Prrx1 isoform switching regulates pancreatic cancer invasion and metastatic colonization

PRRX1-TOP2A interaction is a malignancy-promoting factor in human malignant peripheral nerve sheath tumours

BACKGROUND

Paired related-homeobox 1 (PRRX1) is a transcription factor in the regulation of developmental morphogenetic processes. There is growing evidence that PRRX1 is highly expressed in certain cancers and is critically involved in human survival prognosis. However, the molecular mechanism of PRRX1 in cancer malignancy remains to be elucidated.

METHODS

PRRX1 expression in human Malignant peripheral nerve sheath tumours (MPNSTs) samples was detected immunohistochemically to evaluate survival prognosis. MPNST models with PRRX1 gene knockdown or overexpression were constructed in vitro and the phenotype of MPNST cells was evaluated. Bioinformatics analysis combined with co-immunoprecipitation, mass spectrometry, RNA-seq and structural prediction were used to identify proteins interacting with PRRX1.

RESULTS

High expression of PRRX1 was associated with a poor prognosis for MPNST. PRRX1 knockdown suppressed the tumorigenic potential. PRRX1 overexpressed in MPNSTs directly interacts with topoisomerase 2 A (TOP2A) to cooperatively promote epithelial-mesenchymal transition and increase expression of tumour malignancy-related gene sets including mTORC1, KRAS and SRC signalling pathways. Etoposide, a TOP2A inhibitor used in the treatment of MPNST, may exhibit one of its anticancer effects by inhibiting the PRRX1-TOP2A interaction.

CONCLUSION

Targeting the PRRX1-TOP2A interaction in malignant tumours with high PRRX1 expression might provide a novel tumour-selective therapeutic strategy.

Exploiting transcription factors to target EMT and cancer stem cells for tumor modulation and therapy

Transcription factors (TFs) are essential in controlling gene regulatory networks that determine cellular fate during embryogenesis and tumor development. TFs are the major players in promoting cancer stemness by regulating the function of cancer stem cells (CSCs). Understanding how TFs interact with their downstream targets for determining cell fate during embryogenesis and tumor development is a critical area of research. CSCs are increasingly recognized for their significance in tumorigenesis and patient prognosis, as they play a significant role in cancer initiation, progression, metastasis, and treatment resistance. However, traditional therapies have limited effectiveness in eliminating this subset of cells, allowing CSCs to persist and potentially form secondary tumors. Recent studies have revealed that cancer cells and tumors with CSC-like features also exhibit genes related to the epithelial-to-mesenchymal transition (EMT). EMT-associated transcription factors (EMT-TFs) like TWIST and Snail/Slug can upregulate EMT-related genes and reprogram cancer cells into a stem-like phenotype. Importantly, the regulation of EMT-TFs, particularly through post-translational modifications (PTMs), plays a significant role in cancer metastasis and the acquisition of stem cell-like features. PTMs, including phosphorylation, ubiquitination, and SUMOylation, can alter the stability, localization, and activity of EMT-TFs, thereby modulating their ability to drive EMT and stemness properties in cancer cells. Although targeting EMT-TFs holds potential in tackling CSCs, current pharmacological approaches to do so directly are unavailable. Therefore, this review aims to explore the role of EMT- and CSC-TFs, their connection and impact in cellular development and cancer, emphasizing the potential of TF networks as targets for therapeutic intervention.

Phenotypic Heterogeneity, Bidirectionality, Universal Cues, Plasticity, Mechanics, and the Tumor Microenvironment Drive Cancer Metastasis

Tumor diseases become a huge problem when they embark on a path that advances to malignancy, such as the process of metastasis. Cancer metastasis has been thoroughly investigated from a biological perspective in the past, whereas it has still been less explored from a physical perspective. Until now, the intraluminal pathway of cancer metastasis has received the most attention, while the interaction of cancer cells with macrophages has received little attention. Apart from the biochemical characteristics, tumor treatments also rely on the tumor microenvironment, which is recognized to be immunosuppressive and, as has recently been found, mechanically stimulates cancer cells and thus alters their functions. The review article highlights the interaction of cancer cells with other cells in the vascular metastatic route and discusses the impact of this intercellular interplay on the mechanical characteristics and subsequently on the functionality of cancer cells. For instance, macrophages can guide cancer cells on their intravascular route of cancer metastasis, whereby they can help to circumvent the adverse conditions within blood or lymphatic vessels. Macrophages induce microchannel tunneling that can possibly avoid mechanical forces during extra- and intravasation and reduce the forces within the vascular lumen due to vascular flow. The review article highlights the vascular route of cancer metastasis and discusses the key players in this traditional route. Moreover, the effects of flows during the process of metastasis are presented, and the effects of the microenvironment, such as mechanical influences, are characterized. Finally, the increased knowledge of cancer metastasis opens up new perspectives for cancer treatment.

Update on Epithelial-Mesenchymal Plasticity in Cancer Progression

Epithelial-mesenchymal transition (EMT) is a cellular process by which epithelial cells lose their characteristics and acquire mesenchymal traits to promote cell movement. This program is aberrantly activated in human cancers and endows tumor cells with increased abilities in tumor initiation, cell migration, invasion, metastasis, and therapy resistance. The EMT program in tumors is rarely binary and often leads to a series of gradual or intermediate epithelial-mesenchymal states. Functionally, epithelial-mesenchymal plasticity (EMP) improves the fitness of cancer cells during tumor progression and in response to therapies. Here, we discuss the most recent advances in our understanding of the diverse roles of EMP in tumor initiation, progression, metastasis, and therapy resistance and address major clinical challenges due to EMP-driven phenotypic heterogeneity in cancer. Uncovering novel molecular markers and key regulators of EMP in cancer will aid the development of new therapeutic strategies to prevent cancer recurrence and overcome therapy resistance.

Transcriptional regulation of EMT transcription factors in cancer

The epithelial-mesenchymal transition (EMT) is one of the processes by which epithelial cells transdifferentiate into mesenchymal cells in the developmental stage, known as "complete EMT." In epithelial cancer, EMT, also termed "partial EMT," is associated with invasion, metastasis, and resistance to therapy, and is elicited by several transcription factors, frequently referred to as EMT transcription factors. Among these transcription factors that regulate EMT, ZEB1/2 (ZEB1 and ZEB2), SNAIL, and TWIST play a prominent role in driving the EMT process (hereafter referred to as "EMT-TFs"). Among these, ZEB1/2 show positive correlation with both expression of mesenchymal marker proteins and the aggressiveness of various carcinomas. On the other hand, TWIST and SNAIL are also correlated with the aggressiveness of carcinomas, but are not highly correlated with mesenchymal marker protein expression. Interestingly, these EMT-TFs are not detected simultaneously in any studied cases of aggressive cancers, except for sarcoma. Thus, only one or some of the EMT-TFs are expressed at high levels in cells of aggressive carcinomas. Expression of EMT-TFs is regulated by transforming growth factor-β (TGF-β), a well-established inducer of EMT, in cooperation with other signaling molecules, such as active RAS signals. The focus of this review is the molecular mechanisms by which EMT-TFs are transcriptionally sustained at sufficiently high levels in cells of aggressive carcinomas and upregulated by TGF-β during cancer progression.

Epigenetic control of pancreatic cancer metastasis

Surgical resection, when combined with chemotherapy, has been shown to significantly improve the survival rate of patients with pancreatic ductal adenocarcinoma (PDAC). However, this treatment option is only feasible for a fraction of patients, as more than 50% of cases are diagnosed with metastasis. The multifaceted process of metastasis is still not fully understood, but recent data suggest that transcriptional and epigenetic plasticity play significant roles. Interfering with epigenetic reprogramming can potentially control the adaptive processes responsible for metastatic progression and therapy resistance, thereby enhancing treatment responses and preventing recurrence. This review will focus on the relevance of histone-modifying enzymes in pancreatic cancer, specifically on their impact on the metastatic cascade. Additionally, it will also provide a brief update on the current clinical developments in epigenetic therapies.

The epithelial-mesenchymal plasticity landscape: principles of design and mechanisms of regulation

Epithelial-mesenchymal plasticity (EMP) enables cells to interconvert between several states across the epithelial-mesenchymal landscape, thereby acquiring hybrid epithelial/mesenchymal phenotypic features. This plasticity is crucial for embryonic development and wound healing, but also underlies the acquisition of several malignant traits during cancer progression. Recent research using systems biology and single-cell profiling methods has provided novel insights into the main forces that shape EMP, which include the microenvironment, lineage specification and cell identity, and the genome. Additionally, key roles have emerged for hysteresis (cell memory) and cellular noise, which can drive stochastic transitions between cell states. Here, we review these forces and the distinct but interwoven layers of regulatory control that stabilize EMP states or facilitate epithelial-mesenchymal transitions (EMTs) and discuss the therapeutic potential of manipulating the EMP landscape.

