Multiple roles of single-minded 2 in esophageal squamous cell carcinoma and its clinical implications

SIM2: Its Prognostic Significance and Oncogenic Role in Endometrial Carcinoma

Background

Endometrial carcinoma ranks as the second most widespread malignancy affecting the reproductive system in females. Effective prognostic biomarkers are required to further improve survival rates for patients. Single-minded homolog 2 (SIM2) is known to participate in neurogenesis as a transcription factor. However, the potential role of SIM2 in endometrial carcinoma remains elusive.

Methods

Multiple public databases, including TIMER2.0, GEIPA2, UALCAN, LinkedOmics, BioGRID, DAVID and cBioPortal, were used to investigate SIM2 mRNA expression, SIM2-associated genes, PPI network, functional enrichment analysis, SIM2 gene alterations and methylation. The association between SIM2 expression and immune cell infiltrates was explored using GSVA. The effects of gene alterations and methylation on patient survival and CD8+T infiltration were examined using GSCA. Moreover, the prognostic potential of SIM2 was evaluated using COX regression, ROC curves and a nomogram model. Finally, the differential expression and function of SIM2 in UCEC were explored using qPCR, WB, CCK8 and Transwell assays.

Results

Our findings revealed the heightened expression of SIM2 in endometrial carcinoma, and that its DNA methylation and CNV alterations were correlated with immune infiltration and patients' prognosis. Additionally, functional enrichment revealed the involvement of SIM2 in transcription regulation and signal transduction. Moreover, we performed cell-based experiments to corroborate the oncogenic function of SIM2 in facilitating cell proliferation, migration and invasion.

Conclusion

Collectively, these results suggest that SIM2 holds promise as both a potential prognostic indicator and a viable treatment target for endometrial carcinoma.

Lymph node metastasis-related lncRNA GAS6-AS1 facilitates the progression of esophageal squamous cell carcinoma

Background

Lymph node metastasis is the main type of metastasis in esophageal squamous cell carcinoma (ESCC), especially when the primary tumor invasion depth reaches above the adventitia layer (T3 stage), the incidence of lymph node metastasis increases sharply. Abnormal expression of long non-coding RNAs (lncRNAs) has been confirmed in ESCC, but there are still many unknown connections between lncRNAs and lymph node metastasis.

Methods

We used transcriptome sequencing (RNA-seq) to analyze 10 pairs of ESCC tissues with primary tumor stage T3 and their paired normal epithelium. Quantitative real-time polymerase chain reaction (qRT-PCR) was used to further verify the sequencing results, and survival curve analysis, logistic regression analysis, and receiver operating characteristic (ROC) curve analysis were used to investigate its clinical application value. We investigated the growth and metastasis effects of lncRNA GAS6-AS1 on ESCC cell lines TE-1 and KYSE410 in vitro and in vivo. Other functional experiments included cell apoptosis and cell cycle experiments.

Results

Based on our RNA-seq data, lncRNA GAS6-AS1 is highly expressed in ESCC tissues, especially in cancer tissues with lymph node metastasis. The qRT-PCR experiment analysis showed that high expression of GAS6-AS1 was related to poor tumor differentiation and tumor stage. Logistic regression analysis showed that it was an independent risk factor for lymph node metastasis, and ROC analysis validated that it could predict lymph node metastasis. Further survival analysis suggested that high expression of GAS6-AS1 was associated with patients' poor prognosis. In vitro experiments, knocking down GAS6-AS1 inhibited the growth and metastasis of ESCC cells and inhibited tumor growth in vivo. In addition, knocking down GAS6-AS1 can inhibit cell cycle and promote cell apoptosis.

Conclusions

Our results revealed that lncRNA GAS6-AS1 obtained from RNA-seq can be used as an independent risk factor for ESCC lymph node metastasis and an effective biomarker to predict, and that it was related to the growth and metastasis of ESCC. It may represent a new biomarker to aid in the assessment of the lymph node metastasis of ESCC.

