Snail mediates invasion through uPA/uPAR and the MAPK signaling pathway in prostate cancer cells

LPAR5 confers radioresistance to cancer cells associated with EMT activation via the ERK/Snail pathway

BACKGROUND

Epithelial-to-mesenchymal transition (EMT) is a critical event contributing to more aggressive phenotypes in cancer cells. EMT is frequently activated in radiation-targeted cells during the course of radiotherapy, which often endows cancers with acquired radioresistance. However, the upstream molecules driving the signaling pathways of radiation-induced EMT have not been fully delineated.

METHODS

In this study, RNA-seq-based transcriptome analysis was performed to identify the early responsive genes of HeLa cells to γ-ray irradiation. EMT-associated genes were knocked down by siRNA technology or overexpressed in HeLa cells and A549 cells, and the resulting changes in phenotypes of EMT and radiosensitivity were assessed using qPCR and Western blotting analyses, migration assays, colony-forming ability and apoptosis of flow cytometer assays.

RESULTS

Through RNA-seq-based transcriptome analysis, we found that LPAR5 is downregulated in the early response of HeLa cells to γ-ray irradiation. Radiation-induced alterations in LPAR5 expression were further revealed to be a bidirectional dynamic process in HeLa and A549 cells, i.e., the early downregulating phase at 2 ~ 4 h and the late upregulating phase at 24 h post-irradiation. Overexpression of LPAR5 prompts EMT programing and migration of cancer cells. Moreover, increased expression of LPAR5 is significantly associated with IR-induced EMT and confers radioresistance to cancer cells. Knockdown of LPAR5 suppressed IR-induced EMT by attenuating the activation of ERK signaling and downstream Snail, MMP1, and MMP9 expression.

CONCLUSIONS

LPAR5 is an important upstream regulator of IR-induced EMT that modulates the ERK/Snail pathway. This study provides further insights into understanding the mechanism of radiation-induced EMT and identifies promising targets for improving the effectiveness of cancer radiation therapy.

Small interfering RNA targeting N-cadherin regulates cell proliferation and migration in enzalutamide-resistant prostate cancer

Enzalutamide is one of the options for treating patients with castration-resistant or metastatic prostate cancer. However, a substantial proportion of patients become resistant to enzalutamide after a period of treatment. Cells in these tumors typically exhibit increased proliferative and migratory capabilities, in which N-cadherin (CDH2) appear to serve an important role. In the present study, by up- and downregulating the expression of CDH2, the possible effects of CDH2 on the prostate cancer cell line LNCaP were investigated. Male sex hormone-sensitive LNCaP cells treated with 10 µM enzalutamide were named LNCaP enzalutamide-resistant (EnzaR) cells. Reverse transcription-PCR, western blotting and immunofluorescence staining were used to measure CDH2, E-cadherin, α-SMA, Snail and Slug expression. Transfection with the pCMV-CDH2 plasmid was performed for CDH2 upregulation, whilst transfection with small interfering RNA (siRNA)-CDH2 was performed for CDH2 downregulation. MTT and Cell Counting Kit-4 assays were used to evaluate the proportion of viable cancer cells. Subsequently, gap closure assay was performed to evaluate the migratory capability of both LNCaP and LNCaP EnzaR cell lines. CDH2 expression was found to be increased in LNCaP EnzaR cells compared with that in LNCaP cells. CDH2 overexpression increased cell viability and migration in both LNCaP and LNCaP EnzaR cell lines. By contrast, the opposite trend was observed after CDH2 expression was knocked down. CDH2 expression also showed a high association with that of four epithelial-mesenchymal transition markers, which was confirmed by western blotting. Based on these results, it was concluded that knocking down CDH2 expression using siRNA transfection mediated significant influence on LNCaP EnzaR cell physiology, which may be a potential therapeutic option for prostate cancer treatment.

