EMT and stemness: flexible processes tuned by alternative splicing in development and cancer progression. Mol Cancer. 2017;16:8. [PMID: 28137272 PMCID: PMC5282733 DOI: 10.1186/s12943-016-0579-2]

Molecular Biology and Evolution of Cancer: From Discovery to Action

Cancer progression is an evolutionary process. During this process, evolving cancer cell populations encounter restrictive ecological niches within the body, such as the primary tumor, circulatory system, and diverse metastatic sites. Efforts to prevent or delay cancer evolution-and progression-require a deep understanding of the underlying molecular evolutionary processes. Herein we discuss a suite of concepts and tools from evolutionary and ecological theory that can inform cancer biology in new and meaningful ways. We also highlight current challenges to applying these concepts, and propose ways in which incorporating these concepts could identify new therapeutic modes and vulnerabilities in cancer.

HMGA Genes and Proteins in Development and Evolution

HMGA (high mobility group A) (HMGA1 and HMGA2) are small non-histone proteins that can bind DNA and modify chromatin state, thus modulating the accessibility of regulatory factors to the DNA and contributing to the overall panorama of gene expression tuning. In general, they are abundantly expressed during embryogenesis, but are downregulated in the adult differentiated tissues. In the present review, we summarize some aspects of their role during development, also dealing with relevant studies that have shed light on their functioning in cell biology and with emerging possible involvement of HMGA1 and HMGA2 in evolutionary biology.

Up-regulation of RNA Binding Proteins Contributes to Folate Deficiency-Induced Neural Crest Cells Dysfunction

Folate deficiency has long been associated with the abnormal development of the neural crest cells (NCCs) and neural tube defects (NTDs). RNA binding proteins (RBPs) also play important roles in the normal neural crest development and neural tube formation. Nevertheless, the causative mechanism by which folate status influences human NCCs development and the RBPs functions remains unknown. In this study, we differentiated H9 human embryonic stem cells into neural crest cells (H9-NCCs) and then constructed three folic acid (FA) deficiency (FAD) H9-NCCs models in vitro. Decreased viability, impaired migration and promoted apoptosis of H9-NCCs were observed in three FAD H9-NCCs models. In addition, we showed that three RBPs, namely, hnRNPC, LARP6 and RCAN2, were up-regulated both in the FAD H9-NCC models in vitro and in the FAD mouse model in vivo. Knocking down of these three RBPs increased the H9-NCC viability and RCAN2 knockdown further promoted H9-NCC migration under FAD conditions. In normal culture condition, overexpression of RCAN2 and HnRNPC did not affect viabilities and migration of H9-NCCs while overexpression of LARP6 reduced the H9-NCC viability. Our findings demonstrate important regulatory effects of RBPs underlying FAD-induced impaired function of NCCs.

An Intricate Connection between Alternative Splicing and Phenotypic Plasticity in Development and Cancer

During tumor progression, hypoxia, nutrient deprivation or changes in the extracellular environment (i.e., induced by anti-cancer drugs) elicit adaptive responses in cancer cells. Cellular plasticity increases the chance that tumor cells may survive in a challenging microenvironment, acquire new mechanisms of resistance to conventional drugs, and spread to distant sites. Re-activation of stem pathways appears as a significant cause of cellular plasticity because it promotes the acquisition of stem-like properties through a profound phenotypic reprogramming of cancer cells. In addition, it is a major contributor to tumor heterogeneity, depending on the coexistence of phenotypically distinct subpopulations in the same tumor bulk. Several cellular mechanisms may drive this fundamental change, in particular, high-throughput sequencing technologies revealed a key role for alternative splicing (AS). Effectively, AS is one of the most important pre-mRNA processes that increases the diversity of transcriptome and proteome in a tissue- and development-dependent manner. Moreover, defective AS has been associated with several human diseases. However, its role in cancer cell plasticity and tumor heterogeneity remains unclear. Therefore, unravelling the intricate relationship between AS and the maintenance of a stem-like phenotype may explain molecular mechanisms underlying cancer cell plasticity and improve cancer diagnosis and treatment.

IM-12 activates the Wnt-β-catenin signaling pathway and attenuates rtPA-induced hemorrhagic transformation in rats after acute ischemic stroke

Hemorrhagic transformation (HT) is a devastating complication for patients with acute ischemic stroke (AIS) who are treated with tissue plasminogen activator (tPA). HT is associated with high morbidity and mortality, but no effective treatments are currently available to reduce the risk of HT. Therefore, methods to prevent HT are urgently needed. In this study, we used IM-12, an inhibitor of glycogen synthase kinase 3β (GSK-3β), to evaluate the role of the Wnt-β-catenin signaling pathway in recombinant tPA (rtPA)-induced HT. Sprague-Dawley rats were subjected to a middle cerebral artery occlusion (MCAO) model of ischemic stroke, and then were either administered rtPA, rtPA combined with IM-12, or the vehicle at 4 h after stroke was induced. Our results indicate that rats subjected to HT had more severe neurological deficits, brain edema, and blood-brain barrier (BBB) breakdown, and had a greater infarction volume than the control group. Rats treated with IM-12 had improved outcomes compared with those of rats treated with rtPA alone. Moreover, IM-12 increased the protein expression of β-catenin and downstream proteins while suppressing the expression of GSK-3β. These results suggest that IM-12 reduces rtPA-induced HT and attenuates BBB disruption, possibly through activation of the Wnt-β-catenin signaling pathway, and provides a potential therapeutic strategy for preventing tPA-induced HT after AIS.

Promising Prognosis Marker Candidates on the Status of Epithelial-Mesenchymal Transition and Glioma Stem Cells in Glioblastoma

Multivariable analyses of global expression profiling are valid indicators of the prognosis of various diseases including brain cancers. To identify the candidates for markers of prognosis of glioblastoma, we performed multivariable analyses on the status of epithelial (EPI)-mesenchymal (MES) transition (EMT), glioma (GLI) stem cells (GSCs), molecular target therapy (MTT), and potential glioma biomarkers (PGBs) using the expression data and clinical information from patients. Random forest survival and Cox proportional hazards regression analyses indicated significant variable values for DSG3, CLDN1, CDH11, FN1, HDAC3/7, PTEN, L1CAM, OLIG2, TIMP4, IGFBP2, and GFAP. The analyses also comprised prognosis prediction formulae that could distinguish between the survival curves of the glioblastoma patients. In addition to the genes mentioned above, HDAC1, FLT1, EGFR, MGMT, PGF, STAT3, SIRT1, and GADD45A constituted complex genetic interaction networks. The calculated status scores obtained by principal component analysis indicated that GLI genes covered the status of EPI, GSC, and MTT-related genes. Moreover, survival tree analyses indicated that MES^high, MES^highGLI^low, GSC^highGLI^low, MES^highMTT^low, and PGB^high showed poor prognoses and MES^middle, GSC^low, and PGB^low showed good prognoses, suggesting that enhanced EMT and GSC are associated with poor survival and that lower expression of EPI markers and the pre-stages of EMT are relatively less malignant in glioblastoma. These results demonstrate that the assessment of EMT and GSC enables the prediction of the prognosis of glioblastoma that would help develop novel therapeutics and de novo marker candidates for the prognoses of glioblastoma.

Hypoxia induced Sonic Hedgehog signaling regulates cancer stemness, epithelial-to-mesenchymal transition and invasion in cholangiocarcinoma

Aberrant activation of Sonic Hedgehog (SHH) pathway has been implicated in a variety of cancers including cholangiocarcinoma (CC); however, the influencing factors are still unknown. Additionally, intratumoral hypoxia is known to contribute towards therapeutic resistance through modulatory effects on various pathways. In this study, we investigated the relationship between hypoxia and SHH pathway activation and the effect of this interplay on cancer stemness and epithelial-to- mesenchymal transition (EMT) during cholangiocarcinogenesis. Hypoxia promoted SHH pathway activation, evidenced by upregulated SHH and SMO levels, and enhanced glioma-associated oncogene homolog 1 (GLI1) nuclear translocation; whereas silencing of HIF-1α impaired SHH upregulation. Hypoxia also enhanced the expression of cancer stem cell (CSC) transcription factors (NANOG, Oct4, SOX2), CD133 and EMT markers (N-cadherin, Vimentin), thereby supporting invasion. Cyclopamine treatment suppressed hypoxia induced SHH pathway activation, consequently reducing invasiveness by downregulating the expression of CSC transcription factors, CD133 and EMT. Cyclopamine induced apoptosis in CC cells under hypoxia, suggesting that hypoxia induced activation of SHH pathway has modulatory effects on CC progression. Therefore, SHH signaling is proposed as a target for CC treatment, which is refractory to standard chemotherapy.

