SIX1 maintains tumor basal cells via transforming growth factor-β pathway and associates with poor prognosis in esophageal cancer

Targeting sine oculis homeoprotein 1 (SIX1): A review of oncogenic roles and potential natural product therapeutics

Sine oculis homeoprotein 1 (SIX1), a prominent representative of the homeodomain transcription factors within the SIX family, has attracted significant interest owing to its role in tumorigenesis, cancer progression, and prognostic assessments. Initially recognized for its pivotal role in embryonic development, SIX1 has emerged as a resurgent factor across a diverse set of mammalian cancers. Over the past two decades, numerous investigations have emphasized SIX1's dual significance as a developmental regulator and central player in oncogenic processes. A mounting body of evidence links SIX1 to the initiation of diverse cancers, encompassing enhanced cellular metabolism and advancement. This review provides an overview of the multifaceted roles of SIX1 in both normal development and oncogenic processes, emphasizing its importance as a possible therapeutic target and prognostic marker. Additionally, this review discusses the natural product agents that inhibit various pro-oncogenic mechanisms associated with SIX1.

All eyes on Eya: A unique transcriptional co-activator and phosphatase in cancer

The Eya family of proteins (consisting of Eyas1-4 in mammals) play vital roles in embryogenesis by regulating processes such as proliferation, migration/invasion, cellular survival and pluripotency/plasticity of epithelial and mesenchymal states. Eya proteins carry out such diverse functions through a unique combination of transcriptional co-factor, Tyr phosphatase, and PP2A/B55α-mediated Ser/Thr phosphatase activities. Since their initial discovery, re-expression of Eyas has been observed in numerous tumor types, where they are known to promote tumor progression through a combination of their transcriptional and enzymatic activities. Eya proteins thus reinstate developmental processes during malignancy and represent a compelling class of therapeutic targets for inhibiting tumor progression.

SIX1 amplification modulates stemness and tumorigenesis in breast cancer

BACKGROUND

Sine oculis homeobox homolog 1 (SIX1) is a transcription factor that has recently been identified as a crucial regulator of embryonic development and tumorigenesis. SIX1 is upregulated in different types of tumors, including breast cancer. However, the role and mechanism of SIX1 upregulation in breast cancer carcinogenesis remains uncertain.

METHODS

In this study, we utilized various databases such as UALCAN, TCGA, STRING, and Kaplan-Meier Plotter to investigate the mRNA expression, prognosis, transcriptional profile changes, signal pathway rewiring, and interaction with cancer stem cells of SIX1 in breast cancer. We also conducted both in vitro and in vivo experiments to validate its positive regulation effect on breast cancer stem cells.

RESULTS

Our findings demonstrated that the expression of SIX1 varies among different subtypes of breast cancer and that it upregulates breast cancer grading and lymph node metastasis. Besides, SIX1 participates in the rewiring of several cancer signaling pathways, including estrogen, WNT, MAPK, and other pathways, and interacts with cancer stem cells. SIX1 showed a significant positive correlation with breast cancer stem cell markers such as ALDH1A1, EPCAM, ITGB1, and SOX2. Moreover, our in vitro and in vivo experiments confirmed that SIX1 can promote the increase in the proportion of stem cells and tumor progression.

CONCLUSIONS

Altogether, our results suggest that SIX1 plays an essential regulatory role in breast cancer's occurrence, and its amplification can be utilized as a diagnostic and prognostic predictor. The interaction between SIX1 and cancer stem cells may play a critical role in regulating breast cancer's initiation and metastasis.

Retinal determination gene networks: from biological functions to therapeutic strategies

The retinal determinant gene network (RDGN), originally discovered as a critical determinator in Drosophila eye specification, has become an important regulatory network in tumorigenesis and progression, as well as organogenesis. This network is not only associated with malignant biological behaviors of tumors, such as proliferation, and invasion, but also regulates the development of multiple mammalian organs. Three members of this conservative network have been extensively investigated, including DACH, SIX, and EYA. Dysregulated RDGN signaling is associated with the initiation and progression of tumors. In recent years, it has been found that the members of this network can be used as prognostic markers for cancer patients. Moreover, they are considered to be potential therapeutic targets for cancer. Here, we summarize the research progress of RDGN members from biological functions to signaling transduction, especially emphasizing their effects on tumors. Additionally, we discuss the roles of RDGN members in the development of organs and tissue as well as their correlations with the pathogenesis of chronic kidney disease and coronary heart disease. By summarizing the roles of RDGN members in human diseases, we hope to promote future investigations into RDGN and provide potential therapeutic strategies for patients.

Role of Cell-Cell Junctions in Oesophageal Squamous Cell Carcinoma

Cell-cell junctions comprise various structures, including adherens junctions, tight junctions, desmosomes, and gap junctions. They link cells to each other in tissues and regulate tissue homeostasis in critical cellular processes. Recent advances in cell-cell junction research have led to critical discoveries. Cell-cell adhesion components are important for the invasion and metastasis of tumour cells, which are not only related to cell-cell adhesion changes, but they are also involved in critical molecular signal pathways. They are of great significance, especially given that relevant molecular mechanisms are being discovered, there are an increasing number of emerging biomarkers, targeted therapies are becoming a future therapeutic concern, and there is an increased number of therapeutic agents undergoing clinical trials. Oesophageal squamous cell carcinoma (ESCC), the most common histological subtype of oesophageal cancer, is one of the most common cancers to affect epithelial tissue. ESCC progression is accompanied by the abnormal expression or localisation of components at cell-cell junctions. This review will discuss the recent scientific developments related to the molecules at cell-cell junctions and their role in ESCC to offer valuable insights for readers, provide a global view of the relationships between position, construction, and function, and give a reference for future mechanistic studies, diagnoses, and therapeutic developments.

