Silencing of DLC1 upregulates PAI-1 expression and reduces migration in normal prostate cells

Dissecting the Inorganic Nanoparticle-Driven Interferences on Adhesome Dynamics

Inorganic nanoparticles have emerged as an attractive theranostic tool applied to different pathologies such as cancer. However, the increment in inorganic nanoparticle application in biomedicine has prompted the scientific community to assess their potential toxicities, often preventing them from entering clinical settings. Cytoskeleton network and the related adhesomes nest are present in most cellular processes such as proliferation, migration, and cell death. The nanoparticle treatment can interfere with the cytoskeleton and adhesome dynamics, thus inflicting cellular damage. Therefore, it is crucial dissecting the molecular mechanisms involved in nanoparticle cytotoxicity. This review will briefly address the main characteristics of different adhesion structures and focus on the most relevant effects of inorganic nanoparticles with biomedical potential on cellular adhesome dynamics. Besides, the review put into perspective the use of inorganic nanoparticles for cytoskeleton targeting or study as a versatile tool. The dissection of the molecular mechanisms involved in the nanoparticle-driven interference of adhesome dynamics will facilitate the future development of nanotheranostics targeting cytoskeleton and adhesomes to tackle several diseases, such as cancer.

Tumor suppressor gene DLC1: Its modifications, interactive molecules, and potential prospects for clinical cancer application

Deleted in liver cancer 1 (DLC1) is a recognized tumor suppressor gene that negatively regulates Rho family proteins by hydrolyzing the active GTP-bound state to its inactive GDP-bound state. Active Rho proteins play a positive role in tumorigenesis. Numerous in vitro and in vivo experiments have shown that DLC1 is downregulated or inactivated in various solid tumors, which may be due to the following five reasons: genomic deletion, epigenetic modification and ubiquitin-dependent proteasomal degradation may cause DLC1 underexpression; phosphorylation at the post-translation level may cause DLC1 inactivation; and failure to localize at focal adhesions (FAs) may prevent DLC1 from exerting full activity. All of the causes could be attributed to molecular binding. Experimental evidence suggests that direct or indirect targeting of DLC1 is feasible for cancer treatment. Therefore, elucidating the interaction of DLC1 with its binding partners might provide novel targeted therapies for cancer. In this review, we summarized the binding partners of DLC1 at both the gene and protein levels and expounded a variety of anticancer drugs targeting DLC1 to provide information about DLC1 as a cancer diagnostic indicator or therapeutic target.

Transcription Factor PLAGL1 Is Associated with Angiogenic Gene Expression in the Placenta

During pregnancy, the placenta is important for transporting nutrients and waste between the maternal and fetal blood supply, secreting hormones, and serving as a protective barrier. To better understand placental development, we must understand how placental gene expression is regulated. We used RNA-seq data and ChIP-seq data for the enhancer associated mark, H3k27ac, to study gene regulation in the mouse placenta at embryonic day (e) 9.5, when the placenta is developing a complex network of blood vessels. We identified several upregulated transcription factors with enriched binding sites in e9.5-specific enhancers. The most enriched transcription factor, PLAGL1 had a predicted motif in 233 regions that were significantly associated with vasculature development and response to insulin stimulus genes. We then performed several experiments using mouse placenta and a human trophoblast cell line to understand the role of PLAGL1 in placental development. In the mouse placenta, Plagl1 is expressed in endothelial cells of the labyrinth layer and is differentially expressed in placentas from mice with gestational diabetes compared to placentas from control mice in a sex-specific manner. In human trophoblast cells, siRNA knockdown significantly decreased expression of genes associated with placental vasculature development terms. In a tube assay, decreased PLAGL1 expression led to reduced cord formation. These results suggest that Plagl1 regulates overlapping gene networks in placental trophoblast and endothelial cells, and may play a critical role in placental development in normal and complicated pregnancies.

Differential regulation of rho GTPases during lung adenocarcinoma migration and invasion reveals a novel role of the tumor suppressor StarD13 in invadopodia regulation

Background

Lung cancer is the second most commonly occurring cancer. The ability to metastasize and spread to distant locations renders the tumor more aggressive. Members of the Rho subfamily of small GTP-binding proteins (GTPases) play a central role in the regulation of the actin cytoskeleton and in cancer cell migration and metastasis. In this study we investigated the role of the RhoA/Cdc42 GAP, StarD13, a previously described tumor suppressor, in malignancy, migration and invasion of the lung cancer cells A549.

