SIX4 acts as a master regulator of oncogenes that promotes tumorigenesis in non-small-cell lung cancer cells

Hinokiflavone exerts dual regulation on apoptosis and pyroptosis via the SIX4/Stat3/Akt pathway to alleviate APAP-induced liver injury

Hinokiflavone (HF), classified as a flavonoid, is a main bioactive compound in Platycladus orientalis and Selaginella. HF exhibits activities including anti-HIV, anti-inflammatory, antiviral, antioxidant and anti-tumor effects. The study aimed to explore the function and the mechanisms of HF on acetaminophen (APAP)-induced acute liver injury. Results indicated that HF treatment mitigated the impact of APAP on viability and restored levels of MDA, GSH and SOD on HepG2 cells. The accumulation of reactive oxygen species (ROS) mitochondrial membrane potential (MMP) in HepG2 cells stimulated by APAP were also blocked by HF. HF reduced the levels of pro-apoptotic and pro-pyroptotic proteins. Flow cytometry analysis and fluorescence staining results were consistent with western blot analysis. Following HF treatment in the APAP-induced cell model, there was observed an augmentation in the phosphorylation of Stat3 and an increase in the expression of SIX4. However, not only silenced the SIX4 protein in HepG2 cells by siRNA, but also adding the Stat3 inhibitor (Stattic), attenuated the anti-apoptotic and anti-pyroptotic effects of HF significantly. Furthermore, HF alleviated liver damage in C57BL/6 mice model. Overall, our study demonstrated that HF mitigates apoptosis and pyroptosis induced by APAP in drug-induced liver injury (DILI) through the SIX4/Akt/Stat3 pathway in vivo and in vitro. HF may have promising potential for for the treatment of DILI.

Resveratrol suppresses NSCLC cell growth, invasion and migration by mediating Wnt/β-catenin pathway via downregulating SIX4 and SPHK2

Resveratrol (RSV) has been found to have a cancer-suppressing effect in a variety of cancers, including non-small cell lung cancer (NSCLC). Studies have shown that sine oculis homeobox 4 (SIX4) and sphingosine kinase 2 (SPHK2) are tumour promoters of NSCLC. However, whether RSV regulates SIX4 and SPHK2 to mediate NSCLC cell functions remains unclear. NSCLC cell functions were assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay, 5-ethynyl-2'-deoxyuridine (EdU) assay, flow cytometry, transwell assay and wound healing assay. Protein expression levels were detected by western blot. SIX4 and SPHK2 mRNA levels in NSCLC tumour tissues were examined using quantitative real-time PCR. In addition, mice xenograft models were built to explore the impact of RSV on NSCLC tumour growth. RSV inhibited NSCLC cell proliferation, invasion and migration, while facilitated apoptosis. SIX4 and SPHK2 were up-regulated in NSCLC tissues and cells, and their expression was reduced by RSV. Knockdown of SIX4 and SPHK2 suppressed NSCLC cell growth, invasion and migration, and the regulation of RSV on NSCLC cell functions could be reversed by SIX4 and SPHK2 overexpression. RSV inactivated Wnt/β-catenin pathway via decreasing SIX4 and SPHK2 levels. In animal experiments, RSV reduced NSCLC tumour growth in vivo. RSV repressed NSCLC malignant process by decreasing SIX4 and SPHK2 levels to restrain the activity of Wnt/β-catenin pathway.