Studies of hormonal regulation, phenotype plasticity, bone metastasis, and experimental therapeutics in androgen-repressed human prostate cancer (ARCaP) model

First established by Dr. Leland W. K. Chung's lab, the androgen-repressed prostate cancer cell (ARCaP) line is derived from the ascitic fluid of a prostate cancer (PCa) patient with widely metastatic disease. Based on its unique characteristic of growth suppression in the presence of androgen, ARCaP cell line has contributed to the research of PCa disease progression toward therapy- and castration-resistant PCa (t-CRPC). It has been widely applied in studies exploring experimental therapeutic reagents including Genistein, Vorinostat and Silibinin. ARCaP cells have showed increased metastatic potential to the bone and soft tissues. In addition, accumulating studies using ARCaP model have demonstrated the epithelial-to-mesenchymal transitional plasticity of PCa using epithelial-like ARCaP_E line treated in vitro with growth factors derived from bone microenvironment. The resulting mesenchymal-like ARCaP_M sub-clone derived from bone-metastasized tumor has high expression of several factors correlated with cancer metastasis, such as N-Cadherin, Vimentin, MCM3, Granzyme B, β2-microglobulin and RANKL. In particular, the increased secretion of RANKL in ARCaP_M further facilitates its capacity of inducing osteoclastogenesis at the bone microenvironment, leading to bone resorption and tumor colonization. Meanwhile, sphingosine kinase 1 (SphK1) acts as a key molecule driver in the neuroendocrine differentiation (NED) of ARCaP sublines, suggesting the unique facet of ARCaP cells for insightful studies in more malignant neuroendocrine prostate cancer (NEPC). Overall, the establishment of ARCaP line has provided a valuable model to explore the mechanisms underlying PCa progression toward metastatic t-CRPC. In this review, we will focus on the contribution of ARCaP model in PCa research covering hormone receptor activity, skeletal metastasis, plasticity of epithelial-to-mesenchymal transition (EMT) and application of therapeutic strategies.

Downregulation of Snail by DUSP1 Impairs Cell Migration and Invasion through the Inactivation of JNK and ERK and Is Useful as a Predictive Factor in the Prognosis of Prostate Cancer

Dual specificity phosphatase 1 (DUSP1) is crucial in prostate cancer (PC), since its expression is downregulated in advanced carcinomas. Here, we investigated DUSP1 effects on the expression of mesenchymal marker Snail, cell migration and invasion, analyzing the underlying mechanisms mediated by mitogen-activated protein kinases (MAPKs) inhibition. To this purpose, we used different PC cells overexpressing or lacking DUSP1 or incubated with MAPKs inhibitors. Moreover, we addressed the correlation of DUSP1 expression with Snail and activated MAPKs levels in samples from patients diagnosed with benign hyperplasia or prostate carcinoma, studying its implication in tumor prognosis and survival. We found that DUSP1 downregulates Snail expression and impairs migration and invasion in PC cells. Similar results were obtained following the inhibition of c-Jun N-terminal kinase (JNK) and extracellular-signal-regulated kinase (ERK). In clinical samples, we evidenced an inverse correlation between DUSP1 expression and Snail levels, which are further associated with JNK and ERK activation. Consequently, the pattern DUSP1_high/activated JNK_low/activated ERK_low/Snail_low is associated with an overall extended survival of PC patients. In summary, the ratio between DUSP1 and Snail expression, with additional JNK and ERK activity measurement, may serve as a potential biomarker to predict the clinical outcome of PC patients. Furthermore, DUSP1 induction or inhibition of JNK and ERK pathways could be useful to treat PC.

Downregulation of uPAR promotes urokinase translocation into the nucleus and epithelial to mesenchymal transition in neuroblastoma

