TM4SF1 promotes the self-renewal of esophageal cancer stem-like cells and is regulated by miR-141

Multimodal AI for prediction of distant metastasis in carcinoma patients

Metastasis of cancer is directly related to death in almost all cases, however a lot is yet to be understood about this process. Despite advancements in the available radiological investigation techniques, not all cases of Distant Metastasis (DM) are diagnosed at initial clinical presentation. Also, there are currently no standard biomarkers of metastasis. Early, accurate diagnosis of DM is however crucial for clinical decision making, and planning of appropriate management strategies. Previous works have achieved little success in attempts to predict DM from either clinical, genomic, radiology, or histopathology data. In this work we attempt a multimodal approach to predict the presence of DM in cancer patients by combining gene expression data, clinical data and histopathology images. We tested a novel combination of Random Forest (RF) algorithm with an optimization technique for gene selection, and investigated if gene expression pattern in the primary tissues of three cancer types (Bladder Carcinoma, Pancreatic Adenocarcinoma, and Head and Neck Squamous Carcinoma) with DM are similar or different. Gene expression biomarkers of DM identified by our proposed method outperformed Differentially Expressed Genes (DEGs) identified by the DESeq2 software package in the task of predicting presence or absence of DM. Genes involved in DM tend to be more cancer type specific rather than general across all cancers. Our results also indicate that multimodal data is more predictive of metastasis than either of the three unimodal data tested, and genomic data provides the highest contribution by a wide margin. The results re-emphasize the importance for availability of sufficient image data when a weakly supervised training technique is used. Code is made available at: https://github.com/rit-cui-lab/Multimodal-AI-for-Prediction-of-Distant-Metastasis-in-Carcinoma-Patients.

TM4SF1 promotes esophageal squamous cell carcinoma metastasis by interacting with integrin α6

Transmembrane-4 L-six family member-1 (TM4SF1) is a member of the L6 family and functions as a signal transducer to regulate tumor cell behaviors. However, the function and mechanism of TM4SF1 in esophageal squamous cell carcinoma (ESCC) metastasis remains unclear. Here, we find that TM4SF1 expression is increased and positively correlated with clinical TNM stage, N classification, differentiation, tumor size, and poor prognosis in ESCC patients. Interestingly, we demonstrate that TM4SF1 promotes ESCC cell adhesion, spreading, migration, and invasion, but not cell proliferation, in a laminin-dependent manner by interacting with integrin α6. Mechanistically, the TM4SF1/integrin α6/FAK axis signal pathway mediates cell migration under laminin-coating condition. Inhibiting FAK or knocking down TM4SF1 can attenuate TM4SF1-mediated cell migration and lung metastasis. Clinically, the TM4SF1/integrin α6/FAK axis positively correlates with ESCC. Altogether, these findings reveal a new mechanism of TM4SF1 in promoting ESCC metastasis via binding to integrin α6 and suggest that the cross-talk between TM4SF1 and integrin α6 may serve as a therapeutic target for ESCC.

Epithelial-to-Mesenchymal Transition Mediates Resistance to Maintenance Therapy with Vinflunine in Advanced Urothelial Cell Carcinoma

Simple Summary

Platinum-based chemotherapy is the first-line treatment for advanced urothelial cell carcinoma (aUCC). After first-line treatment, we previously showed that maintenance therapy with vinflunine improves progression-free survival. However, some patients are resistant to vinflunine and the specific mechanisms of resistance in aUCC are unclear. We analyzed the genomic landscape and the biological processes potentially related to vinflunine activity and found that epithelial-to-mesenchymal transition (EMT) plays a pivotal role as a resistance mechanism. In experiments with cell lines, curcumin reversed EMT and sensitized cells to vinflunine. We suggest that EMT mediates resistance to vinflunine and that the reversion of this process could enhance the effect of vinflunine in aUCC patients.

