Role of Lefty in the anti tumor activity of human adult liver stem cells

Analysis of EMT induction in a non-invasive breast cancer cell line by mesenchymal stem cell supernatant: Study of 2D and 3D microfluidic based aggregate formation and migration ability, and cytoskeleton remodeling

AIMS

The process of Epithelial-to-mesenchymal transition (EMT) as a phenotypic invasive shift and the factors affecting it, are under extensive research. Application of supernatants of human adipose-derived mesenchymal stem cells (hADMSCs) on non-invasive cancer cells is a well known method of in vitro induction of EMT like process. While previous researches have focused on the effects of hADMSCs supernatant on the biochemical signaling pathways of the cells through expression of different proteins and genes, we investigated pro-carcinogic alterations of physico-mechanical cues in terms of changes in cell motility and aggregated formation in 3D microenvironments, and cytoskeletal actin-myosin content and fiber arrangement.

MAIN METHODS

MCF-7 cancer cells were treated by the supernatant from 48 hour-starved hADMSCs, and their vimentin/E-cadherin expressions were evaluated. The invasive potential of treated and non-treated cells was measured and compared through aggregate formation and migration capability. Furthermore, alterations in cell and nucleus morphologies were studied, and F-actin and myosin-II alterations in terms of content and arrangement were investigated.

KEY FINDINGS

Results indicated that application of hADMSCs supernatant enhanced vimentin expression as the biomarker of EMT, and induced pro-carcinogenic effects on non-invasive cancer cells through increased invasive potential by higher cell motility and reduced aggregate formation, rearrangement of actin structure and generation of more stress fibers, together with increased myosin II that lead to enhanced cell motility and traction force.

SIGNIFICANCE

Our results indicated that in vitro induction of EMT through mesenchymal supernatant influenced biophysical features of cancer cells through cytoskeletal remodeling that emphasizes the interconnection of chemical and physical signaling pathways during cancer progress and invasion. Results give a better insight to EMT as a biological process and the synergy between biochemical and biophysical parameters that contribute to this process, and eventually assist in improving cancer treatment strategies.

Lefty A is involved in sunitinib resistance of renal cell carcinoma cells via regulation of IL-8

Renal cell carcinoma (RCC) is the third most frequent malignancy within urological oncology. Sunitinib has been used as the standard of treatment for first-line RCC therapy. Understanding mechanisms of sunitinib resistance in RCC cell is important for clinical therapy and drug development. We established sunitinib resistant RCC cells by treating cells with increasing concentrations of sunitinib and named resistant cells as RCC/SR. Lefty A, an important embryonic morphogen, was increased in RCC/SR cells. Targeted inhibition of Lefty via its siRNAs restored the sensitivity of renal resistant cells to sunitinib treatment. It was due to that si-Lefty can decrease the expression of interleukin-8 (IL-8) in RCC/SR cells. Knockdown of IL-8 abolished Lefty-regulated sunitinib sensitivity of RCC cells. Mechanistically, Lefty can regulate IL-8 transcription via activation of p65, one major transcription factor of IL-8. Collectively, our present revealed that Lefty A can regulate sunitinib sensitivity of RCC cells of via NF-κB/IL-8 signals. It indicated that targeted inhibition of Lefty might be a potent approach to overcome sunitinib resistance of RCC.

Assessing the effect of human mesenchymal stem cell-derived conditioned media on human cancer cell lines: A systematic review

BACKGROUND

Mesenchymal stem cells (MSCs) exhibit differential effect (augmentation or inhibition) on cancer cells depending on the tissue of origin. Given the increasing demand to use MSCs in regenerative medicine, it is vital to ensure that the MSCs being employed are not pro-carcinogenic.

OBJECTIVE

To assess the effect of human MSC derived conditioned media (CM) on human cancer cell lines.

MATERIALS AND METHODS

PubMed, SCOPUS, and Web of Science were searched using the keyword combination 'human mesenchymal stem cell and conditioned media and human cancer cell line and in-vitro'.

RESULTS

MSC-CM pro-carcinogenic molecules were IL-6, IL-8, FGF10, VEGF, PDGF, TGF-b1, IGF-1, GRO-a, OSP, MMPs, TNFα, IL-4, IL-10, IL-13, IL-17, IL-1 β, G-CSF, MCP‑1, MIP‑1α, MIP‑1β, RANTES, MIG, IP‑10, HGFa, ETX, DKK1; anti-carcinogenic molecules were IFN-β, OST, LIGHT, FRTK3, INF-γ, IP-10, LAP, IL‑1RA, IL‑2, IL-5, IL-7, IL-12, IL-15, IFN-α, IFN‑γ. Effector pathways were STAT 1, JAK2/STAT3, Ras-Raf-MEK-ERK, Wnt/β-catenin, NF-κB, ERK1/2, PI3K/ Akt/mTOR, MAPK/ERK. BMSC, ADMSC, UCMSC, WJMSC DPMSC, AMSC, and UTCMSC had a differential effect on carcinogenesis. GMSC, LMSC, FDMSC were anti-carcinogenic. OMSC was pro-carcinogenic.