SIX4 Controls Anti-PD-1 Efficacy by Regulating STING Expression

The cGAS/STING cytosolic DNA-sensing pathway plays a significant role in antitumor immunity. Expression of STING is tightly regulated and commonly reduced or defective in many types of cancer. We have identified SIX4 as a significant regulator of STING expression in colon cancer cells. We showed that knockout of SIX4 decreased STING expression at the mRNA and protein levels while ectopic expression of SIX4 increased STING expression. Depletion of SIX4 led to attenuated STING activation and downstream signaling. Reexpression of SIX4 or ectopic expression of STING in SIX4 knockout cells reversed the effect. Ectopic expression of SIX4 enhanced DMXAA and cGAMP-induced STING activation and downstream signaling. Importantly, decrease of SIX4 expression substantially decreased tumor infiltration of CD8+ T cells and reduced the efficacy of PD-1 antibodies to diminish tumor growth in immune competent mice in vivo. Finally, analysis of The Cancer Genome Atlas colon cancer dataset indicated that tumors with high SIX4 expression were significantly enriched in the Inflammatory Response pathway. SIX4 expression also correlated with expression of multiple IFN-stimulated genes, inflammatory cytokines, and CD8A. Taken together, our results implicate that SIX4 is a principal regulator of STING expression in colon cancer cells, providing an additional mechanism and genetic marker to predict effective immune checkpoint blockade therapy responses.

SIGNIFICANCE

Our studies demonstrate that SIX4 is an important regulator of STING expression, providing a genetic marker or a therapeutic target to predict or enhance immune checkpoint blockade therapy responses in colon cancer.

Combination of SIX4-siRNA and temozolomide inhibits the growth and migration of A-172 glioblastoma cancer cells

Glioblastoma is one of the most common and invasive types of primary brain malignancies in adults, accounting for 45.5% of malignancies. Its annual prevalence is low compared to other cancers. The survival rate of this disease is about 14 months after diagnosis. Temozolomide (TMZ) is a common chemotherapy drug used to treatment of glioblastoma, but drug resistance against this drug is an important barrier to successful treatment of this cancer. Today, siRNAs play a significant role in cancer treatment. SIX4 is a transcriptional regulatory molecule that can act as a transcriptional suppressor and an activator in target genes involved in differentiation, migration, and cell survival processes. The aim of this study was to evaluate the effect of SIX4-siRNA on A-172 glioblastoma cells, its role as a tumor suppressor, and its combination with TMZ. We studied the cytotoxic effect of the SIX4-siRNA and TMZ on A-172 cells using the MTT assay investigated their effect on apoptosis and cell cycle of A-172 cells used wound healing assays to assess their effect on cell migration. Finally, we used qRT-PCR to study the mRNA expression levels of genes involved in apoptosis and migration of tumoral cells after treatments. Based on our results, silencing SIX4-siRNA expression reduced the cell viability of A-172 cells and sensitize these cells to TMZ. Furthermore, we observed an increase in apoptosis and cell cycle arrest, and a decrease in migration. Bax and caspase-9 overexpression and BCL2 and MMP9 downregulation were detected in the combination of SIX4-siRNA and TMZ. According to our results, the combination of SIX4-siRNA and TMZ can be a very useful strategy for successful glioblastoma treatment.

Knockdown of SIX4 inhibits pancreatic cancer cells via apoptosis induction

Sine oculis homeobox 4 (SIX4), a critical transcription factor modulating organ development, potentially participates in tumorigenesis through numerous pathways. Here, we investigated siRNA-mediated knockdown effects of SIX4 on pancreatic cancer cells and underlying molecular mechanisms. The expression of SIX4 in pancreatic cancer and adjacent tissues were investigated in clinical tissue samples and bioinformatically approved by gene expression omnibus (GEO) database. Appropriate siRNA transfected into PANC1 pancreatic cancer cells in order to SIX4 knockdown. The survival, migration, invasion, colony formation, mitochondrial membrane potential, apoptosis, autophagy, and cell cycle in the cancer cells were investigated after knockdown of SIX4. In addition, expression of genes involved in apoptosis and metastasis were assessed in the transfected cancer cells in mRNA and protein levels. High-throughput analysis using GEO database confirmed the overexpression of SIX4 in pancreatic cancer tissues by six independent pancreatic cancer microarrays. Knockdown of SIX4 by specific siRNA significantly decreased survival, colony formation, and mitochondrial membrane potential of the cancer cells. Further assessments demonstrated that knockdown of SIX4 increases the apoptosis and autophagy rates in the cancer cells through modifying the expression of related genes. Moreover, a significant decrease in migration and invasion rates were observed in SIX4 suppressed group. Furthermore, frequency of the cells transfected with SIX4 siRNA increased slightly in G1 and Sub-G1 phases of cell cycle. Our study suggested that siRNA-mediated knockdown of SIX4 increases the pancreatic cancer cells death and reduces the invasion and migration of the cancer cells through different molecular pathways.

