LUAD, including the E2F2-centered transcription regulatory network. Function analysis revealed that E2F2 overexpression accelerated cell growth, cell cycle progression and cell motility in LUAD cells whereas E2F2 knockdown inhibited these malignant phenotypes. Mechanistic investigations uncovered various E2F2-regulated downstream genes and oncogenic signaling pathways. Notably, three core transcription factors of E2F2, B-Myb and FOXM1 from the LUAD transcription regulatory network exhibited positive expression correlation, associated with each other, mutually transactivated each other, and regulated similar downstream gene cascades, hence constituting a consolidated core transcription regulatory circuitry. Moreover, E2F2 could promote and was essentially required for LUAD growth in orthotopic mouse models. Prognosis modeling revealed that a two-gene signature of E2F2 and PLK1 from the transcription regulatory circuitry remarkably stratified patients into low- and high-risk groups. Collectively, our results clarified the critical roles of E2F2 and the exquisite core transcription regulatory circuitry of E2F2/B-Myb/FOXM1 in LUAD progression.

E2F1-induced lncRNA, EMSLR regulates lncRNA LncPRESS1

E2F1 induces hundreds of protein-coding genes influencing diverse signaling pathways but much less is known about its non-coding RNA targets. For identifying E2F1-dependent oncogenic long non-coding RNAs (lncRNAs), we carried out genome-wide transcriptome analysis and discovered an lncRNA, EMSLR, which is induced both in lung adenocarcinoma (LUAD) and lung squamous cell carcinoma (LUSC). EMSLR depletion blocks the cells in G1 phase and inhibits the clonogenic ability indicating that it is essential for the tumor-related phenotypes. We discovered that EMSLR represses the promoter activity of another lncRNA, LncPRESS1, which is located 6.9 kb upstream of EMSLR and they display an inverse expression pattern in lung cancer cell lines. Depletion of C-MYC results in downregulation of EMSLR and simultaneous upregulation of EMSLR target LncPRESS1, exemplifying how C-MYC and E2F1 signal transduction pathways control the network of lncRNA genes to modulate cell proliferation and differentiation.

Multiomics Analysis of Spatially Distinct Stromal Cells Reveals Tumor-Induced O-Glycosylation of the CDK4-pRB Axis in Fibroblasts at the Invasive Tumor Edge

The invasive leading edge represents a potential gateway for tumor metastasis. The role of fibroblasts from the tumor edge in promoting cancer invasion and metastasis has not been comprehensively elucidated. We hypothesize that cross-talk between tumor and stromal cells within the tumor microenvironment results in activation of key biological pathways depending on their position in the tumor (edge vs. core). Here we highlight phenotypic differences between tumor-adjacent-fibroblasts (TAF) from the invasive edge and tumor core fibroblasts from the tumor core, established from human lung adenocarcinomas. A multiomics approach that includes genomics, proteomics, and O-glycoproteomics was used to characterize cross-talk between TAFs and cancer cells. These analyses showed that O-glycosylation, an essential posttranslational modification resulting from sugar metabolism, alters key biological pathways including the cyclin-dependent kinase 4 (CDK4) and phosphorylated retinoblastoma protein axis in the stroma and indirectly modulates proinvasive features of cancer cells. In summary, the O-glycoproteome represents a new consideration for important biological processes involved in tumor-stroma cross-talk and a potential avenue to improve the anticancer efficacy of CDK4 inhibitors.

SIGNIFICANCE

A multiomics analysis of spatially distinct fibroblasts establishes the importance of the stromal O-glycoproteome in tumor-stroma interactions at the leading edge and provides potential strategies to improve cancer treatment. See related commentary by De Wever, p. 537.

Potential role of glucosamine-phosphate N-acetyltransferase 1 in the development of lung adenocarcinoma

Glucosamine-phosphate N-acetyltransferase 1 (GNPNAT1) is a key enzyme associated with glucose metabolism and uridine diphosphate-N-acetylglucosamine biosynthesis. Abnormal GNPNAT1 expression might be associated with carcinogenesis. We analyzed multiple lung adenocarcinoma (LUAD) gene expression databases and verified GNPNAT1 higher expression in LUAD tumor tissues than in normal tissues. Moreover, we analyzed the survival relationship between LUAD patients’ clinical status and GNPNAT1 expression, and found higher GNPNAT1 expression in LUAD patients with unfavorable prognosis. We built GNPNAT1 gene co-expression networks and further annotated the co-expressed genes’ Gene Ontology (GO) terms, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways, and various associated regulatory factors. These co-expression genes’ functional networks mainly participate in chromosome segregation, RNA metabolic process, and RNA transport. We analyzed GNPNAT1 genetic alterations and co-occurrence networks, and the functional networks of these genes showed that GNPNAT1 participates in multiple steps of cell cycle transition and in the development of some cancers. We assessed the correlation between GNPNAT1 expression and cancer immune infiltrates and showed that GNPNAT1 expression is correlated with several immune cells, chemokines, and immunomodulators in LUAD. We found that GNPNAT1 correlates with LUAD development and prognosis, laying a foundation for further research, especially in immunotherapy.