Methods

We knocked down StarD13 expression in A549 lung cancer cells and tested the effect on cell migration and invadopodia formation using time lapse imaging and invasion assays. We also performed rescue experiments to determine the signaling pathways downstream of StarD13 and transfected the cells with FRET biosensors for RhoGTPases to identify the proteins involved in invadopodia formation.

Results

We observed a decrease in the level of expression of StarD13 in lung tumor tissues compared to normal lung tissues through immunohistochemistry. StarD13 also showed a lower expression in the lung adenocarcinoma cell line A549 compared to normal lung cells, WI38. In addition, the depletion of StarD13 increased cell proliferation and viability in WI38 and A549 cells, suggesting that StarD13 might potentially be a tumor suppressor in lung cancer. The depletion of StarD13, however, inhibited cell motility, conversely demonstrating a positive regulatory role in cell migration. This was potentially due to the constitutive activation of RhoA detected by pull down and FRET assays. Surprisingly, StarD13 suppressed cell invasion by inhibiting Cdc42-mediated invadopodia formation. Indeed, TKS4 staining and invadopodia assay revealed that StarD13 depletion increased Cdc42 activation as well as invadopodia formation and matrix degradation. Normal lung cells depleted of StarD13 also produced invadopodia, otherwise a unique hallmark of invasive cancer cells. Cdc42 knock down mimicked the effects of StarD13, while overexpression of a constitutively active Cdc42 mimicked the effects of its depletion. Finally, immunostaining and FRET analysis revealed the absence of StarD13 in invadopodia as compared to Cdc42, which was activated in invadopodia at the sites of matrix degradation.

Conclusion

In conclusion, StarD13 plays distinct roles in lung cancer cell migration and invasion through its differential regulation of Rho GTPases.

Silencing of ELK3 Induces S-M Phase Arrest and Apoptosis and Upregulates SERPINE1 Expression Reducing Migration in Prostate Cancer Cells

ELK3, an ETS domain-containing transcription factor, participates in various physiological and pathological processes including cell proliferation, migration, angiogenesis, and malignant progression. However, the role of ELK3 in prostate cancer cells and its mechanism are not fully understood. The contribution of ELK3 to prostate cancer progression was investigated in the present study. We showed that silencing of ELK3 by siRNA in prostate cancer cell DU145 induced S-M phase arrest, promoted apoptosis, inhibited cell proliferation and migration in vitro, and suppressed xenograft growth in mice in vivo. In accordance with its ability to arrest cells in S-M phase, the expression of cyclin A and cyclin B was downregulated. In addition, the expression of p53 was upregulated following ELK3 knockdown, while that of antiapoptotic Bcl-2 was decreased. The migration inhibition may partly due to upregulation of SERPINE1 (a serine protease inhibitor) followed ELK3 knockdown. Consistently, downregulation of SERPINE1 resulted in a modest elimination of migration inhibition resulted from ELK3 knockdown. Furthermore, we found that the AKT signaling was activated in ELK3 knockdown cells, and treatment these cells with AKT inhibitor attenuated SERPINE1 expression induced by ELK3 silencing, suggesting that activation of AKT pathway may be one of the reasons for upregulation of SERPINE1 after ELK3 knockdown. In conclusion, modulation of ELK3 expression may control the progression of prostate cancer partly by regulating cell growth, apoptosis, and migration.

DLC1 is a direct target of activated YAP/TAZ that drives collective migration and sprouting angiogenesis

Endothelial YAP/TAZ (YAP is also known as YAP1, and TAZ as WWTR1) signaling is crucial for sprouting angiogenesis and vascular homeostasis. However, the underlying molecular mechanisms that explain how YAP/TAZ control the vasculature remain unclear. This study reveals that the focal adhesion protein deleted-in-liver-cancer 1 (DLC1) is a direct transcriptional target of the activated YAP/TAZ-TEAD complex. We find that substrate stiffening and VEGF stimuli promote expression of DLC1 in endothelial cells. In turn, DLC1 expression levels are YAP and TAZ dependent, and constitutive activation of YAP is sufficient to drive DLC1 expression. DLC1 is needed to limit F-actin fiber formation, integrin-based focal adhesion lifetime and integrin-mediated traction forces. Depletion of endothelial DLC1 strongly perturbs cell polarization in directed collective migration and inhibits the formation of angiogenic sprouts. Importantly, ectopic expression of DLC1 is sufficient to restore migration and angiogenic sprouting in YAP-depleted cells. Together, these findings point towards a crucial and prominent role for DLC1 in YAP/TAZ-driven endothelial adhesion remodeling and collective migration during angiogenesis.This article has an associated First Person interview with the first author of the paper.