Semaphorin 3 C enhances putative cancer stemness and accelerates peritoneal dissemination in pancreatic cancer

PURPOSE

Semaphorins, axon guidance cues in neuronal network formation, have been implicated in cancer progression. We previously identified semaphorin 3 C (SEMA3C) as a secreted protein overexpressed in pancreatic ductal adenocarcinoma (PDAC). We, therefore, hypothesized that SEMA3C supports PDAC progression. In this study, we aimed to investigate the clinical features of SEMA3C, especially its association with chemo-resistance and peritoneal dissemination.

METHODS

In resected PDAC tissues, we assessed the relationship between SEMA3C expression and clinicopathological features by immunohistochemistry. In vitro studies, we have shown invasion assay, pancreatosphere formation assay, colony formation assay, cytotoxicity assay, and activation of SEMA3C downstream targets (c-Met, Akt, mTOR). In vivo, we performed a preclinical trial to confirm the efficacy of SEMA3C shRNA knockdown and Gemcitabine and nab-Paclitaxel (GnP) in an orthotopic transplantation mouse model and in peritoneal dissemination mouse model.

RESULTS

In resected PDAC tissues, SEMA3C expression correlated with invasion and peritoneal dissemination after surgery. SEMA3C promoted cell invasion, self-renewal, and colony formation in vitro. We further demonstrated that SEMA3C knockdown increased Gem-induced cytotoxicity by suppressing the activation of the Akt/mTOR pathway via the c-Met receptor. Combination therapy with SEMA3C knockdown and GnP reduced tumor growth and peritoneal dissemination.

CONCLUSIONS

SEMA3C enhances peritoneal dissemination by regulating putative cancer stemness and Gem resistance and activates phosphorylation of the Akt/mTOR pathway via c-Met. Our findings provide a new avenue for therapeutic strategies in regulating peritoneal dissemination during PDAC progression.

Cancer cell plasticity during tumor progression, metastasis and response to therapy

Cell plasticity represents the ability of cells to be reprogrammed and to change their fate and identity, enabling homeostasis restoration and tissue regeneration following damage. Cell plasticity also contributes to pathological conditions, such as cancer, enabling cells to acquire new phenotypic and functional features by transiting across distinct cell states that contribute to tumor initiation, progression, metastasis and resistance to therapy. Here, we review the intrinsic and extrinsic mechanisms driving cell plasticity that promote tumor growth and proliferation as well as metastasis and drug tolerance. Finally, we discuss how cell plasticity could be exploited for anti-cancer therapy.

ZHX2 deficiency enriches hybrid MET cells through regulating E-cadherin expression

Growing evidence indicates that the epithelial to mesenchymal (E/M) hybrid state plays a key role in tumorigenesis. Importantly, a hybrid mesenchymal to epithelial transition (MET) state in which individual cells express both epithelial and mesenchymal markers was recently identified in vivo, further strengthening the bonds between the hybrid EMT state and cancer progression. However, the role and the molecular mechanisms by which the hybrid MET state is maintained in triple-negative breast cancer cells (TNBC) remain elusive. Here, we find that loss of ZHX2 expression results in the hybrid MET phenotype in mesenchymal TNBC cells. Mechanistically, through directly binding to the CDH1 promoter, depletion of ZHX2 specifically reactivates expression of CDH1 encoding E-cadherin, an epithelial marker that is crucial for maintaining epithelial phenotype. Functionally, loss of ZHX2 expression enriches the hybrid MET cells and inhibits the migration and dissemination of TNBC cells or organoids, which could be reversed by restoration of E-cadherin. Moreover, depletion of ZHX2 suppresses lung metastasis in preclinical models of TNBC. In patients with TNBC, ZHX2 expression was amplified and negatively correlated with the expression of E-cadherin. These findings suggest that loss of ZHX2 promotes the hybrid MET state to impair TNBC progression.

Role of epithelial-mesenchymal transition factor SNAI1 and its targets in ovarian cancer aggressiveness

Ovarian cancer remains the most lethal gynecologic malignancy in the USA. For over twenty years, epithelial-mesenchymal transition (EMT) has been characterized extensively in development and disease. The dysregulation of this process in cancer has been identified as a mechanism by which epithelial tumors become more aggressive, allowing them to survive and invade distant tissues. This occurs in part due to the increased expression of the EMT transcription factor, SNAI1 (Snail). In the case of epithelial ovarian cancer, Snail has been shown to contribute to cancer invasion, stemness, chemoresistance, and metabolic changes. Thus, in this review, we focus on summarizing current findings on the role of EMT (specifically, factors downstream of Snail) in determining ovarian cancer aggressiveness.

The Epithelial to Mesenchymal Transition in Colorectal Cancer Progression: The Emerging Role of Succinate Dehydrogenase Alterations and Succinate Accumulation

Colorectal cancer (CRC) stands as the third most significant contributor to cancer-related mortality worldwide. A major underlying reason is that the detection of CRC usually occurs at an advanced metastatic stage, rendering therapies ineffective. In the progression from the in situ neoplasia stage to the advanced metastatic stage, a critical molecular mechanism involved is the epithelial-to-mesenchymal transition (EMT). This intricate transformation consists of a series of molecular changes, ultimately leading the epithelial cell to relinquish its features and acquire mesenchymal and stem-like cell characteristics. The EMT regulation involves several factors, such as transcription factors, cytokines, micro RNAs and long noncoding RNAs. Nevertheless, recent studies have illuminated an emerging link between metabolic alterations and EMT in various types of cancers, including colorectal cancers. In this review, we delved into the pivotal role played by EMT during CRC progression, with a focus on highlighting the relationship between the alterations of the tricarboxylic acid cycle, specifically those involving the succinate dehydrogenase enzyme, and the activation of the EMT program. In fact, emerging evidence supports the idea that elucidating the metabolic modifications that can either induce or inhibit tumor progression could be of immense significance for shaping new therapeutic approaches and preventative measures. We conclude that an extensive effort must be directed towards research for the standardization of drugs that specifically target proteins such as SDH and SUCNR1, but also TRAP1, PDH, ERK1/2, STAT3 and the HIF1-α catabolism.

Nanocarrier of Pin1 inhibitor based on supercritical fluid technology inhibits cancer metastasis by blocking multiple signaling pathways

Cancer metastasis is the primary cause of all cancer-related deaths due to the lack of effective targeted drugs that simultaneously block multiple signaling pathways that drive the dissemination and growth of cancer cells. The unique proline isomerase Pin1 activates numerous cancer pathways, but its role in cancer metastasis and the inhibitory efficacy of Pin1 inhibitors on cancer metastasis are unknown. Moreover, the applicability of Pin1 inhibitor-all-trans retinoic acid (ATRA) is limited due to its several drawbacks. Herein, uniform ATRA-loaded polylactic acid-polyethylene glycol block copolymer nanoparticles (ATRA-NPs) with high encapsulation efficiency, good cellular uptake, excellent controlled release performance and pharmacokinetics are developed using supercritical carbon dioxide processing combined with an optimized design. ATRA-NPs exhibited excellent biosafety and significant inhibition on the growth and metastasis of hepatocellular carcinoma. Pin1 played a key role in cancer metastasis and was the main target of ATRA-NPs. ATRA-NPs exerted their potent anti-metastatic effect by inhibiting Pin1 and then simultaneously blocking multiple signaling pathways and cancer epithelial-mesenchymal progression. Since ATRA-NPs could effectively couple the inhibition of cancer cell dissemination with cancer growth, it provided a novel therapeutic strategy for efficiently inhibiting cancer metastasis.

PRRX1 promotes colorectal cancer stemness and chemoresistance via the JAK2/STAT3 axis by targeting IL-6

Background

Stemness acquirement is one of the hallmarks of cancer and the major reason for the chemoresistance and poor prognosis of colorectal cancer (CRC). Previous research has revealed the stimulatory role of paired related homeobox 1 (PRRX1) on CRC metastasis. However, the role of PRRX1 in stemness acquirement and chemoresistance of CRC is still not clear.

Methods

A retrospective cohort study was performed to investigate the relationship between PRRX1 expression and multiple clinicopathological characteristics of CRC patients. The functional effects of PRRX1 on stemness and chemoresistance of CRC cells were validated by in vitro and in vivo assays. Gene set enrichment analysis (GSEA) and JASPAR software were performed to predict the underlying mechanisms. Enzyme-linked immunosorbent assay (ELISA), Western blot, immunofluorescence, and dual-luciferase reporter assays were used to confirm the PRRX1-mediated signaling and its downstream factors.

Results

The expression of PRRX1 was up-regulated in CRC tissues and cell lines compared to normal epithelial tissues and cell lines. High expression of PRRX1 was tightly associated with the metastasis, chemoresistance, and poor prognosis of CRC patients. Additionally, PRRX1 significantly promoted the proliferation, viability, stemness, and chemoresistance of CRC cells, as well as the activation of the interleukin-6 (IL-6)/JAK2/STAT3 axis. Inhibiting the expression of IL-6 dramatically eliminated the effects of PRRX1 on CRC cell stemness and chemoresistance.

Conclusions

PRRX1 plays a vital role in the stemness and chemoresistance of CRC cells via JAK2/STAT3 signaling by targeting IL-6. Further, PRRX1 may be a valid biomarker for predicting the effect of chemotherapy and prognosis of CRC patients.