CONCLUSION

Use of MSC-CM with a pro-carcinogenic effect must be restricted in cancer patients irrespective of the nature of the application.

Genetically-encoded discovery of proteolytically stable bicyclic inhibitors for morphogen NODAL

In this manuscript, we developed a two-fold symmetric linchpin (TSL) that converts readily available phage-displayed peptides libraries made of 20 common amino acids to genetically-encoded libraries of bicyclic peptides displayed on phage. TSL combines an aldehyde-reactive group and two thiol-reactive groups; it bridges two side chains of cysteine [C] with an N-terminal aldehyde group derived from the N-terminal serine [S], yielding a novel bicyclic topology that lacks a free N-terminus. Phage display libraries of SX1CX2X3X4X5X6X7C sequences, where X is any amino acid but Cys, were converted to a library of bicyclic TSL-[S]X1[C]X2X3X4X5X6X7[C] peptides in 45 ± 15% yield. Using this library and protein morphogen NODAL as a target, we discovered bicyclic macrocycles that specifically antagonize NODAL-induced signaling in cancer cells. At a 10 μM concentration, two discovered bicyclic peptides completely suppressed NODAL-induced phosphorylation of SMAD2 in P19 embryonic carcinoma cells. The TSL-[S]Y[C]KRAHKN[C] bicycle inhibited NODAL-induced proliferation of NODAL-TYK-nu ovarian carcinoma cells with apparent IC50 of 1 μM. The same bicycle at 10 μM concentration did not affect the growth of the control TYK-nu cells. TSL-bicycles remained stable over the course of the 72 hour-long assays in a serum-rich cell-culture medium. We further observed general stability in mouse serum and in a mixture of proteases (Pronase™) for 21 diverse bicyclic macrocycles of different ring sizes, amino acid sequences, and cross-linker geometries. TSL-constrained peptides to expand the previously reported repertoire of phage-displayed bicyclic architectures formed by cross-linking Cys side chains. We anticipate that it will aid the discovery of proteolytically stable bicyclic inhibitors for a variety of protein targets.

Human Liver Stem Cells: A Liver-Derived Mesenchymal Stromal Cell-Like Population With Pro-regenerative Properties

Human liver stem cells (HLSCs) were described for the first time in 2006 as a new stem cell population derived from healthy human livers. Like mesenchymal stromal cells, HLSCs exhibit multipotent and immunomodulatory properties. HLSCs can differentiate into several lineages under defined in vitro conditions, such as mature hepatocytes, osteocytes, endothelial cells, and islet-like cell organoids. Over the years, HLSCs have been shown to contribute to tissue repair and regeneration in different in vivo models, leading to more than five granted patents and over 15 peer reviewed scientific articles elucidating their potential therapeutic role in various experimental pathologies. In addition, HLSCs have recently completed a Phase 1 study evaluating their safety post intrahepatic injection in infants with inherited neonatal onset hyperammonemia. Even though a lot of progress has been made in understanding HLSCs over the past years, some important questions regarding the mechanisms of action remain to be elucidated. Among the mechanisms of interaction of HLSCs with their environment, a paracrine interface has emerged involving extracellular vesicles (EVs) as vehicles for transferring active biological materials. In our group, the EVs derived from HLSCs have been studied in vitro as well as in vivo. Our attention has mainly been focused on understanding the in vivo ability of HLSC–derived EVs as modulators of tissue regeneration, inflammation, fibrosis, and tumor growth. This review article aims to discuss in detail the role of HLSCs and HLSC-EVs in these processes and their possible future therapeutic applications.

Requirements of LEFTY and Nodal overexpression for tumor cell survival under hypoxia in glioblastoma

Glioblastomas (GBM) contain numerous hypoxic foci associated with a rare fraction of glioma stem cells (GSCs). Left-right determination factor (LEFTY) and Nodal, members of the transforming growth factor β (TGF-β) superfamily, have glycogen synthase kinase 3β (GSK-3β) phosphorylation motifs and are linked with stemness in human malignancies. Herein, we investigated the roles of LEFTY and Nodal in GBM hypoxic foci. In clinical samples, significantly higher expression of LEFTY, Nodal, phospho (p) GSK-3β, pSmad2, and Nestin, as well as higher apoptotic and lower proliferation rates, were observed in nonpseudopalisading (non-Ps) perinecrotic lesions as compared to Ps and non-necrotic tumor lesions, with a positive correlation between LEFTY, Nodal, pGSK-3β, or pSmad2 scores. In KS-1, a GBM cell line that lacks endogenous Nodal expression, treatment with the hypoxic mimetic CoCl₂ increased LEFTY, pGSK-3β, and pSmad2 levels, but decreased pAkt levels. Moreover, the promoter for LEFTY, but not Nodal, was activated by Smad2 or TGF-β1, suggesting that overexpression of LEFTY and Nodal may be due to Akt-independent GSK-3β inactivation, with or without cooperation of the TGF-β1/Smad2 axis. LEFTY and Nodal overexpression increased proliferation rates and reduced susceptibility to CoCl₂ -induced apoptosis, and increased the expression of epithelial-mesenchymal transition (EMT)/GSC-related markers. An increased ALDH1^high population and more efficient spheroid formation was also observed in LEFTY-overexpressing cells. These findings suggest that LEFTY and Nodal may contribute to cell survival in non-Ps GBM perinecrotic lesions, leading to alterations in apoptosis, proliferation, or EMT/GCS features.