Abstract

In the phase II MAJA trial, maintenance therapy with vinflunine resulted in longer progression-free survival compared to best supportive care in advanced urothelial cell carcinoma (aUCC) patients who did not progress after first-line platinum-based chemotherapy. However, despite an initial benefit observed in some patients, unequivocal resistance appears which underlying mechanisms are presently unknown. We have performed gene expression and functional enrichment analyses to shed light on the discovery of these underlying resistance mechanisms. Differential gene expression profile of eight patients with poor outcome and nine with good outcome to vinflunine administered in the MAJA trial were analyzed. RNA was isolated from tumor tissue and gene expression was assessed by microarray. Differential expression was determined with linear models for microarray data. Gene Set Enrichment Analysis (GSEA) was used for the functional classification of the genes. In vitro functional studies were performed using UCC cell lines. Hierarchical clustering showed a differential gene expression pattern between patients with good and poor outcome to vinflunine treatment. GSEA identified epithelial-to-mesenchymal transition (EMT) as the top negatively enriched hallmark in patients with good outcome. In vitro analyses showed that the polyphenol curcumin downregulated EMT markers and sensitized UCC cells to vinflunine. We conclude that EMT mediates resistance to vinflunine and suggest that the reversion of this process could enhance the effect of vinflunine in aUCC patients.

LOC441178 Overexpression Inhibits the Proliferation and Migration of Esophageal Carcinoma Cells via Methylation of miR-182

Background

Long noncoding RNAs (lncRNAs) have been shown to play an important role in the development and progression of esophageal carcinoma (EC). Recently, lncRNA LOC441178 was shown to be dysregulated in many cancer types; however, the role of LOC441178 in EC remains unclear.

Materials and Methods

Flow cytometry, transwell and wound healing assays were used to measure the apoptosis and migration in esophageal squamous cell carcinoma (ESCC) cells. RT-qPCR was used to detect the level of miR-182 in LOC441178-overexpressed EC cells. In addition, DNA methylation status of miR-182 promoter in LOC441178-overexpressed ESCC cells was detected by methylation-specific PCR (MSP) and bisulfite sequencing PCR.

Results

In this study, we found that LOC441178 negatively regulated miR-182 expression in ESCC cells. In addition, overexpression of LOC441178 inhibited the proliferation and migration and induced apoptosis in ESCC cells via downregulation of miR-182. Moreover, overexpression of LOC441178 markedly inhibited the phosphorylation of Akt and phosphorylation FOXO3a and increased the expression of FOXO3a in ESCC cells via downregulation of miR-182. Mechanistically, LOC441178 overexpression epigenetically suppressed miR-182 expression via DNA methylation. In vivo experiments revealed that overexpression of LOC441178 inhibited ESCC tumor growth in mouse xenograft model.

Conclusion

Collectively, our data suggested that LOC441178 overexpression epigenetically inhibited tumorigenesis of ESCC via DNA methylation of miR-182. These data indicated that the LOC441178/miR-182 axis might represent a novel therapeutic option for the treatment of ESCC.

Role of Transmembrane 4 L Six Family 1 in the Development and Progression of Cancer

Transmembrane 4 L six family 1 (TM4SF1) is a protein with four transmembrane domains that belongs to the transmembrane 4 L six family members (TM4SFs). Structurally, TM4SF1 consists of four transmembrane domains (TM1–4), N- and C-terminal intracellular domains, two extracellular domains, a smaller domain between TM1 and TM2, and a larger domain between TM3 and TM4. Within the cell, TM4SF1 is located at the cell surface where it transmits extracellular signals into the cytoplasm. TM4SF1 interacts with tetraspanins, integrin, receptor tyrosine kinases, and other proteins to form tetraspanin-enriched microdomains. This interaction affects the pro-migratory activity of the cells, and thus it plays important roles in the development and progression of cancer. TM4SF1 has been shown to be overexpressed in many malignant tumors, including gliomas; malignant melanomas; and liver, prostate, breast, pancreatic, bladder, colon, lung, gastric, ovarian, and thyroid cancers. TM4SF1 promotes the migration and invasion of cancer cells by inducing epithelial-mesenchymal transition, self-renewal ability, tumor angiogenesis, invadopodia formation, and regulating the related signaling pathway. TM4SF1 is an independent prognostic indicator and biomarker in several cancers. It also promotes drug resistance, which is a major cause of therapeutic failure. These characteristics make TM4SF1 an attractive target for antibody-based immunotherapy. Here, we review the many functions of TM4SF1 in malignant tumors, with the aim to understand the interaction between its expression and the biological behaviors of cancer and to supply a basis for exploring new therapeutic targets.