CDK4/6 inhibition in cancer: the cell cycle splicing connection

Cyclin-dependent kinase −4 and −6 (CDK4/6) inhibitors are currently being assessed in clinical trials for the treatment of many cancers including melanoma. While investigating the mechanisms of CDK4/6 inhibitor resistance in melanoma, we uncovered a mechanism of action of these inhibitors in regulating the expression of both the mouse double minute 4 (MDM4) oncogene and tumor protein p53 (TP53).

Extracellular Matrix Alterations in Metastatic Processes

The extracellular matrix (ECM) is a complex network of extracellular-secreted macromolecules, such as collagen, enzymes and glycoproteins, whose main functions deal with structural scaffolding and biochemical support of cells and tissues. ECM homeostasis is essential for organ development and functioning under physiological conditions, while its sustained modification or dysregulation can result in pathological conditions. During cancer progression, epithelial tumor cells may undergo epithelial-to-mesenchymal transition (EMT), a morphological and functional remodeling, that deeply alters tumor cell features, leading to loss of epithelial markers (i.e., E-cadherin), changes in cell polarity and intercellular junctions and increase of mesenchymal markers (i.e., N-cadherin, fibronectin and vimentin). This process enhances cancer cell detachment from the original tumor mass and invasiveness, which are necessary for metastasis onset, thus allowing cancer cells to enter the bloodstream or lymphatic flow and colonize distant sites. The mechanisms that lead to development of metastases in specific sites are still largely obscure but modifications occurring in target tissue ECM are being intensively studied. Matrix metalloproteases and several adhesion receptors, among which integrins play a key role, are involved in metastasis-linked ECM modifications. In addition, cells involved in the metastatic niche formation, like cancer associated fibroblasts (CAF) and tumor associated macrophages (TAM), have been found to play crucial roles in ECM alterations aimed at promoting cancer cells adhesion and growth. In this review we focus on molecular mechanisms of ECM modifications occurring during cancer progression and metastatic dissemination to distant sites, with special attention to lung, liver and bone. Moreover, the functional role of cells forming the tumor niche will also be reviewed in light of the most recent findings.

Genome-wide profiling of prognosis-related alternative splicing signatures in sarcoma

BACKGROUND

Sarcomas (SARCs) are rare malignant tumors with poor prognosis. Increasing evidence has suggested that aberrant alternative splicing (AS) is strongly associated with tumor initiation and progression. We considered whether survival-related AS events might serve as prognosis predictors and underlying targeted molecules in SARC treatment.

METHODS

RNA-Seq data of the SARC cohort were downloaded from The Cancer Genome Atlas (TCGA) database. Survival-related AS events were selected by univariate and multivariate Cox regression analyses. Metascape was used for constructing a gene interaction network and performing functional enrichment analysis. Then, prognosis predictors were established based on statistically significant survival-related AS events and evaluated by receiver operator characteristic (ROC) curve analysis. Finally, the potential regulatory network was analyzed via Pearson's correlation between survival-related AS events and splicing factors (SFs).

RESULTS

A total of 3,610 AS events and 2,291 genes were found to be prognosis-related in 261 SARC samples. The focal adhesion pathway was identified as the most critical molecular mechanism corresponding to poor prognosis. Notably, several prognosis predictors based on survival-related AS events showed excellent performance in prognosis prediction. The area under the curve of the ROC of the risk score was 0.85 in the integrated predictor. The splicing network proved complicated regulation between prognosis-related SFs and AS events. Also, driver gene mutations were significantly associated with AS in SARC patients.

CONCLUSIONS

Survival-related AS events may become ideal indictors for the prognosis prediction of SARCs. Corresponding splicing regulatory mechanisms are worth further exploration.

Survival-Associated Alternative Messenger RNA Splicing Signatures in Pancreatic Ductal Adenocarcinoma: A Study Based on RNA-Sequencing Data

Multiple studies have shown that cancer-specific alternative splicing (AS) alterations are associated with clinical outcome. In this study, we aimed to profile prognostic AS signatures for pancreatic ductal adenocarcinoma (PDAC). We integrated the percent-spliced-in (PSI) data of AS in 140 PDAC patients based on the Cancer Genome Atlas (TCGA) dataset. We identified overall survival (OS)-associated AS events using univariate Cox regression analysis. Then, prognostic AS signatures were constructed for OS and chemoresistance prediction using the least absolute shrinkage and selection operator (LASSO) method. We also analyzed splicing factors (SFs) regulatory networks by Pearson's correlation. We detected 677 OS-related AS events in 485 genes by profiling 10,354 AS events obtained from 140 PDAC patients. Gene functional enrichment analysis demonstrated the pathways enriched by survival-associated AS. The AS signatures constructed with significant survival-associated AS events revealed high performance in predicting PDAC survival and gemcitabine chemoresistance. The area under the receiver operator characteristic curve was 0.937 in training cohort and 0.748 in validation cohort at 2000 days of OS. Furthermore, we identified prognostic SFs (e.g., ESRP1 and HNRNPC) to build the AS regulatory network. We constructed AS signatures for OS and gemcitabine chemoresistance in PDAC patients, which may provide clues for further experiment-based mechanism study.

Serine/Arginine-Rich Splicing Factor 3 Modulates the Alternative Splicing of Cytoplasmic Polyadenylation Element Binding Protein 2

Triple negative breast cancer (TNBC) has an unusually low 5-year survival rate linked to higher metastatic rates. Our laboratory recently delineated a role for the alternative RNA splicing (AS) of cytoplasmic polyadenylation element binding protein 2 (CPEB2), via inclusion/exclusion of exon 4, in the metastasis of TNBC. In these studies, the mechanism governing the inclusion/exclusion of exon 4 was examined. Specifically, the RNA trans-factor, SRSF3, was found to be explicitly associated with CPEB2 exon 4. A SRSF3 consensus sequence was identified in exon 4, and mutation of this sequence abolished the association of SRSF3. The expression of SRSF3 was upregulated in TNBC cells upon the acquisition of anoikis resistance correlating with a reduction in the CPEB2A/B ratio. Importantly, downregulation of SRSF3 in these cells by siRNA induced the exclusion of exon 4 in cells increasing the ratio of CPEB2A (exon 4 excluded) to CPEB2B (exon 4 included). Downregulation of SRSF3 also reversed the CPEB2A/B ratio of a wild-type CPEB2 exon 4 minigene and endogenous CPEB2 pre-mRNA, but not a mutant CPEB2 minigene with the SRSF3 RNA cis-element ablated. SRSF3 downregulation ablated the anoikis resistance of TNBC cells, which was "rescued" by ectopic expression of CPEB2B. Finally, analysis of The Cancer Genome Atlas database showed a positive relationship between SRSF3 expression and lower CPEB2A/B ratios in aggressive breast cancers. IMPLICATIONS: These findings demonstrate that SRSF3 modulates CPEB2 AS to induce the expression of the CPEB2B isoform that drives TNBC phenotypes correlating with aggressive human breast cancer. VISUAL OVERVIEW: http://mcr.aacrjournals.org/content/molcanres/17/9/1920/F1.large.jpg.

Emerging insights into the biology of metastasis: A review article

Metastasis means the dissemination of the cancer cells from one organ to another which is not directly connected to the primary site. Metastasis has a crucial role in the prognosis of cancer patients. A few theories, different types of cell and several molecular pathways have been proposed to explain the mechanism of metastasis. In this work, the related articles in the limited period of time, 2000-mid -2018 were reviewed, through search in PubMed, Google Scholar and Scopus database. The articles published in the last two decades related to the biology of cancer metastasis were selected and the most important factors were discussed. Metastasis is critical factor to predict survival in patients with advanced cancer and prognosis determines the treatment plan. Many different cell types and various signaling pathways control the metastatic process. Metastasis is a multistep process. Many signaling pathways and molecules are involved in metastasis. Increasing knowledge about the mechanism of metastasis can help in finding the promising targets of cancer therapy.