LEFTY2 alleviates hepatic stellate cell activation and liver fibrosis by regulating the TGF-β1/Smad3 pathway

Activated hepatic stellate cells (HSCs) are the major cell type involved in the deposition of extracellular matrix (ECM) during the development of hepatic fibrosis. In this study, we revealed that left-right determination factor 2 (LEFTY2), one of the proteins belonging to the transforming growth factor-β (TGF-β) protein superfamily, was remarkedly decreased in human hepatic fibrosis tissues and in a carbon tetrachloride (CCl₄)-induced liver fibrosis mouse model. In addition, TGF-β1 treatment markedly reduced the level of LEFTY2 in HSCs. Importantly, overexpression of LEFTY2 suppressed the activation and proliferation of HSCs. LEFTY2 inhibited the expression of TGF-β1-induced fibrosis-associated genes (α-SMA and COL1a1) in human (LX-2) and rat (HSC-T6) HSC cell lines in vitro. Mechanistically, we demonstrated, for the first time, the role of LEFTY2 in inhibiting TGF-β1/Smad3 signaling, suggesting that there is a mutual antagonism between LEFTY2 and TGF-β1/Smad3 signaling during liver fibrosis. Similarly, we observed that LEFTY2 has a negative effect on its downstream genes, including c-MYC, CDK4, and cyclin D1, in liver fibrosis. Collectively, our data strongly indicated that LEFTY2 plays an important role in controlling the proliferation and activation of HSCs in the progression of liver fibrosis and this could be a potential therapeutic target for its treatment.

LEFTY2/endometrial bleeding-associated factor up-regulates Na+ Coupled Glucose Transporter SGLT1 expression and Glycogen Accumulation in Endometrial Cancer Cells

LEFTY2 (endometrial bleeding associated factor; EBAF or LEFTYA), a cytokine released shortly before menstrual bleeding, is a negative regulator of cell proliferation and tumour growth. LEFTY2 down-regulates Na⁺/H⁺ exchanger activity with subsequent inhibition of glycolytic flux and lactate production in endometrial cancer cells. Glucose can be utilized not only for glycolysis but also for glycogen formation. Both glycolysis and glycogen formation require cellular glucose uptake which could be accomplished by the Na⁺ coupled glucose transporter-1 (SGLT1; SLC5A1). The present study therefore explored whether LEFTY2 modifies endometrial SGLT1 expression and activity as well as glycogen formation. Ishikawa and HEC1a cells were exposed to LEFTY2, SGLT1 and glycogen synthase (GYS1) transcript levels determined by qRT-PCR. SGLT1, GYS1 and phospho-GYS1 protein abundance was quantified by western blotting, cellular glucose uptake from 2-(N-(7-Nitrobenz-2-oxa-1,3-diazol-4-yl)Amino)-2-Deoxyglucose (2-NBDG) uptake, and cellular glycogen content utilizing an enzymatic assay and subsequent colorimetry. As a result, a 48-hour treatment with LEFTY2 significantly increased SGLT1 and GYS1 transcript levels as well as SGLT1 and GYS1 protein abundance in both Ishikawa and HEC1a cells. 2-NBDG uptake and cellular glycogen content were upregulated significantly in Ishikawa (type 1) but not in type 2 endometrial HEC1a cells, although there was a tendency of increased 2-NBDG uptake. Further, none of the effects were seen in human benign endometrial cells (HESCs). Interestingly, in both Ishikawa and HEC1a cells, a co-treatment with TGF-β reduced SGLT1, GYS and phospho-GYS protein levels, and thus reduced glycogen levels and again HEC1a cells had no significant change. In conclusion, LEFTY2 up-regulates expression and activity of the Na⁺ coupled glucose transporter SGLT1 and glycogen synthase GYS1 in a cell line specific manner. We further show the treatment with LEFTY2 fosters cellular glucose uptake and glycogen formation and TGF-β can negate this effect in endometrial cancer cells.