Expression of miRNA in 5-FU resistant esophageal cancer

Fluoropyrimidine plus platinum (FP) are chemotherapeutic drugs that are most frequently used to treat esophageal squamous cell carcinoma (ESCC). However, drug resistance often occurs, and the mechanisms of resistance to 5-FU is yet to be determined. The role of micro (mi)RNAs has been well established in a variety of human cancers. The aim of the present study was to investigate the expression profile of ESCC, revealing the differential expression between ESCC and 5-FU resistant ESCC. The establishment of a 5-FU resistant (5-FUR) cell lines model provides a way of analyzing the expression of miRNAs in drug resistance. The miRNA expression indicated 50 miRNAs that were upregulated in TE10-5-FUR compared with TE10, while 119 miRNAs were downregulated. The TE11-5-FUR demonstrated 140 miRNAs were upregulated compared with TE11, which exhibited 12 downregulated miRNAs. Both cell lines share the 2 candidate upregulated miRNAs (miR-146a and miR-483-5p) and 5 downregulated miRNAs (miR-34a, miR-141, miR-200b, miR-200c and miR-205). Further studies are required to analyze and evaluate the function of the miRNAs.

Apatinib induces apoptosis and autophagy via the PI3K/AKT/mTOR and MAPK/ERK signaling pathways in neuroblastoma

The clinical outcome of neuroblastoma (NB) has significantly improved in the last 30 years for patients with localized disease; however, the overall survival (OS) for patients with metastasis remains poor. Apatinib, a selective inhibitor of the vascular endothelial growth factor receptor-2 (VEGFR-2) tyrosine kinase, which was discovered to be highly associated with metastasis, has been reported to exert antitumor effects in numerous types of cancer. However, the effect of apatinib in NB remains relatively unknown. The present study aimed to investigate the antitumor effects of apatinib in NB cells in vitro. The results revealed that apatinib inhibited cell viability and colony formation, whilst inducing cell cycle arrest and the apoptosis of NB cells. Additionally, apatinib inhibited the migration and invasion of NB cells, in addition to promoting the autophagy of NB cells. Western blotting demonstrated that the protein expression levels of phosphorylated (p)-AKT, p-mTOR and p-P70S6K, and downstream molecules associated with the cell cycle and apoptosis, such as cyclin D1 and the Bcl-2/Bax ratio of NB cells, were significantly decreased following treatment with apatinib. In addition, western blotting and immunofluorescence assays identified that the expression level of microtubule-associated protein 1A/1B-light chain 3-II, which is expressed in autophagosomes, was upregulated following apatinib treatment. In conclusion, the findings of the present study suggested that apatinib may induce apoptosis and autophagy via the PI3K/AKT/mTOR and mitogen-activated protein kinase/ERK signaling pathways in NB cells. Thus, apatinib may be a potential antitumor agent for the clinical treatment of NB.