Elevated TOP2A and UBE2C expressions correlate with poor prognosis in patients with surgically resected lung adenocarcinoma: a study based on immunohistochemical analysis and bioinformatics

PURPOSE

Lung cancer has the highest morbidity and mortality among all cancer types. Reliable prognostic biomarkers are needed to identify high-risk patients apart from TNM system for precision medicine. The present study is designed to identify robust prognostic biomarkers in lung adenocarcinoma (LUAD) based on integration of multiple GEO datasets, The Cancer Genome Atlas (TCGA) database and Clinical Proteomic Tumor Analysis Consortium (CPTAC) database.

METHODS

Four LUAD GEO datasets (GSE10072, GSE2514, GSE43458, and GSE32863) and TCGA database were implemented to analyze the differently expressed genes (DEGs). Gene ontology, KEGG pathway, and protein-protein interaction network (PPI) were conducted based on the above DEGs. Hub genes were selected based on connectivity degree in the PPI network. Expression analysis and Kaplan-Meier survival analysis were conducted in CPTAC lung adenocarcinomas cohort. Kaplan-Meier survival analysis and Cox proportional hazards regression were performed on these hub genes using TCGA and our own cohort.

RESULTS

A total of 430 shared genes in all five datasets were identified as DEGs. Based on their PPI network, nine hub genes were selected and all of them were significantly associated with overall survival using GEPIA analysis. Two hub genes, TOP2A and UBE2C, were further combined and showed poorer prognosis in both TCGA dataset and our validated cohort. Analysis in CPTAC revealed that TOP2A and UBE2C were significantly highly expressed in tumor sample. Multivariable analysis suggested TOP2A and UBE2C as independent prognostic factors in LUAD.

CONCLUSION

Using data mining approach, we identified TOP2A and UBE2C as two robust prognostic factors in LUAD. We also demonstrated the TOP2A/UBE2C co-expression status in LUAD, and TOP2A/UBE2C co-expression correlated with poorer prognosis. More in-depth research is needed for transforming this result into clinical setting.

Integrated analysis of the E2F transcription factors across cancer types

E2F transcription factors are associated with the development of cancer. However, the E2F family genes have not yet been studied in a comprehensive manner. Using The Cancer Genome Atlas, the present study analyzed the functions of the E2F family genes across different types of tumor. It was revealed that compared with normal tissues, the E2F family genes are highly expressed in several types of tumor tissue. Furthermore, E2F transcription factors were significantly enriched in tumor samples across different types of tumor. The high expression levels of E2F family genes were associated with an unfavorable prognosis in liver hepatocellular carcinoma (LIHC) and lung adenocarcinoma (LUAD). Furthermore, patients with pathological T1 stage and iCluster2 molecular subtype of LIHC expressed particularly low levels of E2F family genes. The present study demonstrated that hypo-DNA methylation, DNA amplification and TP53 mutation contributed to the high expression levels of E2F family genes in cancer cells. Finally, the present study revealed that, compared with other types of tumor, the E2F family genes were specifically downregulated in patients with LIHC. The expression levels and prognostic effects of the E2F family genes were validated using the Gene Expression Omnibus database. The results of the present study revealed the biological functions of E2F family genes in the development of cancer and provided potential biomarkers for further therapeutic studies, particularly for patients with LIHC and LUAD.