Silencing of histone deacetylase 3 suppresses the development of esophageal squamous cell carcinoma through regulation of miR-494-mediated TGIF1

BACKGROUND

Deacetylation of histones by histone deacetylase 3 (HDAC3) acts importantly in modulating apoptosis, DNA damage and cellular progression. Herein, we aimed to unravel the functional role of HDAC3 in a lethal disease, esophageal squamous cell carcinoma (ESCC).

METHODS

The expression of HDAC3 in clinically collected ESCC tissues was determined by RT-qPCR and immunohistochemistry. As revealed from bioinformatics analysis, the putative relations between HDAC3 and microRNA-494 (miR-494) and between miR-494 and transforming growth factor beta (TGFβ)-inducing factor 1 (TGIF1) were further verified by chromatin immunoprecipitation and dual-luciferase reporter gene assay. Functional roles of shRNA-mediated depletion of HDAC3, miR-494 mimic and overexpressed TGIF1 were explored by gain- and loss-of-function assays with regard to ESCC cell biological behaviors. A nude mouse model of ESCC was developed for in vivo validation.

RESULTS

HDAC3 was highly expressed in ESCC tissues, suggestive of poor prognosis while TGIF1 was upregulated and miR-494 was downregulated. Mechanistic investigation revealed that HDAC3 inhibited miR-494 expression and TGIF1 was a direct target of miR-494. Furthermore, silencing HDAC3 or overexpressing miR-494 was demonstrated to suppress aggressive phenotypes of ESCC cells both in vitro through the activated TGFβ signaling pathway and in vivo, while TGIF1 overexpression induced opposite results.

CONCLUSION

Collectively, our findings provided demonstration regarding the oncogenic property of HDAC3 in ESCC via the miR-494/TGIF1/TGFβ axis.

Ginsenoside Rh4 Suppresses Metastasis of Gastric Cancer via SIX1-Dependent TGF-β/Smad2/3 Signaling Pathway

Gastric cancer (GC) is the leading causes of cancer-related death worldwide. Surgery remains the cornerstone of gastric cancer treatment, and new strategies with adjuvant chemotherapy are currently gaining more and more acceptance. Ginsenoside Rh4 has excellent antitumor activity. Conversely, the mechanisms involved in treatment of GC are not completely understood. In this study, we certified that Rh4 showed strong anti-GC efficiency in vitro and in vivo. MTT and colony formation assays were performed to exhibit that Rh4 significantly inhibited cellular proliferation and colony formation. Results from the wound healing assay, transwell assays, and Western blotting indicated that Rh4 restrained GC cell migration and invasion by reversing epithelial–mesenchymal transition (EMT). Further validation by proteomic screening, co-treatment with disitertide, and SIX1 signal silencing revealed that SIX1, a target of Rh4, induced EMT by activating the TGF-β/Smad2/3 signaling pathway. In summary, our discoveries demonstrated the essential basis of the anti-GC metastatic effects of Rh4 via suppressing the SIX1–TGF-β/Smad2/3 signaling axis, which delivers a new idea for the clinical treatment of GC.

Homeoprotein SIX1 compromises antitumor immunity through TGF-β-mediated regulation of collagens

The tumor microenvironment (TME), including infiltrated immune cells, is known to play an important role in tumor growth; however, the mechanisms underlying tumor immunogenicity have not been fully elucidated. Here, we discovered an unexpected role for the transcription factor SIX1 in regulating the tumor immune microenvironment. Based on analyses of patient datasets, we found that SIX1 was upregulated in human tumor tissues and that its expression levels were negatively correlated with immune cell infiltration in the TME and the overall survival rates of cancer patients. Deletion of Six1 in cancer cells significantly reduced tumor growth in an immune-dependent manner with enhanced antitumor immunity in the TME. Mechanistically, SIX1 was required for the expression of multiple collagen genes via the TGFBR2-dependent Smad2/3 activation pathway, and collagen deposition in the TME hampered immune cell infiltration and activation. Thus, our study uncovers a crucial role for SIX1 in modulating tumor immunogenicity and provides proof-of-concept evidence for targeting SIX1 in cancer immunotherapy.

The Significance of SIX1 as a Prognostic Biomarker for Survival Outcome in Various Cancer Patients: A Systematic Review and Meta-Analysis

Sine Oculis Homeobox Homolog 1 (SIX1) is reported to promote cancer initiation and progression in many preclinical models and is demonstrated in human cancer tissues. However, the correlation between SIX1 and cancer patients’ prognosis has not yet been systematically evaluated. Therefore, we performed a systematic review and meta-analysis in various human cancer types and extracted some data from TCGA datasets for further verification and perfection. We constructed 27 studies and estimated the association between SIX1 expression in various cancer patients’ overall survival and verified with TCGA datasets. Twenty-seven studies with 4899 patients are include in the analysis of overall, and disease-free survival, most of them were retrospective. The pooled hazard ratios (HRs) for overall and disease-free survival in high SIX1 expression patients were 1.54 (95% CI: 1.32-1.80, P<0.00001) and 1.83 (95% CI: 1.31-2.55, P=0.0004) respectively. On subgroup analysis classified in cancer type, high SIX1 expression was associated with poor overall survival in patients with hepatocellular carcinoma (HR 1.50; 95% CI: 1.17-1.93, P =0.001), breast cancer (HR 1.31; 95% CI: 1.10-1.55, P =0.002) and esophageal squamous cell carcinoma (HR 1.89; 95% CI: 1.42-2.52, P<0.0001). Next, we utilized TCGA online datasets, and the consistent results were verified in various cancer types. SIX1 expression indicated its potential to serve as a cancer biomarker and deliver prognostic information in various cancer patients. More works still need to improve the understandings of SIX1 expression and prognosis in different cancer types.

