Overexpression of bone morphogenetic protein-6 (BMP-6) in murine epidermis suppresses skin tumor formation by induction of apoptosis and downregulation of fos/jun family members

Antifibrogenic Activities of CYP11A1-derived Vitamin D3-hydroxyderivatives Are Dependent on RORγ

Previous studies showed that noncalcemic 20(OH)D3, a product of CYP11A1 action on vitamin D3, has antifibrotic activity in human dermal fibroblasts and in a bleomycin mouse model of scleroderma. In this study, we tested the role of retinoic acid-related orphan receptor γ (RORγ), which is expressed in skin, in the action of CYP11A1-derived secosteroids using murine fibroblasts isolated from the skin of wild-type (RORγ +/+), knockout (RORγ -/-), and heterozygote (RORγ +/-) mice. CYP11A1-derived 20(OH)D3, 20,23(OH)2D3, 1,20(OH)2D3, and 1,20,23(OH)3D3 inhibited proliferation of RORγ +/+ fibroblasts in a dose-dependent manner with a similar potency to 1,25(OH)2D3. Surprisingly, this effect was reversed in RORγ +/- and RORγ -/- fibroblasts, with the most pronounced stimulatory effect seen in RORγ -/- fibroblasts. All analogs tested inhibited TGF-β1-induced collagen synthesis in RORγ +/+ fibroblasts and the expression of other fibrosis-related genes. This effect was curtailed or reversed in RORγ -/- fibroblasts. These results show that the antiproliferative and antifibrotic activities of the vitamin D hydroxy derivatives are dependent on a functional RORγ. The dramatic changes in the transcriptomes of fibroblasts of RORγ -/- versus wild-type mice following treatment with 20(OH)D3 or 1,20(OH)2D3 provide a molecular basis to explain, at least in part, the observed phenotypic differences.

Cell Competition Boosts Clonal Evolution and Hypoxic Selection in Cancer

The comparison of fitness between cells leads to the elimination of less competent cells in the presence of more competent neighbors via cell competition (CC). This phenomenon has been linked with several cancer-related genes and thus may play an important role in cancer. Various processes are involved in the regulation of tumor initiation and growth, including tumor hypoxia, clonal stem cell selection, and immune cell response, all of which have been recently shown to have a potential connection with the mechanisms involved in CC. This review aims to unravel the relation between these processes and competitive cell interactions and how this affects disease progression.

Characterization of Embryonic Skin Transcriptome in Anser cygnoides at Three Feather Follicles Developmental Stages

In order to enrich the Anser cygnoides genome and identify the gene expression profiles of primary and secondary feather follicles development, de novo transcriptome assembly of skin tissues was established by analyzing three developmental stages at embryonic day 14, 18, and 28 (E14, E18, E28). Sequencing output generated 436,730,608 clean reads from nine libraries and de novo assembled into 56,301 unigenes. There were 2,298, 9,423 and 12,559 unigenes showing differential expression in three stages respectively. Furthermore, differentially expressed genes (DEGs) were functionally classified according to genes ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and series-cluster analysis. Relevant specific GO terms such as epithelium development, regulation of keratinocyte proliferation, morphogenesis of an epithelium were identified. In all, 15,144 DEGs were clustered into eight profiles with distinct expression patterns and 2,424 DEGs were assigned to 198 KEGG pathways. Skin development related pathways (mitogen-activated protein kinase signaling pathway, extra-cellular matrix -receptor interaction, Wingless-type signaling pathway) and genes (delta like canonical Notch ligand 1, fibroblast growth factor 2, Snail family transcriptional repressor 2, bone morphogenetic protein 6, polo like kinase 1) were identified, and eight DEGs were selected to verify the reliability of transcriptome results by real-time quantitative PCR. The findings of this study will provide the key insights into the complicated molecular mechanism and breeding techniques underlying the developmental characteristics of skin and feather follicles in Anser cygnoides.

Silibinin inhibits ultraviolet B radiation-induced mast cells recruitment and bone morphogenetic protein 2 expression in the skin at early stages in Ptch(+/-) mouse model of basal cell carcinoma

Around 80% of nonmelanoma skin cancers (NMSCs) are basal cell carcinoma (BCC), still studies evaluating the efficacy of chemopreventive agents during early stage/s of BCC development are lacking. Accordingly, utilizing the well-established patched (Ptch)+/- mouse model of ultraviolet B (UVB) radiation-induced BCC formation, we excised skin samples from UVB exposed Ptch+/- and Ptch+/+ mice before tumor formation to study the promotion/progression of BCC and to determine the efficacy and target/s of silibinin, a well-known skin cancer chemopreventive agent. UVB exposure for 1 month increased the number of mast cells in Ptch+/- mice by ~48% (P < 0.05), which was completely inhibited by silibinin. Polymerase chain reaction profiler array analysis of skin samples showed strong molecular differences between Ptch+/+ and Ptch+/- mice which were either unexposed or UVB irradiated+/- silibinin treatment. Most notably, silibinin treatment significant decreased the expression of BMP-2, Bbc3, PUMA, and Ccnd1 in Ptch+/- mice irradiated with silibinin + UVB. Additional studies showed that silibinin targets UVB-induced expression of bone morphogenetic protein 2 (BMP-2) in Ptch+/- mouse skin. Last, our studies found that silibinin strongly attenuates UVB-induced BMP-2 expression and DNA damage in Ptch+/- mouse skin ex vivo only after single UVB exposure. Together, our results suggest a possible role of mast cell recruitment and BMP-2 activation in the early stages of BCC development; these are strongly inhibited by silibinin suggesting its possible chemopreventive efficacy against BCC formation in long-term UVB exposure regimen.

Expression of bone morphogenetic protein 6 in non-small cell lung cancer and its significance

The present study investigated the expression and clinical significance of bone morphogenetic protein 6 (BMP-6) in patients with non-small cell lung cancer (NSCLC). The tumor and adjacent normal lung tissues were harvested from 65 patients with NSCLC. BMP-6 mRNA expression was measured by reverse transcription-quantitative polymerase chain reaction, while protein expression was measured using immunohistochemistry or an ELISA. Cell viability was determined using Cell Counting Kit-8. The association of BMP-6 mRNA expression with the prognosis of patients with NSCLC was analyzed using the Kaplan-Meier plotter database. BMP-6 mRNA expression in NSCLC tumor tissues was significantly reduced, compared with the adjacent normal lung tissues (P<0.001), yet no significant differences were observed between patients with different clinicopathological features (P>0.05). The expression level of BMP-6 protein in NSCLC tumor tissues was significantly reduced, compared with the adjacent normal lung tissues (P<0.05). Analysis with the Kaplan-Meier plotter database revealed that patients with NSCLC with low BMP-6 mRNA expression had a reduced overall survival rate (P<0.01). The active BMP6 protein significantly inhibited cell proliferation in H460, H1299, A549 and H520 cells. In conclusion, BMP-6 is a tumor suppressor in lung cancer and loss of BMP-6 expression is significantly associated with a poor prognosis in patients with NSCLC.