Gold Nanoparticles sensitize pancreatic cancer cells to gemcitabine

Pancreatic ductal adenocarcinoma (PDAC) is one of the deadliest solid cancers with dismal prognosis. Several mechanisms that are mainly responsible for aggressiveness and therapy resistance of PDAC cells include epithelial to mesenchymal transition (EMT), stemness and Mitogen Activated Protein Kinase (MAPK) signaling. Strategies that inhibit these mechanisms are critically important to improve therapeutic outcome in PDAC. In the current study, we wanted to investigate whether gold nanoparticles (AuNPs) could sensitize pancreatic cancer cells to the chemotherapeutic agent gemcitabine. We demonstrated that treatment with AuNPs of 20 nm diameter inhibited migration and colony forming ability of pancreatic cancer cells. Pre-treatment with AuNPs sensitized pancreatic cancer cells to gemcitabine in both viability and colony forming assays. Mechanistically, pre-treatment of pancreatic cancer cells with AuNPs decreased gemcitabine induced EMT, stemness and MAPK activation. Taken together, these findings suggest that AuNPs could be considered as a potential agent to sensitize pancreatic cancer cells to gemcitabine.

RBM47-regulated alternative splicing of TJP1 promotes actin stress fiber assembly during epithelial-to-mesenchymal transition

Morphological and functional changes in cells during the epithelial-mesenchymal transition (EMT) process are known to be regulated by alternative splicing. However, only a few splicing factors involved in EMT have been reported and their underlying mechanisms remain largely unknown. Here, we showed that an isoform of tight junction protein 1 (TJP1) lacking exon 20 (TJP1-α-) is predominantly expressed in tumor tissues and in A549 cells during transforming growth factor-β (TGF-β)-induced EMT. RBM47 promoted the inclusion of exon 20 of TJP1, the alternative exon encoding the α-domain, by which RBM47 recognizes to (U)GCAUG in the downstream intronic region of exon 20. We also found that the first RNA recognition motif (RRM) domain of RBM47 is critical in the regulation of alternative splicing and its recognition to pre-mRNA of TJP1. Furthermore, we demonstrated that the TJP1-α- isoform enhances the assembly of actin stress fibers, thereby promoting cellular migration in a wound healing assay. Our results suggest the regulatory mechanism for the alternative splicing of TJP1 pre-mRNA by RBM47 during EMT, providing a basis for studies related to the modulation of EMT via alternative splicing.

Presence and role of stem cells in ovarian cancer

Ovarian cancer is the deadliest gynecological malignancy. It is typically diagnosed at advanced stages of the disease, with metastatic sites disseminated widely within the abdominal cavity. Ovarian cancer treatment is challenging due to high disease recurrence and further complicated pursuant to acquired chemoresistance. Cancer stem cell (CSC) theory proposes that both tumor development and progression are driven by undifferentiated stem cells capable of self-renewal and tumor-initiation. The most recent evidence revealed that CSCs in terms of ovarian cancer are not only responsible for primary tumor growth, metastasis and relapse of disease, but also for the development of chemoresistance. As the elimination of this cell population is critical for increasing treatment success, a deeper understanding of ovarian CSCs pathobiology, including epithelial-mesenchymal transition, signaling pathways and tumor microenvironment, is needed. Finally, before introducing new therapeutic agents for ovarian cancer, targeting CSCs, accurate identification of different ovarian stem cell subpopulations, including the very small embryonic-like stem cells suggested as progenitors, is necessary. To these ends, reliable markers of ovarian CSCs should be identified. In this review, we present the current knowledge and a critical discussion concerning ovarian CSCs and their clinical role.

SARNP, a participant in mRNA splicing and export, negatively regulates E-cadherin expression via interaction with pinin

Triple-negative breast cancer (TNBC) is associated with a high mortality rate, which is related to the insufficient number of appropriate biomarkers and targets. Therefore, there is an urgent need to discover appropriate biomarkers and targets for TNBC. SARNP (Hcc-1 and CIP29) is highly expressed in several cancers. It binds to UAP56, an RNA helicase component of the TREX complex in messenger RNA (mRNA) splicing and export. However, the role of SARNP in mRNA splicing and export and in the progression of breast cancer, especially of TNBC, remains unknown. Therefore, we examined the role of SARNP in mRNA splicing and export and progression of TNBC. We confirmed that SARNP binds to UAP56 and Aly and that SARNP overexpression enhances mRNA splicing, whereas its knockdown suppressed mRNA export. The SARNP overexpression induced the proliferation of MCF7 cells, whereas its knockdown induced E-cadherin expression and downregulated vimentin and N-cadherin expressions in SK-BR-3 and MDA-MB-231 cells. SARNP downregulates E-cadherin expression by interaction with pinin. Mice injected with MDA-MB-231_shSARNP cells exhibited a significant reduction in tumor growth and lung metastasis compared with those injected with MDA-MB-231_shCon cells in vivo. These findings suggested that SARNP is involved in mRNA splicing and export. SARNP maintains mesenchymal phenotype by escaping from inhibitory interaction with pinin leading to the downregulation of E-cadherin expression.

The Multifaceted S100A4 Protein in Cancer and Inflammation

The metastasis-promoting S100A4 protein, a member of the S100 family, has recently been discovered as a potent factor implicated in various inflammation-associated diseases. S100A4 is involved in a range of biological functions such as angiogenesis, cell differentiation, apoptosis, motility, and invasion. Moreover, S100A4 is also a potent trigger of inflammatory processes and induces the release of cytokines and growth factors under different pathological conditions.Indeed, the release of S100A4 upon stress and mainly its pro-inflammatory role emerges as the most decisive activity in disease development, such as rheumatoid arthritis (RA), systemic sclerosis (SSc) allergy, psoriasis, and cancer. In the scope of this review, we will focus on the role of S100A4 as a mediator of pro-inflammatory pathways and its associated biological processes involved in the pathogenesis of various human noncommunicable diseases (NCDs) including cancer.

Inhibition of PI3K/Akt/mTOR signaling pathway alleviates ovarian cancer chemoresistance through reversing epithelial-mesenchymal transition and decreasing cancer stem cell marker expression

Background

Ovarian cancer is the most common malignant tumor of the female reproductive tract. Chemoresistance is a major challenge for current ovarian cancer therapy. However, the mechanism underlying epithelial ovarian cancer (EOC) chemoresistance is not completely uncovered. The phosphatidylinositol-3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) signaling is an important intracellular pathway in regulating cell cycle, quiescence, and proliferation. The aim of this study is to investigate the role of PI3K/Akt/mTOR signaling pathway and its association with epithelial-mesenchymal transition (EMT) and cancer stem cell (CSC) marker expression in EOC chemoresistance.

Methods

The expressions of EMT and CSC markers were detected by immunofluorescence, western blot, and quantitative real-time PCR. BEZ235, a dual PI3K/mTOR inhibitor, was employed to investigate the role of PI3K/Akt/ mTOR signaling in regulating EMT and CSC marker expression. Students’ t test and one-way ANOVA with Tukey’s post-hoc test were used to compare the data from different groups.

Results

We found that EMT and CSC marker expression were significantly enhanced in chemoresistant EOC cells, which was accompanied by the activation of PI3K/Akt/mTOR signaling. Compared with single cisplatin treatment, combined treatment with BEZ235 and cisplatin significantly disrupted the colony formation ability, induced higher ROS level and more apoptosis in chemoresistant EOC cells. Furthermore, the combination approach effectively inhibited PI3K/Akt/mTOR signaling pathway, reversed EMT, and decreased CSC marker expression in chemoresistant EOC cells compared with cisplatin mono-treatment.

Conclusions

Our results first demonstrate that EMT and enhanced CSC marker expression triggered by activated PI3K/Akt/mTOR signaling are involved in the chemoresistance of EOC, and BEZ235 in combination with cisplatin might be a promising treatment option to reverse EOC chemoresistance.