SIX4, a potential therapeutic target for estrogen receptor-positive breast cancer patients, is associated with low promoter methylation level

Aim: To investigate SIX4 in breast cancer. Methods: Publicly available online tools were used to analyze the expression, methylation and prognostic significance of SIX4 in breast cancer, as well as its immunohistochemistry. Results: High SIX4 levels were associated with low SIX4 promoter methylation, especially in estrogen receptor-positive breast cancer. Increased SIX4 was related to advanced stage and decreased immune infiltration. Gene set enrichment analysis found that the SIX4-correlated genes were enriched in transcriptional processing and immune response. Patients with high SIX4 expression tended to have poor survival, especially those with estrogen receptor-positive breast cancer. Conclusion: High SIX4 expression in breast cancer plays an oncogenic role, promoting the development of malignancies through suppressing the immune response, especially in luminal subtypes, and is associated with a low promoter methylation level.

IGF2BP3‑stabilized SIX4 promotes the proliferation, migration, invasion and tube formation of ovarian cancer cells

The mortality rate of ovarian cancer (OC) is the highest among the different types of female reproductive system cancers. SIX homeobox 4 (SIX4), a member of the homeobox family, subfamily SIX, fulfills an important role in metastasis and angiogenesis in a variety of types of cancer. The aim of the present study was to investigate both the effects and the underlying mechanism of SIX4 on angiogenesis in OC. The Gene Expression Profiling Interactive Analysis and Encyclopedia of RNA Interactomes databases were employed to predict the expression levels of SIX4 in OC tissues, and its association with the overall survival (OS) rate of patients with OC. The expression levels of SIX4 in OC cell lines were detected by reverse transcription‑quantitative PCR (RT‑qPCR) and western blot analysis. Following silencing of SIX4, the proliferation, invasion, migration and angiogenesis of OC cells were investigated via Cell Counting Kit‑8, colony formation, wound healing, Transwell and tube formation assays. Subsequently, the levels of insulin‑like growth factor 2 mRNA binding protein 3 (IGF2BP3) in OC cell lines were detected by RT‑qPCR and western blot analysis. The ability of IGF2BP3 to bind to SIX4 mRNA was detected via an RNA immunoprecipitation assay, and the stability of SIX4 mRNA was assessed by RT‑qPCR following Actinomycin D treatment. Finally, the effects of transfection of sh‑SIX4 and overexpression of IGF2BP3 simultaneously were examined to further delineate the mechanism involved. It was revealed that SIX4 was highly expressed in OC tissues and cells, and its expression was associated with low OS rates in patients with OC. SIX4 knockdown with short hairpin RNA inhibited the proliferation, migration and invasion of cells, as well as angiogenesis. In addition, IGF2BP3 overexpression led to an improvement in the stability of SIX4 mRNA. Overexpression of IGF2BP3 also reversed the inhibitory effect of SIX4 interference on the malignant phenotypes of OC cells. Taken together, the results of the present study demonstrated that IGF2BP3‑stabilized SIX4 promoted the proliferation, metastasis and angiogenesis of SKOV3 cells.

FOXA1 Leads to Aberrant Expression of SIX4 Affecting Cervical Cancer Cell Growth and Chemoresistance

Cervical cancer (CC) is among the most prevalent cancers among female populations with high recurrence rates all over the world. Cisplatin (DDP) is the first-line treatment for multiple cancers, including CC. The main problem associated with its clinical application is drug resistance. This study is aimed at investigating the function and downstream regulation mechanism of forkhead-box A1 (FOXA1) in CC, which was verified as an oncogene in several cancers. Using GEO database and bioinformatics analysis, we identified FOXA1 as a possible oncogene in CC. Silencing of FOXA1 inhibited CC cell growth, invasion, and chemoresistance. Afterwards, the downstream gene of FOXA1 was predicted using a bioinformatics website and validated using ChIP and dual-luciferase assays. SIX4, a possible target of FOXA1, promoted CC cell malignant aggressiveness and chemoresistance. In addition, overexpression of SIX4 promoted phosphorylation of PI3K and AKT proteins and activated the PI3K/AKT signaling pathway. Further overexpression of SIX4 reversed the repressive effects of FOXA1 knockdown on CC cell growth, invasion, and chemoresistance in DDP-resistant cells. FOXA1-induced SIX4 facilitates CC progression and chemoresistance, highlighting a strong potential for FOXA1 to serve as a promising therapeutic target in CC.