Mechanism of inhibiting proliferation of hepatocellular carcinoma Hepa1-6 cells by embryonic stem cell-conditioned medium

The present study aimed to investigate the antiproliferative effect of embryonic stem cell-conditioned medium (ESC-CM) on the mouse liver cancer Hepa1-6 cells in vitro. Furthermore, in order to elucidate the underlying molecular mechanism, the microRNAs (miRNAs) in ESC-CM associated with the inhibition of Hepa1-6 proliferation were identified. Following the co-culture of ESC-CM and Hepa1-6 in Transwell chambers, the proliferation, cell cycle, apoptosis and associated protein expression were determined in Hepal-6 cells. Moreover, miRNA array analysis was employed to identify differentially expressed miRNAs. Based on the differentially expressed miRNAs, the target genes and potential associated signaling pathways were determined. Finally, RT-qPCR was conducted to confirm the above results. The ESC-CM inhibited Hepal-6 cell proliferation and increased the percentage of cells at G₁ phase and decreased the percentage of cells at the G₂/M phase of the cell cycle. The expression of cyclin D1/cyclin-dependent kinase (CDK)4/CDK6 was decreased following co-culture, with no effect on cell apoptosis. Six significantly regulated miRNAs were identified and 423 putative target genes of these regulated miRNAs were predicted. Gene ontology analysis revealed the putative target genes to be associated with the ‘DNA replication (GO: 0006260)’ GO term, ‘apoptosis’ and ‘signal transduction’. The Kyoto Encyclopedia of Genes and Genomes analysis indicated that deregulated miRNAs were enriched in the Wnt signaling (KEGG entry: Map 04310) and Hippo signaling pathways (KEGG entry: Map 04390), pathways associated with cancer. Overall, the present study demonstrated the inhibition of Hepa1-6 cell line proliferation upon treatment with ESC-CM, by decreasing cell cycle-associated protein cyclin D1/CDK4/CDK6 expression and arresting cells in G₁ phase of the cell cycle, with no effect on cell apoptosis. Furthermore, the inhibition of proliferation by ESC-CM may be mediated by miRNAs that affect cell cycle-associated mRNAs and the Wnt signaling pathway.

Lefty-1 inhibits renal epithelial-mesenchymal transition by antagonizing the TGF-β/Smad signaling pathway

Epithelial-mesenchymal transition (EMT) is a biological process in which tubular epithelial cells lose their phenotypes, and new mesenchymal feature are obtained. In particular, type II EMT possibly contributes to renal tissue fibrogenesis. Recent studies indicate that Lefty-1, a novel member of the TGF-β superfamily with pleiotropical and biological regulation characteristics on TGF-β and other signaling pathways, is considered to have potential fibrotic effects. However, its role in EMT, which is often a long-term consequence of renal tubulointerstitial fibrosis, remains unknown. In this study, we found that Lefty-1 alleviates EMT induction through antagonizing TGF-β/Smad pathway in vivo and in vitro. In unilateral ureteral obstruction (UUO) model mice, administration of adenovirus-mediated overexpression of Lefty-1 (Ad-Lefty-1) significantly reduced TGF-β1/Smad expression and alleviated the phenotypic transition of epithelial cells to mesenchymal cells and extracellular matrix (ECM) accumulation. In high glucose-induced rat renal tubular duct epithelial cell line (NRK-52E), EMT and ECM synthesis were alleviated with Lefty-1 treatment, which significantly inhibited TGF-β1/Smad pathway activation in UUO mice and high glucose-treated NRK-52E cells. Thus, Lefty-1 can alleviate EMT and renal interstitial fibrosis in vivo and in vitro through antagonizing the TGF-β/Smad pathway, and Lefty-1 might have a potential novel therapeutic effect on fibrotic kidney diseases.

Mesenchymal Stem Cells in the Adult Human Liver: Hype or Hope?

Chronic liver diseases constitute a significant economic, social, and biomedical burden. Among commonly adopted approaches, only organ transplantation can radically help patients with end-stage liver pathologies. Cell therapy with hepatocytes as a treatment for chronic liver disease has demonstrated promising results. However, quality human hepatocytes are in short supply. Stem/progenitor cells capable of differentiating into functionally active hepatocytes provide an attractive alternative approach to cell therapy for liver diseases, as well as to liver-tissue engineering, drug screening, and basic research. The application of methods generally used to isolate mesenchymal stem cells (MSCs) and maintain them in culture to human liver tissue provides cells, designated here as liver MSCs. They have much in common with MSCs from other tissues, but differ in two aspects-expression of a range of hepatocyte-specific genes and, possibly, inherent commitment to hepatogenic differentiation. The aim of this review is to analyze data regarding liver MSCs, probably another type of liver stem/progenitor cells different from hepatic stellate cells or so-called hepatic progenitor cells. The review presents an analysis of the phenotypic characteristics of liver MSCs, their differentiation and therapeutic potential, methods for isolating these cells from human liver, and discusses issues of their origin and heterogeneity. Human liver MSCs are a fascinating object of fundamental research with a potential for important practical applications.

