Hypothesis: Cell plasticity, linking embryonal stem cells to adult stem cell reservoirs and metastatic cancer cells?

N3ICD with the transmembrane domain can effectively inhibit EMT by correcting the position of tight/adherens junctions

EMT allows a polarized epithelium to lose epithelial integrity and acquire mesenchymal characteristics. Previously, we found that overexpression of the intracellular domain of Notch3 (N3ICD) can inhibit EMT in breast cancer cells. In this study, we aimed to elucidate the influence of N3ICD or N3ICD combined with the transmembrane domain (TD+N3ICD) on the expression and distribution of TJs/AJs and polar molecules. We found that although N3ICD can upregulate the expression levels of the above-mentioned molecules, TD+N3ICD can inhibit EMT more effectively than N3ICD alone. TD+N3ICD overexpression upregulated the expression of endogenous full-length Notch3 and contributed to correcting the position of TJs/AJs molecules and better acinar structures formation. Co-immunoprecipitation results showed that the upregulated endogenous full-length Notch3 could physically interact with E-ca in MDA-MB-231/pCMV-(TD+N3ICD) cells. Collectively, our data indicate that overexpression of TD+N3ICD can effectively inhibit EMT, resulting in better positioning of TJs/AJs molecules and cell-cell adhesion in breast cancer cells. Abbreviations: EMT: Epithelial-mesenchymal transition; TJs: Tight junctions; AJs: Adherens junctions; aPKC: Atypical protein kinase C; Crb: Crumbs; Lgl: Lethal (2) giant larvae; LLGL2: lethal giant larvae homolog 2; PAR: Partitioning defective; PATJ: Pals1-associated TJ protein.

Lipophilic statins antagonistically alter the major epithelial-to-mesenchymal transition signaling pathways in breast cancer stem-like cells via inhibition of the mevalonate pathway

Resistance to therapies, recurrence, and metastasis remain challenging issues for breast cancer patients, particularly for triple-negative and breast cancer stem cells. The activation of the epithelial-to-mesenchymal transition (EMT) plays an indispensable role in the poor prognosis of those types. The accumulating proofs indicated that the mevalonate pathway crucially mediates a poor prognosis. Here, the effects of lipophilic 3-hydroxy-3-methyl-glutaryl-coenzyme A inhibitors, atorvastatin, lovastatin, and simvastatin, were investigated on expression and function of a selected profile of EMT-related genes in breast cancer stem-like cells. A nontoxic dose of statins (5 μM for 4 days) significantly (P < 0.05 and >2-fold change) altered expression of 50 of 71 studied genes with a shared cluster of 37 genes that are coding chief operator of signaling pathways in Hippo, Notch, Wnt, proliferation, invasion, angiogenesis, and cell death. They also significantly decreased the levels of Yap/Taz proteins and shifted the expression of vimentin/E-cadherin in favor of induction of differentiation. Statins significantly chemosensitized the treated cells to doxorubicin and also reduced in vitro migration of the cells. Whereas lovastatin and simvastatin significantly decreased the expression of CD44, atorvastatin drastically increased CD24 and caused more wide-ranging impacts. In summary, the statins hold back the process of EMT by the antagonizing of EMT-promoting pathways. High degree of overlapping findings is supportive of the central role of the mevalonate pathway in cancer stem-like cells, but further studies are required to find the optimized chemical structure for the maximum abrogation of orchestrated EMT pathways.

Potential Gene Interactions in the Cell Cycles of Gametes, Zygotes, Embryonic Stem Cells and the Development of Cancer

OBJECTIVES

This review is to explore whether potential gene interactions in the cell cycles of gametes, zygotes, and embryonic stem (ES) cells are associated with the development of cancer.

METHODS

MEDPILOT at the Central Library of the University of Cologne, Germany (Zentralbibliothek Köln) that covers 5,800 international medical journals and 4,300 E-journals was used to collect data. The initial searches were done in December 2012 and additional searches in October 2013-May 2015. The search terms included "cancer development," "gene interaction," and "ES cells," and the time period was between 1998 and 2015. A total of 147 articles in English language only were included in this review.