Immunoregulatory mechanism studies of ginseng leaves on lung cancer based on network pharmacology and molecular docking

Panax ginseng is one of the oldest and most generally prescribed herbs in Eastern traditional medicine to treat diseases. Several studies had documented that ginseng leaves have anti-oxidative, anti-inflammatory, and anticancer properties similar to those of ginseng root. The aim of this research was to forecast of the molecular mechanism of ginseng leaves on lung cancer by molecular docking and network pharmacology so as to decipher ginseng leaves' entire mechanism. The compounds associated with ginseng leaves were searched by TCMSP. TCMSP and Swiss Target Prediction databases were used to sort out the potential targets of the main chemical components. Targets were collected from OMIM, PharmGKB, TTD, DrugBank and GeneCards which related to immunity and lung cancer. Ginseng leaves exert its lung cancer suppressive function by regulating the several signaling proteins, such as JUN, STAT3, AKT1, TNF, MAPK1, TP53. GO and KEGG analyses indicated that the immunoreaction against lung cancer by ginseng leaves might be related to response to lipopolysaccharide, response to oxidative stress, PI3K-Akt, MAPK and TNF pathway. Molecular docking analysis demonstrated that hydrogen bonding was interaction's core forms. The results of CCK8 test and qRT-PCR showed that ginseng leaves inhibit cell proliferation and regulates AKT1 and P53 expression in A549. The present study clarifies the mechanism of Ginseng leaves against lung cancer and provides evidence to support its clinical use.

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.

Reciprocal regulation of pancreatic ductal adenocarcinoma growth and molecular subtype by HNF4α and SIX1/4

OBJECTIVE

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive malignancy with a 5-year survival of less than 5%. Transcriptomic analysis has identified two clinically relevant molecular subtypes of PDAC: classical and basal-like. The classical subtype is characterised by a more favourable prognosis and better response to chemotherapy than the basal-like subtype. The classical subtype also expresses higher levels of lineage specifiers that regulate endodermal differentiation, including the nuclear receptor hepatocyte nuclear factor 4 α (HNF4α). The objective of this study is to evaluate the role of HNF4α, SIX4 and SIX1 in regulating the growth and molecular subtype of PDAC.

DESIGN

We manipulate the expression of HNF4α, SIX4 and SIX1 in multiple in vitro and in vivo PDAC models. We determine the consequences of manipulating these genes on PDAC growth, differentiation and molecular subtype using functional assays, gene expression analysis and cross-species comparisons with human datasets.

RESULTS

We show that HNF4α restrains tumour growth and drives tumour cells toward an epithelial identity. Gene expression analysis of murine models and human tumours shows that HNF4α activates expression of genes associated with the classical subtype. HNF4α also directly represses SIX4 and SIX1, two mesodermal/neuronal lineage specifiers expressed in the basal-like subtype. Finally, SIX4 and SIX1 drive proliferation and regulate differentiation in HNF4α-negative PDAC.

CONCLUSION

Our data show that HNF4α regulates the growth and molecular subtype of PDAC by multiple mechanisms, including activation of the classical gene expression programme and repression of SIX4 and SIX1, which may represent novel dependencies of the basal-like subtype.