Genome-Wide DNA Methylation Profiling of Esophageal Squamous Cell Carcinoma from Global High-Incidence Regions Identifies Crucial Genes and Potential Cancer Markers

Epigenetic mechanisms such as aberrant DNA methylation (DNAme) are known to drive esophageal squamous cell carcinoma (ESCC), yet they remain poorly understood. Here, we studied tumor-specific DNAme in ESCC cases from nine high-incidence countries of Africa, Asia, and South America. Infinium MethylationEPIC array was performed on 108 tumors and 51 normal tissues adjacent to the tumors (NAT) in the discovery phase, and targeted pyrosequencing was performed on 132 tumors and 36 NAT in the replication phase. Top genes for replication were prioritized by weighting methylation results using RNA-sequencing data from The Cancer Genome Atlas and GTEx and validated by qPCR. Methylome analysis comparing tumor and NAT identified 6,796 differentially methylated positions (DMP) and 866 differential methylated regions (DMR), with a 30% methylation (Δβ) difference. The majority of identified DMPs and DMRs were hypermethylated in tumors, particularly in promoters and gene-body regions of genes involved in transcription activation. The top three prioritized genes for replication, PAX9, SIM2, and THSD4, had similar methylation differences in the discovery and replication sets. These genes were exclusively expressed in normal esophageal tissues in GTEx and downregulated in tumors. The specificity and sensitivity of these DNAme events in discriminating tumors from NAT were assessed. Our study identified novel, robust, and crucial tumor-specific DNAme events in ESCC tumors across several high-incidence populations of the world. Methylome changes identified in this study may serve as potential targets for biomarker discovery and warrant further functional characterization. SIGNIFICANCE: This largest genome-wide DNA methylation study on ESCC from high-incidence populations of the world identifies functionally relevant and robust DNAme events that could serve as potential tumor-specific markers. GRAPHICAL ABSTRACT: http://cancerres.aacrjournals.org/content/canres/81/10/2612/F1.large.jpg.

Genomic Landscape of Primary and Recurrent Anal Squamous Cell Carcinomas in Relation to HPV Integration, Copy-Number Variation, and DNA Damage Response Genes

The incidence of anal squamous cell carcinoma (ASCC) has been increasing, particularly in populations with HIV. Human papillomavirus (HPV) is the causal factor in 85% to 90% of ASCCs, but few studies evaluated HPV genotypes and integrations in relation to genomic alterations in ASCC. Using whole-exome sequence data for primary (n = 56) and recurrent (n = 31) ASCC from 72 patients, we detected HPV DNA in 87.5% of ASCC, of which HPV-16, HPV-18, and HPV-6 were detected in 56%, 22%, and 33% of HIV-positive (n = 9) compared with 83%, 3.2%, and 1.6% of HIV-negative cases (n = 63), respectively. Recurrent copy-number variations (CNV) involving genes with documented roles in cancer included amplification of PI3KCA and deletion of APC in primary and recurrent tumors; amplifications of CCND1, MYC, and NOTCH1 and deletions of BRCA2 and RB1 in primary tumors; and deletions of ATR, FANCD2, and FHIT in recurrent tumors. DNA damage response genes were enriched among recurrently deleted genes in recurrent ASCCs (P = 0.001). HPV integrations were detected in 29 of 76 (38%) ASCCs and were more frequent in stage III-IV versus stage I-II tumors. HPV integrations were detected near MYC and CCND1 amplifications and recurrent targets included NFI and MUC genes. These results suggest HPV genotypes in ASCC differ by HIV status, HPV integration is associated with ASCC progression, and DNA damage response genes are commonly disrupted in recurrent ASCCs. IMPLICATIONS: These data provide the largest whole-exome sequencing study of the ASCC genomic landscape to date and identify HPV genotypes, integrations, and recurrent CNVs in primary or recurrent ASCCs.

Downregulation of long non-coding RNA LOC101928477 correlates with tumor progression by regulating the epithelial-mesenchymal transition in esophageal squamous cell carcinoma

Background

Esophageal squamous cell carcinoma (ESCC) is one of the deadliest malignancies. There is a growing body of evidence showing that long non‐coding RNAs (lncRNAs) play critical roles in ESCC oncogenesis. The present study aimed to explore the role of LOC101928477, a newly discovered lncRNA, in the development and metastasis of ESCC.

Methods

In this study, real‐time PCR, western blotting, cell counting kit‐8 (CCK‐8), flow cytometry, colony formation, wound healing, transwell migration/invasion assay, immunofluorescence, and immunohistochemistry were used. We also applied an in situ xenograft mouse model and a lung metastasis mouse model to verify our findings.