RESULTS

Transgenerational gene translation is implemented in the zygote through interactions of epigenetic isoforms of transcription factors (TFs) from parental gametes, predominantly during the first two zygote cleavages. Pluripotent transcription factors may provide interacting links with mutated genes during zygote-to-ES cell switches. Translation of post-transcriptional carcinogenic genes is implemented by abnormally spliced, tumor-specific isoforms of gene-encoded mRNA/non-coding RNA variants of TFs employing de novo gene synthesis and neofunctionalization. Post-translationally, mutated genes are preserved in pre-neoplastic ES cell subpopulations that can give rise to overt cancer stem cells. Thus, TFs operate as cell/disease-specific epigenetic messengers triggering clinical expression of neoplasms.

CONCLUSION

Potential gene interactions in the cell cycle of gametes, zygotes, and ES cells may play some roles in the development of cancer.

Molecular mechanisms controlling the phenotype and the EMT/MET dynamics of hepatocyte

The complex spatial and paracrine relationships between the various liver histotypes are essential for proper functioning of the hepatic parenchymal cells. Only within a correct tissue organization, in fact, they stably maintain their identity and differentiated phenotype. The loss of histotype identity, which invariably occurs in the primary hepatocytes in culture, or in vivo in particular pathological conditions (fibrosis and tumours), is mainly because of the phenomenon of epithelial-to-mesenchymal transition (EMT). The EMT process, that occurs in the many epithelial cells, appears to be driven by a number of general, non-tissue-specific, master transcriptional regulators. The reverse process, the mesenchymal-to-epithelial transition (MET), as yet much less characterized at a molecular level, restores specific epithelial identities, and thus must include tissue-specific master elements. In this review, we will summarize the so far unveiled events of EMT/MET occurring in liver cells. In particular, we will focus on hepatocyte and describe the pivotal role in the control of EMT/MET dynamics exerted by a tissue-specific molecular mini-circuitry. Recent evidence, indeed, highlighted as two transcriptional factors, the master gene of EMT Snail, and the master gene of hepatocyte differentiation HNF4α, exhorting a direct reciprocal repression, act as pivotal elements in determining opposite cellular outcomes. The different balances between these two master regulators, further integrated by specific microRNAs, in fact, were found responsible for the EMT/METs dynamics as well as for the preservation of both hepatocyte and stem/precursor cells identity and differentiation. Overall, these findings impact the maintenance of stem cells and differentiated cells both in in vivo EMT/MET physio-pathological processes as well as in culture.

A new perspective of vasculogenic mimicry: EMT and cancer stem cells (Review)

Vasculogenic mimicry (VM), a new pattern of tumor microcirculation, is important for the growth and progression of tumors. Epithelial-mesenchymal transition (EMT) is pivotal in malignant tumor progression and VM formation. With increasing knowledge of cancer stem cell (CSC) phenotypes and functions, increasing evidence suggests that CSCs are involved in VM formation. Recent studies have indicated that EMT is relevant to the acquisition and maintenance of stem cell-like characteristics. Thus, in this review we discuss the correlation between CSCs, EMT and VM formation.

Mesenchymal stem cells and their use in therapy: what has been achieved?

The considerable therapeutic potential of human multipotent mesenchymal stromal cells or mesenchymal stem cells (MSCs) has generated increasing interest in a wide variety of biomedical disciplines. Nevertheless, researchers report studies on MSCs using different methods of isolation and expansion, as well as different approaches to characterize them; therefore, it is increasingly difficult to compare and contrast study outcomes. To begin to address this issue, the Mesenchymal and Tissue Stem Cell Committee of the International Society for Cellular Therapy proposed minimal criteria to define human MSCs. First, MSCs must be plastic-adherent when maintained in standard culture conditions (α minimal essential medium plus 20% fetal bovine serum). Second, MSCs must express CD105, CD73 and CD90, and MSCs must lack expression of CD45, CD34, CD14 or CD11b, CD79α or CD19 and HLA-DR surface molecules. Third, MSCs must differentiate into osteoblasts, adipocytes and chondroblasts in vitro. MSCs are isolated from many adult tissues, in particular from bone marrow and adipose tissue. Along with their capacity to differentiate and transdifferentiate into cells of different lineages, these cells have also generated great interest for their ability to display immunomodulatory capacities. Indeed, a major breakthrough was the finding that MSCs are able to induce peripheral tolerance, suggesting that they may be used as therapeutic tools in immune-mediated disorders. Although no significant adverse events have been reported in clinical trials to date, all interventional therapies have some inherent risks. Potential risks for undesirable events, such as tumor development, that might occur while using these stem cells for therapy must be taken into account and contrasted against the potential benefits to patients.