NF-YA Overexpression in Lung Cancer: LUAD

The trimeric transcription factor (TF) NF-Y regulates the CCAAT box, a DNA element enriched in promoters of genes overexpressed in many types of cancer. The regulatory NF-YA is present in two major isoforms, NF-YAl ("long") and NF-YAs ("short"). There is growing indication that NF-YA levels are increased in tumors. Here, we report interrogation of RNA-Seq TCGA (The Cancer Genome Atlas)-all 576 samples-and GEO (Gene Expression Ominibus) datasets of lung adenocarcinoma (LUAD). NF-YAs is overexpressed in the three subtypes, proliferative, inflammatory, and TRU (terminal respiratory unit). CCAAT is enriched in promoters of tumor differently expressed genes (DEG) and in the proliferative/inflammatory intersection, matching with KEGG (Kyoto Encyclopedia of Genes and Genomes) terms cell-cycle and signaling. Increasing levels of NF-YAs are observed from low to high CpG island methylator phenotypes (CIMP). We identified 166 genes overexpressed in LUAD cell lines with low NF-YAs/NF-YAl ratios: applying this centroid to TCGA samples faithfully predicted tumors' isoform ratio. This signature lacks CCAAT in promoters. Finally, progression-free intervals and hazard ratios concurred with the worst prognosis of patients with either a low or high NF-YAs/NF-YAl ratio. In conclusion, global overexpression of NF-YAs is documented in LUAD and is associated with aggressive tumor behavior; however, a similar prognosis is recorded in tumors with high levels of NF-YAl and overexpressed CCAAT-less genes.

NF-YA Overexpression in Lung Cancer: LUSC

The CCAAT box is recognized by the trimeric transcription factor NF-Y, whose NF-YA subunit is present in two major splicing isoforms, NF-YAl (“long”) and NF-YAs (“short”). Little is known about the expression levels of NF-Y subunits in tumors, and nothing in lung cancer. By interrogating RNA-seq TCGA and GEO datasets, we found that, unlike NF-YB/NF-YC, NF-YAs is overexpressed in lung squamous cell carcinomas (LUSC). The ratio of the two isoforms changes from normal to cancer cells, with NF-YAs becoming predominant in the latter. NF-YA increased expression correlates with common proliferation markers. We partitioned all 501 TCGA LUSC tumors in the four molecular cohorts and verified that NF-YAs is similarly overexpressed. We analyzed global and subtype-specific RNA-seq data and found that CCAAT is the most abundant DNA matrix in promoters of genes overexpressed in all subtypes. Enriched Gene Ontology terms are cell-cycle and signaling. Survival curves indicate a worse clinical outcome for patients with increasing global amounts of NF-YA; same with hazard ratios with very high and, surprisingly, very low NF-YAs/NF-YAl ratios. We then analyzed gene expression in this latter cohort and identified a different, pro-migration signature devoid of CCAAT. We conclude that overexpression of the NF-Y regulatory subunit in LUSC has the scope of increasing CCAAT-dependent, proliferative (NF-YAs^high) or CCAAT-less, pro-migration (NF-YAl^high) genes. The data further reinstate the importance of analysis of single isoforms of TFs involved in tumor development.

The Modifying Effect of a Functional Variant at the miRNA Binding Site in E2F1 Gene on Recurrence of Oropharyngeal Cancer Patients with Definitive Radiotherapy

Human papillomavirus (HPV) activates E2F1-driven transcription via the E7-RB-E2F1 pathway. A polymorphism in the 3' UTR of E2F1 gene may disrupt a binding site for miRNA and may affect its transcription level, thus modifying the susceptibility to radiotherapy and outcomes through this pathway. We evaluated the association of a polymorphism at the 3'UTR miRNA binding site of E2F1 gene (rs3213180) with risk of recurrence of SCCOP in a cohort of 1008 patients. Log-rank test and univariate and multivariable Cox models were used to evaluate the associations. Compared with patients with E2F1-rs3213180 GG homozygous genotype, the patients with E2F1-rs3213180GC+CC variant genotypes had significantly better disease-free survival (log-rank P<.001) and decreased risk of SCCOP recurrence (HR, 0.4, 95% CI, 0.3-0.5) after multivariable adjustment. Furthermore, among patients with HPV16-positive tumors, the patients with E2F1-rs3213180 GC+CC variant genotypes had significantly better disease-free survival rates (log-rank P<.001) and lower recurrence risk than those with E2F1-rs3213180 GG homozygous genotype (HR, 0.2, 95% CI, 0.1-0.4). Our findings suggest that E2F1-rs3213180 polymorphism may modulate the risk of recurrence in SCCOP patients, particularly for patients with HPV16-positive tumors of SCCOP. However, future larger population and functional studies are warranted to validate these results.