Metformin suppresses the esophageal carcinogenesis in rats treated with NMBzA through inhibiting AMPK/mTOR signaling pathway

Metformin is a widely used antidiabetic drug for the management of type 2 diabetes mellitus. Recently, epidemiological studies demonstrate that metformin has anticancer effects on esophageal squamous cell carcinoma (ESCC) and other cancers. However, the effects and potential mechanisms of metformin on ESCC remain elusive. In this study, we used N-nitroso-N-methylbenzylamine (NMBzA), a special carcinogen for esophagi, to develop a rat ESCC model, in which the carcinogenesis progression of ESCC in rat was induced and promoted. We investigated the effects of metformin on carcinogenesis of ESCC in this model. Our results revealed that metformin significantly decreased the incidence and precancerous lesions of ESCC and inhibited proliferation and promoted apoptosis of esophageal epithelial cells in rat treated with NMBzA. Moreover, metformin also increased apoptosis and inhibited migration, colony formation and tumor sphere formation of human ESCC cells in vitro. Immunohistochemistry and western blotting showed that without interfering the metabolism of NMBzA, metformin inhibited the inflammation of esophagi via reducing the expressions of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2) and interleukin-6 (IL-6). Treatment of metformin led to activation of AMP-activated protein kinase (AMPK) and attenuated signaling of the downstream molecules such as p-mTOR, p-p70S6K and cyclin D1 expression both in vivo and in vitro. Taken together, our study demonstrated that metformin suppressed the carcinogenesis of ESCC through inhibiting AMPK/mammalian target of the rapamycin (mTOR) signaling pathway, resulting in its chemopreventive effects on the carcinogenesis of ESCC.

Identification of eQTLs and sQTLs associated with meat quality in beef

BACKGROUND

Transcription has a substantial genetic control and genetic dissection of gene expression could help us understand the genetic architecture of complex phenotypes such as meat quality in cattle. The objectives of the present research were: 1) to perform eQTL and sQTL mapping analyses for meat quality traits in longissimus dorsi muscle; 2) to uncover genes whose expression is influenced by local or distant genetic variation; 3) to identify expression and splicing hot spots; and 4) to uncover genomic regions affecting the expression of multiple genes.

RESULTS

Eighty steers were selected for phenotyping, genotyping and RNA-seq evaluation. A panel of traits related to meat quality was recorded in longissimus dorsi muscle. Information on 112,042 SNPs and expression data on 8588 autosomal genes and 87,770 exons from 8467 genes were included in an expression and splicing quantitative trait loci (QTL) mapping (eQTL and sQTL, respectively). A gene, exon and isoform differential expression analysis previously carried out in this population identified 1352 genes, referred to as DEG, as explaining part of the variability associated with meat quality traits. The eQTL and sQTL mapping was performed using a linear regression model in the R package Matrix eQTL. Genotype and year of birth were included as fixed effects, and population structure was accounted for by including as a covariate the first PC from a PCA analysis on genotypic data. The identified QTLs were classified as cis or trans using 1 Mb as the maximum distance between the associated SNP and the gene being analyzed. A total of 8377 eQTLs were identified, including 75.6% trans, 10.4% cis, 12.5% DEG trans and 1.5% DEG cis; while 11,929 sQTLs were uncovered: 66.1% trans, 16.9% DEG trans, 14% cis and 3% DEG cis. Twenty-seven expression master regulators and 13 splicing master regulators were identified and were classified as membrane-associated or cytoskeletal proteins, transcription factors or DNA methylases. These genes could control the expression of other genes through cell signaling or by a direct transcriptional activation/repression mechanism.

CONCLUSION

In the present analysis, we show that eQTL and sQTL mapping makes possible positional identification of gene and isoform expression regulators.

Lost miR-141 and upregulated TM4SF1 expressions associate with poor prognosis of pancreatic cancer: regulation of EMT and angiogenesis by miR-141 and TM4SF1 via AKT