Human Induced Pluripotent Stem Cells Differentiate Into Functional Mesenchymal Stem Cells and Repair Bone Defects

Using short-term exposure of embryoid bodies to transforming growth factor-β, the authors directed induced pluripotent stem cells (iPSCs) toward mesenchymal stem cell (MSC) differentiation. Two types of iPSC-derived MSCs were identified: early (aiMSCs) and late (tiMSCs) outgrowing cells. Both types differentiated in vitro in response to osteogenic or adipogenic supplements; aiMSCs demonstrated higher osteogenic potential than tiMSCs. Upon orthotopic injection into radial defects, both types regenerated bone and contributed to defect repair.

Mesenchymal stem cells (MSCs) are currently the most established cells for skeletal tissue engineering and regeneration; however, their availability and capability of self-renewal are limited. Recent discoveries of somatic cell reprogramming may be used to overcome these challenges. We hypothesized that induced pluripotent stem cells (iPSCs) that were differentiated into MSCs could be used for bone regeneration. Short-term exposure of embryoid bodies to transforming growth factor-β was used to direct iPSCs toward MSC differentiation. During this process, two types of iPSC-derived MSCs (iMSCs) were identified: early (aiMSCs) and late (tiMSCs) outgrowing cells. The transition of iPSCs toward MSCs was documented using MSC marker flow cytometry. Both types of iMSCs differentiated in vitro in response to osteogenic or adipogenic supplements. The results of quantitative assays showed that both cell types retained their multidifferentiation potential, although aiMSCs demonstrated higher osteogenic potential than tiMSCs and bone marrow-derived MSCs (BM-MSCs). Ectopic injections of BMP6-overexpressing tiMSCs produced no or limited bone formation, whereas similar injections of BMP6-overexpressing aiMSCs resulted in substantial bone formation. Upon orthotopic injection into radial defects, all three cell types regenerated bone and contributed to defect repair. In conclusion, MSCs can be derived from iPSCs and exhibit self-renewal without tumorigenic ability. Compared with BM-MSCs, aiMSCs acquire more of a stem cell phenotype, whereas tiMSCs acquire more of a differentiated osteoblast phenotype, which aids bone regeneration but does not allow the cells to induce ectopic bone formation (even when triggered by bone morphogenetic proteins), unless in an orthotopic site of bone fracture.

Significance

Mesenchymal stem cells (MSCs) are currently the most established cells for skeletal tissue engineering and regeneration of various skeletal conditions; however, availability of autologous MSCs is very limited. This study demonstrates a new method to differentiate human fibroblast-derived induced pluripotent stem cells (iPSCs) to cells with MSC properties, which we comprehensively characterized including differentiation potential and transcriptomic analysis. We showed that these iPS-derived MSCs are able to regenerate nonunion bone defects in mice more efficiently than bone marrow-derived human MSCs when overexpressing BMP6 using a nonviral transfection method.

Mechanisms of action of bone morphogenetic proteins in cancer

The bone morphogenetic proteins (BMPs) play fundamental roles in embryonic development and control differentiation of a diverse set of cell types. It is therefore of no surprise that the BMPs also contribute to the process of tumourigenesis and regulate cancer progression through various stages. We summarise here key roles of BMP ligands, receptors, their signalling mediators, mainly focusing on proteins of the Smad family, and extracellular antagonists, that contribute to the onset of tumourigenesis and to cancer progression in diverse tissues. Overall, the BMP pathways seem to act as tumour suppressors that maintain physiological tissue homeostasis and which are perturbed in cancer either via genetic mutation or via epigenetic misregulation of key gene components. BMPs also control the self-renewal and fate choices made by stem cells in several tissues. By promoting cell differentiation, including inhibition of the process of epithelial-mesenchymal transition, BMPs contribute to the malignant progression of cancer at advanced stages. It is therefore reasonable that pharmaceutical industries continuously develop biological agents and chemical modulators of BMP signalling with the aim to improve therapeutic regimes against several types of cancer.

Gene expression profiling associated with angiotensin II type 2 receptor-induced apoptosis in human prostate cancer cells

Increased expression of angiotensin II type 2 receptor (AT2R) induces apoptosis in numerous tumor cell lines, with either Angiotensin II-dependent or Angiotensin II-independent regulation, but its molecular mechanism remains poorly understood. Here, we used PCR Array analysis to determine the gene and microRNA expression profiles in human prostate cancer cell lines transduced with AT2R recombinant adenovirus. Our results demonstrated that AT2R over expression leads to up-regulation of 6 apoptosis-related genes (TRAIL-R2, BAG3, BNIPI, HRK, Gadd45a, TP53BP2), 2 cytokine genes (IL6 and IL8) and 1 microRNA, and down-regulation of 1 apoptosis-related gene TNFSF10 and 2 cytokine genes (BMP6, BMP7) in transduced DU145 cells. HRK was identified as an up-regulated gene in AT2R-transduced PC-3 cells by real-time RT-PCR. Next, we utilized siRNAs to silence the up-regulated genes to further determine their roles on AT2R overexpression mediated apoptosis. The results showed downregulation of Gadd45a reduced the apoptotic effect by ∼30% in DU145 cells, downregulation of HRK reduced AT2R-mediated apoptosis by more than 50% in PC-3 cells, while downregulation of TRAIL-R2 enhanced AT2R-mediated apoptosis more than 4 times in DU145 cells. We also found that the effects on AT2R-mediated apoptosis caused by downregulation of Gadd45a, TRAIL-R2 and HRK were independent in activation of p38 MAPK, p44/42 MAPK and p53. Taken together, our results demonstrated that TRAIL-R2, Gadd45a and HRK may be novel target genes for further study of the mechanism of AT2R-mediated apoptosis in prostate cancer cells.

Hypermethylation leads to bone morphogenetic protein 6 downregulation in hepatocellular carcinoma

BACKGROUND

In the liver, bone morphogenetic protein 6 (BMP-6) maintains balanced iron metabolism. However, the mechanism that underlies greater BMP-6 expression in hepatocellular carcinoma (HCC) tissue than adjacent non-cancerous tissue is unclear. This study sought to investigate the epigenetic mechanisms of BMP-6 expression by analysing the relationship between the DNA methylation status of BMP-6 and the expression of BMP-6.

METHODS

Methylation-specific polymerase chain reaction (PCR), bisulphite sequencing PCR, the MethyLight assay, and quantitative real-time PCR were performed to examine BMP-6 methylation and mRNA expression levels. Immunohistochemistry (IHC) was performed on tissue arrays to evaluate the BMP-6 protein level.