The clinical value of miR-193a-3p in non-small cell lung cancer and its potential molecular mechanism explored in silico using RNA-sequencing and microarray data

miR‐193a‐3p is a tumor‐related miRNA playing an essential role in tumorigenesis and progression of non‐small cell lung cancer (NSCLC). The objective of the present study was to investigate the relationship between miR‐193a‐3p expression and clinical value and to further explore the potential signaling of miR‐193a‐3p in the carcinogenesis of NSCLC. RNA‐sequencing and microarray data were collected from the databases GEO, ArrayExpress and The Cancer Genome Atlas (TCGA). Furthermore, in silico assessments were performed to analyze the prospective pathways and networks of the target genes of miR‐193a‐3p. In total, 453 cases of NSCLC patients and 476 normal controls were included in blood samples, while 920 cases of NSCLC patients and 406 normal controls were included in tissue samples. The pooled positive likelihood ratio, the pooled negative likelihood ratio and the pooled diagnostic odds ratio were calculated to reflect the diagnostic value of miR‐193a‐3p in blood and tissue samples. Moreover, the areas under the curve of the summary receiver operating characteristic curve of blood and tissue were 0.64 and 0.79, respectively. In addition, we found a lower level of miR‐193a in NSCLC tissues than in non‐cancerous controls based on TCGA. A gene ontology (GO) enrichment analysis demonstrated that miR‐193a‐3p could be related to key signaling pathways in NSCLC. Also, several vital pathways were illustrated by KEGG. Lower expression of miR‐193a‐3p in tissue samples of NSCLC may be associated with tumorigenesis and be a predictor of deterioration of NSCLC patients, and pathway analysis revealed crucial signaling pathways correlated with the incidence and progress of NSCLC.

Loss of RUNX1 is associated with aggressive lung adenocarcinomas

The mammalian runt-related factor 1 (RUNX1) is a master transcription factor that regulates lineage specification of hematopoietic stem cells. RUNX1 translocations result in the development of myeloid leukemias. Recently, RUNX1 has been implicated as a tumor suppressor in other cancers. We postulated RUNX1 expression may be associated with lung adenocarcinoma etiology and/or progression. We evaluated the association of RUNX1 mRNA expression with overall survival data from The Cancer Genome Atlas (TCGA), a publically available database. Compared to high expression levels, Low RUNX1 levels from lung adenocarcinomas were associated with a worse overall survival (Hazard Ratio = 2.014 (1.042-3.730 95% confidence interval), log-rank p = 0.035) compared to those that expressed high RUNX1 levels. Further immunohistochemical examination of 85 surgical specimens resected at the University of Vermont Medical Center identified that low RUNX1 protein expression was associated with larger tumors (p = 0.038). Gene expression network analysis was performed on the same subset of TCGA cases that demonstrated differential survival by RUNX1 expression. This analysis, which reveals regulatory relationships, showed that reduced RUNX1 levels were closely linked to upregulation of the transcription factor E2F1. To interrogate this relationship, RUNX1 was depleted in a lung cancer cell line that expresses high levels of RUNX1. Loss of RUNX1 resulted in enhanced proliferation, migration, and invasion. RUNX1 depletion also resulted in increased mRNA expression of E2F1 and multiple E2F1 target genes. Our data implicate loss of RUNX1 as driver of lung adenocarcinoma aggression, potentially through deregulation of the E2F1 pathway.

Prognostic roles of mRNA expression of notch receptors in non-small cell lung cancer

Notch signalling is aberrantly activated in human non-small cell lung cancer (NSCLC). Nevertheless, the prognostic roles of mRNA expression of four Notch receptors in NSCLC patients remain elusive. In this report, we reported the prognostic roles of Notch receptors in a total of 1,926 NSCLC patients through “The Kaplan-Meier plotter” (KM plotter) database which is capable to assess the effect of 22,277 genes on survival of NSCLC patients. We found that mRNA high expression level of Notch1 was associated with better overall survival (OS) for all NSCLC patients, hazard ratio (HR) 0.78 (0.69-0.89), p=0.00019, better OS in adenocarcinoma (Ade) patients, HR 0.59 (0.46-0.75), p=1.5e-05, as well as in squamous cell carcinoma (SCC) patients, HR 0.78 (0.62-0.99), p=0.044. mRNA high expression levels of Notch2 and Notch3 were associated with worsen OS for all NSCLC patients, as well as in Ade, but not in SCC patients. mRNA high expression level of Notch4 was not found to be associated with to OS for all NSCLC patients. In addition, mRNA high expression levels of Notch2, Notch3, but Notch4 are significantly associated with the NSCLC patients who have different smoking status. Our results indicate that mRNA expression of Notch receptors may have distinct prognostic values in NSCLC patients. These results will benefit for developing tools to accurately predict the prognosis of NSCLC patients.