The urokinase system is involved in a variety of physiological processes, such as fibrinolysis, matrix remodeling, wound healing, and regeneration. Upon binding to its cognate receptor urokinase‐type plasminogen activator receptor (uPAR), urokinase‐type plasminogen activator (uPA) catalyzes the conversion of plasminogen to plasmin and the activation of matrix metalloproteases. Apart from this, uPA–uPAR interaction can lead to the activation of transcription factors, mitogen‐activated protein kinase signaling pathways and RTK cascades. Elevated expression of uPA and uPAR is markedly associated with cancer progression and metastasis and correlates with a poor prognosis in clinics. Targeting the urokinase system has proved to be effective in experimental models in vitro and in vivo, however, in clinics the inhibition of the uPA/uPAR system has fallen short of expectations, suggesting that the question of the functional relevance of uPA/uPAR system is far from being moot. Recently, using CRISPR/Cas9 technology, we have shown that uPAR knockout decreases the proliferation of neuroblastoma Neuro2a cells in vitro. In the present study we demonstrate that uPAR expression is essential for maintaining the epithelial phenotype in Neuro2a cells and that uPAR silencing promotes epithelial‐mesenchymal transition (EMT) and increased cell migration. Accordingly, uPAR knockout results in the downregulation of epithelial markers (E‐cadherin, occludin, and claudin‐5) and in the increase of mesenchymal markers (N‐cadherin, α‐smooth muscle actin, and interleukin‐6). In search of the molecular mechanism underlying these changes, we identified uPA as a key component. Two key insights emerged as a result of this work: in the absence of uPAR, uPA is translocated into the nucleus where it is presumably involved in the activation of transcription factors (nuclear factor κB and Snail) resulting in EMT. In uPAR‐expressing cells, uPAR functions as a uPA “trap” that binds uPA on the cell surface and promotes controlled uPA internalization and degradation in lysosomes.

A Circulating Bioreactor Reprograms Cancer Cells Toward a More Mesenchymal Niche

Cancer is a complex and heterogeneous disease, and cancer cells dynamically interact with the mechanical microenvironment such as hydrostatic pressure, fluid shear, and interstitial flow. These factors play an essential role in cell fate and circulating tumor cell heterogeneity, and can influence the cellular phenotype. In this study, a peristaltic continuous flow reactor is designed and applied to HCT-116 colorectal carcinoma cells to mimic the fluid dynamics of circulation. With this intervention, a CD44/CD24-cell subpopulation emerges, and 100 genes are significantly regulated. The expression of cells at 4 h in the flow reactor is very similar to TGF-ß treatment, which is an inducer of epithelial-mesenchymal transition. ATF3 and SERPINE1 are significantly upregulated in these groups, suggesting that the mesenchymal transition is induced through this signaling pathway. This flow reactor model is satisfactory on its own to reprogram colorectal cancer cells toward a more mesenchymal niche mimicking circulation of the blood.

Sumoylation of Flotillin-1 promotes EMT in metastatic prostate cancer by suppressing Snail degradation

Flotillin-1 (Flot-1) has been shown to regulate cancer progression, but the regulatory role of post-translational modifications of Flot-1 on cancers remains elusive. Herein, we show that up-regulated E2 conjugating enzyme UBC9 sumoylates Flot-1 at Lys-51 and Lys-195 with small ubiquitin-like modifier (SUMO)-2/3 modification in metastatic prostate cancer. Mitogen induced the sumoylation and nuclear translocation of Flot-1. The nuclear-targeted Flot-1 physically interacted with Snail, and inhibited Snail degradation through the proteasome in a sumoylation-dependent manner, thereby promoting epithelial-to-mesenchymal transition (EMT). Sumoylation of Flot-1 by up-regulated UBC9 in human metastatic prostate cancer tissues and prostate cancer cells with high metastatic potential positively correlated with the stabilization of Snail and the induction of Snail-mediated EMT genes in the metastatic prostate cancer. Our study reveals a new mechanism of sumoylated Flot-1-mediating Snail stabilization, and identifies a novel sumoylated Flot-1-Snail signaling axis in EMT of metastatic prostate cancer.

High expression of uPA related to p38MAPK in esophageal cancer indicates poor prognosis

Background

The aim of the study was to investigate the relationship between urokinase-type plasminogen activator (uPA) and mitogen-activated protein kinase 38 (p38MAPK), and preliminarily analyze their relationship with clinical characteristics of esophageal cancer.

Materials and methods

Immunohistochemistry and Western blot were used to detect the expressions of uPA and p38MAPK in patients with esophageal cancer. The relationship between them and clinicopathological features was analyzed by chi-squared test and Spearman correlation. Prognosis was performed using Kaplan–Meier and Cox proportional hazard models analysis.