RESULTS

BMP-6 mRNA expression was approximately 84.09% lower in HCC tissues than in adjacent non-cancerous tissues, and this low level of expression was associated with a poor prognosis. Moreover, the hypermethylation observed in HCC cell lines and HCC tissues was correlated with the BMP-6 mRNA expression level, and this correlation was validated following treatment with 5-aza-CdR, a demethylation agent. In addition, BMP-6 DNA methylation was upregulated by 68.42% in 114 clinical HCC tissue samples compared to adjacent normal tissues, whereas the BMP-6 staining intensity was downregulated by 77.03% in 75 clinical HCC tissue samples in comparison to adjacent normal tissues. Furthermore, elevated expression of BMP-6 in HCC cell lines inhibited cell colony formation.

CONCLUSIONS

Our results suggest that BMP-6 CpG island hypermethylation leads to decreased BMP-6 expression in HCC tissues.

Association of bone morphogenetic protein 6 with exocrine gland dysfunction in patients with Sjögren's syndrome and in mice

OBJECTIVE

Primary Sjögren's syndrome (SS) is characterized by autoimmune activation and loss of function in secretory epithelia. The present study was undertaken to investigate and characterize changes in the epithelia associated with the loss of gland function in primary SS.

METHODS

To identify changes in epithelial gene expression, custom microarrays were probed with complementary RNA (cRNA) isolated from minor salivary glands (MSGs) of female patients with primary SS who had low focus scores and low salivary flow rates, and the results were compared with those obtained using cRNA from the MSGs of sex-matched healthy volunteers. The effect of bone morphogenetic protein 6 (BMP-6) on salivary gland function was tested using adeno-associated virus-mediated gene transfer to the salivary glands of C57BL/6 mice.

RESULTS

A significant increase in expression of BMP-6 was observed in RNA isolated from SS patients compared with healthy volunteers. Overexpression of BMP-6 locally in the salivary or lacrimal glands of mice resulted in the loss of fluid secretion as well as changes in the connective tissue of the salivary gland. Assessment of the fluid movement in either isolated acinar cells from mice overexpressing BMP-6 or a human salivary gland cell line cultured with BMP-6 revealed a loss in volume regulation in these cells. Lymphocytic infiltration in the submandibular gland of BMP-6 vector-treated mice was increased. No significant changes in the production of proinflammatory cytokines or autoantibodies associated with SS (anti-Ro/SSA and anti-La/SSB) were found after BMP-6 overexpression.

CONCLUSION

In addition to identifying BMP-6 expression in association with xerostomia and xerophthalmia in primary SS, the present results suggest that BMP-6-induced salivary and lacrimal gland dysfunction in primary SS is independent of the autoantibodies and immune activation associated with the disease.

Bone morphogenetic protein signaling suppresses wound-induced skin repair by inhibiting keratinocyte proliferation and migration

Bone morphogenetic protein (BMP) signalling plays a key role in the control of skin development and postnatal remodelling by regulating keratinocyte proliferation, differentiation and apoptosis. To study the role of BMPs in wound-induced epidermal repair, we used transgenic mice overexpressing the BMP downstream component Smad1 under the control of a K14 promoter as an in vivo model, as well as ex vivo and in vitro assays. K14-caSmad1 mice exhibited retarded wound healing associated with significant inhibition of proliferation and increased apoptosis in healing wound epithelium. Furthermore, microarray and qRT-PCR analyses revealed decreased expression of a number of cytoskeletal/cell motility-associated genes including wound-associated keratins (Krt16, Krt17) and Myo5a, in the epidermis of K14-caSmad1 mice versus wild-type controls during wound healing. BMP treatment significantly inhibited keratinocyte migration ex vivo, and primary keratinocytes of K14-caSmad1 mice showed retarded migration compared to wild-type controls. Finally, siRNA-mediated silencing of Bmpr-1B in primary mouse keratinocytes accelerated cell migration and was associated with increased expression of Krt16, Krt17 and Myo5a compared to controls. Thus, this study demonstrates that BMPs inhibit keratinocyte proliferation, cytoskeletal organization and migration in regenerating skin epithelium during wound healing, and raises a possibility for using BMP antagonists for the management of chronic wounds.

Downregulation of BMP6 enhances cell proliferation and chemoresistance via activation of the ERK signaling pathway in breast cancer

Previous studies indicate that bone morphogenetic protein (BMP) 6 is involved in breast cancer development and progression. However, the mechanism underlying the role of BMP6 in breast cancer cell proliferation, differentiation and chemoresistance remains unknown. In this study, we confirmed that BMP6 expression was downregulated in breast cancer tissues compared with the adjacent normal breast tissues. We further demonstrated that the downregulation of BMP6 was correlated with the estrogen receptor (ER) and progesterone receptor (PR) status, tumor grade and enhanced proliferation (Ki67 proliferation index). In vitro functional experiments showed that the suppression of BMP6 expression by a specific small hairpin (sh)RNA vector led to increased proliferation in the MCF7 breast cancer cell line. Furthermore, knockdown of BMP6 in MCF7 cells enhanced the chemoresistance to doxorubicin by upregulation of mdr-1/P-gp expression and activation of the ERK signaling pathway. Taken together, our data suggest that BMP6 plays a critical role in breast cancer cell aberrant proliferation and chemoresistance and may serve as a novel diagnostic biomarker or therapeutic target for breast cancer.

Myo/Nog cells in normal, wounded and tumor-bearing skin

Murine and human skin were examined for the presence of Myo/Nog cells that were originally discovered in the chick embryo by their expression of MyoD mRNA, noggin and the G8 antigen. Myo/Nog cells are the primary source of noggin in telogen hair follicles. They are scarce within the interfollicular dermis and absent in the epidermis. Within 24 h following epidermal abrasion, Myo/Nog cells increase in number in the follicles and appear in the wound. Myo/Nog cells are also recruited to the stroma of tumors formed from v-Ras-transformed keratinocytes (Ker/Ras). Human squamous cell carcinomas and malignant melanomas contain significantly more Myo/Nog cells than basal cell carcinomas. Myo/Nog cells are distinct from macrophages, granulocytes and cells expressing alpha smooth muscle actin in the tumor stroma. Myo/Nog cells may be modulators of skin homoeostasis and wound healing, and potential diagnostic and therapeutic targets in skin cancer.

Using mice to unveil the genetics of cancer resistance

In the UK, four in ten people will develop some form of cancer during their lifetime, with an individual's relative risk depending on many factors, including age, lifestyle and genetic make-up. Much research has gone into identifying the genes that are mutated in tumorigenesis with the overwhelming majority of genetically-modified (GM) mice in cancer research showing accelerated tumorigenesis or recapitulating key aspects of the tumorigenic process. Yet if six out of ten people will not develop some form of cancer during their lifetime, together with the fact that some cancer patients experience spontaneous regression/remission, it suggests there are ways of 'resisting' cancer. Indeed, there are wildtype, spontaneously-arising mutants and GM mice that show some form of 'resistance' to cancer. Identification of mice with increased resistance to cancer is a novel aspect of cancer research that is important in terms of providing both chemopreventative and therapeutic options. In this review we describe the different mouse lines that display a 'cancer resistance' phenotype and discuss the molecular basis of their resistance.