PRRX2 predicts poor survival prognosis, and promotes malignant phenotype of lung adenocarcinoma via transcriptional activates PSMD1

INTRODUCTION

Paired-related homeobox transcription factor 2 (PRRX2) has been proved involves in the pathogenesis of tumors, but the role of PRRX2 in lung adenocarcinoma (LUAD) is basically not clear.

MATERIALS AND METHODS

LUAD datasets were obtained from Gene Expression Omnibus datasets. Functional enrichment analyses were performed based on R language. Several online analysis tools were used for PRRX2 expression, survival curves, and immune cell infiltration analyses. CCK-8, flow cytometry assays were used to detect the cell proliferation and apoptosis. Dual luciferase reporter system and chromatin immunoprecipitation were used to explore the interaction of PRRX2 and Proteasome 26S subunit, non-ATPases 1 (PSMD1). Xenograft in nude mice was used to assess the function of PRRX2 regulation in vivo.

RESULTS AND DISCUSSION

Bioinformatics analyses found that PRRX2 was highly expressed in LUAD tissues and the high PRRX2 expression had a poor prognostic value. PRRX2 was highly expressed in LUAD clinical samples and cell lines. PRRX2 acted as a positive regulator of cell proliferation and a negative regulator of apoptosis. PRRX2 could bind with the PSMD1 promoter and regulate PSMD1 expression, thereby affected LUAD cells' malignant phenotype. Result of xenografts in nude mice confirmed that PRRX2 promotes LUAD tumor growth in vivo. Summary, our study results reveal the crucial roles for PRRX2 in the proliferation and apoptosis of LUAD progression and suggest that PRRX2 may regulate PSMD1 expression by combining with the PSMD1 promoter, thereby participating in the malignant behavior of LUAD.

A cellular hierarchy in melanoma uncouples growth and metastasis

Although melanoma is notorious for its high degree of heterogeneity and plasticity1,2, the origin and magnitude of cell-state diversity remains poorly understood. Equally, it is unclear whether growth and metastatic dissemination are supported by overlapping or distinct melanoma subpopulations. Here, by combining mouse genetics, single-cell and spatial transcriptomics, lineage tracing and quantitative modelling, we provide evidence of a hierarchical model of tumour growth that mirrors the cellular and molecular logic underlying the cell-fate specification and differentiation of the embryonic neural crest. We show that tumorigenic competence is associated with a spatially localized perivascular niche, a phenotype acquired through an intercellular communication pathway established by endothelial cells. Consistent with a model in which only a fraction of cells are fated to fuel growth, temporal single-cell tracing of a population of melanoma cells with a mesenchymal-like state revealed that these cells do not contribute to primary tumour growth but, instead, constitute a pool of metastatic initiating cells that switch cell identity while disseminating to secondary organs. Our data provide a spatially and temporally resolved map of the diversity and trajectories of melanoma cell states and suggest that the ability to support growth and metastasis are limited to distinct pools of cells. The observation that these phenotypic competencies can be dynamically acquired after exposure to specific niche signals warrant the development of therapeutic strategies that interfere with the cancer cell reprogramming activity of such microenvironmental cues.

Epithelial–mesenchymal transition: The history, regulatory mechanism, and cancer therapeutic opportunities

Epithelial–mesenchymal transition (EMT) is a program wherein epithelial cells lose their junctions and polarity while acquiring mesenchymal properties and invasive ability. Originally defined as an embryogenesis event, EMT has been recognized as a crucial process in tumor progression. During EMT, cell–cell junctions and cell–matrix attachments are disrupted, and the cytoskeleton is remodeled to enhance mobility of cells. This transition of phenotype is largely driven by a group of key transcription factors, typically Snail, Twist, and ZEB, through epigenetic repression of epithelial markers, transcriptional activation of matrix metalloproteinases, and reorganization of cytoskeleton. Mechanistically, EMT is orchestrated by multiple pathways, especially those involved in embryogenesis such as TGFβ, Wnt, Hedgehog, and Hippo, suggesting EMT as an intrinsic link between embryonic development and cancer progression. In addition, redox signaling has also emerged as critical EMT modulator. EMT confers cancer cells with increased metastatic potential and drug resistant capacity, which accounts for tumor recurrence in most clinic cases. Thus, targeting EMT can be a therapeutic option providing a chance of cure for cancer patients. Here, we introduce a brief history of EMT and summarize recent advances in understanding EMT mechanisms, as well as highlighting the therapeutic opportunities by targeting EMT in cancer treatment.

NR2F1 is a barrier to dissemination of early stage breast cancer cells

Cancer cells can disseminate during very early and sometimes asymptomatic stages of tumor progression. Though biological barriers to tumorigenesis have been identified and characterized, the mechanisms that limit early dissemination remain largely unknown. We report here that the orphan nuclear receptor NR2F1/COUP-TF1 serves as a barrier to early dissemination. NR2F1 expression was decreased in patient ductal carcinoma in situ (DCIS) samples. High-resolution intravital imaging of HER2+ early stage cancer cells revealed that loss of function of NR2F1 increased in vivo dissemination and was accompanied by decreased E-cadherin expression, activation of WNT-dependent β-catenin signaling, disorganized laminin 5 deposition, and increased expression of EMT genes such as TWIST1, ZEB1, and PRRX1. Furthermore, downregulation of NR2F1 promoted a hybrid luminal/basal phenotype. NR2F1 expression was positively regulated by p38α signaling and repressed by HER2 and WNT4 pathways. Lastly, early cancer cells with NR2F1LOW/PRRX1HIGH staining were observed in DCIS samples. Together, these findings reveal the existence of an inhibitory mechanism of dissemination regulated by NR2F1 in early stage breast cancer cells.

The Quasimesenchymal Pancreatic Ductal Epithelial Cell Line PANC-1-A Useful Model to Study Clonal Heterogeneity and EMT Subtype Shifting

Simple Summary

Malignant tumors often escape therapy due to clonal propagation of a subfraction of drug-resistant cancer cells. The underlying phenomenon of intratumoral heterogeneity is driven by epithelial–mesenchymal plasticity (EMP) involving the developmental programs, epithelial–mesenchymal transition (EMT), in which epithelial cells are converted to invasive mesenchymal cells, and the reverse process, mesenchymal–epithelial transition (MET), which allows for metastatic outgrowth at distant sites. For therapeutic targeting of EMP, a better understanding of this process is required; however, cellular models with which to study EMP in pancreatic ductal adenocarcinoma (PDAC) are scarce. Using single-cell clonal analysis, we have found the PDAC cell line, PANC-1, to consist of cells with different E/M phenotypes and functional attributes. Parental PANC-1 cultures could be induced in vitro to shift towards either a more mesenchymal or a more epithelial phenotype, and this bidirectional shift was controlled by the small GTPases RAC1 and RAC1b, together identifying PANC-1 cells as a useful model with which to study EMP.

Abstract

Intratumoral heterogeneity (ITH) is an intrinsic feature of malignant tumors that eventually allows a subfraction of resistant cancer cells to clonally evolve and cause therapy failure or relapse. ITH, cellular plasticity and tumor progression are driven by epithelial–mesenchymal transition (EMT) and the reverse process, MET. During these developmental programs, epithelial (E) cells are successively converted to invasive mesenchymal (M) cells, or back to E cells, by passing through a series of intermediate E/M states, a phenomenon termed E–M plasticity (EMP). The induction of MET has clinical potential as it can block the initial EMT stages that favor tumor cell dissemination, while its inhibition can curb metastatic outgrowth at distant sites. In pancreatic ductal adenocarcinoma (PDAC), cellular models with which to study EMP or MET induction are scarce. Here, we have generated single cell-derived clonal cultures of the quasimesenchymal PDAC-derived cell line, PANC-1, and found that these differ strongly with respect to cell morphology and EMT marker expression, allowing for their tentative classification as E, E/M or M. Interestingly, the different EMT phenotypes were found to segregate with differences in tumorigenic potential in vitro, as measured by colony forming and invasive activities, and in circadian clock function. Moreover, the individual clones the phenotypes of which remained stable upon prolonged culture also responded differently to treatment with transforming growth factor (TGF)β1 in regard to regulation of growth and individual TGFβ target genes, and to culture conditions that favour ductal-to-endocrine transdifferentiation as a more direct measure for cellular plasticity. Of note, stimulation with TGFβ1 induced a shift in parental PANC-1 cultures towards a more extreme M and invasive phenotype, while exposing the cells to a combination of the proinflammatory cytokines IFNγ, IL1β and TNFα (IIT) elicited a shift towards a more E and less invasive phenotype resembling a MET-like process. Finally, we show that the actions of TGFβ1 and IIT both converge on regulating the ratio of the small GTPase RAC1 and its splice isoform, RAC1b. Our data provide strong evidence for dynamic EMT–MET transitions and qualify this cell line as a useful model with which to study EMP.