PMN-MDSCs Enhance CTC Metastatic Properties through Reciprocal Interactions via ROS/Notch/Nodal Signaling

Intratumoral infiltration of myeloid-derived suppressor cells (MDSCs) is known to promote neoplastic growth by inhibiting the tumoricidal activity of T cells. However, direct interactions between patient-derived MDSCs and circulating tumors cells (CTCs) within the microenvironment of blood remain unexplored. Dissecting interplays between CTCs and circulatory MDSCs by heterotypic CTC/MDSC clustering is critical as a key mechanism to promote CTC survival and sustain the metastatic process. We characterized CTCs and polymorphonuclear-MDSCs (PMN-MDSCs) isolated in parallel from peripheral blood of metastatic melanoma and breast cancer patients by multi-parametric flow cytometry. Transplantation of both cell populations in the systemic circulation of mice revealed significantly enhanced dissemination and metastasis in mice co-injected with CTCs and PMN-MDSCs compared to mice injected with CTCs or MDSCs alone. Notably, CTC/PMN-MDSC clusters were detected in vitro and in vivo either in patients’ blood or by longitudinal monitoring of blood from animals. This was coupled with in vitro co-culturing of cell populations, demonstrating that CTCs formed physical clusters with PMN-MDSCs; and induced their pro-tumorigenic differentiation through paracrine Nodal signaling, augmenting the production of reactive oxygen species (ROS) by PMN-MDSCs. These findings were validated by detecting significantly higher Nodal and ROS levels in blood of cancer patients in the presence of naïve, heterotypic CTC/PMN-MDSC clusters. Augmented PMN-MDSC ROS upregulated Notch1 receptor expression in CTCs through the ROS-NRF2-ARE axis, thus priming CTCs to respond to ligand-mediated (Jagged1) Notch activation. Jagged1-expressing PMN-MDSCs contributed to enhanced Notch activation in CTCs by engagement of Notch1 receptor. The reciprocity of CTC/PMN-MDSC bi-directional paracrine interactions and signaling was functionally validated in inhibitor-based analyses, demonstrating that combined Nodal and ROS inhibition abrogated CTC/PMN-MDSC interactions and led to a reduction of CTC survival and proliferation. This study provides seminal evidence showing that PMN-MDSCs, additive to their immuno-suppressive roles, directly interact with CTCs and promote their dissemination and metastatic potency. Targeting CTC/PMN-MDSC heterotypic clusters and associated crosstalks can therefore represent a novel therapeutic avenue for limiting hematogenous spread of metastatic disease.

Anti-inflammatory effects of Lefty-1 in renal tubulointerstitial inflammation via regulation of the NF-κB pathway

Renal tubulointerstitial inflammation has an important role in fibrosis, which is the main pathogenetic alteration associated with chronic kidney disease (CKD). The left-right determination factor 1 (Lefty-1) gene pleiotropically and biologically regulates transforming growth factor, mitogen-activated protein kinase and other signaling pathways, and is considered to have a potential anti-inflammatory function. However, its role in renal tubulointerstitial inflammation, which is often a long-term consequence of renal fibrosis, is currently unknown. In the present study, the effects of adenovirus-mediated overexpression of Lefty-1 (Ad-Lefty-1-flag) on renal tubulointerstitial inflammation were determined using a mouse model of unilateral ureteral obstruction (UUO) and a rat renal tubular duct epithelial cell line (NRK-52E), which was treated with lipopolysaccharide (LPS). In vivo results indicated that the inflammatory response was increased in UUO mice, as evidenced by the increase in inflammatory cytokines and chemokines. Conversely, Lefty-1 significantly reversed the effects of UUO. Furthermore, the results of the in vitro study demonstrated that Lefty-1 significantly inhibited LPS-induced inflammatory marker expression in cultured NRK-52E cells via the nuclear factor (NF)-κB signaling pathway. These results suggested that Lefty-1 may ameliorate renal tubulointerstitial inflammation by suppressing NF-κB signaling. In conclusion, the findings of the present study indicated that Lefty-1 may be considered a potential novel therapeutic agent for inhibiting renal tubulointerstitial inflammation or even reversing the CKD process.

LeftyA decreases Actin Polymerization and Stiffness in Human Endometrial Cancer Cells

LeftyA, a cytokine regulating stemness and embryonic differentiation, down-regulates cell proliferation and migration. Cell proliferation and motility require actin reorganization, which is under control of ras-related C3 botulinum toxin substrate 1 (Rac1) and p21 protein-activated kinase 1 (PAK1). The present study explored whether LeftyA modifies actin cytoskeleton, shape and stiffness of Ishikawa cells, a well differentiated endometrial carcinoma cell line. The effect of LeftyA on globular over filamentous actin ratio was determined utilizing Western blotting and flow cytometry. Rac1 and PAK1 transcript levels were measured by qRT-PCR as well as active Rac1 and PAK1 by immunoblotting. Cell stiffness (quantified by the elastic modulus), cell surface area and cell volume were studied by atomic force microscopy (AFM). As a result, 2 hours treatment with LeftyA (25 ng/ml) significantly decreased Rac1 and PAK1 transcript levels and activity, depolymerized actin, and decreased cell stiffness, surface area and volume. The effect of LeftyA on actin polymerization was mimicked by pharmacological inhibition of Rac1 and PAK1. In the presence of the Rac1 or PAK1 inhibitor LeftyA did not lead to significant further actin depolymerization. In conclusion, LeftyA leads to disruption of Rac1 and Pak1 activity with subsequent actin depolymerization, cell softening and cell shrinkage.