Imaging bone morphogenetic protein 7 induced cell cycle arrest in experimental gliomas

Bone morphogenetic protein 7 (BMP-7) belongs to the superfamily of transforming growth factor β-like cytokines, which can act either as tumor suppressors or as tumor promoters depending on cell type and differentiation. Our investigations focused on analyzing the effects of BMP-7 during glioma cell proliferation in vitro and in vivo. BMP-7 treatment decreased the proliferation of Gli36ΔEGFR-LITG glioma cells up to 50%through a cell cycle arrest in the G(1) phase but not by induction of apoptosis. This effect was mediated by the modulation of the expression and phosphorylation of cyclin-dependent kinase 2, cyclin-dependent kinase inhibitor p21, and downstream retinoblastoma protein. Furthermore, in vivo optical imaging of luciferase activity of Gli36ΔEGFR-LITG cells implanted intracranially into nude mice in the presence or absence of BMP-7 treatment corroborated the antiproliferative effects of this cytokine. This report clearly underlines the tumor-suppressive role of BMP-7 in glioma-derived cells. Taken together, our results indicate that manipulating the BMP/transforming growth factor β signaling cascade may serve as a new strategy for imaging-guided molecular-targeted therapy of malignant gliomas.

Constitutive activation of BMP signalling abrogates experimental metastasis of OVCA429 cells via reduced cell adhesion

Background

Activation of bone morphogenetic protein (BMP)4 signalling in human ovarian cancer cells induces a number of phenotypic changes in vitro, including altered cell morphology, adhesion, motility and invasion, relative to normal human ovarian surface epithelial cells. From these in vitro analyses, we had hypothesized that active BMP signalling promotes the metastatic potential of ovarian cancer.

Methods

To test this directly, we engineered OVCA429 human ovarian cancer cells possessing doxycycline-inducible expression of a constitutively-active mutant BMP receptor, ALK3^QD, and administered these cells to immunocompromised mice. Further characterization was performed in vitro to address the role of activated BMP signalling on the EOC phenotype, with particular emphasis on epithelial-mesenchymal transition (EMT) and cell adhesion.

Results

Unexpectedly, doxycycline-induced ALK3^QD expression in OVCA429 cells reduced tumour implantation on peritoneal surfaces and ascites formation when xenografted into immunocompromised mice by intraperitoneal injection. To determine the potential mechanisms controlling this in vivo observation, we followed with several cell culture experiments. Doxycycline-induced ALK3^QD expression enhanced the refractile, spindle-shaped morphology of cultured OVCA429 cells eliciting an EMT-like response. Using in vitro wound healing assays, we observed that ALK3^QD-expressing cells migrated with long, cytoplasmic projections extending into the wound space. The phenotypic alterations of ALK3^QD-expressing cells correlated with changes in specific gene expression patterns of EMT, including increased Snail and Slug and reduced E-cadherin mRNA expression. In addition, ALK3^QD signalling reduced β1- and β3-integrin expression, critical molecules involved in ovarian cancer cell adhesion. The combination of reduced E-cadherin and β-integrin expression correlates directly with the reduced EOC cell cohesion in spheroids and reduced cell adhesion to the extracellular matrix substrates fibronectin and vitronectin that was observed.

Conclusions

We propose that the key steps of ovarian cancer metastasis, specifically cell cohesion of multicellular aggregates in ascites and cell adhesion for reattachment to secondary sites, may be inhibited by overactive BMP signalling, thereby decreasing the ultimate malignant potential of ovarian cancer in this model system.

Multiple signaling pathways converge to regulate bone-morphogenetic-protein-dependent glial gene expression

A fundamental problem in developmental neuroscience is understanding how extracellular cues link to complex intracellular signaling pathways to drive stage-specific developmental decisions. During the formation of the mammalian peripheral nervous system, bone morphogenetic proteins (BMPs) promote neuronal differentiation. BMPs also maintain the expression of early glial genes such as GFAP, while blocking the acquisition of a mature, myelinating Schwann cell phenotype. We investigated the BMP-activated signaling pathways that contribute to early glial gene expression to address the question of how specific signaling interactions contribute to cell fate decisions in neural crest lineages. Using a neural-crest-derived cell line that exhibits the characteristics of immature Schwann cells, we found that BMP2 promotes GFAP expression using Smad signaling as well as the phosphoinositide-3 kinase (PI3K) and mitogen-activated protein kinase1/2extracellular signal-regulated kinase- (MEK1/2/ERK) pathways. The GFAP promoter does not contain known Smad consensus sites, suggesting that Smads may act indirectly to promote GFAP expression. We provide evidence that this indirect effect may be mediated via induction of immediate early genes and the transcription factor Sp1 by demonstrating that these transcriptional regulators are induced by BMP2 and contribute to GFAP promoter activity. These findings demonstrate new roles for intracellular kinase pathways in mediating the effects of BMPs during the early stages of glial differentiation and suggest that differential contributions by signaling and transcriptional networks may contribute to the range of effects of BMPs on neuronal and glial development during the formation of the peripheral nervous system.

Promoter methylation of the bone morphogenetic protein-6 gene in association with adult T-cell leukemia

Bone morphogenetic proteins (BMP), belonging to the transforming growth factor-beta superfamily, are multifunctional regulators of cell proliferation, differentiation and apoptosis in various types of malignant cells. In this study, we investigated BMP-6 promoter methylation in patients with various types of leukemias. The BMP-6 methylation was found preferentially in adult T-cell leukemia (ATL) (49 of 60, 82%) compared with other types of leukemias studied including acute myeloid leukemia (3 of 67, 5%), acute lymphoblastic leukemia (6 of 38, 16%) and chronic lymphocytic leukemia (1 of 21, 5%). Among subtypes of ATL, the BMP-6 gene was more frequently methylated in aggressive ATL forms of acute (96%) and lymphoma (94%) types than less malignant chronic ATL (44%) and smoldering ATL (20%). We also analyzed the methylation status of peripheral blood mononuclear cells from healthy donors and nonmalignant lymph nodes with reactive lymphadenopathy, none of which showed detectable BMP-6 methylation in this study. The BMP-6 methyaltion was correlated with decreased mRNA transcript and protein expression. Expression of BMP-6 was restored by the demethylating agent 5-aza-2'-deoxycytidine, suggesting that methylation was associated with the transcriptional silencing. Serial analysis demonstrated an increasing methylation of CpG sites in the BMP-6 promoter and the resultant suppression of BMP-6 expression as ATL progressed. These findings suggested that BMP-6 promoter methylation is likely to be a common epigenetic event at later stages of ATL and that the methylation profiles may be useful for the staging of ATL as well as for evaluation of the individual risk of developing the disease.