Results

We determined that LOC101928477 expression was inhibited in ESCC tissue and ESCC cell lines when compared with controls. Moreover, forced expression of LOC101928477 effectively inhibited ESCC cell proliferation, colony formation, migration, and invasion via suppression of epithelial‐mesenchymal transition (EMT). Furthermore, LOC101928477 overexpression inhibited in situ tumor growth and lung metastasis in a mouse model.

Conclusions

Together, our results suggested that LOC101928477 could be a novel suppressor gene involved in ESCC progression.

Long non‑coding RNA CASC15 facilitates esophageal squamous cell carcinoma tumorigenesis via decreasing SIM2 stability via FTO‑mediated demethylation

Long non-coding RNAs (lncRNAs) are involved in the regulation of esophageal squamous cell carcinoma (ESCC) progression. However, the function and mechanism of lncRNA cancer susceptibility candidate 15 (CASC15) are poorly defined. In the present study, tumor and normal adjacent tissues were collected from 45 patients with ESCC. Expression levels of CASC15, fat mass and obesity-associated (FTO) protein and single-minded 2 (SIM2) were examined via reverse transcription-quantitative PCR and western blot assays. Cell proliferation and apoptosis were evaluated via MTT, flow cytometry and caspase-3 activity assays, respectively. Additionally, an ESCC mouse xenograft model was used to assess the function of CASC15 in vivo. The interaction between FTO and CASC15/SIM2 was analyzed via RNA immunoprecipitation and RNA pull-down assays. The results revealed that CASC15 expression was elevated in ESCC tissues, and patients with ESCC exhibiting high CASC15 expression had a poor prognosis. CASC15-knockdown inhibited ESCC cell proliferation and facilitated apoptosis. Additionally, CASC15-knockdown decreased the growth of ESCC xenograft tumors. CASC15 decreased SIM2 stability via FTO-mediated demethylation. Additionally, FTO loss markedly weakened CASC15-mediated pro-proliferative and anti-apoptotic effects in ESCC cells. SIM2 downregulation weakened the effect of CASC15-knockdown on cell proliferation and inhibited the increase of the apoptotic rate and caspase-3 activity induced by CASC15 depletion in ESCC cells. In conclusion, CASC15 promoted ESCC tumorigenesis by decreasing SIM2 stability via FTO-mediated demethylation.

Development and Validation of the Predictive Model for Esophageal Squamous Cell Carcinoma Differentiation Degree

The diagnosis of the degree of differentiation of tumor cells can help physicians to make timely detection and take appropriate treatment for the patient's condition. In this study, the original dataset is clustered into two independent types by the Kohonen clustering algorithm. One type is used as the development sets to find correlation indicators and establish predictive models of differentiation, while the other type is used as the validation sets to test the correlation indicators and models. In the development sets, thirteen indicators significantly associated with the degree of differentiation of esophageal squamous cell carcinoma are found by the Kohonen clustering algorithm. Thirteen relevant indicators are used as input features and the degree of tumor differentiations is used as output. Ten classification algorithms are used to predict the differentiation of esophageal squamous cell carcinoma. Artificial bee colony-support vector machine (ABC-SVM) predicts better than the other nine algorithms, with an average accuracy of 81.5% for the 10-fold cross-validation. Based on logistic regression and ReliefF algorithm, five models with the greater merit for the degree of differentiation are found in the development sets. The AUC values of the five models are 0.672, 0.628, 0.630, 0.628, and 0.608 (P < 0.05). The AUC values of the five models in the validation sets are 0.753, 0.728, 0.744, 0.776, and 0.868 (P < 0.0001). The predicted values of the five models are constructed as the input features of ABC-SVM. The accuracy of the 10-fold cross-validation reached 82.0 and 86.5% in the development sets and the validation sets, respectively.