Identification of crucial long non-coding RNAs and mRNAs along with related regulatory networks through microarray analysis in esophageal carcinoma

Esophageal carcinoma (EC) is a tremendous threat to human health and life worldwide. Long non-coding RNAs (lncRNAs) have been identified as crucial players in carcinomas including EC. An in-depth understanding on regulatory networks of lncRNAs contributes to the better management of EC. In this text, 2052 lncRNAs and 3240 mRNAs were found to be differentially expressed in 5 EC tumor tissues versus adjacent normal tissues by microarray analysis. Moreover, 297 carcinoma-related genes were screened out according to pathway and disease annotation analyses. In addition, 410 potential lncRNA-mRNA cis-regulation pairs and 395 lncRNA-mRNA trans-regulation pairs were screened out. Among these genes, 14 trans-regulated and 19 cis-regulated genes were found to be related with carcinomas. Additionally, 42 possible lncRNA-mRNA trans-regulation pairs and 26 cis-regulation pairs were found to be related with carcinomas. Also, 4 differentially expressed transcription factors in EC and lncRNAs possibly regulated by these transcription factors were screened out. Moreover, plenty of common upregulated or downregulated lncRNAs and mRNAs in EC were identified by comparative analysis for our microarray outcomes and previous high-throughput data. Furthermore, we demonstrated that ENST00000437781.1 knockdown inhibited cell proliferation and facilitated cell apoptosis by downregulating SIX homeobox 4 (SIX4) and ENST00000524987.1 knockdown had no influence on anoctamin 1 calcium activated chloride channel (ANO1) expression in EC cells. In conclusion, we identified some crucial lncRNAs and genes along with potential regulatory networks of lncRNAs/genes, deepening our understanding on pathogenesis of EC.

Upregulation of SIX4 indicates poor clinical outcome and promotes tumor growth and cell metastasis in esophageal squamous cell carcinoma

Background

The role of sine oculis homeobox 4 (SIX4) has been found in some malignant tumors. However, there have been few studies on the function of SIX4 in esophageal squamous cell carcinoma (ESCC). This study aimed to explore the regulatory mechanism of SIX4 in ESCC.

Methods

RT‐qPCR and Western blot analysis were used to measure mRNA and protein expression. The function of SIX4 was investigated using CCK‐8, colony formation, flow cytometry, wound healing and transwell assays. A mouse xenograft tumor assay was designed to perform in vivo experiments.

Results

SIX4 was upregulated in ESCC and indicated poor clinical outcomes in ESCC patients. Functionally, knockdown of SIX4 inhibited cell proliferation and induced apoptosis in ESCC. In addition, the silencing of SIX4 inhibited cell migration, invasion and EMT in ESCC. More importantly, upregulation of SIX4 could activate the PI3K/AKT pathway in ESCC cells and promote tumor growth in vivo.

Conclusions

Upregulation of SIX4 indicates poor clinical outcomes in ESCC patients and promotes tumor growth and cell metastasis in ESCC.

SIX4 promotes hepatocellular carcinoma metastasis through upregulating YAP1 and c-MET

Metastasis is the main reason for high mortality in hepatocellular carcinoma (HCC) patients and the molecular mechanism remains unclear. Therefore, it is important to elucidate the mechanism underlying HCC metastasis. Here, we report a novel role of SIX homeobox 4 (SIX4), one of the SIX gene family, in promoting HCC metastasis. The elevated expression of SIX4 was positively correlated with loss of tumor encapsulation, microvascular invasion, higher TNM stage, and poor prognosis in human HCC. SIX4 expression was an independent and significant risk factor for the recurrence and survival in HCC patients. Upregulation of SIX4 promoted HCC invasion and metastasis, whereas downregulation of SIX4 decreased HCC invasion and metastasis. SIX4 transactivated Yes1 associated transcriptional regulator (YAP1) and MET proto-oncogene, receptor tyrosine kinase (MET) expression through directly binding to their promoters. Knockdown of YAP1 and c-MET inhibited SIX4-medicated HCC metastasis, while the stable overexpression of YAP1 and c-MET reversed the decreased metastasis induced by SIX4 knockdown. Hepatocyte growth factor (HGF), the specific ligand of c-MET, upregulated SIX4 expression through ERK/NF-κB pathway. Knockdown of SIX4 significantly decreased HGF-enhanced HCC metastasis. In human HCC tissues, SIX4 expression was positively correlated with nuclear YAP1, c-MET and HGF expression. Patients with positive coexpression of SIX4/ nuclear YAP1, SIX4/c-MET or HGF/SIX4 had the poorest prognosis. Moreover, the combination treatment of YAP1 inhibitor Verteporfin and c-MET inhibitor Capmatinib significantly suppressed SIX4-mediated HCC metastasis. In conclusion, SIX4 is a prognostic biomarker in HCC patients and targeting the HGF-SIX4-c-MET positive feedback loop may provide a promising strategy for the treatment of SIX4-driven HCC metastasis.