The SIX Family of Transcription Factors: Common Themes Integrating Developmental and Cancer Biology

The sine oculis (SIX) family of transcription factors are key regulators of developmental processes during embryogenesis. Members of this family control gene expression to promote self-renewal of progenitor cell populations and govern mechanisms of cell differentiation. When the function of SIX genes becomes disrupted, distinct congenital defects develops both in animal models and humans. In addition to the embryonic setting, members of the SIX family have been found to be critical regulators of tumorigenesis, promoting cell proliferation, epithelial-to-mesenchymal transition, and metastasis. Research in both the fields of developmental biology and cancer research have provided an extensive understanding of SIX family transcription factor functions. Here we review recent progress in elucidating the role of SIX family genes in congenital disease as well as in the promotion of cancer. Common themes arise when comparing SIX transcription factor function during embryonic and cancer development. We highlight the complementary nature of these two fields and how knowledge in one area can open new aspects of experimentation in the other.

Panel biomarkers associated with cancer invasion and prognostic prediction for head-neck cancer

Aim: Cell invasion leading to metastasis is a major cause of treatment failure in head-neck cancers (HNCs). Identifying prognostic molecules associated with invasiveness is imperative for clinical applications. Materials & methods: A systemic approach was used to globally survey invasion-related genes, including transcriptomic profiling, pathway analysis, data mining and prognostic assessment using TCGA-HNSC dataset. Results: Six functional pathways and six hub molecules (LAMA3, LAMC2, THBS1, IGF1R, PDGFB and TGFβ1) were identified that significantly contributed to cell invasion, leading to poor survival in HNC patients. Combinations of multiple biomarkers substantially increased the probability of accurately predicting prognosis. Conclusion: Our six defined invasion-related molecules may be used as a panel signature in precision medicine for prognostic indicators or molecular therapeutic targets for HNC.

Molecular Interplays Between Cell Invasion and Radioresistance That Lead to Poor Prognosis in Head-Neck Cancer

Background

Cancer metastasis and recurrence after radiotherapy are the significant causes of poor prognosis in head-neck cancer (HNC). Clinically, it is commonly found that patients with either condition may accompany the outcome of the other. We hypothesized that HNC cells might exhibit a cross-phenotypic attribute between cell invasion and radioresistance. To discover effective biomarkers for the intervention of aggressive cancer at one time, the potential molecules that interplay between these two phenotypes were investigated.

Materials and Methods

Three isogenic HNC cell sublines with high invasion or radioresistance properties were established. Transcriptomic and bioinformatic methods were used to globally assess the phenotypic-specific genes, functional pathways, and co-regulatory hub molecules. The associations of gene expressions with patient survival were analyzed by Kaplan-Meier plotter, a web-based tool, using the HNSCC dataset (n=500). The molecular and cellular techniques, including RT-qPCR, flow cytometry, cell invasion assay, and clonogenic survival assay, were applied.

Results

The phenotypic crosstalk between cell invasion and radioresistance was validated, as shown by the existence of mutual properties in each HNC subline. A total of 695 genes was identified in associations with these two phenotypes, including 349 upregulated and 346 downregulated in HNC cells. The focal adhesion mechanism showed the most significant pathway to co-regulate these functions. In the analysis of 20 up-regulatory genes, a general portrait of correlative expression was found between these phenotypic cells (r=0.513, p=0.021), and nine molecules exhibited significant associations with poor prognosis in HNC patients (HR>1, p<0.050). Three hub genes were identified (ITGA6, TGFB1, and NDRG1) that represented a signature of interplayed molecules contributing to cell invasion, radioresistance and leading to poor prognosis. The ITGA6 was demonstrated as a prominent biomarker. The expression of ITGA6 correlated with the levels of several extracellular and apoptotic/anti-apoptotic molecules. Functionally, silencing ITGA6 suppressed cell migration, invasion, and attenuated radioresistance in HNC cells.

Conclusions

A panel of interplay molecules was identified that contribute to cell invasion and radioresistance, leading to poor prognosis. These panel molecules, such as ITGA6, may serve as predictive markers of radioresistance, prognostic markers of metastasis, and molecular therapeutic targets for refractory HNC.

High expression of SIX1 is an independent predictor of poor prognosis in endometrial cancer

Objective: The overexpression of transcription factor Sine oculis homeobox 1 (SIX1) is discovered in various malignant tumors and has been known to be closely associated with tumorigenesis, progression and prognosis. This study aims to determine the role of SIX1 in endometrial cancer (EC). Methods: In this study, we analyzed the SIX1 expression profile and the correlation with the corresponding clinical characteristics of EC samples from the Cancer Genome Atlas (TCGA), Gene Expression Omnibus (GEO) and Clinical Proteomic Tumor Analysis Consortium (CPTAC) databases. Wilcoxon signed-rank test was applied to analyze the difference between tumor group and control group. The potential biological processes or signaling pathways related to SIX1 activity in EC was also assessed. Results: The results showed that SIX1 was overexpressed in EC tissues compared to normal tissues (P=2.029e-15, P=6.25e-6). The SIX1 level was correlated with tumor grade (P=2.91e-4), peritoneal cytology (P=0.005), and the subsequent tumor surgery (P=1.169e-4). SIX1 expression was negatively associated with overall survival rate (P=4.241e-4, P=0.000241) and served as an independent factor that affected EC overall survival rate (P=0.005063), similar to other factors such as age, Figo stage, and tumor (T) stage. SIX1 participates in cancer pathogenesis through gene regulation that involves PI3K/AKT/MTOR signaling, mitotic spindle, G2M checkpoint, E2F targets, NOTCH signaling, glycolysis, cholesterol homeostasis, DNA repair and early estrogen response. Conclusions: Our data demonstrate that SIX1 is overexpressed in EC and associated with adverse clinicopathological outcomes, which can function as an independent factor for EC prognosis.