Reactive oxygen species stimulates epithelial mesenchymal transition in normal human epidermal keratinocytes via TGF-beta secretion

Epithelial to mesenchymal transition (EMT) plays an important role in tumor progression, and is an early step in carcinogenesis. Although reactive oxygen species (ROS) are known to be implicated in EMT in many tumor cell types, its exact role in EMT initiation in normal human cells, especially epidermal keratinocytes (NHEKs), remains unknown. To clarify whether ROS induce EMT in NHEKs, and to establish how ROS regulate EMT, we examined the effect of hydrogen peroxide (H(2)O(2)) on the expression of molecules involved in EMT and cell morphology in NHEKs. H(2)O(2) altered the expression of EMT biomarkers, including downregulation of epithelial cadherin and upregulation of α-smooth muscle actin, through a transcriptional modulator, Snail1. H(2)O(2) also induced epithelial to fibroblast-like morphological changes, together with upregulation of EMT biomarkers, and promoted phosphorylation of ERK1/2 and JNK in a time-dependent manner. Interestingly, H(2)O(2) stimulated the expression and secretion of TGF-β1 in NHEKs. Exogenous TGF-β1 also induced the expression of EMT biomarkers. In contrast, neutralizing antibody anti-TGF-β1 antibody or inhibitor of TGF-β receptor type I suppressed the expression of EMT biomarkers. Our results suggest that ROS stimulated TGF-β1 secretion and MAPK activation, resulting in EMT initiation in NHEKs.

Molecular markers of epithelial-to-mesenchymal transition are associated with tumor aggressiveness in breast carcinoma

BACKGROUND

Epithelial-to-mesenchymal transition (EMT) is a transient process occurring during developmental stages and carcinogenesis, characterized by phenotypic and molecular alterations, resulting in increased invasive and metastatic capabilities of cancer cells and drug resistance. Moreover, emerging evidence suggests that EMT is associated with increased enrichment of cancer stem-like cells in neoplastic tissues. We interrogated the molecular alterations occurring in breast cancer using proposed EMT markers such as E-cadherin, vimentin, epidermal growth factor receptor (EGFR), platelet-derived growth factor (PDGF) D, and nuclear factor κ B (NF-κ B) to decipher their roles in the EMT and breast cancer progression.

METHODS

Fifty-seven invasive ductal adenocarcinomas of the breast were assessed for the expression of E-cadherin, vimentin, EGFR, NF-κ B, and PDGF-D using immunohistochemical analysis. Tumors were categorized into three groups: A (ER+, and/or PR+, HER-2/neu-), B (ER+, and/or PR+, HER-2/neu+), and C (triple-negative: ER-, PR-, and HER-2/neu-). Immunostained slides were microscopically evaluated and scored using intensity (0, 1+, 2+, and 3+) and percentage of positive cells, and data were statistically analyzed.

RESULTS

Membranous E-cadherin was positive in all 57 cases (100%), whereas cytoplasmic E-cadherin was predominantly positive in groups B and C compared with group A (21%, 7%, and 0%, respectively). All group A cases were negative for vimentin and EGFR. There was statistically significant increased expression of vimentin (P < .0002), EGFR (P < .0001), and NF-κ B (P < .02) in triple-negative cases when compared with groups A and B.

CONCLUSIONS

Vimentin, EGFR, and NF-κ B were significantly increased in triple-negative tumors, which is consistent with the aggressiveness of these tumors. These markers could be useful as markers for EMT in breast cancers and may serve as predictive markers for designing customized therapy in the future.

Inflammatory mediators in breast cancer: coordinated expression of TNFα & IL-1β with CCL2 & CCL5 and effects on epithelial-to-mesenchymal transition

Background

The inflammatory chemokines CCL2 (MCP-1) & CCL5 (RANTES) and the inflammatory cytokines TNFα & IL-1β were shown to contribute to breast cancer development and metastasis. In this study, we wished to determine whether there are associations between these factors along stages of breast cancer progression, and to identify the possible implications of these factors to disease course.