PRRX1 Is a Novel Prognostic Biomarker and Facilitates Tumor Progression Through Epithelial–Mesenchymal Transition in Uveal Melanoma

Uveal melanoma (UM) is the most common primary intraocular malignancy in adults. UM develops and is sustained by inflammation and immunosuppression from the tumor microenvironment (TME). This study sought to identify a reliable TME-related biomarker that could provide survival prediction and new insight into therapy for UM patients. Based on clinical characteristics and the RNA-seq transcriptome data of 80 samples from The Cancer Genome Atlas (TCGA) database, PRRX1 as a TME- and prognosis-related gene was identified using the ESTIMATE algorithm and the LASSO–Cox regression model. A prognostic model based on PRRX1 was constructed and validated with a Gene Expression Omnibus (GEO) dataset of 63 samples. High PRRX1 expression was associated with poorer overall survival (OS) and metastasis-free survival (MFS) in UM patients. Comprehensive results of the prognostic analysis showed that PRRX1 was an independent and reliable predictor of UM. Then the results of immunological characteristics demonstrated that higher expression of PRRX1 was accompanied by higher expression of immune checkpoint genes, lower tumor mutation burden (TMB), and greater tumor cell infiltration into the TME. Gene set enrichment analysis (GSEA) showed that high PRRX1 expression correlated with angiogenesis, epithelial–mesenchymal transition (EMT), and inflammation. Furthermore, downregulation of PRRX1 weakened the process of EMT, reduced cell invasion and migration of human UM cell line MuM-2B in vitro. Taken together, these findings indicated that increased PRRX1 expression is independently a prognostic factor of poorer OS and MFS in patients with UM, and that PRRX1 promotes malignant progression of UM by facilitating EMT, suggesting that PRRX1 may be a potential target for UM therapy.

HDAC2 Facilitates Pancreatic Cancer Metastasis

The mortality of patients with pancreatic ductal adenocarcinoma (PDAC) is strongly associated with metastasis, a multistep process that is incompletely understood in this disease. Although genetic drivers of PDAC metastasis have not been defined, transcriptional and epigenetic rewiring can contribute to the metastatic process. The epigenetic eraser histone deacetylase 2 (HDAC2) has been connected to less differentiated PDAC, but the function of HDAC2 in PDAC has not been comprehensively evaluated. Using genetically defined models, we show that HDAC2 is a cellular fitness factor that controls cell cycle in vitro and metastasis in vivo, particularly in undifferentiated, mesenchymal PDAC cells. Unbiased expression profiling detected a core set of HDAC2-regulated genes. HDAC2 controlled expression of several prosurvival receptor tyrosine kinases connected to mesenchymal PDAC, including PDGFRα, PDGFRβ, and EGFR. The HDAC2-maintained program disabled the tumor-suppressive arm of the TGFβ pathway, explaining impaired metastasis formation of HDAC2-deficient PDAC. These data identify HDAC2 as a tractable player in the PDAC metastatic cascade. The complexity of the function of epigenetic regulators like HDAC2 implicates that an increased understanding of these proteins is needed for implementation of effective epigenetic therapies.

SIGNIFICANCE

HDAC2 has a context-specific role in undifferentiated PDAC and the capacity to disseminate systemically, implicating HDAC2 as targetable protein to prevent metastasis.

The effect of the low stromal ratio induced by neoadjuvant chemotherapy on recurrence patterns in borderline resectable pancreatic ductal adenocarcinoma

The optimal regimens of neoadjuvant chemotherapy (NAC) and its biological and physiological modification of the tumor microenvironment (TME) in patients with borderline resectable pancreatic ductal adenocarcinoma (BR PDAC) remain unknown. A deeper understanding of the complex stromal biology of the TME will identify new avenues to establish treatment strategies for PDAC patients. Herein, we sought to clarify whether stromal remodeling by NAC affects recurrence patterns and prognosis in BR PDAC patients. We retrospectively analyzed data from 104 BR PDAC patients who underwent pancreatectomy with or without NAC (upfront surgery [UpS], n = 44; gemcitabine + nab-paclitaxel [GnP], n = 28; and gemcitabine + S-1 [GS], n = 32) to assess the correlations of treatment with early recurrence, the stromal ratio, and Ki-67 levels. Eighty-six patients experienced recurrence, and those with liver metastasis had significantly shorter recurrence-free survival than those with other recurrence patterns. The frequency of liver metastasis was significantly higher in patients with a low stromal ratio than in those with a high stromal ratio in the NAC group but not in the UpS group. Patients in the GnP group had significantly higher Ki-67 than those in the GS and UpS groups. A low stromal ratio was positively correlated with high Ki-67 in the NAC group but not in the UpS group. The low stromal ratio induced by NAC promoted early liver metastasis in patients with BR PDAC. Our findings provide new insights into the complexity of stromal biology, leading to consideration of the optimal NAC regimen.

Deregulation of Transcription Factor Networks Driving Cell Plasticity and Metastasis in Pancreatic Cancer

Pancreatic cancer is a very aggressive disease with 5-year survival rates of less than 10%. The constantly increasing incidence and stagnant patient outcomes despite changes in treatment regimens emphasize the requirement of a better understanding of the disease mechanisms. Challenges in treating pancreatic cancer include diagnosis at already progressed disease states due to the lack of early detection methods, rapid acquisition of therapy resistance, and high metastatic competence. Pancreatic ductal adenocarcinoma, the most prevalent type of pancreatic cancer, frequently shows dominant-active mutations in KRAS and TP53 as well as inactivation of genes involved in differentiation and cell-cycle regulation (e.g. SMAD4 and CDKN2A). Besides somatic mutations, deregulated transcription factor activities strongly contribute to disease progression. Specifically, transcriptional regulatory networks essential for proper lineage specification and differentiation during pancreas development are reactivated or become deregulated in the context of cancer and exacerbate progression towards an aggressive phenotype. This review summarizes the recent literature on transcription factor networks and epigenetic gene regulation that play a crucial role during tumorigenesis.

Understanding the Complex Milieu of Epithelial-Mesenchymal Transition in Cancer Metastasis: New Insight Into the Roles of Transcription Factors

Epithelial-mesenchymal transition (EMT) is a physiological program during which polarised, immobile epithelial cells lose connection with their neighbours and are converted to migratory mesenchymal phenotype. Mechanistically, EMT occurs via a series of genetic and cellular events leading to the repression of epithelial-associated markers and upregulation of mesenchymal-associated markers. EMT is very crucial for many biological processes such as embryogenesis and ontogenesis during human development, and again it plays a significant role in wound healing during a programmed replacement of the damaged tissues. However, this process is often hijacked in pathological conditions such as tumour metastasis, which constitutes the most significant drawback in the fight against cancer, accounting for about 90% of cancer-associated mortality globally. Worse still, metastatic tumours are not only challenging to treat with the available conventional radiotherapy and surgical interventions but also resistant to several cytotoxic agents during treatment, owing to their anatomically diffuse localisation in the body system. As the quest to find an effective method of addressing metastasis in cancer intervention heightens, understanding the molecular interplay involving the signalling pathways, downstream effectors, and their interactions with the EMT would be an important requisite while the challenges of metastasis continue to punctuate. Unfortunately, the molecular underpinnings that govern this process remain to be completely illuminated. However, it is becoming increasingly clear that EMT, which initiates every episode of metastasis, significantly requires some master regulators called EMT transcription factors (EMT-TFs). Thus, this review critically examines the roles of TFs as drivers of molecular rewiring that lead to tumour initiation, progression, EMT, metastasis, and colonisation. In addition, it discusses the interaction of various signalling molecules and effector proteins with these factors. It also provides insight into promising therapeutic targets that may inhibit the metastatic process to overcome the limitation of “undruggable” cancer targets in therapeutic design and upturn the current spate of drug resistance. More so, it extends the discussion from the basic understanding of the EMT binary switch model, and ultimately unveiling the E/M cellular plasticity along a phenotypic spectrum via multiple trans-differentiations. It wraps up on how this knowledge update shapes the diagnostic and clinical approaches that may demand a potential shift in investigative paradigm using novel technologies such as single-cell analyses to improve overall patient survival.

RNA binding protein RBMS3 is a common EMT effector that modulates triple-negative breast cancer progression via stabilizing PRRX1 mRNA

The epithelial-to-mesenchymal transition (EMT) has been recognized as a driving force for tumor progression in breast cancer. Recently, our group identified the RNA Binding Motif Single Stranded Interacting Protein 3 (RBMS3) to be significantly associated with an EMT transcriptional program in breast cancer. Additional expression profiling demonstrated that RBMS3 was consistently upregulated by multiple EMT transcription factors and correlated with mesenchymal gene expression in breast cancer cell lines. Functionally, RBMS3 was sufficient to induce EMT in two immortalized mammary epithelial cell lines. In triple-negative breast cancer (TNBC) models, RBMS3 was necessary for maintaining the mesenchymal phenotype and invasion and migration in vitro. Loss of RBMS3 significantly impaired both tumor progression and spontaneous metastasis in vivo. Using a genome-wide approach to interrogate mRNA stability, we found that ectopic expression of RBMS3 upregulates many genes that are resistant to degradation following transcriptional blockade by actinomycin D (ACTD). Specifically, RBMS3 was shown to interact with the mRNA of EMT transcription factor PRRX1 and promote PRRX1 mRNA stability. PRRX1 is required for RBMS3-mediated EMT and is partially sufficient to rescue the effect of RBMS3 knockdown in TNBC cell lines. Together, this study identifies RBMS3 as a novel and common effector of EMT, which could be a promising therapeutic target for TNBC treatment.