Mouse models of psoriasis

Psoriasis is a T-cell-mediated chronic inflammatory skin disease believed to be of autoimmune nature that can be triggered or worsened by streptococcal throat infections. In addition to conventional chronic inflammatory changes, psoriasis is characterized by complex and striking alterations in epidermal growth and differentiation. Psoriasis is generally not observed in animals other than man, and this lack of a suitable animal model has greatly hindered research into the pathogenesis of psoriasis. Multiple transgenic, knockout, and reconstituted models of psoriasis have been developed over the past two decades. Despite their limitations, these models have demonstrated that keratinocyte hyperplasia, vascular hyperplasia, and cell-mediated immunity in the skin are closely interrelated. Xenograft models, in which involved and uninvolved psoriatic skin are transplanted onto immunodeficient mice, are the only models that come close to incorporating the complete genetic, immunologic, and phenotypic changes of the disease. They have shown conclusively that psoriasis is a T-cell-mediated disease, and have been used to elucidate novel pathogenic pathways. In this review, we describe various animal models, detail the immunologic and intracellular pathways that mediate these phenotypes and assess the utility of these models to better understand this disease.

BMP4 induces EMT and Rho GTPase activation in human ovarian cancer cells

We identified previously an autocrine bone morphogenetic protein-4 (BMP4) signalling pathway in primary human normal ovarian surface epithelial (OSE) and epithelial ovarian cancer (OvCa) cells. Herein we show that treatment of OvCa cells with BMP4 produced morphological alterations and increased cellular adhesion, motility and invasion. The BMP4 inhibitor noggin blocked the BMP4-induced phenotype, and decreased autocrine BMP4-mediated OvCa cell motility and adherence. In response to exogenous BMP4, the epithelial-mesenchymal transition (EMT) markers Snail and Slug mRNA and protein were up-regulated, E-cadherin mRNA and protein were down-regulated and the network of alpha smooth muscle actin changed to resemble a mesenchymal cell. We also observed changes in the level of activated Rho GTPases in OvCa cells treated with BMP4, strongly suggesting that the changes in morphology, adhesion, motility and invasion are probably mediated through the activation of these molecules. Strikingly, treatment of normal OSE cells with BMP4 or noggin failed to alter cell motility, providing evidence that OSE and OvCa cells possess a distinct capability to respond to BMP4. Overall, our studies suggest a link between autocrine BMP signalling mediated through the Rho GTPase family and Snail- and Slug-induced EMT that may collectively contribute to aggressive OvCa behaviour.

Safety and efficacy of use of demineralised bone matrix in orthopaedic and trauma surgery

Demineralised bone matrix (DBM) acts as an osteoconductive, and possibly as an osteoinductive, material. It is widely used in orthopaedic, neurosurgical, plastic and dental areas. More than 500,000 bone grafting procedures with DBM are performed annually in the US. It does not offer structural support, but it is well suited for filling bone defects and cavities. The osteoinductive nature of DBM is presumably attributed to the presence of matrix-associated bone morphogenetic proteins (BMPs) and growth factors, which are made available to the host environment by the demineralisation process. Clinical results have not been uniformly favourable; however, a variable clinical response is attributed partly to nonuniform processing methods found among numerous bone banks and commercial suppliers. DBMs remain reasonably safe and effective products. The ultimate safe bone-graft substitute, one that is osteoconductive, osteoinductive, osteogenic and mechanically strong, remains elusive.

Chordin is underexpressed in ovarian tumors and reduces tumor cell motility

Ovarian cancers mostly derive from the monolayer epithelium that covers the ovary. There are currently very few molecular clues to the etiology of this cancer. Bone morphogenetic proteins (BMPs) are required for follicular development and female fertility and are expressed in the ovarian surface epithelium (OSE). We previously reported the expression of human chordin (CHRD), a BMP extracellular regulator, in the ovary. Here we show that CHRD is underexpressed in epithelium ovary cancer and epithelial cancer cell lines as compared with normal tissues and OSE, respectively. Besides, we detected BMP expression in all ovarian cell lines analyzed. To determine the functional relevance of the absence of CHRD mRNA in tumors and cancer cell lines, we studied the effects of CHRD on two cancer cell lines, BG1 and PEO14. Migratory and invasive properties were greatly reduced, whereas cell adhesion to the support was enhanced. In addition, we detected chordin (Chrd) expression in OSE of rat ovaries in a pattern similar to that of BMP4. Altogether, these results suggest that CHRD could participate in regulating BMP activity in normal OSE physiology, and that its mis-expression in OSE may facilitate cancer incidence and/or progression.

Execution of BMP-4-induced apoptosis by p53-dependent ER dysfunction in myeloma and B-cell hybridoma cells

Bone morphogenic protein (BMP)-4 inhibits proliferation and induces the apoptosis of myeloma cells. However, little is known about the molecular mechanisms of how BMP-4 executes this apoptosis. In this report, we investigated the roles of p53 and the endoplasmic reticulum (ER) in BMP-4-induced apoptosis of mouse hybridoma HS-72 cells. We found that 3 ng/ml of BMP-4 is sufficient to induce the expression of proapoptotic proteins, puma and bax, in a p53-dependent mechanism, and facilitate Ca(2+) release from the ER to the cytosol, resulting in the activation of caspase-12 and ER dysfunction. Similarly to HS-72 cells, multiple myeloma cells with wild-type p53 genes show much higher sensitivity to BMP-4-induced apoptosis than cells without wild-type p53 genes, suggesting that wild-type p53 status is required for dysfunction of the ER during BMP-4-induced apoptosis in ER-enriched cells, such as hybridoma and myeloma cells. These findings demonstrate that the presence of wild-type p53 genes and enrichment of the ER determines the sensitivity to effective apoptosis by BMP-4, and suggest that ER stress-inducing agents would be valuable in the treatment of multiple myeloma.

Establishment and Characterization of a Cell Line, MCO-Y4, Derived from Canine Mammary Gland Osteosarcoma

A cell line, MCO-Y4, was established from a mammary gland osteosarcoma of a 16-year-old female mongrel dog. Histopathologically the tumor was composed of osteoblastic cells with an osteoid meshwork and chondroid matrix. The mean doubling time of the cells at the 93rd passage was 32.39+/-4.66 hr. Immunohistochemically, the osteoblastic and chondroblastic cells were positive for bone morphogenetic protein (BMP)-2/4 and BMP receptor (BMPR) II. The cultured cells were spindle in shape during the growth and the confluent phases. No tumor matrix was detected in the culture dish by alcian blue staining or von-Kossa silver impregnation. MCO-Y4 cells on the chamber slides showed intense immunoreactivity for BMP-2/4 and BMPR II. Noggin, an antagonist for BMP-2/4, showed the growth inhibition on MCO-Y4 cells. In addition, fibronectin might be potential for stimulating growth of MCO-Y4 cells. When transplanted into severe combined immunodeficiency mice, the cells formed tumors consisting of solid proliferation of osteoblastic and fibroblastic cells with woven-bone trabeculae. These tumor cells were intensely positive for BMP-2/4 and BMPR II. Our results suggested that the cell line might be useful for studying the role of BMPs in canine osteosarcoma and the mechanism of ossification.