Aberrant DNA Methylation in Esophageal Squamous Cell Carcinoma: Biological and Clinical Implications

Almost all cancer cells possess multiple epigenetic abnormalities, which cooperate with genetic alterations to enable the acquisition of cancer hallmarks during tumorigenesis. As the most frequently found epigenetic change in human cancers, aberrant DNA methylation manifests at two major forms: global genomic DNA hypomethylation and locus-specific promoter region hypermethylation. It has been recognized as a critical contributor to esophageal squamous cell carcinoma (ESCC) malignant transformation. In ESCC, DNA methylation alterations affect genes involved in cell cycle regulation, DNA damage repair, and cancer-related signaling pathways. Aberrant DNA methylation patterns occur not only in ESCC tumors but also in precursor lesions. It adds another layer of complexity to the ESCC heterogeneity and may serve as early diagnostic, prognostic, and chemo-sensitive markers. Characterization of the DNA methylome in ESCC could help better understand its pathogenesis and develop improved therapies. We herein summarize the current research and knowledge about DNA methylation in ESCC and its clinical significance in diagnosis, prognosis, and treatment.

IFI6 depletion inhibits esophageal squamous cell carcinoma progression through reactive oxygen species accumulation via mitochondrial dysfunction and endoplasmic reticulum stress

BACKGROUND

Esophageal squamous cell carcinoma (ESCC) is one of the most lethal forms of adult cancer with poor prognosis. Substantial evidence indicates that reactive oxygen species (ROS) are important modulators of aggressive cancer behavior. However, the mechanism by which ESCC cells integrate redox signals to modulate carcinoma progression remains elusive.

METHODS

The expression of interferon alpha inducible protein 6 (IFI6) in clinical ESCC tissues and cell lines was detected by RT-PCR and Western blotting. The correlation between IFI6 expression levels and aggressive ESCC disease stage was examined by immunohistochemistry. Bioinformatic analysis was conducted to explore the potential function of IFI6 in ESCC. ESCC cell lines stably depleted of IFI6 and ectopically expressing IFI6 were established using lentiviruses expressing shRNAs and an IFI6 expression plasmid, respectively. The effects of IFI6 on ESCC cells were determined by cell-based analyses, including EdU assay, apoptotic assay, cellular and mitochondria-specific ROS detection, seahorse extracellular flux, and mitochondrial calcium flux assays. Blue native-polyacrylamide gel electrophoresis was used to determine mitochondrial supercomplex assembly. Transcriptional activation of NADPH oxidase 4 (NOX4) via ATF3 was confirmed by dual luciferase assay. In vivo tumor growth was determined in mouse xenograft models.

RESULTS

We find that the expression of IFI6, an IFN-stimulated gene localized in the inner mitochondrial membrane, is markedly elevated in ESCC patients and a panel of ESCC cell lines. High IFI6 expression correlates with aggressive disease phenotype and poor prognosis in ESCC patients. IFI6 depletion suppresses proliferation and induces apoptosis by increasing ROS accumulation. Mechanistically, IFI6 ablation induces mitochondrial calcium overload by activating mitochondrial Ca2+ uniporter and subsequently ROS production. Following IFI6 ablation, mitochondrial ROS accumulation is also induced by mitochondrial supercomplex assembly suppression and oxidative phosphorylation dysfunction, while IFI6 overexpression produces the opposite effects. Furthermore, energy starvation induced by IFI6 inhibition drives endoplasmic reticulum stress through disrupting endoplasmic reticulum calcium uptake, which upregulates NOX4-derived ROS production in an ATF3-dependent manner. Finally, the results in xenograft models of ESCC further corroborate the in vitro findings.

CONCLUSION

Our study unveils a novel redox homeostasis signaling pathway that regulates ESCC pathobiology and identifies IFI6 as a potential druggable target in ESCC.

CD24 and CK4 are upregulated by SIM2, and are predictive biomarkers for chemoradiotherapy and surgery in esophageal cancer