Overexpression of Nodal induces a metastatic phenotype in pancreatic cancer cells via the Smad2/3 pathway

Metastasis is the major cause for the high mortality rate of pancreatic cancer. Human embryonic stem cell (hESC) associated genes frequently correlate with malignant disease progression. Recent studies have demonstrated that the embryonic protein Nodal, which plays a critical role during embryonic development, is re-expressed in several types of tumors and promotes cancers progression. However, little is known about the role of Nodal in pancreatic cancer. Here, we show that Nodal expression is upregulated in human pancreatic cancer tissues. Moreover, Nodal expression levels correlate well with the grade of pancreatic cancer differentiation. In addition, we present clear evidence that Nodal induces signal transduction through the Smad2/3-dependent pathway in vitro. Furthermore, we show that Nodal promotes pancreatic cancer cell migration and invasion, induces epithelial-mesenchymal transition (EMT) and enhances the expression of matrix metalloproteinase-2 (MMP2) and CXC chemokine receptor 4 (CXCR4). Using an in vivo liver metastasis model of pancreatic cancer, we observed that blocking Nodal signaling activity with the small-molecule inhibitor SB431542 decreases the number and size of liver metastases. Taken together, our results suggest that Nodal overexpression induces a metastatic phenotype in pancreatic cancer cells, and that targeting Nodal signaling may be a promising therapeutic strategy for pancreatic cancer.

Lefty-1 alleviates TGF-β1-induced fibroblast-myofibroblast transdifferentiation in NRK-49F cells

Fibroblast activation and proliferation are important for fibroblast–myofibroblast transdifferentiation, a crucial process in the pathological changes that define renal interstitial fibrosis. The left–right determination factor (Lefty) is an important cytokine of the transforming growth factor (TGF)-β family, with two variants, Lefty-1 and Lefty-2, in mice. Lefty has diverse functions, such as the regulation of embryonic development, the inhibition of TGF-β1 signaling, and the suppression of tumor activity. However, whether Lefty-1 influences fibroblast activation and proliferation, and consequently prevents fibroblast–myofibroblast transdifferentiation, remains unclear. This study aimed to investigate whether Lefty-1 can attenuate TGF-β1-induced fibroblast–myofibroblast transdifferentiation in normal rat kidney interstitial fibroblast cells (NRK-49F), as well as the mechanisms underlying any effects. Results showed that the typical fibroblast cell morphology of NRK-49F cells was altered after TGF-β1 treatment and that Lefty-1 significantly prevented this change in a dose-dependent manner. Further analyses demonstrated decreased proliferating cell nuclear antigen, cyclin D1, collagen I(A1), alpha-smooth muscle actin, and fibronectin expression. Lefty-1 further induced remarkable reductions in TGF-β1-induced Smad3 and mitogen-activated protein kinase-10/c-Jun N-terminal kinase (JNK-3) signaling, and enhanced expression of the antifibrotic factor bone morphogenetic protein (BMP)-5. However, without TGF-β1, Lefty-1 had no effect on Smad3, JNK-3, and BMP-5 activation and fibroblast–myofibroblast transdifferentiation. Taken together, these findings indicate that Lefty-1 can alleviate TGF-β1-mediated activation and the proliferation of fibroblasts. Furthermore, Lefty-1 may prevent fibroblast–myofibroblast transdifferentiation in part via modulations of Smad3, JNK-3, and BMP-5 activities in the TGF-β/BMP signaling pathway.

Recellularization of rat liver scaffolds by human liver stem cells

In the present study, rat liver acellular scaffolds were used as biological support to guide the differentiation of human liver stem-like cells (HLSC) to hepatocytes. Once recellularized, the scaffolds were maintained for 21 days in different culture conditions to evaluate hepatocyte differentiation. HLSC lost the embryonic markers (alpha-fetoprotein, nestin, nanog, sox2, Musashi1, Oct 3/4, and pax2), increased the expression of albumin, and acquired the expression of lactate dehydrogenase and three subtypes of cytochrome P450. The presence of urea nitrogen in the culture medium confirmed their metabolic activity. In addition, cells attached to tubular remnant matrix structures expressed cytokeratin 19, CD31, and vimentin. The rat extracellular matrix (ECM) provides not only a favorable environment for differentiation of HLSC in functional hepatocytes (hepatocyte like) but also promoted the generation of some epithelial-like and endothelial-like cells. When fibroblast growth factor-epidermal growth factor or HLSC-derived conditioned medium was added to the perfusate, an improvement of survival rate was observed. The conditioned medium from HLSC potentiated also the metabolic activity of hepatocyte-like cells repopulating the acellular liver. In conclusion, HLSC have the potential, in association with the natural ECM, to generate in vitro a functional "humanized liver-like tissue."