Targeted disruption of Smad4 in mouse epidermis results in failure of hair follicle cycling and formation of skin tumors

Smad4 is the common mediator of transforming growth factor-beta (TGF-beta) superfamily signaling, which functions in diverse developmental processes in mammals. To study the role of Smad4 in skin development, a keratinocyte-specific null mutant of Smad4 (Smad4(co/co);K5-Cre) was generated in mice using the Cre-loxP system. The Smad4-mutant mice exhibited progressive alopecia as a result of the mutant hair follicles failing to undergo programmed regression. Sonic hedgehog (Shh) was only detected in Smad4-mutant hair follicles at the catagen stage. Seventy percent of Smad4(co/co); K5-Cre mice developed spontaneous tumors within 12 months of birth. c-Myc and cyclin D1 were up-regulated whereas p21 and p27 expressions were decreased, which correlated with the epidermal hyperplasia in Smad4 mutants. Interestingly, coordinated deletion of the Smad4 and PTEN genes resulted in accelerated hair loss and skin tumor formation, suggesting that Smad4 and PTEN act synergistically to regulate epidermal proliferation and differentiation. All of our data indicate that Smad4 is essential for catagen induction and acts as a critical suppressor in skin tumorigenesis.

Interaction between the bone morphogenetic proteins and Ras/MAP-kinase signalling pathways in lung cancer

Bone morphogenetic proteins (BMPs) are an integral component of the TGFβ superfamily, responsible for regulation of cell proliferation, differentiation, migration and programmed cell death in a variety of cell types. The BMPs transduce their signals directly through the SMAD family of proteins but they also have been reported to interact with the MAPK and Erk pathways. Inactivation of the BMP pathway genes has been implicated as important in several cancers. Recent work has shown that BMP3b is epigenetically inactivated in cancer and suggests that BMP6 can be epigenetically inactivated. We investigated whether BMP6 is epigenetically inactivated in cell lines and whether BMP3b and BMP6 are epigenetically inactivated in non-small-cell lung cancer (NSCLC). We also studied the relationship between BMP methylation and k-ras mutation. Here, we demonstrate that the BMP3b and BMP6 genes are common targets of epigenetic inactivation in NSCLC, and that they are significantly more likely to be concurrently inactivated (P=0.009). Furthermore, this coinactivation of BMP3b and BMP6 is significantly associated with mutation of k-ras codon 12 in lung cancer (P=0.003); those with a k-ras mutation were six times more likely to have concurrent methylation of these BMP loci. Hence, these data suggest that concurrent inactivation of the BMP and activation of the Ras signalling pathways are important in lung carcinogenesis.

Bone morphogenetic proteins in melanoma: Angel or devil?

Bone morphogenetic proteins (BMPs) are members of the transforming growth factor-beta (TGF-beta) superfamily serving multiple functions in many cell and tissue types including proliferation, apoptosis, differentiation, chemotaxis, angiogenesis, and matrix production during embryogenic development as well as in adult life. Despite the tremendous progress in delineating functional derangements of BMP pathways in carcinogenesis during the last decade, the biological significance of BMPs in human melanoma has received very little attention. It is now clear that biological responses to BMPs are cell type-specific and divergent effects, i.e., both oncogenic and tumor suppressor activities, have been described. Thus, knowledge generated in one system may not translate directly to another. In this review, we summarize the current understanding of BMP signaling in various human cancers and discuss original data pertaining to cutaneous melanoma obtained in our laboratory.

BMP-6 inhibits growth of mature human B cells; induction of Smad phosphorylation and upregulation of Id1

Background

Bone morphogenetic proteins (BMPs) belong to the TGF-β superfamily and are secreted proteins with pleiotropic roles in many different cell types. A potential role of BMP-6 in the immune system has been implied by various studies of malignant and rheumatoid diseases. In the present study, we explored the role of BMP-6 in normal human peripheral blood B cells.

Results

The B cells were found to express BMP type I and type II receptors and BMP-6 rapidly induced phosphorylation of Smad1/5/8. Furthermore, Smad-phosphorylation was followed by upregulation of Id1 mRNA and Id1 protein, whereas Id2 and Id3 expression was not affected. Furthermore, we found that BMP-6 had an antiproliferative effect both in naïve (CD19⁺CD27^-) and memory B cells (CD19⁺CD27⁺) stimulated with anti-IgM alone or the combined action of anti-IgM and CD40L. Additionally, BMP-6 induced cell death in activated memory B cells. Importantly, the antiproliferative effect of BMP-6 in B-cells was completely neutralized by the natural antagonist, noggin. Furthermore, B cells were demonstrated to upregulate BMP-6 mRNA upon stimulation with anti-IgM.

Conclusion

In mature human B cells, BMP-6 inhibited cell growth, and rapidly induced phosphorylation of Smad1/5/8 followed by an upregulation of Id1.

Application of bone morphogenetic proteins in orthopaedic practice: their efficacy and side effects

Bone morphogenetic proteins (BMPs) have been extensively studied since the discovery of agents within bone that could induce bone formation at ectopic sites by Urist in the 1960s. Extensive preclinical research has been carried out showing the efficacy of these products in promoting bone healing. Clinical trials are encouraging, with meta-analysis of results revealing better rates of healing than treatment with autologous bone grafting (risk ratio [RR]: 0.845; 95% confidence interval [CI]: 0.772 - 0.924; p < 0.001 for clinical outcome and RR: 0.884; 95% CI: 0.825 - 0.948; p < 0.001 for radiological outcome). Preclinical and clinical safety assessments have revealed little evidence of toxic effects and there have been few reports of adverse events related to their use. A small rate of immunological reaction following administration, resulting in antibody formation, has been observed in some patients, without clinical consequence, although the long-term implications of this are unknown. Ongoing research is revealing that BMPs act on an extremely wide range of body tissues in a variety of manners and this is far from fully understood. It should be noted, however, that given the role of BMP as a differentiation factor, the production of undifferentiated neoplastic tissue seems unlikely. It has also been shown in an animal model that artificially administered BMP can cross the placenta and subsequently be detected in the growing embryo. As this area has been little investigated, use in pregnancy is currently contraindicated. Until the long-term safety profile is more fully documented it would seem sensible to continue to carefully control use and monitor patients closely. However, the current evidence is very promising.