Electronic supplementary material

The online version of this article (10.1186/s12885-019-5824-9) contains supplementary material, which is available to authorized users.

Nalbuphine suppresses breast cancer stem-like properties and epithelial-mesenchymal transition via the AKT-NFκB signaling pathway

BACKGROUND

Cancer pain is a debilitating disorder of human breast cancer and a primary determinant of the poor quality of life, and relieving pain is fundamental strategy in the cancer treatment. However, opioid analgesics, like morphine and fentanyl, which are widely used in cancer pain treatment have been reported to enhance stem-like traits and epithelial-mesenchymal transition (EMT) of breast cancer cells. As such, it is vital to make the best choice of analgesic for breast cancer management.

METHODS

MTT assays and colony formation assays were performed to examine tumor cell proliferation upon nalbuphine treatment. RT-PCR, western blot, flow cytometry, sphere formation, immunohistochemistry, transwell assays, wound healing assays and mouse xenograft were used to assess the biological effects of nalbuphine treatment.

RESULTS

Nalbuphine inhibited breast cancer cell growth and tumorigenesis, with little effect on noncancerous breast cell lines. Nalbuphine suppressed cancer stem-like traits and EMT in both breast cancer cells and mouse xenograft tumor tissues. Additionally, activation of AKT reversed the nalbuphine-induced inhibition of cancer stem-like properties, tumorigenesis and EMT.

CONCLUSIONS

Our results demonstrate a new role of nalbuphine in inhibiting cancer stem-like properties and EMT in addition to relieving pain, which suggests that nalbuphine may be effective in breast cancer treatment.

Characterization of the molecular changes associated with the overexpression of a novel epithelial cadherin splice variant mRNA in a breast cancer model using proteomics and bioinformatics approaches: identification of changes in cell metabolism and an increased expression of lactate dehydrogenase B

Background

Breast cancer (BC) is the most common female cancer and the leading cause of cancer death in women worldwide. Alterations in epithelial cadherin (E-cadherin) expression and functions are associated to BC, but the underlying molecular mechanisms have not been fully elucidated. We have previously reported a novel human E-cadherin splice variant (E-cadherin variant) mRNA. Stable transfectants in MCF-7 human BC cells (MCF7Ecadvar) depicted fibroblast-like cell morphology, E-cadherin wild-type downregulation, and other molecular changes characteristic of the epithelial-to-mesenchymal transition process, reduced cell-cell adhesion, and increased cell migration and invasion. In this study, a two-dimensional differential gel electrophoresis (2D-DIGE) combined with mass spectrometry (MS) protein identification and bioinformatics analyses were done to characterize biological processes and canonical pathways affected by E-cadherin variant expression.

Results

By 2D-DIGE and MS analysis, 50 proteins were found differentially expressed (≥ Δ1.5) in MCF7Ecadvar compared to control cells. Validation of transcript expression was done in the ten most overexpressed and underexpressed proteins. Bioinformatics analyses revealed that 39 of the 50 proteins identified had been previously associated to BC. Moreover, metabolic processes were the most affected, and glycolysis the canonical pathway most altered. The lactate dehydrogenase B (LDHB) was the highest overexpressed protein, and transcript levels were higher in MCF7Ecadvar than in control cells. In agreement with these findings, MCF7Ecadvar conditioned media had lower glucose and higher lactate levels than control cells. MCF7Ecadvar cell treatment with 5 mM of the glycolytic inhibitor 2-deoxy-glucose led to decreased cell viability, and modulation of LDHB expression in MCF7Ecadvar cells with a specific small interfering RNA resulted in decreased cell proliferation. Finally, a positive association between expression levels of the E-cadherin variant and LDHB transcripts was demonstrated in 21 human breast tumor tissues, and breast tumor samples with higher Ki67 expression showed higher LDHB mRNA levels.

Conclusions

Results from this investigation contributed to further characterize molecular changes associated to the novel E-cadherin splice variant expression in BC cells. They also revealed an association between expression of the novel variant and changes related to BC progression and aggressiveness, in particular those associated to cell metabolism.

Identification of Prognostic Alternative Splicing Signature in Breast Carcinoma

Background

Increasing evidence indicated a close relationship between aberrant splicing variants and carcinoma, whereas comprehensive analysis of prognostic alternative splicing (AS) profiling in breast cancer (BRCA) is lacking and largely unknown.

Methods

RNA-seq data and corresponding clinical information of BRCA patients were obtained and integrated from The Cancer Genome Atlas (TCGA). Then SpliceSeq software was used to assess seven AS types and calculate the Percent Spliced In (PSI) value. Univariate followed by stepwise multivariate Cox regression analyses identified survival associated AS events and constructed the AS signature, which were further sent for enrichment analysis, respectively. Besides, the splicing correlation network was constructed. Additionally, nomogram incorporating AS signature and clinicopathological characteristics was developed and its efficacy was evaluated with respect to discrimination, calibration and clinical utility.

Results

A total of 45,421 AS events were detected, among which 3071 events were found associated with overall survival (OS) after strict filtering. Parent genes of these prognostic events were involved in BRCA-related processes including NF-kappaB and HIF-1 signaling pathway. Besides, the final prognostic signature built with 20 AS events performed well with an area under the curve (AUC) of receiver operating characteristic (ROC) curve up to 0.957 for 5 years. And gene set enrichment analysis (GSEA) also confirmed the candidate 20 AS events contributed to progression of BRCA. Moreover, the nomogram that incorporated 20-AS-event-based classifier, age, pathological stage and Her-2 status showed good calibration and moderate discrimination, with C-index of 0.883 (95% CI, 0.844–0.921). Decision curve analysis (DCA) confirmed more benefit was added to survival prediction with our nomogram, especially in 5 or 8 years with threshold probability up to 80%. Finally, splicing correlation network revealed an obvious regulatory pattern of prognostic splicing factors (SF) in BRCA.

Conclusion

This study provided a systematic portrait of survival-associated AS events involved in BRCA and further presented a AS-clinicopathological nomogram, which could be conveniently used to assist the individualized prediction of long-term survival probability for BRCA patients. And a series of bioinformatic analysis provided a promising perspective for further uncovering the underlying mechanisms of AS events and validating therapeutic targets for BRCA.

MCT-1/miR-34a/IL-6/IL-6R signaling axis promotes EMT progression, cancer stemness and M2 macrophage polarization in triple-negative breast cancer

Background

Triple-negative breast cancer (TNBC) is a poor prognostic breast cancer with the highest mutations and limited therapeutic choices. Cytokine networking between cancer cells and the tumor microenvironment (TME) maintains the self-renewing subpopulation of breast cancer stem cells (BCSCs) that mediate tumor heterogeneity, resistance and recurrence. Immunotherapy of those factors combined with targeted therapy or chemoagents may advantage TNBC treatment.

Results

We found that the oncogene Multiple Copies in T-cell Malignancy 1 (MCT-1/MCTS1) expression is a new poor-prognosis marker in patients with aggressive breast cancers. Overexpressing MCT-1 perturbed the oncogenic breast epithelial acini morphogenesis and stimulated epithelial-mesenchymal transition and matrix metalloproteinase activation in invasive TNBC cells, which were repressed after MCT-1 gene silencing. As mammary tumor progression was promoted by oncogenic MCT-1 activation, tumor-promoting M2 macrophages were enriched in TME, whereas M2 macrophages were decreased and tumor-suppressive M1 macrophages were increased as the tumor was repressed via MCT-1 knockdown. MCT-1 stimulated interleukin-6 (IL-6) secretion that promoted monocytic THP-1 polarization into M2-like macrophages to increase TNBC cell invasiveness. In addition, MCT-1 elevated the soluble IL-6 receptor levels, and thus, IL-6R antibodies antagonized the effect of MCT-1 on promoting M2-like polarization and cancer cell invasion. Notably, MCT-1 increased the features of BCSCs, which were further advanced by IL-6 but prevented by tocilizumab, a humanized IL-6R antibody, thus MCT-1 knockdown and tocilizumab synergistically inhibited TNBC stemness. Tumor suppressor miR-34a was induced upon MCT-1 knockdown that inhibited IL-6R expression and activated M1 polarization.