Background: Transmembrane-4-L-six-family-1 (TM4SF1) functions to regulate cell growth and mobility and TM4SF1 expression was upregulated in pancreatic cancer. This study further investigated the role of TM4SF1 in regulating pancreatic cancer epithelial-mesenchymal transition (EMT) and angiogenesis and the underlying molecular events.Methods: Tissue specimens were collected from 90 pancreatic cancer patients for immunohistochemical and qRT-PCR analysis of miR-141 and TM4SF1 levels, respectively. Pancreatic cancer cell lines were used for in vitro assays, while nude mice were used for the in vivo assay.Results: TM4SF1 expression was upregulated, whereas miR-141 expression was lost in pancreatic cancer tissues, both of which was associated with advanced clinicopathological features and poor survival of pancreatic cancer patients. Furthermore, miR-141 was able to target and reduce TM4SF1 expression in pancreatic cancer cells and miR-141 expression inhibited pancreatic cancer cell EMT in vitro and Matrigel plug angiogenesis and lung metastasis in nude mice. At the gene level, miR-141 directly targeted and reduced TM4SF1 expression and in turn induced E-cadherin expression and reduced VEGF-A expression by suppressing activation of the AKT signaling pathway.Conclusions: This study demonstrated that upregulated TM4SF1 and lost miR-141 expression were associated with advanced clinicopathological features and poor survival of pancreatic cancer patients. Lost miR-141 expression but induced TM4SF1 expression altered expression of VEGF-A and E-cadherin and promoted pancreatic cancer cell EMT and angiogenesis via the AKT signaling pathway, suggesting that targeting of miR-141 and TM4SF1 may be a potential therapeutic strategy to control pancreatic cancer.

TM4SF1, a binding protein of DVL2 in hepatocellular carcinoma, positively regulates beta-catenin/TCF signalling

The interaction between Axin and DVL2 is critical for the breaking down of the beta‐catenin destruction complex and the activation of the Wnt/beta‐catenin cascade. However, this biological process remains poorly understood. In the present study, TM4SF1 was identified as the interacting partner of DVL2 and positively regulated as Wnt/beta‐catenin signalling by strengthening the DVL2‐Axin interaction. The expression levels of TM4SF1 were elevated in hepatocellular carcinoma (HCC) and were induced by Kras signalling. The overexpression of TM4SF1 promoted the growth and motility of HCC cells, and up‐regulated the target genes (Axin2 and cyclin D1). The down‐regulation of TM4SF1 impaired the capability of HCC cells for growth, migration and metastasis. In addition, the down‐regulation of TM4SF1 promoted the ubiquitination of beta‐catenin. In summary, these results reveal the oncogenic functions of TM4SF1 in HCC progression and suggest that TM4SF1 might be a target for treatment.

TM4SF1 is a potential target for anti-invasion and metastasis in ovarian cancer

BACKGROUND

Patients with ovarian cancer commonly have a poor prognosis, owing to its invasiveness and distant metastasis. Studies have found TM4SF1 participates in regulating tumor cell invasion and migration. Therefore, it is expected to become a target for anti-invasion and metastasis in ovarian cancer.

METHODS

The expression of TM4SF1 in normal ovarian epithelial tissues, benign ovarian tumor tissues, primary foci of epithelial ovarian cancer and the matched lymph mode metastatic foci was detected using immunohistochemistry to analyze its association with prognosis. The expression of TM4SF1 in HO8910PM, SKOV3 was inhibited using RNAi, and the growth, proliferation, migration, invasion abilities of HO8910PM and SKOV3 cells and the growth of xenograft tumors in nude mice were examined.

RESULTS

(1) The positive expression rate of TM4SF1 protein in epithelial ovarian cancer tissues (90.90%) was higher than that in benign ovarian tumor tissues (65.22%) and normal ovarian epithelial tissues (31.25%), and both differences were significant (P < 0.05). The expression of TM4SF1 protein was positive in all metastatic lymph node foci and matched primary foci (100%). (2) The level of TM4SF1 protein expression was positively correlated with the International Federation of Gynecology and Obstetrics (FIGO) stage and histological grade. However, The positive TM4SF1 protein expression was not an independent factor of prognosis (P > 0.05). (3) Silencing TM4SF1 expression did not affect growth, proliferation, or cell cycle distribution but inhibited the migration and invasion abilities of HO8910PM and SKOV3 cells. Silencing TM4SF1 expression inhibited the growth of xenograft tumors in nude mice.