miR‑93‑5p regulates the occurrence and development of esophageal carcinoma epithelial cells by targeting TGFβR2

Emerging studies have indicated that the dysregulation of microRNAs (miRNAs or miRs) plays a vital role in the development and metastasis of tumors. However, the role of miR-93-5p in esophageal carcinoma (EC) has not been extensively reported. The present study thus focused on the role of miR-93-5p and its downstream target in the occurrence and development of EC. Firstly, miRNA expression profiles associated with EC were accessed from the TCGA_ESCA dataset and analyzed. Subsequently, the expression patterns of miR-93-5p and TGFβR2 were characterized in the human esophageal cell line, Het-1A, and the human EC cell lines, TE-1, Eca-109 and EC9706, by RT-qPCR and western blot analysis. WST-1 assay, flow cytometry, Transwell assay, wound healing assay and bioinformatics analysis were used to explore their functions in EC cells. Finally, a dual-luciferase reporter assay was employed to determine the targeted association between miR-93-5p and TGFβR2. The results revealed that the expression of miR-93-5p was markedly higher in EC cell lines compared with that in the normal cell line. The overexpression of miR-93-5p facilitated cell proliferation, migration and invasion, and inhibited cell apoptosis. Additionally, TGFβR2 was identified as a functional target of miR-93-5p in EC cells, as judged by a series of in vitro experiments. Furthermore, it was found that the simultaneous overexpression of miR-93-5p and TGFβR2 almost had no effect on the biological behaviors of EC cells. On the whole, the present study demonstrates that miR-93-5p promotes the proliferation, migration and invasion, and inhibits the apoptosis of EC cells by targeting TGFβR2.

SPOCK1/SIX1axis promotes breast cancer progression by activating AKT/mTOR signaling

SPOCK1 is highly expressed in many types of cancer and has been recognized as a promoter of cancer progression. Its regulatory mechanism in breast cancer (BC) remains unclear. This study aimed to explore the precise function of SPOCK1 in BC progression and to identify the mechanism by which SPOCK1 is involved in cell proliferation and epithelial-mesenchymal transition (EMT). Immunohistochemistry (IHC) experiments and database analysis showed that high expression of SPOCK1 was positively associated with histological grade, lymph node metastasis (LN) and poor clinical prognosis in BC. A series of in vitro and in vivo assays elucidated that altering the SPOCK1 level led to distinct changes in BC cell proliferation and metastasis. Investigations of potential mechanisms revealed that SPOCK1 interacted with SIX1 to enhance cell proliferation, cell cycle progression and EMT by activating the AKT/mTOR pathway, whereas inhibition of the AKT/mTOR pathway or depletion of SIX1 reversed the effects of SPOCK1 overexpression. Furthermore, SPOCK1 and SIX1 were highly expressed in BC and might indicate poor prognoses. Altogether, the SPOCK1/SIX1 axis promoted BC progression by activating the AKT/mTOR pathway to accelerate cell proliferation and promote metastasis in BC, so the SPOCK1/SIX1 axis might be a promising clinical therapeutic target for preventing BC progression.

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.

Metabolism and immunity in breast cancer

Breast cancer is one of the most common malignancies that seriously threaten women's health. In the process of the malignant transformation of breast cancer, metabolic reprogramming and immune evasion represent the two main fascinating characteristics of cancer and facilitate cancer cell proliferation. Breast cancer cells generate energy through increased glucose metabolism. Lipid metabolism contributes to biological signal pathways and forms cell membranes except energy generation. Amino acids act as basic protein units and metabolic regulators in supporting cell growth. For tumor-associated immunity, poor immunogenicity and heightened immunosuppression cause breast cancer cells to evade the host's immune system. For the past few years, the complex mechanisms of metabolic reprogramming and immune evasion are deeply investigated, and the genes involved in these processes are used as clinical therapeutic targets for breast cancer. Here, we review the recent findings related to abnormal metabolism and immune characteristics, regulatory mechanisms, their links, and relevant therapeutic strategies.

Silencing SIX1 inhibits epithelial mesenchymal transition through regulating TGF-β/Smad2/3 signaling pathway in papillary thyroid carcinoma

OBJECTIVE

To investigate the sineoculis homeobox homolog 1 (SIX1) affect the epithelial mesenchymal transition (EMT) in papillary thyroid carcinoma (PTC) through regulating TGF-β/Smad2/3 signaling pathway.

METHODS

The SIX1 expression in cytological specimens, tissues or PTC cell lines was detected by qRT-PCR, western blotting or immunohistochemistry. A series of vitro experiments including flow cytometry, CCK-8, wound-healing and Transwell were used to evaluate the biological characteristics in a PTC cell line (NPA cells), which were divided into Blank, Negative control (NC), SIX1, SIX1-siRNA, LY-364947 (TGF-β/Smad2/3 pathway inhibitor) and SIX1 + LY-364947 groups. TGF-β/Smad2/3 pathway and EMT related protein expression were measured by qRT-PCR and western blotting.

RESULTS

SIX1 mRNA expression was increased in cytological specimens from PTC patients as compared with the non-toxic nodular goitre (NTG) patients. Moreover, compared with adjacent normal tissues, expressions of SIX1, N-cadherin and Vimentin were higher while E-cadherin was lower in PTC tissues; and SIX1 was positively correlated with N-cadherin and Vimentin but was negatively correlated with E-cadherin. Furthermore, the SIX1 expression was associated with histopathology, extrathyroidal extension (ETE), lymph node metastasis (LNM), pT stage, TNM stage, and distant metastasis. In addition, the expressions of TGFβ1, p-SMAD2/3, N-cadherin and Vimentin were downregulated in NPA cells after LY-364947 treatment with upregulated E-cadherin, decreased cell proliferation and metastasis, and enhanced cell apoptosis, which was reversed by SIX1 overexpression.