Definitive chemoradiotherapy (CRT) is a less invasive therapy compared with surgery for some types of cancer; however, the 5‑year survival rate of patients with stages II‑III esophageal squamous cell carcinoma (ESCC) is only 37%. Therefore, prediction of CRT responders is necessary. Unfortunately, no definitive biomarker exists that is useful to predict survival outcome following CRT. From our previous microarray study, CD24 and keratin 4 (KRT4), which encodes cytokeratin 4 (CK4), were overexpressed in the favorable prognostic epithelial subtype with SIM bHLH transcription factor 2 (SIM2) expression. This study investigated the association between their mRNA and protein expression levels, and clinicopathological characteristics, and also investigated the functions of CD24 in SIM2‑mediated tumor differentiation and CRT sensitivity. High CD24 and KRT4 mRNA expression was associated with a favorable prognosis following CRT. Multivariate analyses revealed that high CD24 and CK4 protein expression, as determined by immunohistochemistry, and differentiated type were independent factors for predicting a favorable prognosis in response to CRT. Notably, in cases with low CD24 or CK4, surgery was suggested to be a good therapeutic modality compared with CRT. CD24 and KRT4 were expressed preferentially in differentiated layers of the normal esophageal mucosa, and their mRNA expression in 3D cultured ESCC cells was induced by SIM2 transfection, thus suggesting that CD24 and KRT4 were downstream differentiation markers of SIM2. Furthermore, CD24 small interfering RNA increased the mRNA expression levels of superoxide dismutase 2 and enhanced H2O2 resistance, thus indicating the involvement of CD24 in the radiosensitivity of patients with ESCC; however, it had no effect on cisplatin sensitivity. In conclusion, the two markers CD24 and CK4 may be considered predictive biomarkers for definitive CRT.

Positive Programmed Cell Death-Ligand 1 Expression Predicts Poor Treatment Outcomes in Esophageal Squamous Cell Carcinoma Patients Receiving Neoadjuvant Chemoradiotherapy

Background: Programmed cell death-ligand 1 (PD-L1) is present in a subgroup of cancer patients who may be favorable targets for immune checkpoint inhibitor therapies. However, the significance of the PD-L1 expression in esophageal squamous cell carcinoma (ESCC) patients receiving neoadjuvant chemoradiotherapy remains unclear. Methods: By means of PD-L1 immunohistochemistry 22C3 pharmDx assay, we evaluate the PD-L1 expression and its association with clinical outcome in 107 ESCC patients receiving neoadjuvant chemoradiotherapy. Results: Patients with positive PD-L1 expression have significantly lower pathological complete response rates (13% versus 32%; p = 0.036) than those with negative PD-L1 expression. Univariate survival analysis found that positive PD-L1 expression were correlated with poor overall survival (p = 0.004) and inferior disease-free survival (p < 0.001). In a multivariate analysis, positive PD-L1 expression was independently associated with the absence of a pathologically complete response (p = 0.044, hazard ratio: 3.542), worse overall survival (p = 0.006, hazard ratio: 2.017), and inferior disease-free survival (p < 0.001, hazard ratio: 2.516). Conclusions: For patients with ESCC receiving neoadjuvant chemoradiotherapy, positive PD-L1 expression independently predicts the poor chemoradiotherapy response and worse treatment outcome. Thus, our data suggests that PD-L1 may be an influential biomarker for prognostic classification and for immune checkpoint inhibitor therapies in ESCC patients receiving neoadjuvant chemoradiotherapy.

FGF5 methylation is a sensitivity marker of esophageal squamous cell carcinoma to definitive chemoradiotherapy

Definitive chemoradiotherapy (dCRT) is the major treatment for esophageal squamous cell carcinoma (ESCC), and prediction of the response to dCRT is important so as not to miss an opportunity to cure an ESCC. Nevertheless, few validated markers are available. Here, we aimed to identify a highly reproducible marker using multi-layer omics analysis. 117 ESCC samples from 67 responders and 50 non-responders were divided into screening, validation, and re-validation sets. In the screening cohort (n = 41), somatic mutations in 114 genes showed no association with dCRT response. Genome-wide DNA methylation analysis using Infinium HumanMethylation450 BeadChip array identified four genic regions significantly associated with dCRT response. Among them, FGF5 methylation was validated to be associated with dCRT response (n = 34; P = 0.001), and further re-validated (n = 42; P = 0.020) by bisulfite-pyrosequencing. The sensitivity and specificity in the combined validation and re-validation sets (n = 76) were 45% and 90%, respectively, by using the cut-off value established in the screening set, and FGF5 methylation had predictive power independent from clinicopathological parameters. In ESCC cell lines, FGF5 promoter methylation repressed its expression. FGF5 expression was induced by cisplatin (CDDP) treatment in three unmethylated cell lines, but not in two methylated cell lines. Exogenous FGF5 overexpression in a cell line with its methylation conferred resistance to CDDP. In non-cancerous esophageal tissues, FGF5 was not expressed, and its methylation was present in a small fraction of cells. These results showed that FGF5 methylation is a validated marker for ESCC sensitivity to dCRT.