Determinants of renal cell carcinoma invasion and metastatic competence

Metastasis is the principal cause of cancer related deaths. Tumor invasion is essential for metastatic spread. However, determinants of invasion are poorly understood. We addressed this knowledge gap by leveraging a unique attribute of kidney cancer. Renal tumors invade into large vessels forming tumor thrombi (TT) that migrate extending sometimes into the heart. Over a decade, we prospectively enrolled 83 ethnically-diverse patients undergoing surgical resection for grossly invasive tumors at UT Southwestern Kidney Cancer Program. In this study, we perform comprehensive histological analyses, integrate multi-region genomic studies, generate in vivo models, and execute functional studies to define tumor invasion and metastatic competence. We find that invasion is not always associated with the most aggressive clone. Driven by immediate early genes, invasion appears to be an opportunistic trait attained by subclones with diverse oncogenomic status in geospatial proximity to vasculature. We show that not all invasive tumors metastasize and identify determinants of metastatic competency. TT associated with metastases are characterized by higher grade, mTOR activation and a particular immune contexture. Moreover, TT grade is a better predictor of metastasis than overall tumor grade, which may have implications for clinical practice.

Heterogeneity in Pancreatic Cancer Fibroblasts-TGFβ as a Master Regulator?

Pancreatic ductal adenocarcinoma is an aggressive disease for which there are very few available therapies. It is notable for its high degree of tumour complexity, with the tumour microenvironment often accounting for the majority of the tumour volume. Until recently, the biology of the stroma was poorly understood, particularly in terms of heterogeneity. Recent research, however, has shed light on the intricacy of signalling within the stroma and particularly the molecular and functional heterogeneity of the cancer associated fibroblasts. In this review, we summarise the recent improvements in our understanding of the different fibroblast populations within PDAC, with a focus on the role TGFβ plays to dictate their formation and function. These studies have highlighted some of the reasons for the failure of trials targeting the tumour stroma, however, there are still considerable gaps in our knowledge, and more work is needed to make effective fibroblast targeting a reality in the clinic.

Stationed or Relocating: The Seesawing EMT/MET Determinants from Embryonic Development to Cancer Metastasis

Epithelial and mesenchymal transition mechanisms continue to occur during the cell cycle and throughout human development from the embryo stage to death. In embryo development, epithelial-mesenchymal transition (EMT) can be divided into three essential steps. First, endoderm, mesoderm, and neural crest cells form, then the cells are subdivided, and finally, cardiac valve formation occurs. After the embryonic period, the human body will be subjected to ongoing mechanical stress or injury. The formation of a wound requires EMT to recruit fibroblasts to generate granulation tissues, repair the wound and re-create an intact skin barrier. However, once cells transform into a malignant tumor, the tumor cells acquire the characteristic of immortality. Local cell growth with no growth inhibition creates a solid tumor. If the tumor cannot obtain enough nutrition in situ, the tumor cells will undergo EMT and invade the basal membrane of nearby blood vessels. The tumor cells are transported through the bloodstream to secondary sites and then begin to form colonies and undergo reverse EMT, the so-called "mesenchymal-epithelial transition (MET)." This dynamic change involves cell morphology, environmental conditions, and external stimuli. Therefore, in this manuscript, the similarities and differences between EMT and MET will be dissected from embryonic development to the stage of cancer metastasis.

Dynamic EMT: a multi-tool for tumor progression

The process of epithelial-mesenchymal transition (EMT) is fundamental for embryonic morphogenesis. Cells undergoing it lose epithelial characteristics and integrity, acquire mesenchymal features, and become motile. In cancer, this program is hijacked to confer essential changes in morphology and motility that fuel invasion. In addition, EMT is increasingly understood to orchestrate a large variety of complementary cancer features, such as tumor cell stemness, tumorigenicity, resistance to therapy and adaptation to changes in the microenvironment. In this review, we summarize recent findings related to these various classical and non-classical functions, and introduce EMT as a true tumorigenic multi-tool, involved in many aspects of cancer. We suggest that therapeutic targeting of the EMT process will-if acknowledging these complexities-be a possibility to concurrently interfere with tumor progression on many levels.

Dysregulated paired related homeobox 1 impacts on hepatocellular carcinoma phenotypes

BACKGROUND

Hepatocellular carcinoma (HCC) is a major cause of cancer-related death. Paired related homeobox 1 (PRRX1) is a transcription factor that regulates cell growth and differentiation, but its importance in HCC is unclear.

METHODS

We examined the expression pattern of PRRX1 in nine microarray datasets of human HCC tumour samples (n > 1100) and analyzed its function in HCC cell lines. In addition, we performed gene set enrichment, Kaplan-Meier overall survival analysis, metabolomics and functional assays.

RESULTS

PRRX1 is frequently upregulated in human HCC. Pathway enrichment analysis predicted a direct correlation between PRRX1 and focal adhesion and epithelial-mesenchymal transition. High expression of PRRX1 and low ZEB1 or high ZEB2 significantly predicted better overall survival in HCC patients. In contrast, metabolic processes correlated inversely and transcriptional analyses revealed that glycolysis, TCA cycle and amino acid metabolism were affected. These findings were confirmed by metabolomics analysis. At the phenotypic level, PRRX1 knockdown accelerated proliferation and clonogenicity in HCC cell lines.

CONCLUSIONS

Our results suggest that PRRX1 controls metabolism, has a tumour suppressive role, and may function in cooperation with ZEB1/2. These findings have functional relevance in HCC, including in understanding transcriptional control of distinct cancer hallmarks.

Single-cell lineage tracing of metastatic cancer reveals selection of hybrid EMT states

The underpinnings of cancer metastasis remain poorly understood, in part due to a lack of tools for probing their emergence at high resolution. Here we present macsGESTALT, an inducible CRISPR-Cas9-based lineage recorder with highly efficient single-cell capture of both transcriptional and phylogenetic information. Applying macsGESTALT to a mouse model of metastatic pancreatic cancer, we recover ∼380,000 CRISPR target sites and reconstruct dissemination of ∼28,000 single cells across multiple metastatic sites. We find that cells occupy a continuum of epithelial-to-mesenchymal transition (EMT) states. Metastatic potential peaks in rare, late-hybrid EMT states, which are aggressively selected from a predominately epithelial ancestral pool. The gene signatures of these late-hybrid EMT states are predictive of reduced survival in both human pancreatic and lung cancer patients, highlighting their relevance to clinical disease progression. Finally, we observe evidence for in vivo propagation of S100 family gene expression across clonally distinct metastatic subpopulations.

The Prognostic Value of the DNA Repair Gene Signature in Head and Neck Squamous Cell Carcinoma

Purpose

To construct a prognostic signature composed of DNA repair genes to effectively predict the prognosis of patients with head and neck squamous cell carcinoma (HNSCC).

Methods

After downloading the transcriptome and clinical data of HNSCC from the Cancer Genome Atlas (TCGA), 499 patients with HNSCC were equally divided into training and testing sets. In the training set, 13 DNA repair genes were screened using univariate proportional hazard (Cox) regression analysis and least absolute shrinkage and selection operator (LASSO) Cox regression analysis to construct a risk model, which was validated in the testing set.

Results

In the training and testing sets, there were significant differences in the clinical outcomes of patients in the high- and low-risk groups showed by Kaplan-Meier survival curves (P < 0.001). Univariate and multivariate Cox regression analyses showed that the risk score had independent prognostic predictive ability (P < 0.001). At the same time, the immune cell infiltration, immune score, immune-related gene expression, and tumor mutation burden (TMB) of patients with HNSCC were also different between the high- and low-risk groups (P < 0.05). Finally, we screened several chemotherapeutics for HNSCC, which showed significant differences in drug sensitivity between the high- and low-risk groups (P < 0.05).

Conclusion

This study constructed a 13-DNA-repair-gene signature for the prognosis of HNSCC, which could accurately and independently predict the clinical outcome of the patient. We then revealed the immune landscape, TMB, and sensitivity to chemotherapy drugs in different risk groups, which might be used to guide clinical treatment decisions.

The Regulatory Role of PRRX1 in Cancer Epithelial-Mesenchymal Transition

PRRX1 (paired related homeobox 1), a member of the paired homeobox family, exhibits an important role in tumor. It is closely correlated to the occurrence of epithelial-mesenchymal transition (EMT). PRRX1 is an important transcription factor regulating EMT and plays an important role in tumor progression. In the process of tumor metastasis, PRRX1 mainly regulates the occurrence of EMT in tumor cells through TGF-β signaling pathway, Wnt/β-catenin signaling pathway and Notch signaling pathway. PRRX1 is not only closely related to the tumor cell stemness but also involved in miRNA regulation of EMT. Therefore, PRRX1 may be a target for inhibiting the proliferation, metastasis and stemness of tumor cells. The current review provides a systemic profile of the regulatory role of PRRX1 in cancer epithelial-mesenchymal transition.