CONCLUSION

Silencing SIX1 can inhibit TGF-β/Smad2/3 pathway, thereby suppressing EMT in PTC, which may be a novel avenue for the treatment of PTC.

SIX1 and SIX4 homeoproteins regulate PAX7+ progenitor cell properties during fetal epaxial myogenesis

Pax7 expression marks stem cells in developing skeletal muscles and adult satellite cells during homeostasis and muscle regeneration. The genetic determinants that control the entrance into the myogenic program and the appearance of PAX7+ cells during embryogenesis are poorly understood. SIX homeoproteins are encoded by the sine oculis-related homeobox Six1-Six6 genes in vertebrates. Six1, Six2, Six4 and Six5 are expressed in the muscle lineage. Here, we tested the hypothesis that Six1 and Six4 could participate in the genesis of myogenic stem cells. We show that fewer PAX7+ cells occupy a satellite cell position between the myofiber and its associated basal lamina in Six1 and Six4 knockout mice (s1s4KO) at E18. However, PAX7+ cells are detected in remaining muscle masses present in the epaxial region of the double mutant embryos and are able to divide and contribute to muscle growth. To further characterize the properties of s1s4KO PAX7+ cells, we analyzed their transcriptome and tested their properties after transplantation in adult regenerating tibialis anterior muscle. Mutant stem cells contribute to hypotrophic myofibers that are not innervated but retain the ability to self-renew.

MiR-204-5p Inhibits Transforming Growth Factor-β1-Induced Proliferation and Extracellular Matrix Production of Airway Smooth Muscle Cells by Regulating Six1 in Asthma

BACKGROUND

Transforming growth factor-β1 (TGF-β1)-in-duced proliferation of airway smooth muscle cells plays critical roles in the development of airway remodeling. Six1 (sine oculis homeobox homolog 1) has been demonstrated to be involved in airway inflammation and remodeling in asthmatic mice.

OBJECTIVES

The aim of this work was to investigate the potential role of miR-204-5p in the proliferation and extracellular matrix (ECM) production of airway smooth muscle cells in asthma.

METHODS

Real-time PCR was used to measure the expression of miR-204-5p in asthmatic airway smooth muscle cells. Cell viability and apoptosis were detected to evaluate the effect of miR-204-5p on airway smooth muscle cells. Dual-luciferase reporter experiments were applied to identify the target genes of miR-204-5p.

RESULTS

MiR-204-5p was downregulated notably in asthmatic airway smooth muscle cells as well as cells stimulated with TGF-β1. Overexpression of miR-204-5p markedly suppressed the TGF-β1-induced proliferation of airway smooth muscle cells and the deposition of ECM, whereas the inhibition of miR-204-5p significantly enhanced the proliferation of airway smooth muscle cells and upregulated the level of fibronectin and collagen III. Furthermore, subsequent analyses demonstrated that Six1 was a direct target of miR-204-5p, and Western blot further indicated that miR-204-5p negatively regulated the expression of Six1. Most importantly, the restoration of Six1 expression reversed the inhibitory effect of miR-204-5p on TGF-β1-induced proliferation and ECM production.

CONCLUSIONS

MiR-204-5p inhibits TGF-β1-in-duced proliferation and ECM production of airway smooth muscle cells by regulating Six1, identifying a potential therapeutic target for preventing airway remodeling in asthma.

Six2 is negatively correlated with prognosis and facilitates epithelial-mesenchymal transition via TGF-β/Smad signal pathway in hepatocellular carcinoma

BACKGROUND

Increasing evidence indicates that Six2 contributes to tumorigenesis in various tumor including hepatocellular carcinoma (HCC). This study aimed to determine the role of Six2 in HCC and to elucidate the association of Six2 with clinical pathological characteristics.

METHODS

The expressions of Six2 in HCC tumor, para-tumor tissue and portal vein tumor thrombus (PVTT) were detected by tissue microarray technique, immunohistochemistry, real-time RT-PCR and Western blotting. Chi-square and Kaplan-Meier analysis were used to analyze the correlation between Six2 expression and prognosis of HCC patients. Lentivirus mediated Six2 knockdown, spheroid formation assay, proliferation assay and subcutaneous tumor implantation were performed to determine the function of Six2.

RESULTS

In 274 HCC samples, Six2 was strongly expressed. Kaplan-Meier analysis revealed that high expression of Six2 was correlated with a shorter overall survival (OS) and disease-free survival (DFS). Moreover, Six2 expression was associated with sex, alpha-fetoprotein, tumor size and portal vein invasion. Six2 was highly expressed in PVTT. Six2 knockdown inhibited HCC cell lines proliferation, migration, and self-renewal in vitro and in vivo. In addition, low-expression of Six2 weakened TGF-β induced Smad4 activation and epithelial-mesenchymal transition in HCC cell lines.