Conclusions

The MCT-1 pathway is a novel and promising therapeutic target for TNBC.

Electronic supplementary material

The online version of this article (10.1186/s12943-019-0988-0) contains supplementary material, which is available to authorized users.

A novel L1CAM isoform with angiogenic activity generated by NOVA2-mediated alternative splicing

The biological players involved in angiogenesis are only partially defined. Here, we report that endothelial cells (ECs) express a novel isoform of the cell-surface adhesion molecule L1CAM, termed L1-ΔTM. The splicing factor NOVA2, which binds directly to L1CAM pre-mRNA, is necessary and sufficient for the skipping of L1CAM transmembrane domain in ECs, leading to the release of soluble L1-ΔTM. The latter exerts high angiogenic function through both autocrine and paracrine activities. Mechanistically, L1-ΔTM-induced angiogenesis requires fibroblast growth factor receptor-1 signaling, implying a crosstalk between the two molecules. NOVA2 and L1-ΔTM are overexpressed in the vasculature of ovarian cancer, where L1-ΔTM levels correlate with tumor vascularization, supporting the involvement of NOVA2-mediated L1-ΔTM production in tumor angiogenesis. Finally, high NOVA2 expression is associated with poor outcome in ovarian cancer patients. Our results point to L1-ΔTM as a novel, EC-derived angiogenic factor which may represent a target for innovative antiangiogenic therapies.

Growing tumors stimulate the formation of new blood vessels to supply the oxygen and nutrients the cancerous cells need to stay alive. Stopping tumors from forming the blood vessels could therefore help us to treat cancer. To do so, we need to understand how different proteins control when and how blood vessels develop.

Cells make proteins by first ‘transcribing’ genes to form RNA molecules. In many cases, the RNA then goes through a process called alternative splicing. Proteins known as splicing factors cut out different segments of the RNA molecule and stick together the remaining segments to form templates for protein production. This enables a single gene to produce many different variants of a protein.

Angiolini, Belloni, Giordano et al. have now studied mouse and human versions of the cells that line the blood vessels grown by tumors. This revealed that a splicing factor called NOVA2 targets a protein called L1CAM, which is normally responsible for gluing adjacent cells together. Angiolini et al. found that NOVA2 splices L1CAM into a form not seen before. Instead of remaining anchored to cell surfaces, the newly identified form of L1CAM is released into the blood circulation, where it stimulates new blood vessels to grow.

Samples taken from the blood vessels of human ovarian tumors showed high levels of both NOVA2 and the modified form of L1CAM, while blood vessels in healthy tissue contain no, or very low levels of both proteins. Therefore, if the new form of L1CAM can be detected in the blood, it could be used to help cancer diagnosis, and to indicate which patients would benefit from treatments that restrict the growth of blood vessels in tumors. Further work is now needed to explore these possibilities.

Specificity, versatility, and control of TGF-β family signaling

Encoded in mammalian cells by 33 genes, the transforming growth factor-β (TGF-β) family of secreted, homodimeric and heterodimeric proteins controls the differentiation of most, if not all, cell lineages and many aspects of cell and tissue physiology in multicellular eukaryotes. Deregulation of TGF-β family signaling leads to developmental anomalies and disease, whereas enhanced TGF-β signaling contributes to cancer and fibrosis. Here, we review the fundamentals of the signaling mechanisms that are initiated upon TGF-β ligand binding to its cell surface receptors and the dependence of the signaling responses on input from and cooperation with other signaling pathways. We discuss how cells exquisitely control the functional presentation and activation of heteromeric receptor complexes of transmembrane, dual-specificity kinases and, thus, define their context-dependent responsiveness to ligands. We also introduce the mechanisms through which proteins called Smads act as intracellular effectors of ligand-induced gene expression responses and show that the specificity and impressive versatility of Smad signaling depend on cross-talk from other pathways. Last, we discuss how non-Smad signaling mechanisms, initiated by distinct ligand-activated receptor complexes, complement Smad signaling and thus contribute to cellular responses.

Polymethoxylated Flavones Target Cancer Stemness and Improve the Antiproliferative Effect of 5-Fluorouracil in a 3D Cell Model of Colorectal Cancer

Polymethoxylated flavones (PMFs) from citrus fruits are reported to present anticancer potential. However, there is a lack of information regarding their effect on cancer stem cell (CSC) populations, which has been recognized as responsible for tumor initiation, relapse, and chemoresistance. In this study, we evaluated the effect of an orange peel extract (OPE) and its main PMFs, namely, nobiletin, sinensetin, tangeretin, and scutellarein tetramethylether in targeting cell proliferation and stemness using a 3D cell model of colorectal cancer composed of HT29 cell spheroids cultured for 7 days in stirred conditions. Soft agar assay, ALDH1 activity, and relative quantitative gene expression analysis of specific biomarkers were carried out to characterize the stemness, self-renewal, and mesenchymal features of HT29 cell spheroids. Then, the impact of OPE and PMFs in reducing cell proliferation and modulating cancer stemness and self-renewal was assessed. Results showed that, when compared with monolayer cultures, HT29 cell spheroids presented higher ALDH1 activity (81.97% ± 5.27% compared to 63.55% ± 17.49% for 2D), upregulation of CD44, PROM1, SOX9, and SNAI1 genes (1.83 ± 0.34, 2.54 ± 0.51, 2.03 ± 0.15, and 6.12 ± 1.59 times) and high self-renewal capability (352 ± 55 colonies compared to 253 ± 42 for 2D). Incubation with OPE (1 mg/mL) significantly inhibited cell proliferation and modulated cancer stemness and self-renewal ability: colony formation, ALDH1 activity, and the expression of cancer stemness biomarkers PROM1 and LGR5 were significantly reduced (0.66 ± 0.15 and 0.51 ± 0.14 times, respectively). Among all PMFs, tangeretin was the most efficient in targeting the CSC population by decreasing colony formation and the expression of PROM1 and LGR5. Scutellarein tetramethylether was shown to modulate markers of mesenchymal/metastatic transition (increasing CDH1 and reducing ZEB1 and SNAI1) and nobiletin was capable of downregulating PROM1 and SNAI1 expression. Importantly, all PMFs and OPE were shown to synergistically interact with 5-fluorouracil, improving the antiproliferative response of this drug.

Androgen-regulated transcription of ESRP2 drives alternative splicing patterns in prostate cancer

Prostate is the most frequent cancer in men. Prostate cancer progression is driven by androgen steroid hormones, and delayed by androgen deprivation therapy (ADT). Androgens control transcription by stimulating androgen receptor (AR) activity, yet also control pre-mRNA splicing through less clear mechanisms. Here we find androgens regulate splicing through AR-mediated transcriptional control of the epithelial-specific splicing regulator ESRP2. Both ESRP2 and its close paralog ESRP1 are highly expressed in primary prostate cancer. Androgen stimulation induces splicing switches in many endogenous ESRP2-controlled mRNA isoforms, including splicing switches correlating with disease progression. ESRP2 expression in clinical prostate cancer is repressed by ADT, which may thus inadvertently dampen epithelial splice programmes. Supporting this, treatment with the AR antagonist bicalutamide (Casodex) induced mesenchymal splicing patterns of genes including FLNB and CTNND1. Our data reveals a new mechanism of splicing control in prostate cancer with important implications for disease progression.

GATA3 is downregulated in osteosarcoma and facilitates EMT as well as migration through regulation of slug

Background

GATA3 functions as a tumor suppressor and has been observed in multiple types of cancer, but the effects and mechanisms of GATA3 in osteosarcoma (OS) are not yet known.

Methods

The GATA3 expression in OS cells and tissues were detected using quantitative reverse-transcription PCR and Western blotting assay. CCK-8 assay, colony formation assay, wound healing assay as well as transwell assay, were performed to determine the effects of GATA3 on cell proliferation, migration and invasion. ChIP and qChIP as well as luciferase assay were performed whether GATA3 transcriptionally regulated slug expression.