Upregulation of DLC-1 inhibits pancreatic cancer progression: Studies with clinical samples and a pancreatic cancer model

Deleted in liver cancer 1 (DLC-1) serves a vital role in the progression of multiple cancers, including those of the pancreas. Numerous studies have aimed to reveal the anti-cancer mechanisms of the DLC-1 gene, though few have focused on its impact on the development of pancreatic cancer. Using clinical pancreatic cancer samples and pancreatic cancer cell lines, the present study aimed to reveal the role of DLC-1 in this disease. The expression levels of DLC-1 were determined in pancreatic cancer and adjacent normal tissues from patients with pancreatic cancer, indicating a decreased expression level of DLC-1 in cancerous tissues. Using the pancreatic cancer cell line SW1990, the effect of DLC overexpression on cell proliferation, invasive capacity and the cell cycle and were assessed. Using a mouse tumor model, the tumor-progression capacity of transfected and untransfected SW1990 cells was investigated, indicating that DLC-1 transfection reduced the capacity for tumor progression. Thus, the present study indicated that the overexpression of DLC-1 inhibited the proliferation and reduced the invasive capacity of SW1990 cells both in vitro and in vivo, and that it may have significant inhibitory effects on the development of pancreatic cancer.

Down-regulation of DLC1 in endothelial cells compromises the angiogenesis process

DLC1 is a RhoGAP-containing tumor suppressor that inhibits angiogenesis by repressing VEGF production in epithelial cells. Here we report the roles of DLC1 in endothelial cells. Silencing of DLC1 (siDLC1) enhances cell migration but reduces tube formation activities of human umbilical vein endothelial cells (HUVECs). Biochemically, RhoA activity and paxillin protein level are markedly increased in siDLC1 HUVECs. Although further silencing of RhoA restores the cell migration phenotype, the tube formation defect and up-regulated paxillin level remain unchanged. On the other hand, paxillin knockdown rescues tube formation and migration phenotypes but not the up-regulated RhoA activity. These results indicate that DLC1 regulates endothelial cell migration through RhoA and paxillin independently and controls tube formation mainly via paxillin. To further determine endothelial DLC1's function, we have generated endothelial specific knockout mice (DLC1-Tek). DLC1-Tek mice appear to be normal and healthy but their angiogenesis processes are compromised as shown in gel plug and aortic ring sprouting assays. Analysis of endothelial cells isolated from DLC1-Tek mice has further affirmed the cellular and biochemical phenotypes established in siDLC1 HUVECs. Our studies have demonstrated a positive regulatory role of endothelial DLC1 in angiogenesis.

Genomic analysis of Ugandan and Rwandan chicken ecotypes using a 600 k genotyping array

Background

Indigenous populations of animals have developed unique adaptations to their local environments, which may include factors such as response to thermal stress, drought, pathogens and suboptimal nutrition. The survival and subsequent evolution within these local environments can be the result of both natural and artificial selection driving the acquisition of favorable traits, which over time leave genomic signatures in a population. This study’s goals are to characterize genomic diversity and identify selection signatures in chickens from equatorial Africa to identify genomic regions that may confer adaptive advantages of these ecotypes to their environments.

Results

Indigenous chickens from Uganda (n = 72) and Rwanda (n = 100), plus Kuroilers (n = 24, an Indian breed imported to Africa), were genotyped using the Axiom® 600 k Chicken Genotyping Array. Indigenous ecotypes were defined based upon location of sampling within Africa. The results revealed the presence of admixture among the Ugandan, Rwandan, and Kuroiler populations. Genes within runs of homozygosity consensus regions are linked to gene ontology (GO) terms related to lipid metabolism, immune functions and stress-mediated responses (FDR < 0.15). The genes within regions of signatures of selection are enriched for GO terms related to health and oxidative stress processes. Key genes in these regions had anti-oxidant, apoptosis, and inflammation functions.