Results

The expressions of uPA and p38MAPK proteins were significantly higher in esophageal squamous cell carcinoma or adenocarcinoma than in normal esophageal mucosa tissue (both P<0.0001). The expression of uPA was significantly correlated with the depth of invasion of esophageal cancer (P=0.0067), tumor size (P=0.0364), and pathological stage (P<0.0001); p38MAPK expression vs esophageal cancer tissue type (P=0.0043), esophageal cancer infiltration depth (P=0.0097), tumor size (P=0.0015), and pathological stage (P<0.0001). Both were not significantly associated with lymph node staging, gender, age, and esophageal cancer histological type. There was a positive correlation between uPA and p38MAPK expressions (r=0.7301, P=0.0104). Kaplan–Meier analysis showed that the overall survival time of patients with positive expression of uPA or p38MAPK protein was significantly shorter, and the time of recurrence or metastasis of esophageal cancer was significantly earlier in patients with uPA-positive expression. Multivariate analysis of Cox model showed that uPA, p38MAPK, and pathological staging were independent factors influencing survival.

Conclusion

The expressions of uPA and p38MAPK may play an important role in the progression of esophageal cancer, and there is a close relationship between the two proteins, which may be one of the prognostic indicators.

Silencing of uPAR via RNA interference inhibits invasion and migration of oral tongue squamous cell carcinoma

Overexpression of urokinase-type plasminogen activator receptor (uPAR) has been implicated in promoting tumor invasion in various cancer types, including oral tongue squamous cell carcinoma (OTSCC); therefore, the effect of suppressing uPAR expression on the invasive and metastatic potential of OTSCC was investigated. A total of 65 paraffin-embedded tissues were obtained from patients with OTSCC. Immunohistochemistry was used to determine the expression level of uPAR. The Ts cells transfected with short hairpin RNA targeting uPAR were constructed and validated. The cells were used in a number of in vitro analyses, including migration, invasion and western blot analysis assays. Furthermore, a mouse lung metastatic model was used to detect the metastatic ability of OTSCC cells in the lungs. OTSCC cell metastasis and relapse were determined to be associated with uPAR immunopositivity. Inhibition of uPAR expression in Ts cells demonstrated a 40% decrease in migration and a 60% decrease in invasion in vitro, with an associated downregulation of matrix metalloprotease (MMP)-2, MMP-9 and phosphorylated extracellular signal-regulated kinase. In vivo analysis indicated a 90% decrease in the number of mice bearing macroscopic lung metastases. In conclusion, the present study demonstrated that the targeting of uPAR-inhibited cellular proliferation and invasion would provide a potential treatment for OTSCC in the future.

Diversity and functional evolution of the plasminogen activator system

The urokinase plasminogen activator system is a family of serine proteases which consists of uPA (urokinase plasminogen activator), uPAR (urokinase type plasminogen activator receptor) and PAI-1 (plasminogen activator inhibitor 1). In addition to their significant roles in activation, these proteases act as key regulators of the tumor microenvironment and are involved in the metastatic process in many cancers. High levels of uPA system proteases in many human cancer predicts poor patient prognosis and strongly indicated a key role of uPA system in cancer metastasis. Individual components of uPA system are found to be differentially expressed in cancer cells compared to normal cells and therefore are potential therapeutic targets. In this review, we present the molecular and cellular mechanisms underlying the role of uPA system in cancer progression. Epithelial to mesenchymal transitions (EMT) is the main cause of the cancer cell metastasis. We have also attempted to relate the role of uPA signaling in EMT of cancer cells.

The Role and Mechanism of Epithelial-to-Mesenchymal Transition in Prostate Cancer Progression

In prostate cancer (PCa), similar to many other cancers, distant organ metastasis symbolizes the beginning of the end disease, which eventually leads to cancer death. Many mechanisms have been identified in this process that can be rationalized into targeted therapy. Among them, epithelial-to-mesenchymal transition (EMT) is originally characterized as a critical step for cell trans-differentiation during embryo development and now recognized in promoting cancer cells invasiveness because of high mobility and migratory abilities of mesenchymal cells once converted from carcinoma cells. Nevertheless, the underlying pathways leading to EMT appear to be very diverse in different cancer types, which certainly represent a challenge for developing effective intervention. In this article, we have carefully reviewed the key factors involved in EMT of PCa with clinical correlation in hope to facilitate the development of new therapeutic strategy that is expected to reduce the disease mortality.