Circular RNA-hsa-circ-0000670 promotes gastric cancer progression through the microRNA-384/SIX4 axis

Circular RNAs (circRNAs), a special type of non-coding RNA molecules, have been addressed to be implicated in gastric cancer progression. The GSE93541 and GSE83521 microarrays found hsa-circRNA-000670 (hsa-circ-0000670) as an up-regulated circRNAin gastric cancer. We mainly investigated the function and molecular mechanisms of hsa-circ-0000670 involved in gastric cancer. The expression of hsa-circ-0000670 was determined by RT-qPCR to be highly expressed in gastric cancer tissues relative to corresponding adjacent normal tissues, as well as in gastric cancer cell lines relative to normal gastric mucosal epithelial cell line. By conducting EdU, scratch test and Transwell assays, hsa-circ-000670 was found to be a tumor promoter by potentiating the proliferative, invasive and migrating capabilities of gastric cancer cells. Consistently, a tumor-promotive role of hsa-circ-000670 was validated in vivo. Dual-luciferase reporter gene and RIP assays identified the binding of hsa-circ-0000670 to microRNA-384 (miR-384) and the binding of miR-384 to sine oculis-related homeobox 4 (SIX4). The oncogenic potential of hsa-circ-0000670 in gastric cancer cells were inhibited by overexpressed miR-384. Mechanistically, SIX4 was targeted by miR-384 and was upregulated in gastric cancer. High SIX4 expression was suggested to correlate with the poor prognosis of gastric cancer patients. Additionally, silencing of SIX4 delayed tumor growth and progression, which were reversed by overexpression of hsa-circ-0000670. Taken together, hsa-circ-0000670 acts as a tumor promotor in gastric cancer progression and might be a potential target for gastric cancer treatment.

A bioinformatics investigation into the pharmacological mechanisms of javanica oil emulsion injection in non-small cell lung cancer based on network pharmacology methodologies

Background

Javanica oil emulsion injection (JOEI) is an effective therapeutic option for patients with non-small cell lung cancer (NSCLC), but its mechanisms have not been fully elucidated.

Methods

In this study, we utilized network pharmacology to systematically investigate the bioactive components and targets of JOEI, identify common targets in NSCLC, and understand and evaluate the underlying mechanism of JOEI in the treatment of NSCLC through expression level, correlation, enrichment, Cox, survival and molecular docking analyses. The results indicated that five compounds of JOEI interact with five pivotal targets (LDLR, FABP4, ABCB1, PTGS2, and SDC4) that might be strongly correlated with the JOEI-mediated treatment of NSCLC.

Results

The expression level analysis demonstrated that NSCLC tissues exhibit low expression of FABP4, ABCB1, LDLR and PTGS2 and high SDC4 expression. According to the correlation analysis, a decrease in FABP4 expression was strongly correlated with decreases in LDLR and ABCB1, and a decrease in LDLR was strongly correlated with decreased PTGS2 and increased in SDC4 expression. Cox and survival analyses showed that the survival rate of the high-risk group was significantly lower than that of the low-risk group (p = 0.00388). In the survival analysis, the area under the curve (AUC) showed that the pivotal gene model exhibited the best predictive capacity over 4 years (AUC = 0.613). Moreover, the molecular docking analysis indicated that LDLR, FABP4, ABCB1, PTGS2 and SDC4 exhibit good binding activity with the corresponding compounds.

Conclusion

In conclusion, this study predicted and verified that the mechanism of JOEI against NSCLC involves multiple targets and signaling pathways. Furthermore, this study provides candidate targets for the treatment of NSCLC, lays a good foundation for further experimental research and promotes the reasonable application of JOEI in clinical treatment.