Methods

The expression of CCL2, CCL5, TNFα and IL-1β was determined by immunohistochemistry in patients diagnosed with: (1) Benign breast disorders (=healthy individuals); (2) Ductal Carcinoma In Situ (DCIS); (3) Invasive Ducal Carcinoma without relapse (IDC-no-relapse); (4) IDC-with-relapse. Based on the results obtained, breast tumor cells were stimulated by the inflammatory cytokines, and epithelial-to-mesenchymal transition (EMT) was determined by flow cytometry, confocal analyses and adhesion, migration and invasion experiments.

Results

CCL2, CCL5, TNFα and IL-1β were expressed at very low incidence in normal breast epithelial cells, but their incidence was significantly elevated in tumor cells of the three groups of cancer patients. Significant associations were found between CCL2 & CCL5 and TNFα & IL-1β in the tumor cells in DCIS and IDC-no-relapse patients. In the IDC-with-relapse group, the expression of CCL2 & CCL5 was accompanied by further elevated incidence of TNFα & IL-1β expression. These results suggest progression-related roles for TNFα and IL-1β in breast cancer, as indeed indicated by the following: (1) Tumors of the IDC-with-relapse group had significantly higher persistence of TNFα and IL-1β compared to tumors of DCIS or IDC-no-relapse; (2) Continuous stimulation of the tumor cells by TNFα (and to some extent IL-1β) has led to EMT in the tumor cells; (3) Combined analyses with relevant clinical parameters suggested that IL-1β acts jointly with other pro-malignancy factors to promote disease relapse.

Conclusions

Our findings suggest that the coordinated expression of CCL2 & CCL5 and TNFα & IL-1β may be important for disease course, and that TNFα & IL-1β may promote disease relapse. Further in vitro and in vivo studies are needed for determination of the joint powers of the four factors in breast cancer, as well as analyses of their combined targeting in breast cancer.

The role of Notch signaling pathway in epithelial-mesenchymal transition (EMT) during development and tumor aggressiveness

The Notch signaling pathway maintains a balance between cell proliferation and apoptosis, and thus it is believed that Notch signaling pathways may play an important role in the development and progression of several malignancies. However, the functions of Notch signaling in EMT are largely unknown. This mini review describes the role of Notch signaling pathway in EMT, and cataloging how its deregulation is involved in EMT and tumor aggressiveness. Further attempts have been made to summarize the role of several chemopreventive agents that could be useful for targeted inactivation of Notch signaling, and thus it may cause reversal of EMT, which could become a novel approach for cancer prevention and treatment.

Signaling mechanism(s) of reactive oxygen species in Epithelial-Mesenchymal Transition reminiscent of cancer stem cells in tumor progression

Reactive oxygen species (ROS) are known to serve as a second messenger in the intracellular signal transduction pathway for a variety of cellular processes, including inflammation, cell cycle progression, apoptosis, aging and cancer. Recently, ROS have been found to be associated with tumor metastasis involving the processes of tumor cell migration, invasion and angiogenesis. Emerging evidence also suggests that Epithelial-Mesenchymal Transition (EMT), a process that is reminiscent of cancer stem cells, is an important step toward tumor invasion and metastasis, and intimately involved in de novo and acquired drug resistance. In light of recent advances, we are summarizing the role of ROS in EMT by cataloging how its deregulation is involved in EMT and tumor aggressiveness. Further attempts have been made to summarize the role of several chemopreventive agents that could be useful for targeted inactivation of ROS, suggesting that many natural agents could be useful for the reversal of EMT, which would become a novel approach for the prevention of tumor progression and/or treatment of human malignancies especially by killing EMT-type cells that shares similar characteristics with cancer stem cells.

Epithelial-mesenchymal transition in cancer development and its clinical significance

The epithelial-mesenchymal transition (EMT) plays a critical role in embryonic development. EMT is also involved in cancer progression and metastasis and it is probable that a common molecular mechanism is shared by these processes. Cancer cells undergoing EMT can acquire invasive properties and enter the surrounding stroma, resulting in the creation of a favorable microenvironment for cancer progression and metastasis. Furthermore, the acquisition of EMT features has been associated with chemoresistance which could give rise to recurrence and metastasis after standard chemotherapeutic treatment. Thus, EMT could be closely involved in carcinogenesis, invasion, metastasis, recurrence, and chemoresistance. Research into EMT and its role in cancer pathogenesis has progressed rapidly and it is now hypothesized that novel concepts such as cancer stem cells and microRNA could be involved in EMT. However, the involvement of EMT varies greatly among cancer types, and much remains to be learned. In this review, we present recent findings regarding the involvement of EMT in cancer progression and metastasis and provide a perspective from clinical and translational viewpoints.