PRRX1 induced by BMP signaling decreases tumorigenesis by epigenetically regulating glioma-initiating cell properties via DNA methyltransferase 3A

Glioma‐initiating cells (GICs), a major source of glioblastoma recurrence, are characterized by the expression of neural stem cell markers and the ability to grow by forming nonadherent spheres under serum‐free conditions. Bone morphogenetic proteins (BMPs), members of the transforming growth factor‐β family, induce differentiation of GICs and suppress their tumorigenicity. However, the mechanisms underlying the BMP‐induced loss of GIC stemness have not been fully elucidated. Here, we show that paired related homeobox 1 (PRRX1) induced by BMPs decreases the CD133‐positive GIC population and inhibits tumorigenic activity of GICs in vivo. Of the two splice isoforms of PRRX1, the longer isoform, pmx‐1b, but not the shorter isoform, pmx‐1a, induces GIC differentiation. Upon BMP stimulation, pmx‐1b interacts with the DNA methyltransferase DNMT3A and induces promoter methylation of the PROM1 gene encoding CD133. Silencing DNMT3A maintains PROM1 expression and increases the CD133‐positive GIC population. Thus, pmx‐1b promotes loss of stem cell‐like properties of GICs through region‐specific epigenetic regulation of CD133 expression by recruiting DNMT3A, which is associated with decreased tumorigenicity of GICs.

Activation of COL11A1 by PRRX1 promotes tumor progression and radioresistance in ovarian cancer

PURPOSE

Although radiotherapy is a common treatment option for all kinds of cancer patients, including ovarian cancer, a major obstacle limiting its application in the development of resistance. Therefore, it is urgently needed to clarify the mechanism of radiosensitivity modulation.

MATERIALS AND METHODS

We obtained open datasets and analyzed the expression of collagen type XI alpha 1 (COL11A1) in ovarian cancer patients with different stages. Meanwhile, the correlation of COL11A1 and survival outcomes is determined by Kaplan-Meier analysis. The role of COL11A1 in cell proliferation was observed in an in vitro knockdown system. SKOV3 radioresistant cells were established to determine the role of COL11A1 on radioresistant in ovarian cancer.

RESULTS AND DISCUSSION

COL11A1 were highly enriched in late-stage ovarian cancer tumor tissues and negatively correlated with survival outcomes in ovarian cancer. The functional analysis found that COL11A1 promoted ovarian cancer cell proliferation in vitro. Importantly, COL11A1 decreased radiosensitivity in ovarian cancer by AKT activation. Paired related homeobox 1 (PRRX1) acted as an upstream transcription factor to regulate COL11A1 expression in ovarian cancer. Increased COL11A1 expression is related to low survival outcomes and radiosensitivity in ovarian cancer.

CONCLUSIONS

Targeting COL11A1 is a promising strategy for improving radiotherapy efficiency.

Tumor suppressive microRNA-485-5p targets PRRX1 in human skin melanoma cells, regulating epithelial-mesenchymal transition and apoptosis

Melanoma is one of the most aggressive skin cancers. Existing evidence has reported the aberrant expression of microRNAs (miRNAs) in melanoma, but their putative targets and underlying downstream effects remain to be further understood. Herein, we explored the suppressive role of miR-485-5p in melanoma progression. Initial bioinformatics analyses showed that the PRRX1 gene was differentially expressed in melanoma, while miR-485-5p was predicted to be a potential regulatory miRNA binding to PRRX1 mRNA. We confirmed that PRRX1 was upregulated, while miR-485-5p was downregulated in human melanoma samples compared with adjacent normal skin tissues. We then showed that PRRX1 was a target gene of miR-485-5p by dual-luciferase reporter gene assay. Moreover, a reduction in the expression of PRRX1 and downregulation of important proteins of the transforming growth factor-beta (TGFβ) signaling pathway was observed after miR-485-5p overexpression. Furthermore, miR-485-5p overexpression or PRRX1 knockdown suppressed epithelial-mesenchymal transition, cell viability, migration, and invasion, and promoted cell apoptosis in melanoma cells. Our study demonstrates the tumor-suppressive functions of miR-485-5p in the development of human melanoma, providing a potential target for therapy.

Epithelial-to-mesenchymal-like transition events in melanoma

Epithelial-to-mesenchymal transition (EMT), a process through which epithelial tumor cells acquire mesenchymal phenotypic properties, contributes to both metastatic dissemination and therapy resistance in cancer. Accumulating evidence indicates that nonepithelial tumors, including melanoma, can also gain mesenchymal-like properties that increase their metastatic propensity and decrease their sensitivity to therapy. In this review, we discuss recent findings, illustrating the striking similarities-but also knowledge gaps-between the biology of mesenchymal-like state(s) in melanoma and mesenchymal state(s) from epithelial cancers. Based on this comparative analysis, we suggest hypothesis-driven experimental approaches to further deepen our understanding of the EMT-like process in melanoma and how such investigations may pave the way towards the identification of clinically relevant biomarkers for prognosis and new therapeutic strategies.

LIN28B induces a differentiation program through CDX2 in colon cancer

Most colorectal cancers (CRCs) are moderately differentiated or well differentiated, a status that is preserved even in metastatic tumors. However, the molecular mechanisms underlying CRC differentiation remain to be elucidated. Herein, we unravel a potentially novel posttranscriptional regulatory mechanism via a LIN28B/CDX2 signaling axis that plays a critical role in mediating CRC differentiation. Owing to a large number of mRNA targets, the mRNA-binding protein LIN28B has diverse functions in development, metabolism, tissue regeneration, and tumorigenesis. Our RNA-binding protein IP (RIP) assay revealed that LIN28B directly binds CDX2 mRNA, which is a pivotal homeobox transcription factor in normal intestinal epithelial cell identity and differentiation. Furthermore, LIN28B overexpression resulted in enhanced CDX2 expression to promote differentiation in subcutaneous xenograft tumors generated from CRC cells and metastatic tumor colonization through mesenchymal-epithelial transition in CRC liver metastasis mouse models. A ChIP sequence for CDX2 identified α-methylacyl-CoA racemase (AMACR) as a potentially novel transcriptional target of CDX2 in the context of LIN28B overexpression. We also found that AMACR enhanced intestinal alkaline phosphatase activity, which is known as a key component of intestinal differentiation, through the upregulation of butyric acid. Overall, we demonstrated that LIN28B promotes CRC differentiation through the CDX2/AMACR axis.

Epithelial-mesenchymal transition: When tumor cells meet myeloid-derived suppressor cells

Myeloid-derived suppressor cells (MDSCs) are a heterogeneous myeloid cell population characterized by protumoral functions in the tumor immune network. An increasing number of studies have focused on the biological functions of MDSCs in tumor immunity. Epithelial-mesenchymal transition (EMT) is a cellular plasticity process accompanied by a loss of epithelial phenotypes and an acquisition of mesenchymal phenotypes. In general, tumor cells that undergo EMT are more likely to invade and metastasize. Recently, extensive evidence suggests that EMT is closely related to a highly immunosuppressive environment. This review will summarize the immunosuppressive capacities of MDSC subsets and their distinct role in tumor EMT and further discuss immunotherapy for tumor EMT by targeting MDSCs.

From Proteomic Mapping to Invasion-Metastasis-Cascade Systemic Biomarkering and Targeted Drugging of Mutant BRAF-Dependent Human Cutaneous Melanomagenesis

Simple Summary

Despite the recent advances in human malignancy therapy, metastasis and chemoresistance remain the principal causes of cancer-derived deaths. Given the fatal forms of cutaneous metastatic melanoma, we herein employed primary (WM115) and metastatic (WM266-4) melanoma cells, both obtained from the same patient, to identify novel biomarkers and therapeutic agents. Through state-of-the-art technologies including deep proteome landscaping, immunofluorescence phenotyping, and drug toxicity screening, we were able to describe new molecular programs, oncogenic drivers, and drug regimens, controlling the invasion-metastasis cascade during BRAF^V600D-dependent melanomagenesis. It proved that proteomic navigation could foster the development of systemic biomarkering and targeted drugging for successful treatment of advanced disease.