LeftyA sensitive cytosolic pH regulation and glycolytic flux in Ishikawa human endometrial cancer cells

OBJECTIVE

LeftyA, a powerful regulator of stemness, embryonic differentiation, and reprogramming of cancer cells, counteracts cell proliferation and tumor growth. Key properties of tumor cells include enhanced glycolytic flux, which is highly sensitive to cytosolic pH and thus requires export of H(+) and lactate. H(+) extrusion is in part accomplished by Na(+)/H(+) exchangers, such as NHE1. An effect of LeftyA on transport processes has, however, never been reported. The present study thus explored whether LeftyA modifies regulation of cytosolic pH (pHi) in Ishikawa cells, a well differentiated endometrial carcinoma cell model.

METHODS

NHE1 transcript levels were determined by qRT-PCR, NHE1 protein abundance quantified by Western blotting, pHi estimated utilizing (2',7'-bis-(2-carboxyethyl)-5-(and-6)-carboxyfluorescein [BCECF] fluorescence, Na(+)/H(+) exchanger activity from Na(+) dependent realkalinization after an ammonium pulse, and lactate concentration in the supernatant utilizing an enzymatic assay and subsequent colorimetry.

RESULTS

A 2 h treatment with LeftyA (8 ng/ml) significantly decreased NHE1 transcript levels (by 99.6%), NHE1 protein abundance (by 71%), Na(+)/H(+) exchanger activity (by 55%), pHi (from 7.22 ± 0.02 to 7.05 ± 0.02), and lactate release (by 41%).

CONCLUSIONS

LeftyA markedly down-regulates NHE1 expression, Na(+)/H(+) exchanger activity, pHi, and lactate release in Ishikawa cells. Those effects presumably contribute to cellular reprogramming and growth inhibition.

Increased expression of Nodal correlates with reduced patient survival in pancreatic cancer

BACKGROUND

Nodal (nodal growth differentiation factor) and its inhibitor Lefty (left right determination factor), which are ligands of the TGF (transforming growth factor) β superfamily, are responsible for the determination of left-right asymmetry in vertebrates. Nodal/Lefty signaling has been suggested to play a role in the development of metastatic melanoma and breast cancer. However, it remains unclear whether this pathway is also involved in human pancreatic ductal adenocarcinoma (PDAC).

METHODS

Pancreatic cancer patient specimens with clinical data (n = 54) were used to investigate the clinical significance of Nodal-Lefty signaling. A set of in vitro assays were carried out in a human pancreatic cancer cell line (Colo-357) to assess the functional relevance of Nodal-Lefty signaling.

RESULTS

Nodal was absent in the human normal pancreas, while Lefty was present in islet cells. Though Nodal and Lefty expression were found in cancer cells at various expression levels, the cancer-associated tubular complexes were particularly positive for Lefty. Survival analysis revealed that high expression of Nodal correlated with reduced patient survival (median survival 17.8 vs 33.0 months, p = 0.013). Cultured pancreatic cancer cell lines expressed Nodal and Lefty at different levels. In vitro functional assays revealed that treatment with human recombinant Nodal inhibited cell growth and increased invasion of Colo-357 pancreatic cancer cells whereas no effect was found upon treatment with recombinant Lefty.

CONCLUSION

Nodal-Lefty signaling might be involved in the pathogenesis of PDAC as Nodal expression marks a subtype of PDAC with unfavorable prognosis.

The therapeutic potential of bone marrow-derived mesenchymal stromal cells on hepatocellular carcinoma

Mesenchymal stromal cells (MSCs) are more often obtained from adult and extraembryonic tissues, with the latter sources being likely better from a therapeutic perspective. MSCs show tropism towards inflamed or tumourigenic sites. Mechanisms involved in MSC recruitment into tumours are comprehensively analysed, including chemoattractant signalling axes, endothelial adhesion and transmigration. In addition, signals derived from hepatocellular carcinoma (HCC) tumour microenvironment and their influence in MSC tropism and tumour recruitment are dissected, as well as the present controversy regarding their influence on tumour growth and/or metastasis. Finally, evidences available on the use of MSCs and other selected progenitor/stem cells as vehicles of antitumourigenic genes are discussed. A better knowledge of the mechanisms involved in progenitor/stem cell recruitment to HCC tumours is proposed in order to enhance their tumour targeting which may result in improvements in cell-based gene therapy strategies.

Lefty1 and lefty2 control the balance between self-renewal and pluripotent differentiation of mouse embryonic stem cells

Lefty expression has been recognized as a stemness marker because Lefty is enriched both in undifferentiated embryonic stem cells (ESCs) and in blastocysts. Here, we examined the function of Lefty1 and Lefty2 in the maintenance of self-renewal and pluripotency of mouse ESCs (mESCs). Suppression of Lefty1 or Lefty2 expression in mESCs did not alter the self-renewal properties of mESCs under nondifferentiating conditions, but suppression of these genes did affect Smad2 phosphorylation and differentiation. Lefty1 knockdown mESCs showed enhanced phosphorylation of Smad2 and increased differentiation potential, whereas Lefty2 knockdown mESCs exhibited reduced phosphorylation of Smad2 and enhanced self-renewal in the presence of a differentiation signal. In vivo, teratomas developed from Lefty2 knockdown mESCs contained massive expansions of immature neuroepithelium, a marker of malignant teratomas. Taken together, these results suggest that optimal expression of Lefty1 and Lefty2 is critical for the balanced differentiation of mESCs into three germ layers.