Results

GATA3 was downregulated in OS cells and tissues. The GATA3 expression was closely associated with tumor size as well as metastasis. GATA3 significantly suppressed OS cells proliferation, migration and invasion. EMT-associated transcript factor, slug, was transcriptionally inhibited by GATA3, thereby regulation of EMT in OS.

Conclusion

GATA3 serves as a tumor suppressor in OS and suppresses the progression and metastasis of OS through regulation of slug.

RIT1 suppresses esophageal squamous cell carcinoma growth and metastasis and predicts good prognosis

Ras-like without CAAX1 (RIT1) protein is a member of Ras family, which plays critical roles in signaling pathways and cellular process regulation. However, the role of RIT1 in esophageal squamous cell carcinoma (ESCC) is unclear. In this study, we found that the expression of RIT1 is downregulated in ESCC compared to corresponding non-tumor tissues. The low-level expression of RIT1 was correlated with poorer prognosis. Then we showed that RIT1 inhibited proliferation, invasion, and migration of ESCC cells, and silencing RIT1 by shRNA promoted tumorigenicity and metastasis in nude mice. We further demonstrated that RIT1 inhibited the malignant behaviors of ESCC through inhibiting the PI3K/AKT and MAPK pathway and epithelial–mesenchymal transition in ESCC cells. Our study also revealed that RIT1 increased drug sensitivity to cisplatin (CDDP), and this function could be carried out through downregulating stemness of ESCC. In conclusion, our study indicates for the first time that RIT1 displays tumor-suppressing functions in ESCC, and these functions were carried out by inhibiting MAPK and PI3K/AKT signaling pathway, inhibiting EMT, and downregulating cancer stemness of ESCC cells.

Thyroid cancer stem-like cell exosomes: regulation of EMT via transfer of lncRNAs

Thyroid cancers are the most common endocrine malignancy and approximately 2% of thyroid cancers are anaplastic thyroid carcinoma (ATC), one of the most lethal and treatment resistant human cancers. Cancer stem-like cells (CSCs) may initiate tumorigenesis, induce resistance to chemotherapy and radiation therapy, have multipotent capability and may be responsible for recurrent and metastatic disease. The production of CSCs has been linked to epithelial-mesenchymal transition (EMT) and the acquisition of stemness. Exosomes are small (30-150 nm) membranous vesicles secreted by most cells that play a significant role in cell-to-cell communication. Many non-coding RNAs (ncRNA), such as long-non-coding RNAs (lncRNA), can initiate tumorigenesis and the EMT process. Exosomes carry ncRNAs to local and distant cell populations. This study examines secreted exosomes from two in vitro cell culture models; an EMT model and a CSC model. The EMT was induced in a papillary thyroid carcinoma (PTC) cell line by TGFβ1 treatment. Exosomes from this model were isolated and cultured with naïve PTC cells and examined for EMT induction. In the CSC model, exosomes were isolated from a CSC clonal line, cultured with a normal thyroid cell line and examined for EMT induction. The EMT exosomes transferred the lncRNA MALAT1 and EMT effectors SLUG and SOX2; however, EMT was not induced in this model. The exosomes from the CSC model also transferred the lncRNA MALAT1 and the transcription factors SLUG and SOX2 but additionally transferred linc-ROR and induced EMT in the normal thyroid cells. Preliminary siRNA studies directed towards linc-ROR reduced invasion. We hypothesize that CSC exosomes transfer lncRNAs, importantly linc-ROR, to induce EMT and inculcate the local tumor microenvironment and the distant metastatic niche. Therapies directed towards CSCs, their exosomes and/or the lncRNAs they carry may reduce a tumor's metastatic capacity.

Anaplastic transition within the cancer microenvironment in early-stage oral tongue squamous cell carcinoma is associated with local recurrence

The cancer microenvironment (CME) promotes malignant progression of cancer cells by stimulating cell growth, migration and invasion. Cancer-associated fibroblasts (CAFs), prominent features of the CME, interact directly with cancer cells and facilitate epithelial-mesenchymal transition (EMT). The present study examined the spatial distribution of CAFs and EMT on cancer cells in patients with early-stage tongue squamous cell carcinoma (TSCC) and their association with local recurrence. The present study included 14 patients with early-stage TSCC who had undergone glossectomy between 2006 and 2015, of which 7 experienced local recurrence (LR group) and 7 did not (control group). Multiple immunofluorescent analysis (MIA) of PCNA, αSMA, vimentin, E-cadherin and cytokeratin 14 (CK14) was performed on slides obtained from surgical specimens to identify the expression of various cell-specific markers. The number of CAFs in the CME was significantly increased in the LR group (P=0.001). Furthermore, the neighbouring cancer cells were positive for vimentin expression, indicating EMT. However, the present study also identified concurrent expression of CK14 in all vimentin-positive cancer cells, whilst epithelial markers, including E-cadherin, were expressed in certain vimentin-positive cancer cells. Concurrent expression of CK14 and vimentin is not defined as EMT or partial EMT. Therefore, the present study proposed a novel mechanism of anaplastic transition (APT), in which epithelial cancer cells concurrently develop mesenchymal features, which is achieved by pathways other than EMT. APT is characterized such that epithelial cancer cells differentiate into more primitive states, which is different from EMT or partial EMT, and it may be associated with LR. The concept aids in improving knowledge regarding tumor recurrence in patients with early-stage TSCC.

Stroma-derived IL-6, G-CSF and Activin-A mediated dedifferentiation of lung carcinoma cells into cancer stem cells

Cancer stem cells (CSCs) are a small population of resistant cells inhabiting the tumors. Although comprising only nearly 3% of the tumor mass, these cells were demonstrated to orchestrate tumorigenesis and differentiation, underlie tumors’ heterogeneity and mediate therapy resistance and tumor relapse. Here we show that CSCs may be formed by dedifferentiation of terminally differentiated tumor cells under stress conditions. Using a elegant co-culture cellular system, we were able to prove that nutrients and oxygen deprivation activated non-malignant stromal fibroblasts, which in turn established with tumor cells a paracrine loop mediated by Interleukine-6 (IL-6), Activin-A and Granulocyte colony-stimulating factor (G-CSF), that drove subsequent tumor formation and cellular dedifferentiation. However, by scavenging these cytokines from the media and/or blocking exosomes’ mediated communication it was possible to abrogate dedifferentiation thus turning these mechanisms into potential therapeutic targets against cancer progression.

Flubendazole and mebendazole impair migration and epithelial to mesenchymal transition in oral cell lines

Benzimidazole anthelmintics flubendazole and mebendazole are microtubule-targeting drugs that showed considerable anti-cancer activity in different preclinical models. In this study, the effects of flubendazole and mebendazole on proliferation, migration and cadherin switching were studied in a panel of oral cell lines in vitro. Both compounds reduced the viability of the PE/CA-PJ15 and H376 oral squamous carcinoma cells and of the premalignant oral keratinocytes DOK with the IC₅₀ values in the range of 0.19-0.26 μM. Normal oral keratinocytes and normal gingival fibroblasts were less sensitive to the treatment. Flubendazole and mebendazole also reduced the migration of the PE/CA-PJ15 cell in concentrations that had no anti-migratory effects on the normal gingival fibroblasts. Levels of the focal adhesion kinase FAK, Rho-A and Rac1 GTPases and the Rho guanine nucleotide exchange factor GEF-H1 were decreased in both PE/CA-PJ15 cells and gingival fibroblasts following treatment. Both drugs also interfered with cadherin switching in the model of TGF-β-induced epithelial to mesenchymal transition (EMT) in the DOK cell line. Levels of N-cadherin were reduced in the TGF-β induced cells co-treated with flubendazol and mebendazole in very low concentration (50 nM). These results suggest direct effects of both benzimidazoles on selected processes of EMT in oral cell lines such as cadherin switching as well as cellular migration.