CONCLUSIONS

Elevated Six2 expression in HCC tumor patients was associated with negative prognosis. Upregulated Six2 promoted tumor growth and facilitated HCC metastasis via TGF-β/Smad signal pathway.

miR-489-3p/SIX1 Axis Regulates Melanoma Proliferation and Glycolytic Potential

Sine oculis homeobox 1 (SIX1), a key transcription factor for regulating aerobic glycolysis, participates in the occurrence of various cancer types. However, the role of SIX1 in melanoma and the upstream regulating mechanisms of SIX1 remain to be further investigated. MicroRNAs (miRNAs) have emerged as key regulators in tumorigenesis and progression. Here, we show that miR-489-3p suppresses SIX1 expression by directly targeting its 3′ untranslated region (3′ UTR) in melanoma cells. miR-489-3p suppressed melanoma cell proliferation, migration, and invasion through inhibition of SIX1. Mechanistically, by targeting SIX1, miR-489-3p dampens glycolysis, with decreased glucose uptake, lactate production, ATP generation, and extracellular acidification rate (ECAR), as well as an increased oxygen consumption rate (OCR). Importantly, glycolysis regulated by the miR-489-3p/SIX1 axis is critical for its regulation of melanoma growth and metastasis both in vitro and in vivo. In melanoma patients, miR-489-3p expression is negatively correlated with SIX1 expression. In addition, patients who had increased glucose uptake in tumors and with metastasis assessed by positron emission tomography (PET) scans showed decreased miR-489-3p expression and increased expression of SIX1. Collectively, our study demonstrates the importance of the miR-489-3p/SIX1 axis in melanoma, which can be a potential and a promising therapeutic target in melanoma.

Circular RNA circNHSL1 promotes gastric cancer progression through the miR-1306-3p/SIX1/vimentin axis

Background

Mounting evidences indicate that circular RNAs (circRNAs) play vital roles in the development and progression of various cancers. However, the detail functions and underlying mechanisms of circRNAs in gastric cancer remain largely unknown.

Methods

The expression profile of metastasis-related circRNAs was screened by RNA-seq analysis. qRT-PCR was used to determine the level and prognostic values of circNHSL1 in gastric cancer tissues. In vitro cell wound healing and transwell (migration and invasion) and in vivo tumorigenesis and metastasis assays were performed to evaluate the functions of circNHSL1. Luciferase reporter, RNA immunoprecipitation (RIP) and rescued assays were employed to confirm the interactions between circNHSL1, miR-1306-3p and SIX1. It’s widely accepted that as a mesenchymal marker, Vimentin promotes invasion and metastasis in various cancers. Luciferase reporter assay was used to determine the regulation of SIX1 on Vimentin. In addition, In situ hybridization (ISH) was performed to detect the level and prognostic values of miR-1306-3p.

Results

We found that the level of circNHSL1 was significantly up-regulated in gastric cancer, and positively correlated with clinicopathological features and poor prognosis of patients with gastric cancer. Functionally, circNHSL1 promoted cell mobility and invasion, as well as in vivo tumorgenesis and metastasis. Mechanistically, circNHSL1 acted as a miR-1306-3p sponge to relieve the repressive effect of miR-1306-3p on its target SIX1. Moreover, SIX1 enhanced Vimentin expression in the transcriptional level through directly binding to the promoter domain of Vimentin, thereby promoting cell migration and invasion. In addition, miR-1306-3p was down-regulated and negatively correlated with pathological features and poor prognosis in gastric cancer.

Conclusions

CircNHSL1 promotes gastric cancer progression through miR-1306-3p/SIX1/Vimentin axis, and may serve as a novel diagnostic marker and target for treatment of gastric cancer patients.

Electronic supplementary material

The online version of this article (10.1186/s12943-019-1054-7) contains supplementary material, which is available to authorized users.

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.

miR-30b-5p acts as a tumor suppressor microRNA in esophageal squamous cell carcinoma

Background

To study miR-30b-5p expression in esophageal squamous cell carcinoma (ESCC) by comparisons between tumor tissues and matched adjacent non-cancerous tissues to elucidate the correlation between miR-30b-5p expression and ESCC clinical parameters, and to explore the signaling pathways associated with miR-30b-5p and key target genes.

Methods

Clinical data, cancer tissues, and adjacent non-cancerous tissues of 32 patients diagnosed with ESCC were collected from Taizhou Hospital of Zhejiang Province. The expression levels of miR-30b-5p were determined by real-time polymerase chain reaction (RT-PCR). mRNA data for ESCC tissues and normal tissues, and clinical materials of patients with ESCC were obtained from the Gene Expression Omnibus (GEO) database and The Cancer Genome Atlas (TCGA). Associations between miR-30b-5p expression and clinical features of patients with ESCC and overall survival were explored. A bioinformatics analysis was performed to determine the pathways and key miR-30b-5p targets associated with ESCC. Additionally, a cytological experiment was performed to evaluate the biological functions of miR-30b-5p. Finally, correlations between miR-30b-5p and key targets involved in PI3K/Akt signaling pathways were validated by western blotting.

Results

The expression level of miR-30b-5p in the 32 ESCC tissues was significantly lower than that in adjacent normal tissues (P<0.01) and was significantly disparate in the T stage, with higher expression in T1 than in T2 (P<0.05). Among the patients with higher expression levels of miR-30b-5p in ESCC tissues than in adjacent normal tissues, patients with higher expression of miR-30b-5p had a better prognosis (P<0.05). An analysis of gene chip data from the GEO database showed similar results. A gene enrichment analysis indicated a series of pathways that may be associated with the downregulation of miR-30b-5p, including focal adhesion, ECM-receptor interaction, and PI3K/Akt signaling pathways. Seven key target genes (PDGFRB, VIM, ITGA5, ACTN1, THBS2, SERPINE1, and RUNX2) were identified; these were found to be upregulated in ESCC tissues and were negatively correlated with miR-30b-5p. Functional experiments showed that miR-30b-5p attenuated migration (P<0.01) and invasion (P<0.05) in the Eca109 cell line. Moreover, the levels of ITGA5, PDGFRB, p-PI3K, and p-AKT, which are involved in the PI3K/Akt signaling pathway, were decreased in the miR-30b-5p-overexpressing Eca109 cell line.