Conclusions

The study suggests that these populations have alleles under selective pressure from their environment, which may aid in adaptation to harsh environments. The correspondence in gene ontology terms connected to stress-mediated processes across the populations could be related to the similarity of environments or an artifact of the detected admixture.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-016-2711-5) contains supplementary material, which is available to authorized users.

Expression array analysis of the hepatocyte growth factor invasive program

Signaling by human hepatocyte growth factor (hHGF) via its cell surface receptor (MET) drives mitogenesis, motogenesis and morphogenesis in a wide spectrum of target cell types and embryologic, developmental and homeostatic contexts. Oncogenic pathway activation also contributes to tumorigenesis and cancer progression, including tumor angiogenesis and metastasis, in several prevalent malignancies. The HGF gene encodes full-length hHGF and two truncated isoforms known as NK1 and NK2. NK1 induces all three HGF activities at modestly reduced potency, whereas NK2 stimulates only motogenesis and enhances HGF-driven tumor metastasis in transgenic mice. Prior studies have shown that mouse HGF (mHGF) also binds with high affinity to human MET. Here we show that, like NK2, mHGF stimulates cell motility, invasion and spontaneous metastasis of PC3M human prostate adenocarcinoma cells in mice through human MET. To identify target genes and signaling pathways associated with motogenic and metastatic HGF signaling, i.e., the HGF invasive program, gene expression profiling was performed using PC3M cells treated with hHGF, NK2 or mHGF. Results obtained using Ingenuity Pathway Analysis software showed significant overlap with networks and pathways involved in cell movement and metastasis. Interrogating The Cancer Genome Atlas project also identified a subset of 23 gene expression changes in PC3M with a strong tendency for co-occurrence in prostate cancer patients that were associated with significantly decreased disease-free survival.

GAP-independent functions of DLC1 in metastasis

Metastases are responsible for most cancer-related deaths. One of the hallmarks of metastatic cells is increased motility and migration through extracellular matrixes. These processes rely on specific small GTPases, in particular those of the Rho family. Deleted in liver cancer-1 (DLC1) is a tumor suppressor that bears a RhoGAP activity. This protein is lost in most cancers, allowing malignant cells to proliferate and disseminate in a Rho-dependent manner. However, DLC1 is also a scaffold protein involved in alternative pathways leading to tumor and metastasis suppressor activities. Recently, substantial information has been gathered on these mechanisms and this review is aiming at describing the potential and known alternative GAP-independent mechanisms allowing DLC1 to impair migration, invasion, and metastasis formation.

Role of epidermal growth factor in pathogenesis of uterine leiomyomas

OBJECTIVE

To investigate the role of epidermal growth factor (EGF) in the pathogenesis of uterine leiomyomas.

METHODS

Human myometrial smooth muscle cells (HM-SMCs) and smooth muscle cells of human uterine leiomyomas (HL-SMCs) were separated from patients' specimens and cultured. After processed by EGF or PD98059 (inhibitor of MKK/MEK) +EGF, the proliferation rate of both SMCs was detected by BrdU method and the phosphorylation level of p44/42 mitogen-activated protein kinase (MAPK) was determined by Western-blot. After different processing time by EGF, the phosphorylation levels of p44/42 MAPK and AKT and p27 expression level in both SMCs were detected by Western-blot.

RESULTS

EGF could significantly promote HL-SMCs proliferation and PD98059 could inhibit this effect (P<0.05); besides, PD98059 could inhibit the increase of the phosphorylation level of p44/42 MAPK in both SMCs induced by EGF. When the processing time by EGF was over 15min, the phosphorylation levels of p44/42 MAPK and AKT in both SMCs decreased sharply and were close to zero; p27 expression in HM-SMCs raised significantly while the upregulation in HL-SMCs was little.

CONCLUSIONS

EGF could not cause activation of EGFR because of the dephosphorylation of p44/42 MAPK and AKT in HL-SMCs, which caused p27 expression insufficiently and cell cycle dysregulation.