Bone morphogenetic protein 7 induces mesenchymal-to-epithelial transition in melanoma cells, leading to inhibition of metastasis

Bone morphogenetic protein (BMP) 7 counteracts physiological epithelial-to-mesenchymal transition, a process that is indicative of epithelial plasticity in developmental stages. Because epithelial-to-mesenchymal transition and its reversed process mesenchymal-to-epithelial transition (MET) are also involved in cancer progression, we investigated whether BMP7 plays a role in WM-266-4 melanoma cell growth and metastasis. An MTT assay was conducted in WM-266-4 and HEK293T cell lines to show the cell growth inhibition ability of BMP7 and cisplatin. Semiquantitative RT-PCR was used to determine MET in morphologically changed BMP7-treated melanoma cells. MET-induced cells expressed less a basic helix-loop-helix transcription factor (TWIST) in western blot analysis, and we confirm that BMP receptor (Alk2) siRNA transduction could restore TWIST protein expression via blocking of Smad 1, 5 and 8 signaling. Matrigel invasion and cell migration assays were done to investigate the BMP7-induced metastasis inhibition ability. BMP7 treatment only slightly reduced cell growth rate, but induced apparent MET. BMP7 also reduced the invasion and migration ability. Furthermore, BMP7 reduced the resistance of WM-266-4 cells to cisplatin. Collectively, our findings indicate that the metastatis inhibition ability of BMP7 is involved in MET, and that BMP7 could be used as a potential metastasis inhibitor in human melanoma cells.

Redox mechanisms switch on hypoxia-dependent epithelial-mesenchymal transition in cancer cells

Epithelial-mesenchymal transition (EMT) and hypoxia are considered as crucial events favouring invasion and metastasis of many cancer cells. In this study, different human neoplastic cell lines of epithelial origin were exposed to hypoxic conditions in order to investigate whether hypoxia per se may trigger EMT programme as well as to mechanistically elucidate signal transduction mechanisms involved. The following human cancer cell lines were used: HepG2 (from human hepatoblastoma), PANC-1 (from pancreatic carcinoma), HT-29 (from colon carcinoma) and MCF-7 (from breast carcinoma). Cancer cells were exposed to carefully controlled hypoxic conditions and investigated for EMT changes and signal transduction by using morphological, cell and molecular biology techniques. All cancer cells responded to hypoxia within 72 h by classic EMT changes (fibroblastoid phenotype, SNAIL and beta-catenin nuclear translocation and changes in E-cadherin) and by increased migration and invasiveness. This was involving very early inhibition of glycogen synthase kinase-3beta (GSK-3beta), early SNAIL translocation as well as later and long-lasting activation of Wnt/beta-catenin-signalling machinery. Experimental manipulation, including silencing of hypoxia-inducible factor (HIF)-1alpha and the specific inhibition of mitochondrial generation of reactive oxygen species (ROS), revealed that early EMT-related events induced by hypoxia (GSK-3beta inhibition and SNAIL translocation) were dependent on transient intracellular increased generation of ROS whereas late migration and invasiveness were sustained by HIF-1alpha- and vascular endothelial growth factor (VEGF)-dependent mechanisms. These findings indicate that in cancer cells, early redox mechanisms can switch on hypoxia-dependent EMT programme whereas increased invasiveness is sustained by late and HIF-1alpha-dependent release of VEGF.

Potential for access to embryonic-like cells from human umbilical cord blood

All too often media attention clouds the reality that there are many types of stem cell. The embryos, bone marrow and umbilical cord blood (UCB) are the three most used sources. However, despite what it would appear, embryonic stem cells have not been the first to yield life-saving cures at present. Faster routes to clinical intervention have been using adult stem cells that can be sourced from bone marrow and from cord blood, and that are readily accessible and are more ethically acceptable to the general public. Both these non-embryonic sources have been able to provide sufficient numbers of cells to allow development of clinical translational protocols. Bone marrow-derived cells have been used successfully in myocardial infarct therapy where relining by endothelial tissue has allowed limited reperfusion to damaged cardiac tissue. UCB have also demonstrated significant success for around 20 years in haematotransplantation. With a global human population in excess of 6 billion, births thus UCB, remain the largest untouched source of stem cells available every year. UCB also provide a distinct advantage over other adult stem cells due to the length of the telomere and also due protected immunological status of the developing neonatal environment. The total mutation load in the UCB populations is clearly likely to be significant less than in adult tissues.