Inhibitory effect of Nodal on the expression of aldehyde dehydrogenase 1 in endometrioid adenocarcinoma of uterus

Cancers consist of heterogeneous populations. Recently, it has been demonstrated that cells with tumorigenic potential are limited to a small population, called cancer-initiating cells (CICs). Aldehyde dehydrogenase 1 (ALDH1) is one of the markers of CICs. We previously reported that ALDH1-high cases of uterine endometrioid adenocarcinoma showed poor prognosis, and ALDH1-high population of endometrioid adenocarcinoma cell line was more tumorigenic, resistant to anti-cancer drugs, and invasive than ALDH1-low population. Here, the regulatory signaling for ALDH1 was examined. The inhibition of TGF-β signaling increased ALDH1-high population. Among TGF-β family members, Nodal expression and ALDH1 expression levels were mutually exclusive. Immunohistochemical analysis on clinical samples revealed Nodal-high tumor cells to be ALDH-low and vise versa, suggesting that Nodal may inhibit ALDH1 expression via stimulating TGF-β signaling in uterine endometrioid adenocarcinoma. In fact, the addition of Nodal to endometrioid adenocarcinoma cell line reduced ALDH1-high population. Although ALDH1 mRNA level was not affected, the amount of ALDH1 protein appeared to be reduce by Nodal through ubiquitine-proteasome pathway. The regulation of TGF-β signaling might be a novel therapeutic target of CICs in endometrioid adenocarcinoma.

Nodal promotes invasive phenotypes via a mitogen-activated protein kinase-dependent pathway

The progression of cancer from localized to invasive disease is requisite for metastasis, and is often characterized by epithelial-to-mesenchymal transition (EMT) and alterations in cellular adhesion and migration. Studies have shown that this transition is associated with an up-regulation of embryonic stem cell-associated genes, resulting in a dedifferentiated phenotype and poor patient prognosis. Nodal is an embryonic factor that plays a critical role in promoting early invasive events during development. Nodal is silenced as stem cells differentiate; however, it re-emerges in adult life during placentation and mammary gland development, and is aberrantly expressed in many cancers. Here, we show that Nodal over-expression, in poorly-invasive breast cancer and choriocarcinoma cells, causes increased invasion and migration in vitro. Furthermore, we show that Nodal over-expression in these epithelial cancer types induces an EMT-like event concomitant with the internalization of E-Cadherin. This ability of Nodal to promote cellular invasion and EMT-like phenomena is dependent upon the phosphorylation of ERK1/2. Since Nodal normally signals through SMADs, these findings lend insight into an alternative pathway that is hijacked by this protein in cancer. To evaluate the clinical implications of our results, we show that Nodal inhibition reduces liver tumor burden in a model of spontaneous breast cancer metastasis in vivo, and that Nodal loss-of-function in aggressive breast cancer lines results in a decrease in invasive phenotypes. Our results demonstrate that Nodal is involved in promoting invasion in multiple cellular contexts, and that Nodal inhibition may be useful as a therapeutic target for patients with progressive disease.

Embryonic morphogen nodal promotes breast cancer growth and progression

Breast cancers expressing human embryonic stem cell (hESC)-associated genes are more likely to progress than well-differentiated cancers and are thus associated with poor patient prognosis. Elevated proliferation and evasion of growth control are similarly associated with disease progression, and are classical hallmarks of cancer. In the current study we demonstrate that the hESC-associated factor Nodal promotes breast cancer growth. Specifically, we show that Nodal is elevated in aggressive MDA-MB-231, MDA-MB-468 and Hs578t human breast cancer cell lines, compared to poorly aggressive MCF-7 and T47D breast cancer cell lines. Nodal knockdown in aggressive breast cancer cells via shRNA reduces tumour incidence and significantly blunts tumour growth at primary sites. In vitro, using Trypan Blue exclusion assays, Western blot analysis of phosphorylated histone H3 and cleaved caspase-9, and real time RT-PCR analysis of BAX and BCL2 gene expression, we demonstrate that Nodal promotes expansion of breast cancer cells, likely via a combinatorial mechanism involving increased proliferation and decreased apopotosis. In an experimental model of metastasis using beta-glucuronidase (GUSB)-deficient NOD/SCID/mucopolysaccharidosis type VII (MPSVII) mice, we show that although Nodal is not required for the formation of small (<100 cells) micrometastases at secondary sites, it supports an elevated proliferation:apoptosis ratio (Ki67:TUNEL) in micrometastatic lesions. Indeed, at longer time points (8 weeks), we determined that Nodal is necessary for the subsequent development of macrometastatic lesions. Our findings demonstrate that Nodal supports tumour growth at primary and secondary sites by increasing the ratio of proliferation:apoptosis in breast cancer cells. As Nodal expression is relatively limited to embryonic systems and cancer, this study establishes Nodal as a potential tumour-specific target for the treatment of breast cancer.