StarD13 is a tumor suppressor in breast cancer that regulates cell motility and invasion

Breast cancer is one of the most commonly diagnosed cancers in women around the world. In general, the more aggressive the tumor, the more rapidly it grows and the more likely it metastasizes. Members of the Rho subfamily of small GTP-binding proteins (GTPases) play a central role in breast cancer cell motility and metastasis. The switch between active GTP-bound and inactive GDP-bound state is regulated by guanine nucleotide exchange factors (GEFs), GTPase-activating proteins (GAPs) and guanine-nucleotide dissociation inhibitors (GDIs). We studied the role of StarD13, a recently identified Rho-GAP that specifically inhibits the function of RhoA and Cdc42. We aimed to investigate its role in breast cancer proliferation and metastasis. The levels of expression of this Rho-GAP in tumor tissues of different grades were assayed using immunohistochemistry. We observed that, while the level of StarD13 expression decreases in cancer tissues compared to normal tissues, it increases as the grade of the tumor increased. This was consistent with the fact that although StarD13 was indeed a tumor suppressor in our breast cancer cells, as seen by its effect on cell proliferation, it was needed for cancer cell motility. In fact, StarD13 knockdown resulted in an inhibition of cell motility and cells were not able to detach their tail and move forward. Our study describes, for the first time, a tumor suppressor that plays a positive role in cancer motility.

The regulation of RhoA at focal adhesions by StarD13 is important for astrocytoma cell motility

Malignant astrocytomas are highly invasive into adjacent and distant regions of the normal brain. Rho GTPases are small monomeric G proteins that play important roles in cytoskeleton rearrangement, cell motility, and tumor invasion. In the present study, we show that the knock down of StarD13, a GTPase activating protein (GAP) for RhoA and Cdc42, inhibits astrocytoma cell migration through modulating focal adhesion dynamics and cell adhesion. This effect is mediated by the resulting constitutive activation of RhoA and the subsequent indirect inhibition of Rac. Using Total Internal Reflection Fluorescence (TIRF)-based Förster Resonance Energy Transfer (FRET), we show that RhoA activity localizes with focal adhesions at the basal surface of astrocytoma cells. Moreover, the knock down of StarD13 inhibits the cycling of RhoA activation at the rear edge of cells, which makes them defective in retracting their tail. This study highlights the importance of the regulation of RhoA activity in focal adhesions of astrocytoma cells and establishes StarD13 as a GAP playing a major role in this process.

Effect of StarD13 on colorectal cancer proliferation, motility and invasion

Colon cancer is a cancer of the epithelial cells lining the colon. It is mainly divided into different stages according to the invasiveness and metastatic ability of the tumor. Many mutations are acquired which leads to the development of this malignancy. These occur in entities that greatly affect the cell cycle, cell signaling pathways and cell motility, which all involve the action of Rho GTPases. The protein of interest in the present study was DLC2, also known as StarD13 or START-GAP2, a GTPase-activating protein (GAP) for Rho and Cdc42. Literature data indicate that this protein is considered a tumor-suppressor in hepatocellular carcinoma. Previous research in our laboratory confirmed StarD13 as a tumor suppressor in astrocytoma and in breast cancer. In the present study, we investigated the role of StarD13 in colon cancer. When overexpressed, StarD13 was found to lead to a decrease in cell proliferation in colon cancer cells. Consistently, knockdown of StarD13 led to an increase in cell proliferation. This showed that, similarly to its role in astrocytoma and breast cancer, StarD13 appears to be a tumor suppressor in colon cancer as well. We also examined the role of StarD13 in cell motility. StarD13 knockdown resulted in the inhibition of 2D cell motility. This was due to the inhibition of Rho; consequently Rac-dependent focal complexes were not formed nor detached for the cells to move forward. However, StarD13 knockdown led to an increase in 3D cell motility. Although StarD13 was indeed a tumor suppressor in our colon cancer cells, as evidenced by its effect on cell proliferation, it was required for cancer cell invasion. The present study further describes the role of StarD13 as a tumor suppressor as well as a Rho GAP.

Expression of deleted in liver cancer 1 and plasminogen activator inhibitor 1 protein in ovarian carcinoma and their clinical significance

Background

The deleted in liver cancer 1 (DLC1) and plasminogen activator inhibitor 1 (PAI-1) are known to be closely associated with tumor growth and metastasis in several kinds of human tumors. The aim of this study was to investigate the expression of DLC1 and PAI-1 in ovarian carcinoma, and evaluate their relations with the prognosis of ovarian carcinoma.