Abstract

Melanoma is classified among the most notoriously aggressive human cancers. Despite the recent progress, due to its propensity for metastasis and resistance to therapy, novel biomarkers and oncogenic molecular drivers need to be promptly identified for metastatic melanoma. Hence, by employing nano liquid chromatography-tandem mass spectrometry deep proteomics technology, advanced bioinformatics algorithms, immunofluorescence, western blotting, wound healing protocols, molecular modeling programs, and MTT assays, we comparatively examined the respective proteomic contents of WM115 primary (n = 3955 proteins) and WM266-4 metastatic (n = 6681 proteins) melanoma cells. It proved that WM115 and WM266-4 cells have engaged hybrid epithelial-to-mesenchymal transition/mesenchymal-to-epithelial transition states, with TGF-β controlling their motility in vitro. They are characterized by different signatures of SOX-dependent neural crest-like stemness and distinct architectures of the cytoskeleton network. Multiple signaling pathways have already been activated from the primary melanoma stage, whereas HIF1α, the major hypoxia-inducible factor, can be exclusively observed in metastatic melanoma cells. Invasion-metastasis cascade-specific sub-routines of activated Caspase-3-triggered apoptosis and LC3B-II-dependent constitutive autophagy were also unveiled. Importantly, WM115 and WM266-4 cells exhibited diverse drug response profiles, with epirubicin holding considerable promise as a beneficial drug for metastatic melanoma clinical management. It is the proteome navigation that enables systemic biomarkering and targeted drugging to open new therapeutic windows for advanced disease.

Molecular pathology underlying the robustness of cancer stem cells

Intratumoral heterogeneity is tightly associated with the failure of anticancer treatment modalities including conventional chemotherapy, radiation therapy, and molecularly targeted therapy. Such heterogeneity is generated in an evolutionary manner not only as a result of genetic alterations but also by the presence of cancer stem cells (CSCs). CSCs are proposed to exist at the top of a tumor cell hierarchy and are undifferentiated tumor cells that manifest enhanced tumorigenic and metastatic potential, self-renewal capacity, and therapeutic resistance. Properties that contribute to the robustness of CSCs include the abilities to withstand redox stress, to rapidly repair damaged DNA, to adapt to a hyperinflammatory or hyponutritious tumor microenvironment, and to expel anticancer drugs by the action of ATP-binding cassette transporters as well as plasticity with regard to the transition between dormant CSC and transit-amplifying progenitor cell phenotypes. In addition, CSCs manifest the phenomenon of metabolic reprogramming, which is essential for maintenance of their self-renewal potential and their ability to adapt to changes in the tumor microenvironment. Elucidation of the molecular underpinnings of these biological features of CSCs is key to the development of novel anticancer therapies. In this review, we highlight the pathological relevance of CSCs in terms of their hallmarks and identification, the properties of their niche—both in primary tumors and at potential sites of metastasis—and their resistance to oxidative stress dependent on system xc (−).

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Intratumoral heterogeneity driven by CSCs is responsible for therapeutic resistance.

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CTCs survive in the distant organs and achieve colonization, causing metastasis.

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E/M hybrid cancer cells due to partial EMT exhibit the highest metastatic potential.

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The CSC niche regulates stemness in metastatic disease as well as in primary tumor.

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Activation of system xc(-) by CD44 variant in CSCs is a promising therapeutic target.

Silencing of FTX suppresses pancreatic cancer cell proliferation and invasion by upregulating miR-513b-5p

BACKGROUND

Abnormal expression of long non-coding RNA (lncRNA) FTX (five prime to Xist), which is involved in X chromosome inactivation, has been reported in various tumors. However, the effect of FTX on the development of pancreatic cancer (PC) has not been elucidated. The purpose of this study was to explore the possible molecular mechanism of FTX in PC.

METHODS

Quantitative real-time PCR (qRT-PCR) was used to measure the expression levels of FTX and miR-513b-5p in PC cell lines. Proliferation and apoptosis of PC cells were determined by CCK-8, Edu assay, and flow cytometry. Invasion and migration ability of PC cells were detected by Transwell assay and scratch test. Bioinformatics analysis, luciferase reporter gene assay, and RNA immunoprecipitation (RIP) assay were used to verify the direct binding between FTX and miR-513b-5p. The xenotransplantation mouse model was established to explore the effect of FTX and miR-513b-5p on the PC tumor growth in vivo.

RESULTS

The expression levels of FTX were increased in PC cell lines, and silencing of FTX remarkably suppressed the invasion ability and cell viability. Besides, FTX could bind to miR-513b-5p as a competitive endogenous RNA, thus promoting the invasion and proliferation ability of PC cells. Moreover, knockdown of FTX inhibited the tumor growth and increased the expression levels of miR-513b-5p and apoptosis-related proteins in vivo.

CONCLUSIONS

FTX could directly combine with miR-513b-5p as a competitive endogenous RNA, thus promoting the occurrence and development of PC in vitro and in vivo.

Expression and clinical significance of paired- related homeobox 1 and Smad2 in gastric cancer

BACKGROUND

China has a high incidence rate and low survival rate of gastric cancer. Therefore, there is a great need to further identify novel oncogenes and clinically applicable molecular targets for the diagnosis and treatment of this disease.

METHODS

Expressions of PRRX1, Smad2, epithelial phenotype marker E-cadherin, and interstitial phenotype vimentin protein in a sample of 64 gastric carcinoma and adjacent nontumorous tissues were detected by immunohistochemistry. Their relationship and correlations with clinicopathological features were analyzed.

RESULTS

The positive rates of PRRX1, Smad2, E-cadherin, and vimentin protein in primary tumors were 60.94% (39/64), 59.38% (38/64), 34.38%(22/64), and 64.06% (41/64), respectively. A significant correlation was found among the expression of PRRX1, Smad2, E-cadherin, and vimentin (P < 0.05). Expression of the PRRX1, Smad2, and vimentin protein in gastric cancer tissue was correlated with Borrmann classification, lymph node-positive number, the degree of differentiation, depth of tumor invasion, and serum pepsinogen I (PGI) level (P < 0.05), but not with age, sex, serum carcinoembryonic antigen, serum CA199, or PGI/PGII (P > 0.05).

CONCLUSION

The positive rate of PRRX1 protein expression was positively correlated with the protein expression of Smad2 and vimentin, but negatively correlated with E-cadherin protein. PRRX1, Smad2, and vimentin proteins are associated with Borrmann type, lymph node positives, histologic grade, depth of tumor invasion, and serum PGI levels, all of which contribute to a poor prognosis for patients with gastric cancer.

Targeting and Reprograming Cancer-Associated Fibroblasts and the Tumor Microenvironment in Pancreatic Cancer

Pancreatic cancer is the fourth leading cause of cancer deaths in the United States both in female and male, and is projected to become the second deadliest cancer by 2030. The overall five-year survival rate remains at around 10%. Pancreatic cancer exhibits a remarkable resistance to established therapeutic options such as chemotherapy and radiotherapy, due to dense stromal tumor microenvironment. Cancer-associated fibroblasts are the major stromal cell type and source of extracellular matrix proteins shaping a physical and metabolic barrier thereby reducing therapeutic efficacy. Targeting cancer-associated fibroblasts has been considered a promising therapeutic strategy. However, depleting cancer-associated fibroblasts may also have tumor-promoting effects due to their functional heterogeneity. Several subtypes of cancer-associated fibroblasts have been suggested to exhibit tumor-restraining function. This review article summarizes recent preclinical and clinical investigations addressing pancreatic cancer therapy through targeting specific subtypes of cancer-associated fibroblasts, deprogramming activated fibroblasts, administration of mesenchymal stem cells, as well as reprogramming tumor-promoting cancer-associated fibroblasts to tumor-restraining cancer-associated fibroblasts. Further, inter-cellular mediators between cancer-associated fibroblasts and the surrounding tissue microenvironment are discussed. It is important to increase our understanding of cancer-associated fibroblast heterogeneity and the tumor microenvironment for more specific and personalized therapies for pancreatic cancer patients in the future.

Heparanome-Mediated Rescue of Oligodendrocyte Progenitor Quiescence following Inflammatory Demyelination

The proinflammatory cytokine IFN-γ, which is chronically elevated in multiple sclerosis, induces pathologic quiescence in human oligodendrocyte progenitor cells (OPCs) via upregulation of the transcription factor PRRX1. In this study using animals of both sexes, we investigated the role of heparan sulfate proteoglycans in the modulation of IFN-γ signaling following demyelination. We found that IFN-γ profoundly impaired OPC proliferation and recruitment following adult spinal cord demyelination. IFN-γ-induced quiescence was mediated by direct signaling in OPCs as conditional genetic ablation of IFNγR1 (Ifngr1) in adult NG2⁺ OPCs completely abrogated these inhibitory effects. Intriguingly, OPC-specific IFN-γ signaling contributed to failed oligodendrocyte differentiation, which was associated with hyperactive Wnt/Bmp target gene expression in OPCs. We found that PI-88, a heparan sulfate mimetic, directly antagonized IFN-γ to rescue human OPC proliferation and differentiation in vitro and blocked the IFN-γ-mediated inhibitory effects on OPC recruitment in vivo Importantly, heparanase modulation by PI-88 or OGT2155 in demyelinated lesions rescued IFN-γ-mediated axonal damage and demyelination. In addition to OPC-specific effects, IFN-γ-augmented lesions were characterized by increased size, reactive astrogliosis, and proinflammatory microglial/macrophage activation along with exacerbated axonal injury and cell death. Heparanase inhibitor treatment rescued many of the negative IFN-γ-induced sequelae suggesting a profound modulation of the lesion environment. Together, these results suggest that the modulation of the heparanome represents a rational approach to mitigate the negative effects of proinflammatory signaling and rescuing pathologic quiescence in the inflamed and demyelinated human brain.SIGNIFICANCE STATEMENT The failure of remyelination in multiple sclerosis contributes to neurologic dysfunction and neurodegeneration. The activation and proliferation of oligodendrocyte progenitor cells (OPCs) is a necessary step in the recruitment phase of remyelination. Here, we show that the proinflammatory cytokine interferon-γ directly acts on OPCs to induce pathologic quiescence and thereby limit recruitment following demyelination. Heparan sulfate is a highly structured sulfated carbohydrate polymer that is present on the cell surface and regulates several aspects of the signaling microenvironment. We find that pathologic interferon-γ can be blocked by modulation of the heparanome following demyelination using either a heparan mimetic or by treatment with heparanase inhibitor. These studies establish the potential for modulation of heparanome as a regenerative approach in demyelinating disease.