ILK predicts the efficacy of chemoradiotherapy and the prognosis of patients with esophageal squamous cell carcinoma

Isobaric tags for relative and absolute quantitation (iTRAQ) technology was adopted to screen differentially-expressed proteins in the serum that predict the effects of chemoradiotherapy on esophageal squamous cell carcinoma (ESCC). Thus, significantly related proteins can be functionally identified at the cellular level. A total of 60 patients diagnosed with locally advanced and advanced ESCC were recruited and treated with chemoradiotherapy. The iTRAQ technique was used to screen serum differentially expressed proteins associated with chemoradiotherapeutic efficacy. Functional identification of significantly related proteins was performed at the cellular level. Cell proliferation was detected using MTT, clonogenic and fluorescence assays, and apoptosis was assessed using flow cytometry. Transwell and wound-healing assays were used to detect the invasion and migration properties of cancer cells. Proteomics results revealed that prior to chemoradiotherapy, the expression level of integrin-linked kinase (ILK) was significantly upregulated in patients with ESCC, compared with that of the control group [ratio (r)=4.386; P<0.05], and significantly downregulated in the chemoradiotherapy-sensitive group, compared with the chemoradiotherapy-resistant group (r=0.587; P<0.05). At the cellular level, the proliferation rate of cells in the experimental group was significantly inhibited (P<0.05), and the number of cell colonies was decreased (P<0.01), while the number of apoptotic cells was significantly increased (P<0.01). The invasive ability of TE-1 cells in the shILK group was significantly inhibited (P<0.01), and the migration rate was significantly retarded at 8 and 24 h (P<0.01). The present study highlighted the potential value of ILK in predicting the efficacy of chemoradiotherapeutic treatment in patients with ESCC, and that ILK gene-silencing inhibits the progression of ESCC.

Biological Significance of Tumor Heterogeneity in Esophageal Squamous Cell Carcinoma

Esophageal squamous cell carcinoma (ESCC) is a common and aggressive malignancy, with hitherto dismal clinical outcome. Genomic analyses of patient samples reveal a complex heterogeneous landscape for ESCC, which presents in both intertumor and intratumor forms, manifests at both genomic and epigenomic levels, and contributes significantly to tumor evolution, drug resistance, and metastasis. Here, we review the important molecular characteristics underlying ESCC heterogeneity, with an emphasis on genomic aberrations and their functional contribution to cancer evolutionary trajectories. We further discuss how novel experimental tools, including single-cell sequencing and three-dimensional organoids, may advance our understanding of tumor heterogeneity. Lastly, we suggest that deciphering the mechanisms governing tumor heterogeneity holds the potential to developing precision therapeutics for ESCC patients.

Multiple roles of single-minded 2 in esophageal squamous cell carcinoma and its clinical implications

Degree of histological differentiation is an important characteristic of cancers and may be associated with malignant potential. However, in squamous cell carcinomas, a key transcriptional factor regulating tumor differentiation is largely unknown. Chemoradiotherapy (CRT) is a standard treatment for locally advanced esophageal squamous cell carcinoma; however, the survival rate is still below 40%. From microarray data, single‐minded 2 (SIM2) was overexpressed in the epithelial subtype. Here, we investigated the correlation between SIM2 expression and its clinical implication, and in vitro and in vivo functions of SIM2 in tumor differentiation and in CRT sensitivity. Although SIM2 was suppressed in cancerous tissues, SIM2‐high ESCC showed a favorable prognosis in CRT. Transient SIM2 expression followed by 3D culture induced expression of differentiation markers and suppressed epithelial‐mesenchymal transition‐ and basal‐cell markers. Levels of PDPN‐high tumor basal cells and of expression of genes for DNA repair and antioxidant enzymes were reduced in stable transfectants, and they showed high CDDP and H₂O₂ sensitivities, and their xenografts showed a well‐differentiated histology. Reduction of tumor basal cells was restored by knockdown of aryl hydrocarbon receptor nuclear translocator (ARNT) that interacted with SIM2. Together, SIM2 increases CRT sensitivity through tumor differentiation by cooperation with ARNT.