Loss of keratin 10 leads to mitogen-activated protein kinase (MAPK) activation, increased keratinocyte turnover, and decreased tumor formation in mice

Keratin 10 (K10) is the major protein in the upper epidermis where it maintains keratinocyte integrity. Others have reported that K10 may act as a tumor suppressor upon ectopic expression in mice. Although K10(-/-) mice show significant epidermal hyperproliferation, accompanied by an activation of the mitogen-activated protein kinase (MAPK) pathway, they formed no spontaneous tumors. Here, we report that K10(-/-) mice treated with 7,12-dimethylbenz[a]anthracene (DMBA)/12-O-tetradecanoylphorbol-13-acetate (TPA) developed far less papillomas than wild-type mice. BrdU(5-bromo-2'-deoxyuridine)-labeling revealed a strongly accelerated keratinocyte turnover in K10(-/-) epidermis suggesting an increased elimination of initiated keratinocytes at early stages of developing tumors. This is further supported by the absence of label-retaining cells 18 d after the pulse whereas in wild-type mice label-retaining cells were still present. The concomitant increase in K6, K16, and K17 in K10 null epidermis and the increased motility of keratinocytes is in agreement with the pliability versus resilience hypothesis, stating that K10 and K1 render cells more stable and static. The K10(-/-) knockout represent the first mouse model showing that loss of a keratin, a cytoskeletal protein, reduces tumor formation. This is probably caused by an accelerated turnover of keratinocytes, possibly mediated by activation of MAPK pathways.

Smad3 Knockout Mice Exhibit a Resistance to Skin Chemical Carcinogenesis

It has been shown that Smad3 exerts both tumor-suppressive and -promoting roles. To evaluate the role of Smad3 in skin carcinogenesis in vivo, we applied a chemical skin carcinogenesis protocol to Smad3 knockout mice (Smad3(-/-) and Smad3(+/-)) and wild-type littermates (Smad3(+/+)). Smad3(-/-) mice exhibited reduced papilloma formation in comparison with Smad3(+/+) mice and did not develop any squamous cell carcinomas. Further analysis revealed that Smad3 knockout mice were resistant to 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced epidermal hyperproliferation. Concurrently, increased apoptosis was observed in TPA-treated Smad3(-/-) skin and papillomas when compared with those of wild-type mice. Expression levels of activator protein-1 family members (c-jun, junB, junD, and c-fos) and transforming growth factor (TGF)-alpha were significantly lower in TPA-treated Smad3(-/-) skin, cultured keratinocytes, and papillomas, as compared with Smad3(+/+) controls. Smad3(-/-) papillomas also exhibited reduced leukocyte infiltration, particularly a reduction of tumor-associated macrophage infiltration, in comparison with Smad3(+/+) papillomas. All of these molecular and cellular alterations also occurred to a lesser extent in Smad3(+/-) mice as compared with Smad3(+/+) mice, suggesting a Smad3 gene dosage effect. Given that TGF-beta1 is a well-documented TPA-responsive gene and also has a potent chemotactic effect on macrophages, our study suggests that Smad3 may be required for TPA-mediated tumor promotion through inducing TGF-beta1-responsive genes, which are required for tumor promotion, and through mediating TGF-beta1-induced macrophage infiltration.

Bone morphogenetic protein-5, -6 and -7 inhibit growth and induce apoptosis in human myeloma cells

Previously, bone morphogenetic protein (BMP)-2 and -4 have been shown to inhibit proliferation and induce apoptosis in human myeloma cells. BMP-2 and -4 belong to a subgroup of BMPs using the BMP receptors Alk-3 or -6. In this study, we examined the effects on human myeloma cells of BMP-6 and -7, members of a different BMP subgroup, which mainly utilize Alk-2 as their receptor. All cell lines examined expressed mRNA for the BMP-6 and -7 receptor Alk-2. We did not detect transcripts for the BMP-2 and -4 receptors Alk-3 or Alk-6 in INA-6 and RPMI-8226 cells by RT-PCR. Accordingly, the intracellular signalling molecules Smad-1, -5 and -8 were not phosphorylated by BMP-4 in INA-6 and RPMI-8226 cells. The expression patterns of various BMP receptors in the myeloma cell lines explained the differences in responses to the various BMPs. Alk-2-expressing cell lines responded with growth inhibition and apoptosis to BMP-6 and -7, whereas cell lines lacking both Alk-3 and -6 were resistant to BMP-4. Soluble Alk-3 and -6 were able to neutralize the BMP-4 effects in BMP-4-responsive cell lines. All BMPs reduced viability in more than 70% of purified primary myeloma cell samples. BMPs have intriguing antitumor effects in vitro. Importantly, myeloma cells not responsive to BMP-2 and -4 may still be sensitive to BMP-6 or -7. It is possible that therapeutic use of BMP or BMP analogues could have an impact on both myeloma bone disease and myeloma cell growth.

Type II Collagen Accumulation in Overlying Dermo-Epidermal Junction of Pilomatricoma Is Mediated by Bone Morphogenetic Protein 2 and 4

Pilomatricoma consists of the cells differentiating towards hair matrix cells. Immunohistochemical study revealed the deposition of type II collagen in the overlying dermo-epidermal junction (DEJ) of this benign tumor. Proalpha(1)(II) mRNA was detected by RT-PCR in the overlying epidermal layer but not in the dermal layer prepared from the lesional skin of pilomatricoma. The neutral salt-soluble proteins extracted from the tumor of pilomatricoma induced proalpha(1)(II) mRNA in the cultured human keratinocytes but not in the cultured dermal fibroblasts. Bone morphogenetic protein 2 or 4 (BMP2 or 4) was immunohistochemically detected in some shadow cells of pilomatricoma. Recombinant BMP2 and BMP4 were found to induce proalpha(1)(II) mRNA concentration dependently in the cultured human keratinocytes but not in the cultured fibroblasts. Proalpha(1)(II) mRNA induced by BMP2 and in cultured keratinocytes contained exon 2, indicating that the mRNA species is non-chondrogenic type IIA form. The results strongly suggest that BMP2 or 4 expressed in pilomatricoma is responsible for the induction of proalpha(1)(II) collagen mRNA in the overlying epidermal cells resulting in the deposition of type II collagen in the DEJ. When human keratinocytes were cultured on type II collagen substratum in vitro, the cell proliferation was accelerated at the early period of culture but was inhibited at the late period of culture, whereas the cell proliferation was persistently accelerated by type I or IV collagen substratum. Type II collagen deposition in the DEJ may potentially exert profound effects on keratinocyte proliferation and differentiation.