Methods

Immunohistochemical staining and Western blot were used to examine the expressions of DLC1 and PAI-1 protein in 25 specimens normal ovarian tissues, 52 specimens of serous cystadenocarcinoma tissues and 23 specimens of mucinous cystadenocarcinoma tissues. Chi-square test, Logistic regression and Partial Correlate analysis were performed to evaluate the association between DLC1 and PAI-1 with clinicopathological characteristics. Overall survival was estimated by Kaplan-Meier curves and multivariate Cox analysis. The relationships between DLC1 and PAI-1 protein expression were analyzed by Pearson’s correlation coefficient.

Results

The expression of DLC1 protein in ovarian carcinoma tissues was significantly lower than that in normal ovarian tissues, but it was converse for PAI-1. In ovarian carcinoma, the expression of DLC1 was significantly associated with advanced FIGO stage, ascites and positive lymph node metastasis, whereas PAI-1 protein was closely related with advanced FIGO stage, poor histological differentiation and lymph node metastasis. The expression of DLC1 was negatively correlated with PAI-1 in ovarian carcinoma. Ovarian cancer patients with negative expression of DLC1 and positive expression of PAI-1 had the worst overall survival time compared to other patients.

Conclusions

The expression of DLC1 and PAI-1 were closely related with the metastasis and invasion of ovarian carcinoma, only the combination of DLC1 and PAI-1 could serve as an independent prognostic factor of ovarian carcinoma.

DLC2/StarD13 plays a role of a tumor suppressor in astrocytoma

Astrocytomas are tumors occurring in young adulthood. Astrocytic tumors can be classified into four grades according to histologic features: grades I, II, III and grade IV. Malignant tumors, those of grades III and IV, are characterized by uncontrolled proliferation, which is known to be regulated by the family of Rho GTPases. StarD13, a GAP for Rho GTPases, has been described as a tumor suppressor in hepatocellular carcinoma. In the present study, IHC analysis on grades I-IV brain tissues from patients showed StarD13 to be overexpressed in grades III and IV astrocytoma tumors when compared to grades I and II. However, when we mined the REMBRANDT data, we found that the mRNA levels of StarD13 are indeed higher in the higher grades but much lower than the normal tissues. Knocking down StarD13 using siRNA led to a decrease in cell death and an increase in cell viability, proving that StarD13 is indeed a tumor suppressor in astrocytomas. This was found to be mainly through cell cycle arrest independently of apoptosis. Finally, we detected an increase in p-ERK in StarD13 knockdown cells, uncovering a potential link between Rho GTPases and ERK activation.

DLC1 interaction with α-catenin stabilizes adherens junctions and enhances DLC1 antioncogenic activity

The DLC1 (for deleted in liver cancer 1) tumor suppressor gene encodes a RhoGAP protein that inactivates Rho GTPases, which are implicated in regulation of the cytoskeleton and adherens junctions (AJs), a cell-cell adhesion protein complex associated with the actin cytoskeleton. Malignant transformation and tumor progression to metastasis are often associated with changes in cytoskeletal organization and cell-cell adhesion. Here we have established in human cells that the AJ-associated protein α-catenin is a new binding partner of DLC1. Their binding was mediated by the N-terminal amino acids 340 to 435 of DLC1 and the N-terminal amino acids 117 to 161 of α-catenin. These proteins colocalized in the cytosol and in the plasma membrane, where together they associated with E-cadherin and β-catenin, constitutive AJ proteins. Binding of DLC1 to α-catenin led to their accumulation at the plasma membrane and required DLC1 GAP activity. Knocking down α-catenin in DLC1-positive cells diminished DLC1 localization at the membrane. The DLC1-α-catenin complex reduced the Rho GTP level at the plasma membrane, increased E-cadherin's mobility, affected actin organization, and stabilized AJs. This process eventually contributed to a robust oncosuppressive effect of DLC1 in metastatic prostate carcinoma cells. Together, these results unravel a new mechanism through which DLC1 exerts its strong oncosuppressive function by positively influencing AJ stability.