Mesenchymal Plasticity Regulated by Prrx1 Drives Aggressive Pancreatic Cancer Biology

BACKGROUND & AIMS

Pancreatic ductal adenocarcinoma (PDAC) is characterized by a fibroblast-rich desmoplastic stroma. Cancer-associated fibroblasts (CAFs) have been shown to display a high degree of interconvertible states including quiescent, inflammatory, and myofibroblastic phenotypes; however, the mechanisms by which this plasticity is achieved are poorly understood. Here, we aim to elucidate the role of CAF plasticity and its impact on PDAC biology.

METHODS

To investigate the role of mesenchymal plasticity in PDAC progression, we generated a PDAC mouse model in which CAF plasticity is modulated by genetic depletion of the transcription factor Prrx1. Primary pancreatic fibroblasts from this mouse model were further characterized by functional in vitro assays. To characterize the impact of CAFs on tumor differentiation and response to chemotherapy, various coculture experiments were performed. In vivo, tumors were characterized by morphology, extracellular matrix composition, and tumor dissemination and metastasis.

RESULTS

Our in vivo findings showed that Prrx1-deficient CAFs remain constitutively activated. Importantly, this CAF phenotype determines tumor differentiation and disrupts systemic tumor dissemination. Mechanistically, coculture experiments of tumor organoids and CAFs showed that CAFs shape the epithelial-to-mesenchymal phenotype and confer gemcitabine resistance of PDAC cells induced by CAF-derived hepatocyte growth factor. Furthermore, gene expression analysis showed that patients with pancreatic cancer with high stromal expression of Prrx1 display the squamous, most aggressive, subtype of PDAC.

CONCLUSIONS

Here, we define that the Prrx1 transcription factor is critical for tuning CAF activation, allowing a dynamic switch between a dormant and an activated state. This work shows that Prrx1-mediated CAF plasticity has significant impact on PDAC biology and therapeutic resistance.

PRRX1 promotes malignant properties in human osteosarcoma

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PRRX1 is a poor-prognosis marker of human osteosarcoma.

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PRRX1 promotes proliferation, invasion, and drug resistance in human osteosarcoma.

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Forskolin was identified using RNA expression signatures of PRRX1 knockdown.

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Forskolin decreased proliferation and migration in human osteosarcoma.

Paired related homeobox 1 (PRRX1) is a marker of limb bud mesenchymal cells, and deficiency of p53 or Rb in Prrx1-positive cells induces osteosarcoma in several mouse models. However, the regulatory roles of PRRX1 in human osteosarcoma have not been defined. In this study, we performed PRRX1 immunostaining on 35 human osteosarcoma specimens to assess the correlation between PRRX1 level and overall survival. In patients with osteosarcoma, the expression level of PRRX1 positively correlated with poor prognosis or the ratio of lung metastasis. Additionally, we found PRRX1 expression on in 143B cells, a human osteosarcoma line with a high metastatic capacity. Downregulation of PRRX1 not only suppressed proliferation and invasion but also increased the sensitivity to cisplatin and doxorubicin. When 143B cells were subcutaneously transplanted into nude mice, PRRX1 knockdown decreased tumor sizes and rates of lung metastasis. Interestingly, forskolin, a chemical compound identified by Connectivity Map analysis using RNA expression signatures during PRRX1 knockdown, decreased tumor proliferation and cell migration to the same degree as PRRX1 knockdown. These results demonstrate that PRRX1 promotes tumor malignancy in human osteosarcoma.

Sphingosine-1-phosphate Receptor-1 Promotes Vascular Invasion and EMT in Hepatocellular Carcinoma

BACKGROUND

It remains unknown whether epithelial-mesenchymal transition (EMT)-mediated vascular invasion and cancer stemness are associated with sphingosine-1-phosphate receptor-1 (S1PR1) expression in human hepatocellular carcinoma (HCC). The aim of this study was to investigate the correlation between S1PR1 expression and prognosis of patients with primary HCC and to define the potential of S1PR as a therapeutic target.

MATERIALS AND METHODS

We investigated 108 patients who underwent primary surgical resection for HCC treatment. Expression of S1PR1 and EMT markers was analyzed to predict prognosis of patients with HCC. Furthermore, three-dimensional organotypic culture, anoikis assay, and cell invasion were performed to validate the association of S1PR1 with EMT and cancer stemness.

RESULTS

Among patients with HCC, the high S1PR1 expression group had significantly shorter overall survival than the low expression group. Moreover, high S1PR1 expression was significantly associated with shorter recurrence-free survival, increased risk of portal and hepatic vein invasion, and intrahepatic metastasis. Multivariate analyses revealed that S1PR1 overexpression was an independent prognostic factor in patients with HCC. S1PR1 overexpression positively correlated with vimentin and MMP-9 expression and negatively correlated with E-cadherin. In addition, S1PR1 overexpression induced EMT and enhanced tumor invasion and cancer stemness.

CONCLUSIONS

S1PR1 overexpression, via EMT-induced vascular invasion and increased cancer stem cell properties, establishes a metastatic niche, enhances the capacity of hematogenous metastasis, and associates with poor outcomes in patients with HCC. Hence, S1PR1 may serve as a therapeutic target for patients with HCC with vascular invasion.

COL6A3 expression in adipose tissue cells is associated with levels of the homeobox transcription factor PRRX1

Fibrillar collagen COL6α3 in adipose tissue has been associated with obesity, inflammation, insulin resistance and cancer. We here aimed to identify novel transcriptional regulators of COL6A3 expression. Based on a transcriptome dataset of adipose tissue, we identified strong correlations for 56 genes with COL6A3 mRNA, including targets of TGF-β/SMAD signaling. Among the identified candidates, the homeobox transcription factor PRRX1 showed a particularly striking co-expression with COL6A3, validated across several different cohorts, including patients with extreme obesity, insulin sensitive and resistant obesity (subcutaneous and omental), after profound fat loss (subcutaneous), and lean controls (subcutaneous). In human and mouse adipose cells, PRRX1 knockdown reduced COL6A3 mRNA and PRRX1 overexpression transactivated a reporter construct with the endogenous human COL6A3 promoter. Stable PRRX1 overexpression in 3T3-L1 cells induced Col6a3 mRNA threefold specifically after adipogenic induction, whereas TGF-β1 treatment upregulated Col6a3 mRNA also in the preadipocyte state. Interestingly, pro-inflammatory stimulus (i.e., TNF-α treatment) decreased PRRX1-mediated Col6a3 transactivation and mRNA expression, supporting a role for this mechanism in the regulation of adipose tissue inflammation. In conclusion, we identified the homeobox factor PRRX1 as a novel transcriptional regulator associated with COL6A3 expression, providing new insight into the regulatory mechanisms of altered adipose tissue function in obesity and insulin resistance.

Functional balance between Tcf21-Slug defines cellular plasticity and migratory modalities in high grade serous ovarian cancer cell lines

Cellular plasticity and transitional phenotypes add to complexities of cancer metastasis that can be initiated by single cell epithelial to mesenchymal transition (EMT) or cooperative cell migration (CCM). Our study identifies novel regulatory cross-talks between Tcf21 and Slug in mediating phenotypic and migration plasticity in high-grade serous ovarian adenocarcinoma (HGSC). Differential expression and subcellular localization associate Tcf21, Slug with epithelial, mesenchymal phenotypes, respectively; however, gene manipulation approaches identify their association with additional intermediate phenotypic states, implying the existence of a multistep epithelial-mesenchymal transition program. Live imaging further associated distinct migratory modalities with the Tcf21/Slug status of cell systems and discerned proliferative/passive CCM, active CCM and EMT modes of migration. Tcf21-Slug balance identified across a phenotypic spectrum in HGSC cell lines, associated with microenvironment-induced transitions and the emergence of an epithelial phenotype following drug exposure. Phenotypic transitions and associated functionalities following drug exposure were affirmed to ensue from occupancy of Slug promoter E-box sequences by Tcf21. Our study effectively provides a framework for understanding the relevance of ovarian cancer plasticity as a function of two transcription factors.