Stem-like and highly invasive prostate cancer cells expressing CD44v8-10 marker originate from CD44-negative cells

In human prostate cancer (PCa), the neuroendocrine cells, expressing the prostate cancer stem cell (CSC) marker CD44, may be resistant to androgen ablation and promote tumor recurrence. During the study of heterogeneity of the highly aggressive neuroendocrine PCa cell lines PC3 and DU-145, we isolated and expanded in vitro a minor subpopulation of very small cells lacking CD44 (CD44^neg). Unexpectedly, these sorted CD44^neg cells rapidly and spontaneously converted to a stable CD44^high phenotype specifically expressing the CD44v8-10 isoform which the sorted CD44^high subpopulation failed to express. Surprisingly and potentially interesting, in these cells expression of CD44v8-10 was found to be induced in stem cell medium. CD44 variant isoforms are known to be more expressed in CSC and metastatic cells than CD44 standard isoform. In agreement, functional analysis of the two sorted and cultured subpopulations has shown that the CD44v8-10^pos PC3 cells, resulting from the conversion of the CD44^neg subpopulation, were more invasive in vitro and had a higher clonogenic potential than the sorted CD44^high cells, in that they produced mainly holoclones, known to be enriched in stem-like cells. Of interest, the CD44v8-10 is more expressed in human PCa biopsies than in normal gland. The discovery of CD44v8-10^pos cells with stem-like and invasive features, derived from a minoritarian CD44^neg cell population in PCa, alerts on the high plasticity of stem-like markers and urges for prudency on the approaches to targeting the putative CSC.

Apoptotic Cell-Derived Extracellular Vesicles Promote Malignancy of Glioblastoma Via Intercellular Transfer of Splicing Factors

Aggressive cancers such as glioblastoma (GBM) contain intermingled apoptotic cells adjacent to proliferating tumor cells. Nonetheless, intercellular signaling between apoptotic and surviving cancer cells remain elusive. In this study, we demonstrate that apoptotic GBM cells paradoxically promote proliferation and therapy resistance of surviving tumor cells by secreting apoptotic extracellular vesicles (apoEVs) enriched with various components of spliceosomes. apoEVs alter RNA splicing in recipient cells, thereby promoting their therapy resistance and aggressive migratory phenotype. Mechanistically, we identified RBM11 as a representative splicing factor that is upregulated in tumors after therapy and shed in extracellular vesicles upon induction of apoptosis. Once internalized in recipient cells, exogenous RBM11 switches splicing of MDM4 and Cyclin D1 toward the expression of more oncogenic isoforms.

Snail knockdown reverses stemness and inhibits tumour growth in ovarian cancer

To develop effective therapies for advanced high grade serous ovarian cancer (HGSOC), understanding mechanisms of recurrence and metastasis is necessary. In this study, we define the epithelial/mesenchymal status of cell lines that accurately model HGSOC, and evaluate the therapeutic potential of targeting Snai1 (Snail), a master regulator of the epithelial/mesenchymal transition (EMT) in vitro and in vivo. The ratio of Snail to E-cadherin (S/E index) at RNA and protein levels was correlated with mesenchymal morphology in four cell lines. The cell lines with high S/E index (OVCAR8 and COV318) showed more CSC-like, motile, and chemoresistant phenotypes than those with low S/E index (OVSAHO and Kuramochi). We tested the role of Snail in regulation of malignant phenotypes including stemness, cell motility, and chemotherapy resistance: shRNA-mediated knockdown of Snail reversed these malignant phenotypes. Interestingly, the expression of let-7 tumour suppressor miRNA was upregulated in Snail knockdown cells. Furthermore, knockdown of Snail decreased tumour burden in an orthotopic xenograft mouse model. We conclude that Snail is important in controlling HGSOC malignant phenotypes and suggest that the Snail/Let-7 axis may be an attractive target for HGSOC treatment.

Alternative splicing and cancer metastasis: prognostic and therapeutic applications

Metastatic cells exhibit an extraordinary phenotypic plasticity, not only in adapting to unfamiliar microenvironments but also in surviving aggressive treatments and immune responses. A major source of phenotypic variability is alternative splicing (AS) of the pre-messenger RNA. This process is catalyzed by one of the most complex pieces of cellular molecular regulatory events, the spliceosome, which is composed of ribonucleoproteins and polypeptides termed spliceosome factors. With strong evidence indicating that AS affects nearly all genes encoded by the human genome, aberrant AS programs have a significant impact on cancer cell development and progression. In this review, we present insights about the genomic and epigenomic factors affecting AS, summarize the most recent findings linking aberrant AS to metastatic progression, and highlight potential prognostic and therapeutic applications.

Ovol2 induces mesenchymal-epithelial transition via targeting ZEB1 in osteosarcoma

Purpose

Osteosarcoma (OS) is the most common type of primary solid bone tumor. Ovo-like zinc finger 2 (Ovol2), a zinc finger transcription factor, is a mesenchymal–epithelial transition (MET) driver that induces miR-200 expression in prostate cancer, breast cancer, and hepatocellular carcinoma. However, little is known about the expression and function of MET in sarcomas, including OS. This study investigated the expression and clinicopathological significance of Ovol2 and its effect on MET in OS.

Patients and methods

The Ovol2 expression in the tumor samples from patients with OS was examined using immunohistochemistry (IHC). We then upregulated the Ovol2 expression in MG-63 and SW1353 cells, detected the expression of MET-associated proteins, and observed the effects of Ovol2 on OS cell proliferation, migration, and cytoskeleton reorganization using Cell Counting Kit-8, transwell invasion, and phalloidin dyeing assays, respectively. The correlation between zinc finger E-box-binding homeobox 1 (ZEB1) and Ovol2 was assessed using the luciferase gene reporter assay in the MG-63 and SW1353 cells and IHC in the human OS tissue samples.

Results

The Ovol2 protein overexpression was related to the clinical grade (P=0.02) and the recurrence and metastasis (P=0.02) of OS. Results of the in vitro experiments showed that Ovol2 overexpression can suppress cell migration and invasion and can regulate the expression levels of MET-associated proteins. Ovol2 suppresses ZEB1 expression by binding to the ZEB1 promoter. Ovol2 is concomitant with a reduced IHC expression of ZEB1 in human OS tissues.

Conclusion

Ovol2 expression is associated with MET in OS cells and suppresses ZEB1 expression and OS progression.

Alpha B-crystallin promotes the invasion and metastasis of gastric cancer via NF-κB-induced epithelial-mesenchymal transition

Alpha B‐crystallin (CRYAB) is overexpressed in a variety of cancers. However, little is known about its specific function and regulatory mechanism in gastric cancer. Here, we first explore the role of CRYAB in gastric cancer progression and metastasis. The expression of CRYAB was determined by western blot and immunohistochemistry in gastric cancer tissues. Besides, methods including stably transfected against CRYAB into gastric cancer cells, western blot, migration and invasion assays in vitro and metastasis assay in vivo were also conducted. The expression of CRYAB is up‐regulated in gastric cancer tissues compared with matched normal tissues. High expression level of CRYAB is closely correlated with cancer metastasis and shorter survival time in patients with gastric cancer. Additionally, CRYAB silencing significantly suppresses epithelial‐mesenchymal transition (EMT), migration and invasion of gastric cancer cells in vitro and in vivo, whereas CRYAB overexpression dramatically reverses these events. Mechanically, CRYAB facilitates gastric cancer cells invasion and metastasis via nuclear factor‐κ‐gene binding (NF‐κB)‐regulated EMT. These findings suggest that CRYAB expression predicts a poor prognosis in patients with gastric cancer. Besides, CRYAB contributes to gastric cancer cells migration and invasion via EMT, mediated by the NF‐κB signalling pathway, thus possibly providing a novel therapeutic target for gastric cancer.

Conversion of epithelial-to-mesenchymal transition to mesenchymal-to-epithelial transition is mediated by oxygen concentration in pancreatic cancer cells

Tumor metastasis is accompanied by a two-stage process of epithelial-to-mesenchymal transition (EMT) and mesenchymal-to-epithelial transition (MET). Currently, the exact mechanisms underlying EMT-MET conversion are unclear. In the present study, the mechanisms by which primary sites (hypoxic) and homing sites (normoxic or hyperoxic) participate in EMT-MET conversion were evaluated. Pancreatic cancer cells were grown under different oxygenation conditions. Cell morphology and epithelial (E)-cadherin and vimentin expression were examined. Transwell chambers were used to examine tumor invasiveness, and scratch assays were performed to examine cell migration. Reverse transcription-polymerase chain reaction and western blot analysis were used to quantitate the mRNA and protein expression of E-cadherin, vimentin, Snail and hypoxia-inducible factor (HIF)-1α. BxPc-3 and Panc-1 cells grown under hypoxic conditions demonstrated increased partial EMT, reduced E-cadherin expression, and increased vimentin expression, compared with cells grown under normoxic or hyperoxic conditions. Cells grown under hypoxic conditions also indicated increased migration and invasiveness. HIF-1α mRNA and protein expression was increased in cells grown under hypoxic conditions. These changes were reversed when a specific inhibitor of the HIF-1α receptor was used to block HIF-1α signaling. Differences in oxygen concentration at primary sites and homing sites are important in the EMT-MET process, and the underlying mechanism may involve HIF-1α-Snail signaling.