CONCLUSION

TM4SF1 is a potential target for anti-invasion and metastasis in ovarian cancer.

miR-30 Family Reduction Maintains Self-Renewal and Promotes Tumorigenesis in NSCLC-Initiating Cells by Targeting Oncogene TM4SF1

Increasing evidence indicates that tumor-initiating cells (TICs) are responsible for the occurrence, development, recurrence, and development of the drug resistance of cancer. MicroRNA (miRNA) plays a significant functional role by directly regulating targets of TIC-triggered non-small-cell lung cancer (NSCLC), but little is known about the function of the miR-30 family in TICs. In this study, we found the miR-30 family to be downregulated during the spheroid formation of NSCLC cells, and patients with lower miR-30a/c expression had shorter overall survival (OS) and progression-free survival (PFS). Moreover, transmembrane 4 super family member 1 (TM4SF1) was confirmed to be a direct target of miR-30a/c. Concomitant low expression of miR-30a/c and high expression of TM4SF1 correlated with a shorter median OS and PFS in NSCLC patients. miR-30a/c significantly inhibited stem-like characteristics in vitro and in vivo via suppression of its target gene TM4SF1, and then it inhibited the activity of the mTOR/AKT-signaling pathway. Thus, our data provide the first evidence that TM4SF1 is a direct target of miR-30a/c and miR-30a/c inhibits the stemness and proliferation of NSCLC cells by targeting TM4SF1, suggesting that miR-30a/c and TM4SF1 may be useful as tumor biomarkers for the diagnosis and treatment of NSCLC patients.

TM4SF1 inhibits apoptosis and promotes proliferation, migration and invasion in human gastric cancer cells

Gastric cancer (GC) is associated with poor patient prognosis, and so it crucial to investigate the molecular mechanisms underlying the progression of GC. The aim of the present study was to investigate the role of transmembrane-4 L6 family member 1 (TM4SF1) in the progression of GC. TM4SF1 small interfering RNA (siRNA) and TM4SF1-expressing plasmids were employed to regulate TM4SF1 expression. In vitro experiments were performed to determine the effect of TM4SF1 on the expression of apoptosis-associated molecules and determine the role of TM4SF1 in apoptosis, proliferation, migration and invasion using human GC cell lines MGC803 and MKN45. The data of the present study demonstrated that TM4SF1 may regulate the expression of apoptosis-associated molecules at the mRNA and protein levels. TM4SF1 silencing reduced B-cell lymphoma 2 (Bcl2) expression, whilst caspase-3 and Bcl2-associated X expression increased, and upregulating TM4SF1 reversed these changes in GC cells. Furthermore, TM4SF1 knockdown promoted apoptosis while inhibiting the proliferation, migration and invasion of GC cells. Rescue experiments demonstrated that TM4SF1 upregulation reversed the changes induced by transfection with TM4SF1 siRNA. In summary, TM4SF1 is an anti-apoptosis protein associated with the progression of GC. Additional in vivo experiments and clinical trials are required to confirm the possible use of TM4SF1 in tumor therapy.

microRNA-520f inhibits hepatocellular carcinoma cell proliferation and invasion by targeting TM4SF1

microRNAs (miRNAs) are reported to play crucial roles in tumorigenesis. Dysregulation of miR-520f has been implicated to be involved in several cancer progressions. However, the biological functions of miR520f in hepatocellular carcinoma (HCC) remain unclear. Thus, the molecular mechanism underlying miR-520f on HCC development was investigated in this study. Here, we found that miR-520f was remarkably down-regulated in human HCC samples and cell lines compared to paired normal tissues and cell lines as detected by qRT-PCR. Furthermore, the deregulated miR-520f was strongly associated with larger tumor size, advanced TNM stage, and metastasis in HCC patients. Functional investigations revealed that overexpression of miR-520f significantly suppressed cell proliferation, invasion and migration, caused cell cycle arrested at G0/G1 phase, and promoted cell apoptosis in HCC cells according to MTT, colony formation, transwell, and flow cytometry assays, respectively, whereas, downregulation of miR-520f exhibited inverse effects. Transmembrane-4 L-Six family member-1 (TM4SF1) was identified as a direct target of miR-520f, and an inverse relationship was found between miR-520f and TM4SF1 mRNA levels in HCC specimens. Rescue experiments suggested that restoration of TM4SF1 partially abolished miR-520f-meidated cell proliferation and invasion inhibition in HCC cells through regulating P13K/AKT and p38 MAPK signaling pathways. In conclusion, these data indicated that miR-520f acted as tumor suppressor in HCC proliferation and invasion by targeting TM4SF1, which might provide potential therapeutic evidence for HCC patients.