Are postnatal hemangioblasts generated by dedifferentiation from committed hematopoietic stem cells?

Cell dedifferentiation occurs in different cell systems. In spite of a relative paucity of data it seems reasonable to assume that cell dedifferentiation exists in reversible equilibrium with differentiation, to which cells resort in response to intercellular signals. The current literature is indeed compatible with the concept that dedifferentiation is guided by structural rearrangements of nuclear chromatin, directed by epigenetic cell memory information available as silenced genes stored on heterochromatin, and that gene transcription exists in reversible "fluctuating continua" during parental cell cycles. Here, we review the molecular mechanisms of cell dedifferentiation and suggest for hematopoietic development that postnatal hemangioblasts are generated by dedifferentiation of committed hematopoietic stem cells.

Signaling networks guiding epithelial-mesenchymal transitions during embryogenesis and cancer progression

Epithelial-mesenchymal transition (EMT) describes the differentiation switch between polarized epithelial cells and contractile and motile mesenchymal cells, and facilitates cell movements and generation of new tissue types during embryogenesis. Many secreted polypeptides are implicated in the EMT process and their corresponding intracellular transduction pathways form highly interconnected networks. Transforming growth factor-beta, Wnt, Notch and growth factors acting through tyrosine kinase receptors induce EMT and often act in a sequential manner. Such growth factors orchestrate the concerted regulation of an elaborate gene program and a complex protein network, needed for establishment of new mesenchymal phenotypes after disassembly of the main elements of epithelial architecture, such as desmosomes, as well as tight, adherens and gap junctions. EMT of tumor cells occurs during cancer progression and possibly generates cell types of the tumor stroma, such as cancer-associated myofibroblasts. EMT contributes to new tumor cell properties required for invasiveness and vascular intravasation during metastasis. Here we present some of the current mechanisms that mediate the process of EMT and discuss their relevance to cancer progression.

Epithelial-mesenchymal transition (EMT) and activated extracellular signal-regulated kinase (p-Erk) in surgically resected pancreatic cancer

BACKGROUND

EMT or transformation to the mesenchymal phenotype plays an important role in tumor invasion and metastasis. In vitro data suggest that mesenchymal transformation may correlate with the activation of PI3 kinase and Ras/Erk pathways. We investigated the expression of EMT markers (low E-cadherin, high fibronectin, and vimentin) and their association with p-Erk in resected pancreatic cancer.

METHODS

Clinical data/surgical specimens from 34 consecutive pancreatic cancer patients (pts) who underwent pancreatectomy were included. Immunohistochemical staining was performed on formalin-fixed paraffin-embedded tissues using monoclonal antibodies against vimentin, fibronectin, E-cadherin, and p-Erk. The results were correlated with clinicopathological parameters and survival. Survival analysis (log-rank test, Cox proportional hazard model), categorical data analysis (Pearson's chi-square, Fisher's exact test) and Kendall's tau were performed at a significance level of 0.05.

RESULTS

The patient population was formed from 13 males and 21 females, with a median age of 66 years (range 38-84 years); American Joint Committee on Cancer (AJCC) stage 1 (n = 2), 2 (n = 27), 3 (n = 5); histological grade 1 (n = 4), 2 (n = 13), 3 (n = 16), 4 (n = 1). Median survival was 15 months (95% CI: 11-24 months). Fibronectin overexpression correlated with the presence of vimentin (p = 0.0048) and activated Erk (p = 0.0264). There was a borderline association of fibronectin with worsening grade (p = 0.06). A negative association between vimentin and E-cadherin was noted (p = 0.0024). Increased fibronectin or vimentin and decreased E-cadherin correlated with poor survival.

CONCLUSION

EMT is associated with poor survival in surgically resected pancreatic adenocarcinoma. A correlation between activated Erk and fibronectin was identified that may open avenues for targeted therapy for this subgroup.