Ectopic GRHL2 Expression Due to Non-coding Mutations Promotes Cell State Transition and Causes Posterior Polymorphous Corneal Dystrophy 4

In a large family of Czech origin, we mapped a locus for an autosomal-dominant corneal endothelial dystrophy, posterior polymorphous corneal dystrophy 4 (PPCD4), to 8q22.3-q24.12. Whole-genome sequencing identified a unique variant (c.20+544G>T) in this locus, within an intronic regulatory region of GRHL2. Targeted sequencing identified the same variant in three additional previously unsolved PPCD-affected families, including a de novo occurrence that suggests this is a recurrent mutation. Two further unique variants were identified in intron 1 of GRHL2 (c.20+257delT and c.20+133delA) in unrelated PPCD-affected families. GRHL2 is a transcription factor that suppresses epithelial-to-mesenchymal transition (EMT) and is a direct transcriptional repressor of ZEB1. ZEB1 mutations leading to haploinsufficiency cause PPCD3. We previously identified promoter mutations in OVOL2, a gene not normally expressed in the corneal endothelium, as the cause of PPCD1. OVOL2 drives mesenchymal-to-epithelial transition (MET) by directly inhibiting EMT-inducing transcription factors, such as ZEB1. Here, we demonstrate that the GRHL2 regulatory variants identified in PPCD4-affected individuals induce increased transcriptional activity in vitro. Furthermore, although GRHL2 is not expressed in corneal endothelial cells in control tissue, we detected GRHL2 in the corneal "endothelium" in PPCD4 tissue. These cells were also positive for epithelial markers E-Cadherin and Cytokeratin 7, indicating they have transitioned to an epithelial-like cell type. We suggest that mutations inducing MET within the corneal endothelium are a convergent pathogenic mechanism leading to dysfunction of the endothelial barrier and disease.

Exploration of Involved Key Genes and Signaling Diversity in Brain Tumors

Brain tumors are becoming a major cause of death. The classification of brain tumors has gone through restructuring with regard to some criteria such as the presence or absence of a specific genetic alteration in the 2016 central nervous system World Health Organization update. Two categories of genes with a leading role in tumorigenesis and cancer induction include tumor suppressor genes and oncogenes; tumor suppressor genes are inactivated through a variety of mechanisms that result in their loss of function. As for the oncogenes, overexpression and amplification are the most common mechanisms of alteration. Important cell cycle genes such as p53, ATM, cyclin D2, and Rb have shown altered expression patterns in different brain tumors such as meningioma and astrocytoma. Some genes in signaling pathways have a role in brain tumorigenesis. These pathways include hedgehog, EGFR, Notch, hippo, MAPK, PI3K/Akt, and WNT signaling. It has been shown that telomere length in some brain tumor samples is shortened compared to that in normal cells. As the shortening of telomere length triggers chromosome instability early in brain tumors, it could lead to initiation of cancer. On the other hand, telomerase activity was positive in some brain tumors. It is suggestive that telomere length and telomerase activity are important diagnostic markers in brain tumors. This review focuses on brain tumors with regard to the status of oncogenes, tumor suppressors, cell cycle genes, and genes in signaling pathways as well as the role of telomere length and telomerase in brain tumors.

Clinicopathological and prognostic significance of Twist overexpression in NSCLC

Several studies were conducted to explore the prognostic significance of Twist in non-small cell lung cancer (NSCLC), however, contradictory results in different studies were reported. To this end, we presented a systematic review aiming to summarize the prognostic significance of Twist in patients with NSCLC. 5 studies involving a total of 572 patients were identified. The result indicated that high Twist expression was significantly associated with a worse overall survival (OS) (hazard ratio (HR) = 2.19, 95% confidence interval (95% CI) = 1.64–2.94, p < 0.001; I² = 0.0%, fixed effect), recurrence-free survival (RFS) (HR = 2.476, 95% CI = 1.728–3.547, p < 0.001; I² = 0.0%, fixed effect) and lymph node or other metastasis (odds rate (OR) = 0.419, 95% CI = 0.259–0.679, P < 0.001, fixed effect). Subgroup analysis revealed that the expression of Twist in Chinese patients might be more closely associated with the prognosis of NSCLC than in American patients. Overall, these results indicated that Twist over-expression in patients with NSCLC might be related to poor prognosis and serves as an unfavorable predictor of poor clinicopathological prognosis factor.

Multifaceted Roles of Interleukin-6 in Adipocyte-Breast Cancer Cell Interaction

Breast cancer is the most common malignancy in women worldwide, with a developmental process spanning decades. The malignant cells recruit a variety of cells including fibroblasts, endothelial cells, immune cells, and adipocytes, creating the tumor microenvironment. The tumor microenvironment has emerged as active participants in breast cancer progression and response to treatment through autocrine and paracrine interaction with the malignant cells. Adipose tissue is abundant in the breast cancer microenvironment; interactions with cancer cells create cancer-associated adipocytes which produce a variety of adipokines that influence breast cancer initiation, metastasis, angiogenesis, and cachexia. Interleukin (IL)-6 has emerged as key compound significantly produced by breast cancer cells and adipocytes, with the potential of inducing proliferation, epithelial-mesenchymal phenotype, stem cell phenotype, angiogenesis, cachexia, and therapeutic resistance in breast cancer cells. Our aim is to present a brief knowledge of IL-6’s role in breast cancer. This review summarizes our current understanding of the breast microenvironment, with emphasis on adipocytes as key players in breast cancer tumorigenesis. The effects of key adipocytes such as leptin, adipokines, TGF-b, and IL-6 are discussed. Finally, we discuss the role of IL-6 in various aspects of cancer progression.

Linking Race, Cancer Outcomes, and Tissue Repair

The burden of cancer in the United States is unevenly spread across its different populations, with stark differences in both disease prevalence and outcome on the basis of race and ethnicity. Although a large portion of these differences can be explained by a variety of sociobehavioral and socioeconomic factors, even after these exposures are taken into consideration, considerable disparities persist. In this review, we explore a conceptual framework of biological theories and unifying concepts, based on an evolutionary perspective, that may help better define common guiding principles for exploration of underlying causes of cancer health disparities. The ultimate goal of this conceptual perspective is to outline approaches that may aid in establishing integrated pathway and processes analyses to provide useful insights to guide the development of future interventions. These interventions will improve outcome, increase prevention, and ultimately eliminate all disparities.

FOXC1, the new player in the cancer sandbox

In recent years, rapidly accumulating evidence implicates forkhead box C1 (FOXC1) in cancer, especially in studies of basal-like breast cancer (BLBC). Other studies have followed suit, demonstrating that FOXC1 is not only a major player in this breast cancer subtype, but also in hepatocellular carcinoma (HCC), endometrial cancer, Hodgkin's lymphoma (HL), and non-Hodgkin's lymphoma (NHL). The FOXC1 gene encodes a transcription factor that is crucial to mesodermal, neural crest, and ocular development, and mutations found in FOXC1 have been found to cause dominantly inherited Axenfeld-Rieger Syndrome (ARS). Interestingly, while FOXC1 missense mutations that are associated with ARS usually reduce gene activity, increased FOXC1 function now appears to be often linked to more aggressive cancer phenotypes in BLBC, HCC, HL, and NHL. This review discusses not only the role of FOXC1 in cancer cell progression, proliferation, differentiation, and metastasis, but also the underlying mechanisms of how FOXC1 can contribute to aggressive cancer phenotypes.