DNMT1 ablation suppresses tumorigenesis by inhibiting the self-renewal of esophageal cancer stem cells

Cancer stem cells (CSCs) have been isolated from many tumors and considered as the main reason of cancer recurrence and metastasis. DNA methyltransferase 1 (DNMT1) mediates DNA methylation and plays an important role in CSCs maintenance. However, the function of DNMT1 in CSCs of esophageal squamous cell carcinoma (ESCC) remains unclear. In this study, we examined the role of DNMT1 in regulating self-renewal in CSCs of ESCC. We found a high expression of DNMT1 in both side population (SP) cells and sphere formation cells that represented as substitutes for CSCs in KYSE150 and EC109 ESCC cell lines. We performed the knockdown of DNMT1 using lentivirus-mediated RNA interference (RNAi) methods. We revealed that ablation of DNMT1 resulted in the numbers and self-renewal abilities of CSCs refrained significantly in ESCC cells. As a result of the CSCs inhibition, the malignant phenotypes such as cell proliferation, colony formation, migration and drug resistance abilities were dramatically inhibited in ESCC cells. Treatment of 5-aza-2'-deoxycytidine (5-aza-dC), a DNMT inhibitor, also resulted in the inhibition of CSCs and malignant profiles in ESCC cells. Our findings also provided the first evidence that 5-aza-dC inhibited the colony and sphere formation of CSCs. Thus, our results indicated that DNMT1 was important for the self-renewal maintenance of CSCs in ESCC, and 5-aza-dC could be a potential therapy for the CSCs of ESCC.

Osteopontin production by TM4SF4 signaling drives a positive feedback autocrine loop with the STAT3 pathway to maintain cancer stem cell-like properties in lung cancer cells

Transmembrane 4 L6 family proteins have been known to promote cancer. In this study, we demonstrated that transmembrane 4 L6 family member 4 (TM4SF4), which is induced by γ-radiation in non-small cell lung cancer (NSCLC) cells, is involved in epithelial-to-mesenchymal transition (EMT) and cancer stem cell (CSC) properties of NSCLC through the regulation of osteopontin (OPN). Forced TM4SF4 overexpression in A549 cells increased the secretion of OPN, which activates CD44 or integrin signaling and thus maintains EMT-associated CSC-like properties. OPN, known as a downstream target of β-catenin/T-cell factor 4 (TCF-4), was induced by up-regulated β-catenin via TM4SF4-driven phosphorylation of glycogen synthase kinase 3b (GSK3β). TCF4 complexed to promoter regions of OPN in TM4SF4-overexpressing A549 cells was also confirmed by chromatin immunoprecipitation. Knockout of either β-catenin or TCF4-suppressed OPN expression, demonstrating that both factors are essential for OPN expression in NSCLC cells. OPN secreted by TM4SF4/GSK3β/β-catenin signaling activated the JAK2/STAT3 or FAK/STAT3 pathway, which also up-regulates OPN expression in an autocrine manner and consequently maintains the self-renewal and metastatic capacity of cancer cells. Neutralizing antibody to OPN blocked the autocrine activation of OPN expression, consequently weakened the metastatic and self-renewal capacity of cancer cells. Collectively, our findings indicate that TM4SF4-triggered OPN expression is involved in the persistent reinforcement of EMT or cancer stemness by creating a positive feedback autocrine loop with JAK2/STAT3 or FAK/STAT3 pathways.