Conclusions

Upregulated miR-30b-5p may inhibit migration and invasion in ESCC by targeting ITGA5, PDGFRB, and signaling pathways, such as PI3K/Akt, involved in ESCC regulation. Our results indicate that miR-30b-5p plays an important role in the occurrence and progression of ESCC and is a potential therapeutic target.

MiR-150-5p regulates melanoma proliferation, invasion and metastasis via SIX1-mediated Warburg Effect

Aerobic glycolysis is a hallmark of cancer. Sine oculis homeobox 1 (SIX1), a key transcription factor in terms of regulating aerobic glycolysis (the Warburg Effect), plays a critical role in tumorigenesis of various cancer types, including breast cancer, liver cancer, and lung cancer. However, the upstream regulating mechanisms of SIX1 in melanoma remain to be determined. MicroRNAs (miRNAs) have emerged as key regulators in tumorigenesis and progression. Here, we initially showed that microRNA-150-5p (miR-150-5p) inhibits SIX1 expression by directly targeting its 3'-UTR in melanoma cells. miR-150-5p suppressed melanoma cell proliferation, migration, and invasion through inhibition of SIX1. Mechanistically, miR-150-5p dampens glycolysis by decreasing the glucose uptake, lactate production, ATP generation, and extracellular acidification rate (ECAR), and increasing oxygen consumption rate (OCR) by targeting SIX1. Importantly, glycolysis regulated by miR-150-5p/SIX1 axis is critical for its regulation of melanoma growth and metastasis both in vitro and in vivo. Collectively, our study demonstrates the importance of miR-150-5p/SIX1 axis in melanoma, which could be a promising therapeutic target in melanoma.

Gene Expression Profiling Reveals Distinct Molecular Subtypes of Esophageal Squamous Cell Carcinoma in Asian Populations

Esophageal squamous cell carcinoma (ESCC) is one of the most common cancers worldwide, particularly in Asian populations, and responds poorly to conventional therapy. Subclassification of ESCCs by molecular analysis is a powerful strategy in extending conventional clinicopathologic classification, improving prognosis and therapy. Here we identified two ESCC molecular subtypes in Chinese population using gene expression profiling data and further validated the molecular subtypes in two other independent Asian populations (Japanese and Vietnamese). Subtype I ESCCs were enriched in pathways including immune response, while genes overexpressed in subtype II ESCCs were mainly involved in ectoderm development, glycolysis process, and cell proliferation. Specifically, we identified potential ESCC subtype-specific diagnostic markers (FOXA1 and EYA2 for subtype I, LAMC2 and KRT14 for subtype II) and further validated them in a fourth Asian cohort. In addition, we propose a few subtype-specific therapeutic targets for ESCC, which may guide future ESCC clinical treatment when further validated.

Possible biomarkers for predicting lymph node metastasis of esophageal squamous cell carcinoma: a review

Esophageal cancer is the eighth most common form of cancer worldwide, and esophageal squamous cell carcinoma (ESCC) is a major type of esophageal cancer that arises from epithelial cells of the esophagus. Local lymph node metastasis (LNM) is a typical sign of failure for ESCC clinical treatments, and a link has been established between LNM and the aberrant expression of specific biomarkers. In this review, we summarize what is known about nine factors significantly associated with LNM in ESCC patients: phosphatase and tensin homolog (PTEN), mucin 1, vascular endothelial growth factor-C, tumor necrosis factor alpha-induced protein 8 (TNFAIP8), Raf-1 kinase inhibitory protein, stathmin (STMN1), metastasis-associated protein 1, caveolin-1, and interferon-induced transmembrane protein 3. The function of these nine proteins involves four major mechanisms: tumor cell proliferation, tumor cell migration and invasion, epithelium–mesenchymal transition, and chemosensitivity. The roles of PTEN, STMN1, and TNFAIP8 involve at least two of these mechanisms, and we suggest that they are possible biomarkers for predicting LNM in ESCC. However, further retrospective research into PTEN, STMN1, and TNFAIP8 is needed to test their possibilities as indicators.

Regulation of cancer stem cell properties by SIX1, a member of the PAX-SIX-EYA-DACH network

The PAX-SIX-EYA-DACH network (PSEDN) is a central developmental transcriptional regulatory network from Drosophila to humans. The PSEDN is comprised of four conserved protein families; including paired box (PAX), sine oculis (SIX), eyes absent (EYA), and dachshund (DACH). Aberrant expression of PSEDN members, particularly SIX1, has been observed in multiple human cancers, where SIX1 expression correlates with increased aggressiveness and poor prognosis. In conjunction with its transcriptional activator EYA, the SIX1 transcription factor increases cancer stem cell (CSC) numbers and induces epithelial-mesenchymal transition (EMT). SIX1 promotes multiple hallmarks and enabling characteristics of cancer via regulation of cell proliferation, senescence, apoptosis, genome stability, and energy metabolism. SIX1 also influences the tumor microenvironment, enhancing recruitment of tumor-associated macrophages and stimulating angiogenesis, to promote tumor development and progression. EYA proteins are multifunctional, possessing a transcriptional activation domain and tyrosine phosphatase activity, that each contributes to cancer stem cell properties. DACH proteins function as tumor suppressors in solid cancers, opposing the actions of SIX-EYA and reducing CSC prevalence. Multiple mechanisms can lead to increased SIX1 expression, including loss of SIX1-targeting tumor suppressor microRNAs (miRs), whose expression correlates inversely with SIX1 expression in cancer patient samples. In this review, we discuss the major mechanisms by which SIX1 confers CSC and EMT features and other important cancer cell characteristics. The roles of EYA and DACH in CSCs and cancer progression are briefly highlighted. Finally, we summarize the clinical significance of SIX1 in cancer to emphasize the potential therapeutic benefits of effective strategies to disrupt PSEDN protein interactions and functions.