BMP7, a putative regulator of epithelial homeostasis in the human prostate, is a potent inhibitor of prostate cancer bone metastasis in vivo

Bone morphogenic protein 7 (BMP7) counteracts physiological epithelial-to-mesenchymal transition, a process that is indicative of epithelial plasticity. Because epithelial-to-mesenchymal transition is involved in cancer, we investigated whether BMP7 plays a role in prostate cancer growth and metastasis. BMP7 expression in laser-microdissected primary human prostate cancer tissue was strongly down-regulated compared with normal prostate luminal epithelium. Furthermore, BMP7 expression in prostate cancer cell lines was inversely related to tumorigenic and metastatic potential in vivo and significantly correlated to E-cadherin/vimentin ratios. Exogenous addition of BMP7 to human prostate cancer cells dose-dependently inhibited transforming growth factor beta-induced activation of nuclear Smad3/4 complexes via ALK5 and induced E-cadherin expression. Moreover, BMP7-induced activation of nuclear Smad1/4/5 signaling transduced via BMP type I receptors was synergistically stimulated in the presence of transforming growth factor beta, a growth factor that is enriched in the bone microenvironment. Daily BMP7 administration to nude mice inhibited the growth of cancer cells in bone. In contrast, no significant growth inhibitory effect of BMP7 was observed in intraprostatic xenografts. Collectively, our observations suggest that BMP7 controls and preserves the epithelial phenotype in the human prostate and underscore a decisive role of the tumor microenvironment in mediating the therapeutic response of BMP7. Thus, BMP7 can still counteract the epithelial-to-mesenchymal transition process in the metastatic tumor, positioning BMP7 as a novel therapeutic molecule for treatment of metastatic bone disease.

Hemangioblasts representing a functional endothelio-hematopoietic entity in ontogeny, postnatal life, and CML neovasculogenesis

The life-long interdependencies/interactions between hemato- and endotheliopoiesis suggest that they form a supplementary functional entity. This view is compatible with the concept of stem cell plasticity as a reversible continuum and is substantiated by the common hematopoietic-endothelial stem cell, i.e., hemangioblasts, with bidirectional, reversible gene transcription and persistence in postnatal life. Indeed, embryonal stem cells/hemangioblasts appear to form a reservior in the adult with the possibility of dedifferentiation of more differentiated progenitor cells back to hemangioblasts. The recent detection of BCR/ABL fusion proteins in endothelial cells during vascular neoangiogenesis in CML suggests that endothelial cells are part of the neoplastic clone, and extends the concept of a functional entity to include CML angiogenesis. Thus, hemangioblasts rather than committed hematopoietic stem cells appear to be target cells for the first oncogenic hit in CML, which could occur as early as during the first steps of embryonal stem cell differentiation towards hemato-endotheliopoiesis and/or in hemangioblasts persisting in adults. The relation of the other leukemias to hemangioblasts is not known.

Roots and stems: stem cells in cancer

Cancer develops from normal tissues through the accumulation of genetic alterations that act in concert to confer malignant phenotypes. Although we have now identified some of the genes that when mutated initiate tumor formation and drive cancer progression, the identity of the cell population(s) susceptible to such transforming events remains undefined for the majority of human cancers. Recent work indicates that a small population of cells endowed with unique self-renewal properties and tumorigenic potential is present in some, and perhaps all, tumors. Although our understanding of the biology of these putative cancer stem cells remains rudimentary, the existence of such cells has implications for current conceptualizations of malignant transformation and therapeutic approaches to cancer.

Mesenchymal stem cells

About 40 years ago Friedenstein described stromal cells in the bone marrow that were spindle shaped and proliferate to form colonies. These cells attach to plastic and are able to differentiate under defined in vitro conditions into multiple cell types present in many different tissues, e.g. osteoblasts, chondroblasts, adipocytes, etc. Later on these cells, obtained from postnatal bone marrow, were called mesenchymal stem cells (MSC) or stromal stem cells. Recently the presence of somewhat similar cells has been demonstrated in many other tissues too. In spite of extensive attempts to characterize these cells we are still lacking definitive in vivo markers of MSC although retrospective functional data strongly support the existence of common adult stem cells that have the capacity to differentiate along various specific differentiation lineages. Since MSC can be rather easily isolated from the bone marrow and can also be expanded in vitro they have become a prime target for researchers of tissue regeneration. These cells have now been extensively used for transplantation experiments in animals and also for some therapeutic trials in humans. However, much new research is needed to learn enough on the molecular mechanisms of MSC differentiation to evaluate their full capacity for tissue regeneration.