BMP4 signaling induces senescence and modulates the oncogenic phenotype of A549 lung adenocarcinoma cells

Lung cancer is the most common visceral malignancy in males, with rapidly increasing incidence in females, and a devastatingly poor prognosis. Transforming growth factor (TGF)-beta has been shown to induce senescence in A549 lung cancer cells, and both TGF-beta and bone morphogenetic protein (BMP) 2 can suppress the transformed phenotype of A549 cells in vitro. We examined the effects of BMP4, another member of the TGF-beta superfamily, on specific oncogenic properties of A549 cancer cells. When A549 cancer cells were treated continuously with 100 ng/ml of BMP4, a senescent phenotype was observed after 2 wk of treatment. The BMP-treated cells appeared larger than untreated cells, grew more slowly, had more senescence-associated beta-galactosidase activity, and had less telomerase activity, as measured by the telomeric repeat amplification protocol assay. Invasion through Engelbreth Holm-Swarm matrix was inhibited in the senescent cell population. Senescent BMP4-treated cells had lower ERK activation, VEGF expression, and Bcl2 expression than wild-type cells, consistent with a less proliferative, less angiogenic phenotype with increased susceptibility to death by apoptosis. BMP4 treatment also resulted in sustained elevation of Smad1. In vivo xenograft studies in the flanks of nude mice confirmed that the BMP-treated cells were significantly less tumorigenic than untreated cells. Direct overexpression of Smad1 using adenoviral constructs resulted in cell death within 5 days. These studies suggest that BMP4 pathway signaling can induce senescence and thus negatively regulate the growth of A549 lung cancer cells.

Bone morphogenetic protein 2 is expressed by, and acts upon, mature epithelial cells in the colon

BACKGROUND AND AIMS

The recent findings of bone morphogenetic protein (BMP) receptor Ia mutations in juvenile polyposis and frequent Smad4 mutations in colon cancer suggest a role for BMPs in the colonic epithelium and colon cancer. We investigated the role of BMP2 in the colon.

METHODS

We assessed BMP receptor expression in cell lines using the reverse-transcribed polymerase chain reaction and immunoblotting. We investigated the effect of BMP2 on cell lines using the MTT assay and by immunoblotting for markers of differentiation, proliferation, and apoptosis. We assessed the expression of BMP2, its receptors, and signal transduction elements in mouse and human colon tissue using immunohistochemistry. We also investigated the effect of the BMP antagonist noggin in vivo in mice by assessing colon tissue with immunohistochemistry and immunoblotting. Finally, we investigated the expression of BMP2 in microadenomas from familial adenomatous polyposis patients.

RESULTS

BMP receptors (BMPR) Ia, BMPR Ib, and BMPR II are all expressed in colonic epithelial cell lines. BMP2 inhibits colonic epithelial cell growth in vitro, promoting apoptosis and differentiation and inhibiting proliferation. BMP2, BMPRIa, BMPRIb, BMPRII, phosphorylated Smad1, and Smad4 are expressed predominantly in mature colonocytes at the epithelial surface in normal adult human and mouse colon. Noggin inhibits apoptosis and proliferation in mouse colonic epithelium in vivo. BMP2 expression is lost in the microadenomas of familial adenomatous polyposis patients.

CONCLUSIONS

These data suggest that BMP2 acts as a tumor suppressor promoting apoptosis in mature colonic epithelial cells.

Essential roles of BMPR-IA signaling in differentiation and growth of hair follicles and in skin tumorigenesis

Hair differentiation and growth are controlled by complex reciprocal signaling between epithelial and mesenchymal cells. To better understand the requirement and molecular mechanism of BMP signaling in hair follicle development, we performed genetic analyses of bone morphogenetic protein receptor 1A (BMPR-IA) function during hair follicle development by using a conditional knockout approach. The conditional mutation of Bmpr1a in ventral limb ectoderm and its derivatives (epidermis and hair follicles) resulted in a lack of hair outgrowth from the affected skin regions. Mutant hair follicles exhibited abnormal morphology and lacked hair formation and pigment deposition during anagen. The timing of the hair cycle and the proliferation of hair matrix cells were also affected in the mutant follicles. We demonstrate that signaling via epithelial BMPR-IA is required for differentiation of both hair shaft and inner root sheath from hair matrix precursor cells in anagen hair follicles but is dispensable for embryonic hair follicle induction. Surprisingly, aberrant de novo hair follicle morphogenesis together with hair matrix cell hyperplasia was observed in the absence of BMPR-IA signaling within the affected skin of adult mutants. They developed hair follicle tumors from 3 months of age, indicating that inactivation of epidermal BMPR-IA signaling can lead to hair tumor formation. Taken together, our data provide genetic evidence that BMPR-IA signaling plays critical and multiple roles in controlling cell fate decisions or maintenance, proliferation, and differentiation during hair morphogenesis and growth, and implicate Bmpr1a as a tumor suppressor in skin tumorigenesis.

Identification of a putative autocrine bone morphogenetic protein-signaling pathway in human ovarian surface epithelium and ovarian cancer cells

Bone morphogenetic proteins (BMPs) are members of the TGFbeta superfamily of cytokines that are involved in development, differentiation, and disease. In an analysis of normal ovarian surface epithelium (OSE) and ovarian cancer (OC) cells, we observed BMP4 mRNA expression and found that primary OC cells produce mature BMP4. In addition, each member of the downstream signaling pathway was expressed in primary OSE and OC cells. Smad1 was phosphorylated and underwent nuclear translocation in normal OSE and OC cells upon treatment with BMP4. Interestingly, the BMP target genes ID1 and ID3 were up-regulated 10- to 15-fold in primary OC cells, compared with a 2- to 3-fold increase in normal OSE. The growth of several primary OC cells was relatively unaltered by BMP4 treatment; however, long-term BMP4 treatment of primary OC cells resulted in decreased cell density as well as increased cell spreading and adherence. These data demonstrate the existence and putative function of BMP signaling in normal OSE and OC cells, and thus the continued examination of BMP4 signaling in the regulation of these two processes will be critical to further our current understanding of the role of BMP biology in OC pathogenesis.

Bone morphogenetic proteins and their antagonists in skin and hair follicle biology

Bone morphogenetic proteins (BMP) are members of the transforming growth factor-beta superfamily regulating a large variety of biologic responses in many different cells and tissues during embryonic development and postnatal life. BMP exert their biologic effects via binding to two types of serine/threonine kinase BMP receptors, activation of which leads to phosphorylation and translocation into the nucleus of intracellular signaling molecules, including Smad1, Smad5, and Smad8 ("canonical" BMP signaling pathway). BMP effects are also mediated by activation of the mitogen-activated protein (MAP) kinase pathway ("noncanonical" BMP Signaling pathway). BMP activity is regulated by diffusible BMP antagonists that prevent BMP interactions with BMP receptors thus modulating BMP effects in tissues. During skin development, BMPs its receptors and antagonists show stringent spatiotemporal expressions patterns to achieve proper regulation of cell proliferation and differentiation in the epidermis and in the hair follicle. In normal postnatal skin, BMP are involved in the control of epidermal homeostasis, hair follicle growth, and melanogenesis. Furthermore, BMP are implicated in a variety of pathobiologic processes in skin, including wound healing, psoriasis, and carcinogenesis. Therefore, BMPs represent new important players in the molecular network regulating homeostasis in normal and diseased skin. Pharmacologic modulation of BMP signaling may be used as a new approach for managing skin and hair disorders.