MiR-448-5p inhibits TGF-β1-induced epithelial-mesenchymal transition and pulmonary fibrosis by targeting Six1 in asthma

MicroRNAs (miRNAs) are small yet versatile gene tuners that regulate a variety of cellular processes, including cell growth and proliferation. The aim of this study was to explore how miR-448-5p affects airway remodeling and transforming growth factor-β1 (TGF-β1)-stimulated epithelial-mesenchymal transition (EMT) by targeting Sine oculis homeobox homolog 1 (Six1) in asthma. Asthmatic mice models with airway remodeling were induced with ovalbumin solution. MiRNA expression was evaluated using quantitative real-time polymerase chain reaction. Transfection studies of bronchial epithelial cells were performed to determine the target genes. A luciferase reporter assay system was applied to identify whether Six1 is a target gene of miR-448-5p. In the current study, we found that miR-448-5p was dramatically decreased in lung tissues of asthmatic mice and TGF-β1-stimulated bronchial epithelial cells. In addition, the decreased level of miR-448-5p was closely associated with the increased expression of Six1. Overexpression of miR-448-5p decreased Six1 expression and, in turn, suppressed TGF-β1-mediated EMT and fibrosis. Next, we predicted that Six1 was a potential target gene of miR-448-5p and demonstrated that miR-448-5p could directly target Six1. An SiRNA targeting Six1 was sufficient to suppress TGF-β1-induced EMT and fibrosis in 16HBE cells. Furthermore, the overexpression of Six1 partially reversed the protective effect of miR-448-5p on TGF-β1-mediated EMT and fibrosis in bronchial epithelial cells. Taken together, the miR-448-5p/TGF-β1/Six1 link may play roles in the progression of EMT and pulmonary fibrosis in asthma.

The regulation of cytokine signaling by retinal determination gene network pathway in cancer

Tumor environment plays a pivotal role in determining cancer biology characteristics. Cytokine factors, as a critical component in tumor milieu, execute distinct functions in the process of tumorigenesis and progression via the autocrine or paracrine manner. The retinal determination gene network (RDGN), which mainly comprised DACH, SIX, and EYA family members, is required for the organ development in mammalian species. While the aberrant expression of RDGN is involved in the proliferation, apoptosis, angiogenesis, and metastasis of tumors via interacting with different cytokine-related signals, such as CXCL8, IL-6, TGF-β, FGF, and VEGF, in a cell- or tissue-dependent manner. Thus, joint detection of this pathway might be used as a potential biomarker for the stratification of target therapy and for the precision prediction of the prognosis of cancer patients.

Overexpression of KIFC1 and its association with spheroid formation in esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) is one of the most common human cancers. We previously reported that KIFC1 is involved in gastric cancer pathogenesis and that KIFC1 plays an important role in gastric cancer spheroid colony formation. However, the significance of KIFC1 in ESCC has not been examined. In the present study, we analyzed the expression and distribution of KIFC1 in 132 ESCC cases by immunohistochemistry. In contrast to weak or no staining of KIFC1 in non-neoplastic mucosa, ESCC tissue showed stronger, more extensive KIFC1 staining. In total, 95 (72%) of 132 ESCC cases were positive for KIFC1. Immunostaining of ALDH1 was also performed, and KIFC1-positive ESCC cases were significantly frequently found in ALDH1-positive ESCC cases compared with ALDH1-negative ESCC cases. Spheroid colony formation is an effective method to characterize CSCs, thus we analyzed sphere number and size at 15days in ESCC cells downregulated for KIFC1 by siRNA transfection. Both the number and size of sphere from TE-1 cells were significantly reduced in KIFC1 siRNA-transfected TE-1 cells than in negative control siRNA-transfected cells. These results suggest that KIFC1 plays an important role in ESCC pathogenesis.

SIX1 maintains tumor basal cells via transforming growth factor-β pathway and associates with poor prognosis in esophageal cancer

Esophageal squamous cell carcinoma (ESCC) is one of the most common malignant tumors. Although improvement in both surgical techniques and neoadjuvant chemotherapy has been achieved, the 5-year survival rate of locally advanced tumors was, at best, still 55%. Therefore, elucidation of mechanisms of the malignancy is eagerly awaited. Epithelial-mesenchymal transition (EMT) by transforming growth factor-β (TGF-β) has been reported to have critical biological roles for cancer cell stemness, whereas little is known about it in ESCC. In the current study, a transcriptional factor SIX1 was found to be aberrantly expressed in ESCCs. SIX1 cDNA transfection induced overexpression of transforming growth factors (TGFB1 and TGFB2) and its receptor (TGFBR2). Cell invasion was reduced by SIX1 knockdown and was increased in stable SIX1-transfectants. Furthermore, the SIX1-transfectants highly expressed tumor basal cell markers such as NGFR, SOX2, ALDH1A1, and PDPN. Although mock-transfectants had only a 20% PDPN-high population, SIX1-transfectants had 60-70%. In two sets of 42 and 85 ESCC patients receiving surgery alone or neoadjuvant chemoradiotherapy followed by surgery, the cases with high SIX1 mRNA and protein expression level significantly showed a poor prognosis compared with those with low levels. These SIX1 high cases also expressed the above basal cell markers, but suppressed the differentiation markers. Finally, TGF-β signaling blockade suppressed ESCC cell growth in association with the reduction of PDPN-positive tumor basal cell population. The present results suggest that SIX1 accelerates self-renewal of tumor basal cells, resulting in a poor prognosis for ESCC patients.